Multifunctional surface modification of silk fabric via graphene oxide repeatedly coating and chemical reduction method

NASA Astrophysics Data System (ADS)

Cao, Jiliang; Wang, Chaoxia

2017-05-01

Multifunctional silk fabrics with electrical conductive, anti-ultraviolet and water repellent were successfully prepared by surface modification with graphene oxide (GO). The yellow-brown GO deposited on the surface of silk fabric was converted into graphitic black reduced graphene (RGO) by sodium hydrosulfite. The surface properties of silk fabrics were changed by repeatedly RGO coating process, which have been proved by SEM and XPS. The SEM results showed that the RGO sheets were successive form a continuously thin film on the surface of silk fabrics, and the deposition of GO or RGO also can be proved by XPS. The electrical conductivity was tested by electrical surface resistance value of the silk fabric, the surface resistance decreased with increasing of RGO surface modification times, and a low surface resistance value reached to 3.24 KΩ cm-1 after 9 times of modification, indicating the silk obtained excellent conductivity. The UPF value of one time GO modification silk fabric (silk-1RGO) was enhanced significantly to 24.45 in comparison to 10.40 of original silk. The contact angle of RGO coating silk samples was all above of 120°. The durability of RGO coated silk fabrics was tested by laundering. The electrical surface resistance of silk-4RGO (65.74 KΩ cm-1), silk-6RGO (15.54 KΩ cm-1) and silk-8RGO (3.86 KΩ cm-1) fabrics was up to 86.82, 22.30 and 6.57 KΩ cm-1 after 10 times of standard washing, respectively. The UPF value, contact angle and color differences of RGO modified silk fabric slightly changed before and after 10 times of standard washing. Therefore, the washing fastness of electric conduction, anti-ultraviolet and water repellent multifunctional silk fabrics was excellent.

The development of a novel wound healing material, silk-elastin sponge.

PubMed

Kawabata, Shingo; Kawai, Katsuya; Somamoto, Satoshi; Noda, Kazuo; Matsuura, Yoshitaka; Nakamura, Yoko; Suzuki, Shigehiko

2017-12-01

Silk-elastin is a recombinant protein polymer with repeating units of silk and elastin blocks. This novel wound healing promoting material has the ability to self-assemble from a liquid to a gel. We have already reported that an aqueous solution of silk-elastin has the potential to accelerate wound healing; however, there are several problems in applying silk-elastin in the clinical setting. To solve these problems, we developed a silk-elastin sponge that is easy to use in the clinical setting. In the present study, we examined whether the wound healing effect of the silk-elastin sponge is equal to the aqueous solution of silk-elastin in vivo. The granulation tissue formation promoting effect of the silk-elastin sponge was equal to that of the aqueous solution the silk-elastin, as after application to the wound surface, the sponge was absorbed and dissolved by the exudate. At body temperature the silk-elastin then formed temperature gel. The silk-elastin gel that was obtained contained abundant cytokines from the exudate. We believe that silk-elastin sponge can be applied to various wounds that are difficult to treat with the aqueous solution.

Regulation of Silk Genes by Hox and Homeodomain Proteins in the Terminal Differentiated Silk Gland of the Silkworm Bombyx mori

PubMed Central

Takiya, Shigeharu; Tsubota, Takuya; Kimoto, Mai

2016-01-01

The silk gland of the silkworm Bombyx mori is a long tubular organ that is divided into several subparts along its anteroposterior (AP) axis. As a trait of terminal differentiation of the silk gland, several silk protein genes are expressed with unique regional specificities. Most of the Hox and some of the homeobox genes are also expressed in the differentiated silk gland with regional specificities. The expression patterns of Hox genes in the silk gland roughly correspond to those in embryogenesis showing “colinearity”. The central Hox class protein Antennapedia (Antp) directly regulates the expression of several middle silk gland–specific silk genes, whereas the Lin-1/Isl-1/Mec3 (LIM)-homeodomain transcriptional factor Arrowhead (Awh) regulates the expression of posterior silk gland–specific genes for silk fiber proteins. We summarize our results and discuss the usefulness of the silk gland of Bombyx mori for analyzing the function of Hox genes. Further analyses of the regulatory mechanisms underlying the region-specific expression of silk genes will provide novel insights into the molecular bases for target-gene selection and regulation by Hox and homeodomain proteins. PMID:29615585

Preparation and mechanical properties of layers made of recombinant spider silk proteins and silk from silk worm

NASA Astrophysics Data System (ADS)

Junghans, F.; Morawietz, M.; Conrad, U.; Scheibel, T.; Heilmann, A.; Spohn, U.

2006-02-01

Layers of recombinant spider silks and native silks from silk worms were prepared by spin-coating and casting of various solutions. FT-IR spectra were recorded to investigate the influence of the different mechanical stress occurring during the preparation of the silk layers. The solubility of the recombinant spider silk proteins SO1-ELP, C16, AQ24NR3, and of the silk fibroin from Bombyx mori were investigated in hexafluorisopropanol, ionic liquids and concentrated salt solutions. The morphology and thickness of the layers were determined by Atomic Force Microscopy (AFM) or with a profilometer. The mechanical behaviour was investigated by acoustic impedance analysis by using a quartz crystal microbalance (QCMB) as well as by microindentation. The density of silk layers (d<300 nm) was determined based on AFM and QCMB measurements. At silk layers thicker than 300 nm significant changes of the half-band-half width can be correlated with increasing energy dissipation. Microhardness measurements demonstrate that recombinant spider silk and sericine-free Bombyx mori silk layers achieve higher elastic penetration modules EEP and Martens hardness values HM than those of polyethylenterephthalate (PET) and polyetherimide (PEI) foils.

Phosphoproteomic analysis of the posterior silk gland of Bombyx mori provides novel insight into phosphorylation regulating the silk production.

PubMed

Song, Jia; Che, Jiaqian; You, Zhengying; Ye, Lupeng; Li, Jisheng; Zhang, Yuyu; Qian, Qiujie; Zhong, Boxiong

2016-10-04

To understand phosphorylation event regulating silk synthesis in the posterior silk gland of Bombyx mori, phosphoproteome was profiled in a pair of near-isogenic lines, a normally cocooning strain (IC) and a nakedly pupated strain (IN) that the silk production is much lower than IC. In the posterior silk gland of the IC and IN, 714 and 658 phosphosites resided on 554 and 507 phosphopeptides from 431 and 383 phosphoproteins, were identified, respectively. Of all the phosphosites, the single phosphosite was the dominate phosphorylation form, comprising>60% of all the phosphosites in two phenotypic of silk production. All these phosphosites were classified as acidophilic and proline-directed kinase classes, and three motifs were uniquely identified in the IC. The motif S-P-P might be important for regulating phosphorylation network of silk protein synthesis. The dynamically phosphorylated proteins participated in ribosome, protein transport and energy metabolism suggest that phosphorylation may play key roles in regulating silk protein synthesis and secretion. Furthermore, fibroin heavy chain, an important component of silk protein, was specifically phosphorylated in the IC strain, suggesting its role to ensure the normal formation of silk structure and silk secretion. The data gain new understanding of the regulatory processes of silk protein synthesis and offer as starting point for further research on the silk production at phosphoproteome level. Despite the knowledge on regulation of silk protein synthesis in the posterior silk gland has gained at the gene or protein levels, how phosphorylation event influences the silk yield is largely unknown. To this end, we constructed a pair of silkworm near-isogenic lines that showed different cocooning phenotypes, and the phosphoproteome of the posterior silk gland of two isolines was compared. Here, we reported the first phosphoproteome data on the silkworm and found several key pathways related protein synthesis are regulated by phosphorylation, thereby influencing the silk production. The data provide valuable resources for further functional assay of targeted protein phosphorylation that regulates the silk synthesis in silkworm. Copyright © 2016 Elsevier B.V. All rights reserved.

Optically probing torsional superelasticity in spider silks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Bhupesh; Thakur, Ashish; Panda, Biswajit

2013-11-11

We investigate torsion mechanics of various spider silks using a sensitive optical technique. We find that spider silks are torsionally superelastic in that they can reversibly withstand great torsion strains of over 10{sup 2−3} rotations per cm before failure. Among various silks from a spider, we find the failure twist-strain is greatest in the sticky capture silk followed by dragline and egg-case silk. Our in situ laser-diffraction measurements reveal that torsional strains on the silks induce a nano-scale transverse compression in its diameter that is linear and reversible. These unique torsional properties of the silks could find applications in silk-basedmore » materials and devices.« less

Microdissection of Black Widow Spider Silk-producing Glands

PubMed Central

Hsia, Yang; Gnesa, Eric; Zhao, Liang; Franz, Andreas; Vierra, Craig

2011-01-01

Modern spiders spin high-performance silk fibers with a broad range of biological functions, including locomotion, prey capture and protection of developing offspring 1,2. Spiders accomplish these tasks by spinning several distinct fiber types that have diverse mechanical properties. Such specialization of fiber types has occurred through the evolution of different silk-producing glands, which function as small biofactories. These biofactories manufacture and store large quantities of silk proteins for fiber production. Through a complex series of biochemical events, these silk proteins are converted from a liquid into a solid material upon extrusion. Mechanical studies have demonstrated that spider silks are stronger than high-tensile steel 3. Analyses to understand the relationship between the structure and function of spider silk threads have revealed that spider silk consists largely of proteins, or fibroins, that have block repeats within their protein sequences 4. Common molecular signatures that contribute to the incredible tensile strength and extensibility of spider silks are being unraveled through the analyses of translated silk cDNAs. Given the extraordinary material properties of spider silks, research labs across the globe are racing to understand and mimic the spinning process to produce synthetic silk fibers for commercial, military and industrial applications. One of the main challenges to spinning artificial spider silk in the research lab involves a complete understanding of the biochemical processes that occur during extrusion of the fibers from the silk-producing glands. Here we present a method for the isolation of the seven different silk-producing glands from the cobweaving black widow spider, which includes the major and minor ampullate glands [manufactures dragline and scaffolding silk] 5,6, tubuliform [synthesizes egg case silk] 7,8, flagelliform [unknown function in cob-weavers], aggregate [makes glue silk], aciniform [synthesizes prey wrapping and egg case threads] 9 and pyriform [produces attachment disc silk] 10. This approach is based upon anesthetizing the spider with carbon dioxide gas, subsequent separation of the cephalothorax from the abdomen, and microdissection of the abdomen to obtain the silk-producing glands. Following the separation of the different silk-producing glands, these tissues can be used to retrieve different macromolecules for distinct biochemical analyses, including quantitative real-time PCR, northern- and western blotting, mass spectrometry (MS or MS/MS) analyses to identify new silk protein sequences, search for proteins that participate in the silk assembly pathway, or use the intact tissue for cell culture or histological experiments. PMID:21248709

Silkworms transformed with chimeric silkworm/spider silk genes spin composite silk fibers with improved mechanical properties

USDA-ARS?s Scientific Manuscript database

The development of a spider silk manufacturing process is of great interest. piggyBac vectors were used to create transgenic silkworms encoding chimeric silkworm/spider silk proteins. The silk fibers produced by these animals were composite materials that included chimeric silkworm/spider silk prote...

Improved strength of silk fibers in Bombyx mori trimolters induced by an anti-juvenile hormone compound.

PubMed

Guo, Kaiyu; Dong, Zhaoming; Zhang, Yan; Wang, Dandan; Tang, Muya; Zhang, Xiaolu; Xia, Qingyou; Zhao, Ping

2018-05-01

Bombyx mori silk fibers with thin diameters have advantages of lightness and crease-resistance. Many studies have used anti-juvenile hormones to induce trimolters in order to generate thin silk; however, there has been comparatively little analysis of the morphology, structure and mechanical properties of trimolter silk. This study induced two kinds of trimolters by appling topically anti-juvenile hormones and obtained thin diameter silk. Scanning electron microscope (SEM), FTIR analysis, tensile mechanical testing, chitin staining were used to reveal that the morphology, conformation and mechanical property of the trimolter silk. Cocoon of trimolters were highly densely packed by thinner fibers and thus had small apertures. We found that the conformation of trimolter silk fibroin changed and formed more β-sheet structures. In addition, analysis of mechanical parameters yielded a higher Young's modulus and strength in trimolter silk than in the control. By chitin staining of silk gland, we postulated that the mechanical properties of trimolters' silk was enhanced greatly during to the structural changes of silk gland. We induced trimolters by anti-juvenile hormones and the resulting cocoons were more closely packed and had smaller silk fiber diameters. We found that the conformation of trimolters silk fibroin had a higher content of β-sheet structures and better mechanical properties. Our study revealed the structures and mechanical properties of trimolter silk, and provided a valuable reference to improve silk quality by influencing molting in silkworms. Copyright © 2018 Elsevier B.V. All rights reserved.

Synthetic Engineering of Spider Silk Fiber as Implantable Optical Waveguides for Low-Loss Light Guiding.

PubMed

Qiao, Xin; Qian, Zhigang; Li, Junjie; Sun, Hongji; Han, Yao; Xia, Xiaoxia; Zhou, Jin; Wang, Chunlan; Wang, Yan; Wang, Changyong

2017-05-03

A variety of devices used for biomedical engineering have been fabricated using protein polymer because of their excellent properties, such as strength, toughness, biocompatibility, and biodegradability. In this study, we fabricated an optical waveguide using genetically engineered spider silk protein. This method has two significant advantages: (1) recombinant spider silk optical waveguide exhibits excellent optical and biological properties and (2) biosynthesis of spider silk protein can overcome the limitation to the research on spider silk optical waveguide due to the low yield of natural spider silk. In detail, two kinds of protein-based optical waveguides made from recombinant spider silk protein and regenerative silkworm silk protein were successfully prepared. Results suggested that the recombinant spider silk optical waveguide showed a smoother surface and a higher refractive index when compared with regenerative silkworm silk protein. The optical loss of recombinant spider silk optical waveguide was 0.8 ± 0.1 dB/cm in air and 1.9 ± 0.3 dB/cm in mouse muscles, which were significantly lower than those of regenerative silkworm silk optical waveguide. Moreover, recombinant spider silk optical waveguide can meet the demand to guide and efficiently deliver light through biological tissue. In addition, recombinant spider silk optical waveguide showed low toxicity to cells in vitro and low-level inflammatory reaction with surrounding tissue in vivo. Therefore, recombinant spider silk optical waveguide is a promising implantable device to guide and deliver light with low loss.

Post-secretion processing influences spider silk performance

PubMed Central

Blamires, Sean J.; Wu, Chung-Lin; Blackledge, Todd A.; Tso, I-Min

2012-01-01

Phenotypic variation facilitates adaptations to novel environments. Silk is an example of a highly variable biomaterial. The two-spidroin (MaSp) model suggests that spider major ampullate (MA) silk is composed of two proteins—MaSp1 predominately contains alanine and glycine and forms strength enhancing β-sheet crystals, while MaSp2 contains proline and forms elastic spirals. Nonetheless, mechanical properties can vary in spider silks without congruent amino acid compositional changes. We predicted that post-secretion processing causes variation in the mechanical performance of wild MA silk independent of protein composition or spinning speed across 10 species of spider. We used supercontraction to remove post-secretion effects and compared the mechanics of silk in this ‘ground state’ with wild native silks. Native silk mechanics varied less among species compared with ‘ground state’ silks. Variability in the mechanics of ‘ground state’ silks was associated with proline composition. However, variability in native silks did not. We attribute interspecific similarities in the mechanical properties of native silks, regardless of amino acid compositions, to glandular processes altering molecular alignment of the proteins prior to extrusion. Such post-secretion processing may enable MA silk to maintain functionality across environments, facilitating its function as a component of an insect-catching web. PMID:22628213

Silk from crickets: a new twist on spinning.

PubMed

Walker, Andrew A; Weisman, Sarah; Church, Jeffrey S; Merritt, David J; Mudie, Stephen T; Sutherland, Tara D

2012-01-01

Raspy crickets (Orthoptera: Gryllacrididae) are unique among the orthopterans in producing silk, which is used to build shelters. This work studied the material composition and the fabrication of cricket silk for the first time. We examined silk-webs produced in captivity, which comprised cylindrical fibers and flat films. Spectra obtained from micro-Raman experiments indicated that the silk is composed of protein, primarily in a beta-sheet conformation, and that fibers and films are almost identical in terms of amino acid composition and secondary structure. The primary sequences of four silk proteins were identified through a mass spectrometry/cDNA library approach. The most abundant silk protein was large in size (300 and 220 kDa variants), rich in alanine, glycine and serine, and contained repetitive sequence motifs; these are features which are shared with several known beta-sheet forming silk proteins. Convergent evolution at the molecular level contrasts with development by crickets of a novel mechanism for silk fabrication. After secretion of cricket silk proteins by the labial glands they are fabricated into mature silk by the labium-hypopharynx, which is modified to allow the controlled formation of either fibers or films. Protein folding into beta-sheet structure during silk fabrication is not driven by shear forces, as is reported for other silks.

[Engineered spider silk: the intelligent biomaterial of the future. Part I].

PubMed

Florczak, Anna; Piekoś, Konrad; Kaźmierska, Katarzyna; Mackiewicz, Andrzej; Dams-Kozłowska, Hanna

2011-06-17

The unique properties of spider silk such as strength, extensibility, toughness, biocompatibility and biodegradability are the reasons for the recent development in silk biomaterial technology. For a long time scientific progress was impeded by limited access to spider silk. However, the development of the molecular biology strategy was a breaking point in synthetic spider silk protein design. The sequences of engineered spider silk are based on the consensus motives of the corresponding natural equivalents. Moreover, the engineered silk proteins may be modified in order to gain a new function. The strategy of the hybrid proteins constructed on the DNA level combines the sequence of engineered silk, which is responsible for the biomaterial structure, with the sequence of polypeptide which allows functionalization of the silk biomaterial. The functional domains may comprise receptor binding sites, enzymes, metal or sugar binding sites and others. Currently, advanced research is being conducted, which on the one hand focuses on establishing the particular silk structure and understanding the process of silk thread formation in nature. On the other hand, there are attempts to improve methods of engineered spider silk protein production. Due to acquired knowledge and recent progress in synthetic protein technology, the engineered silk will turn into intelligent biomaterial of the future, while its industrial production scale will trigger a biotechnological revolution.

Bombyx mori silk: From mechanical properties to functionalities

NASA Astrophysics Data System (ADS)

Koh, Leng Duei

Bombyx mori silkworms are the main producer of silk worldwide. It has been used as high-end textile fibers and as surgical sutures, and is being further developed for various emerging biomedical applications including drug delivery, tissue engineering, sensing, and imaging. The silk fibroin features a hierarchical architecture consisting of beta-sheet crystallites embedded in a less ordered amorphous matrix, which accounts for its unique combination of lustre appearance, soft-to-touch texture, and impressive mechanical properties. Notably, many applications of silk take advantage of its impressive mechanical properties, which by nature surpass many natural and synthetic materials. Interestingly, both the silkworm silk and spider dragline silk share similar hierarchical architecture but possess great disparity in mechanical properties. Inspired by spider dragline silk with much superior strength and toughness, there is an ever growing interest to enhance the mechanical properties of Bombyx mori silk. Here, we design a green and facile feeding method to modulate the structures of silk fibroin at the nanoscale using citric acid (CA), and achieved greatly enhanced mechanical properties. The silk obtained (i.e., CA silk) emerges to be the intrinsically toughest silkworm silk, with mechanical properties that exceed those of the previously reported natural and enhanced silkworm silk, and compare well with those of naturally produced spider silk (including those from spiders Araneus diadematus, Nephila clavipes, etc.).The underlying interactions of CA with fibroin structures are revealed by both advanced characterizations and simulations. It is found that CA interacts with fibroin, resulted in remarkably shorter crystallites, and thus giving the outstanding strength and toughness of the CA silk. The greatly enhanced mechanical properties are expected to lead to better functionalities and wider applications of the Bombyx mori silkworm silk. Silkworms usually produce white silk with normal feed containing no xenobiotics. Here, through introducing fluorescent xenobiotics into silkworm's diet and monitoring the resulting color and fluorescence in the silkworm's body, we established an understanding on the in vivo uptake of xenobiotics in silkworms that leads to direct production of intrinsically colored and/or luminescent silk by the silkworms. The molecular properties-directed absorption, distribution and excretion of xenobiotics were investigated using a series of fluorescent molecules as model compounds in a silkworm model. The efficient uptake of xenobiotics into silk is further studied through quantitative analysis of the intrinsically colored and highly luminescent silk secreted by silkworm. Criteria for effective uptake have been established based on the relationship between the structure-dependent hydrophobicity of various dyes vs. the amount selectively absorbed into the silk. The biological incorporation of dyes into silk, in particular its fibroin is a greener method of producing the functional silk because it eliminates the need of an external dyeing process, along with the resources (water, energy and additional chemicals) associated with conventional dyeing of silk. Beyond the absorption of dyes to produce color and luminescence in the silk, this feeding concept can also be expanded to incorporate other functional molecules (e.g., drugs, antibacterial agents, perfumes and nutrients) into silk with therapeutic or nutritional value.

Silks produced by insect labial glands

PubMed Central

Sutherland, Tara

2008-01-01

Insect silks are secreted from diverse gland types; this chapter deals with the silks produced by labial glands of Holometabola (insects with pupa in their life cycle). Labial silk glands are composed of a few tens or hundreds of large polyploid cells that secrete polymerizing proteins which are stored in the gland lumen as a semi-liquid gel. Polymerization is based on weak molecular interactions between repetitive amino acid motifs present in one or more silk proteins; cross-linking by disulfide bonds may be important in the silks spun under water. The mechanism of long-term storage of the silk dope inside the glands and its conversion into the silk fiber during spinning is not fully understood. The conversion occurs within seconds at ambient temperature and pressure, under minimal drawing force and in some cases under water. The silk filament is largely built of proteins called fibroins and in Lepidoptera and Trichoptera coated by glue-type proteins known as sericins. Silks often contain small amounts of additional proteins of poorly known function. The silk components controlling dope storage and filament formation seem to be conserved at the level of orders, while the nature of polymerizing motifs in the fibroins, which determine the physical properties of silk, differ at the level of family and even genus. Most silks are based on fibroin β-sheets interrupted with other structures such as α-helices but the silk proteins of certain sawflies have predominantly a collagen-like or polyglycine II arrangement and the silks of social Hymenoptera are formed from proteins in a coiled coil arrangement. PMID:19221523

Fabrication and characterization of biomaterial film from gland silk of muga and eri silkworms.

PubMed

Dutta, Saranga; Talukdar, Bijit; Bharali, Rupjyoti; Rajkhowa, Rangam; Devi, Dipali

2013-05-01

This study discusses the possibilities of liquid silk (Silk gland silk) of Muga and Eri silk, the indigenous non mulberry silkworms of North Eastern region of India, as potential biomaterials. Silk protein fibroin of Bombyx mori, commonly known as mulberry silkworm, has been extensively studied as a versatile biomaterial. As properties of different silk-based biomaterials vary significantly, it is important to characterize the non mulberry silkworms also in this aspect. Fibroin was extracted from the posterior silk gland of full grown fifth instars larvae, and 2D film was fabricated using standard methods. The films were characterized using SEM, Dynamic contact angle test, FTIR, XRD, DSC, and TGA and compared with respective silk fibers. SEM images of films reveal presence of some globules and filamentous structure. Films of both the silkworms were found to be amorphous with random coil conformation, hydrophobic in nature, and resistant to organic solvents. Non mulberry silk films had higher thermal resistance than mulberry silk. Fibers were thermally more stable than the films. This study provides insight into the new arena of research in application of liquid silk of non mulberry silkworms as biomaterials. Copyright © 2012 Wiley Periodicals, Inc.

Multifunctional silk-heparin biomaterials for vascular tissue engineering applications

PubMed Central

Seib, F. Philipp; Herklotz, Manuela; Burke, Kelly A.; Maitz, Manfred F.; Werner, Carsten; Kaplan, David L.

2013-01-01

Over the past 30 years, silk has been proposed for numerous biomedical applications that go beyond its traditional use as a suture material. Silk sutures are well tolerated in humans, but the use of silk for vascular engineering applications still requires extensive biocompatibility testing. Some studies have indicated a need to modify silk to yield a hemocompatible surface. This study examined the potential of low molecular weight heparin as a material for refining silk properties by acting as a carrier for vascular endothelial growth factor (VEGF) and improving silk hemocompatibility. Heparinized silk showed a controlled VEGF release over 6 days; the released VEGF was bioactive and supported the growth of human endothelial cells. Silk samples were then assessed using a humanized hemocompatibility system that employs whole blood and endothelial cells. The overall thrombogenic response for silk was very low and similar to the clinical reference material polytetrafluoroethylene. Despite an initial inflammatory response to silk, apparent as complement and leukocyte activation, the endothelium was maintained in a resting, anticoagulant state. The low thrombogenic response and the ability to control VEGF release support the further development of silk for vascular applications. PMID:24099708

Single Honeybee Silk Protein Mimics Properties of Multi-Protein Silk

PubMed Central

Sutherland, Tara D.; Church, Jeffrey S.; Hu, Xiao; Huson, Mickey G.; Kaplan, David L.; Weisman, Sarah

2011-01-01

Honeybee silk is composed of four fibrous proteins that, unlike other silks, are readily synthesized at full-length and high yield. The four silk genes have been conserved for over 150 million years in all investigated bee, ant and hornet species, implying a distinct functional role for each protein. However, the amino acid composition and molecular architecture of the proteins are similar, suggesting functional redundancy. In this study we compare materials generated from a single honeybee silk protein to materials containing all four recombinant proteins or to natural honeybee silk. We analyse solution conformation by dynamic light scattering and circular dichroism, solid state structure by Fourier Transform Infrared spectroscopy and Raman spectroscopy, and fiber tensile properties by stress-strain analysis. The results demonstrate that fibers artificially generated from a single recombinant silk protein can reproduce the structural and mechanical properties of the natural silk. The importance of the four protein complex found in natural silk may lie in biological silk storage or hierarchical self-assembly. The finding that the functional properties of the mature material can be achieved with a single protein greatly simplifies the route to production for artificial honeybee silk. PMID:21311767

Silk Materials Functionalized via Genetic Engineering for Biomedical Applications.

PubMed

Deptuch, Tomasz; Dams-Kozlowska, Hanna

2017-12-12

The great mechanical properties, biocompatibility and biodegradability of silk-based materials make them applicable to the biomedical field. Genetic engineering enables the construction of synthetic equivalents of natural silks. Knowledge about the relationship between the structure and function of silk proteins enables the design of bioengineered silks that can serve as the foundation of new biomaterials. Furthermore, in order to better address the needs of modern biomedicine, genetic engineering can be used to obtain silk-based materials with new functionalities. Sequences encoding new peptides or domains can be added to the sequences encoding the silk proteins. The expression of one cDNA fragment indicates that each silk molecule is related to a functional fragment. This review summarizes the proposed genetic functionalization of silk-based materials that can be potentially useful for biomedical applications.

Analysis of proteome dynamics inside the silk gland lumen of Bombyx mori.

PubMed

Dong, Zhaoming; Zhao, Ping; Zhang, Yan; Song, Qianru; Zhang, Xiaolu; Guo, Pengchao; Wang, Dandan; Xia, Qingyou

2016-04-22

The silk gland is the only organ where silk proteins are synthesized and secreted in the silkworm, Bombyx mori. Silk proteins are stored in the lumen of the silk gland for around eight days during the fifth instar. Determining their dynamic changes is helpful for clarifying the secretion mechanism of silk proteins. Here, we identified the proteome in the silk gland lumen using liquid chromatography-tandem mass spectrometry, and demonstrated its changes during two key stages. From day 5 of the fifth instar to day 1 of wandering, the abundances of fibroins, sericins, seroins, and proteins of unknown functions increased significantly in different compartments of the silk gland lumen. As a result, these accumulated proteins constituted the major cocoon components. In contrast, the abundances of enzymes and extracellular matrix proteins decreased in the silk gland lumen, suggesting that they were not the structural constituents of silk. Twenty-five enzymes may be involved in the regulation of hormone metabolism for proper silk gland function. In addition, the metabolism of other non-proteinous components such as chitin and pigment were also discussed in this study.

Analysis of proteome dynamics inside the silk gland lumen of Bombyx mori

PubMed Central

Dong, Zhaoming; Zhao, Ping; Zhang, Yan; Song, Qianru; Zhang, Xiaolu; Guo, Pengchao; Wang, Dandan; Xia, Qingyou

2016-01-01

The silk gland is the only organ where silk proteins are synthesized and secreted in the silkworm, Bombyx mori. Silk proteins are stored in the lumen of the silk gland for around eight days during the fifth instar. Determining their dynamic changes is helpful for clarifying the secretion mechanism of silk proteins. Here, we identified the proteome in the silk gland lumen using liquid chromatography–tandem mass spectrometry, and demonstrated its changes during two key stages. From day 5 of the fifth instar to day 1 of wandering, the abundances of fibroins, sericins, seroins, and proteins of unknown functions increased significantly in different compartments of the silk gland lumen. As a result, these accumulated proteins constituted the major cocoon components. In contrast, the abundances of enzymes and extracellular matrix proteins decreased in the silk gland lumen, suggesting that they were not the structural constituents of silk. Twenty-five enzymes may be involved in the regulation of hormone metabolism for proper silk gland function. In addition, the metabolism of other non-proteinous components such as chitin and pigment were also discussed in this study. PMID:27102218

Effect of Processing on Silk-Based Biomaterials: Reproducibility and Biocompatibility

PubMed Central

Wray, Lindsay S.; Hu, Xiao; Gallego, Jabier; Georgakoudi, Irene; Omenetto, Fiorenzo G.; Schmidt, Daniel; Kaplan, David L.

2012-01-01

Silk fibroin has been successfully used as a biomaterial for tissue regeneration. In order to prepare silk fibroin biomaterials for human implantation a series of processing steps are required to purify the protein. Degumming to remove inflammatory sericin is a crucial step related to biocompatibility and variability in the material. Detailed characterization of silk fibroin degumming is reported. The degumming conditions significantly affected cell viability on the silk fibroin material and the ability to form three-dimensional porous scaffolds from the silk fibroin, but did not affect macrophage activation or β-sheet content in the materials formed. Methods are also provided to determine the content of residual sericin in silk fibroin solutions and to assess changes in silk fibroin molecular weight. Amino acid composition analysis was used to detect sericin residuals in silk solutions with a detection limit between 1.0% and 10% wt/wt, while fluorescence spectroscopy was used to reproducibly distinguish between silk samples with different molecular weights. Both methods are simple and require minimal sample volume, providing useful quality control tools for silk fibroin preparation processes. PMID:21695778

Spider Silk Fibers Spun from Soluble Recombinant Silk Produced in Mammalian Cells

NASA Astrophysics Data System (ADS)

Lazaris, Anthoula; Arcidiacono, Steven; Huang, Yue; Zhou, Jiang-Feng; Duguay, François; Chretien, Nathalie; Welsh, Elizabeth A.; Soares, Jason W.; Karatzas, Costas N.

2002-01-01

Spider silks are protein-based ``biopolymer'' filaments or threads secreted by specialized epithelial cells as concentrated soluble precursors of highly repetitive primary sequences. Spider dragline silk is a flexible, lightweight fiber of extraordinary strength and toughness comparable to that of synthetic high-performance fibers. We sought to ``biomimic'' the process of spider silk production by expressing in mammalian cells the dragline silk genes (ADF-3/MaSpII and MaSpI) of two spider species. We produced soluble recombinant (rc)-dragline silk proteins with molecular masses of 60 to 140 kilodaltons. We demonstrated the wet spinning of silk monofilaments spun from a concentrated aqueous solution of soluble rc-spider silk protein (ADF-3; 60 kilodaltons) under modest shear and coagulation conditions. The spun fibers were water insoluble with a fine diameter (10 to 40 micrometers) and exhibited toughness and modulus values comparable to those of native dragline silks but with lower tenacity. Dope solutions with rc-silk protein concentrations >20% and postspinning draw were necessary to achieve improved mechanical properties of the spun fibers. Fiber properties correlated with finer fiber diameter and increased birefringence.

Silk ionomers for encapsulation and differentiation of human MSCs

PubMed Central

Calabrese, Rossella; Kaplan, David L.

2012-01-01

The response of human bone marrow derived human mesenchymal stem cells (hMSCs) encapsulated in silk ionomer hydrogels was studied. Silk aqueous solutions with silk-poly-L-lysine or silk-poly-L-glutamate were formed into hydrogels via ultrasonication in situ with different net charges. hMSCs were encapsulated within the hydrogels and the impact of matrix charge was assessed over weeks in osteogenic, adipogenic and maintenance growth media. These modified silk charged polymers supported cell viability and proliferative potential, and the hMSCs were able to differentiate toward osteogenic or adipogenic lineages in the corresponding differentiation media. The silk/silk-poly-L-lysine hydrogels exhibited a positive effect on selective osteogenesis of hMSCs, inducing differentiation toward an osteogenic lineage even in the absence of osteogenic supplements, while also inhibiting adipogenesis. In contrast, silk/silk fibroin-poly-L-glutamate hydrogels supported both osteogenic and adipogenic differentiation of hMSCs when cultured under induction conditions. The results demonstrate the potential utility of silk-based ionomers in gel formats for hMSCs encapsulation and for directing hMSCs long term functional differentiation toward specific lineages. PMID:22824008

High-Toughness Silk Produced by a Transgenic Silkworm Expressing Spider (Araneus ventricosus) Dragline Silk Protein

PubMed Central

Kuwana, Yoshihiko; Sezutsu, Hideki; Nakajima, Ken-ichi; Tamada, Yasushi; Kojima, Katsura

2014-01-01

Spider dragline silk is a natural fiber that has excellent tensile properties; however, it is difficult to produce artificially as a long, strong fiber. Here, the spider (Araneus ventricosus) dragline protein gene was cloned and a transgenic silkworm was generated, that expressed the fusion protein of the fibroin heavy chain and spider dragline protein in cocoon silk. The spider silk protein content ranged from 0.37 to 0.61% w/w (1.4–2.4 mol%) native silkworm fibroin. Using a good silk-producing strain, C515, as the transgenic silkworm can make the raw silk from its cocoons for the first time. The tensile characteristics (toughness) of the raw silk improved by 53% after the introduction of spider dragline silk protein; the improvement depended on the quantity of the expressed spider dragline protein. To demonstrate the commercial feasibility for machine reeling, weaving, and sewing, we used the transgenic spider silk to weave a vest and scarf; this was the first application of spider silk fibers from transgenic silkworms. PMID:25162624

High-toughness silk produced by a transgenic silkworm expressing spider (Araneus ventricosus) dragline silk protein.

PubMed

Kuwana, Yoshihiko; Sezutsu, Hideki; Nakajima, Ken-ichi; Tamada, Yasushi; Kojima, Katsura

2014-01-01

Spider dragline silk is a natural fiber that has excellent tensile properties; however, it is difficult to produce artificially as a long, strong fiber. Here, the spider (Araneus ventricosus) dragline protein gene was cloned and a transgenic silkworm was generated, that expressed the fusion protein of the fibroin heavy chain and spider dragline protein in cocoon silk. The spider silk protein content ranged from 0.37 to 0.61% w/w (1.4-2.4 mol%) native silkworm fibroin. Using a good silk-producing strain, C515, as the transgenic silkworm can make the raw silk from its cocoons for the first time. The tensile characteristics (toughness) of the raw silk improved by 53% after the introduction of spider dragline silk protein; the improvement depended on the quantity of the expressed spider dragline protein. To demonstrate the commercial feasibility for machine reeling, weaving, and sewing, we used the transgenic spider silk to weave a vest and scarf; this was the first application of spider silk fibers from transgenic silkworms.

The role of capture spiral silk properties in the diversification of orb webs.

PubMed

Tarakanova, Anna; Buehler, Markus J

2012-12-07

Among a myriad of spider web geometries, the orb web presents a fascinating, exquisite example in architecture and evolution. Orb webs can be divided into two categories according to the capture silk used in construction: cribellate orb webs (composed of pseudoflagelliform silk) coated with dry cribellate threads and ecribellate orb webs (composed of flagelliform silk fibres) coated by adhesive glue droplets. Cribellate capture silk is generally stronger but less-extensible than viscid capture silk, and a body of phylogenic evidence suggests that cribellate capture silk is more closely related to the ancestral form of capture spiral silk. Here, we use a coarse-grained web model to investigate how the mechanical properties of spiral capture silk affect the behaviour of the whole web, illustrating that more elastic capture spiral silk yields a decrease in web system energy absorption, suggesting that the function of the capture spiral shifted from prey capture to other structural roles. Additionally, we observe that in webs with more extensible capture silk, the effect of thread strength on web performance is reduced, indicating that thread elasticity is a dominant driving factor in web diversification.

Dynamic Camouflage Materials Based on Silk-Reflectin Chimeras

DTIC Science & Technology

2012-08-01

Dynamic Camouflage Materials Based on Silk -Reflectin Chimeras Final Performance Report for FA9550-09-1-0513 (Program Manager: Hugh DeLong...efforts to bioengineer silk -reflectin chimeric proteins, with the silk component serving as one of the organizing elements for material functions and...Further contributions may also come from the silk due to its novel light guiding properties and diffractive optics. Variants in silk block sizes

Silk Materials Functionalized via Genetic Engineering for Biomedical Applications

PubMed Central

Deptuch, Tomasz

2017-01-01

The great mechanical properties, biocompatibility and biodegradability of silk-based materials make them applicable to the biomedical field. Genetic engineering enables the construction of synthetic equivalents of natural silks. Knowledge about the relationship between the structure and function of silk proteins enables the design of bioengineered silks that can serve as the foundation of new biomaterials. Furthermore, in order to better address the needs of modern biomedicine, genetic engineering can be used to obtain silk-based materials with new functionalities. Sequences encoding new peptides or domains can be added to the sequences encoding the silk proteins. The expression of one cDNA fragment indicates that each silk molecule is related to a functional fragment. This review summarizes the proposed genetic functionalization of silk-based materials that can be potentially useful for biomedical applications. PMID:29231863

Bioprospecting Finds the Toughest Biological Material: Extraordinary Silk from a Giant Riverine Orb Spider

PubMed Central

Agnarsson, Ingi; Kuntner, Matjaž; Blackledge, Todd A.

2010-01-01

Background Combining high strength and elasticity, spider silks are exceptionally tough, i.e., able to absorb massive kinetic energy before breaking. Spider silk is therefore a model polymer for development of high performance biomimetic fibers. There are over 41.000 described species of spiders, most spinning multiple types of silk. Thus we have available some 200.000+ unique silks that may cover an amazing breadth of material properties. To date, however, silks from only a few tens of species have been characterized, most chosen haphazardly as model organisms (Nephila) or simply from researchers' backyards. Are we limited to ‘blindly fishing’ in efforts to discover extraordinary silks? Or, could scientists use ecology to predict which species are likely to spin silks exhibiting exceptional performance properties? Methodology We examined the biomechanical properties of silk produced by the remarkable Malagasy ‘Darwin's bark spider’ (Caerostris darwini), which we predicted would produce exceptional silk based upon its amazing web. The spider constructs its giant orb web (up to 2.8 m2) suspended above streams, rivers, and lakes. It attaches the web to substrates on each riverbank by anchor threads as long as 25 meters. Dragline silk from both Caerostris webs and forcibly pulled silk, exhibits an extraordinary combination of high tensile strength and elasticity previously unknown for spider silk. The toughness of forcibly silked fibers averages 350 MJ/m3, with some samples reaching 520 MJ/m3. Thus, C. darwini silk is more than twice tougher than any previously described silk, and over 10 times better than Kevlar®. Caerostris capture spiral silk is similarly exceptionally tough. Conclusions Caerostris darwini produces the toughest known biomaterial. We hypothesize that this extraordinary toughness coevolved with the unusual ecology and web architecture of these spiders, decreasing the likelihood of bridgelines breaking and collapsing the web into the river. This hypothesis predicts that rapid change in material properties of silk co-occurred with ecological shifts within the genus, and can thus be tested by combining material science, behavioral observations, and phylogenetics. Our findings highlight the potential benefits of natural history–informed bioprospecting to discover silks, as well as other materials, with novel and exceptional properties to serve as models in biomimicry. PMID:20856804

GC/MS-based metabolomic studies reveal key roles of glycine in regulating silk synthesis in silkworm, Bombyx mori.

PubMed

Chen, Quanmei; Liu, Xinyu; Zhao, Ping; Sun, Yanhui; Zhao, Xinjie; Xiong, Ying; Xu, Guowang; Xia, Qingyou

2015-02-01

Metabolic profiling of silkworm, especially the factors that affect silk synthesis at the metabolic level, is little known. Herein, metabolomic method based on gas chromatography-mass spectrometry was applied to identify key metabolic changes in silk synthesis deficient silkworms. Forty-six differential metabolites were identified in Nd group with the defect of silk synthesis. Significant changes in the levels of glycine and uric acid (up-regulation), carbohydrates and free fatty acids (down-regulation) were observed. The further metabolomics of silk synthesis deficient silkworms by decreasing silk proteins synthesis using knocking out fibroin heavy chain gene or extirpating silk glands operation showed that the changes of the metabolites were almost consistent with those of the Nd group. Furthermore, the increased silk yields by supplying more glycine or its related metabolite confirmed that glycine is a key metabolite to regulate silk synthesis. These findings provide important insights into the regulation between metabolic profiling and silk synthesis. Copyright © 2014 Elsevier Ltd. All rights reserved.

Uncovering the structure-function relationship in spider silk

NASA Astrophysics Data System (ADS)

Yarger, Jeffery L.; Cherry, Brian R.; van der Vaart, Arjan

2018-03-01

All spiders produce protein-based biopolymer fibres that we call silk. The most studied of these silks is spider dragline silk, which is very tough and relatively abundant compared with other types of spider silks. Considerable research has been devoted to understanding the relationship between the molecular structure and mechanical properties of spider dragline silks. In this Review, we overview experimental and computational studies that have provided a wealth of detail at the molecular level on the highly conserved repetitive core and terminal regions of spider dragline silk. We also discuss the role of the nanocrystalline β-sheets and amorphous regions in determining the properties of spider silk fibres, endowing them with strength and elasticity. Additionally, we outline imaging techniques and modelling studies that elucidate the importance of the hierarchical structure of silk fibres at the molecular level. These insights into structure-function relationships can guide the reverse engineering of spider silk to enable the production of superior synthetic fibres.

Characterization and assembly of a GFP-tagged cylindriform silk into hexameric complexes.

PubMed

Öster, Carl; Svensson Bonde, Johan; Bülow, Leif; Dicko, Cedric

2014-04-01

Spider silk has been studied extensively for its attractive mechanical properties and potential applications in medicine and industry. The production of spider silk, however, has been lagging behind for lack of suitable systems. Our approach focuses on solving the production of spider silk by designing, expressing, purifying and characterizing the silk from cylindriform glands. We show that the cylindriform silk protein, in contrast to the commonly used dragline silk protein, is fully folded and stable in solution. With the help of GFP as a fusion tag we enhanced the expression of the silk protein in Escherichia coli and could optimize the downstream processing. Secondary structures analysis by circular dichroism and FTIR shows that the GFP-silk fusion protein is predominantly α-helical, and that pH can trigger a α- to β-transition resulting in aggregation. Structural analysis by small angle X-ray scattering suggests that the GFP-Silk exists in the form of a hexamer in solution. Copyright © 2013 Wiley Periodicals, Inc.

The elaborate structure of spider silk

PubMed Central

Römer, Lin

2008-01-01

Biomaterials, having evolved over millions of years, often exceed man-made materials in their properties. Spider silk is one outstanding fibrous biomaterial which consists almost entirely of large proteins. Silk fibers have tensile strengths comparable to steel and some silks are nearly as elastic as rubber on a weight to weight basis. In combining these two properties, silks reveal a toughness that is two to three times that of synthetic fibers like Nylon or Kevlar. Spider silk is also antimicrobial, hypoallergenic and completely biodegradable. This article focuses on the structure-function relationship of the characterized highly repetitive spider silk spidroins and their conformational conversion from solution into fibers. Such knowedge is of crucial importance to understanding the intrinsic properties of spider silk and to get insight into the sophisticated assembly processes of silk proteins. This review further outlines recent progress in recombinant production of spider silk proteins and their assembly into distinct polymer materials as a basis for novel products. PMID:19221522

Advancing the frontiers of silk fibroin protein-based materials for futuristic electronics and clinical wound-healing (Invited review).

PubMed

Koh, Leng-Duei; Yeo, Jingjie; Lee, Yeong Yuh; Ong, Qunya; Han, Mingyong; Tee, Benjamin C-K

2018-05-01

The present review will introduce the basic concepts of silk-based electronics/optoelectronics including the latest technological advances on the use of silk fibroin in combination with other functional components, with an emphasis on improving the performance of next-generation silk-based materials. It also highlights the patterning of silk fibroin to produce micro/nano-scale features, as well as the functionalization of silk fibroin to impart antimicrobial (i.e. antibacterial) properties. Silk-based bioelectronics have great potential for advanced or futuristic bio-applications including e-skins, e-bandages, biosensors, wearable displays, implantable devices, artificial muscles, etc. Notably, silk-based organic field-effect transistors have highly promising applications in e-skins and biosensors; silk-based electrodes/antennas are used for in vivo bioanalysis or sensing purpose (e.g., measurement of neurotransmitter such as dopamine) in addition to their use as food sensors; silk-based diodes can be applied as light sources for wound healing or tissue engineering, e.g., in cutaneous wound closure or induction of photothrombosis of corneal neovascularization; silk-based actuators have promising applications as artificial muscles; whereas silk-based memristors have exciting applications as logic or synaptic network for realizing e-skins or bionic brains. Copyright © 2018 Elsevier B.V. All rights reserved.

Improvement of Physical and Wound Adhesion Properties of Silk Sericin and Polyvinyl Alcohol Dressing Using Glycerin.

PubMed

Aramwit, Pornanong; Ratanavaraporn, Juthamas; Siritientong, Tippawan

2015-08-01

This study aimed to use glycerin to improve physical and wound adhesion properties of a wound dressing made of silk sericin and polyvinyl alcohol (PVA). Glycerin of a natural-derived plasticizer was used to modify the properties of silk sericin/PVA scaffolds. Various concentrations of glycerin were mixed with silk sericin and PVA and then fabricated into the scaffolds by a freeze-drying technique. The control study was performed to examine the properties of the silk sericin/PVA scaffolds with and without glycerin. Physical, mechanical, wound adhesion properties, the release profile of silk sericin, and in vivo safety of the silk sericin/PVA scaffolds with and without glycerin were investigated. The silk sericin/PVA scaffolds with glycerin exhibited more homogenous structure, less compressive modulus, higher Young modulus and elongation percentage, and a higher degree of crosslinking compared with the scaffold without glycerin. The silk sericin/PVA scaffold with 2% wt/vol glycerin showed more controlled release of silk sericin than the other scaffolds. The sustained release of silk sericin from the scaffold with glycerin would be advantageous for long-term healing of wounds. The silk sericin/PVA scaffold with 2% (wt/vol) glycerin was less adhesive to the wound compared with the scaffold without glycerin. Furthermore, the implantation of silk sericin/PVA scaffolds with 2% (wt/vol) glycerin did not cause any irritation to the tissue. The silk sericin/PVA scaffolds with glycerin were introduced as a biocompatible, more flexible, and less adhesive wound dressing than the scaffold without glycerin.

Silk gene expression of theridiid spiders: implications for male-specific silk use.

PubMed

Correa-Garhwal, Sandra M; Chaw, R Crystal; Clarke, Thomas H; Ayoub, Nadia A; Hayashi, Cheryl Y

2017-06-01

Spiders (order Araneae) rely on their silks for essential tasks, such as dispersal, prey capture, and reproduction. Spider silks are largely composed of spidroins, members of a protein family that are synthesized in silk glands. As needed, silk stored in silk glands is extruded through spigots on the spinnerets. Nearly all studies of spider silks have been conducted on females; thus, little is known about male silk biology. To shed light on silk use by males, we compared silk gene expression profiles of mature males to those of females from three cob-web weaving species (Theridiidae). We de novo assembled species-specific male transcriptomes from Latrodectus hesperus, Latrodectus geometricus, and Steatoda grossa followed by differential gene expression analyses. Consistent with their complement of silk spigots, male theridiid spiders express appreciable amounts of aciniform, major ampullate, minor ampullate, and pyriform spidroin genes but not tubuliform spidroin genes. The relative expression levels of particular spidroin genes varied between sexes and species. Because mature males desert their prey-capture webs and become cursorial in their search for mates, we anticipated that major ampullate (dragline) spidroin genes would be the silk genes most highly expressed by males. Indeed, major ampullate spidroin genes had the highest expression in S. grossa males. However, minor ampullate spidroin genes were the most highly expressed spidroin genes in L. geometricus and L. hesperus males. Our expression profiling results suggest species-specific adaptive divergence of silk use by male theridiids. Copyright © 2017 The Authors. Published by Elsevier GmbH.. All rights reserved.

Lithium-free processing of silk fibroin.

PubMed

Zheng, Zhaozhu; Guo, Shaozhe; Liu, Yawen; Wu, Jianbing; Li, Gang; Liu, Meng; Wang, Xiaoqin; Kaplan, David

2016-09-01

Silk fibroin protein was purified from Bombyx mori silkworm cocoons using a novel dialysis strategy to avoid fibroin aggregation and pre-mature formation of β-sheets. The degummed silk fibers were dissolved in Ajisawa's reagent, a mixture of CaCl2-EtOH-H2O, that is less expensive than lithium bromide. The dissolved solutions were dialyzed against either water or urea solution with a stepwise decrease in concentration. When the steps of 4 M-2 M-1 M-0 M urea (referred to as silk-TS-4210) were adopted, the purified silk fibroin had smaller aggregates (<10 nm), similar average molecular weight (225 kDa) and a lower content of β-sheet (∼15%) compared to the sample processing methods (silk-TS-210, 10, 0) studied here. This outcome was close to the fibroin purified by the lithium bromide (silk-Li-0) method. Polyvinyl alcohol-emulsified silk microspheres generated using the purified solution had a similar size distribution and morphology when compared to lithium bromide dissolved solutions, while glycerol-blended silk films showed different mechanical properties. The silk-Li-0 generated films with the highest breaking strength (5.7 MPa ± 0.3) while the silk-TS-4210 had the highest extension at break (215.1% ± 12.5). The films prepared from silk-TS-4210 were cytocompatible to support the adhesion and proliferation of human mesenchymal stem cells, with improvements compared to the other samples likely due to the porous morphology of these films. © The Author(s) 2016.

Production And Characterization Of Synthetic Spider Silks Based On Nephila Clavipes Major Ampullate Silk Proteins

NASA Astrophysics Data System (ADS)

An, Bo

The extraordinary mechanical properties of orb-weaving spider silks have served spiders for over 400 million years. However, only in the late 20th century did we start to understand the molecular nature of spider silk that contributes to its incredible properties as biomaterials. Among all seven types of spider silks, major ampullate silk from typical orb-weaving spiders is the toughest of all, it consists of primarily two proteins: MaSp1 and MaSp2. Variable ratios and conserved motifs of these two proteins in all the native spider silks demonstrate the significant role of MaSp1 and MaSp2 in controlling the mechanical properties of the fiber. The amino acid sequences of the orb weaving spider silk proteins have remained almost unchanged for more than 100 million years. Interestingly, MaSp1 and MaSp2 are the only two components in all studied dragline silk fibers from these spiders. The mechanical properties of native dragline silk vary slightly between species, which are believed to relate to the ratio of MaSp1 to MaSp2 in the silk. Both of these facts clearly indicate the importance of these two proteins to the mechanical properties of the fiber. Various types of synthetic spider silk fibers have been produced and studied in an effort to mass-produce man-made fibers with qualities comparable to native spider silk. To investigate the roles of MaSp1 and MaSp2 in silk fiber, synthetic MaSp1 (major abundant protein in Nephila clavipes major ampullate silks) only fibers, MaSp1/MaSp2 protein mixture fibers and chimeric protein fibers with both MaSp1 and MaSp2 sequence features have been produced and tested for mechanical properties. Solid-State Nuclear Magnetic Resonance was used to characterize the structure of silk fibers and reveal the relation between fiber spatial structure and mechanical properties.

Biotechnology and Composite Materials

DTIC Science & Technology

1993-04-01

protein fibroin which are glued together by the protein sericin . Many other insects produce silk, most notably spiders. Spider silks Zre proteins with...silk is boiled to remove the soluble sticky sericin protein, and the remaining fibroin portion of the silk is then unwound and used as silk fiber. Orb

Control of silk microsphere formation using polyethylene glycol (PEG).

PubMed

Wu, Jianbing; Zheng, Zhaozhu; Li, Gang; Kaplan, David L; Wang, Xiaoqin

2016-07-15

A one step, rapid method to prepare silk microspheres was developed, with particle size controlled by the addition of polyethylene glycol (PEG). PEG molecular weight (4.0K-20.0KDa) and concentration (20-50wt%), as well as silk concentration (5-20wt%), were key factors that determined particle sizes varying in a range of 1-100μm. Addition of methanol to the PEG-silk combinations increased the content of crystalline β-sheet in the silk microspheres. To track the distribution and degradation of silk microspheres in vivo, 3-mercaptopropionic acid (MPA)-coated CdTe quantum dots (QDs) were physically entrapped in the silk microspheres. QDs tightly bound to the β-sheet domains of silk via hydrophobic interactions, with over 96% of the loaded QDs remaining in the silk microspheres after exhaustive extraction. The fluorescence of QDs-incorporated silk microspheres less stable in cell culture medium than in phosphate buffer solution (PBS) and water. After subcutaneous injection in mice, microspheres prepared from 20% silk (approx. 30μm diameter particles) still fluoresced at 24h, while those prepared from 8% silk (approx. 4μm diameter particles) and free QDs were not detectable, reflecting the QDs quenching and particle size effect on microsphere clearance in vivo. The larger microspheres were more resistant to cell internalization and degradation. Since PEG is an FDA-approved polymer, and silk is FDA approved for some medical devices, the methods developed in the present study will be useful in a variety of biomedical applications where simple, rapid and scalable preparation of silk microspheres is required. The work is of significance to the biomaterial and controlled release society because it provides a new option for fabricating silk microspheres in one simple step of mixing silk and polyethylene glycol (PEG), with the size and properties of microspheres controllable by PEG molecular weight as well as PEG and silk concentrations. Although fabrication of silk microspheres have been reported previously using spray-drying, liposome-templating, polyvinyl alcohol (PVA) emulsification, etc., applications were hindered due to harsh conditions (temperature, solvents, etc.) and complicated procedures used as well as low yield and less controllable particle size (usually <10μm). Since PEG is an FDA-approved polymer, and silk is FDA approved for some medical devices, the methods developed in the present study will be useful in a variety of biomedical applications where simple, rapid and scalable preparation of silk microspheres is required. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Spider Webs and Silks.

ERIC Educational Resources Information Center

Vollrath, Fritz

1992-01-01

Compares the attributes of the silk from spiders with those of the commercially harvested silk from silkworms. Discusses the evolution, design, and effectiveness of spider webs; the functional mechanics of the varieties of silk that can be produced by the same spider; and the composite, as well as molecular, structure of spider silk thread. (JJK)

Recombinant DNA production of spider silk proteins

PubMed Central

Tokareva, Olena; Michalczechen-Lacerda, Valquíria A; Rech, Elíbio L; Kaplan, David L

2013-01-01

Spider dragline silk is considered to be the toughest biopolymer on Earth due to an extraordinary combination of strength and elasticity. Moreover, silks are biocompatible and biodegradable protein-based materials. Recent advances in genetic engineering make it possible to produce recombinant silks in heterologous hosts, opening up opportunities for large-scale production of recombinant silks for various biomedical and material science applications. We review the current strategies to produce recombinant spider silks. PMID:24119078

Mechanics and Morphology of Silk Drawn from Anesthetized Spiders

NASA Astrophysics Data System (ADS)

Madsen, B.; Vollrath, F.

CO2 and N2 anesthetized Nephila spiders produced dragline silk with mechanical properties that differed from control silk as a function of time under anesthesia. Silk from CO2 spiders had a significantly lower breaking strain and breaking energy, significantly higher initial modulus, and marginally lower breaking stress. At the onset of anesthesia the silk diameter became highly variable. During deep anesthesia silk either became thinner or retained cross-section but fibrillated.

Facts and myths of antibacterial properties of silk.

PubMed

Kaur, Jasjeet; Rajkhowa, Rangam; Afrin, Tarannum; Tsuzuki, Takuya; Wang, Xungai

2014-03-01

Silk cocoons provide protection to silkworm from biotic and abiotic hazards during the immobile pupal phase of the lifecycle of silkworms. Protection is particularly important for the wild silk cocoons reared in an open and harsh environment. To understand whether some of the cocoon components resist growth of microorganisms, in vitro studies were performed using gram negative bacteria Escherichia coli (E. coli) to investigate antibacterial properties of silk fiber, silk gum, and calcium oxalate crystals embedded inside some cocoons. The results show that the previously reported antibacterial properties of silk cocoons are actually due to residues of chemicals used to isolate/purify cocoon elements, and properly isolated silk fiber, gum, and embedded crystals free from such residues do not have inherent resistance to E. coli. This study removes the uncertainty created by previous studies over the presence of antibacterial properties of silk cocoons, particularly the silk gum and sericin. Copyright © 2013 Wiley Periodicals, Inc.

PEGylated Silk Nanoparticles for Anticancer Drug Delivery.

PubMed

Wongpinyochit, Thidarat; Uhlmann, Petra; Urquhart, Andrew J; Seib, F Philipp

2015-11-09

Silk has a robust clinical track record and is emerging as a promising biopolymer for drug delivery, including its use as nanomedicine. However, silk-based nanomedicines still require further refinements for full exploitation of their potential; the application of "stealth" design principals is especially necessary to support their evolution. The aim of this study was to develop and examine the potential of PEGylated silk nanoparticles as an anticancer drug delivery system. We first generated B. mori derived silk nanoparticles by driving β-sheet assembly (size 104 ± 1.7 nm, zeta potential -56 ± 5.6 mV) using nanoprecipitation. We then surface grafted polyethylene glycol (PEG) to the fabricated silk nanoparticles and verified the aqueous stability and morphology of the resulting PEGylated silk nanoparticles. We assessed the drug loading and release behavior of these nanoparticles using clinically established and emerging anticancer drugs. Overall, PEGylated silk nanoparticles showed high encapsulation efficiency (>93%) and a pH-dependent release over 14 days. Finally, we demonstrated significant cytotoxicity of drug loaded silk nanoparticles applied as single and combination nanomedicines to human breast cancer cells. In conclusion, these results, taken together with prior silk nanoparticle data, support a viable future for silk-based nanomedicines.

The role of capture spiral silk properties in the diversification of orb webs

PubMed Central

Tarakanova, Anna; Buehler, Markus J.

2012-01-01

Among a myriad of spider web geometries, the orb web presents a fascinating, exquisite example in architecture and evolution. Orb webs can be divided into two categories according to the capture silk used in construction: cribellate orb webs (composed of pseudoflagelliform silk) coated with dry cribellate threads and ecribellate orb webs (composed of flagelliform silk fibres) coated by adhesive glue droplets. Cribellate capture silk is generally stronger but less-extensible than viscid capture silk, and a body of phylogenic evidence suggests that cribellate capture silk is more closely related to the ancestral form of capture spiral silk. Here, we use a coarse-grained web model to investigate how the mechanical properties of spiral capture silk affect the behaviour of the whole web, illustrating that more elastic capture spiral silk yields a decrease in web system energy absorption, suggesting that the function of the capture spiral shifted from prey capture to other structural roles. Additionally, we observe that in webs with more extensible capture silk, the effect of thread strength on web performance is reduced, indicating that thread elasticity is a dominant driving factor in web diversification. PMID:22896566

High-performance spider webs: integrating biomechanics, ecology and behaviour

PubMed Central

Harmer, Aaron M. T.; Blackledge, Todd A.; Madin, Joshua S.; Herberstein, Marie E.

2011-01-01

Spider silks exhibit remarkable properties, surpassing most natural and synthetic materials in both strength and toughness. Orb-web spider dragline silk is the focus of intense research by material scientists attempting to mimic these naturally produced fibres. However, biomechanical research on spider silks is often removed from the context of web ecology and spider foraging behaviour. Similarly, evolutionary and ecological research on spiders rarely considers the significance of silk properties. Here, we highlight the critical need to integrate biomechanical and ecological perspectives on spider silks to generate a better understanding of (i) how silk biomechanics and web architectures interacted to influence spider web evolution along different structural pathways, and (ii) how silks function in an ecological context, which may identify novel silk applications. An integrative, mechanistic approach to understanding silk and web function, as well as the selective pressures driving their evolution, will help uncover the potential impacts of environmental change and species invasions (of both spiders and prey) on spider success. Integrating these fields will also allow us to take advantage of the remarkable properties of spider silks, expanding the range of possible silk applications from single threads to two- and three-dimensional thread networks. PMID:21036911

Effects of Japanese beetle (Coleoptera: Scarabaeidae) and silk clipping in field corn.

PubMed

Steckel, Sandy; Stewart, S D; Tindall, K V

2013-10-01

Japanese beetle (Popillia japonica Newman) is an emerging silk-feeding insect found in fields in the lower Corn Belt and Midsouthern United States. Studies were conducted in 2010 and 2011 to evaluate how silk clipping in corn affects pollination and yield parameters. Manually clipping silks once daily had modest effects on yield parameters. Sustained clipping by either manually clipping silks three times per day or by caging Japanese beetles onto ears affected total kernel weight if it occurred during early silking (R1 growth stage). Manually clipping silks three times per day for the first 5 d of silking affected the number of kernels per ear, total kernel weight, and the weight of individual kernels. Caged beetles fed on silks and, depending on the number of beetles caged per ear, reduced the number of kernels per ear. Caging eight beetles per ear significantly reduced total kernel weight compared with noninfested ears. Drought stress before anthesis appeared to magnify the impact of silk clipping by Japanese beetles. There was evidence of some compensation for reduced pollination by increasing the size of pollinated kernels within the ear. Our results showed that it requires sustained silk clipping during the first week of silking to have substantial impacts on pollination and yield parameters, at least under good growing conditions. Some states recommend treating for Japanese beetle when three Japanese beetles per ear are found, silks are clipped to < 13 mm, and pollination is < 50% complete, and that recommendation appears to be adequate.

Genetic engineered color silk: fabrication of a photonics material through a bioassisted technology.

PubMed

Shimizu, Katsuhiko

2018-05-15

Silk produced by the silkworm Bombyx mori is an attractive material because of its luster, smooth and soft texture, conspicuous mechanical strength, good biocompatibility, slow biodegradation, and carbon neutral synthesis. Silkworms have been domesticated and bred for production of better quality and quantity of silk, resulting in the development of sericulture and the textile industry. Silk is generally white, so dyeing is required to obtain colored fiber. However, the dyeing process involves harsh conditions and generates a large volume of waste water, which have environmentally and economically negative impacts. Although some strains produce cocoons that contain pigments derived from the mulberry leaves that they eat, the pigments are distributed in the sericin layer and are lost during gumming. In trials for production of colored silk by feeding silkworms on diets containing dyes, only limited species of dye molecules were incorporated into the silk threads. A method for the generation of transgenic silkworm was established in conjunction with the discovery of green fluorescent protein (GFP), and silkworms carrying the GFP gene spun silk threads that formed cocoons that glowed bright green and still retained the original properties of silk. A wide range of color variation of silk threads has been obtained by replacing the GFP gene with the genes of other fluorescent proteins chosen from the fluorescent protein palette. The genetically modified silk with photonic properties can be processed to form various products including linear threads, 2D fabrics, and 3D materials. The transgenic colored silk could be economically advantageous due to addition of a new value to silk and reduction of cost for water waste, and environmentally preferable for saving water. Here, I review the literature regarding the production methods of fluorescent silk from transgenic silkworms and present examples of genetically modified color silk.

Curcumin-functionalized silk biomaterials for anti-aging utility.

PubMed

Yang, Lei; Zheng, Zhaozhu; Qian, Cheng; Wu, Jianbing; Liu, Yawen; Guo, Shaozhe; Li, Gang; Liu, Meng; Wang, Xiaoqin; Kaplan, David L

2017-06-15

Curcumin is a natural antioxidant that is isolated from turmeric (Curcuma longa) and exhibits strong free radical scavenging activity, thus functional for anti-aging. However, poor stability and low solubility of curcumin in aqueous conditions limit its biomedical applications. Previous studies have shown that the anti-oxidation activity of curcumin embedded in silk fibroin films could be well preserved, resulting in the promoted adipogenesis from human mesenchymal stem cells (hMSCs) cultured on the surface of the films. In the present study, curcumin was encapsulated in both silk fibroin films (silk/cur films) and nanoparticles (silk/cur NPs), and their anti-aging effects were compared with free curcumin in solution, with an aim to elucidate the mechanism of anti-aging of silk-associated curcumin and to better serve biomedical applications in the future. The morphology and structure of silk/cur film and silk/cur NP were characterized using SEM, FTIR and DSC, indicating characteristic stable beta-sheet structure formation in the materials. Strong binding of curcumin molecules to the beta-sheet domains of silk fibroin resulted in the slow release of curcumin with well-preserved activity from the materials. For cell aging studies, rat bone marrow mesenchymal stem cells (rBMSCs) were cultured in the presence of free curcumin (FC), silk/cur film and silk/cur NP, and cell proliferation and markers of aging (P53, P16, HSP70 gene expression and β-Galactosidase activity) were examined. The results indicated that cell aging was retarded in all FC, silk/cur NP and silk/cur film samples, with the silk-associated curcumin superior to the FC. Copyright © 2017 Elsevier Inc. All rights reserved.

Environmentally friendly surface modification of silk fiber: Chitosan grafting and dyeing

NASA Astrophysics Data System (ADS)

Davarpanah, Saideh; Mahmoodi, Niyaz Mohammad; Arami, Mokhtar; Bahrami, Hajir; Mazaheri, Firoozmehr

2009-01-01

In this paper, the surface modification of silk fiber using anhydrides to graft the polysaccharide chitosan and dyeing ability of the grafted silk were studied. Silk fiber was degummed and acylated with two anhydrides, succinic anhydride (SA) and phthalic anhydride (PA), in different solvents (dimethyl sulfoxide (DMSO) and N, N-dimethyl formamide (DMF)). The effects of anhydrides, solvents, anhydride concentration, liquor ratio (L:R) and reaction time on acylation of silk were studied. The polysaccharide chitosan was grafted to the acylated silk fiber and dyed by acid dye (Acid Black NB.B). The effects of pH, chitosan concentration, and reaction time on chitosan grafting of acylated silk were investigated. The physical properties show sensible changes regardless of weight gain. Scanning electron microscopy (SEM) analysis showed the presence of foreign materials firmly attached to the surface of silk. FTIR spectroscopy provided evidence that chitosan was grafted onto the acylated silk through the formation of new covalent bonds. The dyeing of the chitosan grafted-acylated silk fiber indicated the higher dye ability in comparison to the acylated and degummed silk samples. The mechanism of chitosan grafting over degummed silk through anhydride linkage was proposed. The findings of this research support the potential production of new environmentally friendly textile fibers. It is worthwhile to mention that the grafted samples have antibacterial potential due to the antibacterial property of chitosan molecules.

Cell proliferation by silk gut incorporating FGF-2 protein microcrystals.

PubMed

Kotani, Eiji; Yamamoto, Naoto; Kobayashi, Isao; Uchino, Keiro; Muto, Sayaka; Ijiri, Hiroshi; Shimabukuro, Junji; Tamura, Toshiki; Sezutsu, Hideki; Mori, Hajime

2015-06-08

Silk gut processed from the silk glands of the silkworm could be an ideal biodegradable carrier for cell growth factors. We previously demonstrated that polyhedra, microcrystals of Cypovirus 1 polyhedrin, can serve as versatile carrier proteins. Here, we report the generation of a transgenic silkworm that expresses polyhedrin together with human basic fibroblast growth factor (FGF-2) in its posterior silk glands to utilize silk gut as a proteinaceous carrier to protect and slowly release active cell growth factors. In the posterior silk glands, polyhedrin formed polyhedral microcrystals, and FGF-2 became encapsulated within the polyhedra due to a polyhedron-immobilization signal. Silk gut powder prepared from posterior silk glands containing polyhedron-encapsulated FGF-2 stimulated the phosphorylation of p44/p42 MAP kinase and induced the proliferation of serum-starved NIH3T3 cells by releasing bioactive FGF-2. Even after a one-week incubation at 25 °C, significantly higher biological activity of FGF-2 was observed for silk gut powder incorporating polyhedron-encapsulated FGF-2 relative to silk gut powder with non-encapsulated FGF-2. Our results demonstrate that posterior silk glands incorporating polyhedron-encapsulated FGF-2 are applicable to the preparation of biodegradable silk gut, which can protect and release FGF-2 that is produced in a virus- and serum-free expression system with significant application potential.

A novel marine silk.

PubMed

Kronenberger, Katrin; Dicko, Cedric; Vollrath, Fritz

2012-01-01

The discovery of a novel silk production system in a marine amphipod provides insights into the wider potential of natural silks. The tube-building corophioid amphipod Crassicorophium bonellii produces from its legs fibrous, adhesive underwater threads that combine barnacle cement biology with aspects of spider silk thread extrusion spinning. We characterised the filamentous silk as a mixture of mucopolysaccharides and protein deriving from glands representing two distinct types. The carbohydrate and protein silk secretion is dominated by complex β-sheet structures and a high content of charged amino acid residues. The filamentous secretion product exits the gland through a pore near the tip of the secretory leg after having moved through a duct, which subdivides into several small ductules all terminating in a spindle-shaped chamber. This chamber communicates with the exterior and may be considered the silk reservoir and processing/mixing space, in which the silk is mechanically and potentially chemically altered and becomes fibrous. We assert that further study of this probably independently evolved, marine arthropod silk processing and secretion system can provide not only important insights into the more complex arachnid and insect silks but also into crustacean adhesion cements.

Discerning Silk Produced by Bombyx mori from Those Produced by Wild Species Using an Enzyme-Linked Immunosorbent Assay Combined with Conventional Methods.

PubMed

You, Qiushi; Li, Qingqing; Zheng, Hailing; Hu, Zhiwen; Zhou, Yang; Wang, Bing

2017-09-06

Recently, much interest has been paid to the separation of silk produced by Bombyx mori from silk produced by other species and tracing the beginnings of silk cultivation from wild silk exploitation. In this paper, significant differences between silks from Bombyx mori and other species were found by microscopy and spectroscopy, such as morphology, secondary structure, and amino acid composition. For further accurate identification, a diagnostic antibody was designed by comparing the peptide sequences of silks produced by Bombyx mori and other species. The results of the noncompetitive indirect enzyme-linked immunosorbent assay (ELISA) indicated that the antibody that showed good sensitivity and high specificity can definitely discern silk produced by Bombyx mori from silk produced by wild species. Thus, the antibody-based immunoassay has the potential to be a powerful tool for tracing the beginnings of silk cultivation. In addition, combining the sensitive, specific, and convenient ELISA technology with other conventional methods can provide more in-depth and accurate information for species identification.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Okada, Shoko; Weisman, Sarah; Trueman, Holly E.

Aposthonia gurneyi, an Australian webspinner species, is a primitive insect that constructs and lives in a silken tunnel which screens it from the attentions of predators. The insect spins silk threads from many tiny spines on its forelegs to weave a filmy sheet. We found that the webspinner silk fibers have a mean diameter of only 65 nm, an order of magnitude smaller than any previously reported insect silk. The purpose of such fine silk may be to reduce the metabolic cost of building the extensive tunnels. At the molecular level, the A. gurneyi silk has a predominantly beta-sheet proteinmore » structure. The most abundant clone in a cDNA library produced from the webspinner silk glands encoded a protein with extensive glycine-serine repeat regions. The GSGSGS repeat motif of the A. gurneyi silk protein is similar to the well-known GAGAGS repeat motif found in the heavy fibroin of silkworm silk, which also has beta-sheet structure. As the webspinner silk gene is unrelated to the silk gene of the phylogenetically distant silkworm, this is a striking example of convergent evolution.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cebe, Peggy; Partlow, Benjamin P.; Kaplan, David L.

Using fast scanning calorimetry (FSC), we investigated the glass transition and crystal melting of samples of B. mori silk fibroin containing Silk I and/or Silk II crystals. Due to the very short residence times at high temperatures during such measurements, thermal decomposition of silk protein can be significantly suppressed. FSC was performed at 2000 K/s using the Mettler Flash DSC1 on fibroin films with masses around 130–270 ng. Films were prepared with different crystalline fractions (ranging from 0.26 to 0.50) and with different crystal structures (Silk I, Silk II, or mixed) by varying the processing conditions. These included water annealingmore » at different temperatures, exposure to 50% MeOH in water, or autoclaving. The resulting crystal structure was examined using wide angle X-ray scattering. Degree of crystallinity was evaluated from Fourier transform infrared (FTIR) spectroscopy and from analysis of the heat capacity increment at the glass transition temperature. Silk fibroin films prepared by water annealing at 25 °C were the least crystalline and had Silk I structure. FTIR and FSC studies showed that films prepared by autoclaving or 50% MeOH exposure were the most crystalline and had Silk II structure. Intermediate crystalline fraction and mixed Silk I/Silk II structures were found in films prepared by water annealing at 37 °C. FSC results indicate that Silk II crystals exhibit endotherms of narrower width and have higher mean melting temperature Tm(II) = 351 ± 2.6 °C, compared to Silk I crystals which melt at Tm(I) = 292 ± 3.8 °C. Films containing mixed Silk I/Silk II structure showed two clearly separated endothermic peaks. Evidence suggests that the two types of crystals melt separately and do not thermally interconvert on the extremely short time scale (0.065 s between onset and end of melting) of the FSC experiment.« less

Variation in Protein Intake Induces Variation in Spider Silk Expression

PubMed Central

Blamires, Sean J.; Wu, Chun-Lin; Tso, I-Min

2012-01-01

Background It is energetically expensive to synthesize certain amino acids. The proteins (spidroins) of spider major ampullate (MA) silk, MaSp1 and MaSp2, differ in amino acid composition. Glutamine and proline are prevalent in MaSp2 and are expensive to synthesize. Since most orb web spiders express high proline silk they might preferentially attain the amino acids needed for silk from food and shift toward expressing more MaSp1 in their MA silk when starved. Methodology/Principal Findings We fed three spiders; Argiope aetherea, Cyrtophora moluccensis and Leucauge blanda, high protein, low protein or no protein solutions. A. aetherea and L. blanda MA silks are high in proline, while C. moluccesnsis MA silks are low in proline. After 10 days of feeding we determined the amino acid compositions and mechanical properties of each species' MA silk and compared them between species and treatments with pre-treatment samples, accounting for ancestry. We found that the proline and glutamine of A. aetherea and L. blanda silks were affected by protein intake; significantly decreasing under the low and no protein intake treatments. Glutmaine composition in C. moluccensis silk was likewise affected by protein intake. However, the composition of proline in their MA silk was not significantly affected by protein intake. Conclusions Our results suggest that protein limitation induces a shift toward different silk proteins with lower glutamine and/or proline content. Contradictions to the MaSp model lie in the findings that C. moluccensis MA silks did not experience a significant reduction in proline and A. aetherea did not experience a significant reduction in serine on low/no protein. The mechanical properties of the silks could not be explained by a MaSp1 expressional shift. Factors other than MaSp expression, such as the expression of spidroin-like orthologues, may impact on silk amino acid composition and spinning and glandular processes may impact mechanics. PMID:22363691

Multiscale mechanisms of nutritionally induced property variation in spider silks.

PubMed

Blamires, Sean J; Nobbs, Madeleine; Martens, Penny J; Tso, I-Min; Chuang, Wei-Tsung; Chang, Chung-Kai; Sheu, Hwo-Shuenn

2018-01-01

Variability in spider major ampullate (MA) silk properties at different scales has proven difficult to determine and remains an obstacle to the development of synthetic fibers mimicking MA silk performance. A multitude of techniques may be used to measure multiscale aspects of silk properties. Here we fed five species of Araneoid spider solutions that either contained protein or were protein deprived and performed silk tensile tests, small and wide-angle X-ray scattering (SAXS/WAXS), amino acid composition analyses, and silk gene expression analyses, to resolve persistent questions about how nutrient deprivation induces variations in MA silk mechanical properties across scales. Our analyses found that the properties of each spider's silk varied differently in response to variations in their protein intake. We found changes in the crystalline and non-crystalline nanostructures to play specific roles in inducing the property variations we found. Across treatment MaSp expression patterns differed in each of the five species. We found that in most species MaSp expression and amino acid composition variations did not conform with our predictions based on a traditional MaSp expression model. In general, changes to the silk's alanine and proline compositions influenced the alignment of the proteins within the silk's amorphous region, which influenced silk extensibility and toughness. Variations in structural alignment in the crystalline and non-crystalline regions influenced ultimate strength independent of genetic expression. Our study provides the deepest insights thus far into the mechanisms of how MA silk properties vary from gene expression to nanostructure formations to fiber mechanics. Such knowledge is imperative for promoting the production of synthetic silk fibers.

Effect of polyamines on mechanical and structural properties of Bombyx mori silk.

PubMed

Yerra, Aparna; Mysarla, Danti Kumari; Siripurapu, Prasanthi; Jha, Anjali; Valluri, Satyavathi V; Mamillapalli, Anitha

2017-01-01

Silkworm, Bombyx mori (B. mori) belongs to the Lepidoptera family. The silk produced from this insect, mulberry silk, gained lot of importance as a fabric. Silk is being exploited as a biomaterial due to its surprising strength and biocompatibility. Polyamines (PA) are important cell growth regulators. In the present work the effect of treatment of polyamines, putrescine (Put), spermidine (Spd), and spermine (Spm) on the quantity and quality of silk produced was assessed. Results showed that exogenous feeding of Spd at a concentration of 50 µM increased fiber length significantly. Analysis by Fourier transform infrared (FTIR) on the properties of silk obtained from Spd treated silkworms revealed an increase in percentage of absorption with no difference in peak positions of amide I and amide III groups. Scanning electron microscopy (SEM) revealed an increase in diameter of silk. Further, analysis at molecular level showed an increase in fibroin expression in Spd treated silk glands. However, the Spd treatment showed no significant difference with respect to fibroin to sericin ratio per unit weight of cocoon, silk tenacity, and percent elongation. Thus, the present results show that polyamine treatment would influence silk quality at structural, mechanical, and molecular level in the Bombyx mori, which can be exploited in silk biomaterial production. © 2016 Wiley Periodicals, Inc.

Formation of silk fibroin nanoparticles in water-miscible organic solvent and their characterization

NASA Astrophysics Data System (ADS)

Zhang, Yu-Qing; Shen, Wei-De; Xiang, Ru-Li; Zhuge, Lan-Jian; Gao, Wei-Jian; Wang, Wen-Bao

2007-10-01

When Silk fibre derived from Bombyx mori, a native biopolymer, was dissolved in highly concentrated neutral salts such as CaCl2, the regenerated liquid silk, a gradually degraded peptide mixture of silk fibroin, could be obtained. The silk fibroin nanoparticles were prepared rapidly from the liquid silk by using water-miscible protonic and polar aprotonic organic solvents. The nanoparticles are insoluble but well dispersed and stable in aqueous solution and are globular particles with a range of 35-125 nm in diameter by means of TEM, SEM, AFM and laser sizer. Over one half of the ɛ-amino groups exist around the protein nanoparticles by using a trinitrobenzenesulfonic acid (TNBS) method. Raman spectra shows the tyrosine residues on the surface of the globules are more exposed than those on native silk fibers. The crystalline polymorph and conformation transition of the silk nanoparticles from random-coil and α-helix form (Silk I) into anti-parallel β-sheet form (Silk II) are investigated in detail by using infrared, fluorescence and Raman spectroscopy, DSC, 13C CP-MAS NMR and electron diffraction. X-ray diffraction of the silk nanoparticles shows that the nanoparticles crystallinity is about four fifths of the native fiber. Our results indicate that the degraded peptide chains of the regenerated silk is gathered homogeneously or heterogeneously to form a looser globular structure in aqueous solution. When introduced into excessive organic solvent, the looser globules of the liquid silk are rapidly dispersed and simultaneously dehydrated internally and externally, resulting in the further chain-chain contact, arrangement of those hydrophobic domains inside the globules and final formation of crystalline silk nanoparticles with β-sheet configuration. The morphology and size of the nanoparticles are relative to the kinds, properties and even molecular structures of organic solvents, and more significantly to the looser globular substructure of the degraded silk fibroin in aqueous solution. It is possible that the silk protein nanoparticles are potentially useful in biomaterials such as cosmetics, anti-UV skincare products, industrial materials and surface improving materials, especially in enzyme/drug delivery system as vehicle.

Effect of silk protein surfactant on silk degumming and its properties.

PubMed

Wang, Fei; Cao, Ting-Ting; Zhang, Yu-Qing

2015-10-01

The silk protein surfactant (SPS) first used as a silk degumming agent in this study is an amino acid-type anionic surfactant that was synthesized using silk fibroin amino acids and lauroyl chloride. We studied it systematically in comparison with the traditional degumming methods such as sodium carbonate (Na2CO3) and neutral soap (NS). The experimental results showed that the sericin can be completely removed from the silk fibroin fiber after boiling the fibers three times for 30 min and using a bath ratio of 1:80 (g/mL) and a concentration of 0.2% SPS in an aqueous solution. The results of the tensile properties, thermal analysis, and SEM all show that SPS is similar to the NS, far superior to Na2CO3. In short, SPS may be used as an environmentally friendly silk degumming/refining agent in the silk textile industry and in the manufacture of silk floss quilts. Copyright © 2015 Elsevier B.V. All rights reserved.

Silk protein aggregation kinetics revealed by Rheo-IR.

PubMed

Boulet-Audet, Maxime; Terry, Ann E; Vollrath, Fritz; Holland, Chris

2014-02-01

The remarkable mechanical properties of silk fibres stem from a multi-scale hierarchical structure created when an aqueous protein "melt" is converted to an insoluble solid via flow. To directly relate a silk protein's structure and function in response to flow, we present the first application of a Rheo-IR platform, which couples cone and plate rheology with attenuated total reflectance infrared spectroscopy. This technique provides a new window into silk processing by linking shear thinning to an increase in molecular alignment, with shear thickening affecting changes in the silk protein's secondary structure. Additionally, compared to other static characterization methods for silk, Rheo-IR proved particularly useful at revealing the intrinsic difference between natural (native) and reconstituted silk feedstocks. Hence Rheo-IR offers important novel insights into natural silk processing. This has intrinsic academic merit, but it might also be useful when designing reconstituted silk analogues alongside other polymeric systems, whether natural or synthetic. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Expression of a maize Myb transcription factor driven by a putative silk-specific promoter significantly enhances resistance to Helicoverpa zea in transgenic maize.

PubMed

Johnson, Eric T; Berhow, Mark A; Dowd, Patrick F

2007-04-18

Hi II maize (Zea mays) plants were engineered to express maize p1 cDNA, a Myb transcription factor, controlled by a putative silk specific promoter, for secondary metabolite production and corn earworm resistance. Transgene expression did not enhance silk color, but about half of the transformed plant silks displayed browning when cut, which indicated the presence of p1-produced secondary metabolites. Levels of maysin, a secondary metabolite with insect toxicity, were highest in newly emerged browning silks. The insect resistance of transgenic silks was also highest at emergence, regardless of maysin levels, which suggests that other unidentified p1-induced molecules likely contributed to larval mortality. Mean survivor weights of corn earworm larvae fed mature browning transgenic silks were significantly lower than weights of those fed mature nonbrowning transgenic silks. Some transgenic pericarps browned with drying and contained similar molecules found in pericarps expressing a dominant p1 allele, suggesting that the promoter may not be silk-specific.

Invited review the coiled coil silk of bees, ants, and hornets.

PubMed

Sutherland, Tara D; Weisman, Sarah; Walker, Andrew A; Mudie, Stephen T

2012-06-01

In this article, we review current knowledge about the silk produced by the larvae of bees, ants, and hornets [Apoidea and Vespoidea: Hymenoptera]. Different species use the silk either alone or in composites for a variety of purposes including mechanical reinforcement, thermal regulation, or humidification. The characteristic molecular structure of this silk is α-helical proteins assembled into tetrameric coiled coils. Gene sequences from seven species are available, and each species possesses a copy of each of four related silk genes that encode proteins predicted to form coiled coils. The proteins are ordered at multiple length scales within the labial gland of the final larval instar before spinning. The insects control the morphology of the silk during spinning to produce either fibers or sheets. The silk proteins are small and non repetitive and have been produced artificially at high levels by fermentation in E. coli. The artificial silk proteins can be fabricated into materials with structural and mechanical properties similar to those of native silks. Copyright © 2011 Wiley Periodicals, Inc.

Development of an enzyme-linked-immunosorbent-assay technique for accurate identification of poorly preserved silks unearthed in ancient tombs.

PubMed

Zheng, Qin; Wu, Xiaofeng; Zheng, Hailing; Zhou, Yang

2015-05-01

We report the preparation of a specific fibroin antibody and its use for the identification of unearthed ancient silk relics. Based on the 12-amino-acid repeat sequence "GAGAGSGAGAGS", which is found in fibroin of the silkworm Bombyx mori, a specific antibody against fibroin was prepared in rabbits through peptide synthesis and carrier-protein coupling. This antibody was highly specific for fibroin found in silk. Using this antibody we have successfully identified four silk samples from different time periods. Our results reveal, for the first time, a method capable of detecting silk from a few milligrams of archaeological fabric that has been buried for thousands of years, confirming that the ancient practice of wearing silk products while praying for rebirth dated back to at least 400 BCE. This method also complements current approaches in silk detection, especially for the characterization of poorly preserved silks, promoting the investigation of silk origins and of ancient clothing cultures.

Highly water-absorbing silk yarn with interpenetrating network via in situ polymerization.

PubMed

Lee, Ka I; Wang, Xiaowen; Guo, Xia; Yung, Ka-Fu; Fei, Bin

2017-02-01

Silk was modified via in situ polymerization of two monomers acrylamide and sodium acrylate by swelling in an effective LiBr dissolution system. Swelling of natural silks in LiBr solutions of low concentration was clearly observed under optical microscope, and their conformational changes were revealed by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. Dissolution tests and FTIR spectra of these modified silks suggested the presence of interpenetrating network of polyacrylamide and poly(sodium acrylate) in the silk yarns. These modified silks exhibited superior water absorption to that of raw silk and greatly improved mechanical properties in both dry and wet states. These novel modified silks also showed low cytotoxicity towards skin keratinocytes, having potential applications in biomedical textiles. This modification method by in situ polymerization after swelling in LiBr provides a new route to highly enhance the properties and performance of silk for various applications. Copyright © 2016 Elsevier B.V. All rights reserved.

Comparative transcriptome analyses on silk glands of six silkmoths imply the genetic basis of silk structure and coloration.

PubMed

Dong, Yang; Dai, Fangyin; Ren, Yandong; Liu, Hui; Chen, Lei; Yang, Pengcheng; Liu, Yanqun; Li, Xin; Wang, Wen; Xiang, Hui

2015-03-17

Silk has numerous unique properties that make it a staple of textile manufacturing for several thousand years. However, wider applications of silk in modern have been stalled due to limitations of traditional silk produced by Bombyx mori. While silk is commonly produced by B. mori, several wild non-mulberry silkmoths--especially members of family Saturniidae--produce silk with superior properties that may be useful for wider applications. Further utilization of such silks is hampered by the non-domestication status or limited culturing population of wild silkworms. To date there is insufficient basic genomic or transcriptomic data on these organisms or their silk production. We sequenced and compared the transcriptomes of silk glands of six Saturniidae wild silkmoth species through next-generation sequencing technology, identifying 37758 ~ 51734 silkmoth unigenes, at least 36.3% of which are annotated with an e-value less than 10(-5). Sequence analyses of these unigenes identified a batch of genes specific to Saturniidae that are enriched in growth and development. Analyses of silk proteins including fibroin and sericin indicate intra-genus conservation and inter-genus diversification of silk protein features among the wild silkmoths, e.g., isoelectric points, hydrophilicity profile and amino acid composition in motifs of silk H-fibroin. Interestingly, we identified p25 in two of the silkmoths, which were previously predicted to be absent in Saturniidae. There are rapid evolutionary changes in sericin proteins, which might account for the highly heterogeneity of sericin in Saturniidae silkmoths. Within the six sikmoths, both colored-cocoon silkmoth specific transcripts and differentially expressed genes between the colored-cocoon and non-colored-cocoon silkmoths are significantly enriched in catalytic activity, especially transferase activity, suggesting potentially viable targets for future gene mining or genetic manipulation. Our results characterize novel and potentially valuable gene resources of saturniid silkmoths that may facilitate future genetic improvement and modification of mulberry silkworms. Our results suggest that the disparate features of silk--coloration, retention, strength, etc. --are likely not only due to silk proteins, but also to the environment of silk assembly, and more specifically, that stable silk coloration exhibited by some Saturniidae silkmoths may be attributable to active catalytic progress in pigmentation.

The advances and perspectives of recombinant protein production in the silk gland of silkworm Bombyx mori.

PubMed

Xu, Hanfu

2014-10-01

The silk gland of silkworm Bombyx mori, is one of the most important organs that has been fully studied and utilized so far. It contributes finest silk fibers to humankind. The silk gland has excellent ability of synthesizing silk proteins and is a kind tool to produce some useful recombinant proteins, which can be widely used in the biological, biotechnical and pharmaceutical application fields. It's a very active area to express recombinant proteins using the silk gland as a bioreactor, and great progress has been achieved recently. This review recapitulates the progress of producing recombinant proteins and silk-based biomaterials in the silk gland of silkworm in addition to the construction of expression systems. Current challenges and future trends in the production of valuable recombinant proteins using transgenic silkworms are also discussed.

Lyophilized Silk Fibroin Hydrogels for the Sustained Local Delivery of Therapeutic Monoclonal Antibodies

PubMed Central

Guziewicz, Nicholas; Best, Annie; Perez-Ramirez, Bernardo; Kaplan, David L.

2011-01-01

The development of sustained delivery systems compatible with protein therapeutics continues to be a significant unmet need. A lyophilized silk fibroin hydrogel matrix (lyogel) for the sustained release of pharmaceutically relevant monoclonal antibodies is described. Sonication of silk fibroin prior to antibody incorporation avoids exposing the antibody to the sol-gel transition inducing shear stress. Fourier Transform Infrared (FTIR) analysis showed no change in silk structural composition between hydrogel and lyogel or with increasing silk fibroin concentration. Antibody release from hydrogels occurred rapidly over 10 days regardless of silk concentration. Upon lyophilization, sustained antibody release was observed over 38 days from lyogels containing 6.2% (w/w) silk fibroin and above. In 3.2% (w/w) silk lyogels, antibody release was comparable to hydrogels. Swelling properties of lyogels followed a similar threshold behavior. Lyogels at 3.2% (w/w) silk recovered approximately 90% of their fluid mass upon rehydration, while approximately 50% fluid recovery was observed at 6.2% (w/w) silk and above. Antibody release was primarily governed by hydrophobic/hydrophilic silk-antibody interactions and secondarily altered by the hydration resistance of the lyogel. Hydration resistance was controlled by altering β-sheet (crystalline) density of the matrix. The antibody released from lyogels maintained biological activity. Silk lyogels offer an advantage as a delivery matrix over other hydrogel materials for the slow release of the loaded protein, making lyogels suitable for long-term sustained release applications. PMID:21216004

Controlling silk fibroin particle features for drug delivery

PubMed Central

Lammel, Andreas; Hu, Xiao; Park, Sang-Hyug; Kaplan, David L.; Scheibel, Thomas

2010-01-01

Silk proteins are a promising material for drug delivery due to their aqueous processability, biocompatibility, and biodegradability. A simple aqueous preparation method for silk fibroin particles with controllable size, secondary structure and zeta potential is reported. The particles were produced by salting out a silk fibroin solution with potassium phosphate. The effect of ionic strength and pH of potassium phosphate solution on the yield and morphology of the particles was determined. Secondary structure and zeta potential of the silk particles could be controlled by pH. Particles produced by salting out with 1.25 M potassium phosphate pH 6 showed a dominating silk II (crystalline) structure whereas particles produced at pH 9 were mainly composed of silk I (less crystalline). The results show that silk I rich particles possess chemical and physical stability and secondary structure which remained unchanged during post treatments even upon exposure to 100% ethanol or methanol. A model is presented to explain the process of particle formation based on intra- and intermolecular interactions of the silk domains, influenced by pH and kosmotrope salts. The reported silk fibroin particles can be loaded with small molecule model drugs, such as alcian blue, rhodamine B, and crystal violet, by simple absorption based on electrostatic interactions. In vitro release of these compounds from the silk particles depends on charge – charge interactions between the compounds and the silk. With crystal violet we demonstrated that the release kinetics are dependent on the secondary structure of the particles. PMID:20219241

The influence of specific binding of collagen-silk chimeras to silk biomaterials on hMSC behavior

PubMed Central

An, Bo; DesRochers, Teresa M.; Qin, Guokui; Xia, Xiaoxia; Thiagarajan, Geetha; Brodsky, Barbara; Kaplan, David

2012-01-01

Collagen-like proteins in the bacteria Streptococcus pyogenes adopt a triple-helix structure with a thermal stability similar to that of animal collagens, can be expressed in high yield in E. coli and can be easily modified through molecular biology techniques. However, potential applications for such recombinant collagens are limited by their lack of higher order structure to achieve the physical properties needed for most biomaterials. To overcome this problem, the S. pyrogenes collagen domain was fused to a repetitive Bombyx mori silk consensus sequence, as a strategy to direct specific non-covalent binding onto solid silk materials whose superior stability, mechanical and material properties have been previously established. This approach resulted in the successful binding of these new collagen-silk chimeric proteins to silk films and porous scaffolds, and the binding affinity could be controlled by varying the number of repeats in the silk sequence. To explore the potential of collagen-silk chimera for regulating biological activity, integrin (Int) and fibronectin (Fn) binding sequences from mammalian collagens were introduced into the bacterial collagen domain. The attachment of bioactive collagen-silk chimeras to solid silk biomaterials promoted hMSC spreading and proliferation substantially in comparison to the controls. The ability to combine the biomaterial features of silk with the biological activities of collagen allowed more rapid cell interactions with silk-based biomaterials, improved regulation of stem cell growth and differentiation, as well as the formation of artificial extracellular matrices useful for tissue engineering applications. PMID:23088839

Aqueous multiphoton lithography with multifunctional silk-centred bio-resists.

PubMed

Sun, Yun-Lu; Li, Qi; Sun, Si-Ming; Huang, Jing-Chun; Zheng, Bo-Yuan; Chen, Qi-Dai; Shao, Zheng-Zhong; Sun, Hong-Bo

2015-10-16

Silk and silk fibroin, the biomaterial from nature, nowadays are being widely utilized in many cutting-edge micro/nanodevices/systems via advanced micro/nanofabrication techniques. Herein, for the first time to our knowledge, we report aqueous multiphoton lithography of diversiform-regenerated-silk-fibroin-centric inks using noncontact and maskless femtosecond laser direct writing (FsLDW). Initially, silk fibroin was FsLDW-crosslinked into arbitrary two/three-dimensional micro/nanostructures with good elastic properties merely using proper photosensitizers. More interestingly, silk/metal composite micro/nanodevices with multidimension-controllable metal content can be FsLDW-customized through laser-induced simultaneous fibroin oxidation/crosslinking and metal photoreduction using the simplest silk/Ag(+) or silk/[AuCl4](-) aqueous resists. Noticeably, during FsLDW, fibroin functions as biological reductant and matrix, while metal ions act as the oxidant. A FsLDW-fabricated prototyping silk/Ag microelectrode exhibited 10(4)-Ω(-1 ) m(-1)-scale adjustable electric conductivity. This work not only provides a powerful development to silk micro/nanoprocessing techniques but also creates a novel way to fabricate multifunctional metal/biomacromolecule complex micro/nanodevices for applications such as micro/nanoscale mechanical and electrical bioengineering and biosystems.

Comparative proteomics reveal diverse functions and dynamic changes of Bombyx mori silk proteins spun from different development stages.

PubMed

Dong, Zhaoming; Zhao, Ping; Wang, Chen; Zhang, Yan; Chen, Jianping; Wang, Xin; Lin, Ying; Xia, Qingyou

2013-11-01

Silkworms (Bombyx mori) produce massive amounts of silk proteins to make cocoons during the final stages of larval development. Although the major components, fibroin and sericin, have been the focus for a long time, few researchers have realized the complexity of the silk proteome. We collected seven kinds of silk fibers spun by silkworm larvae at different developmental stages: the silks spun by new hatched larvae, second instar day 0 larvae, third instar day 0 larvae, fourth instar day 0 larvae, and fourth instar molting larvae, the scaffold silk used to attach the cocoon to the substrate and the cocoon silk. Analysis by liquid chromatography-tandem mass spectrometry identified 500 proteins from the seven silks. In addition to the expected fibroins, sericins, and some known protease inhibitors, we also identified further protease inhibitors, enzymes, proteins of unknown function, and other proteins. Unsurprisingly, our quantitative results showed fibroins and sericins were the most abundant proteins in all seven silks. Except for fibroins and sericins, protease inhibitors, enzymes, and proteins of unknown function were more abundant than other proteins. We found significant change in silk protein compositions through development, being consistent with their different biological functions and complicated formation.

Aqueous multiphoton lithography with multifunctional silk-centred bio-resists

PubMed Central

Sun, Yun-Lu; Li, Qi; Sun, Si-Ming; Huang, Jing-Chun; Zheng, Bo-Yuan; Chen, Qi-Dai; Shao, Zheng-Zhong; Sun, Hong-Bo

2015-01-01

Silk and silk fibroin, the biomaterial from nature, nowadays are being widely utilized in many cutting-edge micro/nanodevices/systems via advanced micro/nanofabrication techniques. Herein, for the first time to our knowledge, we report aqueous multiphoton lithography of diversiform-regenerated-silk-fibroin-centric inks using noncontact and maskless femtosecond laser direct writing (FsLDW). Initially, silk fibroin was FsLDW-crosslinked into arbitrary two/three-dimensional micro/nanostructures with good elastic properties merely using proper photosensitizers. More interestingly, silk/metal composite micro/nanodevices with multidimension-controllable metal content can be FsLDW-customized through laser-induced simultaneous fibroin oxidation/crosslinking and metal photoreduction using the simplest silk/Ag+ or silk/[AuCl4]− aqueous resists. Noticeably, during FsLDW, fibroin functions as biological reductant and matrix, while metal ions act as the oxidant. A FsLDW-fabricated prototyping silk/Ag microelectrode exhibited 104-Ω−1 m−1-scale adjustable electric conductivity. This work not only provides a powerful development to silk micro/nanoprocessing techniques but also creates a novel way to fabricate multifunctional metal/biomacromolecule complex micro/nanodevices for applications such as micro/nanoscale mechanical and electrical bioengineering and biosystems. PMID:26472600

A silk-based encapsulation platform for pancreatic islet transplantation improves islet function in vivo.

PubMed

Hamilton, Diana C; Shih, Hank H; Schubert, Richard A; Michie, Sara A; Staats, Paul N; Kaplan, David L; Fontaine, Magali J

2017-03-01

The success of pancreatic islet (PI) transplantation is challenged by PI functional damage during the peritransplantation period. A silk-based encapsulation platform including mesenchymal stromal cells (MSCs) was evaluated for islet cell delivery in vivo. Islet equivalents (IEQs) were transplanted into the epididymal fat pads of mice with streptozotocin-induced diabetes. Three PI combinations were tested: (A) co-encapsulated in silk with MSCs; (b) encapsulated in silk alone; or (c) pelleted. Blood glucose levels were monitored and intraperitoneal glucose tolerance test (IPGTT) was performed upon return to euglycaemia. Grafts were removed for histology and cytokine content analysis. Mice with PI grafts in silk showed a prompt return to euglycaemia. IPGTT was significantly improved with PI in silk with MSCs, compared to PI in silk alone or pelleted. Both Th 1 and Th 2 cytokines were increased in PI grafts in silk, but Th 1 cytokines were decreased significantly with PI and MSC co-encapsulation. Histological analysis showed osteogenesis and chondrogenesis in the silk grafts containing MSCs. Future studies will evaluate MSC stability and function in vivo and improve silk biocompatibility for applications in islet transplantation. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

Metal nanoparticles triggered persistent negative photoconductivity in silk protein hydrogels

NASA Astrophysics Data System (ADS)

Gogurla, Narendar; Sinha, Arun K.; Naskar, Deboki; Kundu, Subhas C.; Ray, Samit K.

2016-03-01

Silk protein is a natural biopolymer with intriguing properties, which are attractive for next generation bio-integrated electronic and photonic devices. Here, we demonstrate the negative photoconductive response of Bombyx mori silk protein fibroin hydrogels, triggered by Au nanoparticles. The room temperature electrical conductivity of Au-silk hydrogels is found to be enhanced with the incorporation of Au nanoparticles over the control sample, due to the increased charge transporting networks within the hydrogel. Au-silk lateral photoconductor devices show a unique negative photoconductive response under an illumination of 325 nm, with excitation energy higher than the characteristic metal plasmon resonance band. The enhanced photoconductance yield in the hydrogels over the silk protein is attributed to the photo-oxidation of amino groups in the β-pleated sheets of the silk around the Au nanoparticles followed by the breaking of charge transport networks. The Au-silk nanocomposite does not show any photoresponse under visible illumination because of the localization of excited charges in Au nanoparticles. The negative photoconductive response of hybrid Au-silk under UV illumination may pave the way towards the utilization of silk for future bio-photonic devices using metal nanoparticle platforms.

Aqueous multiphoton lithography with multifunctional silk-centred bio-resists

NASA Astrophysics Data System (ADS)

Sun, Yun-Lu; Li, Qi; Sun, Si-Ming; Huang, Jing-Chun; Zheng, Bo-Yuan; Chen, Qi-Dai; Shao, Zheng-Zhong; Sun, Hong-Bo

2015-10-01

Silk and silk fibroin, the biomaterial from nature, nowadays are being widely utilized in many cutting-edge micro/nanodevices/systems via advanced micro/nanofabrication techniques. Herein, for the first time to our knowledge, we report aqueous multiphoton lithography of diversiform-regenerated-silk-fibroin-centric inks using noncontact and maskless femtosecond laser direct writing (FsLDW). Initially, silk fibroin was FsLDW-crosslinked into arbitrary two/three-dimensional micro/nanostructures with good elastic properties merely using proper photosensitizers. More interestingly, silk/metal composite micro/nanodevices with multidimension-controllable metal content can be FsLDW-customized through laser-induced simultaneous fibroin oxidation/crosslinking and metal photoreduction using the simplest silk/Ag+ or silk/[AuCl4]- aqueous resists. Noticeably, during FsLDW, fibroin functions as biological reductant and matrix, while metal ions act as the oxidant. A FsLDW-fabricated prototyping silk/Ag microelectrode exhibited 104-Ω-1 m-1-scale adjustable electric conductivity. This work not only provides a powerful development to silk micro/nanoprocessing techniques but also creates a novel way to fabricate multifunctional metal/biomacromolecule complex micro/nanodevices for applications such as micro/nanoscale mechanical and electrical bioengineering and biosystems.

Silkworm silk-based materials and devices generated using bio-nanotechnology.

PubMed

Huang, Wenwen; Ling, Shengjie; Li, Chunmei; Omenetto, Fiorenzo G; Kaplan, David L

2018-06-25

Silks are natural fibrous protein polymers that are spun by silkworms and spiders. Among silk variants, there has been increasing interest devoted to the silkworm silk of B. mori, due to its availability in large quantities along with its unique material properties. Silk fibroin can be extracted from the cocoons of the B. mori silkworm and combined synergistically with other biomaterials to form biopolymer composites. With the development of recombinant DNA technology, silks can also be rationally designed and synthesized via genetic control. Silk proteins can be processed in aqueous environments into various material formats including films, sponges, electrospun mats and hydrogels. The versatility and sustainability of silk-based materials provides an impressive toolbox for tailoring materials to meet specific applications via eco-friendly approaches. Historically, silkworm silk has been used by the textile industry for thousands of years due to its excellent physical properties, such as lightweight, high mechanical strength, flexibility, and luster. Recently, due to these properties, along with its biocompatibility, biodegradability and non-immunogenicity, silkworm silk has become a candidate for biomedical utility. Further, the FDA has approved silk medical devices for sutures and as a support structure during reconstructive surgery. With increasing needs for implantable and degradable devices, silkworm silk has attracted interest for electronics, photonics for implantable yet degradable medical devices, along with a broader range of utility in different device applications. This Tutorial review summarizes and highlights recent advances in the use of silk-based materials in bio-nanotechnology, with a focus on the fabrication and functionalization methods for in vitro and in vivo applications in the field of tissue engineering, degradable devices and controlled release systems.

MicroRNA profile of silk gland reveals different silk yields of three silkworm strains.

PubMed

Qin, Sheng; Danso, Blessing; Zhang, Jing; Li, Juan; Liu, Na; Sun, Xia; Hou, Chengxiang; Luo, Heng; Chen, Keping; Zhang, Guozheng; Li, Muwang

2018-05-05

Silk proteins are synthesized and secreted by the silk gland. The differential gene expression in it leads to different silk yield among various silkworm strains. As crucial factors, microRNAs (miRNAs) regulate protein synthesis at post-transcriptional level in silk gland. MiRNAs expression level in the silk gland of three silkworm strains (Jingsong, Lan10 and Dazao) was analyzed and 33 differentially expressed miRNAs (DEMs) were discovered between JingSong (JS) and Lan10 (L10), 60 DEMs between JS and Dazao, 54 DEMs between L10 and Dazao respectively. The DEMs target genes were predicted combing with two different methods and their functions were annotated according to gene ontology. Our previous studies showed that a batch of genes related to silk yield were identified in JS and L10 strains by comparative transcriptome and quantitative trait loci (QTL) method. Thirteen DEMs whose target genes are related to protein biosynthesis processes were screened by combining with these researches. Twelve DEMs potentially regulate nineteen genes which exist in our QTL results. Six common DEMs potentially regulate the genes in both of previous results. Finally, five DEMs were selected to verify their expression levels between JS and L10 by qRT-PCR, which showed similar difference as the results of small RNA-sequencing. MiRNAs in the silk gland may directly affect silk protein biosynthesis in different silkworm strains. In current work, we identified a batch of DEMs which potentially regulate the genes related to silk yield. Further functionally study of these miRNAs will contribute to improve varieties and boost the silk yield. Our research provides a basis for studying these miRNAs and their functions in silk production. Copyright © 2018 Elsevier B.V. All rights reserved.

Recombinant DNA production of spider silk proteins.

PubMed

Tokareva, Olena; Michalczechen-Lacerda, Valquíria A; Rech, Elíbio L; Kaplan, David L

2013-11-01

Spider dragline silk is considered to be the toughest biopolymer on Earth due to an extraordinary combination of strength and elasticity. Moreover, silks are biocompatible and biodegradable protein-based materials. Recent advances in genetic engineering make it possible to produce recombinant silks in heterologous hosts, opening up opportunities for large-scale production of recombinant silks for various biomedical and material science applications. We review the current strategies to produce recombinant spider silks. © 2013 The Authors. Microbial Biotechnology published by John Wiley & Sons Ltd and Society for Applied Microbiology.

Silk Gland Gene Expression during Larval-Pupal Transition in the Cotton Leaf Roller Sylepta derogata (Lepidoptera: Pyralidae)

PubMed Central

Su, Honghua; Cheng, Yuming; Wang, Zhongyang; Li, Zhong; Stanley, David; Yang, Yizhong

2015-01-01

The cotton leaf roller, Sylepta derogata, is a silk-producing insect pest. While young larvae feed on the underside of leaves, the older ones roll cotton leaves and feed on the leaf edges, which defoliates cotton plants. The larvae produce silk to stabilize the rolled leaf and to balloon from used to new leaves. Despite the significance of silk in the biology of pest insect species, there is virtually no information on the genes involved in their silk production. This is a substantial knowledge gap because some of these genes may be valuable targets for developing molecular pest management technologies. We addressed the gap by posing the hypothesis that silk gland gene expression changes during the transition from larvae to pupae. We tested our hypothesis using RNA-seq to investigate changes in silk gland gene expression at three developmental stages, 5th instar larvae (silk producing; 15,445,926 clean reads), prepupae (reduced silk producing; 13,758,154) and pupae (beyond silk producing; 16,787,792). We recorded 60,298 unigenes and mapped 50,158 (larvae), 48,415 (prepupae) and 46,623 (pupae) of them to the NCBI database. Most differentially expressed genes in the 5th instar larvae/prepupae libraries were relevant to nucleotide synthesis and maintenance of silk gland function. We identified down-regulated transcriptional factors and several genes involved in silk formation in the three libraries and verified the expression pattern of eight genes by qPCR. The developmental- and tissue-specific expression patterns of the fibroin light chain gene showed it was highly expressed during the larval silk-producing stage. We recorded highest expression of this gene in the larval silk gland, compared to other tissues, including midgut, hindgut, epidermis, Malpighian tubes, hemolymph and fat body. These data are a genetic resource to guide selection of key genes that may be targeted for in planta and other gene-silencing technologies for sustainable cotton agriculture. PMID:26352931

Silk Gland Gene Expression during Larval-Pupal Transition in the Cotton Leaf Roller Sylepta derogata (Lepidoptera: Pyralidae).

PubMed

Su, Honghua; Cheng, Yuming; Wang, Zhongyang; Li, Zhong; Stanley, David; Yang, Yizhong

2015-01-01

The cotton leaf roller, Sylepta derogata, is a silk-producing insect pest. While young larvae feed on the underside of leaves, the older ones roll cotton leaves and feed on the leaf edges, which defoliates cotton plants. The larvae produce silk to stabilize the rolled leaf and to balloon from used to new leaves. Despite the significance of silk in the biology of pest insect species, there is virtually no information on the genes involved in their silk production. This is a substantial knowledge gap because some of these genes may be valuable targets for developing molecular pest management technologies. We addressed the gap by posing the hypothesis that silk gland gene expression changes during the transition from larvae to pupae. We tested our hypothesis using RNA-seq to investigate changes in silk gland gene expression at three developmental stages, 5th instar larvae (silk producing; 15,445,926 clean reads), prepupae (reduced silk producing; 13,758,154) and pupae (beyond silk producing; 16,787,792). We recorded 60,298 unigenes and mapped 50,158 (larvae), 48,415 (prepupae) and 46,623 (pupae) of them to the NCBI database. Most differentially expressed genes in the 5th instar larvae/prepupae libraries were relevant to nucleotide synthesis and maintenance of silk gland function. We identified down-regulated transcriptional factors and several genes involved in silk formation in the three libraries and verified the expression pattern of eight genes by qPCR. The developmental- and tissue-specific expression patterns of the fibroin light chain gene showed it was highly expressed during the larval silk-producing stage. We recorded highest expression of this gene in the larval silk gland, compared to other tissues, including midgut, hindgut, epidermis, Malpighian tubes, hemolymph and fat body. These data are a genetic resource to guide selection of key genes that may be targeted for in planta and other gene-silencing technologies for sustainable cotton agriculture.

Structural and optical studies on selected web spinning spider silks

NASA Astrophysics Data System (ADS)

Karthikeyani, R.; Divya, A.; Mathavan, T.; Asath, R. Mohamed; Benial, A. Milton Franklin; Muthuchelian, K.

2017-01-01

This study investigates the structural and optical properties in the cribellate silk of the sheet web spider Stegodyphus sarasinorum Karsch (Eresidae) and the combined dragline, viscid silk of the orb-web spiders Argiope pulchella Thorell (Araneidae) and Nephila pilipes Fabricius (Nephilidae). X-ray diffraction (XRD), Fourier transform infra-red (FTIR), Ultraviolet-visible (UV-Vis) and fluorescence spectroscopic techniques were used to study these three spider silk species. X-ray diffraction data are consistent with the amorphous polymer network which is arising from the interaction of larger side chain amino acid contributions due to the poly-glycine rich sequences known to be present in the proteins of cribellate silk. The same amorphous polymer networks have been determined from the combined dragline and viscid silk of orb-web spiders. From FTIR spectra the results demonstrate that, cribellate silk of Stegodyphus sarasinorum, combined dragline viscid silk of Argiope pulchella and Nephila pilipes spider silks are showing protein peaks in the amide I, II and III regions. Further they proved that the functional groups present in the protein moieties are attributed to α-helical and side chain amino acid contributions. The optical properties of the obtained spider silks such as extinction coefficients, refractive index, real and imaginary dielectric constants and optical conductance were studied extensively from UV-Vis analysis. The important fluorescent amino acid tyrosine is present in the protein folding was investigated by using fluorescence spectroscopy. This research would explore the protein moieties present in the spider silks which were found to be associated with α-helix and side chain amino acid contributions than with β-sheet secondary structure and also the optical relationship between the three different spider silks are investigated. Successful spectroscopic knowledge of the internal protein structure and optical properties of the spider silks could permit industrial production of silk-based fibres with unique properties under benign conditions.

Duplication and concerted evolution of MiSp-encoding genes underlie the material properties of minor ampullate silks of cobweb weaving spiders.

PubMed

Vienneau-Hathaway, Jannelle M; Brassfield, Elizabeth R; Lane, Amanda Kelly; Collin, Matthew A; Correa-Garhwal, Sandra M; Clarke, Thomas H; Schwager, Evelyn E; Garb, Jessica E; Hayashi, Cheryl Y; Ayoub, Nadia A

2017-03-14

Orb-web weaving spiders and their relatives use multiple types of task-specific silks. The majority of spider silk studies have focused on the ultra-tough dragline silk synthesized in major ampullate glands, but other silk types have impressive material properties. For instance, minor ampullate silks of orb-web weaving spiders are as tough as draglines, due to their higher extensibility despite lower strength. Differences in material properties between silk types result from differences in their component proteins, particularly members of the spidroin (spider fibroin) gene family. However, the extent to which variation in material properties within a single silk type can be explained by variation in spidroin sequences is unknown. Here, we compare the minor ampullate spidroins (MiSp) of orb-weavers and cobweb weavers. Orb-web weavers use minor ampullate silk to form the auxiliary spiral of the orb-web while cobweb weavers use it to wrap prey, suggesting that selection pressures on minor ampullate spidroins (MiSp) may differ between the two groups. We report complete or nearly complete MiSp sequences from five cobweb weaving spider species and measure material properties of minor ampullate silks in a subset of these species. We also compare MiSp sequences and silk properties of our cobweb weavers to published data for orb-web weavers. We demonstrate that all our cobweb weavers possess multiple MiSp loci and that one locus is more highly expressed in at least two species. We also find that the proportion of β-spiral-forming amino acid motifs in MiSp positively correlates with minor ampullate silk extensibility across orb-web and cobweb weavers. MiSp sequences vary dramatically within and among spider species, and have likely been subject to multiple rounds of gene duplication and concerted evolution, which have contributed to the diverse material properties of minor ampullate silks. Our sequences also provide templates for recombinant silk proteins with tailored properties.

Use of the Stable Nitrogen Isotope to Reveal the Source-Sink Regulation of Nitrogen Uptake and Remobilization during Grain Filling Phase in Maize

PubMed Central

Yang, Lan; Guo, Song; Chen, Qinwu; Chen, Fanjun; Yuan, Lixing; Mi, Guohua

2016-01-01

Although the remobilization of vegetative nitrogen (N) and post-silking N both contribute to grain N in maize (Zea mays L.), their regulation by grain sink strength is poorly understood. Here we use 15N labeling to analyze the dynamic behaviors of both pre- and post-silking N in relation to source and sink manipulation in maize plants. The results showed that the remobilization of pre-silking N started immediately after silking and the remobilized pre-silking N had a greater contribution to grain N during early grain filling, with post-silking N importance increasing during the later filling stage. The amount of post-silking N uptake was largely driven by post-silking dry matter accumulation in both grain as well as vegetative organs. Prevention of pollination during silking had less effect on post-silking N uptake, as a consequence of compensatory growth of stems, husk + cob and roots. Also, leaves continuously export N even though grain sink was removed. The remobilization efficiency of N in the leaf and stem increased with increasing grain yield (hence N requirement). It is suggested that the remobilization of N in the leaf is controlled by sink strength but not the leaf per se. Enhancing post-silking N uptake rather than N remobilization is more likely to increase grain N accumulation. PMID:27606628

Lyophilized Silk Sponges: A Versatile Biomaterial Platform for Soft Tissue Engineering

PubMed Central

2015-01-01

We present a silk biomaterial platform with highly tunable mechanical and degradation properties for engineering and regeneration of soft tissues such as, skin, adipose, and neural tissue, with elasticity properties in the kilopascal range. Lyophilized silk sponges were prepared under different process conditions and the effect of silk molecular weight, concentration and crystallinity on 3D scaffold formation, structural integrity, morphology, mechanical and degradation properties, and cell interactions in vitro and in vivo were studied. Tuning the molecular weight distribution (via degumming time) of silk allowed the formation of stable, highly porous, 3D scaffolds that held form with silk concentrations as low as 0.5% wt/v. Mechanical properties were a function of silk concentration and scaffold degradation was driven by beta-sheet content. Lyophilized silk sponges supported the adhesion of mesenchymal stem cells throughout 3D scaffolds, cell proliferation in vitro, and cell infiltration and scaffold remodeling when implanted subcutaneously in vivo. PMID:25984573

Engineering aqueous fiber assembly into silk-elastin-like protein polymers.

PubMed

Zeng, Like; Jiang, Linan; Teng, Weibing; Cappello, Joseph; Zohar, Yitshak; Wu, Xiaoyi

2014-07-01

Self-assembled peptide/protein nanofibers are valuable 1D building blocks for creating complex structures with designed properties and functions. It is reported that the self-assembly of silk-elastin-like protein polymers into nanofibers or globular aggregates in aqueous solutions can be modulated by tuning the temperature of the protein solutions, the size of the silk blocks, and the charge of the elastin blocks. A core-sheath model is proposed for nanofiber formation, with the silk blocks in the cores and the hydrated elastin blocks in the sheaths. The folding of the silk blocks into stable cores--affected by the size of the silk blocks and the charge of the elastin blocks--plays a critical role in the assembly of silk-elastin nanofibers. Furthermore, enhanced hydrophobic interactions between the elastin blocks at elevated temperatures greatly influence the nanoscale features of silk-elastin nanofibers. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mechanical Properties of Transgenic Silkworm Silk Under High Strain Rate Tensile Loading

NASA Astrophysics Data System (ADS)

Chu, J.-M.; Claus, B.; Chen, W.

2017-12-01

Studies have shown that transgenic silkworm silk may be capable of having similar properties of spider silk while being mass-producible. In this research, the tensile stress-strain response of transgenic silkworm silk fiber is systematically characterized using a quasi-static load frame and a tension Kolsky bar over a range of strain-rates between 10^{-3} and 700/s. The results show that transgenic silkworm silk tends to have higher overall ultimate stress and failure strain at high strain rate (700/s) compared to quasi-static strain rates, indicating rate sensitivity of the material. The failure strain at the high strain rate is higher than that of spider silk. However, the stress levels are significantly below that of spider silk, and far below that of high-performance fiber. Failure surfaces are examined via scanning electron microscopy and reveal that the failure modes are similar to those of spider silk.

The processing and heterostructuring of silk with light

NASA Astrophysics Data System (ADS)

Sidhu, Mehra S.; Kumar, Bhupesh; Singh, Kamal P.

2017-09-01

Spider silk is a tough, elastic and lightweight biomaterial, although there is a lack of tools available for non-invasive processing of silk structures. Here we show that nonlinear multiphoton interactions of silk with few-cycle femtosecond pulses allow the processing and heterostructuring of the material in ambient air. Two qualitatively different responses, bulging by multiphoton absorption and plasma-assisted ablation, are observed for low- and high-peak intensities, respectively. Plasma ablation allows us to make localized nanocuts, microrods, nanotips and periodic patterns with minimal damage while preserving molecular structure. The bulging regime facilitates confined bending and microwelding of silk with materials such as metal, glass and Kevlar with strengths comparable to pristine silk. Moreover, analysis of Raman bands of microwelded joints reveals that the polypeptide backbone remains intact while perturbing its weak hydrogen bonds. Using this approach, we fabricate silk-based functional topological microstructures, such as Mobiüs strips, chiral helices and silk-based sensors.

The processing and heterostructuring of silk with light.

PubMed

Sidhu, Mehra S; Kumar, Bhupesh; Singh, Kamal P

2017-09-01

Spider silk is a tough, elastic and lightweight biomaterial, although there is a lack of tools available for non-invasive processing of silk structures. Here we show that nonlinear multiphoton interactions of silk with few-cycle femtosecond pulses allow the processing and heterostructuring of the material in ambient air. Two qualitatively different responses, bulging by multiphoton absorption and plasma-assisted ablation, are observed for low- and high-peak intensities, respectively. Plasma ablation allows us to make localized nanocuts, microrods, nanotips and periodic patterns with minimal damage while preserving molecular structure. The bulging regime facilitates confined bending and microwelding of silk with materials such as metal, glass and Kevlar with strengths comparable to pristine silk. Moreover, analysis of Raman bands of microwelded joints reveals that the polypeptide backbone remains intact while perturbing its weak hydrogen bonds. Using this approach, we fabricate silk-based functional topological microstructures, such as Mobiüs strips, chiral helices and silk-based sensors.

Thermal crystallization mechanism of silk fibroin protein

NASA Astrophysics Data System (ADS)

Hu, Xiao

In this thesis, the thermal crystallization mechanism of silk fibroin protein from Bombyx mori silkworm, was treated as a model for the general study of protein based materials, combining theories from both biophysics and polymer physics fields. A systematic and scientific path way to model the dynamic beta-sheet crystallization process of silk fibroin protein was presented in the following sequence: (1) The crystallinity, fractions of secondary structures, and phase compositions in silk fibroin proteins at any transition stage were determined. Two experimental methods, Fourier transform infrared spectroscopy (FTIR) with Fourier self-deconvolution, and specific reversing heat capacity, were used together for the first time for modeling the static structures and phases in the silk fibroin proteins. The protein secondary structure fractions during the crystallization were quantitatively determined. The possibility of existence of a "rigid amorphous phase" in silk protein was also discussed. (2) The function of bound water during the crystallization process of silk fibroin was studied using heat capacity, and used to build a silk-water dynamic crystallization model. The fundamental concepts and thermal properties of silk fibroin with/without bound water were discussed. Results show that intermolecular bound water molecules, acting as a plasticizer, will cause silk to display a water-induced glass transition around 80°C. During heating, water is lost, and the change of the microenvironment in the silk fibroin chains induces a mesophase prior to thermal crystallization. Real time FTIR during heating and isothermal holding above Tg show the tyrosine side chain changes only during the former process, while beta sheet crystallization occurs only during the latter process. Analogy is made between the crystallization of synthetic polymers according to the four-state scheme of Strobl, and the crystallization process of silk fibroin, which includes an intermediate precursor stage before crystallization. (3) The beta-sheet crystallization kinetics in silk fibroin protein were measured using X-ray, FTIR and heat flow, and the structure reveals the formation mechanism of the silk crystal network. Avrami kinetics theories, which were established for studies of synthetic polymer crystal growth, were for the first time extended to investigate protein self-assembly in multiblock silk fibroin samples. The Avrami exponent, n, was close to two for all methods, indicating formation of beta sheet crystals in silk proteins is different from the 3-D spherulitic crystal growth found in most synthetic homopolymers. A microphase separation pattern after chymotrypsin enzyme biodegradation was shown in the protein structures using scanning electron microscopy. A model was then used to explain the crystallization of silk fibroin protein by analogy to block copolymers. (4) The effects of metal ions during the crystallization of silk fibroin was investigated using thermal analysis. Advanced thermal analysis methods were used to analyze the thermal protein-metallic ion interactions in silk fibroin proteins. Results show that K+ and Ca2+ metallic salts play different roles in silk fibroin proteins, which either reduce (K+) or increase (Ca2+ ) the glass transition (Tg) of pure silk protein and affect the thermal stability of this structure.

Rapid Characterization of Spider Silk Genes via Exon Capture

DTIC Science & Technology

2015-03-28

SECURITY CLASSIFICATION OF: Spider silks are high-performance materials with an array of potential military and civilian applications. As such, there...is persistent demand for the mass production of silks, which requires knowledge of the underlying silk gene sequences. Spidroins ( spider fibroins...2015 1-May-2014 31-Jan-2015 Approved for Public Release; Distribution Unlimited Final Report: Rapid Characterization of Spider Silk Genes via Exon

Surface modification of silk fibroin fabric using layer-by-layer polyelectrolyte deposition and heparin immobilization for small-diameter vascular prostheses.

PubMed

Elahi, M Fazley; Guan, Guoping; Wang, Lu; Zhao, Xinzhe; Wang, Fujun; King, Martin W

2015-03-03

There is an urgent need to develop a biologically active implantable small-diameter vascular prosthesis with long-term patency. Silk-fibroin-based small-diameter vascular prosthesis is a promising candidate having higher patency rate; however, the surface modification is indeed required to improve its further hemocompatibility. In this study, silk fibroin fabric was modified by a two-stage process. First, the surface of silk fibroin fabric was coated using a layer-by-layer polyelectrolyte deposition technique by stepwise dipping the silk fibroin fabric into a solution of cationic poly(allylamine hydrochloride) (PAH) and anionic poly(acrylic acid) (PAA) solution. The dipping procedure was repeated to obtain the PAH/PAA multilayers deposited on the silk fibroin fabrics. Second, the polyelectrolyte-deposited silk fibroin fabrics were treated in EDC/NHS-activated low-molecular-weight heparin (LMWH) solution at 4 °C for 24 h, resulting in immobilization of LMWH on the silk fibroin fabrics surface. Scanning electron microscopy, atomic force microscopy, and energy-dispersive X-ray data revealed the accomplishment of LMWH immobilization on the polyelectrolyte-deposited silk fibroin fabric surface. The higher the number of PAH/PAA coating layers on the silk fibroin fabric, the more surface hydrophilicity could be obtained, resulting in a higher fetal bovine serum protein and platelets adhesion resistance properties when tested in vitro. In addition, compared with untreated sample, the surface-modified silk fibroin fabrics showed negligible loss of bursting strength and thus reveal the acceptability of polyelectrolytes deposition and heparin immobilization approach for silk-fibroin-based small-diameter vascular prostheses modification.

Web building and silk properties functionally covary among species of wolf spider.

PubMed

Lacava, Mariángeles; Camargo, Arley; Garcia, Luis F; Benamú, Marco A; Santana, Martin; Fang, Jian; Wang, Xungai; Blamires, Sean J

2018-04-15

Although phylogenetic studies have shown covariation between the properties of spider major ampullate (MA) silk and web building, both spider webs and silks are highly plastic so we cannot be sure whether these traits functionally covary or just vary across environments that the spiders occupy. As MaSp2-like proteins provide MA silk with greater extensibility, their presence is considered necessary for spider webs to effectively capture prey. Wolf spiders (Lycosidae) are predominantly non-web building, but a select few species build webs. We accordingly collected MA silk from two web-building and six non-web-building species found in semirural ecosystems in Uruguay to test whether the presence of MaSp2-like proteins (indicated by amino acid composition, silk mechanical properties and silk nanostructures) was associated with web building across the group. The web-building and non-web-building species were from disparate subfamilies so we estimated a genetic phylogeny to perform appropriate comparisons. For all of the properties measured, we found differences between web-building and non-web-building species. A phylogenetic regression model confirmed that web building and not phylogenetic inertia influences silk properties. Our study definitively showed an ecological influence over spider silk properties. We expect that the presence of the MaSp2-like proteins and the subsequent nanostructures improves the mechanical performance of silks within the webs. Our study furthers our understanding of spider web and silk co-evolution and the ecological implications of spider silk properties. © 2018 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2018 European Society For Evolutionary Biology.

Silk fibroin/chitosan thin film promotes osteogenic and adipogenic differentiation of rat bone marrow-derived mesenchymal stem cells.

PubMed

Li, Da-Wei; He, Jin; He, Feng-Li; Liu, Ya-Li; Liu, Yang-Yang; Ye, Ya-Jing; Deng, Xudong; Yin, Da-Chuan

2018-04-01

As a biodegradable polymer thin film, silk fibroin/chitosan composite film overcomes the defects of pure silk fibroin and chitosan films, respectively, and shows remarkable biocompatibility, appropriate hydrophilicity and mechanical properties. Silk fibroin/chitosan thin film can be used not only as metal implant coating for bone injury repair, but also as tissue engineering scaffold for skin, cornea, adipose, and other soft tissue injury repair. However, the biocompatibility of silk fibroin/chitosan thin film for mesenchymal stem cells, a kind of important seed cell of tissue engineering and regenerative medicine, is rarely reported. In this study, silk fibroin/chitosan film was prepared by solvent casting method, and the rat bone marrow-derived mesenchymal stem cells were cultured on the silk fibroin/chitosan thin film. Osteogenic and adipogenic differentiation of rat bone marrow-derived mesenchymal stem cells were induced, respectively. The proliferation ability, osteogenic and adipogenic differentiation abilities of rat bone marrow-derived mesenchymal stem cells were systematically compared between silk fibroin/chitosan thin film and polystyrene tissue culture plates. The results showed that silk fibroin/chitosan thin film not only provided a comparable environment for the growth and proliferation of rat bone marrow-derived mesenchymal stem cells but also promoted their osteogenic and adipogenic differentiation. This work provided information of rat bone marrow-derived mesenchymal stem cells behavior on silk fibroin/chitosan thin film and extended the application of silk fibroin/chitosan thin film. Based on the results, we suggested that the silk fibroin/chitosan thin film could be a promising material for tissue engineering of bone, cartilage, adipose, and skin.

The influence of specific binding of collagen-silk chimeras to silk biomaterials on hMSC behavior.

PubMed

An, Bo; DesRochers, Teresa M; Qin, Guokui; Xia, Xiaoxia; Thiagarajan, Geetha; Brodsky, Barbara; Kaplan, David L

2013-01-01

Collagen-like proteins in the bacteria Streptococcus pyogenes adopt a triple-helix structure with a thermal stability similar to that of animal collagens, can be expressed in high yield in Escherichia coli and can be easily modified through molecular biology techniques. However, potential applications for such recombinant collagens are limited by their lack of higher order structure to achieve the physical properties needed for most biomaterials. To overcome this problem, the S. pyogenes collagen domain was fused to a repetitive Bombyx mori silk consensus sequence, as a strategy to direct specific non-covalent binding onto solid silk materials whose superior stability, mechanical and material properties have been previously established. This approach resulted in the successful binding of these new collagen-silk chimeric proteins to silk films and porous scaffolds, and the binding affinity could be controlled by varying the number of repeats in the silk sequence. To explore the potential of collagen-silk chimera for regulating biological activity, integrin (Int) and fibronectin (Fn) binding sequences from mammalian collagens were introduced into the bacterial collagen domain. The attachment of bioactive collagen-silk chimeras to solid silk biomaterials promoted hMSC spreading and proliferation substantially in comparison to the controls. The ability to combine the biomaterial features of silk with the biological activities of collagen allowed more rapid cell interactions with silk-based biomaterials, improved regulation of stem cell growth and differentiation, as well as the formation of artificial extracellular matrices useful for tissue engineering applications. Copyright © 2012 Elsevier Ltd. All rights reserved.

Concentration state dependence of the rheological and structural properties of reconstituted silk.

PubMed

Mo, Chunli; Holland, Chris; Porter, David; Shao, Zhengzhong; Vollrath, Fritz

2009-10-12

The ability to control the processing of artificial silk is key to the successful application of this important and high performance biopolymer. Understanding where our current reconstitution process can be improved will not only aid us in the creation of better materials, but will also provide insight into the natural material along the way. This study aims to understand what proportion of reconstituted silk contributes to its rheological properties and what conformational state the silk proteins are in. It shows, for the first time, that a change in rheological properties can be related to a change in silk structures present in solution and reveals a low concentration gel state for silk that may have important implications for future successful artificial processing of silk.

Regenerated silk materials for functionalized silk orthopedic devices by mimicking natural processing

PubMed Central

Li, Chunmei; Hotz, Blake; Ling, Shengjie; Guo, Jin; Haas, Dylan S.; Marelli, Benedetto; Omenetto, Fiorenzo; Lin, Samuel J.; Kaplan, David L.

2016-01-01

Silk fibers spun by silkworms and spiders exhibit exceptional mechanical properties with a unique combination of strength, extensibility and toughness. In contrast, the mechanical properties of regenerated silk materials can be tuned through control of the fabrication process. Here we introduce a biomimetic, all-aqueous process, to obtain bulk regenerated silk-based materials for the fabrication of functionalized orthopedic devices. The silk materials generated in the process replicate the nano-scale structure of natural silk fibers and possess excellent mechanical properties. The biomimetic materials demonstrated excellent machinability, providing a path towards the fabrication of a new family of resorbable orthopedic devices where organic solvents are avoided, thus allowing functionalization with bioactive molecules to promote bone remodeling and integration. PMID:27697669

Protein composition correlates with the mechanical properties of spider ( Argiope trifasciata ) dragline silk.

PubMed

Marhabaie, Mohammad; Leeper, Thomas C; Blackledge, Todd A

2014-01-13

We investigated the natural variation in silk composition and mechanical performance of the orb-weaving spider Argiope trifasciata at multiple spatial and temporal scales in order to assess how protein composition contributes to the remarkable material properties of spider dragline silk. Major ampullate silk in orb-weaving spiders consists predominantly of two proteins (MaSp1 and MaSp2) with divergent amino acid compositions and functionally different microstructures. Adjusting the expression of these two proteins therefore provides spiders with a simple mechanism to alter the material properties of their silk. We first assessed the reliability and precision of the Waters AccQ-Tag amino acid composition analysis kit for determining the amino acid composition of small quantities of spider silk. We then tested how protein composition varied within single draglines, across draglines spun by the same spider on different days, and finally between spiders. Then, we correlated chemical composition with the material properties of dragline silk. Overall, we found that the chemical composition of major ampullate silk was in general homogeneous among individuals of the same population. Variation in chemical composition was not detectable within silk spun by a single spider on a single day. However, we found that variation within a single spider's silk across different days could, in rare instances, be greater than variation among individual spiders. Most of the variation in silk composition in our investigation resulted from a small number of outliers (three out of sixteen individuals) with a recent history of stress, suggesting stress affects silk production process in orb web spiders. Based on reported sequences for MaSp genes, we developed a gene expression model showing the covariation of the most abundant amino acids in major ampullate silk. Our gene expression model supports that dragline silk composition was mostly determined by the relative abundance of MaSp1 and MaSp2. Finally, we showed that silk composition (especially proline content) strongly correlated with some measures of mechanical performance, particularly how much fibers shrunk during supercontraction as well as their breaking strains. Our findings suggest that spiders are able to change the relative expression rates of different MaSp genes to produce silk fibers with different chemical compositions, and hence, different material properties.

Silk sericin loaded alginate nanoparticles: Preparation and anti-inflammatory efficacy.

PubMed

Khampieng, Thitikan; Aramwit, Pornanong; Supaphol, Pitt

2015-09-01

In this study, silk sericin loaded alginate nanoparticles were prepared by the emulsification method followed by internal crosslinking. The effects of various silk sericin loading concentration on particle size, shape, thermal properties, and release characteristics were investigated. The initial silk sericin loadings of 20, 40, and 80% w/w to polymer were incorporated into these alginate nanoparticles. SEM images showed a spherical shape and small particles of about 71.30-89.50 nm. TGA analysis showed that thermal stability slightly increased with increasing silk sericin loadings. FTIR analysis suggested interactions between alginate and silk sericin in the nanoparticles. The release study was performed in acetate buffer at normal skin conditions (pH 5.5; 32 °C). The release profiles of silk sericin exhibited initial rapid release, consequently with sustained release. These silk sericin loaded alginate nanoparticles were further incorporated into topical hydrogel and their anti-inflammatory properties were studied using carrageenan-induced paw edema assay. The current study confirms the hypothesis that the application of silk sericin loaded alginate nanoparticle gel can inhibit inflammation induced by carrageenan. Copyright © 2015 Elsevier B.V. All rights reserved.

The protective ability of Camellia meal extract on the silk protein

NASA Astrophysics Data System (ADS)

Weng, JZ; Cai, C.; Zhang, DY; Dai, BK

2018-02-01

With the enhancement of living standards, people pay more and more attention to the health. The edible oil become more and more popular, but also produced a large amount of Camellia meal which can not fully put into utilization. In this study, the extracting liquid of Camellia meal was used on the process of silk degumming. Firstly, tussah silk was treated by degumming in the Na2CO3 solution, and the preliminary condition of tussah silk degumming was obtained by orthogonal experiment: the concentration Na2CO3 was 0.1%, the degumming time was 1 hour, and the ratio of silk/water was 40:1. Then the extract of Camellia meal (GCJSY) was added before the bleaching process of tussah silk to investigate the protective ability of GCJSY on the silk protein basry on the residual ratio of the silk. While the concentration of GYJSY was 0.08%, the residual ratio of silk after degumming in the Na2CO3 solution and bleaching in the 2% H2O2 solution was 87.2%.

Structuring of Functional Spider Silk Wires, Coatings, and Sheets by Self-Assembly on Superhydrophobic Pillar Surfaces.

PubMed

Gustafsson, Linnea; Jansson, Ronnie; Hedhammar, My; van der Wijngaart, Wouter

2018-01-01

Spider silk has recently become a material of high interest for a large number of biomedical applications. Previous work on structuring of silk has resulted in particles (0D), fibers (1D), films (2D), and foams, gels, capsules, or microspheres (3D). However, the manufacturing process of these structures is complex and involves posttreatment of chemicals unsuitable for biological applications. In this work, the self-assembly of recombinant spider silk on micropatterned superhydrophobic surfaces is studied. For the first time, structuring of recombinant spider silk is achieved using superhydrophobic surfaces under conditions that retain the bioactivity of the functionalized silk. By tuning the superhydrophobic surface geometry and the silk solution handling parameters, this approach allows controlled generation of silk coatings, nanowires, and sheets. The underlying mechanisms and governing parameters are discussed. It is believed that the results of this work pave the way for fabrication of silk formations for applications including vehicles for drug delivery, optical sensing, antimicrobial coatings, and cell culture scaffolds. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Biocompatibility of a Sonicated Silk Gel for Cervical Injection During Pregnancy

PubMed Central

Critchfield, Agatha S.; Mccabe, Reid; Klebanov, Nikolai; Richey, Lauren; Socrate, Simona; Norwitz, Errol R.; Kaplan, David L.; House, Michael

2014-01-01

Objective: To evaluate the biocompatibility of silk gel for cervical injection. Study Design: Silk gel was injected into the cervix of pregnant rats on day 13 (n = 11) and harvested at day 17. Histology of silk gel was compared with suture controls. Also, human cervical fibroblasts were cultured on silk gel and tissue culture plastic (TCP) in vitro. Cell viability, proliferation, metabolic activity, gene expression (COL1A1, COL3A1, and COX2), and release of proinflammatory mediators (interleukin [IL] 6 and IL-8) were evaluated. Results: In vivo, a mild foreign body response was seen surrounding the silk gel and suture controls. In vitro, cervical fibroblasts were viable, metabolically active, and proliferating at 72 hours. Release of IL-6 and IL-8 was similar on silk gel and TCP. Collagen and COX2 gene expression was similar or slightly decreased compared with TCP. Conclusions: Silk gel was well tolerated in vivo and in vitro, which supports continuing efforts to develop silk gels as an alternative to cervical cerclage. PMID:24520079

Clay-Enriched Silk Biomaterials for Bone Formation

PubMed Central

Mieszawska, Aneta J.; Llamas, Jabier Gallego; Vaiana, Christopher A.; Kadakia, Madhavi P.; Naik, Rajesh R.; Kaplan, David L.

2011-01-01

The formation of silk protein/clay composite biomaterials for bone tissue formation is described. Silk fibroin serves as an organic scaffolding material offering mechanical stability suitable for bone specific uses. Clay montmorillonite (Cloisite ® Na+) and sodium silicate are sources of osteoinductive silica-rich inorganic species, analogous to bioactive bioglass-like bone repair biomaterial systems. Different clay particle-silk composite biomaterial films were compared to silk films doped with sodium silicate as controls for support of human bone marrow derived mesenchymal stem cells (hMSCs) in osteogenic culture. The cells adhered and proliferated on the silk/clay composites over two weeks. Quantitative real-time RT-PCR analysis revealed increased transcript levels for alkaline phosphatase (ALP), bone sialoprotein (BSP), and collagen type 1 (Col I) osteogenic markers in the cells cultured on the silk/clay films in comparison to the controls. Early evidence for bone formation based on collagen deposition at the cell-biomaterial interface was also found, with more collagen observed for the silk films with higher contents of clay particles. The data suggest that the silk/clay composite systems may be useful for further study toward bone regenerative needs. PMID:21549864

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lewis, Randolph

Spider silks have the potential to provide new bio-inspired materials for numerous applications in bioenergetics and products ranging from protective clothing to artificial ligaments and tendons. A number of spider silk genes have been cloned and sequenced by the Lewis laboratory revealing the basis for understanding the key elements of spider silk proteins with respect to their materials performance. In particular, specific amino acid motifs have been identified which have been conserved for over 125 million years in all spiders that use their silk to physically trap prey. The key element in taking the next step toward generating bio-based materialsmore » from spider silks will be to move from the current descriptive data to predictive knowledge. Current efforts are focused on mimicking spider silk through synthetic proteins. In developing synthetic silk fibers, we first need to understand the complete secondary and tertiary structure of natural silk so that we can compare synthetic constructs to the natural material. Being able to compare the structure on a single fiber level is critical to the future of molecular directed mimic development because we can vary mechanical properties by different spinning methods. The new generation of synchrotron x-ray diffraction and neutron beamlines will allow, for the first time, determination of the molecular structure of silk fibers and synthetic mimics. We propose an exciting new collaborative research team working jointly between Argonne National Laboratory, Arizona State U. and the University of Wyoming to address the ?characterization of synthetic and natural spider silk fibers using x-ray and neutron diffraction.? Thus these new methodologies will provide understanding of current fibers and determine changes needed to produce fibers with specific properties. The following specific aims are proposed: ? Synthesize spider silk fibers with molecular structures mimicking that of natural silks. Test the mechanic properties of these materials and compare them to natural silk fibers. ? Develop x-ray and neutron diffraction techniques to better determine the structure in amorphous and semicrystalline biopolymers, such as spider silk fibers. ? Combine mechanical testing and structural x-ray and neutron diffraction data to develop a molecular understanding of the structure-function relationship in spider silk materials. ? Elucidate the role water plays in spider silk fiber formation and structure. Emphasis will be placed on combined neutron and NMR studies. ? Use solid-state Nuclear Magnetic Resonance (NMR) to characterize synthetic and natural spider silk materials that show potential as a biomimetic material or bio-inspired polymer architecture. ? Develop EPSCoR student and postdoctoral training and exposure to national laboratory facilities. ? Further develop scientific outreach and chemical education programs and research.« less

Silk fibroin-chondroitin sulfate scaffold with immuno-inhibition property for articular cartilage repair.

PubMed

Zhou, Feifei; Zhang, Xianzhu; Cai, Dandan; Li, Jun; Mu, Qin; Zhang, Wei; Zhu, Shouan; Jiang, Yangzi; Shen, Weiliang; Zhang, Shufang; Ouyang, Hong Wei

2017-11-01

The demand of favorable scaffolds has increased for the emerging cartilage tissue engineering. Chondroitin sulfate (CS) and silk fibroin have been investigated and reported with safety and excellent biocompatibility as tissue engineering scaffolds. However, the rapid degradation rate of pure CS scaffolds presents a challenge to effectively recreate neo-tissue similar to natural articular cartilage. Meanwhile the silk fibroin is well used as a structural constituent material because its remarkable mechanical properties, long-lasting in vivo stability and hypoimmunity. The application of composite silk fibroin and CS scaffolds for joint cartilage repair has not been well studied. Here we report that the combination of silk fibroin and CS could synergistically promote articular cartilage defect repair. The silk fibroin (silk) and silk fibroin/CS (silk-CS) scaffolds were fabricated with salt-leaching, freeze-drying and crosslinking methodologies. The biocompatibility of the scaffolds was investigated in vitro by cell adhesion, proliferation and migration with human articular chondrocytes. We found that silk-CS scaffold maintained better chondrocyte phenotype than silk scaffold; moreover, the silk-CS scaffolds reduced chondrocyte inflammatory response that was induced by interleukin (IL)-1β, which is in consistent with the well-documented anti-inflammatory activities of CS. The in vivo cartilage repair was evaluated with a rabbit osteochondral defect model. Silk-CS scaffold induced more neo-tissue formation and better structural restoration than silk scaffold after 6 and 12weeks of implantation in ICRS histological evaluations. In conclusion, we have developed a silk fibroin/ chondroitin sulfate scaffold for cartilage tissue engineering that exhibits immuno-inhibition property and can improve the self-repair capacity of cartilage. Severe cartilage defect such as osteoarthritis (OA) is difficult to self-repair because of its avascular, aneural and alymphatic nature. Current scaffolds often focus on providing sufficient mechanical support or bio-mimetic structure to promote cartilage repair. Thus, silk has been adopted and investigated broadly. However, inflammation is one of the most important factors in OA. But few scaffolds for cartilage repair reported anti-inflammation property. Meanwhile, chondroitin sulfate (CS) is a glycosaminoglycan present in the natural cartilage ECM, and has exhibited a number of useful biological properties including anti-inflammatory activity. Thus, we designed this silk-CS scaffold and proved that this scaffold exhibited good anti-inflammatory effects both in vitro and in vivo, promoted the repair of articular cartilage defect in animal model. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Fabrication and Biocompatibility of Electrospun Silk Biocomposites

PubMed Central

Wei, Kai; Kim, Byoung-Suhk; Kim, Ick-Soo

2011-01-01

Silk fibroin has attracted great interest in tissue engineering because of its outstanding biocompatibility, biodegradability and minimal inflammatory reaction. In this study, two kinds of biocomposites based on regenerated silk fibroin are fabricated by electrospinning and post-treatment processes, respectively. Firstly, regenerated silk fibroin/tetramethoxysilane (TMOS) hybrid nanofibers with high hydrophilicity are prepared, which is superior for fibroblast attachment. The electrospinning process causes adjacent fibers to ‘weld’ at contact points, which can be proved by scanning electron microscope (SEM). The water contact angle of silk/tetramethoxysilane (TMOS) composites shows a sharper decrease than pure regenerated silk fibroin nanofiber, which has a great effect on the early stage of cell attachment behavior. Secondly, a novel tissue engineering scaffold material based on electrospun silk fibroin/nano-hydroxyapatite (nHA) biocomposites is prepared by means of an effective calcium and phosphate (Ca–P) alternate soaking method. nHA is successfully produced on regenerated silk fibroin nanofiber within several min without any pre-treatments. The osteoblastic activities of this novel nanofibrous biocomposites are also investigated by employing osteoblastic-like MC3T3-E1 cell line. The cell functionality such as alkaline phosphatase (ALP) activity is ameliorated on mineralized silk nanofibers. All these results indicate that this silk/nHA biocomposite scaffold material may be a promising biomaterial for bone tissue engineering. PMID:24957869

Silk elasticity as a potential constraint on spider body size.

PubMed

Rodríguez-Gironés, Miguel A; Corcobado, Guadalupe; Moya-Laraño, Jordi

2010-10-07

Silk is known for its strength and extensibility and has played a key role in the radiation of spiders. Individual spiders use different glands to produce silk types with unique sets of proteins. Most research has studied the properties of major ampullate and capture spiral silks and their ecological implications, while little is known about minor ampullate silk, the type used by those spider species studied to date for bridging displacements. A biomechanical model parameterised with available data shows that the minimum radius of silk filaments required for efficient bridging grows with the square root of the spider's body mass, faster than the radius of minor ampullate silk filaments actually produced by spiders. Because the morphology of spiders adapted to walking along or under silk threads is ill suited for moving on a solid surface, for these species there is a negative relationship between body mass and displacement ability. As it stands, the model suggests that spiders that use silk for their displacements are prevented from attaining a large body size if they must track their resources in space. In particular, silk elasticity would favour sexual size dimorphism because males that must use bridging lines to search for females cannot grow large. 2010 Elsevier Ltd. All rights reserved.

Bimorph Silk Microsheets with Programmable Actuating Behavior: Experimental Analysis and Computer Simulations.

PubMed

Ye, Chunhong; Nikolov, Svetoslav V; Geryak, Ren D; Calabrese, Rossella; Ankner, John F; Alexeev, Alexander; Kaplan, David L; Tsukruk, Vladimir V

2016-07-13

Microscaled self-rolling construct sheets from silk protein material have been fabricated, containing a silk bimorph composed of silk ionomers as an active layer and cross-linked silk β-sheet as the passive layer. The programmable morphology was experimentally explored along with a computational simulation to understand the mechanism of shape reconfiguration. The neutron reflectivity shows that the active silk ionomers layer undergoes remarkable swelling (eight times increase in thickness) after deprotonation while the passive silk β-sheet retains constant volume under the same conditions and supports the bimorph construct. This selective swelling within the silk-on-silk bimorph microsheets generates strong interfacial stress between layers and out-of-plane forces, which trigger autonomous self-rolling into various 3D constructs such as cylindrical and helical tubules. The experimental observations and computational modeling confirmed the role of interfacial stresses and allow programming the morphology of the 3D constructs with particular design. We demonstrated that the biaxial stress distribution over the 2D planar films depends upon the lateral dimensions, thickness and the aspect ratio of the microsheets. The results allow the fine-tuning of autonomous shape transformations for the further design of complex micro-origami constructs and the silk based rolling/unrolling structures provide a promising platform for polymer-based biomimetic devices for implant applications.

Investigating the transverse optical structure of spider silk micro-fibers using quantitative optical microscopy

NASA Astrophysics Data System (ADS)

Little, Douglas J.; Kane, Deb M.

2017-01-01

The transverse optical structure of two orb-weaver (family Araneidae) spider dragline silks was investigated using a variant of the inverse-scattering technique. Immersing the silks in a closely refractive index-matched liquid, the minimum achievable image contrast was greater than expected for an optically homogeneous silk, given what is currently known about the optical absorption of these silks. This "excess contrast" indicated the presence of transverse optical structure within the spider silk. Applying electromagnetic scattering theory to a transparent double cylinder, the minimum achievable irradiance contrast for the Plebs eburnus and Argiope keyserlingi dragline silks was determined to be consistent with step index refractive index contrasts of 1-4×10-4 and 6-7×10-4, respectively, supposing outer-layer thicknesses consistent with previous TEM studies (50 nm and 100 nm, respectively). The possibility of graded index refractive index contrasts within the spider silks is also discussed. This is the strongest evidence, to date, that there is a refractive index contrast associated with the layered morphology of spider silks and/or variation of proportion of nanocrystalline components within the spider silk structure. The method is more generally applicable to optical micro-fibers, including those with refractive index variations on a sub-wavelength scale.

Effects of Microwave Radiation on Selected Mechanical Properties of Silk

NASA Astrophysics Data System (ADS)

Reed, Emily Jane

Impressive mechanical properties have served to peak interest in silk as an engineering material. In addition, the ease with which silk can be altered through processing has led to its use in various biomaterial applications. As the uses of silk branch into new territory, it is imperative (and inevitable) to discover the boundary conditions beyond which silk no longer performs as expected. These boundary conditions include factors as familiar as temperature and humidity, but may also include other less familiar contributions, such as exposure to different types of radiation. The inherent variations in mechanical properties of silk, as well as its sensitivity to moisture, suggest that in an engineering context silk is best suited for use in composite materials; that way, silk can be shielded from ambient moisture fluctuations, and the surrounding matrix allows efficient load transfer from weaker fibers to stronger ones. One such application is to use silk as a reinforcing fiber in epoxy composites. When used in this way, there are several instances in which exposure to microwave radiation is likely (for example, as a means of speeding epoxy cure rates), the effects of which remain mostly unstudied. It will be the purpose of this dissertation to determine whether selected mechanical properties of B. mori cocoon silk are affected by exposure to microwave radiation, under specified temperature and humidity conditions. Results of our analyses are directly applicable wherever exposure of silk to microwave radiation is possible, including in fiber reinforced epoxy composites (the entire composite may be microwaved to speed epoxy cure time), or when silk is used as a component in the material used to construct the radome of an aircraft (RADAR units use frequencies in the microwave range of the electromagnetic spectrum), or when microwave energy is used to sterilize biomaterials (such as cell scaffolds) made of silk. In general, we find that microwave exposure does not detract from the average mechanical properties of silk, but that it may increase the spread of data points around that average. Along the way, we come to a number of useful conclusions, summarized here: Regarding silk in general: • Storage conditions can have a significant and enduring effect on tensile properties of degummed B. mori silk. Samples stored in a sealed container with desiccant (silica gel) have a lower yield stress and yield strain than samples stored without desiccant and they also relax more rapidly in stress relaxation tests. The ability of this silk to resist plastic deformation is optimized at intermediate hydration levels. Sensitivity to the humidity levels encountered by samples prior to testing complicates the interpretation of results, and makes inter-laboratory comparisons challenging. Silk storage conditions should therefore be reported---and, ideally, standardized---to enable useful comparison between studies. (Abstract shortened by UMI.)

Invited review current progress and limitations of spider silk for biomedical applications.

PubMed

Widhe, Mona; Johansson, Jan; Hedhammar, My; Rising, Anna

2012-06-01

Spider silk is a fascinating material combining remarkable mechanical properties with low density and biodegradability. Because of these properties and historical descriptions of medical applications, spider silk has been proposed to be the ideal biomaterial. However, overcoming the obstacles to produce spider silk in sufficient quantities and in a manner that meets regulatory demands has proven to be a difficult task. Also, there are relatively few studies of spider silk in biomedical applications available, and the methods and materials used vary a lot. Herein we summarize cell culture- and in vivo implantation studies of natural and synthetic spider silk, and also review the current status and future challenges in the quest for a large scale production of spider silk for medical applications. Copyright © 2011 Wiley Periodicals, Inc.

Thromboelastometric and platelet responses to silk biomaterials.

PubMed

Kundu, Banani; Schlimp, Christoph J; Nürnberger, Sylvia; Redl, Heinz; Kundu, S C

2014-05-13

Silkworm's silk is natural biopolymer with unique properties including mechanical robustness, all aqueous base processing and ease in fabrication into different multifunctional templates. Additionally, the nonmulberry silks have cell adhesion promoting tri-peptide (RGD) sequences, which make it an immensely potential platform for regenerative medicine. The compatibility of nonmulberry silk with human blood is still elusive; thereby, restricts its further application as implants. The present study, therefore, evaluate the haematocompatibility of silk biomaterials in terms of platelet interaction after exposure to nonmulberry silk of Antheraea mylitta using thromboelastometry (ROTEM). The mulberry silk of Bombyx mori and clinically used Uni-Graft W biomaterial serve as references. Shortened clotting time, clot formation times as well as enhanced clot strength indicate the platelet mediated activation of blood coagulation cascade by tested biomaterials; which is comparable to controls.

Regenerated silk materials for functionalized silk orthopedic devices by mimicking natural processing.

PubMed

Li, Chunmei; Hotz, Blake; Ling, Shengjie; Guo, Jin; Haas, Dylan S; Marelli, Benedetto; Omenetto, Fiorenzo; Lin, Samuel J; Kaplan, David L

2016-12-01

Silk fibers spun by silkworms and spiders exhibit exceptional mechanical properties with a unique combination of strength, extensibility and toughness. In contrast, the mechanical properties of regenerated silk materials can be tuned through control of the fabrication process. Here we introduce a biomimetic, all-aqueous process, to obtain bulk regenerated silk-based materials for the fabrication of functionalized orthopedic devices. The silk materials generated in the process replicate the nano-scale structure of natural silk fibers and possess excellent mechanical properties. The biomimetic materials demonstrate excellent machinability, providing a path towards the fabrication of a new family of resorbable orthopedic devices where organic solvents are avoided, thus allowing functionalization with bioactive molecules to promote bone remodeling and integration. Copyright © 2016 Elsevier Ltd. All rights reserved.

Sculpting with light: Light/matter interactions in biocompatible polymers

NASA Astrophysics Data System (ADS)

Applegate, Matthew B.

When light interacts with matter either the light or the material can be changed. This dissertation focuses on light/matter interaction in silk fibroin and its utility for biomedical applications. Silk, a natural biocompatible, biodegradable polymer, has a large 3-photon absorption cross-section which allows modest peak intensity light to cause significant multiphoton absorption. This absorption allows voids to be formed with three dimensional control within soft, transparent silk hydrogels. A theoretical model of the void formation process is developed to allow the size of the voids to be predicted for a range of laser and sample parameters. Arbitrary 3D patterns are created in silk gels that allow cells to penetrate into the bulk of the gel both in vitro and in vivo. To explore how silk can be used to alter light, the creation of step-index optical waveguides, formed by encapsulating a silk film within a silk hydrogel, is described. These waveguides allow light to be delivered to targets through several centimeters of highly scattering biological tissue. Finally, the interaction of light with riboflavin is used to photocrosslink silk to form solid structures, rather than voids. The mechanism of crosslinking to be driven by radicalized tyrosine residues resulting in the formation of dityrosine bonds which lead to the gelation of a liquid silk solution. Riboflavin is a versatile photoinitiator and can be used to crosslink collagen as well as silk, which allows silk to be crosslinked directly to corneal collagen. When applied to the eye, an artificial corneal layer is formed which has the potential to treat various corneal diseases and allow for risk-free laser vision correction. These studies show the versatility of light-based processing of silk for a wide variety of medical applications.

The effect of native silk fibroin powder on the physical properties and biocompatibility of biomedical polyurethane membrane.

PubMed

Zhuang, Yan; Zhang, Qian; Feng, Jinqi; Wang, Na; Xu, Weilin; Yang, Hongjun

2017-04-01

Naturally derived fibers such as silk fibroin can potentially enhance the biocompatibility of currently used biomaterials. This study investigated the physical properties of native silk fibroin powder and its effect on the biocompatibility of biomedical polyurethane. Native silk fibroin powder with an average diameter of 3 µm was prepared on a purpose-built machine. A simple method of phase inversion was used to produce biomedical polyurethane/native silk fibroin powder hybrid membranes at different blend ratios by immersing a biomedical polyurethane/native silk fibroin powder solution in deionized water at room temperature. The physical properties of the membranes including morphology, hydrophilicity, roughness, porosity, and compressive modulus were characterized, and in vitro biocompatibility was evaluated by seeding the human umbilical vein endothelial cells on the top surface. Native silk fibroin powder had a concentration-dependent effect on the number and morphology of human umbilical vein endothelial cells growing on the membranes; cell number increased as native silk fibroin powder content in the biomedical polyurethane/native silk fibroin powder hybrid membrane was increased from 0% to 50%, and cell morphology changed from spindle-shaped to cobblestone-like as the native silk fibroin powder content was increased from 0% to 70%. The latter change was related to the physical characteristics of the membrane, including hydrophilicity, roughness, and mechanical properties. The in vivo biocompatibility of the native silk fibroin powder-modified biomedical polyurethane membrane was evaluated in a rat model; the histological analysis revealed no systemic toxicity. These results indicate that the biomedical polyurethane/native silk fibroin powder hybrid membrane has superior in vitro and in vivo biocompatibility relative to 100% biomedical polyurethane membranes and thus has potential applications in the fabrication of small-diameter vascular grafts and in tissue engineering.

Silk Nanospheres and Microspheres from Silk/PVA Blend Films for Drug Delivery

PubMed Central

Wang, Xiaoqin; Yucel, Tuna; Lu, Qiang; Hu, Xiao; Kaplan, David L.

2009-01-01

Silk fibroin protein-based micro- and nanospheres provide new options for drug delivery due to their biocompatibility, biodegradability and their tunable drug loading and release properties. In the present study, we report a new aqueous-based preparation method for silk spheres with controllable sphere size and shape. The preparation was based on phase separation between silk fibroin and polyvinyl alcohol (PVA) at a weight ratio of 1/1 and 1/4. Water-insoluble silk spheres were easily obtained from the blend in a three step process: (1) air-drying the blend solution into a film, (2) film dissolution in water and (3) removal of residual PVA by subsequent centrifugation. In both cases, the spheres had approximately 30% beta-sheet content and less than 5% residual PVA. Spindle-shaped silk particles, as opposed to the spherical particles formed above, were obtained by stretching the blend films before dissolving in water. Compared to the 1/1 ratio sample, the silk spheres prepared from the 1/4 ratio sample showed a more homogeneous size distribution ranging from 300 nm up to 20 μm. Further studies showed that sphere size and polydispersity could be controlled either by changing the concentration of silk and PVA or by applying ultrasonication on the blend solution. Drug loading was achieved by mixing model drugs in the original silk solution. The distribution and loading efficiency of the drug molecules in silk spheres depended on their hydrophobicity and charge, resulting in different drug release profiles. The entire fabrication procedure could be completed within one day. The only chemical used in the preparation except water was PVA, an FDA-approved ingredient in drug formulations. Silk micro- and nanospheres reported have potential as drug delivery carriers in a variety of biomedical applications. PMID:19945157

Traveling the Silk Road: A Measurement of a Large Anonymous Online Marketplace

DTIC Science & Technology

2012-11-28

Silk Road, an anonymous, international online marketplace that operates as a Tor hidden service and uses Bitcoin as its exchange currency. We gather...analysis of Silk Road, an anonymous, international on- line marketplace that operates as a Tor hidden service and uses Bitcoin as its exchange currency. We...anonymity, Silk Road needs to also preserve payment anonymity. To that effect, Silk Road only supports Bitcoin (BTC, [30]) as a trading currency

Evaluating drug trafficking on the Tor Network: Silk Road 2, the sequel.

PubMed

Dolliver, Diana S

2015-11-01

Housing an illicit, online drug retail market generating sales in the millions of USD, the Silk Road was a profitable marketplace with a growing and loyal consumer base. Following its FBI-forced shut down in October 2013, the Silk Road enjoyed newfound fame that contributed to an increase in new users downloading and accessing the Tor Network; however, with this particular marketplace out of order, Silk Road 2 was launched to fill the void. The goals of this study were to (1) compare the metrics of Silk Road 2 to the original site, and to (2) determine if there were any indications of the presence of more sophisticated drug trafficking operations. Data were collected from Silk Road 2 during the months of August and September 2014 using webcrawling software. Silk Road 2 was a much smaller marketplace than the original Silk Road. Of the 1834 unique items for sale, 348 were drug items sold by 145 distinct vendors shipping from 19 countries. Of the drug items advertised, most were stimulants and hallucinogens. The United States is both the number one country of origin for drug sales on Silk Road 2 and the number one destination country. Interestingly, 73% of all vendor accounts on Silk Road 2 advertised drug items, even though drugs only constituted 19% of all items advertised. This study was the first to research Silk Road 2, the replacement illicit marketplace to the original virtual Silk Road. This study was also the first to examine indications of the presence of more coordinated drug trafficking efforts in an online setting. The findings indicated that while Silk Road 2 was not primarily a drug market, there were indications that some vendor accounts may have connections reaching beyond a base retail market. Copyright © 2015 Elsevier B.V. All rights reserved.

Inhibitory effect of corn silk on skin pigmentation.

PubMed

Choi, Sang Yoon; Lee, Yeonmi; Kim, Sung Soo; Ju, Hyun Min; Baek, Ji Hwoon; Park, Chul-Soo; Lee, Dong-Hyuk

2014-03-03

In this study, the inhibitory effect of corn silk on melanin production was evaluated. This study was performed to investigate the inhibitory effect of corn silk on melanin production in Melan-A cells by measuring melanin production and protein expression. The corn silk extract applied on Melan-A cells at a concentration of 100 ppm decreased melanin production by 37.2% without cytotoxicity. This was a better result than arbutin, a positive whitening agent, which exhibited a 26.8% melanin production inhibitory effect at the same concentration. The corn silk extract did not suppress tyrosinase activity but greatly reduced the expression of tyrosinase in Melan-A cells. In addition, corn silk extract was applied to the human face with hyperpigmentation, and skin color was measured to examine the degree of skin pigment reduction. The application of corn silk extract on faces with hyperpigmentation significantly reduced skin pigmentation without abnormal reactions. Based on the results above, corn silk has good prospects for use as a material for suppressing skin pigmentation.

Silk Self-Assembly Mechanisms and Control-From Thermodynamics to Kinetics

PubMed Central

Lu, Qiang; Zhu, Hesun; Zhang, Cencen; Zhang, Feng; Zhang, Bing; Kaplan, David L.

2012-01-01

Silkworms and spiders generate fibres that exhibit high strength and extensibility. The underlying mechanisms involved in processing silk proteins into fiber form remain incompletely understood, resulting in the failure to fully recapitulate the remarkable properties of native fibers in vitro from regenerated silk solutions. In the present study, the extensibility and high strength of regenerated silks were achieved by mimicking the natural spinning process. Conformational transitions inside micelles, followed by aggregation of micelles and their stabilization as they relate to the metastable structure of silk are described. Subsequently, the mechanisms to control the formation of nanofibrous structures were elucidated. The results clarify that the self-assembly of silk in aqueous solution is a thermodynamically driven process where kinetics also play a key role. Four key factors, molecular mobility, charge, hydrophilic interactions and concentration underlie the process. Adjusting these factors can balance nanostructure and conformational composition, and be used to achieve silk-based materials with properties comparable to native fibers. These mechanisms suggest new directions to design silk-based multifunctional materials. PMID:22320432

The Potential of Silk and Silk-Like Proteins as Natural Mucoadhesive Biopolymers for Controlled Drug Delivery.

PubMed

Brooks, Amanda E

2015-01-01

Drug delivery across mucus membranes is a particularly effective route of administration due to the large surface area. However, the unique environment present at the mucosa necessitates altered drug formulations designed to (1) deliver sensitive biologic molecules, (2) promote intimate contact between the mucosa and the drug, and (3) prolong the drug's local residence time. Thus, the pharmaceutical industry has an interest in drug delivery systems formulated around the use of mucoadhesive polymers. Mucoadhesive polymers, both synthetic and biological, have a history of use in local drug delivery. Prominently featured in the literature are chitosan, alginate, and cellulose derivatives. More recently, silk and silk-like derivatives have been explored for their potential as mucoadhesive polymers. Both silkworms and spiders produce sticky silk-like glue substances, sericin and aggregate silk respectively, that may prove an effective, natural matrix for drug delivery to the mucosa. This mini review will explore the potential of silk and silk-like derivatives as a biocompatible mucoadhesive polymer matrix for local controlled drug delivery.

An Unlikely Silk: The Composite Material of Green Lacewing Cocoons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weisman, Sarah; Trueman, Holly E.; Mudie, Stephen T.

2009-01-15

Spiders routinely produce multiple types of silk; however, common wisdom has held that insect species produce one type of silk each. This work reports that the green lacewing (Mallada signata, Neuroptera) produces two distinct classes of silk. We identified and sequenced the gene that encodes the major protein component of the larval lacewing cocoon silk and demonstrated that it is unrelated to the adult lacewing egg-stalk silk. The cocoon silk protein is 49 kDa in size and is alanine rich (>40%), and it contains an {alpha}-helical secondary structure. The final instar lacewing larvae spin protein fibers of {approx}2 {mu}m diametermore » to construct a loosely woven cocoon. In a second stage of cocoon construction, the insects lay down an inner wall of lipids that uses the fibers as a scaffold. We propose that the silk protein fibers provide the mechanical strength of the composite lacewing cocoon whereas the lipid layer provides a barrier to water loss during pupation.« less

De novo design of recombinant spider silk proteins for material applications.

PubMed

Zheng, Ke; Ling, Shengjie

2018-05-21

Spider silks are well known for their superior mechanical properties that are stronger and tougher than steel despite being assembled at close to ambient conditions and using water as the solvent. However, it is a significant challenge to utilize spider silks for practical applications due to their limited sources. Fortunately, genetic engineering techniques offer a promising approach to produce useable amounts of spider silk variants. Starting from these recombinant spider silk proteins, a series of experiments and simulations strategies were developed to improve the recombinant spider silk proteins (RSSP) material design and fabrication with the aim of biomimicking the structure-property-function relationships of spider silks. Accordingly, in this review, we first introduce the structure-property-function relationship of spider silks. Then, we discuss the recent progress in the genetic synthesis of RSSPs and summarize their related multiscale self-assembly behaviors. Finally, we outline works utilizing multiscale modeling to assist RSSP material design. This article is protected by copyright. All rights reserved.

Silk-microfluidics for advanced biotechnological applications: A progressive review.

PubMed

Konwarh, Rocktotpal; Gupta, Prerak; Mandal, Biman B

2016-01-01

Silk based biomaterials have not only carved a unique niche in the domain of regenerative medicine but new avenues are also being explored for lab-on-a-chip applications. It is pertinent to note that biospinning of silk represents nature's signature microfluidic-maneuver. Elucidation of non-Newtonian flow of silk in the glands of spiders and silkworms has inspired researchers to fabricate devices for continuous extrusion and concentration of silk. Microfluidic channel networks within porous silk scaffolds ensure optimal nutrient and oxygen supply apart from serving as precursors for vascularization in tissue engineering applications. On the other hand, unique topographical features and surface wettability of natural silk fibers have inspired development of a number of simple and cost-effective devices for applications like blood typing and chemical sensing. This review mirrors the recent progress and challenges in the domain of silk-microfluidics for prospective avant-garde applications in the realm of biotechnology. Copyright © 2016 Elsevier Inc. All rights reserved.

DNA replication events during larval silk gland development in the silkworm, Bombyx mori.

PubMed

Zhang, Chun-Dong; Li, Fang-Fang; Chen, Xiang-Yun; Huang, Mao-Hua; Zhang, Jun; Cui, Hongjuan; Pan, Min-Hui; Lu, Cheng

2012-07-01

The silk gland is an important organ in silkworm as it synthesizes silk proteins and is critical to spinning. The genomic DNA content of silk gland cells dramatically increases 200-400 thousand times for the larval life span through the process of endomitosis. Using in vitro culture, DNA synthesis was measured using BrdU labeling during the larval molt and intermolt periods. We found that the cell cycle of endomitosis was activated during the intermolt and was inhibited during the molt phase. The anterior silk gland, middle silk gland, and posterior silk gland cells asynchronously exit the endomitotic cycle after day 6 in 5th instar larvae, which correlated with the reduced expression of the cell cycle-related cdt1, pcna, cyclin E, cdk2 and cdk1 mRNAs in the wandering phase. Additional starvation had no effect on the initiation of silk gland DNA synthesis of the freshly ecdysed larvae. Copyright © 2012 Elsevier Ltd. All rights reserved.

Biomedical Applications of Mulberry Silk and its Proteins: A Review

NASA Astrophysics Data System (ADS)

Nivedita, S.; Sivaprasad, V.

2014-04-01

Silk is a natural fibre used mainly for aesthetic purposes. It has also been used for making surgical sutures for centuries. The recent rediscovery of silk's biological properties have led to new areas of research and utilization in cosmetic, health and medical fields. The silk proteins, fibroin and sericin are processed into biomaterials because of bio-compatibility, bio-degradability, excellent mechanical properties, thermo tolerance and UV protective properties. Silk proteins could be obtained as pure liquids and regenerated in different forms suitable for tissue engineering applications. This paper presents some of the biomedical products and biomaterials made from native, degraded and regenerated silk and their fabrication techniques.

Biomimetic Hybridization of Kevlar into Silk Fibroin: Nanofibrous Strategy for Improved Mechanic Properties of Flexible Composites and Filtration Membranes.

PubMed

Lv, Lili; Han, Xiangsheng; Zong, Lu; Li, Mingjie; You, Jun; Wu, Xiaochen; Li, Chaoxu

2017-08-22

Silk, one of the strongest natural biopolymers, was hybridized with Kevlar, one of the strongest synthetic polymers, through a biomimetic nanofibrous strategy. Regenerated silk materials have outstanding properties in transparency, biocompatibility, biodegradability and sustainability, and promising applications as diverse as in pharmaceutics, electronics, photonic devices and membranes. To compete with super mechanic properties of their natural counterpart, regenerated silk materials have been hybridized with inorganic fillers such as graphene and carbon nanotubes, but frequently lose essential mechanic flexibility. Inspired by the nanofibrous strategy of natural biomaterials (e.g., silk fibers, hemp and byssal threads of mussels) for fantastic mechanic properties, Kevlar was integrated in regenerated silk materials by combining nanometric fibrillation with proper hydrothermal treatments. The resultant hybrid films showed an ultimate stress and Young's modulus two times as high as those of pure regenerated SF films. This is not only because of the reinforcing effect of Kevlar nanofibrils, but also because of the increasing content of silk β-sheets. When introducing Kevlar nanofibrils into the membranes of silk nanofibrils assembled by regenerated silk fibroin, the improved mechanic properties further enabled potential applications as pressure-driven nanofiltration membranes and flexible substrates of electronic devices.

Controllable in situ synthesis of silver nanoparticles on multilayered film-coated silk fibers for antibacterial application.

PubMed

Meng, Mei; He, Huawei; Xiao, Jing; Zhao, Ping; Xie, Jiale; Lu, Zhisong

2016-01-01

Layer-by-layer (LbL) assembly is a versatile technique for the preparation of multilayered polymeric films. However, fabrication of LbL polymetic film on silk for the in situ growth of high-density silver nanoparticles (AgNPs) has not been realized. Herein poly(acrylic acid) (PAA)/poly(dimethyldiallylammonium chloride) (PDDA) multilayers are constructed on silk via the LbL approach, subsequently serving as a 3-dimensional matrix for in situ synthesis of AgNPs. After 8 rounds of LbL assembly, the silk is fully covered with a layer of polymeric film. AgNPs with good crystalline structures could be in-situ generated in the silk-coated multilayers and their amount could be tailored by adjusting the bilayer numbers. The as-prepared silk could effectively kill the existing bacteria and inhibit the bacterial growth, demonstrating the antimicrobial activity. Moreover, the release of Ag(+) from the modified silk can last for 120 h, rendering the modified silk sustainable antimicrobial activity. This work may provide a novel method to prepare AgNPs-functionalized antimicrobial silk for potential applications in textile industry. Copyright © 2015 Elsevier Inc. All rights reserved.

The effect of ageing on the mechanical properties of the silk of the bridge spider Larinioides cornutus (Clerck, 1757)

NASA Astrophysics Data System (ADS)

Lepore, Emiliano; Isaia, Marco; Mammola, Stefano; Pugno, Nicola

2016-05-01

Spider silk is regarded as one of the best natural polymer fibers especially in terms of low density, high tensile strength and high elongation until breaking. Since only a few bio-engineering studies have been focused on spider silk ageing, we conducted nano-tensile tests on the vertical naturally spun silk fibers of the bridge spider Larinioides cornutus (Clerck, 1757) (Arachnida, Araneae) to evaluate changes in the mechanical properties of the silk (ultimate stress and strain, Young’s modulus, toughness) over time. We studied the natural process of silk ageing at different time intervals from spinning (20 seconds up to one month), comparing silk fibers spun from adult spiders collected in the field. Data were analyzed using Linear Mixed Models. We detected a positive trend versus time for the Young’s modulus, indicating that aged silks are stiffer and possibly less effective in catching prey. Moreover, we observed a negative trend for the ultimate strain versus time, attesting a general decrement of the resistance force. These trends are interpreted as being due to the drying of the silk protein chains and the reorientation among the fibers.

Heat Capacity of B. Mori Silk Fibroin Based on the Vibrational-Motion of Poly(amino acid)s.

NASA Astrophysics Data System (ADS)

Pyda, Marek; Hu, Xiao; Cebe, Peggy

2009-03-01

Bombyx mori silk fibroin heat capacities with and without water have been determined based on the vibrational motions of poly(amino acid)s and water, using the Advanced Thermal Analysis System (ATHAS) Data Bank. The heat capacities, Cp, of dry silk and silk-water were linked to their vibrational spectra based on the group and skeletal vibration contributions. For dry silk, the experimental and calculated Cp agree to better than ±3% between 200 K and 435 K. The heat capacity of the solid silk-water system, below the glass transition, was estimated from a sum of linear combinations of the molar fractions of the vibrational heat capacities of dry silk and glassy water. Calculations are compared to experimental data obtained from calorimetric methods, using hermetic and non-hermetic pans. The approach presented allows one to predict the low temperature vibrational heat capacity for dry silk and for the silk-water system down to zero kelvin, and, together with an extension to higher temperatures, above the glass transition. This can be used as a reference baseline for quantitative thermal analysis of this biomaterial..

Timing of autophagy and apoptosis during posterior silk gland degeneration in Bombyx mori.

PubMed

Montali, Aurora; Romanelli, Davide; Cappellozza, Silvia; Grimaldi, Annalisa; de Eguileor, Magda; Tettamanti, Gianluca

2017-07-01

Over the years, the silkworm, Bombyx mori, has been manipulated by means of chemical and genetic approaches to improve silk production both quantitatively and qualitatively. The silk is produced by the silk gland, which degenerates quickly once the larva has finished spinning the cocoon. Thus, interfering with this degeneration process could help develop new technologies aimed at ameliorating silk yield. To this end, in this work we studied the cell death processes that lead to the demise of the posterior silk gland of B. mori, directing in particular our attention to autophagy and apoptosis. We focused on this portion of the gland because it produces fibroin, the main component of the silk thread. By using multiple markers, we provide a morphological, biochemical and molecular characterization of the apoptotic and autophagic processes and define their timing in this biological setting. Our data demonstrate that the activation of both autophagy and apoptosis is preceded by a transcriptional rise in key regulatory genes. Moreover, while autophagy is maintained active for several days and progressively digests silk gland cells, apoptosis is only switched on at a very late stage of silk gland demise. Copyright © 2017 Elsevier Ltd. All rights reserved.

Self-assembly of silk fibroin under osmotic stress

NASA Astrophysics Data System (ADS)

Sohn, Sungkyun

The supramolecular self-assembly behavior of silk fibroin was investigated using osmotic stress technique. In Chapter 2, a ternary phase diagram of water-silk-LiBr was constructed based on X-ray results on the osmotically stressed regenerated silk fibroin of Bombyx mori silkworm. Microscopic data indicated that silk I is a hydrated structure and a rough estimate of the number of water molecules lost by the structure upon converting from silk I to silk II has been made, and found to be about 2.2 per [GAGAGS] hexapeptide. In Chapter 3, wet-spinning of osmotically stressed, regenerated silk fibroin was performed, based on the prediction that the enhanced control over structure and phase behavior using osmotic stress method helps improve the physical properties of wet-spun regenerated silk fibroin fibers. The osmotic stress was applied in order to pre-structure the regenerated silk fibroin molecule from its original random coil state to more oriented state, manipulating the phase of the silk solution in the phase diagram before the start of spinning. Monofilament fiber with a diameter of 20 microm was produced. In Chapter 4, we investigated if there is a noticeable synergistic osmotic pressure increase between co-existing polymeric osmolyte and salt when extremely highly concentrated salt molecules are present both at sample subphase and stressing subphase, as is the case of silk fibroin self-assembly. The equilibration method that measures osmotic pressure relative to a reference with known osmotic pressure was introduced. Osmotic pressure of aqueous LiBr solution up to 2.75M was measured and it was found that the synergistic effect was insignificant up to this salt concentration. Solution parameters of stressing solutions and Arrhenius kinetics based on time-temperature relationship for the equilibration process were derived as well. In Chapter 5, self-assembly behavior of natural silk fibroin within the gland of Bombyx mori silkworm was investigated using osmotic stress technique. Microscopic and thermodynamic details of this self-assembly process along the spinline have been assessed. Formation of a needle-shaped molecular lath under appropriate osmotic stress was found. Silk I degree of hydration of silk gland was quantitatively estimated by image analysis of optical micrographs and the numbers varied from 2.2 to 2.7 depending on the region in the gland. Osmotic pressure in the gland was also estimated by equilibration method.

Proteomic Analysis of Silk Viability in Maize Inbred Lines and Their Corresponding Hybrids

PubMed Central

Wang, Yafei; Zhao, Xiaofeng; Zhang, Fangfang; Tang, Jihua; Fu, Zhiyuan

2015-01-01

A long period of silk viability is critical for a good seed setting rate in maize (Zea mays L.), especially for inbred lines and hybrids with a long interval between anthesis and silking. To explore the molecular mechanism of silk viability and its heterosis, three inbred lines with different silk viability characteristics (Xun928, Lx9801, and Zong3) and their two hybrids (Xun928×Zong3 and Lx9801×Zong3) were analyzed at different developmental stages by a proteomic method. The differentially accumulated proteins were identified by mass spectrometry and classified into metabolism, protein biosynthesis and folding, signal transduction and hormone homeostasis, stress and defense responses, and cellular processes. Proteins involved in nutrient (methionine) and energy (ATP) supply, which support the pollen tube growth in the silk, were important for silk viability and its heterosis. The additive and dominant effects at a single locus, as well as complex epistatic interactions at two or more loci in metabolic pathways, were the primary contributors for mid-parent heterosis of silk viability. Additionally, the proteins involved in the metabolism of anthocyanins, which indirectly negatively regulate local hormone accumulation, were also important for the mid-parent heterosis of silk viability. These results also might imply the developmental dependence of heterosis, because many of the differentially accumulated proteins made distinct contributions to the heterosis of silk viability at specific developmental stages. PMID:26630375

Proteomic Analysis of Silk Viability in Maize Inbred Lines and Their Corresponding Hybrids.

PubMed

Ma, Zhihui; Qin, Yongtian; Wang, Yafei; Zhao, Xiaofeng; Zhang, Fangfang; Tang, Jihua; Fu, Zhiyuan

2015-01-01

A long period of silk viability is critical for a good seed setting rate in maize (Zea mays L.), especially for inbred lines and hybrids with a long interval between anthesis and silking. To explore the molecular mechanism of silk viability and its heterosis, three inbred lines with different silk viability characteristics (Xun928, Lx9801, and Zong3) and their two hybrids (Xun928×Zong3 and Lx9801×Zong3) were analyzed at different developmental stages by a proteomic method. The differentially accumulated proteins were identified by mass spectrometry and classified into metabolism, protein biosynthesis and folding, signal transduction and hormone homeostasis, stress and defense responses, and cellular processes. Proteins involved in nutrient (methionine) and energy (ATP) supply, which support the pollen tube growth in the silk, were important for silk viability and its heterosis. The additive and dominant effects at a single locus, as well as complex epistatic interactions at two or more loci in metabolic pathways, were the primary contributors for mid-parent heterosis of silk viability. Additionally, the proteins involved in the metabolism of anthocyanins, which indirectly negatively regulate local hormone accumulation, were also important for the mid-parent heterosis of silk viability. These results also might imply the developmental dependence of heterosis, because many of the differentially accumulated proteins made distinct contributions to the heterosis of silk viability at specific developmental stages.

Influence of spider silk on refugia preferences of the recluse spiders Loxosceles reclusa and Loxosceles laeta (Araneae: Sicariidae).

PubMed

Vetter, Richard S; Rust, Michael K

2010-06-01

In a previous experimental study, recluse spiders Loxosceles reclusa Gertsch and Mulaik and Loxosceles laeta (Nicolet) (Araneae: Sicariidae) preferred small cardboard refugia covered with conspecific silk compared with never-occupied refugia. Herein, we investigated some factors that might be responsible for this preference using similar cardboard refugia. When the two Loxosceles species were given choices between refugia previously occupied by their own and by the congeneric species, neither showed a species-specific preference; however, each chose refugia coated with conspecific silk rather than those previously inhabited by a distantly related cribellate spider, Metaltella simoni (Keyserling). When L. laeta spiders were offered refugia that were freshly removed from silk donors compared with heated, aged refugia from the same silk donor, older refugia were preferred. Solvent extracts of L. laeta silk were chosen approximately as often as control refugia when a range of solvents (methylene chloride:methanol, water, and hexane) were used. However, when acetone was used on similar silk, there was a statistical preference for the control, indicating that there might be a mildly repellent aspect to acetone-washed silk. Considering the inability to show attraction to chemical aspects of fresh silk, it seems that physical attributes may be more important for selection and that there might be repellency to silk of a recently vacated spider. These findings are discussed in regard to pest management strategies to control recluse spiders.

Novel silk fibroin films prepared by formic acid/hydroxyapatite dissolution method.

PubMed

Ming, Jinfa; Liu, Zhi; Bie, Shiyu; Zhang, Feng; Zuo, Baoqi

2014-04-01

Bombyx mori silk fibroin from the silkworm was firstly found to be soluble in formic acid/hydroxyapatite system. The rheological behavior of silk fibroin solution was significantly influenced by HAp contents in dissolved solution. At the same time, silk fibroin nanofibers were observed in dissolved solution with 103.6±20.4nm in diameter. Moreover, the structure behavior of SF films prepared by formic acid/hydroxyapatite dissolution method was examined. The secondary structure of silk fibroin films was attributed to silk II structure (β-sheet), indicating that the hydroxyapatite contents in dissolved solution were not significantly affected by the structure of silk fibroin. The X-ray diffraction results exhibited obviously hydroxyapatite crystalline nature existing in silk fibroin films; however, when the hydroxyapatite content was 5.0wt.% in dissolved solution, some hydroxyapatite crystals were converted to calcium hydrogen phosphate dehydrate in silk fibroin dissolution process. This result was also confirmed by Fourier transform infrared analysis and DSC measurement. In addition, silk fibroin films prepared by this dissolution method had higher breaking strength and extension at break. Based on these analyses, an understanding of novel SF dissolution method may provide an additional tool for designing and synthesizing advanced materials with more complex structures, which should be helpful in different fields, including biomaterial applications. Copyright © 2014 Elsevier B.V. All rights reserved.

Preparation and characterization of silk fibroin as a biomaterial with potential for drug delivery

PubMed Central

2012-01-01

Background Degummed silk fibroin from Bombyx mori (silkworm) has potential carrier capabilities for drug delivery in humans; however, the processing methods have yet to be comparatively analyzed to determine the differential effects on the silk protein properties, including crystalline structure and activity. Methods In this study, we treated degummed silk with four kinds of calcium-alcohol solutions, and performed secondary structure measurements and enzyme activity test to distinguish the differences between the regenerated fibroins and degummed silk fibroin. Results Gel electrophoresis analysis revealed that Ca(NO3)2-methanol, Ca(NO3)2-ethanol, or CaCl2-methanol treatments produced more lower molecular weights of silk fibroin than CaCl2-ethanol. X-ray diffraction and Fourier-transform infrared spectroscopy showed that CaCl2-ethanol produced a crystalline structure with more silk I (α-form, type II β-turn), while the other treatments produced more silk II (β-form, anti-parallel β-pleated sheet). Solid-State 13C cross polarization and magic angle spinning-nuclear magnetic resonance measurements suggested that regenerated fibroins from CaCl2-ethanol were nearly identical to degummed silk fibroin, while the other treatments produced fibroins with significantly different chemical shifts. Finally, enzyme activity test indicated that silk fibroins from CaCl2-ethanol had higher activity when linked to a known chemotherapeutic drug, L-asparaginase, than the fibroins from other treatments. Conclusions Collectively, these results suggest that the CaCl2-ethanol processing method produces silk fibroin with biomaterial properties that are appropriate for drug delivery. PMID:22676291

Tough silk fibers prepared in air using a biomimetic microfluidic chip.

PubMed

Luo, Jie; Zhang, Lele; Peng, Qingfa; Sun, Mengjie; Zhang, Yaopeng; Shao, Huili; Hu, Xuechao

2014-05-01

Microfluidic chips with single channel were built to mimic the shear and elongation conditions in the spinning apparatus of spider and silkworm. Silk fibers dry-spun from regenerated silk fibroin (RSF) aqueous solution using the chip could be tougher than degummed natural silk. The artificial silk exhibited a breaking strength up to 614 MPa, a breaking elongation up to 27% and a breaking energy of 101 kJ/kg. Copyright © 2014 Elsevier B.V. All rights reserved.

Solubilization of spider silk proteins and its structural analysis using Fourier transform infrared spectroscopy

NASA Astrophysics Data System (ADS)

Osbin, K.; Jayan, Manuel; Bhadrakumari, S.; Predeep, P.

2017-06-01

This study investigates the presence of various amide bands present in different spider silk species, which provides extraordinary physical properties. Three different spider silks were collected from Western Ghats region. The collected spider silks samples belonging to the spider Heteropoda venatoria (species 1), Hersilia savignyi (species 2) and Pholcus phalangioides (species 3). Fourier transform infrared (FTIR) spectra reveals the protein peaks in the amide I, II, and III regions in all the three types of spider silk species.

Development of new smart materials and spinning systems inspired by natural silks and their applications

NASA Astrophysics Data System (ADS)

Cheng, Jie; Lee, Sang-Hoon

2015-12-01

Silks produced by spiders and silkworms are charming natural biological materials with highly optimized hierarchical structures and outstanding physicomechanical properties. The superior performance of silks relies on the integration of a unique protein sequence, a distinctive spinning process, and complex hierarchical structures. Silks have been prepared to form a variety of morphologies and are widely used in diverse applications, for example, in the textile industry, as drug delivery vehicles, and as tissue engineering scaffolds. This review presents an overview of the organization of natural silks, in which chemical and physical functions are optimized, as well as a range of new materials inspired by the desire to mimic natural silk structure and synthesis.

Effect of residual sericin on the structural characteristics and properties of regenerated silk films.

PubMed

Lee, Ji Hye; Song, Dae Woong; Park, Young Hwan; Um, In Chul

2016-08-01

Regenerated silk film has been increasingly attracting the research community's attention for biomedical applications due to its good biocompatibility and excellent cyto-compatibility. However, some limitations regarding its mechanical properties, such as brittleness, have restricted the use of silk films for industrial biomedical applications. In this study, regenerated silk films with different residual sericin content were prepared applying controlled degumming conditions to evaluate the effect of sericin content on the structure and properties of the films generated. When the residual sericin content increased to 0.6%, crystallinity index and breaking strength of silk films were increased. Above this value, these parameters then decreased. A 1.5 fold increase of silk film elongation properties was obtained when incorporating 16% sericin. Regardless of sericin content, all regenerated silk films showed excellent cyto-compatibility, comparable to the one obtained with tissue culture plates. Copyright © 2016 Elsevier B.V. All rights reserved.

Protective effect of silk lutein on ultraviolet B-irradiated human keratinocytes.

PubMed

Pongcharoen, Sutatip; Warnnissorn, Prateep; Leŗtkajornsin, Ongart; Limpeanchob, Nanteetip; Sutheerawattananonda, Manote

2013-01-01

Carotenoids are efficient antioxidants that are of great importance for human health. Lutein and zeaxanthin are carotinoids present in high concentrations in the human retina which are involved in the photoprotection of the human eye. Lutein may also protect the skin from ultraviolet (UV)-induced damage. The present study investigated the protective effect of lutein extracted from yellow silk cocoons of Bombyx mori on human keratinocytes against UVB irradiation. A human keratinocyte cell line and primary human keratinocytes were used to investigate the UVB protection effects of silk lutein and plant lutein. Silk lutein showed no cytotoxicity to keratinocytes. Treatment with silk lutein prior to UVB irradiation enhanced cell viability and cell proliferation, and reduced cell apoptosis. The protective effects of silk lutein may be superior to those of plant lutein. Silk lutein may have a benefit for protection of keratinocytes against UVB-irradiation.

Spider genomes provide insight into composition and evolution of venom and silk

PubMed Central

Sanggaard, Kristian W.; Bechsgaard, Jesper S.; Fang, Xiaodong; Duan, Jinjie; Dyrlund, Thomas F.; Gupta, Vikas; Jiang, Xuanting; Cheng, Ling; Fan, Dingding; Feng, Yue; Han, Lijuan; Huang, Zhiyong; Wu, Zongze; Liao, Li; Settepani, Virginia; Thøgersen, Ida B.; Vanthournout, Bram; Wang, Tobias; Zhu, Yabing; Funch, Peter; Enghild, Jan J.; Schauser, Leif; Andersen, Stig U.; Villesen, Palle; Schierup, Mikkel H; Bilde, Trine; Wang, Jun

2014-01-01

Spiders are ecologically important predators with complex venom and extraordinarily tough silk that enables capture of large prey. Here we present the assembled genome of the social velvet spider and a draft assembly of the tarantula genome that represent two major taxonomic groups of spiders. The spider genomes are large with short exons and long introns, reminiscent of mammalian genomes. Phylogenetic analyses place spiders and ticks as sister groups supporting polyphyly of the Acari. Complex sets of venom and silk genes/proteins are identified. We find that venom genes evolved by sequential duplication, and that the toxic effect of venom is most likely activated by proteases present in the venom. The set of silk genes reveals a highly dynamic gene evolution, new types of silk genes and proteins, and a novel use of aciniform silk. These insights create new opportunities for pharmacological applications of venom and biomaterial applications of silk. PMID:24801114

Adhesion modulation using glue droplet spreading in spider capture silk

PubMed Central

Zhang, Ci; Blackledge, Todd A.

2017-01-01

Orb web spiders use sticky capture spiral silk to retain prey in webs. Capture spiral silk is composed of an axial fibre of flagelliform silk covered with glue droplets that are arranged in a beads-on-a-string morphology that allows multiple droplets to simultaneously extend and resist pull off. Previous studies showed that the adhesion of capture silk is responsive to environmental humidity, increasing up to an optimum humidity that varied among different spider species. The maximum adhesion was hypothesized to occur when the viscoelasticity of the glue optimized contributions from glue spreading and bulk cohesion. In this study, we show how glue droplet shape during peeling contributes significantly to capture silk adhesion. Both overspreading and underspreading of glue droplets reduces adhesion through changes in crack propagation and failure regime. Understanding the mechanism of stimuli-responsive adhesion of spider capture silk will lead to new designs for smarter adhesives. PMID:28490605

Uptake of atmospheric carbon dioxide into silk fiber by silkworms.

PubMed

Magoshi, Jun; Tanaka, Toshihisa; Sasaki, Haruto; Kobayashi, Masatoshi; Magoshi, Yoshiko; Tsuda, Hidetoshi; Becker, Mary A; Inoue, Shun-ichi; Ishimaru, Ken

2003-01-01

The relation between the uptake of atmospheric CO(2) and insect's production of silk fiber has not yet been reported. Here, we provide the first quantitative demonstrations that four species of silkworms (Bombyx mori, Samia cynthia ricini, Antheraea pernyi, and Antheraea yamamai) and a silk-producing spider (Nephila clavata) incorporate atmospheric CO(2) into their silk fibers. The abundance of (13)C incorporated from the environment was determined by mass spectrometry and (13)C NMR measurements. Atmospheric CO(2) was incorporated into the silk fibers in the carbonyl groups of alanine, aspartic acid, serine, and glycine and the C(gamma) of aspartic acid. We show a simple model for the uptake of atmospheric CO(2) by silkworms. These results will demonstrate that silkworm has incorporated atmospheric CO(2) into silk fiber via the TCA cycle; however, the magnitude of uptake into the silk fibers is smaller than that consumed by the photosynthesis in trees and coral reefs.

Synergistic adhesion mechanisms of spider capture silk.

PubMed

Guo, Yang; Chang, Zheng; Guo, Hao-Yuan; Fang, Wei; Li, Qunyang; Zhao, Hong-Ping; Feng, Xi-Qiao; Gao, Huajian

2018-03-01

It is well known that capture silk, the main sticky component of the orb web of a spider, plays an important role in the spider's ability to capture prey via adhesion. However, the detailed mechanism with which the spider achieves its unparalleled high-adhesion performance remains elusive. In this work, we combine experiments and theoretical analysis to investigate the adhesion mechanisms of spider silk. In addition to the widely recognized adhesion effect of the sticky glue, we reveal a synergistic enhancement mechanism due to the elasticity of silk fibres. A balance between silk stiffness, strength and glue stickiness is crucial to endow the silk with superior adhesion, as well as outstanding energy absorption capacity and structural robustness. The revealed mechanisms deepen our understanding of the working principles of spider silk and suggest guidelines for biomimetic designs of spider-inspired adhesion and capture devices. © 2018 The Author(s).

Silk micrococoons for protein stabilisation and molecular encapsulation

NASA Astrophysics Data System (ADS)

Shimanovich, Ulyana; Ruggeri, Francesco S.; de Genst, Erwin; Adamcik, Jozef; Barros, Teresa P.; Porter, David; Müller, Thomas; Mezzenga, Raffaele; Dobson, Christopher M.; Vollrath, Fritz; Holland, Chris; Knowles, Tuomas P. J.

2017-07-01

Naturally spun silks generate fibres with unique properties, including strength, elasticity and biocompatibility. Here we describe a microfluidics-based strategy to spin liquid native silk, obtained directly from the silk gland of Bombyx mori silkworms, into micron-scale capsules with controllable geometry and variable levels of intermolecular β-sheet content in their protein shells. We demonstrate that such micrococoons can store internally the otherwise highly unstable liquid native silk for several months and without apparent effect on its functionality. We further demonstrate that these native silk micrococoons enable the effective encapsulation, storage and release of other aggregation-prone proteins, such as functional antibodies. These results show that native silk micrococoons are capable of preserving the full activity of sensitive cargo proteins that can aggregate and lose function under conditions of bulk storage, and thus represent an attractive class of materials for the storage and release of active biomolecules.

Adhesion modulation using glue droplet spreading in spider capture silk.

PubMed

Amarpuri, Gaurav; Zhang, Ci; Blackledge, Todd A; Dhinojwala, Ali

2017-05-01

Orb web spiders use sticky capture spiral silk to retain prey in webs. Capture spiral silk is composed of an axial fibre of flagelliform silk covered with glue droplets that are arranged in a beads-on-a-string morphology that allows multiple droplets to simultaneously extend and resist pull off. Previous studies showed that the adhesion of capture silk is responsive to environmental humidity, increasing up to an optimum humidity that varied among different spider species. The maximum adhesion was hypothesized to occur when the viscoelasticity of the glue optimized contributions from glue spreading and bulk cohesion. In this study, we show how glue droplet shape during peeling contributes significantly to capture silk adhesion. Both overspreading and underspreading of glue droplets reduces adhesion through changes in crack propagation and failure regime. Understanding the mechanism of stimuli-responsive adhesion of spider capture silk will lead to new designs for smarter adhesives. © 2017 The Author(s).

The potential of silk and silk-like proteins as natural mucoadhesive biopolymers for controlled drug delivery

NASA Astrophysics Data System (ADS)

Brooks, Amanda

2015-11-01

Drug delivery across mucus membranes is a particularly effective route of administration due to the large surface area. However, the unique environment present at the mucosa necessitates altered drug formulations designed to (1) deliver sensitive biologic molecules, (2) promote intimate contact between the mucosa and the drug, and (3) prolong the drug’s local residence time. Thus, the pharmaceutical industry has an interest in drug delivery systems formulated around the use of mucoadhesive polymers. Mucoadhesive polymers, both synthetic and biological, have a history of use in local drug delivery. Prominently featured in the literature are chitosan, alginate, and cellulose derivatives. More recently, silk and silk-like derivatives have been explored for their potential as mucoadhesive polymers. Both silkworms and spiders produce sticky silk-like glue substances, sericin and aggregate silk respectively, that may prove an effective, natural matrix for drug delivery to the mucosa. This mini review will explore the potential of silk and silk-like derivatives as a biocompatible mucoadhesive polymer matrix for local controlled drug delivery.

Silk scaffolds with tunable mechanical capability for cell differentiation

PubMed Central

Bai, Shumeng; Han, Hongyan; Huang, Xiaowei; Xu, Weian; Kaplan, David L.; Zhu, Hesun; Lu, Qiang

2015-01-01

Bombyx mori silk fibroin is a promising biomaterial for tissue regeneration and is usually considered an “inert” material with respect to actively regulating cell differentiation due to few specific cell signaling peptide domains in the primary sequence and the generally stiffer mechanical properties due to crystalline content formed in processing. In the present study, silk fibroin porous 3D scaffolds with nanostructures and tunable stiffness were generated via a silk fibroin nanofiber-assisted lyophilization process. The silk fibroin nanofibers with high β-sheet content were added into the silk fibroin solutions to modulate the self-assembly, and to directly induce water-insoluble scaffold formation after lyophilization. Unlike previously reported silk fibroin scaffold formation processes, these new scaffolds had lower overall β-sheet content and softer mechanical properties for improved cell compatibility. The scaffold stiffness could be further tuned to match soft tissue mechanical properties, which resulted in different differentiation outcomes with rat bone marrow-derived mesenchymal stem cells towards myogenic and endothelial cells, respectively. Therefore, these silk fibroin scaffolds regulate cell differentiation outcomes due to their mechanical features. PMID:25858557

Electrophoretic deposition of tetracycline modified silk fibroin coatings for functionalization of titanium surfaces

NASA Astrophysics Data System (ADS)

Zhang, Zhen; Qu, Yinying; Li, Xiaoshuang; Zhang, Sheng; Wei, Qingsong; Shi, Yusheng; Chen, Lili

2014-06-01

Electrophoretic deposition has been widely used for the fabrication of functional coatings onto metal implant. A characteristic feature of this process is that positively charged materials migrate toward the cathode and can deposit on it. In this study, silk fibroin was decorated with tetracycline in aqueous solution to impart positive charge, and then deposited on negatively titanium cathode under certain electric field. The characterization of the obtained coatings indicated that the intermolecular hydrogen bonds formed between the backbone of silk fibroin and tetracycline molecular. In vitro biological tests demonstrated that osteoblast-like cells achieved acceptable cell affinity on the tetracycline cross-linked silk fibroin coatings, although greater cell viability was seen on pure silk fibroin coatings. The cationic silk fibroin coatings showed remarkable antibacterial activity against gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli) bacteria. Therefore, we concluded that electrophoretic deposition was an effective and efficient technique to prepare cationic silk fibroin coatings on the titanium surface and that cationic silk fibroin coatings with acceptable biocompatibility and antibacterial property were promising candidates for further loading of functional agents.

Effects of silk fibroin in murine dry eye

NASA Astrophysics Data System (ADS)

Kim, Chae Eun; Lee, Ji Hyun; Yeon, Yeung Kyu; Park, Chan Hum; Yang, Jaewook

2017-03-01

The study aimed to investigate the effects of silk fibroin in a mouse model of dry eye. The experimental dry eye mouse model was developed using more than twelve-weeks-old NOD.B10.H2b mice exposing them to 30-40% ambient humidity and injecting them with scopolamine hydrobromide for 10 days. Tear production and corneal irregularity score were measured by the instillation of phosphate buffered saline or silk fibroin. Corneal detachment and conjunctival goblet cell density were observed by hematoxylin and eosin or periodic acid Schiff staining in the cornea or conjunctiva. The expression of inflammatory markers was detected by immunohistochemistry in the lacrimal gland. The silk group tear production was increased, and corneal smoothness was improved. The corneal epithelial cells and conjunctival goblet cells were recovered in the silk groups. The expression of inflammatory factors was inhibited in the lacrimal gland of the silk group. These results show that silk fibroin improved the cornea, conjunctiva, and lacrimal gland in the mouse model of dry eye. These findings suggest that silk fibroin has anti-inflammatory effects in the experimental models of dry eye.

Infrared and Raman Study of the Recluse Spider Silk

NASA Astrophysics Data System (ADS)

Wang, S. L.; Wang, Qijue; Xing, Zhen; Schniepp, H. C.; Qazilbash, M. M.

Spider silk exhibits remarkable mechanical properties, such as high tensile strength and toughness. We want to gain insight into the composition and structure of spider silk to discover the origin of these properties. We are especially interested in the organization of the crystalline beta sheets that are expected to contribute to the high strength of the silk from the recluse spider, Loxosceles laeta. The recluse spider produces a silk that has a unique geometry amongst arachnids. We measure the silk's optical properties, particularly the infrared-active and Raman-active vibrations. Broadband infrared transmission spectra were collected in the spectral range between 600 cm-1 and 4000 cm-1, with light polarized parallel and perpendicular to the long axis of the silk. Raman micro-spectroscopy was performed in the spectral range 500 cm-1 and 4000 cm- 1 with a 514 nm laser. The infrared and Raman vibrational modes are fit with Lorentzian and pseudo-Voigt functions. The vibrational modes are assigned to specific structures and electronic bonds in the silk. This work was supported by NASA/ Virginia Space Grant Consortium.

Characteristics of platelet gels combined with silk

PubMed Central

Pallotta, Isabella; Kluge, Jonathan A.; Moreau, Jodie; Calabrese, Rossella

2014-01-01

Platelet gel, a fibrin network containing activated platelets, is widely used in regenerative medicine due the capacity of platelet-derived growth factors to accelerate and direct healing processes. However, limitations to this approach include poor mechanical properties, relatively rapid degradation, and the lack of control of release of growth factors at the site of injection. These issues compromise the ability of platelet gels for sustained function in regenerative medicine. In the present study, a combination of platelet gels with silk fibroin gel was studied to address the above limitations. Mixing sonicated silk gels with platelet gels extended the release of growth factors without inhibiting gel forming ability. The released growth factors were biologically active and their delivery was modified further by manipulation of the charge of the silk protein. Moreover, the silk gel augmented both the rheological properties and compressive stiffness of the platelet gel, tuned by the silk concentration and/or silk/platelet gel ratio. Silk-platelet gel injections in nude rats supported enhanced cell infiltration and blood vessel formation representing a step towards new platelet gel formulations with enhanced therapeutic impact. PMID:24480538

Silk Electrogel Based Gastroretentive Drug Delivery System

NASA Astrophysics Data System (ADS)

Wang, Qianrui

Gastric cancer has become a global pandemic and there is imperative to develop efficient therapies. Oral dosing strategy is the preferred route to deliver drugs for treating the disease. Recent studies suggested silk electro hydrogel, which is pH sensitive and reversible, has potential as a vehicle to deliver the drug in the stomach environment. The aim of this study is to establish in vitro electrogelation e-gel based silk gel as a gastroretentive drug delivery system. We successfully extended the duration of silk e-gel in artificial gastric juice by mixing silk solution with glycerol at different ratios before the electrogelation. Structural analysis indicated the extended duration was due to the change of beta sheet content. The glycerol mixed silk e-gel had good doxorubicin loading capability and could release doxorubicin in a sustained-release profile. Doxorubicin loaded silk e-gels were applied to human gastric cancer cells. Significant cell viability decrease was observed. We believe that with further characterization as well as functional analysis, the silk e-gel system has the potential to become an effective vehicle for gastric drug delivery applications.

Milled non-mulberry silk fibroin microparticles as biomaterial for biomedical applications.

PubMed

Bhardwaj, Nandana; Rajkhowa, Rangam; Wang, Xungai; Devi, Dipali

2015-11-01

Silk fibroin has been widely employed in various forms as biomaterials for biomedical applications due to its superb biocompatibility and tunable degradation and mechanical properties. Herein, silk fibroin microparticles of non-mulberry silkworm species (Antheraea assamensis, Antheraea mylitta and Philosamia ricini) were fabricated via a top-down approach using a combination of wet-milling and spray drying techniques. Microparticles of mulberry silkworm (Bombyx mori) were also utilized for comparative studies. The fabricated microparticles were physico-chemically characterized for size, stability, morphology, chemical composition and thermal properties. The silk fibroin microparticles of all species were porous (∼5μm in size) and showed nearly spherical morphology with rough surface as revealed from dynamic light scattering and microscopic studies. Non-mulberry silk microparticles maintained the typical silk-II structure with β-sheet secondary conformation with higher thermal stability. Additionally, non-mulberry silk fibroin microparticles supported enhanced cell adhesion, spreading and viability of mouse fibroblasts than mulberry silk fibroin microparticles (p<0.001) as evidenced from fluorescence microscopy and cytotoxicity studies. Furthermore, in vitro drug release from the microparticles showed a significantly sustained release over 3 weeks. Taken together, this study demonstrates promising attributes of non-mulberry silk fibroin microparticles as a potential drug delivery vehicle/micro carrier for diverse biomedical applications. Copyright © 2015 Elsevier B.V. All rights reserved.

Influence of pH, temperature, and concentration on stabilization of aqueous hornet silk solution and fabrication of salt-free materials.

PubMed

Kameda, Tsunenori

2015-01-01

We found that an aqueous solution of silk from cocoons produced by hornet larvae (hornet silk) can be obtained when the solution is adjusted to basic conditions of pH > 9.2. It is known that native hornet cocoons can be dissolved in concentrated aqueous solution of salts, such as lithium bromide (LiBr) and calcium chloride (CaCl2). Upon the removal of these salts from solution by dialysis, solidification, gelation, or sedimentation of hornet silk is known to occur. In the present study, under basic conditions, however, no such solidification occurred, even after salt removal. In this study, ammonia was used for alkalization of solution because it is volatilized during the casting process and pure hornet silk materials can be obtained after drying. The effects of the concentrations of hornet silk and ammonia, as well as dialysis temperature, on preventing gelation during dialysis were investigated. Dialysis conditions that limit the degradation of hornet silk by hydrolysis in alkali solution were identified. Moreover, casting conditions to prepare flexible and transparent hornet silk film from aqueous ammonia solution were optimized. Molecular structural analysis of hornet silk in aqueous ammonia solution and cast film indicated the formation of α-helix conformations. © 2014 Wiley Periodicals, Inc.

Distinct spinning patterns gain differentiated loading tolerance of silk thread anchorages in spiders with different ecology.

PubMed

Wolff, Jonas O; van der Meijden, Arie; Herberstein, Marie E

2017-07-26

Building behaviour in animals extends biological functions beyond bodies. Many studies have emphasized the role of behavioural programmes, physiology and extrinsic factors for the structure and function of buildings. Structure attachments associated with animal constructions offer yet unrealized research opportunities. Spiders build a variety of one- to three-dimensional structures from silk fibres. The evolution of economic web shapes as a key for ecological success in spiders has been related to the emergence of high performance silks and thread coating glues. However, the role of thread anchorages has been widely neglected in those models. Here, we show that orb-web (Araneidae) and hunting spiders (Sparassidae) use different silk application patterns that determine the structure and robustness of the joint in silk thread anchorages. Silk anchorages of orb-web spiders show a greater robustness against different loading situations, whereas the silk anchorages of hunting spiders have their highest pull-off resistance when loaded parallel to the substrate along the direction of dragline spinning. This suggests that the behavioural 'printing' of silk into attachment discs along with spinneret morphology was a prerequisite for the evolution of extended silk use in a three-dimensional space. This highlights the ecological role of attachments in the evolution of animal architectures. © 2017 The Author(s).

Silk-Based Biomaterials for Sustained Drug Delivery

PubMed Central

Yucel, Tuna; Lovett, Michael L.; Kaplan, David L.

2014-01-01

Silk presents a rare combination of desirable properties for sustained drug delivery, including aqueous-based purification and processing options without chemical cross-linkers, compatibility with common sterilization methods, controllable and surface-mediated biodegradation into non-inflammatory by-products, biocompatibility, utility in drug stabilization, and robust mechanical properties. A versatile silk-based toolkit is currently available for sustained drug delivery formulations of small molecule through macromolecular drugs, with a promise to mitigate several drawbacks associated with other degradable sustained delivery technologies in the market. Silk-based formulations utilize silk’s well-defined nano- through microscale structural hierarchy, stimuli-responsive self-assembly pathways and crystal polymorphism, as well as sequence and genetic modification options towards targeted pharmaceutical outcomes. Furthermore, by manipulating the interactions between silk and drug molecules, near-zero order sustained release may be achieved through diffusion- and degradation-based release mechanisms. Because of these desirable properties, there has been increasing industrial interest in silk-based drug delivery systems currently at various stages of the developmental pipeline from pre-clinical to FDA-approved products. Here, we discuss the unique aspects of silk technology as a sustained drug delivery platform and highlight the current state of the art in silk-based drug delivery. We also offer a potential early development pathway for silk-based sustained delivery products. PMID:24910193

Mechanical properties of silk of the Australian golden orb weavers Nephila pilipes and Nephilaplumipes.

PubMed

Kerr, Genevieve G; Nahrung, Helen F; Wiegand, Aaron; Kristoffersen, Joanna; Killen, Peter; Brown, Cameron; Macdonald, Joanne

2018-02-22

Silks from orb-weaving spiders are exceptionally tough, producing a model polymer for biomimetic fibre development. The mechanical properties of naturally spun silk threads from two species of Australian orb-weavers, Nephila pilipes and Nephila plumipes , were examined here in relation to overall thread diameter, the size and number of fibres within threads, and spider size. N. pilipes , the larger of the two species, had significantly tougher silk with higher strain capacity than its smaller congener, producing threads with average toughness of 150 MJ m -3 , despite thread diameter, mean fibre diameter and number of fibres per thread not differing significantly between the two species. Within N. pilipes , smaller silk fibres were produced by larger spiders, yielding tougher threads. In contrast, while spider size was correlated with thread diameter in N. plumipes , there were no clear patterns relating to silk toughness, which suggests that the differences in properties between the silk of the two species arise through differing molecular structure. Our results support previous studies that found that the mechanical properties of silk differ between distantly related spider species, and extends on that work to show that the mechanical and physical properties of silk from more closely related species can also differ remarkably. © 2018. Published by The Company of Biologists Ltd.

Formulation of Biologically-Inspired Silk-Based Drug Carriers for Pulmonary Delivery Targeted for Lung Cancer

PubMed Central

Kim, Sally Yunsun; Naskar, Deboki; Kundu, Subhas C.; Bishop, David P.; Doble, Philip A.; Boddy, Alan V.; Chan, Hak-Kim; Wall, Ivan B.; Chrzanowski, Wojciech

2015-01-01

The benefits of using silk fibroin, a major protein in silk, are widely established in many biomedical applications including tissue regeneration, bioactive coating and in vitro tissue models. The properties of silk such as biocompatibility and controlled degradation are utilized in this study to formulate for the first time as carriers for pulmonary drug delivery. Silk fibroin particles are spray dried or spray-freeze-dried to enable the delivery to the airways via dry powder inhalers. The addition of excipients such as mannitol is optimized for both the stabilization of protein during the spray-freezing process as well as for efficient dispersion using an in vitro aerosolisation impactor. Cisplatin is incorporated into the silk-based formulations with or without cross-linking, which show different release profiles. The particles show high aerosolisation performance through the measurement of in vitro lung deposition, which is at the level of commercially available dry powder inhalers. The silk-based particles are shown to be cytocompatible with A549 human lung epithelial cell line. The cytotoxicity of cisplatin is demonstrated to be enhanced when delivered using the cross-linked silk-based particles. These novel inhalable silk-based drug carriers have the potential to be used as anti-cancer drug delivery systems targeted for the lungs. PMID:26234773

Silk-based biomaterials.

PubMed

Altman, Gregory H; Diaz, Frank; Jakuba, Caroline; Calabro, Tara; Horan, Rebecca L; Chen, Jingsong; Lu, Helen; Richmond, John; Kaplan, David L

2003-02-01

Silk from the silkworm, Bombyx mori, has been used as biomedical suture material for centuries. The unique mechanical properties of these fibers provided important clinical repair options for many applications. During the past 20 years, some biocompatibility problems have been reported for silkworm silk; however, contamination from residual sericin (glue-like proteins) was the likely cause. More recent studies with well-defined silkworm silk fibers and films suggest that the core silk fibroin fibers exhibit comparable biocompatibility in vitro and in vivo with other commonly used biomaterials such as polylactic acid and collagen. Furthermore, the unique mechanical properties of the silk fibers, the diversity of side chain chemistries for 'decoration' with growth and adhesion factors, and the ability to genetically tailor the protein provide additional rationale for the exploration of this family of fibrous proteins for biomaterial applications. For example, in designing scaffolds for tissue engineering these properties are particularly relevant and recent results with bone and ligament formation in vitro support the potential role for this biomaterial in future applications. To date, studies with silks to address biomaterial and matrix scaffold needs have focused on silkworm silk. With the diversity of silk-like fibrous proteins from spiders and insects, a range of native or bioengineered variants can be expected for application to a diverse set of clinical needs.

More than a safety line: jump-stabilizing silk of salticids.

PubMed

Chen, Yung-Kang; Liao, Chen-Pan; Tsai, Feng-Yueh; Chi, Kai-Jung

2013-10-06

Salticids are diurnal hunters known for acute vision, remarkable predatory strategies and jumping ability. Like other jumpers, they strive for stability and smooth landings. Instead of using inertia from swinging appendages or aerodynamic forces by flapping wings as in other organisms, we show that salticids use a different mechanism for in-air stability by using dragline silk, which was previously believed to function solely as a safety line. Analyses from high-speed images of jumps by the salticid Hasarius adansoni demonstrate that despite being subject to rearward pitch at take-off, spiders with dragline silk can change body orientation in the air. Instantaneous drag and silk forces calculated from kinematic data further suggest a comparable contribution to deceleration and energy dissipation, and reveal that adjustments by the spider to the silk force can reverse its body pitch for a predictable and optimal landing. Without silk, upright-landing spiders would slip or even tumble, deferring completion of landing. Thus, for salticids, dragline silk is critical for dynamic stability and prey-capture efficiency. The dynamic functioning of dragline silk revealed in this study can advance the understanding of silk's physiological control over material properties and its significance to spider ecology and evolution, and also provide inspiration for future manoeuvrable robot designs.

Enhancing the Mechanical Toughness of Epoxy-Resin Composites Using Natural Silk Reinforcements

DOE PAGES

Yang, Kang; Wu, Sujun; Guan, Juan; ...

2017-09-20

Strong and tough epoxy composites are developed using a less-studied fibre reinforcement, that of natural silk. Two common but structurally distinct silks from the domestic B. mori/Bm and the wild A. pernyi/Ap silkworms are selected in fabric forms. We show that the toughening effects on silk-epoxy composites or SFRPs are dependent on the silk species and the volume fraction of silk. Both silks enhance the room-temperature tensile and flexural mechanical properties of the composite, whereas the more resilient Ap silk shows a more pronounced toughening effect and a lower critical reinforcement volume for the brittle-ductile transition. Specifically, our 60 vol.%more » Ap-SFRP displays a three-fold elevation in tensile and flexural strength, as compared to pure epoxy resin, with an order of magnitude higher breaking energy via a distinct, ductile failure mode. Importantly, the 60 vol.% Ap-SFRP remains ductile with 7% flexural elongation at lower temperatures (-50 °C). Under impact, these SFRPs show significantly improved energy absorption, and the 60 vol.% Ap-SFRP has an impact strength some eight times that of pure epoxy resin. Lastly, the findings demonstrate both marked toughening and strengthening effects for epoxy composites from natural silk reinforcements, which presents opportunities for mechanically superior and "green" structural composites.« less

Accelerated In Vitro Degradation of Optically Clear Low β-Sheet Silk Films by Enzyme-Mediated Pretreatment

PubMed Central

Shang, Ke; Rnjak-Kovacina, Jelena; Lin, Yinan; Hayden, Rebecca S.; Tao, Hu; Kaplan, David L.

2013-01-01

Purpose: To design patterned, transparent silk films with fast degradation rates for the purpose of tissue engineering corneal stroma. Methods: β-sheet (crystalline) content of silk films was decreased significantly by using a short water annealing time. Additionally, a protocol combining short water annealing time with enzymatic pretreatment of silk films with protease XIV was developed. Results: Low β-sheet content (17%–18%) and enzymatic pretreatment provided film stability in aqueous environments and accelerated degradation of the silk films in the presence of human corneal fibroblasts in vitro. The results demonstrate a direct relationship between reduced β-sheet content and enzymatic pretreatment, and overall degradation rate of the protein films. Conclusions: The novel protocol developed here provides new approaches to modulate the regeneration rate of silk biomaterials for corneal tissue regeneration needs. Translational Relevance: Patterned silk protein films possess desirable characteristics for corneal tissue engineering, including optical transparency, biocompatibility, cell alignment, and tunable mechanical properties, but current fabrication protocols do not provide adequate degradation rates to match the regeneration properties of the human cornea. This novel processing protocol makes silk films more suitable for the construction of human corneal stroma tissue and a promising way to tune silk film degradation properties to match corneal tissue regeneration. PMID:24049717

Accelerated in vitro Degradation of Optically Clear Low β-sheet Silk Films by Enzyme-Mediated Pretreatment

PubMed Central

Shang, Ke; Rnjak-Kovacina, Jelena; Lin, Yinan; Hayden, Rebecca S.; Hu, Tao; Kaplan, David L.

2013-01-01

Purpose To design patterned, transparent silk films with fast degradation rates for the purpose of tissue engineering corneal stroma, Methods β-sheet (crystalline) content of silk films was decreased significantly by using a short water annealing time. Additionally, a protocol combining short water annealing time with enzymatic pretreatment of silk films with protease XIV was developed. Results Low β-sheet content (17–18%) and enzymatic pre-treatment provided film stability in aqueous environments and accelerated degradation of the silk films in the presence of human corneal fibroblasts in vitro. The results demonstrate a direct relationship between reduced β-sheet content and enzymatic pre-treatment and overall degradation rate of the protein films. Conclusions The novel protocol developed here provides new approaches to modulate the regeneration rate of silk biomaterials for corneal tissue regeneration needs. Translational relevance Patterned silk protein films possess desirable characteristics for corneal tissue engineering, including optical transparency, biocompatibility, cell alignment and tunable mechanical properties, but current fabrication protocols do not provide adequate degradation rates to match the regeneration properties of the human cornea. This novel processing protocol makes silk films more suitable for the construction of human corneal stroma tissue and a promising way to tune silk film degradation properties to match corneal tissue regeneration. PMID:23579493

More than a safety line: jump-stabilizing silk of salticids

PubMed Central

Chen, Yung-Kang; Liao, Chen-Pan; Tsai, Feng-Yueh; Chi, Kai-Jung

2013-01-01

Salticids are diurnal hunters known for acute vision, remarkable predatory strategies and jumping ability. Like other jumpers, they strive for stability and smooth landings. Instead of using inertia from swinging appendages or aerodynamic forces by flapping wings as in other organisms, we show that salticids use a different mechanism for in-air stability by using dragline silk, which was previously believed to function solely as a safety line. Analyses from high-speed images of jumps by the salticid Hasarius adansoni demonstrate that despite being subject to rearward pitch at take-off, spiders with dragline silk can change body orientation in the air. Instantaneous drag and silk forces calculated from kinematic data further suggest a comparable contribution to deceleration and energy dissipation, and reveal that adjustments by the spider to the silk force can reverse its body pitch for a predictable and optimal landing. Without silk, upright-landing spiders would slip or even tumble, deferring completion of landing. Thus, for salticids, dragline silk is critical for dynamic stability and prey-capture efficiency. The dynamic functioning of dragline silk revealed in this study can advance the understanding of silk's physiological control over material properties and its significance to spider ecology and evolution, and also provide inspiration for future manoeuvrable robot designs. PMID:23925983

Tuning chemical and physical cross-links in silk electrogels for morphological analysis and mechanical reinforcement.

PubMed

Lin, Yinan; Xia, Xiaoxia; Shang, Ke; Elia, Roberto; Huang, Wenwen; Cebe, Peggy; Leisk, Gary; Omenetto, Fiorenzo; Kaplan, David L

2013-08-12

Electrochemically controlled, reversible assembly of biopolymers into hydrogel structures is a promising technique for on-demand cell or drug encapsulation and release systems. An electrochemically sol-gel transition has been demonstrated in regenerated Bombyx mori silk fibroin, offering a controllable way to generate biocompatible and reversible adhesives and other biomedical materials. Despite the involvement of an electrochemically triggered electrophoretic migration of the silk molecules, the mechanism of the reversible electrogelation remains unclear. It is, however, known that the freshly prepared silk electrogels (e-gels) adopt a predominantly random coil conformation, indicating a lack of cross-linking as well as thermal, mechanical, and morphological stabilities. In the present work, the tuning of covalent and physical β-sheet cross-links in silk hydrogels was studied for programming the structural properties. Scanning electron microscopy (SEM) revealed delicate morphology, including locally aligned fibrillar structures, in silk e-gels, preserved by combining glutaraldehyde-cross-linking and ethanol dehydration. Fourier transform infrared (FTIR) spectroscopic analysis of either electrogelled, vortex-induced or spontaneously formed silk hydrogels showed that the secondary structure of silk e-gels was tunable between non-β-sheet-dominated and β-sheet-dominated states. Dynamic oscillatory rheology confirmed the mechanical reinforcement of silk e-gels provided by controlled chemical and physical cross-links. The selective incorporation of either chemical or physical or both cross-links into the electrochemically responsive, originally unstructured silk e-gel should help in the design for electrochemically responsive protein polymers.

Functional regeneration of ligament-bone interface using a triphasic silk-based graft.

PubMed

Li, Hongguo; Fan, Jiabing; Sun, Liguo; Liu, Xincheng; Cheng, Pengzhen; Fan, Hongbin

2016-11-01

The biodegradable silk-based scaffold with unique mechanical property and biocompatibility represents a favorable ligamentous graft for tissue-engineering anterior cruciate ligament (ACL) reconstruction. However, the low efficiency of ligament-bone interface restoration barriers the isotropic silk graft to common ACL therapeutics. To enhance the regeneration of the silk-mediated interface, we developed a specialized stratification approach implementing a sequential modification on isotropic silk to constitute a triphasic silk-based graft in which three regions respectively referring to ligament, cartilage and bone layers of interface were divided, followed by respective biomaterial coating. Furthermore, three types of cells including bone marrow mesenchymal stem cells (BMSCs), chondrocytes and osteoblasts were respectively seeded on the ligament, cartilage and bone region of the triphasic silk graft, and the cell/scaffold complex was rolled up as a multilayered graft mimicking the stratified structure of native ligament-bone interface. In vitro, the trilineage cells loaded on the triphasic silk scaffold revealed a high proliferative capacity as well as enhanced differentiation ability into their corresponding cell lineage. 24 weeks postoperatively after the construct was implanted to repair the ACL defect in rabbit model, the silk-based ligamentous graft exhibited the enhancement of osseointegration detected by a robust pullout force and formation of three-layered structure along with conspicuously corresponding matrix deposition via micro-CT and histological analysis. These findings potentially broaden the application of silk-based ligamentous graft for ACL reconstruction and further large animal study. Copyright © 2016 Elsevier Ltd. All rights reserved.

Morus planting and silk production in Oxus civilization (2000 BC), Transoxiana

NASA Astrophysics Data System (ADS)

Zhou, X.; Li, X.; Wang, J.

2017-12-01

Silk is the most important luxury in ancient trade, which promoted communications between east and west civilizations that facilitated the development of them. Currently, probably more than 99% of the silk in commerce in the world today comes from a single species called the silkworm or mulberry silk moth, Bombyx mori (L.), of the family Bombycidae. At present, a list of occurrences of unearthed early silk thread, textile and terracotta figures of China suggests that wild silk has been widely used for weave in Yangtze river and Yellow River basin at least 5000 cal yr BP. On the other hand, the earliest silk fabric out China is from the earliest civilization Harappa site (4500-4000 cal a BP) that confirmed the early use of wild silkworms in South Asia.. In addition, in the Egyptian Deir al Medina relics site, the unearthed silk also as old as nearly 3000 cal a BP, and a serials of pre-han silk also unearthed 3000-2500 cal a BP in Europe. But, the appearance of these out-China silk is usually considered to be the result of the early trade or wild silkmoth products. Here we present a synthesis study of chronology, entomology, protein group, the paleoethnobotany form three Bronze Age site (Sapalli, Jarzgudan, Molleli) concerning on the paleo environment, agriculture gardening, and the possible mulberry silkworm utilization in Bronze Age Tensoxiana 4000 cal a BP. Together with archaeobotany and chronology data from Xinjiang, Hexi corridor and the Loess Plateau in China, we analysis the status of the mulberry silk factory in Bronze Age in Transoxiana and it possible connection to ancient China.

Conferring biological activity to native spider silk: A biofunctionalized protein-based microfiber.

PubMed

Wu, Hsuan-Chen; Quan, David N; Tsao, Chen-Yu; Liu, Yi; Terrell, Jessica L; Luo, Xiaolong; Yang, Jen-Chang; Payne, Gregory F; Bentley, William E

2017-01-01

Spider silk is an extraordinary material with physical properties comparable to the best scaffolding/structural materials, and as a fiber it can be manipulated with ease into a variety of configurations. Our work here demonstrates that natural spider silk fibers can also be used to organize biological components on and in devices through rapid and simple means. Micron scale spider silk fibers (5-10 μm in diameter) were surface modified with a variety of biological entities engineered with pentaglutamine tags via microbial transglutaminase (mTG). Enzymes, enzyme pathways, antibodies, and fluorescent proteins were all assembled onto spider silk fibers using this biomolecular engineering/biofabrication process. Additionally, arrangement of biofunctionalized fiber should in of itself generate a secondary level of biomolecular organization. Toward this end, as proofs of principle, spatially defined arrangement of biofunctionalized spider silk fiber was shown to generate effects specific to silk position in two cases. In one instance, arrangement perpendicular to a flow produced selective head and neck carcinoma cell capture on silk with antibodies complexed to conjugated protein G. In a second scenario, asymmetric bacterial chemotaxis arose from asymmetric conjugation of enzymes to arranged silk. Overall, the biofabrication processes used here were rapid, required no complex chemistries, were biologically benign, and also the resulting engineered silk microfibers were flexible, readily manipulated and functionally active. Deployed here in microfluidic environments, biofunctional spider silk fiber provides a means to convey complex biological functions over a range of scales, further extending its potential as a biomaterial in biotechnological settings. Biotechnol. Bioeng. 2017;114: 83-95. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Multiscale mechanisms of nutritionally induced property variation in spider silks

PubMed Central

Nobbs, Madeleine; Martens, Penny J.; Tso, I-Min; Chuang, Wei-Tsung; Chang, Chung-Kai; Sheu, Hwo-Shuenn

2018-01-01

Variability in spider major ampullate (MA) silk properties at different scales has proven difficult to determine and remains an obstacle to the development of synthetic fibers mimicking MA silk performance. A multitude of techniques may be used to measure multiscale aspects of silk properties. Here we fed five species of Araneoid spider solutions that either contained protein or were protein deprived and performed silk tensile tests, small and wide-angle X-ray scattering (SAXS/WAXS), amino acid composition analyses, and silk gene expression analyses, to resolve persistent questions about how nutrient deprivation induces variations in MA silk mechanical properties across scales. Our analyses found that the properties of each spider’s silk varied differently in response to variations in their protein intake. We found changes in the crystalline and non-crystalline nanostructures to play specific roles in inducing the property variations we found. Across treatment MaSp expression patterns differed in each of the five species. We found that in most species MaSp expression and amino acid composition variations did not conform with our predictions based on a traditional MaSp expression model. In general, changes to the silk’s alanine and proline compositions influenced the alignment of the proteins within the silk’s amorphous region, which influenced silk extensibility and toughness. Variations in structural alignment in the crystalline and non-crystalline regions influenced ultimate strength independent of genetic expression. Our study provides the deepest insights thus far into the mechanisms of how MA silk properties vary from gene expression to nanostructure formations to fiber mechanics. Such knowledge is imperative for promoting the production of synthetic silk fibers. PMID:29390013

The effects of corn silk on glycaemic metabolism.

PubMed

Guo, Jianyou; Liu, Tongjun; Han, Linna; Liu, Yongmei

2009-11-23

Corn silk contains proteins, vitamins, carbohydrates, Ca, K, Mg and Na salts, fixed and volatile oils, steroids such as sitosterol and stigmasterol, alkaloids, saponins, tannins, and flavonoids. Base on folk remedies, corn silk has been used as an oral antidiabetic agent in China for decades. However, the hypoglycemic activity of it has not yet been understood in terms of modern pharmacological concepts. The purpose of this study is to investigate the effects of corn silk on glycaemic metabolism. Alloxan and adrenalin induced hyperglycemic mice were used in the study. The effects of corn silk on blood glucose, glycohemoglobin (HbA1c), insulin secretion, damaged pancreatic beta-cells, hepatic glycogen and gluconeogenesis in hyperglycemic mice were studied respectively. After the mice were orally administered with corn silk extract, the blood glucose and the HbA1c were significantly decreased in alloxan-induced hyperglycemic mice (p < 0.05, p < 0.01, respectively), while the level of insulin secretionn was markedly elevated in alloxa-induced hyperglycemic mice (p < 0.05). The alloxan-damaged pancreatic beta-cells of the mice were partly recovered gradually after the mice were administered with corn silk extract 15 days later. Also, the body weight of the alloxan-induced hyperglycemic mice was increased gradually. However, ascension of blood glucose induced by adrenalin and gluconeogenesis induced by L-alanine were not inhibited by corn silk extract treatment (p > 0.05). Although corn silk extract increased the level of hepatic glycogen in the alloxan-induced hyperglycemic mice, there was no significant difference between them and that of the control group(p > 0.05). Corn silk extract markedly reduced hyperglycemia in alloxan-induced diabetic mice. The action of corn silk extract on glycaemic metabolism is not via increasing glycogen and inhibiting gluconeogenesis but through increasing insulin level as well as recovering the injured beta-cells. The results suggest that corn silk extract may be used as a hypoglycemic food or medicine for hyperglycemic people in terms of this modern pharmacological study.

Reversible Hydrogel–Solution System of Silk with High Beta-Sheet Content

PubMed Central

2015-01-01

Silkworm silk has been widely used as a textile fiber, as biomaterials and in optically functional materials due to its extraordinary properties. The β-sheet-rich natural nanofiber units of about 10–50 nm in diameter are often considered the origin of these properties, yet it remains unclear how silk self-assembles into these hierarchical structures. A new system composed of β-sheet-rich silk nanofibers about 10–20 nm in diameter is reported here, where these nanofibers formed into “flowing hydrogels” at 0.5–2% solutions and could be transformed back into the solution state at lower concentrations, even with a high β-sheet content. This is in contrast with other silk processed materials, where significant β-sheet content negates reversibility between solution and solid states. These fibers are formed by regulating the self-assembly process of silk in aqueous solution, which changes the distribution of negative charges while still supporting β-sheet formation in the structures. Mechanistically, there appears to be a shift toward negative charges along the outside of the silk nanofibers in our present study, resulting in a higher zeta potential (above −50 mV) than previous silk materials which tend to be below −30 mV. The higher negative charge on silk nanofibers resulted in electrostatic repulsion strong enough to negate further assembly of the nanofibers. Changing silk concentration changed the balance between hydrophobic interactions and electrostatic repulsion of β-sheet-rich silk nanofibers, resulting in reversible hydrogel–solution transitions. Furthermore, the silk nanofibers could be disassembled into shorter fibers and even nanoparticles upon ultrasonic treatment following the transition from hydrogel to solution due to the increased dispersion of hydrophobic smaller particles, without the loss of β-sheet content, and with retention of the ability to transition between hydrogel and solution states through reversion to longer nanofibers during self-assembly. These reversible solution-hydrogel transitions were tunable with ultrasonic intensity, time, or temperature. PMID:25056606

DNA preservation in silk.

PubMed

Liu, Yawen; Zheng, Zhaozhu; Gong, He; Liu, Meng; Guo, Shaozhe; Li, Gang; Wang, Xiaoqin; Kaplan, David L

2017-06-27

The structure of DNA is susceptible to alterations at high temperature and on changing pH, irradiation and exposure to DNase. Options to protect and preserve DNA during storage are important for applications in genetic diagnosis, identity authentication, drug development and bioresearch. In the present study, the stability of total DNA purified from human dermal fibroblast cells, as well as that of plasmid DNA, was studied in silk protein materials. The DNA/silk mixtures were stabilized on filter paper (silk/DNA + filter) or filter paper pre-coated with silk and treated with methanol (silk/DNA + PT-filter) as a route to practical utility. After air-drying and water extraction, 50-70% of the DNA and silk could be retrieved and showed a single band on electrophoretic gels. 6% silk/DNA + PT-filter samples provided improved stability in comparison with 3% silk/DNA + filter samples and DNA + filter samples for DNA preservation, with ∼40% of the band intensity remaining at 37 °C after 40 days and ∼10% after exposure to UV light for 10 hours. Quantitative analysis using the PicoGreen assay confirmed the results. The use of Tris/borate/EDTA (TBE) buffer enhanced the preservation and/or extraction of the DNA. The DNA extracted after storage maintained integrity and function based on serving as a functional template for PCR amplification of the gene for zinc finger protein 750 (ZNF750) and for transgene expression of red fluorescence protein (dsRed) in HEK293 cells. The high molecular weight and high content of a crystalline beta-sheet structure formed on the coated surfaces likely accounted for the preservation effects observed for the silk/DNA + PT-filter samples. Although similar preservation effects were also obtained for lyophilized silk/DNA samples, the rapid and simple processing available with the silk-DNA-filter membrane system makes it appealing for future applications.

Reversible hydrogel-solution system of silk with high beta-sheet content.

PubMed

Bai, Shumeng; Zhang, Xiuli; Lu, Qiang; Sheng, Weiqin; Liu, Lijie; Dong, Boju; Kaplan, David L; Zhu, Hesun

2014-08-11

Silkworm silk has been widely used as a textile fiber, as biomaterials and in optically functional materials due to its extraordinary properties. The β-sheet-rich natural nanofiber units of about 10-50 nm in diameter are often considered the origin of these properties, yet it remains unclear how silk self-assembles into these hierarchical structures. A new system composed of β-sheet-rich silk nanofibers about 10-20 nm in diameter is reported here, where these nanofibers formed into "flowing hydrogels" at 0.5-2% solutions and could be transformed back into the solution state at lower concentrations, even with a high β-sheet content. This is in contrast with other silk processed materials, where significant β-sheet content negates reversibility between solution and solid states. These fibers are formed by regulating the self-assembly process of silk in aqueous solution, which changes the distribution of negative charges while still supporting β-sheet formation in the structures. Mechanistically, there appears to be a shift toward negative charges along the outside of the silk nanofibers in our present study, resulting in a higher zeta potential (above -50 mV) than previous silk materials which tend to be below -30 mV. The higher negative charge on silk nanofibers resulted in electrostatic repulsion strong enough to negate further assembly of the nanofibers. Changing silk concentration changed the balance between hydrophobic interactions and electrostatic repulsion of β-sheet-rich silk nanofibers, resulting in reversible hydrogel-solution transitions. Furthermore, the silk nanofibers could be disassembled into shorter fibers and even nanoparticles upon ultrasonic treatment following the transition from hydrogel to solution due to the increased dispersion of hydrophobic smaller particles, without the loss of β-sheet content, and with retention of the ability to transition between hydrogel and solution states through reversion to longer nanofibers during self-assembly. These reversible solution-hydrogel transitions were tunable with ultrasonic intensity, time, or temperature.

Silk film biomaterials for ocular surface repair

NASA Astrophysics Data System (ADS)

Lawrence, Brian David

Current biomaterial approaches for repairing the cornea's ocular surface upon injury are partially effective due to inherent material limitations. As a result there is a need to expand the biomaterial options available for use in the eye, which in turn will help to expand new clinical innovations and technology development. The studies illustrated here are a collection of work to further characterize silk film biomaterials for use on the ocular surface. Silk films were produced from regenerated fibroin protein solution derived from the Bombyx mori silkworm cocoon. Methods of silk film processing and production were developed to produce consistent biomaterials for in vitro and in vivo evaluation. A wide range of experiments was undertaken that spanned from in vitro silk film material characterization to in vivo evaluation. It was found that a variety of silk film properties could be controlled through a water-annealing process. Silk films were then generated that could be use in vitro to produce stratified corneal epithelial cell sheets comparable to tissue grown on the clinical standard substrate of amniotic membrane. This understanding was translated to produce a silk film design that enhanced corneal healing in vivo on a rabbit injury model. Further work produced silk films with varying surface topographies that were used as a simplified analog to the corneal basement membrane surface in vitro. These studies demonstrated that silk film surface topography is capable of directing corneal epithelial cell attachment, growth, and migration response. Most notably epithelial tissue development was controllably directed by the presence of the silk surface topography through increasing cell sheet migration efficiency at the individual cellular level. Taken together, the presented findings represent a comprehensive characterization of silk film biomaterials for use in ocular surface reconstruction, and indicate their utility as a potential material choice in the development of innovative procedures and technologies for corneal repair.

The use of injectable sonication-induced silk hydrogel for VEGF165 and BMP-2 delivery for elevation of the maxillary sinus floor

PubMed Central

Zhang, Wenjie; Wang, Xiuli; Wang, Shaoyi; Zhao, Jun; Xu, Lianyi; Zhu, Chao; Zeng, Deliang; Chen, Jake; Zhang, Zhiyuan; Kaplan, David L.; Jiang, Xinquan

2011-01-01

Sonication-induced silk hydrogels were previously prepared as an injectable bone replacement biomaterial, with a need to improve osteogenic features. Vascular endothelial growth factor (VEGF165) and bone morphogenic protein-2 (BMP-2) are key regulators of angiogenesis and osteogenesis, respectively, during bone regeneration. Therefore, the present study aimed at evaluating in situ forming silk hydrogels as a vehicle to encapsulate dual factors for rabbit maxillary sinus floor augmentation. Sonication-induced silk hydrogels were prepared in vitro and the slow release of VEGF165 and BMP-2 from these silk gels was evaluated by ELISA. For in vivo studies for each time point (4 and 12 weeks), 24 sinus floors elevation surgeries were made bilaterally in 12 rabbits for the following four treatment groups: silk gel (group Silk gel), silk gel/VEGF165 (group VEGF), silk gel/BMP-2 (group BMP-2), silk gel/VEGF165/BMP-2 (group V+B) (n=6 per group). Sequential florescent labeling and radiographic observations were used to record new bone formation and mineralization, along with histological and histomorphometric analysis. At week 4, VEGF165 promoted more tissue infiltration into the gel and accelerated the degradation of the gel material. At this time point, the bone area in group V+B was significantly larger than those in the other three groups. At week 12, elevated sinus floor heights of groups BMP-2 and V+B were larger than those of the Silk gel and VEGF groups, and the V+B group had the largest new bone area among all groups. In addition, a larger blood vessel area formed in the remaining gel areas in groups VEGF and V+B. In conclusion, VEGF165 and BMP-2 released from injectable and biodegradable silk gels promoted angiogenesis and new bone formation, with the two factors demonstrating an additive effect on bone regeneration. These results indicate that silk hydrogels can be used as an injectable vehicle to deliver multiple growth factors in a minimally invasive approach to regenerate irregular bony cavities. PMID:21889205

Silk protein-based hydrogels: Promising advanced materials for biomedical applications.

PubMed

Kapoor, Sonia; Kundu, Subhas C

2016-02-01

Hydrogels are a class of advanced material forms that closely mimic properties of the soft biological tissues. Several polymers have been explored for preparing hydrogels with structural and functional features resembling that of the extracellular matrix. Favourable material properties, biocompatibility and easy processing of silk protein fibers into several forms make it a suitable material for biomedical applications. Hydrogels made from silk proteins have shown a potential in overcoming limitations of hydrogels prepared from conventional polymers. A great deal of effort has been made to control the properties and to integrate novel topographical and functional characteristics in the hydrogel composed from silk proteins. This review provides overview of the advances in silk protein-based hydrogels with a primary emphasis on hydrogels of fibroin. It describes the approaches used to fabricate fibroin hydrogels. Attempts to improve the existing properties or to incorporate new features in the hydrogels by making composites and by improving fibroin properties by genetic engineering approaches are also described. Applications of the fibroin hydrogels in the realms of tissue engineering and controlled release are reviewed and their future potentials are discussed. This review describes the potentiality of silk fibroin hydrogel. Silk Fibroin has been widely recognized as an interesting biomaterial. Due to its properties including high mechanical strength and excellent biocompatibility, it has gained wide attention. Several groups are exploring silk-based materials including films, hydrogels, nanofibers and nanoparticles for different biomedical applications. Although there is a good amount of literature available on general properties and applications of silk based biomaterials, there is an inadequacy of extensive review articles that specifically focus on silk based hydrogels. Silk-based hydrogels have a strong potential to be utilized in biomedical applications. Our work is an effort to highlight the research that has been done in the area of silk-based hydrogels. It aims to provide an overview of the advances that have been made and the future course available. It will provide an overview of the silk-based hydrogels as well as may direct the readers to the specific areas of application. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Effect of UV-light on the uniaxial tensile properties and structure of uncoated and TiO2 coated Bombyx mori silk fibers

NASA Astrophysics Data System (ADS)

Aksakal, Baki; Koç, Kenan; Yargı, Önder; Tsobkallo, Katherina

2016-01-01

The effect of UV-light on the uniaxial tensile properties and the structure of uncoated and TiO2 coated silk fibers in the bave form by using sol-gel method was investigated with tensile testing and FT-IR/ATR spectroscopy methods after the silk filaments were exposed to UV-light with high intensity of 760 W/m2 for different times from 0.5 h to 1 day. It was clearly observed that TiO2 coating considerably increased the Young's modulus of the uncoated silk single filament by around 17% before the UV-irradiation. The yield point and the post yield region disappeared on the stress-strain curves of both uncoated and TiO2 coated silk filaments after UV-irradiation time higher than 1 h. Except for the Young's modulus, most of the tensile characteristics of both uncoated and TiO2 coated silk filaments decreased remarkably with increasing UV-irradiation time, e.g., after 1 h irradiation, although the Young's modulus slightly changed and ultimate tensile strength decreased by only around 18% and 23%, for the uncoated and TiO2 coated silk filaments, respectively; breaking extension decreased dramatically by 67% and 72%, respectively, for uncoated and TiO2 coated silk filaments. Only the Young's modulus of TiO2 coated silk filaments which can be considered as a more stable tensile characteristic became significantly higher than that of the uncoated silk filaments with increasing UV-irradiation time. After 1 day irradiation, even though the uncoated silk filaments could not be tested and completely lost of their fiber properties, the TiO2 coated silk filaments showed a stress-strain curve in initial elastic region with Young's modulus of ∼13 GPa which indicates considerable protective effect of TiO2 on the silk fiber structure, especially on the β-sheet microcrystals against UV-radiation. The FT-IR/ATR spectral results showed that significant photodegradation took place in not only crystalline but also amorphous regions which were deduced from the decrease in the absorbance ratios of the bands assigned to CH3 rocking, Cα-Cβ, Cα-C stretching vibrations in β-sheet crystalline regions as well as the Amide I, II, and III bands for both crystalline and amorphous regions. Even though the ratio of crystalline to amorphous regions in uncoated silk filaments decreased significantly, the ratio in TiO2 coated silk filaments became almost constant with increasing UV-irradiation time which may indicate more stable β-sheet microcrystals against photodegradation.

Silk Roads or Steppe Roads? The Silk Roads in World History.

ERIC Educational Resources Information Center

Christian, David

2000-01-01

Explores the prehistory of the Silk Roads, reexamines their structure and history in the classical era, and explores shifts in their geography in the last one thousand years. Explains that a revised understanding of the Silk Roads demonstrates how the Afro-Eurasian land mass has been linked by networks of exchange since the Bronze Age. (CMK)

Derivation of a variational principle for plane strain elastic-plastic silk biopolymers

NASA Astrophysics Data System (ADS)

He, J. H.; Liu, F. J.; Cao, J. H.; Zhang, L.

2014-01-01

Silk biopolymers, such as spider silk and Bombyx mori silk, behave always elastic-plastically. An elastic-plastic model is adopted and a variational principle for the small strain, rate plasticity problem is established by semi-inverse method. A trial Lagrangian is constructed where an unknown function is included which can be identified step by step.

Structural and thermal properties of silk fibroin - Silver nanoparticles composite films

NASA Astrophysics Data System (ADS)

Shivananda, C. S.; Rao B, B. Lakshmeesha; Shetty, G. Rajesh; Sangappa, Y.

2018-05-01

In this work, silk fibroin-silver nanoparticles (SF-AgNPs) composite films have been prepared by simple solution casting method. The composite films were examined for structural and thermal properties using X-ray diffraction (XRD), thermogravimatric (TGA) and differential scanning calorimetry (DSC) analysis. The XRD results showed that with the introduction of AgNPs in the silk fibroin matrix the amorphous nature of the silk fibroin decreases with increasing nanoparticles concentration. The silk fibroin films possess good thermal stability with the presence of AgNPs.

Silk fabric dyed with extract of sophora flower bud.

PubMed

Yan, Su; Pan, Shanshan; Ji, Junling

2018-02-01

This study analysed the use of sophora flower bud extract for dyeing and the resulting colour character and fastness of dyed silk fabric. The pigment composition on the silk fabric and recycling of this extract were also studied. The results indicated that the dyed silk fabric possessed good washing, rubbing and perspiration fastness, and the pigment composition on the silk fabric was mainly rutin and quercetin. The average recovery rate of the dye was 55.00%. These results demonstrate that the sophora flower bud extract is an effective natural dye.

Structure-Function-Property-Design Interplay in Biopolymers: Spider Silk

PubMed Central

Tokareva, Olena; Jacobsen, Matthew; Buehler, Markus; Wong, Joyce; Kaplan, David L.

2013-01-01

Spider silks have been a focus of research for almost two decades due to their outstanding mechanical and biophysical properties. Recent advances in genetic engineering have led to the synthesis of recombinant spider silks, thus helping to unravel a fundamental understanding of structure-function-property relationships. The relationships between molecular composition, secondary structures, and mechanical properties found in different types of spider silks are described, along with a discussion of artificial spinning of these proteins and their bioapplications, including the role of silks in biomineralization and fabrication of biomaterials with controlled properties. PMID:23962644

Silk-based delivery systems of bioactive molecules

PubMed Central

Numata, Keiji; Kaplan, David L

2010-01-01

Silks are biodegradable, biocompatible, self-assemblying proteins that can also be tailored via genetic engineering to contain specific chemical features, offering utility for drug and gene delivery. Silkworm silk has been used in biomedical sutures for decades and has recently achieved Food and Drug Administration approval for expanded biomaterials device utility. With the diversity and control of size, structure and chemistry, modified or recombinant silk proteins can be designed and utilized in various biomedical application, such as for the delivery of bioactive molecules. This review focuses on the biosynthesis and applications of silk-based multi-block copolymer systems and related silk protein drug delivery systems. The utility of these systems for the delivery of small molecule drugs, proteins and genes are reviewed. PMID:20298729

Regeneration of high-quality silk fibroin fiber by wet spinning from CaCl2-formic acid solvent.

PubMed

Zhang, Feng; Lu, Qiang; Yue, Xiaoxiao; Zuo, Baoqi; Qin, Mingde; Li, Fang; Kaplan, David L; Zhang, Xueguang

2015-01-01

Silks spun by silkworms and spiders feature outstanding mechanical properties despite being spun under benign conditions. The superior physical properties of silk are closely related to its complicated hierarchical structures constructed from nanoscale building blocks, such as nanocrystals and nanofibrils. Here, we report a novel silk dissolution behavior, which preserved nanofibrils in CaCl2-formic acid solution, that enables spinning of high-quality fibers with a hierarchical structure. This process is characterized by simplicity, high efficiency, low cost, environmental compatibility and large-scale industrialization potential, as well as having utility and potential for the recycling of silk waste and the production of silk-based functional materials. Copyright © 2014. Published by Elsevier Ltd.

Ovary Apical Abortion under Water Deficit Is Caused by Changes in Sequential Development of Ovaries and in Silk Growth Rate in Maize.

PubMed

Oury, Vincent; Tardieu, François; Turc, Olivier

2016-06-01

Grain abortion allows the production of at least a few viable seeds under water deficit but causes major yield loss. It is maximum for water deficits occurring during flowering in maize (Zea mays). We have tested the hypothesis that abortion is linked to the differential development of ovary cohorts along the ear and to the timing of silk emergence. Ovary volume and silk growth were followed over 25 to 30 d under four levels of water deficit and in four hybrids in two experiments. A position-time model allowed characterizing the development of ovary cohorts and their silk emergence. Silk growth rate decreased in water deficit and stopped 2 to 3 d after first silk emergence, simultaneously for all ovary cohorts, versus 7 to 8 d in well-watered plants. Abortion rate in different treatments and positions on the ear was not associated with ovary growth rate. It was accounted for by the superposition of (1) the sequential emergence of silks originating from ovaries of different cohorts along the ear with (2) one event occurring on a single day, the simultaneous silk growth arrest. Abortion occurred in the youngest ovaries whose silks did not emerge 2 d before silk arrest. This mechanism accounted for more than 90% of drought-related abortion in our experiments. It resembles the control of abortion in a large range of species and inflorescence architectures. This finding has large consequences for breeding drought-tolerant maize and for modeling grain yields in water deficit. © 2016 American Society of Plant Biologists. All Rights Reserved.

Ovary Apical Abortion under Water Deficit Is Caused by Changes in Sequential Development of Ovaries and in Silk Growth Rate in Maize1[OPEN

PubMed Central

Tardieu, François

2016-01-01

Grain abortion allows the production of at least a few viable seeds under water deficit but causes major yield loss. It is maximum for water deficits occurring during flowering in maize (Zea mays). We have tested the hypothesis that abortion is linked to the differential development of ovary cohorts along the ear and to the timing of silk emergence. Ovary volume and silk growth were followed over 25 to 30 d under four levels of water deficit and in four hybrids in two experiments. A position-time model allowed characterizing the development of ovary cohorts and their silk emergence. Silk growth rate decreased in water deficit and stopped 2 to 3 d after first silk emergence, simultaneously for all ovary cohorts, versus 7 to 8 d in well-watered plants. Abortion rate in different treatments and positions on the ear was not associated with ovary growth rate. It was accounted for by the superposition of (1) the sequential emergence of silks originating from ovaries of different cohorts along the ear with (2) one event occurring on a single day, the simultaneous silk growth arrest. Abortion occurred in the youngest ovaries whose silks did not emerge 2 d before silk arrest. This mechanism accounted for more than 90% of drought-related abortion in our experiments. It resembles the control of abortion in a large range of species and inflorescence architectures. This finding has large consequences for breeding drought-tolerant maize and for modeling grain yields in water deficit. PMID:26598464

Bioconjugation of silk fibroin nanoparticles with enzyme and Peptide and their characterization.

PubMed

Wang, Fei; Zhang, Yu-Qing

2015-01-01

Bombyx mori silk fibroin is a type of protein-based polymer with unique characteristics that is widely used in the research and development of medical biomaterials. The degummed filament of silk fibroin can be dissolved in a highly concentrated salt solution. After desalination, the regenerated liquid silk fibroin (LSF) solution could be made into various forms of silk biomaterials, such as powder, fiber, film, porous matrix, 3D scaffold, and hydrogel, depending on its application. In this study, we mixed the liquid silk solution with enzymes, including oxidase and hydrolase, and rapidly injected the mixture into an excess of acetone. The enzyme retained most of its enzymatic activity and was also captured in silk fibroin nanoparticles (SFNs), which instantly formed via a configuration transition of the regenerated silk protein from a random coil and α-helix to a β-sheet. The resulting enzyme-captured SFNs displayed a fine crystal structure with a high activity recovery and good thermal stability. Moreover, the affinities of these modified enzymes to their substrate did not evidently suffer from the capture. When only the liquid silk solution was rapidly injected into acetone, the resulting globular SFNs with the same crystallinity were also a good carrier that was covalently conjugated to enzymes and insulin. Thus, silk protein nanoparticles are of potential value as an enzyme or peptide delivery system for the research and development of medical biomaterials. In this report, the bioconjugation of SFNs with glucose oxidase, superoxidase, β-glucosidase, L-asparaginase, neutral protease, and insulin and their characterization are described in detail. © 2015 Elsevier Inc. All rights reserved.

Curcumin-functionalized silk materials for enhancing adipogenic differentiation of bone marrow-derived human mesenchymal stem cells

PubMed Central

Li, Chunmei; Luo, Tingting; Zheng, Zhaozhu; Murphy, Amanda R.; Wang, Xiaoqin; Kaplan, David L.

2014-01-01

Curcumin, a natural phenolic compound derived from the plant Curcuma longa, was physically entrapped and stabilized in silk hydrogel films and its influence on human bone marrow-derived mesenchymal stem cells (hBMSCs) was assessed related to adipogenic differentiation. The presence of curcumin significantly reduced silk gelation time and changed the porous morphology of gel matrix, but did not change the formation of silk beta-sheet structure. Based on spectrofluorimetric analysis, curcumin likely interacted with hydrophobic residues in silk, interacting with the beta-sheet domains formed in the hydrogels. The antioxidant activity of silk film-associated curcumin remained functional over at least one month in both the dry and hydrated state. Negligible curcumin was released from silk hydrogel films over 48 hours incubation in aqueous solution. For hBMSCs cultured on silk films containing more than 0.25 mg/mL curcumin, cell proliferation was inhibited while adipogenesis was significantly promoted based on transcripts as well as oil red O staining. When hBMSCs were cultured in media containing free curcumin, both proliferation and adipogenesis of hBMSCs were inhibited when curcumin concentrations exceeded 5 μM, which is more than 1,000-times higher than the level of curcumin released from the films in aqueous solution. Thus, silk film-associated curcumin exhibited different effects on hBMSC proliferation and differentiation when compared to curcumin in solution. PMID:25132274

YorkieCA overexpression in the posterior silk gland improves silk yield in Bombyx mori.

PubMed

Zhang, Panli; Liu, Shumin; Song, Hong-Sheng; Zhang, Guozheng; Jia, Qiangqiang; Li, Sheng

2017-07-01

The traditional hybrid breeding techniques can no longer meet the increasing demands for silk production by the silkworm, Bombyx mori, and further improvement of the silk yield will depend on modern molecular breeding techniques. Here, we report improved silk yield in transgenic silkworms overexpressing the oncogene Yorkie CA specifically in the posterior silk gland (PSG). The Yorkie CA cDNA was ligated downstream of the hr3 enhancer and the fibroin L-chain (Fil) promoter, then inserted into a piggyBac vector for transgene. Overexpression of Yorkie CA in the PSG significantly increased the weight of the PSG, and also increased the weight of the cocoon, larval body, and pupal body to decreasing degrees. Overexpression of Yorkie CA up-regulated the Yorkie target genes resulting in increased cell size, endomitosis, the number of protein synthesis organelles, the expression of fibroin genes in the PSG, and eventually silk yield. Additionally, as we reported previously using the binary GAL4/UAS system, transgenic silkworms overexpressing Ras1 CA with the hr3 enhancer and the Fil promoter also showed improved silk yield. Unfortunately, the hybrid progeny of Yorkie CA -overexpressing silkworms and Ras1 CA -overexpressing silkworms did not show overlapping improved silk yield due to the failure to increase expression of both Yorkie and Ras1. Copyright © 2017. Published by Elsevier Ltd.

Investigate the Effect of Thawing Process on the Self-Assembly of Silk Protein for Tissue Applications.

PubMed

Nguyen, Hiep Thi; Luong, Hien Thu; Nguyen, Hai Dai; Tran, Hien Anh; Huynh, Khon Chan; Vo, Toi Van

2017-01-01

Biological self-assembly is a process in which building blocks autonomously organize to form stable supermolecules of higher order and complexity through domination of weak, noncovalent interactions. For silk protein, the effect of high incubating temperature on the induction of secondary structure and self-assembly was well investigated. However, the effect of freezing and thawing on silk solution has not been studied. The present work aimed to investigate a new all-aqueous process to form 3D porous silk fibroin matrices using a freezing-assisted self-assembly method. This study proposes an experimental investigation and optimization of environmental parameters for the self-assembly process such as freezing temperature, thawing process, and concentration of silk solution. The optical images demonstrated the possibility and potential of -80ST48 treatment to initialize the self-assembly of silk fibroin as well as controllably fabricate a porous scaffold. Moreover, the micrograph images illustrate the assembly of silk protein chain in 7 days under the treatment of -80ST48 process. The surface morphology characterization proved that this method could control the pore size of porous scaffolds by control of the concentration of silk solution. The animal test showed the support of silk scaffold for cell adhesion and proliferation, as well as the cell migration process in the 3D implantable scaffold.

A highly divergent gene cluster in honey bees encodes a novel silk family.

PubMed

Sutherland, Tara D; Campbell, Peter M; Weisman, Sarah; Trueman, Holly E; Sriskantha, Alagacone; Wanjura, Wolfgang J; Haritos, Victoria S

2006-11-01

The pupal cocoon of the domesticated silk moth Bombyx mori is the best known and most extensively studied insect silk. It is not widely known that Apis mellifera larvae also produce silk. We have used a combination of genomic and proteomic techniques to identify four honey bee fiber genes (AmelFibroin1-4) and two silk-associated genes (AmelSA1 and 2). The four fiber genes are small, comprise a single exon each, and are clustered on a short genomic region where the open reading frames are GC-rich amid low GC intergenic regions. The genes encode similar proteins that are highly helical and predicted to form unusually tight coiled coils. Despite the similarity in size, structure, and composition of the encoded proteins, the genes have low primary sequence identity. We propose that the four fiber genes have arisen from gene duplication events but have subsequently diverged significantly. The silk-associated genes encode proteins likely to act as a glue (AmelSA1) and involved in silk processing (AmelSA2). Although the silks of honey bees and silkmoths both originate in larval labial glands, the silk proteins are completely different in their primary, secondary, and tertiary structures as well as the genomic arrangement of the genes encoding them. This implies independent evolutionary origins for these functionally related proteins.

3D Bioprinting of Self-Standing Silk-Based Bioink.

PubMed

Zheng, Zhaozhu; Wu, Jianbing; Liu, Meng; Wang, Heng; Li, Chunmei; Rodriguez, María J; Li, Gang; Wang, Xiaoqin; Kaplan, David L

2018-03-01

Silk/polyethylene glycol (PEG) hydrogels are studied as self-standing bioinks for 3D printing for tissue engineering. The two components of the bioink, silk fibroin protein (silk) and PEG, are both Food and Drug Administration approved materials in drug and medical device products. Mixing PEG with silk induces silk β-sheet structure formation and thus gelation and water insolubility due to physical crosslinking. A variety of constructs with high resolution, high shape fidelity, and homogeneous gel matrices are printed. When human bone marrow mesenchymal stem cells are premixed with the silk solution prior to printing and the constructs are cultured in this medium, the cell-loaded constructs maintain their shape over at least 12 weeks. Interestingly, the cells grow faster in the higher silk concentration (10%, w/v) gel than in lower ones (7.5 and 5%, w/v), likely due to the difference in material stiffness and the amount of residual PEG remaining in the gel related to material hydrophobicity. Subcutaneous implantation of 7.5% (w/v) bioink gels with and without printed fibroblast cells in mice reveals that the cells survive and proliferate in the gel matrix for at least 6 week postimplantation. The results suggest that these silk/PEG bioink gels may provide suitable scaffold environments for cell printing and function. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Investigate the Effect of Thawing Process on the Self-Assembly of Silk Protein for Tissue Applications

PubMed Central

Tran, Hien Anh; Huynh, Khon Chan; Vo, Toi Van

2017-01-01

Biological self-assembly is a process in which building blocks autonomously organize to form stable supermolecules of higher order and complexity through domination of weak, noncovalent interactions. For silk protein, the effect of high incubating temperature on the induction of secondary structure and self-assembly was well investigated. However, the effect of freezing and thawing on silk solution has not been studied. The present work aimed to investigate a new all-aqueous process to form 3D porous silk fibroin matrices using a freezing-assisted self-assembly method. This study proposes an experimental investigation and optimization of environmental parameters for the self-assembly process such as freezing temperature, thawing process, and concentration of silk solution. The optical images demonstrated the possibility and potential of −80ST48 treatment to initialize the self-assembly of silk fibroin as well as controllably fabricate a porous scaffold. Moreover, the micrograph images illustrate the assembly of silk protein chain in 7 days under the treatment of −80ST48 process. The surface morphology characterization proved that this method could control the pore size of porous scaffolds by control of the concentration of silk solution. The animal test showed the support of silk scaffold for cell adhesion and proliferation, as well as the cell migration process in the 3D implantable scaffold. PMID:28367442

Natural Occurring Silks and Their Analogues as Materials for Nerve Conduits.

PubMed

Radtke, Christine

2016-10-20

Spider silk and its synthetic derivatives have a light weight in combination with good strength and elasticity. Their high cytocompatibility and low immunogenicity make them well suited for biomaterial products such as nerve conduits. Silk proteins slowly degrade enzymatically in vivo, thus allowing for an initial therapeutic effect such as in nerve scaffolding to facilitate endogenous repair processes, and then are removed. Silks are biopolymers naturally produced by many species of arthropods including spiders, caterpillars and mites. The silk fibers are secreted by the labial gland of the larvae of some orders of Holometabola (insects with pupa) or the spinnerets of spiders. The majority of studies using silks for biomedical applications use materials from silkworms or spiders, mostly of the genus Nephila clavipes . Silk is one of the most promising biomaterials with effects not only in nerve regeneration, but in a number of regenerative applications. The development of silks for human biomedical applications is of high scientific and clinical interest. Biomaterials in use for biomedical applications have to meet a number of requirements such as biocompatibility and elicitation of no more than a minor inflammatory response, biodegradability in a reasonable time and specific structural properties. Here we present the current status in the field of silk-based conduit development for nerve repair and discuss current advances with regard to potential clinical transfer of an implantable nerve conduit for enhancement of nerve regeneration.

Tissue response and biodegradation of composite scaffolds prepared from Thai silk fibroin, gelatin and hydroxyapatite.

PubMed

Tungtasana, Hathairat; Shuangshoti, Somruetai; Shuangshoti, Shanop; Kanokpanont, Sorada; Kaplan, David L; Bunaprasert, Tanom; Damrongsakkul, Siriporn

2010-12-01

This work aimed to investigate tissue responses and biodegradation, both in vitro and in vivo, of four types of Bombyx mori Thai silk fibroin based-scaffolds. Thai silk fibroin (SF), conjugated gelatin/Thai silk fibroin (CGSF), hydroxyapatite/Thai silk fibroin (SF4), and hydroxyapatite/conjugated gelatin/Thai silk fibroin (CGSF4) scaffolds were fabricated using salt-porogen leaching, dehydrothermal/chemical crosslinking and an alternate soaking technique for mineralization. In vitro biodegradation in collagenase showed that CGSF scaffolds had the slowest biodegradability, due to the double crosslinking by dehydrothermal and chemical treatments. The hydroxyapatite deposited from alternate soaking separated from the surface of the protein scaffolds when immersed in collagenase. From in vivo biodegradation studies, all scaffolds could still be observed after 12 weeks of implantation in subcutaneous tissue of Wistar rats and also following ISO10993-6: Biological evaluation of medical devices. At 2 and 4 weeks of implantation the four types of Thai silk fibroin based-scaffolds were classified as "non-irritant" to "slight-irritant", compared to Gelfoam(®) (control samples). These natural Thai silk fibroin-based scaffolds may provide suitable biomaterials for clinical applications.

In situ synthesis of silver nanoparticles uniformly distributed on polydopamine-coated silk fibers for antibacterial application.

PubMed

Lu, Zhisong; Xiao, Jing; Wang, Ying; Meng, Mei

2015-08-15

Fabrication of silver nanoparticles (AgNPs)-modified silk for antibacterial application is one of the hottest topics in the textile material research. However, the utilization of a polymer as both 3-dimensional matrix and reductant for the in-situ synthesis of AgNPs on silk fibers has not been realized. In this work, a facile, efficient and green approach was developed to in-situ grow AgNPs on the polydopamine (PDA)-functionalized silk. AgNPs with the size of 30-90 nm were uniformly deposited on the silk fiber surface with the PDA coating layer as a reduction reagent. The AgNPs exhibit excellent face-centered cubic crystalline structures. The bacterial growth curve and inhibition zone assays clearly demonstrate the antibacterial properties of the functionalized silk. Both high Ag(+) release level and long-time release profile were observed for the as-prepared AgNPs-PDA-coated silk, indicating the high-density loading of AgNPs and the possible long-term antibacterial effects. This work may provide a new method for the preparation of AgNPs-functionalized silk with antibacterial activity for the clothing and textile industry. Copyright © 2015 Elsevier Inc. All rights reserved.

Controlling the cell adhesion property of silk films by graft polymerization.

PubMed

Dhyani, Vartika; Singh, Neetu

2014-04-09

We report here a graft polymerization method to improve the cell adhesion property of Bombyx mori silk fibroin films. B. mori silk has evolved as a promising material for tissue engineering because of its biocompatibility and biodegradability. However, silk's hydrophobic character makes cell adhesion and proliferation difficult. Also, the lack of sufficient reactive amino acid residues makes biofunctionalization via chemical modification challenging. Our study describes a simple method that provides increased chemical handles for tuning of the surface chemistry of regenerated silk films (SFs), thus allowing manipulation of their bioactivity. By grafting pAAc and pHEMA via plasma etching, we have increased carboxylic acid and hydroxyl groups on silk, respectively. These modifications allowed us to tune the hydrophilicity of SFs and provide functional groups for bioconjugation. Our strategy also allowed us to develop silk-based surface coatings, where spatial control over cell adhesion can be achieved. This control over cell adhesion in a particular region of the SFs is difficult to obtain via existing methods of modifying the silk fibroin instead of the SF surface. Thus, our strategy will be a valuable addition to the toolkit of biofunctionalization for enhancing SFs' tissue engineering applications.

Silk Spinning in Silkworms and Spiders

PubMed Central

Andersson, Marlene; Johansson, Jan; Rising, Anna

2016-01-01

Spiders and silkworms spin silks that outcompete the toughness of all natural and manmade fibers. Herein, we compare and contrast the spinning of silk in silkworms and spiders, with the aim of identifying features that are important for fiber formation. Although spiders and silkworms are very distantly related, some features of spinning silk seem to be universal. Both spiders and silkworms produce large silk proteins that are highly repetitive and extremely soluble at high pH, likely due to the globular terminal domains that flank an intermediate repetitive region. The silk proteins are produced and stored at a very high concentration in glands, and then transported along a narrowing tube in which they change conformation in response primarily to a pH gradient generated by carbonic anhydrase and proton pumps, as well as to ions and shear forces. The silk proteins thereby convert from random coil and alpha helical soluble conformations to beta sheet fibers. We suggest that factors that need to be optimized for successful production of artificial silk proteins capable of forming tough fibers include protein solubility, pH sensitivity, and preservation of natively folded proteins throughout the purification and initial spinning processes. PMID:27517908

Silk fibroin/gold nanocrystals: a new example of biopolymer-based nanocomposites

NASA Astrophysics Data System (ADS)

Noinville, S.; Garnier, A.; Courty, A.

2017-05-01

The dispersion of nanoparticles in ordered polymer nanostructures can provide control over particle location and orientation, and pave the way for tailored nanomaterials that have enhanced mechanical, electrical, or optical properties. Here we used silk fibroin, a natural biopolymer, to embed gold nanocrystals (NCs), so as to obtain well-ordered structures such as nanowires and self-assembled triangular nanocomposites. Monodisperse gold NCs synthesized in organic media are mixed to silk fibroin and the obtained nanocomposites are characterized by UV-visible spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (FE-SEM), atomic force microscopy (AFM) and Infrared spectroscopy. The optical properties study of gold NCs and silk-gold nanocomposites shows that the Surface Plasmon band is blue shifted compared to gold NCs. The size and shape of NCs gold superlattices can be well controlled by the presence of silk fibroin giving nanowires and also self-assembled triangular nanocomposites as characterized by TEM, FE-SEM and AFM. The strong interaction between gold NCs and silk fibroin is also revealed by the conformation change of silk protein in presence of gold NCs, as shown by FTIR analysis. The formation of such ordered nanocomposites (gold NCs/silk fibroin) will provide new nanoplasmonic devices.

Introducing biomimetic shear and ion gradients to microfluidic spinning improves silk fiber strength.

PubMed

Li, David; Jacobsen, Matthew M; Gyune Rim, Nae; Backman, Daniel; Kaplan, David L; Wong, Joyce Y

2017-05-31

Silkworm silk is an attractive biopolymer for biomedical applications due to its high mechanical strength and biocompatibility; as a result, there is increasing interest in scalable devices to spin silk and recombinant silk so as to improve and customize their properties for diverse biomedical purposes (Vepari and Kaplan 2007 Prog. Polym. Sci. 32 ). While artificial spinning of regenerated silk fibroins adds tunability to properties such as degradation rate and surface functionalization, the resulting fibers do not yet approach the mechanical strength of native silkworm silk. These drawbacks reduce the applicability and attractiveness of artificial silk (Kinahan et al 2011 Biomacromolecules 12 ). Here, we used computational fluid dynamic simulations to incorporate shear in tandem with biomimetic ion gradients by coupling a modular novel glass microfluidic device to our previous co-axial flow device. Fibers spun with this combined apparatus demonstrated a significant increase in mechanical strength compared to fibers spun with the basic apparatus alone, with a three-fold increase in Young's modulus and extensibility and a twelve-fold increase in toughness. These results thus demonstrate the critical importance of ionic milieu and shear stress in spinning strong fibers from solubilized silk fibroin.

Characterizing the Effects of Washing by Different Detergents on the Wavelength-Scale Microstructures of Silk Samples Using Mueller Matrix Polarimetry.

PubMed

Dong, Yang; He, Honghui; He, Chao; Zhou, Jialing; Zeng, Nan; Ma, Hui

2016-08-10

Silk fibers suffer from microstructural changes due to various external environmental conditions including daily washings. In this paper, we take the backscattering Mueller matrix images of silk samples for non-destructive and real-time quantitative characterization of the wavelength-scale microstructure and examination of the effects of washing by different detergents. The 2D images of the 16 Mueller matrix elements are reduced to the frequency distribution histograms (FDHs) whose central moments reveal the dominant structural features of the silk fibers. A group of new parameters are also proposed to characterize the wavelength-scale microstructural changes of the silk samples during the washing processes. Monte Carlo (MC) simulations are carried out to better understand how the Mueller matrix parameters are related to the wavelength-scale microstructure of silk fibers. The good agreement between experiments and simulations indicates that the Mueller matrix polarimetry and FDH based parameters can be used to quantitatively detect the wavelength-scale microstructural features of silk fibers. Mueller matrix polarimetry may be used as a powerful tool for non-destructive and in situ characterization of the wavelength-scale microstructures of silk based materials.

Characterizing the Effects of Washing by Different Detergents on the Wavelength-Scale Microstructures of Silk Samples Using Mueller Matrix Polarimetry

PubMed Central

Dong, Yang; He, Honghui; He, Chao; Zhou, Jialing; Zeng, Nan; Ma, Hui

2016-01-01

Silk fibers suffer from microstructural changes due to various external environmental conditions including daily washings. In this paper, we take the backscattering Mueller matrix images of silk samples for non-destructive and real-time quantitative characterization of the wavelength-scale microstructure and examination of the effects of washing by different detergents. The 2D images of the 16 Mueller matrix elements are reduced to the frequency distribution histograms (FDHs) whose central moments reveal the dominant structural features of the silk fibers. A group of new parameters are also proposed to characterize the wavelength-scale microstructural changes of the silk samples during the washing processes. Monte Carlo (MC) simulations are carried out to better understand how the Mueller matrix parameters are related to the wavelength-scale microstructure of silk fibers. The good agreement between experiments and simulations indicates that the Mueller matrix polarimetry and FDH based parameters can be used to quantitatively detect the wavelength-scale microstructural features of silk fibers. Mueller matrix polarimetry may be used as a powerful tool for non-destructive and in situ characterization of the wavelength-scale microstructures of silk based materials. PMID:27517919

Silk Spinning in Silkworms and Spiders.

PubMed

Andersson, Marlene; Johansson, Jan; Rising, Anna

2016-08-09

Spiders and silkworms spin silks that outcompete the toughness of all natural and manmade fibers. Herein, we compare and contrast the spinning of silk in silkworms and spiders, with the aim of identifying features that are important for fiber formation. Although spiders and silkworms are very distantly related, some features of spinning silk seem to be universal. Both spiders and silkworms produce large silk proteins that are highly repetitive and extremely soluble at high pH, likely due to the globular terminal domains that flank an intermediate repetitive region. The silk proteins are produced and stored at a very high concentration in glands, and then transported along a narrowing tube in which they change conformation in response primarily to a pH gradient generated by carbonic anhydrase and proton pumps, as well as to ions and shear forces. The silk proteins thereby convert from random coil and alpha helical soluble conformations to beta sheet fibers. We suggest that factors that need to be optimized for successful production of artificial silk proteins capable of forming tough fibers include protein solubility, pH sensitivity, and preservation of natively folded proteins throughout the purification and initial spinning processes.

Pro-apoptotic and anti-proliferative effects of corn silk extract on human colon cancer cell lines.

PubMed

Guo, Hao; Guan, Hong; Yang, Wenqin; Liu, Han; Hou, Huiling; Chen, Xue; Liu, Zhenyan; Zang, Chuangang; Liu, Yuchao; Liu, Jicheng

2017-02-01

Corn silk is an economically and nutritionally significant natural product as it represents a staple food for a large proportion of the world population. This study investigated the anticancer activity of corn silk extract in human colon cancer cells and human gastric cancer cells. Following treatment with corn silk extract, certain apoptosis-related events were observed, including inhibition of cell proliferation, loss of mitochondrial membrane potential (ΔΨm), release of Ca2+ and release of cytochrome c from the mitochondria into the cytosol. Our results revealed that corn silk extract inhibited the proliferation of cancer cells and increased the level of apoptosis in a concentration-dependent manner. Western blot analysis revealed that corn silk extract upregulated the levels of Bax, cytochrome c , caspase-3 and caspase-9, but downregulated the levels of B-cell lymphoma 2. These results suggest that corn silk extract may induce apoptosis through the mitochondria-mediated pathway.

Sample selection, preparation methods, and the apparent tensile properties of silkworm (B. mori) cocoon silk.

PubMed

Reed, Emily J; Bianchini, Lindsay L; Viney, Christopher

2012-06-01

Reported literature values of the tensile properties of natural silk cover a wide range. While much of this inconsistency is the result of variability that is intrinsic to silk, some is also a consequence of differences in the way that silk is prepared for tensile tests. Here we explore how measured mechanical properties of Bombyx mori cocoon silk are affected by two intrinsic factors (the location from which the silk is collected within the cocoon, and the color of the silk), and two extrinsic factors (the storage conditions prior to testing, and different styles of reeling the fiber). We find that extrinsic and therefore controllable factors can affect the properties more than the intrinsic ones studied. Our results suggest that enhanced inter-laboratory collaborations, that lead to standardized sample collection, handling, and storage protocols prior to mechanical testing, would help to decrease unnecessary (and complicating) variation in reported tensile properties. Copyright © 2011 Wiley Periodicals, Inc.

Electrodeposited silk coatings for bone implants.

PubMed

Elia, Roberto; Michelson, Courtney D; Perera, Austin L; Brunner, Teresa F; Harsono, Masly; Leisk, Gray G; Kugel, Gerard; Kaplan, David L

2015-11-01

The aim of this study was to characterize the mechanical properties and drug elution features of silk protein-based electrodeposited dental implant coatings. Silk processing conditions were modified to obtain coatings with a range of mechanical properties on titanium studs. These coatings were assessed for adhesive strength and dissolution, with properties tuned using water vapor annealing or glycerol incorporation to modulate crystalline content. Coating reproducibility was demonstrated over a range of silk concentrations from 1% to 10%. Surface roughness of titanium substrates was altered using industry relevant acid etching and grit blasting, and the effect of surface topography on silk coating adhesion was assessed. Florescent compounds were incorporated into the silk coatings, which were modulated for crystalline content, to achieve four days of sustained release of the compounds. This silk electrogelation technique offers a safe and relatively simple approach to generate mechanically robust, biocompatible, and degradable implant coatings that can also be functionalized with bioactive compounds to modulate the local regenerative tissue environment. © 2014 Wiley Periodicals, Inc.

Electrodeposited silk coatings for bone implants

PubMed Central

Elia, Roberto; Michelson, Courtney D.; Perera, Austin L.; Brunner, Teresa F.; Harsono, Masly; Leisk, Gray G.; Kugel, Gerard; Kaplan, David L.

2014-01-01

The aim of this study was to characterize the mechanical properties and drug elution features of silk protein-based electrodeposited dental implant coatings. Silk processing conditions were modified to obtain coatings with a range of mechanical properties on titanium studs. These coatings were assessed for adhesive strength and dissolution, with properties tuned using water vapor annealing or glycerol incorporation to modulate crystalline content. Coating reproducibility was demonstrated over a range of silk concentrations from 1 to 10%. Surface roughness of titanium substrates was altered using industry relevant acid etching and grit blasting, and the effect of surface topography on silk coating adhesion was assessed. Florescent compounds were incorporated into the silk coatings, which were modulated for crystalline content, to achieve four days of sustained release of the compounds. This silk electrogelation technique offers a safe and relatively simple approach to generate mechanically robust, biocompatible and degradable implant coatings that can also be functionalized with bioactive compounds to modulate the local regenerative tissue environment. PMID:25545462

Investigation of synthetic spider silk crystallinity and alignment via electrothermal, pyroelectric, literature XRD, and tensile techniques.

PubMed

Munro, Troy; Putzeys, Tristan; Copeland, Cameron G; Xing, Changhu; Lewis, Randolph V; Ban, Heng; Glorieux, Christ; Wubbenhorst, Michael

2017-04-01

The processes used to create synthetic spider silk greatly affect the properties of the produced fibers. This paper investigates the effect of process variations during artificial spinning on the thermal and mechanical properties of the produced silk. Property values are also compared to the ones of the natural dragline silk of the N. clavipes spider, and to unprocessed (as-spun) synthetic silk. Structural characterization by scanning pyroelectric microscopy is employed to provide insight into the axial orientation of the crystalline regions of the fiber and is supported by XRD data. The results show that stretching and passage through liquid baths induce crystal formation and axial alignment in synthetic fibers, but with different structural organization than natural silks. Furthermore, an increase in thermal diffusivity and elastic modulus is observed with decreasing fiber diameter, trending towards properties of natural fiber. This effect seems to be related to silk fibers being subjected to a radial gradient during production.

Investigation of synthetic spider silk crystallinity and alignment via electrothermal, pyroelectric, literature XRD, and tensile techniques

PubMed Central

Munro, Troy; Putzeys, Tristan; Copeland, Cameron G.; Xing, Changhu; Lewis, Randolph V; Ban, Heng; Glorieux, Christ; Wubbenhorst, Michael

2018-01-01

The processes used to create synthetic spider silk greatly affect the properties of the produced fibers. This paper investigates the effect of process variations during artificial spinning on the thermal and mechanical properties of the produced silk. Property values are also compared to the ones of the natural dragline silk of the N. clavipes spider, and to unprocessed (as-spun) synthetic silk. Structural characterization by scanning pyroelectric microscopy is employed to provide insight into the axial orientation of the crystalline regions of the fiber and is supported by XRD data. The results show that stretching and passage through liquid baths induce crystal formation and axial alignment in synthetic fibers, but with different structural organization than natural silks. Furthermore, an increase in thermal diffusivity and elastic modulus is observed with decreasing fiber diameter, trending towards properties of natural fiber. This effect seems to be related to silk fibers being subjected to a radial gradient during production. PMID:29430211

Use of spider silk fibres as an innovative material in a biocompatible artificial nerve conduit

PubMed Central

Allmeling, Christina; Jokuszies, Andreas; Reimers, Kerstin; Kall, Susanne; Vogt, Peter M

2006-01-01

Defects of peripheral nerves still represent a challenge for surgical nerve reconstruction. Recent studies concentrated on replacement by artificial nerve conduits from different synthetic or biological materials. In our study, we describe for the first time the use of spider silk fibres as a new material in nerve tissue engineering. Schwann cells (SC) were cultivated on spider silk fibres. Cells adhered quickly on the fibres compared to polydioxanone monofilaments (PDS). SC survival and proliferation was normal in Live/Dead assays. The silk fibres were ensheathed completely with cells. We developed composite nerve grafts of acellularized veins, spider silk fibres and SC diluted in matrigel. These artificial nerve grafts could be cultivated in vitro for one week. Histological analysis showed that the cells were vital and formed distinct columns along the silk fibres. In conclusion, our results show that artificial nerve grafts can be constructed successfully from spider silk, acellularized veins and SC mixed with matrigel. PMID:16989736

Effect of Sericin on Mechanical Behavior of Composite Material Reinforced by Silk Woven Fabric

NASA Astrophysics Data System (ADS)

Kimura, Teruo; Ino, Haruhiro; Hanada, Koji; Katori, Sigetaka

Recent, attention has been given to shift from glass fibers and carbon fibers to natural fibers for FRP composites for the goal of protecting the environment. This paper concerned with the application of silk fabric for composite materials. Polypropylene (PP) was used for the matrix material and the silk fabric composites were molded using a compression molding method. Especially, the effect of sericin on mechanical behaviors of composite materials was discussed. Good adhesion between silk and PP was obtained by removing the sericin existing around the fibroin. The tensile modulus of composite decreased with decreasing the sericin because of the flexibility of silk fibers without sericin. In particular, the higher Izod impact value was obtained for the composites containing the silk fibers without sericin.

Silk-based delivery systems of bioactive molecules.

PubMed

Numata, Keiji; Kaplan, David L

2010-12-30

Silks are biodegradable, biocompatible, self-assembling proteins that can also be tailored via genetic engineering to contain specific chemical features, offering utility for drug and gene delivery. Silkworm silk has been used in biomedical sutures for decades and has recently achieved Food and Drug Administration approval for expanded biomaterials device utility. With the diversity and control of size, structure and chemistry, modified or recombinant silk proteins can be designed and utilized in various biomedical application, such as for the delivery of bioactive molecules. This review focuses on the biosynthesis and applications of silk-based multi-block copolymer systems and related silk protein drug delivery systems. The utility of these systems for the delivery of small molecule drugs, proteins and genes is reviewed. Copyright © 2010 Elsevier B.V. All rights reserved.

Synergistic Integration of Experimental and Simulation Approaches for the de Novo Design of Silk-Based Materials.

PubMed

Huang, Wenwen; Ebrahimi, Davoud; Dinjaski, Nina; Tarakanova, Anna; Buehler, Markus J; Wong, Joyce Y; Kaplan, David L

2017-04-18

Tailored biomaterials with tunable functional properties are crucial for a variety of task-specific applications ranging from healthcare to sustainable, novel bio-nanodevices. To generate polymeric materials with predictive functional outcomes, exploiting designs from nature while morphing them toward non-natural systems offers an important strategy. Silks are Nature's building blocks and are produced by arthropods for a variety of uses that are essential for their survival. Due to the genetic control of encoded protein sequence, mechanical properties, biocompatibility, and biodegradability, silk proteins have been selected as prototype models to emulate for the tunable designs of biomaterial systems. The bottom up strategy of material design opens important opportunities to create predictive functional outcomes, following the exquisite polymeric templates inspired by silks. Recombinant DNA technology provides a systematic approach to recapitulate, vary, and evaluate the core structure peptide motifs in silks and then biosynthesize silk-based polymers by design. Post-biosynthesis processing allows for another dimension of material design by controlled or assisted assembly. Multiscale modeling, from the theoretical prospective, provides strategies to explore interactions at different length scales, leading to selective material properties. Synergy among experimental and modeling approaches can provide new and more rapid insights into the most appropriate structure-function relationships to pursue while also furthering our understanding in terms of the range of silk-based systems that can be generated. This approach utilizes nature as a blueprint for initial polymer designs with useful functions (e.g., silk fibers) but also employs modeling-guided experiments to expand the initial polymer designs into new domains of functional materials that do not exist in nature. The overall path to these new functional outcomes is greatly accelerated via the integration of modeling with experiment. In this Account, we summarize recent advances in understanding and functionalization of silk-based protein systems, with a focus on the integration of simulation and experiment for biopolymer design. Spider silk was selected as an exemplary protein to address the fundamental challenges in polymer designs, including specific insights into the role of molecular weight, hydrophobic/hydrophilic partitioning, and shear stress for silk fiber formation. To expand current silk designs toward biointerfaces and stimuli responsive materials, peptide modules from other natural proteins were added to silk designs to introduce new functions, exploiting the modular nature of silk proteins and fibrous proteins in general. The integrated approaches explored suggest that protein folding, silk volume fraction, and protein amino acid sequence changes (e.g., mutations) are critical factors for functional biomaterial designs. In summary, the integrated modeling-experimental approach described in this Account suggests a more rationally directed and more rapid method for the design of polymeric materials. It is expected that this combined use of experimental and computational approaches has a broad applicability not only for silk-based systems, but also for other polymer and composite materials.

Glycopolymer functionalization of engineered spider silk protein-based materials for improved cell adhesion.

PubMed

Hardy, John G; Pfaff, André; Leal-Egaña, Aldo; Müller, Axel H E; Scheibel, Thomas R

2014-07-01

Silk protein-based materials are promising biomaterials for application as tissue scaffolds, due to their processability, biocompatibility, and biodegradability. The preparation of films composed of an engineered spider silk protein (eADF4(C16)) and their functionalization with glycopolymers are described. The glycopolymers bind proteins found in the extracellular matrix, providing a biomimetic coating on the films that improves cell adhesion to the surfaces of engineered spider silk films. Such silk-based materials have potential as coatings for degradable implantable devices. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Trail and arena marking by caterpillars ofArchips cerasivoranus (lepidoptera: Tortricidae).

PubMed

Fitzgerald, T D

1993-07-01

The activity ofArchips cerasivoranus caterpillars is largely limited to their colonial silk web and trails. Silk pulled directly from the spinnerets of caterpillars and wound onto paper strips to form artificial trails elicited locomotion from the larvae. Trails made from extracts of silk and silk glands also elicited locomotion. These and other observations reported here indicate that the caterpillars are responsive to a water-soluble pheromone that is a component of the silk strand. Marker pheromones appear not to be secreted from other regions of the body, as has been reported for some other trail-following caterpillars.

Second-order nonlinear optical microscopy of spider silk

NASA Astrophysics Data System (ADS)

Zhao, Yue; Hien, Khuat Thi Thu; Mizutani, Goro; Rutt, Harvey N.

2017-06-01

Asymmetric β-sheet protein structures in spider silk should induce nonlinear optical interaction such as second harmonic generation (SHG) which is experimentally observed for a radial line and dragline spider silk using an imaging femtosecond laser SHG microscope. By comparing different spider silks, we found that the SHG signal correlates with the existence of the protein β-sheets. Measurements of the polarization dependence of SHG from the dragline indicated that the β-sheet has a nonlinear response depending on the direction of the incident electric field. We propose a model of what orientation the β-sheet takes in spider silk.

Effect of UV-light on the uniaxial tensile properties and structure of uncoated and TiO2 coated Bombyx mori silk fibers.

PubMed

Aksakal, Baki; Koç, Kenan; Yargı, Önder; Tsobkallo, Katherina

2016-01-05

The effect of UV-light on the uniaxial tensile properties and the structure of uncoated and TiO2 coated silk fibers in the bave form by using sol-gel method was investigated with tensile testing and FT-IR/ATR spectroscopy methods after the silk filaments were exposed to UV-light with high intensity of 760W/m(2) for different times from 0.5h to 1day. It was clearly observed that TiO2 coating considerably increased the Young's modulus of the uncoated silk single filament by around 17% before the UV-irradiation. The yield point and the post yield region disappeared on the stress-strain curves of both uncoated and TiO2 coated silk filaments after UV-irradiation time higher than 1h. Except for the Young's modulus, most of the tensile characteristics of both uncoated and TiO2 coated silk filaments decreased remarkably with increasing UV-irradiation time, e.g., after 1h irradiation, although the Young's modulus slightly changed and ultimate tensile strength decreased by only around 18% and 23%, for the uncoated and TiO2 coated silk filaments, respectively; breaking extension decreased dramatically by 67% and 72%, respectively, for uncoated and TiO2 coated silk filaments. Only the Young's modulus of TiO2 coated silk filaments which can be considered as a more stable tensile characteristic became significantly higher than that of the uncoated silk filaments with increasing UV-irradiation time. After 1day irradiation, even though the uncoated silk filaments could not be tested and completely lost of their fiber properties, the TiO2 coated silk filaments showed a stress-strain curve in initial elastic region with Young's modulus of ∼13GPa which indicates considerable protective effect of TiO2 on the silk fiber structure, especially on the β-sheet microcrystals against UV-radiation. The FT-IR/ATR spectral results showed that significant photodegradation took place in not only crystalline but also amorphous regions which were deduced from the decrease in the absorbance ratios of the bands assigned to CH3 rocking, Cα-Cβ, Cα-C stretching vibrations in β-sheet crystalline regions as well as the Amide I, II, and III bands for both crystalline and amorphous regions. Even though the ratio of crystalline to amorphous regions in uncoated silk filaments decreased significantly, the ratio in TiO2 coated silk filaments became almost constant with increasing UV-irradiation time which may indicate more stable β-sheet microcrystals against photodegradation. Copyright © 2015 Elsevier B.V. All rights reserved.

Silk produced by hornets: thermophotovoltaic properties-a review.

PubMed

Kirshboim, S; Ishay, J S

2000-09-01

This article deals with the silk weave produced by pupating larvae of the Oriental hornet and its electric properties. Larvae of this hornet commence pupation at approximately 2 weeks of age. Creation of the cocoonal silk weave requires a number of hours and the encased pupa remains in the cocoon for approximately 2 more weeks before ecloding as an adult. The silk weave is initially of a creamish white color, but gradually becomes brown-gray owing to the activity of certain bacteria secreted in the silk. The silk weave is composed of fibers arranged in multiple layers with interposed surfaces occupying a considerable part of the area and containing pockets of bacteria. The spun silk contains both metallic and non-metallic elements, mostly K and Cl but also Mg, P, S, Ca, Ti and V. Shaped as a dome, the silk projects considerably beyond the cell proper, contributing importantly to its total volume and providing a shield for the contained pupa against predators, parasites, or extreme changes in temperature, as well as affording a 'sterile and clean room' in which the pupa can form its new cuticle without the interference of contaminating dust particles or the turbulence of air currents. The silk is endowed with electric properties. Inter alia, a thermoelectric phenomenon was observed in the dark, namely, upon increase in temperature the current rose to several hundred nano Amperes (nA); in light, a photovoltaic effect was observed involving voltages of several dozen millivolts (mV), with a sharp transition between the current and voltage during transition from darkness to light. Also recorded was a very high electric capacitance, amounting to scores of milli farads (mF). In all, the pupal silk behaves like an organic semiconductor, in that its electric properties are temperature-dependent, and it also displays ferroelectric properties. Additionally, a luminescence phenomenon was recorded on the silk, wherein excitation at wavelengths within the UV(i.e. 249, 290 and 312 nm) range yielded an emission spectrum at a wavelength of 450 and of 530 nm. The silk caps are anisotropic in that the emission from the outside is lower than that from the inside. By way of recap, the various mentioned properties of the pupal silk are discussed from their biological and physical aspects.

In vivo bioresponses to silk proteins.

PubMed

Thurber, Amy E; Omenetto, Fiorenzo G; Kaplan, David L

2015-12-01

Silks are appealing materials for numerous biomedical applications involving drug delivery, tissue engineering, or implantable devices, because of their tunable mechanical properties and wide range of physical structures. In addition to the functionalities needed for specific clinical applications, a key factor necessary for clinical success for any implanted material is appropriate interactions with the body in vivo. This review summarizes our current understanding of the in vivo biological responses to silks, including degradation, the immune and inflammatory response, and tissue remodeling with particular attention to vascularization. While we focus in this review on silkworm silk fibroin protein due to the large quantity of in vivo data thanks to its widespread use in medical materials and consumer products, spider silk information is also included if available. Silk proteins are degraded in the body on a time course that is dependent on the method of silk fabrication and can range from hours to years. Silk protein typically induces a mild inflammatory response that decreases within a few weeks of implantation. The response involves recruitment and activation of macrophages and may include activation of a mild foreign body response with the formation of multinuclear giant cells, depending on the material format and location of implantation. The number of immune cells present decreases with time and granulation tissue, if formed, is replaced by endogenous, not fibrous, tissue. Importantly, silk materials have not been demonstrated to induce mineralization, except when used in calcified tissues. Due to its ability to be degraded, silk can be remodeled in the body allowing for vascularization and tissue ingrowth with eventual complete replacement by native tissue. The degree of remodeling, tissue ingrowth, or other specific cell behaviors can be modulated with addition of growth or other signaling factors. Silk can also be combined with numerous other materials including proteins, synthetic polymers, and ceramics to enhance its characteristics for a particular function. Overall, the diverse array of silk materials shows excellent bioresponses in vivo with low immunogenicity and the ability to be remodeled and replaced by native tissue making it suitable for numerous clinical applications. Copyright © 2015 Elsevier Ltd. All rights reserved.

Tunable green graphene-silk biomaterials: Mechanism of protein-based nanocomposites.

PubMed

Wang, Fang; Jyothirmayee Aravind, S S; Wu, Hao; Forys, Joseph; Venkataraman, Venkat; Ramanujachary, Kandalam; Hu, Xiao

2017-10-01

Green graphene materials prepared by photoreduction of graphite oxide were first time blended with aqueous-based silk fibroin proteins to improve the mechanical and thermal properties of silk biomaterials, and their nanocomposite interaction mechanism was illustrated. Powder X-ray diffraction (XRD) analysis confirmed the complete exfoliation of graphite oxide to graphene in presence of focused pulses of solar radiation. By varying the concentration of graphene (0.1wt% to 10wt%), a series of free standing graphene-silk films were prepared and were systematically characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and nanoindentation measurements. The homogeneity of graphene in silk as well as the thermal stability of the composite films was demonstrated by thermal gravimetric analysis (TGA) and temperature-modulated differential scanning calorimetry (TMDSC). Surprisingly, silk composite film containing only 0.5wt% of graphene gives the highest Young's modulus of 1.65GPa (about 5.8 times higher than the pure silk's modulus), indicating a nano-composite to micro-composite transition of silk-graphene structure occurred around this mixing ratio. This finding provided an easy approach to improve the elastic modulus and other physical properties of silk materials by adding a tiny amount of graphene sheets. Fibroblast cells studies also proved that these graphene-silk materials can significantly improve cell adhesion, growth and proliferation. This protein nanocomposite study provided a useful model to understand how to manipulate the hydrophobic-hydrophobic and polar-polar interactions between high-surface-area inorganic nanomaterials and amphiphilic protein materials, which has many emerging applications in the material science and engineering, such as bio-device fabrication, drug storage and release, and tissue regeneration. Copyright © 2017 Elsevier B.V. All rights reserved.

Regulation of Silk Material Structure by Temperature-Controlled Water Vapor Annealing

PubMed Central

Hu, Xiao; Shmelev, Karen; Sun, Lin; Gil, Eun-Seok; Park, Sang-Hyug; Cebe, Peggy; Kaplan, David L.

2011-01-01

We present a simple and effective method to obtain refined control of the molecular structure of silk biomaterials through physical temperature-controlled water vapor annealing (TCWVA). The silk materials can be prepared with control of crystallinity, from a low content using conditions at 4°C (alpha-helix dominated silk I structure), to highest content of ~60% crystallinity at 100°C (beta-sheet dominated silk II structure). This new physical approach covers the range of structures previously reported to govern crystallization during the fabrication of silk materials, yet offers a simpler, green chemistry, approach with tight control of reproducibility. The transition kinetics, thermal, mechanical, and biodegradation properties of the silk films prepared at different temperatures were investigated and compared by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), uniaxial tensile studies, and enzymatic degradation studies. The results revealed that this new physical processing method accurately controls structure, in turn providing control of mechanical properties, thermal stability, enzyme degradation rate, and human mesenchymal stem cell interactions. The mechanistic basis for the control is through the temperature controlled regulation of water vapor, to control crystallization. Control of silk structure via TCWVA represents a significant improvement in the fabrication of silk-based biomaterials, where control of structure-property relationships is key to regulating material properties. This new approach to control crystallization also provides an entirely new green approach, avoiding common methods which use organic solvents (methanol, ethanol) or organic acids. The method described here for silk proteins would also be universal for many other structural proteins (and likely other biopolymers), where water controls chain interactions related to material properties. PMID:21425769

Genome sequence of the Japanese oak silk moth, Antheraea yamamai: the first draft genome in the family Saturniidae

PubMed Central

Kim, Seong-Ryul; Kwak, Woori; Kim, Hyaekang; Kim, Kee-Young; Kim, Su-Bae; Choi, Kwang-Ho; Kim, Seong-Wan; Hwang, Jae-Sam; Kim, Minjee; Kim, Iksoo; Goo, Tae-Won

2018-01-01

Abstract Background Antheraea yamamai, also known as the Japanese oak silk moth, is a wild species of silk moth. Silk produced by A. yamamai, referred to as tensan silk, shows different characteristics such as thickness, compressive elasticity, and chemical resistance compared with common silk produced from the domesticated silkworm, Bombyx mori. Its unique characteristics have led to its use in many research fields including biotechnology and medical science, and the scientific as well as economic importance of the wild silk moth continues to gradually increase. However, no genomic information for the wild silk moth, including A. yamamai, is currently available. Findings In order to construct the A. yamamai genome, a total of 147G base pairs using Illumina and Pacbio sequencing platforms were generated, providing 210-fold coverage based on the 700-Mb estimated genome size of A. yamamai. The assembled genome of A. yamamai was 656 Mb (>2 kb) with 3675 scaffolds, and the N50 length of assembly was 739 Kb with a 34.07% GC ratio. Identified repeat elements covered 37.33% of the total genome, and the completeness of the constructed genome assembly was estimated to be 96.7% by Benchmarking Universal Single-Copy Orthologs v2 analysis. A total of 15 481 genes were identified using Evidence Modeler based on the gene prediction results obtained from 3 different methods (ab initio, RNA-seq-based, known-gene-based) and manual curation. Conclusions Here we present the genome sequence of A. yamamai, the first genome sequence of the wild silk moth. These results provide valuable genomic information, which will help enrich our understanding of the molecular mechanisms relating to not only specific phenotypes such as wild silk itself but also the genomic evolution of Saturniidae. PMID:29186418

Forced reeling of Bombyx mori silk: separating behavior and processing conditions.

PubMed

Mortimer, Beth; Holland, Chris; Vollrath, Fritz

2013-10-14

Controlled reeling is a powerful tool to investigate the details of silk processing. However, consistent forced reeling of silkworms is hindered by the significant degree of behaviorally induced variation caused by the animal. This paper proposes silkworm paralysis as a novel method to control the animal and thus in vivo spinning conditions. Using these methods, we achieve low and consistent reeling forces during the collection of over 500 m of individual silk fiber while monitoring filament variability, morphology, and properties. Novel techniques to measure the irregular silk cross-sectional areas lead to the more accurate calculation of the true engineering values and mechanical property variation of individual silk fibers. Combining controlled reeling and accurate thread measurement techniques allows us to present the relative contributions of processing and behavior in the performance envelope of Bombyx mori silk.

Silk Fibroin Aqueous-Based Adhesives Inspired by Mussel Adhesive Proteins.

PubMed

Burke, Kelly A; Roberts, Dane C; Kaplan, David L

2016-01-11

Silk fibroin from the domesticated silkworm Bombyx mori is a naturally occurring biopolymer with charged hydrophilic terminal regions that end-cap a hydrophobic core consisting of repeating sequences of glycine, alanine, and serine residues. Taking inspiration from mussels that produce proteins rich in L-3,4-dihydroxyphenylalanine (DOPA) to adhere to a variety of organic and inorganic surfaces, the silk fibroin was functionalized with catechol groups. Silk fibroin was selected for its high molecular weight, tunable mechanical and degradation properties, aqueous processability, and wide availability. The synthesis of catechol-functionalized silk fibroin polymers containing varying amounts of hydrophilic polyethylene glycol (PEG, 5000 g/mol) side chains was carried out to balance silk hydrophobicity with PEG hydrophilicity. The efficiency of the catechol functionalization reaction did not vary with PEG conjugation over the range studied, although tuning the amount of PEG conjugated was essential for aqueous solubility. Adhesive bonding and cell compatibility of the resulting materials were investigated, where it was found that incorporating as little as 6 wt % PEG prior to catechol functionalization resulted in complete aqueous solubility of the catechol conjugates and increased adhesive strength compared with silk lacking catechol functionalization. Furthermore, PEG-silk fibroin conjugates maintained their ability to form β-sheet secondary structures, which can be exploited to reduce swelling. Human mesenchymal stem cells (hMSCs) proliferated on the silks, regardless of PEG and catechol conjugation. These materials represent a protein-based approach to catechol-based adhesives, which we envision may find applicability as biodegradable adhesives and sealants.

Acute and Subacute Toxicity Evaluation of Corn Silk Extract

PubMed Central

Ha, Ae Wha; Kang, Hyeon Jung; Kim, Sun Lim; Kim, Myung Hwan

2018-01-01

Many studies have reported therapeutic efficacy of corn silk extract. However, research on its toxicity and safe dose range is limited. Thus, the objective of this study was to determine the acute and subacute toxicity of corn silk extract in ICR mice. To determine acute toxicity, corn silk extract containing high levels of maysin was orally administered to mice at a dose of 0 or 2,000 mg/kg. Clinical symptoms, mortality, and body weight changes were recorded for 14 days. To determine subacute toxicity, corn silk extract was orally administered to mice over a 4-week period, and then body weight, water and food consumption, and organ weight were determined. In addition, urine and serum analyses were performed. In the acute toxicity study, no death or abnormal symptoms was observed in all treatment groups during the study period. Body weights did not show any significant change compared to those of the control group. Lethal dose of corn silk extract was estimated to be more than 2,000 mg/kg. In the 4-week subacute toxicity study, there was no corn silk extract related toxic effect on body weight, water intake, food consumption, urine parameters, clinical chemistry, or organ weight. Histopathological examination showed no abnormality related to the administration of corn silk extract at 500 mg/kg. The maximum non-toxic dose of corn silk extract containing high levels of maysin was found to be more than 500 mg/kg. PMID:29662850

Acute and Subacute Toxicity Evaluation of Corn Silk Extract.

PubMed

Ha, Ae Wha; Kang, Hyeon Jung; Kim, Sun Lim; Kim, Myung Hwan; Kim, Woo Kyoung

2018-03-01

Many studies have reported therapeutic efficacy of corn silk extract. However, research on its toxicity and safe dose range is limited. Thus, the objective of this study was to determine the acute and subacute toxicity of corn silk extract in ICR mice. To determine acute toxicity, corn silk extract containing high levels of maysin was orally administered to mice at a dose of 0 or 2,000 mg/kg. Clinical symptoms, mortality, and body weight changes were recorded for 14 days. To determine subacute toxicity, corn silk extract was orally administered to mice over a 4-week period, and then body weight, water and food consumption, and organ weight were determined. In addition, urine and serum analyses were performed. In the acute toxicity study, no death or abnormal symptoms was observed in all treatment groups during the study period. Body weights did not show any significant change compared to those of the control group. Lethal dose of corn silk extract was estimated to be more than 2,000 mg/kg. In the 4-week subacute toxicity study, there was no corn silk extract related toxic effect on body weight, water intake, food consumption, urine parameters, clinical chemistry, or organ weight. Histopathological examination showed no abnormality related to the administration of corn silk extract at 500 mg/kg. The maximum non-toxic dose of corn silk extract containing high levels of maysin was found to be more than 500 mg/kg.

Natural printed silk substrate circuit fabricated via surface modification using one step thermal transfer and reduction graphene oxide

NASA Astrophysics Data System (ADS)

Cao, Jiliang; Huang, Zhan; Wang, Chaoxia

2018-05-01

Graphene conductive silk substrate is a preferred material because of its biocompatibility, flexibility and comfort. A flexible natural printed silk substrate circuit was fabricated by one step transfer of graphene oxide (GO) paste from transfer paper to the surface of silk fabric and reduction of the GO to reduced graphene oxide (RGO) using a simple hot press treatment. The GO paste was obtained through ultrasonic stirring exfoliation under low temperature, and presented excellent printing rheological properties at high concentration. The silk fabric was obtained a surface electric resistance as low as 12.15 KΩ cm-1, in the concentration of GO 50 g L-1 and hot press at 220 °C for 120 s. Though the whiteness and strength decreased with the increasing of hot press temperature and time slowly, the electric conductivity of RGO surface modification silk substrate improved obviously. The surface electric resistance of RGO/silk fabrics increased from 12.15 KΩ cm-1 to 18.05 KΩ cm-1, 28.54 KΩ cm-1 and 32.53 KΩ cm-1 after 10, 20 and 30 washing cycles, respectively. The results showed that the printed silk substrate circuit has excellent washability. This process requires no chemical reductant, and the reduction efficiency and reduction degree of GO is high. This time-effective and environmentally-friendly one step thermal transfer and reduction graphene oxide onto natural silk substrate method can be easily used to production of reduced graphene oxide (RGO) based flexible printed circuit.

Bioactive and UV protective silk materials containing baicalin - The multifunctional plant extract from Scutellaria baicalensis Georgi.

PubMed

Zhou, Yuyang; Yang, Zhi-Yi; Tang, Ren-Cheng

2016-10-01

There has been a phenomenal increase in the research and development of new health and hygiene-related textile products. This work reports a novel approach to develop antibacterial, antioxidant and UV-protective silk using an adsorption technique of baicalin (a bioactive ingredient from the root of Scutellaria baicalensis Georgi). Baicalin displayed high adsorption capability at pH2.75, contributing to the sufficient functionalities on silk. The equilibrium adsorption research showed that the Langmuir isotherm was able to describe the behavior of baicalin, indicating the electrostatic interactions between the ionized carboxyl groups in baicalin and the positively charged amino groups in silk. The treated silk with 2% owf (on the weight of fiber) baicalin exhibited excellent antioxidant activity, high antibacterial activities against Escherichia coli and Staphylococcus aureus, and very good ultraviolet protection ability comparable to that of the commercial benzotriazole ultraviolet absorber. The baicalin treatment had no obvious impact on the functional groups, crystal structure and surface morphology of silk. The functionalities of the treated silk obviously declined after first laundering cycle and slowly decreased in the following washing cycles. Encouraging results demonstrate that the baicalin-functionalized silk is a promising material for protective clothing and medical textiles. Copyright © 2016 Elsevier B.V. All rights reserved.

Effects of alkyl polyglycoside (APG) on Bombyx mori silk degumming and the mechanical properties of silk fibroin fibre.

PubMed

Wang, Fei; Zhang, Yu-Qing

2017-05-01

Alkyl polyglycoside (APG), a nonionic surfactant, is often considered to be a green surfactant and is synthesized using glucose and long chain fatty alcohols. It is used as a degumming agent of Bombyx mori silk fibre in this study for the first time. We studied APG systematically in comparison to the traditional degumming methods, such as aqueous solutions of sodium carbonate (Na 2 CO 3 ) and neutral soap (NS). After repeatedly boiling silk fibres in an aqueous solution of 0.25% APG three times for 30min and using a bath ratio of 1:90-120 (g/mL), sericin was completely removed from the fibre. SDS-PAGE showed that the degumming in APG did not induce an evident breakage of the silk fibroin peptide chains, including the light chain and P25 protein. The tensile properties, thermal analysis, and scanning electron microscopic (SEM) observation of the degummed fibroin fibre all show that APG is a degumming agent similar to NS and far superior to Na 2 CO 3 . These results indicate that APG is an environment-friendly silk degumming/refining agent in the silk textile industry and in the manufacture of silk floss quilts. Copyright © 2017 Elsevier B.V. All rights reserved.

Effect of ionic strength on the interfacial viscoelasticity and stability of silk fibroin at the oil/water interface.

PubMed

Tang, Xiaoxiao; Qiao, Xiuying; Miller, Reinhard; Sun, Kang

2016-12-01

The amphiphilic character and surface activity endows silk fibroin with the ability to reside at fluid interfaces and effectively stabilize emulsions. However, the influence of relevant factors and their actual effect on the interfacial viscoelasticity and stability of silk fibroin at the oil/water interface has received less attention. In the present study, the effect of ionic strength on the interfacial viscoelasticity, emulsification effectiveness and stability of silk fibroin at the oil/water interface was investigated in detail. A higher ion concentration facilitates greater adsorption, stronger molecular interaction and faster structure reorganization of silk fibroin at the oil/water interface, thus causing quicker interfacial saturation adsorption, greater interfacial strength and lower interfacial structural fracture on large deformation. However, the presence of concentrated ions screens the charges in silk fibroin molecules and the zeta potential decreases as a result of electrostatic screening and ion-binding effects, which may result in emulsion droplet coalescence and a decrease in emulsion stability. The positively-charged ions significantly affect the interfacial elasticity and stability of silk fibroin layers at the oil/water interface as a result of the strong electrostatic interactions between counter-ions and the negatively-charged groups of silk fibroin. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

Genome editing of BmFib-H gene provides an empty Bombyx mori silk gland for a highly efficient bioreactor

PubMed Central

Ma, Sanyuan; Shi, Run; Wang, Xiaogang; Liu, Yuanyuan; Chang, Jiasong; Gao, Jie; Lu, Wei; Zhang, Jianduo; Zhao, Ping; Xia, Qingyou

2014-01-01

Evolution has produced some remarkable creatures, of which silk gland is a fascinating organ that exists in a variety of insects and almost half of the 34,000 spider species. The impressive ability to secrete huge amount of pure silk protein, and to store proteins at an extremely high concentration (up to 25%) make the silk gland of Bombyx mori hold great promise to be a cost-effective platform for production of recombinant proteins. However, the extremely low production yields of the numerous reported expression systems greatly hindered the exploration and application of silk gland bioreactors. Using customized zinc finger nucleases (ZFN), we successfully performed genome editing of Bmfib-H gene, which encodes the largest and most abundant silk protein, in B. mori with efficiency higher than any previously reported. The resulted Bmfib-H knocked-out B. mori showed a smaller and empty silk gland, abnormally developed posterior silk gland cells, an extremely thin cocoon that contain only sericin proteins, and a slightly heavier pupae. We also showed that removal of endogenous Bmfib-H protein could significantly increase the expression level of exogenous protein. Furthermore, we demonstrated that the bioreactor is suitable for large scale production of protein-based materials. PMID:25359576

The embryonic origin of the ampullate silk glands of the spider Cupiennius salei.

PubMed

Hilbrant, Maarten; Damen, Wim G M

2015-05-01

Silk production in spiders is considered a key innovation, and to have been vital for the diversification of the clade. The evolutionary origin of the organs involved in spider silk production, however, and in particular of the silk glands, is poorly understood. Homologies have been proposed between these and other glands found in arachnids, but lacking knowledge of the embryonic development of spider silk glands hampers an evaluation of hypotheses. This study focuses on the embryonic origin of the largest silk glands of the spider Cupiennius salei, the major and minor ampullate glands. We show how the ampullate glands originate from ectodermal invaginations on the embryonic spinneret limb buds, in relation to morphogenesis of these buds. Moreover, we visualize the subsequent growth of the ampullate glands in sections of the early postembryonic stages. The invaginations are shown to correlate with expression of the proneural gene CsASH2, which is remarkable since it has been proposed that spider silk glands and their nozzles originate from sensory bristles. Hence, by confirming the ectodermal origin of spider silk glands, and by describing the (post-)embryonic morphogenesis of the ampullate glands, this work provides a starting point for further investigating into the genetic program that underlies their development. Copyright © 2015 Elsevier Ltd. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Kang; Wu, Sujun; Guan, Juan

Strong and tough epoxy composites are developed using a less-studied fibre reinforcement, that of natural silk. Two common but structurally distinct silks from the domestic B. mori/Bm and the wild A. pernyi/Ap silkworms are selected in fabric forms. We show that the toughening effects on silk-epoxy composites or SFRPs are dependent on the silk species and the volume fraction of silk. Both silks enhance the room-temperature tensile and flexural mechanical properties of the composite, whereas the more resilient Ap silk shows a more pronounced toughening effect and a lower critical reinforcement volume for the brittle-ductile transition. Specifically, our 60 vol.%more » Ap-SFRP displays a three-fold elevation in tensile and flexural strength, as compared to pure epoxy resin, with an order of magnitude higher breaking energy via a distinct, ductile failure mode. Importantly, the 60 vol.% Ap-SFRP remains ductile with 7% flexural elongation at lower temperatures (-50 °C). Under impact, these SFRPs show significantly improved energy absorption, and the 60 vol.% Ap-SFRP has an impact strength some eight times that of pure epoxy resin. Lastly, the findings demonstrate both marked toughening and strengthening effects for epoxy composites from natural silk reinforcements, which presents opportunities for mechanically superior and "green" structural composites.« less

Strength of silk attachment to Ilex chinensis leaves in the tea bagworm Eumeta minuscula (Lepidoptera, Psychidae)

PubMed Central

Lovtsova, Julia; Gorb, Elena; Dai, Zhendong; Ji, Aihong; Zhao, Zhihui; Jiang, Nan; Gorb, Stanislav N.

2017-01-01

Silks play an important role in the life of various arthropods. A highly neglected prerequisite to make versatile use of silks is sufficient attachment to substrates. Although there have been some studies on the structure and mechanics of silk anchorages of spiders, for insects only anecdotal reports on attachment-associated spinning behaviour exist. Here, we experimentally studied the silk attachment of the pupae and last instar caterpillars of the tea bagworm Eumeta minuscula (Butler 1881) (Lepidoptera, Psychidae) to the leaves of its host plant Ilex chinensis. We found that the bagworms spin attachment discs, which share some structural features with those of spiders, like a plaque consisting of numerous overlaid, looped glue-coated silk fibres and the medially attaching suspension thread. Although the glue, which coats the fibres, cannot spread and adhere very well to the leaf surface, high pull-off forces were measured, yielding a mean safety factor (force divided by the animal weight) of 385.6. Presumably, the bagworms achieve this by removal of the leaf epidermis prior to silk attachment, which exposes the underlying tissue that represents a much better bonding site. This ensures a reliable attachment during the immobile, vulnerable pupal stage. This is the first study on the biomechanics and structure of silk attachments to substrates in insects. PMID:28250101

Flame retardant and hydrophobic properties of novel sol-gel derived phytic acid/silica hybrid organic-inorganic coatings for silk fabric

NASA Astrophysics Data System (ADS)

Cheng, Xian-Wei; Liang, Cheng-Xi; Guan, Jin-Ping; Yang, Xu-Hong; Tang, Ren-Cheng

2018-01-01

In this work, a novel phosphorus-rich hybrid organic-inorganic silica coating for improving the flame retardancy of silk fabric was prepared using naturally occurring phytic acid as phosphorus precursor and catalyst for the hydrolysis of tetraethoxysilane. In addition, three silane coupling agents, namely 3-aminopropyldimethoxymethylsilane, 3-chloropropyltrimethoxysilane and 3-methacryloxypropyltrimethoxysilane, were added in the hybrid sol as cross-linkers with the aim of developing hydrophobic coatings and improving the washing durability of the treated silk fabric. The condensation degree of the hybrid sol was characterized by solid-state 29Si nuclear magnetic resonance spectroscopy. The flammability and thermal degradation properties of the treated silk fabrics were determined in terms of limiting oxygen index, vertical burning, pyrolysis combustion flow calorimetry and thermogravimetric analyses. The surface morphology and hydrophobicity of the treated silk fabrics were evaluated by scanning electron microscopy, atomic force microscopy and water contact angle tests. The flammability tests revealed that the silicon sol could endow silk fabric with excellent flame retardancy when doped with phytic acid, and the treated silk fabrics self-extinguished immediately when the ignition source was removed. The silk fabrics treated with the modified hybrid sols exhibited hydrophobic surface and also better durability to washing.

Recombinant production and film properties of full-length hornet silk proteins.

PubMed

Kambe, Yusuke; Sutherland, Tara D; Kameda, Tsunenori

2014-08-01

Full-length versions of the four main components of silk cocoons of Vespa simillima hornets, Vssilk1-4, were produced as recombinant proteins in Escherichia coli. In shake flasks, the recombinant Vssilk proteins yielded 160-330mg recombinant proteinl(-1). Films generated from solutions of single Vssilk proteins had a secondary structure similar to that of films generated from native hornet silk. The films made from individual recombinant hornet silk proteins had similar or enhanced mechanical performance compared with films generated from native hornet silk, possibly reflecting the homogeneity of the recombinant proteins. The pH-dependent changes in zeta (ζ) potential of each Vssilk film were measured, and isoelectric points (pI) of Vssilk1-4 were determined as 8.9, 9.1, 5.0 and 4.2, respectively. The pI of native hornet silk, a combination of the four Vssilk proteins, was 4.7, a value similar to that of Bombyx mori silkworm silk. Films generated from Vssilk1 and 2 had net positive charge under physiological conditions and showed significantly higher cell adhesion activity. It is proposed that recombinant hornet silk is a valuable new material with potential for cell culture applications. Copyright © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Titanium dioxide nanoparticles relieve silk gland damage and increase cocooning of Bombyx mori under phoxim-induced toxicity.

PubMed

Li, Bing; Yu, Xiaohong; Gui, Suxin; Xie, Yi; Hong, Jie; Zhao, Xiaoyang; Sheng, Lei; Sang, Xuezi; Sun, Qingqing; Wang, Ling; Shen, Weide; Hong, Fashui

2013-12-18

Organophosphate pesticides are applied widely in the world for agricultural purposes, and their exposures often resulted in non-cocooning of Bombyx mori in China. TiO2 nanoparticles have been demonstrated to increase pesticide resistance of Bombyx mori. While the toxicity of phoxim is well-documented, very limited information exists on the mechanisms of TiO2 nanoparticles improving the cocooning function of Bombyx mori following exposure to phoxim. The present study was, therefore, undertaken to determine whether TiO2 nanoparticles attenuate silk gland injury and elevate cocooning of B. mori following exposure to phoxim. The findings suggested that phoxim exposure resulted in severe damages of the silk gland structure and significantly decreased the cocooning in the silk gland of Bombyx mori. Furthermore, phoxim exposure significantly resulted in reductions of total protein concentrations and suppressed expressions of silk protein synthesis-related genes, including Fib-L, Fib-H, P25, Ser-2, and Ser-3, in the silk gland. TiO2 nanoparticle pretreatment, however, could significantly relieve silk gland injury of Bombyx mori. Importantly, TiO2 nanoparticles could remarkably elevate cocooning and total protein contents and promote expressions of Fib-L, Fib-H, P25, Ser-2, and Ser-3 in the silk gland following exposure to phoxim.

Folding process of silk fibroin induced by ferric and ferrous ions

NASA Astrophysics Data System (ADS)

Ji, Dan; Deng, Yi-Bin; Zhou, Ping

2009-12-01

Bombyx mori silk fiber has useful mechanical properties largely due to a high content of ordered β-sheet crystallites separated by non-crystalline spacers. Metallic ions present in the silk dope in nature could affect the β-sheet content. In this work, we used solid-state 13C NMR, EPR and Raman spectroscopy to investigate how the ferric/ferrous ions affect the folding process of the silk fibroin. NMR and Raman results indicate that ferric and ferrous ions have different effects on the secondary structure of silk fibroin. Ferric ions can induce a conformation change from helix to β-sheet form in silk fibroin when their concentration exceeds a critical value, while ferrous ions cannot. EPR results indicate that the ferric ions bound with silk fibroin have a high-spin state ( S = 5/2) with g-value of g1 = 1.950, g2 = 1.990 and g3 = 1.995, zero-field splitting interaction D of 1.2-2 cm -1, and symmetric character of E/ D = 1/3, resulting in an effective g-value of g' = 4.25. The hydrophilic spacer GTGSSGFGPYVAN(H)GGYSGYEYAWSSESDFGT in the heavy chain of silk fibroin is likely to be involved in the binding of ferric ions, and His, Asn and Tyr residues are considered as the potential binding sites.

Structure-function-property-design interplay in biopolymers: spider silk.

PubMed

Tokareva, Olena; Jacobsen, Matthew; Buehler, Markus; Wong, Joyce; Kaplan, David L

2014-04-01

Spider silks have been a focus of research for almost two decades due to their outstanding mechanical and biophysical properties. Recent advances in genetic engineering have led to the synthesis of recombinant spider silks, thus helping to unravel a fundamental understanding of structure-function-property relationships. The relationships between molecular composition, secondary structures and mechanical properties found in different types of spider silks are described, along with a discussion of artificial spinning of these proteins and their bioapplications, including the role of silks in biomineralization and fabrication of biomaterials with controlled properties. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Different Types of Peptide Detected by Mass Spectrometry among Fresh Silk and Archaeological Silk Remains for Distinguishing Modern Contamination

PubMed Central

Li, Li; Gong, Yuxuan; Yin, Hao; Gong, Decai

2015-01-01

Archaeological silk provides abundant information for studying ancient technologies and cultures. However, due to the spontaneous degradation and the damages from burial conditions, most ancient silk fibers which suffered the damages for thousands of years were turned into invisible molecular residues. For the obtained rare samples, extra care needs to be taken to accurately identify the genuine archaeological silk remains from modern contaminations. Although mass spectrometry (MS) is a powerful tool for identifying and analyzing the ancient protein residues, the traditional approach could not directly determine the dating and contamination of each sample. In this paper, a series of samples with a broad range of ages were tested by MS to find an effective and innovative approach to determine whether modern contamination exists, in order to verify the authenticity and reliability of the ancient samples. The new findings highlighted that the detected peptide types of the fibroin light chain can indicate the degradation levels of silk samples and help to distinguish contamination from ancient silk remains. PMID:26186676

Sericin Promotes Fibroin Silk I Stabilization Across a Phase-Separation.

PubMed

Kwak, Hyo Won; Ju, Ji Eun; Shin, Munju; Holland, Chris; Lee, Ki Hoon

2017-08-14

Natural silk spinning offers several advantages over the synthetic fiber spinning, although the underlying mechanisms of this process are yet to be fully elucidated. Silkworm silks, specifically B. mori, comprise two main proteins: fibroin, which forms the fiber, and sericin, a coextruded coating that acts as a matrix in the resulting nonwoven composite cocoon. To date, most studies have focused on fibroin's self-assembly and gelation, with the influence of sericin during spinning receiving little to no attention. This study investigates sericin's effects on the self-assembly of fibroin via their natural phase-separation. Through changes in sample opacity, FTIR, and XRD, we report that increasing sericin concentration retards the time to gelation and β-sheet formation of fibroin, causing it to adopt a Silk I conformation. Such findings have important implications for both the natural silk spinning process and any future industrial applications, suggesting that sericin may be able to induce long-range conformational and stability control in silk fibroin, while being in a separate phase, a factor that would facilitate long-term storage or silk feedstocks.

Phase separation and mechanical properties of an elastomeric biomaterial from spider wrapping silk and elastin block copolymers.

PubMed

Muiznieks, Lisa D; Keeley, Fred W

2016-10-01

Elastin and silk spidroins are fibrous, structural proteins with elastomeric properties of extension and recoil. While elastin is highly extensible and has excellent recovery of elastic energy, silks are particularly strong and tough. This study describes the biophysical characterization of recombinant polypeptides designed by combining spider wrapping silk and elastin-like sequences as a strategy to rationally increase the strength of elastin-based materials while maintaining extensibility. We demonstrate a thermo-responsive phase separation and spontaneous colloid-like droplet formation from silk-elastin block copolymers, and from a 34 residue disordered region of Argiope trifasciata wrapping silk alone, and measure a comprehensive suite of tensile mechanical properties from cross-linked materials. Silk-elastin materials exhibited significantly increased strength, toughness, and stiffness compared to an elastin-only material, while retaining high failure strains and low energy loss upon recoil. These data demonstrate the mechanical tunability of protein polymer biomaterials through modular, chimeric recombination, and provide structural insights into mechanical design. © 2016 Wiley Periodicals, Inc. Biopolymers 105: 693-703, 2016. © 2016 Wiley Periodicals, Inc.

Hunting with sticky tape: functional shift in silk glands of araneophagous ground spiders (Gnaphosidae).

PubMed

Wolff, Jonas O; Řezáč, Milan; Krejčí, Tomáš; Gorb, Stanislav N

2017-06-15

Foraging is one of the main evolutionary driving forces shaping the phenotype of organisms. In predators, a significant, though understudied, cost of foraging is the risk of being injured by struggling prey. Hunting spiders that feed on dangerous prey like ants or other spiders are an extreme example of dangerous feeding, risking their own life over a meal. Here, we describe an intriguing example of the use of attachment silk (piriform silk) for prey immobilization that comes with the costs of reduced silk anchorage function, increased piriform silk production and additional modifications of the extrusion structures (spigots) to prevent their clogging. We show that the piriform silk of gnaphosids is very stretchy and tough, which is an outstanding feat for a functional glue. This is gained by the combination of an elastic central fibre and a bi-layered glue coat consisting of aligned nanofibrils. This represents the first tensile test data on the ubiquitous piriform gland silk, adding an important puzzle piece to the mechanical catalogue of silken products in spiders. © 2017. Published by The Company of Biologists Ltd.

Review structure of silk by raman spectromicroscopy: from the spinning glands to the fibers.

PubMed

Lefèvre, Thierry; Paquet-Mercier, François; Rioux-Dubé, Jean-François; Pézolet, Michel

2012-06-01

Raman spectroscopy has long been proved to be a useful tool to study the conformation of protein-based materials such as silk. Thanks to recent developments, linearly polarized Raman spectromicroscopy has appeared very efficient to characterize the molecular structure of native single silk fibers and spinning dopes because it can provide information relative to the protein secondary structure, molecular orientation, and amino acid composition. This review will describe recent advances in the study of the structure of silk by Raman spectromicroscopy. A particular emphasis is put on the spider dragline and silkworm cocoon threads, other fibers spun by orb-weaving spiders, the spinning dope contained in their silk glands and the effect of mechanical deformation. Taken together, the results of the literature show that Raman spectromicroscopy is particularly efficient to investigate all aspects of silk structure and production. The data provided can lead to a better understanding of the structure of the silk dope, transformations occurring during the spinning process, and structure and mechanical properties of native fibers. Copyright © 2011 Wiley Periodicals, Inc.

Human Corneal Limbal-Epithelial Cell Response to Varying Silk Film Geometric Topography In Vitro

PubMed Central

Lawrence, Brian D.; Pan, Zhi; Liu, Aihong; Kaplan, David L.; Rosenblatt, Mark I.

2012-01-01

Silk fibroin films are a promising class of biomaterials that have a number of advantages for use in ophthalmic applications due to their transparent nature, mechanical properties and minimal inflammatory response upon implantation. Freestanding silk films with parallel line and concentric ring topographies were generated for in vitro characterization of human corneal limbal-epithelial (HCLE) cell response upon differing geometric patterned surfaces. Results indicated that silk film topography significantly affected initial HCLE culture substrate attachment, cellular alignment, cell-to-cell contact formation, actin cytoskeleton alignment, and focal adhesion (FA) localization. Most notably, parallel line patterned surfaces displayed a 36%–54% increase on average in initial cell attachment, which corresponded to an over 2-fold increase in FA localization when compared to other silk film surfaces and controls. In addition, distinct localization of FA formation was observed along the edges for all patterned silk film topographies. In conclusion, silk film feature topography appears to help direct corneal epithelial cell response and cytoskeleton development, especially in regards to FA distribution, in vitro. PMID:22705042

Role of chondroitin sulphate tethered silk scaffold in cartilaginous disc tissue regeneration.

PubMed

Bhattacharjee, Maumita; Chawla, Shikha; Chameettachal, Shibu; Murab, Sumit; Bhavesh, Neel Sarovar; Ghosh, Sourabh

2016-04-12

Strategies for tissue engineering focus on scaffolds with tunable structure and morphology as well as optimum surface chemistry to simulate the anatomy and functionality of the target tissue. Silk fibroin has demonstrated its potential in supporting cartilaginous tissue formation both in vitro and in vivo. In this study, we investigate the role of controlled lamellar organization and chemical composition of biofunctionalized silk scaffolds in replicating the structural properties of the annulus region of an intervertebral disc using articular chondrocytes. Covalent attachment of chondroitin sulfate (CS) to silk is characterized. CS-conjugated silk constructs demonstrate enhanced cellular metabolic activity and chondrogenic redifferentiation potential with significantly improved mechanical properties over silk-only constructs. A matrix-assisted laser desorption ionization-time of flight analysis and protein-protein interaction studies help to generate insights into how CS conjugation can facilitate the production of disc associated matrix proteins, compared to a silk-only based construct. An in-depth understanding of the interplay between such extra cellular matrix associated proteins should help in designing more rational scaffolds for cartilaginous disc regeneration needs.

Natural Silk as a Photonics Component: a Study on Its Light Guiding and Nonlinear Optical Properties

NASA Astrophysics Data System (ADS)

Kujala, Sami; Mannila, Anna; Karvonen, Lasse; Kieu, Khanh; Sun, Zhipei

2016-03-01

Silk fibers are expected to become a pathway to biocompatible and bioresorbable waveguides, which could be used to deliver localized optical power for various applications, e.g., optical therapy or imaging inside living tissue. Here, for the first time, the linear and nonlinear optical properties of natural silk fibers have been studied. The waveguiding properties of silk fibroin of largely unprocessed Bombyx mori silkworm silk are assessed using two complementary methods, and found to be on the average 2.8 dB mm-1. The waveguide losses of degummed silk are to a large extent due to scattering from debris on fiber surface and helical twisting of the fiber. Nonlinear optical microscopy reveals both configurational defects such as torsional twisting, and strong symmetry breaking at the center of the fiber, which provides potential for various nonlinear applications. Our results show that nonregenerated B. mori silk can be used for delivering optical power over short distances, when the waveguide needs to be biocompatible and bioresorbable, such as embedding the waveguide inside living tissue.

X-ray diffraction study of nanocrystalline and amorphous structure within major and minor ampullate dragline spider silks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sampath, Sujatha; Isdebski, Thomas; Jenkins, Janelle E.

Synchrotron X-ray micro-diffraction experiments were carried out on Nephila clavipes (NC) and Argiope aurantia (AA) major (MA) and minor ampullate (MiA) fibers that make up dragline spider silk. The diffraction patterns show a semi-crystalline structure with {beta}-poly(L-alanine) nanocrystallites embedded in a partially oriented amorphous matrix. A superlattice reflection 'S' diffraction ring is observed, which corresponds to a crystalline component larger in size and is poorly oriented, when compared to the {beta}-poly(L-alanine) nanocrystallites that are commonly observed in dragline spider silks. Crystallite size, crystallinity and orientation about the fiber axis have been determined from the wide-angle X-ray diffraction (WAXD) patterns. Inmore » both NC and AA, the MiA silks are found to be more highly crystalline, when compared with the corresponding MA silks. Detailed analysis on the amorphous matrix shows considerable differences in the degree of order of the oriented amorphous component between the different silks studied and may play a crucial role in determining the mechanical properties of the silks.« less

Biomolecular Evidence of Silk from 8,500 Years Ago

PubMed Central

Gong, Yuxuan; Li, Li; Gong, Decai; Yin, Hao; Zhang, Juzhong

2016-01-01

Pottery, bone implements, and stone tools are routinely found at Neolithic sites. However, the integrity of textiles or silk is susceptible to degradation, and it is therefore very difficult for such materials to be preserved for 8,000 years. Although previous studies have provided important evidence of the emergence of weaving skills and tools, such as figuline spinning wheels and osseous lamellas with traces of filament winding, there is a lack of direct evidence proving the existence of silk. In this paper, we explored evidence of prehistoric silk fibroin through the analysis of soil samples collected from three tombs at the Neolithic site of Jiahu. Mass spectrometry was employed and integrated with proteomics to characterize the key peptides of silk fibroin. The direct biomolecular evidence reported here showed the existence of prehistoric silk fibroin, which was found in 8,500-year-old tombs. Rough weaving tools and bone needles were also excavated, indicating the possibility that the Jiahu residents may possess the basic weaving and sewing skills in making textile. This finding may advance the study of the history of silk, and the civilization of the Neolithic Age. PMID:27941996

Functionalized bioengineered spider silk spheres improve nuclease resistance and activity of oligonucleotide therapeutics providing a strategy for cancer treatment.

PubMed

Kozlowska, Anna Karolina; Florczak, Anna; Smialek, Maciej; Dondajewska, Ewelina; Mackiewicz, Andrzej; Kortylewski, Marcin; Dams-Kozlowska, Hanna

2017-09-01

Cell-selective delivery and sensitivity to serum nucleases remain major hurdles to the clinical application of RNA-based oligonucleotide therapeutics, such as siRNA. Spider silk shows great potential as a biomaterial due to its biocompatibility and biodegradability. Self-assembling properties of silk proteins allow for processing into several different morphologies such as fibers, scaffolds, films, hydrogels, capsules and spheres. Moreover, bioengineering of spider silk protein sequences can functionalize silk by adding peptide moieties with specific features including binding or cell recognition domains. We demonstrated that modification of silk protein by adding the nucleic acid binding domain enabled the development of a novel oligonucleotide delivery system that can be utilized to improve pharmacokinetics of RNA-based therapeutics, such as CpG-siRNA. The MS2 bioengineered silk was functionalized with poly-lysine domain (KN) to generate hybrid silk MS2KN. CpG-siRNA efficiently bound to MS2KN in contrary to control MS2. Both MS2KN complexes and spheres protected CpG-siRNA from degradation by serum nucleases. CpG-siRNA molecules encapsulated into MS2KN spheres were efficiently internalized and processed by TLR9-positive macrophages. Importantly, CpG-STAT3siRNA loaded in silk spheres showed delayed and extended target gene silencing compared to naked oligonucleotides. The prolonged Stat3 silencing resulted in the more pronounced downregulation of interleukin 6 (IL-6), a proinflammatory cytokine and upstream activator of STAT3, which limits the efficacy of TLR9 immunostimulation. Our results demonstrate the feasibility of using spider silk spheres as a carrier of therapeutic nucleic acids. Moreover, the modified kinetic and activity of the CpG-STAT3siRNA embedded into silk spheres is likely to improve immunotherapeutic effects in vivo. We demonstrated that modification of silk protein by adding the nucleic acid binding domain enabled the development of a novel oligonucleotide delivery system that can be utilized to improve pharmacokinetics of RNA-based therapeutics. Although, the siRNA constructs have already given very promising results in the cancer therapy, the in vivo application of RNA-based oligonucleotide therapeutics still is limited due to their sensitivity to serum nucleases and some toxicity. We propose a carrier for RNA-based therapeutics that is made of bioengineered spider silk. We showed that functionalized bioengineered spider silk spheres not only protected RNA-based therapeutics from degradation by serum nucleases, but what is more important the embedding of siRNA into silk spheres delayed and extended target gene silencing compared with naked oligonucleotides. Moreover, we showed that plain silk spheres did not have unspecific effect on target gene levels proving not only to be non-cytotoxic but also very neutral vehicles in terms of TLR9/STAT3 activation in macrophages. We demonstrated advantages of novel delivery technology in safety and efficacy comparing with delivery of naked CpG-STAT3siRNA therapeutics. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Dissolvable Films of Silk Fibroin for Ultrathin Conformal Bio-integrated Electronics

DTIC Science & Technology

2010-01-01

spin- cast films of polyimide (PI) served as a support for arrays of electrodes designed for passive neural recording. Control devices consisted of...optically transparent, mechanically robust, biocompatible silk fibroin films. Adv. Mater. 20, 3070–3072 (2008). 20. Murphy, A. R., John, P. S. & Kaplan, D...induced colour change on periodically nanopatterned silk films. Opt. Express 17, 21271–21279 (2009). 25. Parker, S. T. et al. Biocompatible silk printed

Self-Assembly of a Modular Polypeptide Based on Blocks of Silk-Mimetic and Elastin-Mimetic Sequences

DTIC Science & Technology

2002-04-01

Silk -Mimetic and Elastin-Mimetic Sequences DISTRIBUTION: Approved for public release, distribution unlimited This paper is part of the following...724 © 2002 Materials Research Society N3.8 Self-Assembly of a Modular Polypeptide based on Blocks of Silk -Mimetic and Elastin- Mimetic Sequences...Chrystelle S. Cazalis, and Vincent P. Conticello* Department of Chemistry, Emory University, Atlanta, GA 30322 ABSTRACT Spider dragline silk fiber displays

Antibacterial effect of silk treated with silver and copper nanoparticles synthesized by pulsed laser ablation in distilled water

NASA Astrophysics Data System (ADS)

Baruah, Prahlad K.; Raman, Moghe A.; Chakrabartty, Ishani; Rangan, Latha; Sharma, Ashwini K.; Khare, Alika

2018-05-01

The antibacterial activity of three kinds of silks viz. Eri, Pat and Muga treated with silver and copper nanoparticles is reported in this paper. The nanoparticles have been synthesized by pulsed laser ablation of the respective metal targets in distilled water. Treatment of the silk pellets with the synthesized nanoparticles exhibited definite antibacterial activity whereas no such activity is observed in the untreated silk pellets.

Processing, Properties and Morphology of Optical Limiting Silk Membranes

DTIC Science & Technology

2006-02-28

Christopher Brewer, Donald Ott, Polymer, 45 8451 (2004). 2. Electrospun Bombyx mori Gland Silk, S. Putthanarat, R.K. Eby, W. Kataphinan, S. Jones, R...Science, The University of Akron, Akron, OH. 3. American Physical Society (APS) meeting, March 2005, "Electrospun liquid silk from the gland of Bombyx Mori ...provide a good compatible matrix. They have previously demonstrated that GFP molecules can be incorporated into cast membranes of silk from B. mori

Corn silk induces nitric oxide synthase in murine macrophages.

PubMed

Kim, Kyung A; Choi, Sang Kyu; Choi, Hye Seon

2004-12-31

Corn silk has been purified as an anticoagulant previously and the active component is a polysaccharide with a molecular mass of 135 kDa. It activates murine macrophages to induce nitric oxide synthase (NOS) and generate substantial amounts of NO in time and dose-dependent manners. It was detectable first at 15 h after stimulation by corn silk, peaked at 24 h, and undetectable by 48 h. Induction of NOS is inhibited by pyrolidine dithiocarbamate (PDTC) and genistein, an inhibitor of nuclear factor kappa B (NF-kappaB) and tyrosine kinase, respectively, indicating that iNOS stimulated by corn silk is associated with tyrosine kinase and NF-kappaB signaling pathways. IkappaB-alpha degradation was detectible at 10 min, and the level was restored at 120 min after treatment of corn silk. Corn silk induced nuclear translocation of NF-kappaB by phosphorylation and degradation of IkappaB-alpha.

Effects of the amino acid sequence on thermal conduction through β-sheet crystals of natural silk protein.

PubMed

Zhang, Lin; Bai, Zhitong; Ban, Heng; Liu, Ling

2015-11-21

Recent experiments have discovered very different thermal conductivities between the spider silk and the silkworm silk. Decoding the molecular mechanisms underpinning the distinct thermal properties may guide the rational design of synthetic silk materials and other biomaterials for multifunctionality and tunable properties. However, such an understanding is lacking, mainly due to the complex structure and phonon physics associated with the silk materials. Here, using non-equilibrium molecular dynamics, we demonstrate that the amino acid sequence plays a key role in the thermal conduction process through β-sheets, essential building blocks of natural silks and a variety of other biomaterials. Three representative β-sheet types, i.e. poly-A, poly-(GA), and poly-G, are shown to have distinct structural features and phonon dynamics leading to different thermal conductivities. A fundamental understanding of the sequence effects may stimulate the design and engineering of polymers and biopolymers for desired thermal properties.

Bioengineered porous composite curcumin/silk scaffolds for cartilage regeneration.

PubMed

Kim, Do Kyung; In Kim, Jeong; Sim, Bo Ra; Khang, Gilson

2017-09-01

Articular cartilage repair is a challenge due to its limited self-repair capacity. Cartilage tissue engineering supports to overcome following injuries or degenerative diseases. Herein, we fabricated the scaffold composed of curcumin and silk fibroin as an appropriate clinical replacement for defected cartilage. The scaffolds were designed to have adequate pore size and mechanical strength for cartilage repair. Cell proliferation, sulfated glycosaminoglycan (sGAG) content and mRNA expression analysis indicated that chondrocytes remained viable and showed its growth ability in the curcumin/silk scaffolds. Especially, in 1mg/ml curcumin/silk scaffold showed higher cell viability rate and extracellular matrix formation than other experimental groups. Furthermore, curcumin/silk scaffold showed its biocompatibility and favorable environment for cartilage repair after transplantation in vivo, as indicated in histological examination results. Overall, the functional composite curcumin/silk scaffold can be applied in cartilage tissue engineering and promising substrate for cartilage repair. Copyright © 2017. Published by Elsevier B.V.

The complexity of silk under the spotlight of synthetic biology.

PubMed

Vollrath, Fritz

2016-08-15

For centuries silkworm filaments have been the focus of R&D innovation centred on textile manufacture with high added value. Most recently, silk research has focused on more fundamental issues concerning bio-polymer structure-property-function relationships. This essay outlines the complexity and fundamentals of silk spinning, and presents arguments for establishing this substance as an interesting and important subject at the interface of systems biology (discovery) and synthetic biology (translation). It is argued that silk is a generic class of materials where each type of silk presents a different embodiment of emergent properties that combine genetically determined (anticipatory) and environmentally responsive components. In spiders' webs the various silks have evolved to form the interactive components of an intricate fabric that provides an extended phenotype to the spider's body morphology. © 2016 The Author(s). published by Portland Press Limited on behalf of the Biochemical Society.

Optical surface profiling of orb-web spider capture silks.

PubMed

Kane, D M; Joyce, A M; Staib, G R; Herberstein, M E

2010-09-01

Much spider silk research to date has focused on its mechanical properties. However, the webs of many orb-web spiders have evolved for over 136 million years to evade visual detection by insect prey. It is therefore a photonic device in addition to being a mechanical device. Herein we use optical surface profiling of capture silks from the webs of adult female St Andrews cross spiders (Argiope keyserlingi) to successfully measure the geometry of adhesive silk droplets and to show a bowing in the aqueous layer on the spider capture silk between adhesive droplets. Optical surface profiling shows geometric features of the capture silk that have not been previously measured and contributes to understanding the links between the physical form and biological function. The research also demonstrates non-standard use of an optical surface profiler to measure the maximum width of a transparent micro-sized droplet (microlens).

Investigation of Natural Bombyx mori Silk Fibroin Proteins Using INS

NASA Astrophysics Data System (ADS)

Crain, Christopher; Strange, Nicholas; Larese, J. Z.

The mechanical properties of many protein comprised biomaterials are a direct reflection of non-covalent (i.e. weak) interacting ions such as F-actin in muscles, tubulin in the cytoskeleton of cells, viral capsids, and silk. Porter and Vollrath underscored the two main factors that are critical for understanding the high mechanical strength of silks: the nanoscale semi-crystalline folding structure, which gives it exceptional toughness and strength, and the degree of hydration of the disordered fraction, which acts to modify these properties. Understanding and controlling these two principal factors are the key to the functionality of protein elastomers, and render silk an ideal model protein for (bio)material design. We will describe our investigation of electrospun silk of the Bombyx mori (silk worm), using Inelastic Neutron Scattering (INS). These techniques were used to investigate the microscopic dynamics of the dry and hydrated protein.

Flexible, highly sensitive pressure sensor with a wide range based on graphene-silk network structure

NASA Astrophysics Data System (ADS)

Liu, Ying; Tao, Lu-Qi; Wang, Dan-Yang; Zhang, Tian-Yu; Yang, Yi; Ren, Tian-Ling

2017-03-01

In this paper, a flexible, simple-preparation, and low-cost graphene-silk pressure sensor based on soft silk substrate through thermal reduction was demonstrated. Taking silk as the support body, the device had formed a three-dimensional structure with ordered multi-layer structure. Through a simple and low-cost process technology, graphene-silk pressure sensor can achieve the sensitivity value of 0.4 kPa - 1 , and the measurement range can be as high as 140 kPa. Besides, pressure sensor can have a good combination with knitted clothing and textile product. The signal had good reproducibility in response to different pressures. Furthermore, graphene-silk pressure sensor can not only detect pressure higher than 100 kPa, but also can measure weak body signals. The characteristics of high-sensitivity, good repeatability, flexibility, and comfort for skin provide the high possibility to fit on various wearable electronics.

Nanoparticle self-assembly by a highly stable recombinant spider wrapping silk protein subunit.

PubMed

Xu, Lingling; Tremblay, Marie-Laurence; Orrell, Kathleen E; Leclerc, Jérémie; Meng, Qing; Liu, Xiang-Qin; Rainey, Jan K

2013-10-01

Artificial spider silk proteins may form fibers with exceptional strength and elasticity. Wrapping silk, or aciniform silk, is the toughest of the spider silks, and has a very different protein composition than other spider silks. Here, we present the characterization of an aciniform protein (AcSp1) subunit named W1, consisting of one AcSp1 199 residue repeat unit from Argiope trifasciata. The structural integrity of recombinant W1 is demonstrated in a variety of buffer conditions and time points. Furthermore, we show that W1 has a high thermal stability with reversible denaturation at ∼71°C and forms self-assembled nanoparticle in near-physiological conditions. W1 therefore represents a highly stable and structurally robust module for protein-based nanoparticle formation. Copyright © 2013 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

Dry-Spun Silk Produces Native-Like Fibroin Solutions

PubMed Central

2016-01-01

Silk’s outstanding mechanical properties and energy efficient solidification mechanisms provide inspiration for biomaterial self-assembly as well as offering a diverse platform of materials suitable for many biotechnology applications. Experiments now reveal that the mulberry silkworm Bombyx mori secretes its silk in a practically “unspun” state that retains much of the solvent water and exhibits a surprisingly low degree of molecular order (β-sheet crystallinity) compared to the state found in a fully formed and matured fiber. These new observations challenge the general understanding of silk spinning and in particular the role of the spinning duct for structure development. Building on this discovery we report that silk spun in low humidity appears to arrest a molecular annealing process crucial for β-sheet formation. This, in turn, has significant positive implications, enabling the production of a high fidelity reconstituted silk fibroin with properties akin to the gold standard of unspun native silk. PMID:27526078

A Hox Gene, Antennapedia, Regulates Expression of Multiple Major Silk Protein Genes in the Silkworm Bombyx mori*

PubMed Central

Tsubota, Takuya; Tomita, Shuichiro; Uchino, Keiro; Kimoto, Mai; Takiya, Shigeharu; Kajiwara, Hideyuki; Yamazaki, Toshimasa; Sezutsu, Hideki

2016-01-01

Hox genes play a pivotal role in the determination of anteroposterior axis specificity during bilaterian animal development. They do so by acting as a master control and regulating the expression of genes important for development. Recently, however, we showed that Hox genes can also function in terminally differentiated tissue of the lepidopteran Bombyx mori. In this species, Antennapedia (Antp) regulates expression of sericin-1, a major silk protein gene, in the silk gland. Here, we investigated whether Antp can regulate expression of multiple genes in this tissue. By means of proteomic, RT-PCR, and in situ hybridization analyses, we demonstrate that misexpression of Antp in the posterior silk gland induced ectopic expression of major silk protein genes such as sericin-3, fhxh4, and fhxh5. These genes are normally expressed specifically in the middle silk gland as is Antp. Therefore, the evidence strongly suggests that Antp activates these silk protein genes in the middle silk gland. The putative sericin-1 activator complex (middle silk gland-intermolt-specific complex) can bind to the upstream regions of these genes, suggesting that Antp directly activates their expression. We also found that the pattern of gene expression was well conserved between B. mori and the wild species Bombyx mandarina, indicating that the gene regulation mechanism identified here is an evolutionarily conserved mechanism and not an artifact of the domestication of B. mori. We suggest that Hox genes have a role as a master control in terminally differentiated tissues, possibly acting as a primary regulator for a range of physiological processes. PMID:26814126

Effect of degumming time on silkworm silk fibre for biodegradable polymer composites

NASA Astrophysics Data System (ADS)

Ho, Mei-po; Wang, Hao; Lau, Kin-tak

2012-02-01

Recently, many studies have been conducted on exploitation of natural materials for modern product development and bioengineering applications. Apart from plant-based materials (such as sisal, hemp, jute, bamboo and palm fibre), animal-based fibre is a kind of sustainable natural materials for making novel composites. Silkworm silk fibre extracted from cocoon has been well recognized as a promising material for bio-medical engineering applications because of its superior mechanical and bioresorbable properties. However, when producing silk fibre reinforced biodegradable/bioresorbable polymer composites, hydrophilic sericin has been found to cause poor interfacial bonding with most polymers and thus, it results in affecting the resultant properties of the composites. Besides, sericin layers on fibroin surface may also cause an adverse effect towards biocompatibility and hypersensitivity to silk for implant applications. Therefore, a proper pre-treatment should be done for sericin removal. Degumming is a surface modification process which allows a wide control of the silk fibre's properties, making the silk fibre possible to be used for the development and production of novel bio-composites with unique/specific mechanical and biodegradable properties. In this paper, a cleaner and environmentally friendly surface modification technique for tussah silk in polymer based composites is proposed. The effectiveness of different degumming parameters including degumming time and temperature on tussah silk is discussed through the analyses of their mechanical and morphological properties. Based on results obtained, it was found that the mechanical properties of tussah silk are affected by the degumming time due to the change of the fibre structure and fibroin alignment.

Characterisation of phenol oxidase and peroxidase from maize silk.

PubMed

Sukalović, V Hadzi-Tasković; Veljović-Jovanović, S; Maksimović, J Dragisić; Maksimović, V; Pajić, Z

2010-05-01

Silk of some maize genotypes contains a high level of phenolics that undergo enzymatic oxidation to form quinones, which condense among themselves or with proteins to form brown pigments. Two phenolic oxidizing enzymes, peroxidase (POD; EC 1.11.1.7) and polyphenol oxidase (PPO; EC 1.10.3.1), from maize (Zea mays L.) silk were characterised with respect to their preferred substrate, different isoforms and specific effectors. One browning silk sample with high, and two non-browning samples with low phenolic content were investigated. Although POD oxidizes a wide range of phenolic substrates in vitro, its activity rate was independent of silk phenolic content. PPO activity, detected with o-diphenolic substrates, was abundant only in browning silk, and low or absent in non-browning silk. Pollination increased POD but not PPO activity. Isoelectric-focusing (IEF) and specific staining for POD and PPO showed a high degree of polymorphism that varied with silk origin. The IEF pattern of POD revealed a number of anionic and several cationic isoenzymes, with the most pronounced having neutral pI 7 and a basic isoform with pI 10. Detected isoforms of PPO were anionic, except for one neutral form found only in browning silk, and occupied positions different from those of POD. Different inhibitory effects of NaN(3), EDTA, KCN, and L-cysteine, as well as different impacts of a variety of cations on the oxidation of chlorogenic acid, mediated by PPO or POD, were detected. The findings are discussed in terms of a possible roles of these enzymes in defence and pollination.

The other prey-capture silk: Fibres made by glow-worms (Diptera: Keroplatidae) comprise cross-β-sheet crystallites in an abundant amorphous fraction.

PubMed

Walker, Andrew A; Weisman, Sarah; Trueman, Holly E; Merritt, David J; Sutherland, Tara D

2015-09-01

Glow-worms (larvae of dipteran genus Arachnocampa) are restricted to moist habitats where they capture flying prey using snares composed of highly extensible silk fibres and sticky mucus droplets. Little is known about the composition or structure of glow-worm snares, or the extent of possible convergence between glow-worm and arachnid capture silks. We characterised Arachnocampa richardsae silk and mucus using X-ray scattering, Fourier transform infrared spectroscopy and amino acid analysis. Silk but not mucus contained crystallites of the cross-β-sheet type, which occur in unrelated insect silks but have not been reported previously in fibres used for prey capture. Mucus proteins were rich in Gly (28.5%) and existed in predominantly a random coil structure, typical of many adhesive proteins. In contrast, the silk fibres were unusually rich in charged and polar residues, particularly Lys (18.1%), which we propose is related to their use in a highly hydrated state. Comparison of X-ray scattering, infrared spectroscopy and amino acid analysis data suggests that silk fibres contain a high fraction of disordered protein. We suggest that in the native hydrated state, silk fibres are capable of extension via deformation of both disordered regions and cross-β-sheet crystallites, and that high extensibility is an adaptation promoting successful prey capture. This study illustrates the rich variety of protein motifs that are available for recruitment into biopolymers, and how convergently evolved materials can nevertheless be based on fundamentally different protein structures. Crown Copyright © 2015. Published by Elsevier Inc. All rights reserved.

Nanostructure and molecular mechanics of spider dragline silk protein assemblies

PubMed Central

Keten, Sinan; Buehler, Markus J.

2010-01-01

Spider silk is a self-assembling biopolymer that outperforms most known materials in terms of its mechanical performance, despite its underlying weak chemical bonding based on H-bonds. While experimental studies have shown that the molecular structure of silk proteins has a direct influence on the stiffness, toughness and failure strength of silk, no molecular-level analysis of the nanostructure and associated mechanical properties of silk assemblies have been reported. Here, we report atomic-level structures of MaSp1 and MaSp2 proteins from the Nephila clavipes spider dragline silk sequence, obtained using replica exchange molecular dynamics, and subject these structures to mechanical loading for a detailed nanomechanical analysis. The structural analysis reveals that poly-alanine regions in silk predominantly form distinct and orderly beta-sheet crystal domains, while disorderly regions are formed by glycine-rich repeats that consist of 31-helix type structures and beta-turns. Our structural predictions are validated against experimental data based on dihedral angle pair calculations presented in Ramachandran plots, alpha-carbon atomic distances, as well as secondary structure content. Mechanical shearing simulations on selected structures illustrate that the nanoscale behaviour of silk protein assemblies is controlled by the distinctly different secondary structure content and hydrogen bonding in the crystalline and semi-amorphous regions. Both structural and mechanical characterization results show excellent agreement with available experimental evidence. Our findings set the stage for extensive atomistic investigations of silk, which may contribute towards an improved understanding of the source of the strength and toughness of this biological superfibre. PMID:20519206

Nanostructure and molecular mechanics of spider dragline silk protein assemblies.

PubMed

Keten, Sinan; Buehler, Markus J

2010-12-06

Spider silk is a self-assembling biopolymer that outperforms most known materials in terms of its mechanical performance, despite its underlying weak chemical bonding based on H-bonds. While experimental studies have shown that the molecular structure of silk proteins has a direct influence on the stiffness, toughness and failure strength of silk, no molecular-level analysis of the nanostructure and associated mechanical properties of silk assemblies have been reported. Here, we report atomic-level structures of MaSp1 and MaSp2 proteins from the Nephila clavipes spider dragline silk sequence, obtained using replica exchange molecular dynamics, and subject these structures to mechanical loading for a detailed nanomechanical analysis. The structural analysis reveals that poly-alanine regions in silk predominantly form distinct and orderly beta-sheet crystal domains, while disorderly regions are formed by glycine-rich repeats that consist of 3₁-helix type structures and beta-turns. Our structural predictions are validated against experimental data based on dihedral angle pair calculations presented in Ramachandran plots, alpha-carbon atomic distances, as well as secondary structure content. Mechanical shearing simulations on selected structures illustrate that the nanoscale behaviour of silk protein assemblies is controlled by the distinctly different secondary structure content and hydrogen bonding in the crystalline and semi-amorphous regions. Both structural and mechanical characterization results show excellent agreement with available experimental evidence. Our findings set the stage for extensive atomistic investigations of silk, which may contribute towards an improved understanding of the source of the strength and toughness of this biological superfibre.

Spider silk as a novel high performance biomimetic muscle driven by humidity.

PubMed

Agnarsson, Ingi; Dhinojwala, Ali; Sahni, Vasav; Blackledge, Todd A

2009-07-01

The abrupt halt of a bumble bee's flight when it impacts the almost invisible threads of an orb web provides an elegant example of the amazing strength and toughness of spider silk. Spiders depend upon these properties for survival, yet the impressive performance of silk is not limited solely to tensile mechanics. Here, we show that silk also exhibits powerful cyclic contractions, allowing it to act as a high performance mimic of biological muscles. These contractions are actuated by changes in humidity alone and repeatedly generate work 50 times greater than the equivalent mass of human muscle. Although we demonstrate that this response is general and occurs weakly in diverse hydrophilic materials, the high modulus of spider silk is such that it generates exceptional force. Furthermore, because this effect already operates at the level of single silk fibers, only 5 microm in diameter, it can easily be scaled across the entire size range at which biological muscles operate. By contrast, the most successful synthetic muscles developed so far are driven by electric voltage, such that they cannot scale easily across large ranges in cross-sectional areas. The potential applicability of silk muscles is further enhanced by our finding that silkworm fibers also exhibit cyclic contraction because they are already available in commercial quantities. The simplicity of using wet or dry air to drive the biomimetic silk muscle fibers and the incredible power generated by silk offer unique possibilities in designing lightweight and compact actuators for robots and micro-machines, new sensors, and green energy production.

Conserved C-Terminal Domain of Spider Tubuliform Spidroin 1 Contributes to Extensibility in Synthetic Fibers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gnesa, Eric; Hsia, Yang; Yarger, Jeffery L.

2012-05-24

Spider silk is renowned for its extraordinary mechanical properties, having a balance of high tensile strength and extensibility. To date, the majority of studies have focused on the production of dragline silks from synthetic spider silk gene products. Here we report the first mechanical analysis of synthetic egg case silk fibers spun from the Latrodectus hesperus tubuliform silk proteins, TuSp1 and ECP-2. We provide evidence that recombinant ECP-2 proteins can be spun into fibers that display mechanical properties similar to other synthetic spider silks. We also demonstrate that silks spun from recombinant thioredoxin-TuSp1 fusion proteins that contain the conserved C-terminalmore » domain exhibit increased extensibility and toughness when compared to the identical fibers spun from fusion proteins lacking the C-terminus. Mechanical analyses reveal that the properties of synthetic tubuliform silks can be modulated by altering the postspin draw ratios of the fibers. Fibers subject to increased draw ratios showed elevated tensile strength and decreased extensibility but maintained constant toughness. Wide-angle X-ray diffraction studies indicate that postdrawn fibers containing the C-terminal domain of TuSp1 have more amorphous content when compared to fibers lacking the C-terminus. Taken together, these studies demonstrate that recombinant tubuliform spidroins that contain the conserved C-terminal domain with embedded protein tags can be effectively spun into fibers, resulting in similar tensile strength but increased extensibility relative to nontagged recombinant dragline silk proteins spun from equivalently sized proteins.« less

Silk-fibrin/hyaluronic acid composite gels for nucleus pulposus tissue regeneration.

PubMed

Park, Sang-Hyug; Cho, Hongsik; Gil, Eun Seok; Mandal, Biman B; Min, Byoung-Hyun; Kaplan, David L

2011-12-01

Scaffold designs are critical for in vitro culture of tissue-engineered cartilage in three-dimensional environments to enhance cellular differentiation for tissue engineering and regenerative medicine. In the present study we demonstrated silk and fibrin/hyaluronic acid (HA) composite gels as scaffolds for nucleus pulposus (NP) cartilage formation, providing both biochemical support for NP outcomes as well as fostering the retention of size of the scaffold during culture due to the combined features of the two proteins. Passage two (P2) human chondrocytes cultured in 10% serum were encapsulated within silk-fibrin/HA gels. Five study groups with fibrin/HA gel culture (F/H) along with varying silk concentrations (2% silk gel only, fibrin/HA gel culture with 1% silk [F/H+1S], 1.5% silk [F/H+1.5S], and 2% silk [F/H+2S]) were cultured in serum-free chondrogenic defined media (CDM) for 4 weeks. Histological examination with alcian blue showed a defined chondrogenic area at 1 week in all groups that widened homogenously until 4 weeks. In particular, chondrogenic differentiation observed in the F/H+1.5S had no reduction in size throughout the culture period. The results of biochemical and molecular biological evaluations supported observations made during histological examination. Mechanical strength measurements showed that the silk mixed gels provided stronger mechanical properties for NP tissue than fibrin/HA composite gels in CDM. This effect could potentially be useful in the study of in vitro NP tissue engineering as well as for clinical implications for NP tissue regeneration.

Silk-Fibrin/Hyaluronic Acid Composite Gels for Nucleus Pulposus Tissue Regeneration

PubMed Central

Park, Sang-Hyug; Cho, Hongsik; Gil, Eun Seok; Mandal, Biman B.; Min, Byoung-Hyun

2011-01-01

Scaffold designs are critical for in vitro culture of tissue-engineered cartilage in three-dimensional environments to enhance cellular differentiation for tissue engineering and regenerative medicine. In the present study we demonstrated silk and fibrin/hyaluronic acid (HA) composite gels as scaffolds for nucleus pulposus (NP) cartilage formation, providing both biochemical support for NP outcomes as well as fostering the retention of size of the scaffold during culture due to the combined features of the two proteins. Passage two (P2) human chondrocytes cultured in 10% serum were encapsulated within silk-fibrin/HA gels. Five study groups with fibrin/HA gel culture (F/H) along with varying silk concentrations (2% silk gel only, fibrin/HA gel culture with 1% silk [F/H+1S], 1.5% silk [F/H+1.5S], and 2% silk [F/H+2S]) were cultured in serum-free chondrogenic defined media (CDM) for 4 weeks. Histological examination with alcian blue showed a defined chondrogenic area at 1 week in all groups that widened homogenously until 4 weeks. In particular, chondrogenic differentiation observed in the F/H+1.5S had no reduction in size throughout the culture period. The results of biochemical and molecular biological evaluations supported observations made during histological examination. Mechanical strength measurements showed that the silk mixed gels provided stronger mechanical properties for NP tissue than fibrin/HA composite gels in CDM. This effect could potentially be useful in the study of in vitro NP tissue engineering as well as for clinical implications for NP tissue regeneration. PMID:21736446

Biosynthesis of insulin-silk fibroin nanoparticles conjugates and in vitro evaluation of a drug delivery system

NASA Astrophysics Data System (ADS)

Yan, Hai-Bo; Zhang, Yu-Qing; Ma, Yong-Lei; Zhou, Li-Xia

2009-11-01

Silk fibroin derived from Bombyx mori is a biomacromolecular protein with outstanding biocompatibility. When it was dissolved in highly concentrated CaCl2 solution and then the mixture of the protein and salt was subjected to desalting treatments for long time in flowing water, the resulting liquid silk was water-soluble polypeptides with different molecular masses, ranging from 8 to 70 kDa. When the liquid silk was introduced rapidly into acetone, silk protein nanoparticles with a range of 40-120 nm in diameter could be obtained. The crystalline silk nanoparticles could be conjugated covalently with insulin alone with cross-linking reagent glutaraldehyde. In vitro properties of the insulin-silk fibroin nanoparticles (Ins-SFN) bioconjugates were determined by Enzyme-Linked Immunosorbent Assay (ELISA). The optimal conditions for the biosynthesis of Ins-SFN bioconjugates were investigated. The Ins-SFN constructs obtained by 8 h of covalent cross-linking with 0.7% cross-linking reagent and the proportion of insulin and SFN being 30 IU: 15 mg showed much higher recoveries (90-115%). When insulin was coupled covalently with silk nanoparticles, the resistance of the modified insulin to trypsin digestion and in vitro stability in human serum were greatly enhanced as compared with insulin alone. The results in human serum indicated that the half-life in vitro of the biosynthesized Ins-SFN derivatives was about 2.5 times more than that of native insulin. Therefore, the silk protein nanoparticles have the potential values for being studied and developed as a new bioconjugate for enzyme/polypeptide drug delivery system.

A Hox Gene, Antennapedia, Regulates Expression of Multiple Major Silk Protein Genes in the Silkworm Bombyx mori.

PubMed

Tsubota, Takuya; Tomita, Shuichiro; Uchino, Keiro; Kimoto, Mai; Takiya, Shigeharu; Kajiwara, Hideyuki; Yamazaki, Toshimasa; Sezutsu, Hideki

2016-03-25

Hoxgenes play a pivotal role in the determination of anteroposterior axis specificity during bilaterian animal development. They do so by acting as a master control and regulating the expression of genes important for development. Recently, however, we showed that Hoxgenes can also function in terminally differentiated tissue of the lepidopteranBombyx mori In this species,Antennapedia(Antp) regulates expression of sericin-1, a major silk protein gene, in the silk gland. Here, we investigated whether Antpcan regulate expression of multiple genes in this tissue. By means of proteomic, RT-PCR, and in situ hybridization analyses, we demonstrate that misexpression of Antpin the posterior silk gland induced ectopic expression of major silk protein genes such assericin-3,fhxh4, and fhxh5 These genes are normally expressed specifically in the middle silk gland as is Antp Therefore, the evidence strongly suggests that Antpactivates these silk protein genes in the middle silk gland. The putativesericin-1 activator complex (middle silk gland-intermolt-specific complex) can bind to the upstream regions of these genes, suggesting that Antpdirectly activates their expression. We also found that the pattern of gene expression was well conserved between B. moriand the wild species Bombyx mandarina, indicating that the gene regulation mechanism identified here is an evolutionarily conserved mechanism and not an artifact of the domestication of B. mori We suggest that Hoxgenes have a role as a master control in terminally differentiated tissues, possibly acting as a primary regulator for a range of physiological processes. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Bundles of Spider Silk, Braided into Sutures, Resist Basic Cyclic Tests: Potential Use for Flexor Tendon Repair

PubMed Central

Hennecke, Kathleen; Redeker, Joern; Kuhbier, Joern W.; Strauss, Sarah; Allmeling, Christina; Kasper, Cornelia; Reimers, Kerstin; Vogt, Peter M.

2013-01-01

Repair success for injuries to the flexor tendon in the hand is often limited by the in vivo behaviour of the suture used for repair. Common problems associated with the choice of suture material include increased risk of infection, foreign body reactions, and inappropriate mechanical responses, particularly decreases in mechanical properties over time. Improved suture materials are therefore needed. As high-performance materials with excellent tensile strength, spider silk fibres are an extremely promising candidate for use in surgical sutures. However, the mechanical behaviour of sutures comprised of individual silk fibres braided together has not been thoroughly investigated. In the present study, we characterise the maximum tensile strength, stress, strain, elastic modulus, and fatigue response of silk sutures produced using different braiding methods to investigate the influence of braiding on the tensile properties of the sutures. The mechanical properties of conventional surgical sutures are also characterised to assess whether silk offers any advantages over conventional suture materials. The results demonstrate that braiding single spider silk fibres together produces strong sutures with excellent fatigue behaviour; the braided silk sutures exhibited tensile strengths comparable to those of conventional sutures and no loss of strength over 1000 fatigue cycles. In addition, the braiding technique had a significant influence on the tensile properties of the braided silk sutures. These results suggest that braided spider silk could be suitable for use as sutures in flexor tendon repair, providing similar tensile behaviour and improved fatigue properties compared with conventional suture materials. PMID:23613793

Nuclear Magnetic Resonance (NMR) Spectroscopic Characterization of Nanomaterials and Biopolymers

NASA Astrophysics Data System (ADS)

Guo, Chengchen

Nanomaterials have attracted considerable attention in recent research due to their wide applications in various fields such as material science, physical science, electrical engineering, and biomedical engineering. Researchers have developed many methods for synthesizing different types of nanostructures and have further applied them in various applications. However, in many cases, a molecular level understanding of nanoparticles and their associated surface chemistry is lacking investigation. Understanding the surface chemistry of nanomaterials is of great significance for obtaining a better understanding of the properties and functions of the nanomaterials. Nuclear magnetic resonance (NMR) spectroscopy can provide a familiar means of looking at the molecular structure of molecules bound to surfaces of nanomaterials as well as a method to determine the size of nanoparticles in solution. Here, a combination of NMR spectroscopic techniques including one- and two-dimensional NMR spectroscopies was used to investigate the surface chemistry and physical properties of some common nanomaterials, including for example, thiol-protected gold nanostructures and biomolecule-capped silica nanoparticles. Silk is a natural protein fiber that features unique properties such as excellent mechanical properties, biocompatibility, and non-linear optical properties. These appealing physical properties originate from the silk structure, and therefore, the structural analysis of silk is of great importance for revealing the mystery of these impressive properties and developing novel silk-based biomaterials as well. Here, solid-state NMR spectroscopy was used to elucidate the secondary structure of silk proteins in N. clavipes spider dragline silk and B. mori silkworm silk. It is found that the Gly-Gly-X (X=Leu, Tyr, Gln) motif in spider dragline silk is not in a beta-sheet or alpha-helix structure and is very likely to be present in a disordered structure with evidence for 31-helix confirmation. In addition, the conformations of the Ala, Ser, and Tyr residues in silk fibroin of B. mori were investigated and it indicates that the Ala, Ser, and Tyr residues are all present in disordered structures in silk I (before spinning), while show different conformations in silk II (after spinning). Specifically, in silk II, the Ala and Tyr residues are present in both disordered structures and beta-sheet structures, and the Ser residues are present primarily in beta-sheet structures.

Dating silk by capillary electrophoresis mass spectrometry.

PubMed

Moini, Mehdi; Klauenberg, Kathryn; Ballard, Mary

2011-10-01

A new capillary electrophoresis mass spectrometry (CE-MS) technique is introduced for age estimation of silk textiles based on amino acid racemization rates. With an L to D conversion half-life of ~2500 years for silk (B. mori) aspartic acid, the technique is capable of dating silk textiles ranging in age from several decades to a few-thousand-years-old. Analysis required only ~100 μg or less of silk fiber. Except for a 2 h acid hydrolysis at 110 °C, no other sample preparation is required. The CE-MS analysis takes ~20 min, consumes only nanoliters of the amino acid mixture, and provides both amino acid composition profiles and D/L ratios for ~11 amino acids.

Thin Film Assembly of Spider Silk-like Block Copolymers

DTIC Science & Technology

2011-01-01

Shipley, N. H.; Lewis, R. V. Int. J. Biol.Macromol. 1999, 24, 271. (c) Thiel, B. L.; Guess, K. B.; Viney, C. Biopolymers 1997, 41, 703. (13) Silk ...Film Assembly of Spider Silk -like Block Copolymers Sreevidhya T. Krishnaji,†,‡ Wenwen Huang,§ Olena Rabotyagova,†,‡ Eugenia Kharlampieva, ) Ikjun Choi...Received November 26, 2010 We report the self-assembly of monolayers of spider silk -like block copolymers. Langmuir isotherms were obtained for a series of

Mechanical properties of silk: interplay of deformation on macroscopic and molecular length scales.

PubMed

Krasnov, Igor; Diddens, Imke; Hauptmann, Nadine; Helms, Gesa; Ogurreck, Malte; Seydel, Tilo; Funari, Sérgio S; Müller, Martin

2008-02-01

Using an in situ combination of tensile tests and x-ray diffraction, we have determined the mechanical properties of both the crystalline and the disordered phase of the biological nanocomposite silk by adapting a model from linear viscoelastic theory to the semicrystalline morphology of silk. We observe a strong interplay between morphology and mechanical properties. Silk's high extensibility results principally from the disordered phase; however, the crystals are also elastically deformed.

Silk-Quality, Spinnability and Low Temperature Behavior

DTIC Science & Technology

2015-12-02

dry  silk  radial  and   web  frame  threads.    In   this  study  we  experimentally  demonstrated...green  dashed  line),   nylon  (orange),  Nephila  major  ampullate  spider  silk  ( dry :  black,  wet:  cyan).  Asterisk...gives  low  tension,   dry   Aciniform  spider  silk.  [  33  ]  For  the  major

Preventing Vision Loss from Blast Injuries with Regenerative Biomaterial

DTIC Science & Technology

2012-12-01

the silk material was placed intrastromally within the rabbit cornea model. To do this, silk fibroin films that measured 6-mm in diameter and 3-µms...to the corneal surface after 10-minutes post application. (H) Insoluble portions of the silk bandage were measured at 45-minutes showing the... measuring 14-mm in diameter and 50-µm in thickness were cast using the same batch of silk solution as the bandages from the previous residence time studies

Rheology of Self-Assembling Silk Fibroin Solutions

NASA Astrophysics Data System (ADS)

Zhou, Rui; Chen, Song-Bi; Yuan, Xue-Feng

2008-07-01

A robust procedure for preparation of aqueous silk fibroin solutions with a range of concentration up to 25 wt% from domestic Bombyx mori cocoon shells has been established. We have carried out molecular and rheometric characterizations of silk fibroin solutions, and constructed an equilibrium phase diagram. The sharp sol-gel transition can be exploited for rapid solidification of micro-morphological structure. We will discuss the correlations between fluid formulation, rheological properties and processibility of silk fibroin in the talk.

Mechanical response of silk crystalline units from force-distribution analysis.

PubMed

Xiao, Senbo; Stacklies, Wolfram; Cetinkaya, Murat; Markert, Bernd; Gräter, Frauke

2009-05-20

The outstanding mechanical toughness of silk fibers is thought to be caused by embedded crystalline units acting as cross links of silk proteins in the fiber. Here, we examine the robustness of these highly ordered beta-sheet structures by molecular dynamics simulations and finite element analysis. Structural parameters and stress-strain relationships of four different models, from spider and Bombyx mori silk peptides, in antiparallel and parallel arrangement, were determined and found to be in good agreement with x-ray diffraction data. Rupture forces exceed those of any previously examined globular protein many times over, with spider silk (poly-alanine) slightly outperforming Bombyx mori silk ((Gly-Ala)(n)). All-atom force distribution analysis reveals both intrasheet hydrogen-bonding and intersheet side-chain interactions to contribute to stability to similar extent. In combination with finite element analysis of simplified beta-sheet skeletons, we could ascribe the distinct force distribution pattern of the antiparallel and parallel silk crystalline units to the difference in hydrogen-bond geometry, featuring an in-line or zigzag arrangement, respectively. Hydrogen-bond strength was higher in antiparallel models, and ultimately resulted in higher stiffness of the crystal, compensating the effect of the mechanically disadvantageous in-line hydrogen-bond geometry. Atomistic and coarse-grained force distribution patterns can thus explain differences in mechanical response of silk crystals, opening up the road to predict full fiber mechanics.

Fabrication and Characterization of Conductive Conjugated Polymer-Coated Antheraea mylitta Silk Fibroin Fibers for Biomedical Applications.

PubMed

Gh, Darshan; Kong, Dexu; Gautrot, Julien; Vootla, Shyam Kumar

2017-07-01

Conductive polymers are interesting materials for a number of biological and medical applications requiring electrical stimulation of cells or tissues. Highly conductive polymers (polypyrrole and polyaniline)/Antheraea mylitta silk fibroin coated fibers are fabricated successfully by in situ polymerization without any modification of the native silk fibroin. Coated fibers characterized by scanning electron microscopy confirm the silk fiber surface is covered by conductive polymers. Thermogravimetric analysis reveals preserved thermal stability of silk fiber after coating process. X-ray diffraction of degummed fiber diffraction peaks at around 2θ = 20.4 and 16.5 confirms the preservation of the β-sheet structure typical of degummed silk II fibers. This phenomenon implies that both polypyrrole and polyaniline chains form interactions with peptide linkages in degummed fiber macromolecules, without significantly disrupting protein assembly. Fourier transform infrared spectroscopy of coated fibers indicates hydrogen bonding and electrostatic interactions exist between silk fibroin macromolecules and conductive polymers. Resulting fibers display good conductive properties compared to corresponding conjugated polymers. In vitro analysis (live/dead assay) of the behavior of human immortalized keratinocytes (HaCaTs) on coated fibers demonstrates improved cell-adhesive properties and viability after polymers coating. Hence, polypyrrole- and polyaniline-coated A. mylitta silk fibers are suitable for application in cell culture and for tissue engineering, where electrical conduction properties are required. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Strength of silk attachment to Ilex chinensis leaves in the tea bagworm Eumeta minuscula (Lepidoptera, Psychidae).

PubMed

Wolff, Jonas O; Lovtsova, Julia; Gorb, Elena; Dai, Zhendong; Ji, Aihong; Zhao, Zhihui; Jiang, Nan; Gorb, Stanislav N

2017-03-01

Silks play an important role in the life of various arthropods. A highly neglected prerequisite to make versatile use of silks is sufficient attachment to substrates. Although there have been some studies on the structure and mechanics of silk anchorages of spiders, for insects only anecdotal reports on attachment-associated spinning behaviour exist. Here, we experimentally studied the silk attachment of the pupae and last instar caterpillars of the tea bagworm Eumeta minuscula (Butler 1881) (Lepidoptera, Psychidae) to the leaves of its host plant Ilex chinensis We found that the bagworms spin attachment discs, which share some structural features with those of spiders, like a plaque consisting of numerous overlaid, looped glue-coated silk fibres and the medially attaching suspension thread. Although the glue, which coats the fibres, cannot spread and adhere very well to the leaf surface, high pull-off forces were measured, yielding a mean safety factor (force divided by the animal weight) of 385.6. Presumably, the bagworms achieve this by removal of the leaf epidermis prior to silk attachment, which exposes the underlying tissue that represents a much better bonding site. This ensures a reliable attachment during the immobile, vulnerable pupal stage. This is the first study on the biomechanics and structure of silk attachments to substrates in insects. © 2017 The Author(s).

Sequence Identification, Recombinant Production, and Analysis of the Self-Assembly of Egg Stalk Silk Proteins from Lacewing Chrysoperla carnea.

PubMed

Neuenfeldt, Martin; Scheibel, Thomas

2017-06-13

Egg stalk silks of the common green lacewing Chrysoperla carnea likely comprise at least three different silk proteins. Based on the natural spinning process, it was hypothesized that these proteins self-assemble without shear stress, as adult lacewings do not use a spinneret. To examine this, the first sequence identification and determination of the gene expression profile of several silk proteins and various transcript variants thereof was conducted, and then the three major proteins were recombinantly produced in Escherichia coli encoded by their native complementary DNA (cDNA) sequences. Circular dichroism measurements indicated that the silk proteins in aqueous solutions had a mainly intrinsically disordered structure. The largest silk protein, which we named ChryC1, exhibited a lower critical solution temperature (LCST) behavior and self-assembled into fibers or film morphologies, depending on the conditions used. The second silk protein, ChryC2, self-assembled into nanofibrils and subsequently formed hydrogels. Circular dichroism and Fourier transform infrared spectroscopy confirmed conformational changes of both proteins into beta sheet rich structures upon assembly. ChryC3 did not self-assemble into any morphology under the tested conditions. Thereby, through this work, it could be shown that recombinant lacewing silk proteins can be produced and further used for studying the fiber formation of lacewing egg stalks.

Invited review nonmulberry silk biopolymers.

PubMed

Kundu, S C; Kundu, Banani; Talukdar, Sarmistha; Bano, Subia; Nayak, Sunita; Kundu, Joydip; Mandal, Biman B; Bhardwaj, Nandana; Botlagunta, Mahendran; Dash, Biraja C; Acharya, Chitrangada; Ghosh, Ananta K

2012-06-01

The silk produced by silkworms are biopolymers and can be classified into two types--mulberry and nonmulberry. Mulberry silk of silkworm Bombyx mori has been extensively explored and used for century old textiles and sutures. But for the last few decades it is being extensively exploited for biomedical applications. However, the transformation of nonmulberry silk from being a textile commodity to biomaterials is relatively new. Within a very short period of time, the combination of load bearing capability and tensile strength of nonmulberry silk has been equally envisioned for bone, cartilage, adipose, and other tissue regeneration. Adding to its advantage is its diverse morphology, including macro to nano architectures with controllable degradation and biocompatibility yields novel natural material systems in vitro. Its follow on applications involve sustained release of model compounds and anticancer drugs. Its 3D cancer models provide compatible microenvironment systems for better understanding of the cancer progression mechanism and screening of anticancer compounds. Diversely designed nonmulberry matrices thus provide an array of new cutting age technologies, which is unattainable with the current synthetic materials that lack biodegradability and biocompatibility. Scientific exploration of nonmulberry silk in tissue engineering, regenerative medicine, and biotechnological applications promises advancement of sericulture industries in India and China, largest nonmulberry silk producers of the world. This review discusses the prospective biomedical applications of nonmulberry silk proteins as natural biomaterials. Copyright © 2012 Wiley Periodicals, Inc.

Dissecting the structural determinants for the difference in mechanical stability of silk and amyloid beta-sheet stacks.

PubMed

Xiao, Senbo; Xiao, Shijun; Gräter, Frauke

2013-06-14

Stacking of β-sheets results in a protein super secondary structure with remarkable mechanical properties. β-Stacks are the determinants of a silk fiber's resilience and are also the building blocks of amyloid fibrils. While both silk and amyloid-type crystals are known to feature a high resistance against rupture, their structural and mechanical similarities and particularities are yet to be fully understood. Here, we systematically compare the rupture force and stiffness of amyloid and spider silk poly-alanine β-stacks of comparable sizes using Molecular Dynamics simulations. We identify the direction of force application as the primary determinant of the rupture strength; β-sheets in silk are orientated along the fiber axis, i.e. the pulling direction, and consequently require high forces in the several nanoNewton range for shearing β-strands apart, while β-sheets in amyloid are oriented vertically to the fiber, allowing a zipper-like rupture at sub-nanoNewton forces. A secondary factor rendering amyloid β-stacks softer and weaker than their spider silk counterparts is the sub-optimal side-chain packing between β-sheets due to the sequence variations of amyloid-forming proteins as opposed to the perfectly packed poly-alanine β-sheets of silk. Taken together, amyloid fibers can reach the stiffness of silk fibers in spite of their softer and weaker β-sheet arrangement as they are missing a softening amorphous matrix.

Impact of processing parameters on the haemocompatibility of Bombyx mori silk films.

PubMed

Seib, F Philipp; Maitz, Manfred F; Hu, Xiao; Werner, Carsten; Kaplan, David L

2012-02-01

Silk has traditionally been used for surgical sutures due to its lasting strength and durability; however, the use of purified silk proteins as a scaffold material for vascular tissue engineering goes beyond traditional use and requires application-orientated biocompatibility testing. For this study, a library of Bombyx mori silk films was generated and exposed to various solvents and treatment conditions to reflect current silk processing techniques. The films, along with clinically relevant reference materials, were exposed to human whole blood to determine silk blood compatibility. All substrates showed an initial inflammatory response comparable to polylactide-co-glycolide (PLGA), and a low to moderate haemostasis response similar to polytetrafluoroethylene (PTFE) substrates. In particular, samples that were water annealed at 25 °C for 6 h demonstrated the best blood compatibility based on haemostasis parameters (e.g. platelet decay, thrombin-antithrombin complex, platelet factor 4, granulocytes-platelet conjugates) and inflammatory parameters (e.g. C3b, C5a, CD11b, surface-associated leukocytes). Multiple factors such as treatment temperature and solvent influenced the biological response, though no single physical parameter such as β-sheet content, isoelectric point or contact angle accurately predicted blood compatibility. These findings, when combined with prior in vivo data on silk, support a viable future for silk-based vascular grafts. Copyright © 2011 Elsevier Ltd. All rights reserved.

Preparation of new natural silk non-woven fabrics by using adhesion characteristics of sericin and their characterization.

PubMed

Lee, Ji Hye; Bae, Yeon Su; Kim, Su Jin; Song, Dae Woong; Park, Young Hwan; Bae, Do Gyu; Choi, Jin Hyun; Um, In Chul

2018-01-01

Electro-spun regenerated silk webs have been extensively studied for biomedical applications because of the simplicity of their fabrication methods However, the productivity of the electro-spinning process is low for web fabrication and the mechanical properties of the electro-spun silk web are not satisfactory, which restricts its commercialization. In this study, a new silk non-woven fabric was successfully fabricated by wetting and hot press treatments using the excellent binding characteristic of sericin. The effects of the press temperature and residual sericin content on the preparation, structure, and properties of the silk non-woven fabric were examined. A press temperature of 200°C was optimum for obtaining non-woven fabrics with best mechanical properties, without yellowing. The silk non-woven fabric could not be fabricated without sericin, and a minimum of 8% sericin was required to fabricate it. As the sericin content was increased, the strength and Young's modulus of the silk non-woven fabric increased, while the tensile elongation remained constant. Regardless of the press temperature and sericin content, all the silk non-woven fabrics showed good cell viability, comparable to that of the tissue culture plate (TCP) used as a control until 4days, which however decreased compared to that of TCP after 7days. Copyright © 2017 Elsevier B.V. All rights reserved.

Differentiation of human endometrial stem cells into urothelial cells on a three-dimensional nanofibrous silk-collagen scaffold: an autologous cell resource for reconstruction of the urinary bladder wall.

PubMed

Shoae-Hassani, Alireza; Mortazavi-Tabatabaei, Seyed Abdolreza; Sharif, Shiva; Seifalian, Alexander Marcus; Azimi, Alireza; Samadikuchaksaraei, Ali; Verdi, Javad

2015-11-01

Reconstruction of the bladder wall via in vitro differentiated stem cells on an appropriate scaffold could be used in such conditions as cancer and neurogenic urinary bladder. This study aimed to examine the potential of human endometrial stem cells (EnSCs) to form urinary bladder epithelial cells (urothelium) on nanofibrous silk-collagen scaffolds, for construction of the urinary bladder wall. After passage 4, EnSCs were induced by keratinocyte growth factor (KGF) and epidermal growth factor (EGF) and seeded on electrospun collagen-V, silk and silk-collagen nanofibres. Later we tested urothelium-specific genes and proteins (uroplakin-Ia, uroplakin-Ib, uroplakin-II, uroplakin-III and cytokeratin 20) by immunocytochemistry, RT-PCR and western blot analyses. Scanning electron microscopy (SEM) and histology were used to detect cell-matrix interactions. DMEM/F12 supplemented by KGF and EGF induced EnSCs to express urothelial cell-specific genes and proteins. Either collagen, silk or silk-collagen scaffolds promoted cell proliferation. The nanofibrous silk-collagen scaffolds provided a three-dimensional (3D) structure to maximize cell-matrix penetration and increase differentiation of the EnSCs. Human EnSCs seeded on 3D nanofibrous silk-collagen scaffolds and differentiated to urothelial cells provide a suitable source for potential use in bladder wall reconstruction in women. Copyright © 2013 John Wiley & Sons, Ltd.

Rate-Dependent Behavior of the Amorphous Phase of Spider Dragline Silk

PubMed Central

Patil, Sandeep P.; Markert, Bernd; Gräter, Frauke

2014-01-01

The time-dependent stress-strain behavior of spider dragline silk was already observed decades ago, and has been attributed to the disordered sequences in silk proteins, which compose the soft amorphous matrix. However, the actual molecular origin and magnitude of internal friction within the amorphous matrix has remained inaccessible, because experimentally decomposing the mechanical response of the amorphous matrix from the embedded crystalline units is challenging. Here, we used atomistic molecular dynamics simulations to obtain friction forces for the relative sliding of peptide chains of Araneus diadematus spider silk within bundles of these chains as a representative unit of the amorphous matrix in silk fibers. We computed the friction coefficient and coefficient of viscosity of the amorphous phase to be in the order of 10−6 Ns/m and 104 Ns/m2, respectively, by extrapolating our simulation data to the viscous limit. Finally, we used a finite element method for the amorphous phase, solely based on parameters derived from molecular dynamics simulations including the newly determined coefficient of viscosity. With this model the time scales of stress relaxation, creep, and hysteresis were assessed, and found to be in line with the macroscopic time-dependent response of silk fibers. Our results suggest the amorphous phase to be the primary source of viscosity in silk and open up the avenue for finite element method studies of silk fiber mechanics including viscous effects. PMID:24896131

Structural study of Bombyx mori silk fibroin during processing for regeneration

NASA Astrophysics Data System (ADS)

Ha, Sung-Won

Bombyx mori silk fibroin has excellent mechanical properties combined with flexibility, tissue compatibility, and high oxygen permeability in the wet condition. This important material should be dissolved and regenerated to be utilized as useful forms such as gel, film, fiber, powder, or non-woven. However, it has long been a problem that the regenerated fibroin materials show poor mechanical properties and brittleness. These problems were technically solved by improving a fiber processing method reported here. The regenerated fibroin fibers showed much better mechanical properties compared to the original silk fibers. This improved technique for the fiber processing of Bombyx mori silk fibroin may be used as a model system for other semi-crystalline fiber forming proteins, becoming available through biotechnology. The physical and chemical properties of the regenerated fibers were characterized by SinTechRTM tensile testing, X-ray diffraction, solid state 13C NMR spectroscopy, and SEM. Unlike synthetic polymers, the molecular weight distribution of Bombyx mori silk fibroin is mono-disperse because silk fibroin is synthesized from DNA template. Genetic studies have revealed the entire amino acid sequence of Bombyx mori silk fibroin. It is known that the crystalline silk II structure is composed of hexa-amino acid sequences, GAGAGS. However, in the amino acid sequence of Bombyx mori silk fibroin heavy chain, there are present 11 chemically irregular but evolutionarily conserved sequences with about 31 amino acid residues (irregular GT˜GT sequences). The structure and role of these irregular sequences have remained unknown. One of the most frequently appearing irregular sequences was synthesized by a peptide synthesizer. The three-dimensional structure of this irregular silk peptide was studied by the high resolution two-dimensional NMR technique. The three-dimensional structure of this peptide shows that it makes a turn or loop structure (distorted O shape), which means the proceeding backbone direction is changed 180° by this sequence. This may facilitate the beta-sheet formation of the crystal forming building blocks, GAGAGS/GY˜GY sequences, in fibroin heavy chain. It may also facilitate the solubilization of the fibroin heavy chain within the silk gland.

Molecular and macro-scale analysis of enzyme-crosslinked silk hydrogels for rational biomaterial design.

PubMed

McGill, Meghan; Coburn, Jeannine M; Partlow, Benjamin P; Mu, Xuan; Kaplan, David L

2017-11-01

Silk fibroin-based hydrogels have exciting applications in tissue engineering and therapeutic molecule delivery; however, their utility is dependent on their diffusive properties. The present study describes a molecular and macro-scale investigation of enzymatically-crosslinked silk fibroin hydrogels, and demonstrates that these systems have tunable crosslink density and diffusivity. We developed a liquid chromatography tandem mass spectroscopy (LC-MS/MS) method to assess the quantity and order of covalent tyrosine crosslinks in the hydrogels. This analysis revealed between 28 and 56% conversion of tyrosine to dityrosine, which was dependent on the silk concentration and reactant concentration. The crosslink density was then correlated with storage modulus, revealing that both crosslinking and protein concentration influenced the mechanical properties of the hydrogels. The diffusive properties of the bulk material were studied by fluorescence recovery after photobleaching (FRAP), which revealed a non-linear relationship between silk concentration and diffusivity. As a result of this work, a model for synthesizing hydrogels with known crosslink densities and diffusive properties has been established, enabling the rational design of silk hydrogels for biomedical applications. Hydrogels from naturally-derived silk polymers offer versitile opportunities in the biomedical field, however, their design has largely been an empirical process. We present a fundamental study of the crosslink density, storage modulus, and diffusion behavior of enzymatically-crosslinked silk hydrogels to better inform scaffold design. These studies revealed unexpected non-linear trends in the crosslink density and diffusivity of silk hydrogels with respect to protein concentration and crosslink reagent concentration. This work demonstrates the tunable diffusivity and crosslinking in silk fibroin hydrogels, and enables the rational design of biomaterials. Further, the characterization methods presented have applications for other materials with dityrosine crosslinks, which are found in nature as post-translational modificaitons, as well as in engineered matrices such as tyramine-substituted hyaluronic acid and recombinant resilin. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Silk: Optical Properties over 12.6 Octaves THz-IR-Visible-UV Range

PubMed Central

Balčytis, Armandas; Ryu, Meguya; Wang, Xuewen; Novelli, Fabio; Seniutinas, Gediminas; Du, Shan; Wang, Xungai; Li, Jingliang; Davis, Jeffrey; Appadoo, Dominique; Morikawa, Junko; Juodkazis, Saulius

2017-01-01

Domestic (Bombyx mori) and wild (Antheraea pernyi) silk fibers were characterised over a wide spectral range from THz 8 cm−1 (λ= 1.25 mm, f= 0.24 THz) to deep-UV 50×103 cm−1 (λ= 200 nm, f= 1500 THz) wavelengths or over a 12.6 octave frequency range. Spectral features at β-sheet, α-coil and amorphous fibroin were analysed at different spectral ranges. Single fiber cross sections at mid-IR were used to determine spatial distribution of different silk constituents and revealed an α-coil rich core and more broadly spread β-sheets in natural silk fibers obtained from wild Antheraea pernyi moths. Low energy T-ray bands at 243 and 229 cm−1 were observed in crystalline fibers of domestic and wild silk fibers, respectively, and showed no spectral shift down to 78 K temperature. A distinct 20±4 cm−1 band was observed in the crystalline Antheraea pernyi silk fibers. Systematic analysis and assignment of the observed spectral bands is presented. Water solubility and biodegradability of silk, required for bio-medical and sensor applications, are directly inferred from specific spectral bands. PMID:28772716

An optically transparent, flexible, patterned and conductive silk biopolymer film (Conference Presentation)

NASA Astrophysics Data System (ADS)

Umar, Muhammad; Min, Kyungtaek; Kim, Sunghwan

2017-02-01

Transparent, flexible, and conducting films are of great interest for wearable electronics. For better biotic/abiotic interface, the films to integrate the electronics components requires the patterned surface conductors with optical transparency, smoothness, good electrical conductivity, along with the biofriendly traits of films. We focus on silk fibroin, a natural biopolymer extracted from the Bombyx mori cocoons, for this bioelectronics applications. Here we report an optically transparent, flexible, and patterned surface conductor on a silk film by burying a silver nanowires (AgNW) network below the surface of the silk film. The conducting silk film reveals high optical transparency of 80% and the excellent electronic conductivity of 15 Ω/sq, along with smooth surface. The integration of light emitting diode (LED) chip on the patterned electrodes confirms that the current can flow through the transparent and patterned electrodes on the silk film, and this result shows an application for integration of functional electronic/opto-electronic devices. Additionally, we fabricate a transparent and flexible radio frequency (RF) antenna and resistor on a silk film and apply these as a food sensor by monitoring the increasing resistance by the flow of gases from the spoiled food.

Spider Silk Processing for Spidroin Recovery from Crossopriza Lyoni Web

NASA Astrophysics Data System (ADS)

Mohtar, J. A.; Ooi, W. L.; Yusuf, F.

2018-03-01

Spider silk is a potential biomaterial that can be used in various applications for its outstanding physicomechanical properties attributed by the spidroin composition. Efforts for commercializing spider silks have been mainly focused on the characterization of spidroins from the Entelegyne spiders for exceptional fibre construction. Hence, studies on silk proteins from the Haplogyne species remain neglected. The aim of this study is to isolate spidroin from Crossopriza lyoni web. Silk processing involved the pretreatment of fibres for the shell layer removal from the surface. A screening study was conducted to analyze the effect of temperature, incubation time and agitation speed on spidroin extraction using Ajisawa’s reagent by OFAT analysis followed by statistical optimization of the extraction process via RSM for maximal protein recovery. All parameters exerted significant effect on spidroin recovery (p<0.05) in which the maximum protein concentration (451.78 ± 0.110 µg/ml) was obtained at optimal condition of 70°C, 350 rpm and 1.25 hours. The discovery of spidroin from this study provides a basic platform for engineering spider silk to meet the demand for a variety of silk-based products in the near future.

Human stem cell neuronal differentiation on silk-carbon nanotube composite

NASA Astrophysics Data System (ADS)

Chen, Chi-Shuo; Soni, Sushant; Le, Catherine; Biasca, Matthew; Farr, Erik; Chen, Eric Y.-T.; Chin, Wei-Chun

2012-02-01

Human embryonic stem cells [hESCs] are able to differentiate into specific lineages corresponding to regulated spatial and temporal signals. This unique attribute holds great promise for regenerative medicine and cell-based therapy for many human diseases such as spinal cord injury [SCI] and multiple sclerosis [MS]. Carbon nanotubes [CNTs] have been successfully used to promote neuronal differentiation, and silk has been widely applied in tissue engineering. This study aims to build silk-CNT composite scaffolds for improved neuron differentiation efficiency from hESCs. Two neuronal markers (β-III tubulin and nestin) were utilized to determine the hESC neuronal lineage differentiation. In addition, axonal lengths were measured to evaluate the progress of neuronal development. The results demonstrated that cells on silk-CNT scaffolds have a higher β-III tubulin and nestin expression, suggesting augmented neuronal differentiation. In addition, longer axons with higher density were found to associate with silk-CNT scaffolds. Our silk-CNT-based composite scaffolds can promote neuronal differentiation of hESCs. The silk-CNT composite scaffolds developed here can serve as efficient supporting matrices for stem cell-derived neuronal transplants, offering a promising opportunity for nerve repair treatments for SCI and MS patients.

Compliant threads maximize spider silk connection strength and toughness

PubMed Central

Meyer, Avery; Pugno, Nicola M.; Cranford, Steven W.

2014-01-01

Millions of years of evolution have adapted spider webs to achieve a range of functionalities, including the well-known capture of prey, with efficient use of material. One feature that has escaped extensive investigation is the silk-on-silk connection joints within spider webs, particularly from a structural mechanics perspective. We report a joint theoretical and computational analysis of an idealized silk-on-silk fibre junction. By modifying the theory of multiple peeling, we quantitatively compare the performance of the system while systematically increasing the rigidity of the anchor thread, by both scaling the stress–strain response and the introduction of an applied pre-strain. The results of our study indicate that compliance is a virtue—the more extensible the anchorage, the tougher and stronger the connection becomes. In consideration of the theoretical model, in comparison with rigid substrates, a compliant anchorage enormously increases the effective adhesion strength (work required to detach), independent of the adhered thread itself, attributed to a nonlinear alignment between thread and anchor (contact peeling angle). The results can direct novel engineering design principles to achieve possible load transfer from compliant fibre-to-fibre anchorages, be they silk-on-silk or another, as-yet undeveloped, system. PMID:25008083

Fabrication of silk fibroin film using centrifugal casting technique for corneal tissue engineering.

PubMed

Lee, Min Chae; Kim, Dong-Kyu; Lee, Ok Joo; Kim, Jung-Ho; Ju, Hyung Woo; Lee, Jung Min; Moon, Bo Mi; Park, Hyun Jung; Kim, Dong Wook; Kim, Su Hyeon; Park, Chan Hum

2016-04-01

Films prepared from silk fibroin have shown potential as biomaterials in tissue engineering applications for the eye. Here, we present a novel process for fabrication of silk fibroin films for corneal application. In this work, fabrication of silk fibroin films was simply achieved by centrifugal force. In contrast to the conventional dry casting method, we carried out the new process in a centrifuge with a rotating speed of 4000 rpm, where centrifugal force was imposed on an aluminum tube containing silk fibroin solution. In the present study, we also compared the surface roughness, mechanical properties, transparency, and cell proliferation between centrifugal and dry casting method. In terms of surface morphology, films fabricated by the centrifugal casting have less surface roughness than those by the dry casting. For elasticity and transparency, silk fibroin films obtained from the centrifugal casting had favorable results compared with those prepared by dry casting. Furthermore, primary human corneal keratocytes grew better in films prepared by the centrifugal casting. Therefore, our results suggest that this new fabrication process for silk fibroin films offers important potential benefits for corneal tissue regeneration. © 2015 Wiley Periodicals, Inc.

Flexible and wearable electronic silk fabrics for human physiological monitoring

NASA Astrophysics Data System (ADS)

Mao, Cuiping; Zhang, Huihui; Lu, Zhisong

2017-09-01

The development of textile-based devices for human physiological monitoring has attracted tremendous interest in recent years. However, flexible physiological sensing elements based on silk fabrics have not been realized. In this paper, ZnO nanorod arrays are grown in situ on reduced graphene oxide-coated silk fabrics via a facile electro-deposition method for the fabrication of silk-fabric-based mechanical sensing devices. The data show that well-aligned ZnO nanorods with hexagonal wurtzite crystalline structures are synthesized on the conductive silk fabric surface. After magnetron sputtering of gold electrodes, silk-fabric-based devices are produced and applied to detect periodic bending and twisting. Based on the electric signals, the deformation and release processes can be easily differentiated. Human arterial pulse and respiration can also be real-time monitored to calculate the pulse rate and respiration frequency, respectively. Throat vibrations during coughing and singing are detected to demonstrate the voice recognition capability. This work may not only help develop silk-fabric-based mechanical sensing elements for potential applications in clinical diagnosis, daily healthcare monitoring and voice recognition, but also provide a versatile method for fabricating textile-based flexible electronic devices.

New Materials Based on Spider Silk

DTIC Science & Technology

2007-11-06

encoding the honey bee secretion signal was (genetically) fused to the spider silk protein. A respective recombinant virus was used to infect high...2007). Role of individual spider silk domains during assembly. Poster at the conference on "Protein Assembly in Materials, Biology and Medicine

Sequence of Spider Aciniform and Piriform Silks

DTIC Science & Technology

2001-09-19

7/98nd subtan-6/01 4. TITLE AND SUBTITLE Sequence of Spider Aciniform and Piriform Silks 5. FUNDING NUMBERS DAAD19-01-1-0569 6...aciniform glands from Argiope trifasciata were used to construct a cDNA library. The library was probed with various DNA probes based on known spider silk ...sequence in a number of other spider silks . The 5’end of the clone still appears to be repetitive sequence and thus it is unlikely to be a full-length

Understanding the Mechanical Properties and Structure Transition of Antheraea pernyi Silk Fiber Induced by Its Contraction.

PubMed

Wang, Yu; Wen, Jianchuan; Peng, Bo; Hu, Bingwen; Chen, Xin; Shao, Zhengzhong

2018-02-23

Like most major ampullate silks of spider, the length of Antheraea pernyi silkworm silk can shrink to a certain degree when the fiber is in contact with water. However, what happens in terms of molecule chain level and how it correlates to the mechanical properties of the silk during its contraction is not yet fully understood. Here, we investigate the water-induced mechanical property changes as well as the structure transition of two kinds of A. pernyi silk fiber, which are forcibly reeled from two different individuals (silkworm a and silkworm b; the silk fiber from either one represents the lower and upper limit of the distribution of mechanical properties, respectively). The tensile test results present that most of the mechanical parameters except the post-yield modulus and breaking strain for both silk fibers have the same variation trend before and after their water contraction. Synchrotron FTIR and Raman spectra show that the native filament from silkworm a contains more α-helix structures than that in silkworm b filament, and these α-helices are partially converted to β-sheet structures after the contraction of the fibers, while the order of both β-sheet and α-helix slightly increase. On the other side, the content and orientation of both secondary structural components in silkworm b fiber keep unchanged, no matter if it is native or contracted. 13 C CP/MAS NMR results further indicate that the α-helix/random coil to β-sheet conformational transition that occurred in the silk of silkworm a corresponds the Ala residues. Based upon these results, the detailed structure transition models of both as-reeled A. pernyi silk fibers during water contraction are proposed finally to interpret their properties transformation.

Conductive Au nanowires regulated by silk fibroin nanofibers

NASA Astrophysics Data System (ADS)

Dong, Bo-Ju; Lu, Qiang

2014-03-01

Conductive Au-biopolymer composites have promising applications in tissue engineering such as nerve tissue regeneration. In this study, silk fibroin nanofibers were formed in aqueous solution by regulating silk self-assembly process and then used as template for Au nanowire fabrication. We performed the synthesis of Au seeds by repeating the seeding cycles for several times in order to increase the density of Au seeds on the nanofibers. After electroless plating, densely decorated Au seeds grew into irregularly shaped particles following silk nanofiber to fill the gaps between particles and finally form uniform continuous nanowires. The conductive property of the Au-silk fibroin nanowires was studied with current-voltage ( I-V) measurement. A typical ohmic behavior was observed, which highlighted their potential applications in nerve tissue regeneration.

Synthetic Adhesive Attachment Discs based on Spider Pyriform Silk Architecture

NASA Astrophysics Data System (ADS)

Jain, Dharamdeep; Sahni, Vasav; Dhinojwala, Ali

2014-03-01

Among the variety of silks produced by spiders, pyriform silk is used in conjunction with the dragline silk to attach webs to different surfaces. Cob weaver spiders employ different architectural patterns to utilize the pyriform silk and form attachment joints with each pattern having a characteristic adhesive performance. The staple pin architecture is a one of the strongest attachment designs employed by spiders to attach their webs. Here we use a synthetic approach to create the a similar patterned architecture attachment discs on aluminum substrate using thermoplastic polyurethane. Measurable pull off forces are generated when the synthetic discs are peeled off a surface. This innovative adhesive strategy can be a source of design in various biomedical applications. Financial Support from National Science Foundation.

Electrodeposited gels prepared from protein alloys

PubMed Central

Lin, Yinan; Wang, Siran; Chen, Ying; Wang, Qianrui; Burke, Kelly A; Spedden, Elise M; Staii, Cristian; Weiss, Anthony S; Kaplan, David L

2015-01-01

Aim Silk-tropoelastin alloys, composed of recombinant human tropoelastin and regenerated Bombyx mori silk fibroin, are an emerging, versatile class of biomaterials endowed with tunable combinations of physical and biological properties. Electrodeposition of these alloys provides a programmable means to assemble functional gels with both spatial and temporal controllability. Materials & methods Tropoelastin-modified silk was prepared by enzymatic coupling between tyrosine residues. Hydrogel coatings were electrodeposited using two wire electrodes. Results & discussion Mechanical characterization and in vitro cell culture revealed enhanced adhesive capability and cellular response of these alloy gels as compared with electrogelled silk alone. Conclusion These electro-depositable silk-tropoelastin alloys constitute a suitable coating material for nanoparticle-based drug carriers and offer a novel opportunity for on-demand encapsulation/release of nanomedicine. PMID:25816881

Materials Fabrication from Bombyx mori Silk Fibroin

PubMed Central

Rockwood, Danielle N.; Preda, Rucsanda C.; Yücel, Tuna; Wang, Xiaoqin; Lovett, Michael L.; Kaplan, David L.

2013-01-01

Silk fibroin, derived from Bombyx mori cocoons, is a widely used and studied protein polymer for biomaterial applications. Silk fibroin has remarkable mechanical properties when formed into different materials, demonstrates biocompatibility, has controllable degradation rates from hours to years, and it can be chemically modified to alter surface properties or to immobilize growth factors. A variety of aqueous or organic solvent processing methods can be used to generate silk biomaterials for a range of applications. In this protocol we include methods to extract silk from B. mori cocoons in order to fabricate hydrogels, tubes, sponges, composites, fibers, microspheres and thin films. These materials can be used directly as biomaterials for implants, as scaffolding in tissue engineering and in vitro disease models, and for drug delivery. PMID:21959241

Robust composite silk fibers pulled out of silkworms directly fed with nanoparticles.

PubMed

Wu, GuoHua; Song, Peng; Zhang, DongYang; Liu, ZeYu; Li, Long; Huang, HuiMing; Zhao, HongPing; Wang, NanNan; Zhu, YanQiu

2017-11-01

This paper reports the impacts of direct feeding silkworms with different nanoparticles (Cu, Fe, and TiO 2 ) on the morphology, structures, and mechanical properties of the resulting silk fiber (SF). The contents of the Cu nanoparticles were 38 times higher in the posterior silk glands and only 2-3 times higher in the SF and in the middle silk glands compared with the controlled groups. Significant changes of the surface morphology, structures, and diameter of the Cu nanoparticle fed SF have been observed, which are attributed to a slight SF protein reconstruction or conformational change in the mixture of silk fibroin and sericin in the silk glands. The resulting Cu-containing SF exhibits good tensile strength of 360MPa and reaches a strain of 38%, which are 89% and 36% higher than those of the natural SF. This study offers a new green strategy for the easy modification to achieve robust composite SF. Copyright © 2017 Elsevier B.V. All rights reserved.

Self-assembly of nucleic acids, silk and hybrid materials thereof.

PubMed

Humenik, Martin; Scheibel, Thomas

2014-12-17

Top-down approaches based on etching techniques have almost reached their limits in terms of dimension. Therefore, novel assembly strategies and types of nanomaterials are required to allow technological advances. Self-assembly processes independent of external energy sources and unlimited in dimensional scaling have become a very promising approach. Here,we highlight recent developments in self-assembled DNA-polymer, silk-polymer and silk-DNA hybrids as promising materials with biotic and abiotic moieties for constructing complex hierarchical materials in ‘bottom-up’ approaches. DNA block copolymers assemble into nanostructures typically exposing a DNA corona which allows functionalization, labeling and higher levels of organization due to its specific addressable recognition properties. In contrast, self-assembly of natural silk proteins as well as their recombinant variants yields mechanically stable β-sheet rich nanostructures. The combination of silk with abiotic polymers gains hybrid materials with new functionalities. Together, the precision of DNA hybridization and robustness of silk fibrillar structures combine in novel conjugates enable processing of higher-order structures with nanoscale architecture and programmable functions.

Nanoscale chemical mapping of laser-solubilized silk

NASA Astrophysics Data System (ADS)

Ryu, Meguya; Kobayashi, Hanae; Balčytis, Armandas; Wang, Xuewen; Vongsvivut, Jitraporn; Li, Jingliang; Urayama, Norio; Mizeikis, Vygantas; Tobin, Mark; Juodkazis, Saulius; Morikawa, Junko

2017-11-01

A water soluble amorphous form of silk was made by ultra-short laser pulse irradiation and detected by nanoscale IR mapping. An optical absorption-induced nanoscale surface expansion was probed to yield the spectral response of silk at IR molecular fingerprinting wavelengths with a high  ˜ 20 nm spatial resolution defined by the tip of the probe. Silk microtomed sections of 1-5 μm in thickness were prepared for nanoscale spectroscopy and a laser was used to induce amorphisation. Comparison of silk absorbance measurements carried out by table-top and synchrotron Fourier transform IR spectroscopy proved that chemical imaging obtained at high spatial resolution and specificity (able to discriminate between amorphous and crystalline silk) is reliably achieved by nanoscale IR. Differences in absorbance and spectral line-shapes of the bands are related to the different sensitivity of the applied methods to real and imaginary parts of permittivity. A nanoscale material characterization by combining synchrotron IR radiation and nano-IR is discussed.

Production of Bombyx mori silk fibroin incorporated with unnatural amino acids.

PubMed

Teramoto, Hidetoshi; Kojima, Katsura

2014-07-14

Silk fibroin incorporated with unnatural amino acids was produced by in vivo feeding of p-chloro-, p-bromo-, and p-azido-substituted analogues of L-phenylalanine (Phe) to transgenic silkworms (Bombyx mori) that expressed a mutant of phenylalanyl-tRNA synthetase with expanded substrate recognition capabilities in silk glands. Cutting down the content of Phe in the diet was effective for increasing the incorporation of Phe analogues but simultaneously caused a decrease of fibroin production. The azide groups incorporated in fibroin were active as chemical handles for click chemistry in both the solubilized and the solid (fibrous) states. The azides survived degumming in the boiling alkaline solution that is required for complete removal of the sericin layer, demonstrating that AzPhe-incorporated silk fibroin could be a versatile platform to produce "clickable" silk materials in various forms. This study indicates the huge potential of UAA mutagenesis as a novel methodology to alter the characteristics of B. mori silk.

Self-assembly of nucleic acids, silk and hybrid materials thereof

NASA Astrophysics Data System (ADS)

Humenik, Martin; Scheibel, Thomas

2014-12-01

Top-down approaches based on etching techniques have almost reached their limits in terms of dimension. Therefore, novel assembly strategies and types of nanomaterials are required to allow technological advances. Self-assembly processes independent of external energy sources and unlimited in dimensional scaling have become a very promising approach. Here, we highlight recent developments in self-assembled DNA-polymer, silk-polymer and silk-DNA hybrids as promising materials with biotic and abiotic moieties for constructing complex hierarchical materials in ‘bottom-up’ approaches. DNA block copolymers assemble into nanostructures typically exposing a DNA corona which allows functionalization, labeling and higher levels of organization due to its specific addressable recognition properties. In contrast, self-assembly of natural silk proteins as well as their recombinant variants yields mechanically stable β-sheet rich nanostructures. The combination of silk with abiotic polymers gains hybrid materials with new functionalities. Together, the precision of DNA hybridization and robustness of silk fibrillar structures combine in novel conjugates enable processing of higher-order structures with nanoscale architecture and programmable functions.

3-D Modeling of Planar Target-Mount Perturbation Experiments on OMEGA

NASA Astrophysics Data System (ADS)

Collins, T. J. B.; Marshall, F. J.; Marozas, J. A.; Bonino, M. J.; Forties, R.; Goncharov, V. N.; Igumenshchev, I. V.; McKenty, P. W.; Smalyuk, V. A.

2008-11-01

OMEGA cryogenic targets are suspended in the target chamber using four spider silks attached to a C-shaped mount. The spider silks are typically composed of two entwined protein strands comparable to 1 μm in diameter. The silks and mount refract the incident laser light and cast shadows on the target surface. Experiments to measure the effects of the silks on target illumination have been performed in planar geometry using silks suspended parallel to a 20-μm-thick laser-driven target. The evolution of the surface perturbations introduced by the silks was measured using x-ray backlighting. The results of these experiments will be compared to simulations performed with DRACO, employing three-dimensional (3-D) planar hydrodynamics and a new 3-D refractive ray-trace package written specifically for this geometry. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-08NA28302.

Bone Tissue Engineering with Premineralized Silk Scaffolds

PubMed Central

Kim, Hyeon Joo; Kim, Ung-Jin; Kim, Hyun Suk; Li, Chunmei; Wada, Masahisa; Leisk, Gary G.; Kaplan, David L.

2009-01-01

Silks fibroin biomaterials are being explored as novel protein-based systems for cell and tissue culture. In the present study, biomimetic growth of calcium phosphate on porous silk fibroin polymeric scaffolds was explored to generate organic/inorganic composites as scaffolds for bone tissue engineering. Aqueous-derived silk fibroin scaffolds were prepared with the addition of polyaspartic acid during processing, followed by the controlled deposition of calcium phosphate by exposure to CaCl2 and Na2HPO4. These mineralized protein-composite scaffolds were subsequently seeded with human bone marrow stem cells (hMSC) and cultured in vitro for 6 weeks under osteogenic conditions with or without BMP-2. The extent of osteoconductivity was assessed by cell numbers, alkaline phosphatase and calcium deposition, along with immunohistochemistry for bone related outcomes. The results suggest increased osteoconductive outcomes with an increase in initial content of apatite and BMP-2 in the silk fibroin porous scaffolds. The premineralization of these highly porous silk fibroin protein scaffolds provided enhanced outcomes for the bone tissue engineering. PMID:18387349

Biocompatibility of helicoidal multilamellar arginine-glycine-aspartic acid-functionalized silk biomaterials in a rabbit corneal model.

PubMed

Wang, Liqiang; Ma, Ruijue; Du, Gaiping; Guo, Huiling; Huang, Yifei

2015-01-01

Silk proteins represent a unique choice in the selection of biomaterials that can be used for corneal tissue engineering and regenerative medical applications. We implanted helicoidal multilamellar arginine-glycine-aspartic acid-functionalized silk biomaterials into the corneal stroma of rabbits, and evaluated its biocompatibility. The corneal tissue was examined after routine hematoxylin-eosin staining, immunofluorescence for collagen I and III, and fibronectin, and scanning electron microscopy. The silk films maintained their integrity and transparency over the 180-day experimental period without causing immunogenic and neovascular responses or degradation of the rabbit corneal stroma. Collagen I increased, whereas Collagen III and fibronectin initially increased and then gradually decreased. The extracellular matrix deposited on the surface of the silk films, tightly adhered to the biomaterial. We have shown this kind of silk film graft has suitable biocompatibility with the corneal stroma and is an initial step for clinical trials to evaluate this material as a transplant biomaterial for keratoplasty tissue constructs. © 2014 Wiley Periodicals, Inc.

Recombinant spider silk from aqueous solutions via a bio-inspired microfluidic chip

NASA Astrophysics Data System (ADS)

Peng, Qingfa; Zhang, Yaopeng; Lu, Li; Shao, Huili; Qin, Kankan; Hu, Xuechao; Xia, Xiaoxia

2016-11-01

Spiders achieve superior silk fibres by controlling the molecular assembly of silk proteins and the hierarchical structure of fibres. However, current wet-spinning process for recombinant spidroins oversimplifies the natural spinning process. Here, water-soluble recombinant spider dragline silk protein (with a low molecular weight of 47 kDa) was adopted to prepare aqueous spinning dope. Artificial spider silks were spun via microfluidic wet-spinning, using a continuous post-spin drawing process (WS-PSD). By mimicking the natural spinning apparatus, shearing and elongational sections were integrated in the microfluidic spinning chip to induce assembly, orientation of spidroins, and fibril structure formation. The additional post-spin drawing process following the wet-spinning section partially mimics the spinning process of natural spider silk and substantially contributes to the compact aggregation of microfibrils. Subsequent post-stretching further improves the hierarchical structure of the fibres, including the crystalline structure, orientation, and fibril melting. The tensile strength and elongation of post-treated fibres reached up to 510 MPa and 15%, respectively.

Silk/nano-material hybrid: properties and functions

NASA Astrophysics Data System (ADS)

Steven, Eden; Lebedev, Victor; Laukhina, Elena; Laukhin, Vladimir; Alamo, Rufina G.; Rovira, Concepcio; Veciana, Jaume; Brooks, James S.

2014-03-01

Silk continues to emerge as a material of interest in electronics. In this work, the interaction between silk and conducting nano-materials are investigated. Simple fabrication methods, physical, electronic, thermal, and actuation properties are reported for spider silk / carbon nanotube (CNT-SS) and Bombyx mori / (BEDT-TTF)-based organic molecular conductor hybrids (ET-S). The CNT-SS fibers are produced via water and shear assisted method, resulting in fibers that are tough, custom-shapeable, flexible, and electrically conducting. For ET-S bilayer films, a layer transfer technique is developed to deposit linked crystallites of (BEDT-TTF)2I3 molecular conductor onto silk films, generating highly piezoresistive semi-transparent films. In both cases, the hybridization allows us to gain additional functions by harnessing the water-dependent properties of silk materials, for example, as humidity sensor and electrical current- or water-driven actuators. SEM, TEM, FT-IR, and resistance measurements under varying temperature, strain, and relative humidity reveal the synergistic interactions between the bio- and nano-materials. E.S. is supported by NSF-DMR 1005293.

Preliminary Characterization of Genipin-Cross-Linked Silk Sericin/Poly(vinyl alcohol) Films as Two-Dimensional Wound Dressings for the Healing of Superficial Wounds

PubMed Central

Siritientong, Tippawan; Ratanavaraporn, Juthamas; Srichana, Teerapol; Aramwit, Pornanong

2013-01-01

The genipin-cross-linked silk sericin/poly(vinyl alcohol) (PVA) films were developed aiming to be applied as two-dimensional wound dressings for the treatment of superficial wounds. The effects of genipin cross-linking concentration on the physical and biological properties of the films were investigated. The genipin-cross-linked silk sericin/PVA films showed the increased surface density, tensile strength, and percentage of elongation, but decreased percentage of light transmission, water vapor transmission rate, and water swelling, compared to the non-cross-linked films. This explained that the cross-linking bonds between genipin and silk sericin would reduce the mobility of molecular chains within the films, resulting in the more rigid molecular structure. Silk sericin was released from the genipin-cross-linked films in a sustained manner. In addition, either L929 mouse fibroblast or HaCat keratinocyte cells showed high percentage of viability when cultured on the silk sericin/PVA films cross-linked with 0.075 and 0.1% w/v genipin. The in vivo safety test performed according to ISO 10993-6 confirmed that the genipin-cross-linked silk sericin/PVA films were safe for the medical usages. The efficacy of the films for the treatment of superficial skin wounds will be further investigated in vivo and clinically. The genipin-cross-linked silk sericin/PVA films would be promising choices of two-dimensional wound dressings for the treatment of superficial wounds. PMID:24106722

Preliminary characterization of genipin-cross-linked silk sericin/poly(vinyl alcohol) films as two-dimensional wound dressings for the healing of superficial wounds.

PubMed

Siritientong, Tippawan; Ratanavaraporn, Juthamas; Srichana, Teerapol; Aramwit, Pornanong

2013-01-01

The genipin-cross-linked silk sericin/poly(vinyl alcohol) (PVA) films were developed aiming to be applied as two-dimensional wound dressings for the treatment of superficial wounds. The effects of genipin cross-linking concentration on the physical and biological properties of the films were investigated. The genipin-cross-linked silk sericin/PVA films showed the increased surface density, tensile strength, and percentage of elongation, but decreased percentage of light transmission, water vapor transmission rate, and water swelling, compared to the non-cross-linked films. This explained that the cross-linking bonds between genipin and silk sericin would reduce the mobility of molecular chains within the films, resulting in the more rigid molecular structure. Silk sericin was released from the genipin-cross-linked films in a sustained manner. In addition, either L929 mouse fibroblast or HaCat keratinocyte cells showed high percentage of viability when cultured on the silk sericin/PVA films cross-linked with 0.075 and 0.1% w/v genipin. The in vivo safety test performed according to ISO 10993-6 confirmed that the genipin-cross-linked silk sericin/PVA films were safe for the medical usages. The efficacy of the films for the treatment of superficial skin wounds will be further investigated in vivo and clinically. The genipin-cross-linked silk sericin/PVA films would be promising choices of two-dimensional wound dressings for the treatment of superficial wounds.

Nanostructural and mechanical property changes to spider silk as a consequence of insecticide exposure.

PubMed

Benamú, Marco; Lacava, Mariángeles; García, Luis F; Santana, Martín; Fang, Jian; Wang, Xungai; Blamires, Sean J

2017-08-01

Neonicotinoids are one of the world's most extensively used insecticides, but their sub-lethal influences on non-target and beneficial organisms are not well known. Here we exposed the orb web spider Parawixia audax, which is found on arable lands in Uruguay, to a sub-lethal concentration of the broad spectrum insecticide Geonex (thiamethoxam + lambda-cyhalothrin) and monitored their web building. We collected their major ampullate silk and subjected it to tensile tests, wide-angle X-ray diffraction (WAXS) analysis, and amino acid composition analysis. Around half of the exposed spiders failed to build webs. Those that built webs produced irregular webs lacking spiral threads. The mechanical properties, nanostructures, and amino acid compositions of the silk were all significantly affected when the spiders were exposed to insecticides. We found that silk proline, glutamine, alanine and glycine compositions differed between treatments, indicating that insecticide exposure induced downregulation of the silk protein MaSp2. The spiders in the control group had stronger, tougher and more extensible silks than those in the insecticide exposed group. Our WAXS analyses showed the amorphous region nanostructures became misaligned in insecticide exposed silks, explaining their greater stiffness. While the insecticide dose we subjected P. audax to was evidently sub-lethal, the changes in silk physicochemical properties and the impairment to web building will indelibly affect their ability to catch prey. Copyright © 2017 Elsevier Ltd. All rights reserved.

Low-Tech, Pilot Scale Purification of a Recombinant Spider Silk Protein Analog from Tobacco Leaves.

PubMed

Heppner, René; Weichert, Nicola; Schierhorn, Angelika; Conrad, Udo; Pietzsch, Markus

2016-10-09

Spider dragline is used by many members of the Araneae family not only as a proteinogenic safety thread but also for web construction. Spider dragline has been shown to possess high tensile strength in combination with elastic behavior. This high tensile strength can be attributed to the presence of antiparallel β-sheets within the thread; these antiparallel β-sheets are why the protein is classified as a silk. Due to the properties of spider silk and its technical and medical uses, including its use as a suture material and as a scaffold for tissue regeneration, spider dragline is a focus of the biotechnology industry. The production of sufficient amounts of spider silk is challenging, as it is difficult to produce large quantities of fibers because of the cannibalistic behavior of spiders and their large spatial requirements. In recent years, the heterologous expression of genes coding for spider silk analogs in various hosts, including plants such as Nicotiana tabacum , has been established. We developed a simple and scalable method for the purification of a recombinant spider silk protein elastin-like peptide fusion protein (Q-/K-MaSp1-100× ELP) after heterologous production in tobacco leaves involving heat and acetone precipitation. Further purification was performed using centrifugal Inverse Transition Cycling (cITC). Up to 400 mg of highly pure spider silk protein derivatives can be isolated from six kilograms of tobacco leaves, which is the highest amount of silk protein derivatives purified from plants thus far.

Nonlinear material behaviour of spider silk yields robust webs.

PubMed

Cranford, Steven W; Tarakanova, Anna; Pugno, Nicola M; Buehler, Markus J

2012-02-01

Natural materials are renowned for exquisite designs that optimize function, as illustrated by the elasticity of blood vessels, the toughness of bone and the protection offered by nacre. Particularly intriguing are spider silks, with studies having explored properties ranging from their protein sequence to the geometry of a web. This material system, highly adapted to meet a spider's many needs, has superior mechanical properties. In spite of much research into the molecular design underpinning the outstanding performance of silk fibres, and into the mechanical characteristics of web-like structures, it remains unknown how the mechanical characteristics of spider silk contribute to the integrity and performance of a spider web. Here we report web deformation experiments and simulations that identify the nonlinear response of silk threads to stress--involving softening at a yield point and substantial stiffening at large strain until failure--as being crucial to localize load-induced deformation and resulting in mechanically robust spider webs. Control simulations confirmed that a nonlinear stress response results in superior resistance to structural defects in the web compared to linear elastic or elastic-plastic (softening) material behaviour. We also show that under distributed loads, such as those exerted by wind, the stiff behaviour of silk under small deformation, before the yield point, is essential in maintaining the web's structural integrity. The superior performance of silk in webs is therefore not due merely to its exceptional ultimate strength and strain, but arises from the nonlinear response of silk threads to strain and their geometrical arrangement in a web.

Gold nanoparticle-embedded silk protein-ZnO nanorod hybrids for flexible bio-photonic devices

NASA Astrophysics Data System (ADS)

Gogurla, Narendar; Kundu, Subhas C.; Ray, Samit K.

2017-04-01

Silk protein has been used as a biopolymer substrate for flexible photonic devices. Here, we demonstrate ZnO nanorod array hybrid photodetectors on Au nanoparticle-embedded silk protein for flexible optoelectronics. Hybrid samples exhibit optical absorption at the band edge of ZnO as well as plasmonic energy due to Au nanoparticles, making them attractive for selective UV and visible wavelength detection. The device prepared on Au-silk protein shows a much lower dark current and a higher photo to dark-current ratio of ∼105 as compared to the control sample without Au nanoparticles. The hybrid device also exhibits a higher specific detectivity due to higher responsivity arising from the photo-generated hole trapping by Au nanoparticles. Sharp pulses in the transient photocurrent have been observed in devices prepared on glass and Au-silk protein substrates due to the light induced pyroelectric effect of ZnO, enabling the demonstration of self-powered photodetectors at zero bias. Flexible hybrid detectors have been demonstrated on Au-silk/polyethylene terephthalate substrates, exhibiting characteristics similar to those fabricated on rigid glass substrates. A study of the performance of photodetectors with different bending angles indicates very good mechanical stability of silk protein based flexible devices. This novel concept of ZnO nanorod array photodetectors on a natural silk protein platform provides an opportunity to realize integrated flexible and self-powered bio-photonic devices for medical applications in near future.

Rate-dependent behavior of the amorphous phase of spider dragline silk.

PubMed

Patil, Sandeep P; Markert, Bernd; Gräter, Frauke

2014-06-03

The time-dependent stress-strain behavior of spider dragline silk was already observed decades ago, and has been attributed to the disordered sequences in silk proteins, which compose the soft amorphous matrix. However, the actual molecular origin and magnitude of internal friction within the amorphous matrix has remained inaccessible, because experimentally decomposing the mechanical response of the amorphous matrix from the embedded crystalline units is challenging. Here, we used atomistic molecular dynamics simulations to obtain friction forces for the relative sliding of peptide chains of Araneus diadematus spider silk within bundles of these chains as a representative unit of the amorphous matrix in silk fibers. We computed the friction coefficient and coefficient of viscosity of the amorphous phase to be in the order of 10(-6) Ns/m and 10(4) Ns/m(2), respectively, by extrapolating our simulation data to the viscous limit. Finally, we used a finite element method for the amorphous phase, solely based on parameters derived from molecular dynamics simulations including the newly determined coefficient of viscosity. With this model the time scales of stress relaxation, creep, and hysteresis were assessed, and found to be in line with the macroscopic time-dependent response of silk fibers. Our results suggest the amorphous phase to be the primary source of viscosity in silk and open up the avenue for finite element method studies of silk fiber mechanics including viscous effects. Copyright © 2014 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Transcript Profile Analyses of Maize Silks Reveal Effective Activation of Genes Involved in Microtubule-Based Movement, Ubiquitin-Dependent Protein Degradation, and Transport in the Pollination Process

PubMed Central

Chen, Hao; Sun, Wei; Zhang, Xian Sheng

2013-01-01

Pollination is the first crucial step of sexual reproduction in flowering plants, and it requires communication and coordination between the pollen and the stigma. Maize (Zea mays) is a model monocot with extraordinarily long silks, and a fully sequenced genome, but little is known about the mechanism of its pollen–stigma interactions. In this study, the dynamic gene expression of silks at four different stages before and after pollination was analyzed. The expression profiles of immature silks (IMS), mature silks (MS), and silks at 20 minutes and 3 hours after pollination (20MAP and 3HAP, respectively) were compared. In total, we identified 6,337 differentially expressed genes in silks (SDEG) at the four stages. Among them, the expression of 172 genes were induced upon pollination, most of which participated in RNA binding, processing and transcription, signal transduction, and lipid metabolism processes. Genes in the SDEG dataset could be divided into 12 time-course clusters according to their expression patterns. Gene Ontology (GO) enrichment analysis revealed that many genes involved in microtubule-based movement, ubiquitin-mediated protein degradation, and transport were predominantly expressed at specific stages, indicating that they might play important roles in the pollination process of maize. These results add to current knowledge about the pollination process of grasses and provide a foundation for future studies on key genes involved in the pollen–silk interaction in maize. PMID:23301084

Tulane/Xavier Vaccine Peptide Program

DTIC Science & Technology

2013-07-01

include a dry powder formulation, microemulsions , nonspherical liposomes, ceramic shell vesicles, and nanometer-sized silk particles. Nasal...pulmonary delivery: dry powder formulation, microemulsions , nonspherical liposomes, ceramic shell vesicles, and nanometer-sized silk particles. (3) Confirm...include a dry powder formulation, microemulsions , nonspherical liposomes, ceramic shell vesicles, and nanometer-sized silk particles. Nasal

Drawing-induced changes in morphology and mechanical properties of hornet silk gel films.

PubMed

Kameda, Tsunenori; Kojima, Katsura; Togawa, Eiji; Sezutsu, Hideki; Zhang, Qiang; Teramoto, Hidetoshi; Tamada, Yasushi

2010-04-12

Complete amino acid sequences of the four major proteins (Vssilk 1-4) of silk (hornet silk) obtained from yellow hornet ( Vespa simillima , Vespinae, Vespidae) cocoons have been determined. The native structure of the hornet silk (HS), in which Vssilk 1-4 have an alpha-helix domain with coiled-coil alpha-helices and a beta-sheet domain, is restored when hornet silk gel films (HSGFs) are formed by pressing and drying HS hydrogel. Necking occurs when dry HSGFs are drawn; however, wet HSGFs can be uniaxially drawn with a draw ratio (DR) of 2. Drawing helps obtain high-performance films with a maximum tensile strength and tensile modulus of 170 MPa and 5.5 GPa, respectively. Drawing-induced changes in the orientation and conformation of the coiled-coil structure are investigated.

Water-driven actuation of Ornithoctonus huwena spider silk fibers

NASA Astrophysics Data System (ADS)

Lin, Shuyuan; Zhu, Jia; Li, Xinming; Guo, Yang; Fang, Yaopeng; Cheng, Huanyu; Zhu, Hongwei

2017-01-01

Spider silk possesses remarkable mechanical properties and can lift weight effectively. Certain kinds of spider silk have unique response to liquid, especially water, because of their hydrophilic proteins, β-sheet characters, and surface structure. The Ornithoctonus huwena (O. huwena) spider is a unique species because it can be bred artificially and it spins silk whose diameter is in nanometer scale. In this work, we report the "shrink-stretch" behavior of the O. huwena spider silk fibers and show how they can be actuated by water to lift weight over long distance, at a fast speed, and with high efficiency. We further rationalize this behavior by analyzing the mechanical energy of the system. The lifting process is energy-efficient and environmentally friendly, allowing applications in actuators, biomimetic muscles, or hoisting devices.

Dual-functional composite with anticoagulant and antibacterial properties based on heparinized silk fibroin and chitosan.

PubMed

Wang, Jianglin; Hu, Wei; Liu, Qun; Zhang, Shengmin

2011-07-01

Heparinized biomaterials exhibit great anticoagulant properties. However, they promote proliferation of Staphylococcus aureus (S. aureus) and therefore cause infection within the bloodstream upon implantation in vivo. In the present study, an interesting dual-functional composite with anticoagulant and antibacterial properties based on heparinized silk fibroin and chitosan was synthesized. First, heparin was grafted onto the silk fibroin by covalent immobilization with N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide (EDC) and N-hydroxysuccinimide (NHS). All data gathered from Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and elemental analysis (EA) indicated that the heparin was successfully immobilized onto the silk fibroin. The dual-functional composite of heparinized silk fibroin and chitosan was then fabricated by a blending method. The anticoagulant activity of the heparinized materials was evaluated using the prothrombin time (PT), activated partial thromboplastin time (APTT) and thrombin time (TT). The results showed that both heparinized silk fibroin and the composite material exhibited better hemocompatibility in comparison with single silk fibroin or chitosan. The antibacterial property of the materials was investigated by the pour-plate method. Results further suggested that the composite antibacterial property with respect to S. aureus was significantly enhanced. The dual-functionality of the composite material may supply a potential choice in blood contact devices. Copyright © 2011 Elsevier B.V. All rights reserved.

Water permeability of spider dragline silk.

PubMed

Li, Xiang; Eles, Philip T; Michal, Carl A

2009-05-11

The water permeability of spider dragline silk was studied by measuring changes in amide deuteration of D(2)O-soaked silk with solid-state NMR. (13)C-D rotational-echo double-resonance (REDOR) NMR experiments showed that chemical exchange of amide hydrogen occurs in a large fraction of amino acids, including over 50% of alanine residues, which are known to exist predominantly in beta-sheet crystallites. This suggests that a substantial fraction of the crystalline regions are permeable to water, at least on the time scale of hours, implying that they are more dynamic, and therefore susceptible to chemical exchange with water, than previously thought. Wideline deuterium NMR spectra of dried D(2)O-soaked silk showed a combination of quadrupolar broadened and motionally averaged isotropic components whose intensities change on the time scale of hours. These results are interpreted in terms of chemical exchange between deuterium on the protein backbone, residual water within the silk, and water vapor in the ambient atmosphere. A simple compartmental model fits the results well and yields rate constants for the exchange processes. The model requires the inclusion of a compartment that does not undergo exchange. This compartment, likely related to the crystalline region, is interesting because it is accessible to water in wet silk, but impervious to any remaining free water when the silk is dried.

Sericin removal from raw Bombyx mori silk scaffolds of high hierarchical order.

PubMed

Teuschl, Andreas Herbert; van Griensven, Martijn; Redl, Heinz

2014-05-01

Silk fibroin has previously been described as a promising candidate for ligament tissue engineering (TE) approaches. For biocompatibility reasons, silkworm silk requires removal of sericin, which can elicit adverse immune responses in the human body. One disadvantage of the required degumming process is the alteration of the silk fiber structural properties, which can hinder textile engineering of high order hierarchical structures. Therefore, the aim of this study was to find a way to remove sericin from a compact and highly ordered raw silk fiber matrix. The wire rope design of the test model scaffold comprises several levels of geometric hierarchy. Commonly used degumming solutions fail in removing sericin in this wire rope design. Weight loss measurements, picric acid and carmine staining as well as scanning electron microscopy demonstrated that the removal of sericin from the model scaffold of a wire rope design can be achieved through a borate buffer-based system. Furthermore, the borate buffer degummed silks were shown to be nontoxic and did not alter cell proliferation behavior. The possibility to remove sericin after the textile engineering process has taken place eases the production of highly ordered scaffold structures and may expand the use of silk as scaffold material in further TE and regenerative medicine applications.

Potential of 3-D tissue constructs engineered from bovine chondrocytes / silk fibroin-chitosan for in vitro cartilage tissue engineering

PubMed Central

Bhardwaj, Nandana; Nguyen, Quynhhoa T; Chen, Albert C; Kaplan, David L.; Sah, Robert L; Kundu, Subhas C

2011-01-01

The use of cell-scaffold constructs is a promising tissue engineering approach to repair cartilage defects and to study cartilaginous tissue formation. In this study, silk fibroin/chitosan blended scaffolds were fabricated and studied for cartilage tissue engineering. Silk fibroin served as a substrate for cell adhesion and proliferation while chitosan has a structure similar to that of glycosaminoglycans, and shows promise for cartilage repair. We compared the formation of cartilaginous tissue in silk fibroin/chitosan blended scaffolds seeded with bovine chondrocytes and cultured in vitro for 2 weeks. The constructs were analyzed for cell viability, histology, extracellular matrix components glycosaminoglycan and collagen types I and II, and biomechanical properties. Silk fibroin/chitosan scaffolds supported cell attachment and growth, and chondrogenic phenotype as indicated by Alcian Blue histochemistry and relative expression of type II versus type I collagen. Glycosaminoglycan and collagen accumulated in all the scaffolds and was highest in the silk fibroin/chitosan (1:1) blended scaffolds. Static and dynamic stiffness at high frequencies was higher in cell-seeded constructs than non-seeded controls. The results suggest that silk/chitosan scaffolds may be a useful alternative to synthetic cell scaffolds for cartilage tissue engineering. PMID:21601277

Silk Fibroin as Edible Coating for Perishable Food Preservation

NASA Astrophysics Data System (ADS)

Marelli, B.; Brenckle, M. A.; Kaplan, D. L.; Omenetto, F. G.

2016-05-01

The regeneration of structural biopolymers into micelles or nanoparticles suspended in water has enabled the design of new materials with unique and compelling properties that can serve at the interface between the biotic and the abiotic worlds. In this study, we leveraged silk fibroin quintessential properties (i.e. polymorphism, conformability and hydrophobicity) to design a water-based protein suspension that self-assembles on the surface of food upon dip coating. The water-based post-processing control of the protein polymorphism enables the modulation of the diffusion of gases through the silk fibroin thin membranes (e.g. O2 and CO2 diffusion, water vapour permeability), which is a key parameter to manage food freshness. In particular, an increased beta-sheet content corresponds to a reduction in oxygen diffusion through silk fibroin thin films. By using the dip coating of strawberries and bananas as proof of principle, we have shown that the formation of micrometre-thin silk fibroin membranes around the fruits helps the management of postharvest physiology of the fruits. Thus, silk fibroin coatings enhance fruits’ shelf life at room conditions by reducing cell respiration rate and water evaporation. The water-based processing and edible nature of silk fibroin makes this approach a promising alternative for food preservation with a naturally derived material.

Comparative architecture of silks, fibrous proteins and their encoding genes in insects and spiders.

PubMed

Craig, Catherine L; Riekel, Christian

2002-12-01

The known silk fibroins and fibrous glues are thought to be encoded by members of the same gene family. All silk fibroins sequenced to date contain regions of long-range order (crystalline regions) and/or short-range order (non-crystalline regions). All of the sequenced fibroin silks (Flag or silk from flagelliform gland in spiders; Fhc or heavy chain fibroin silks produced by Lepidoptera larvae) are made up of hierarchically organized, repetitive arrays of amino acids. Fhc fibroin genes are characterized by a similar molecular genetic architecture of two exons and one intron, but the organization and size of these units differs. The Flag, Ser (sericin gene) and BR (Balbiani ring genes; both fibrous proteins) genes are made up of multiple exons and introns. Sequences coding for crystalline and non-crystalline protein domains are integrated in the repetitive regions of Fhc and MA exons, but not in the protein glues Ser1 and BR-1. Genetic 'hot-spots' promote recombination errors in Fhc, MA, and Flag. Codon bias, structural constraint, point mutations, and shortened coding arrays may be alternative means of stabilizing precursor mRNA transcripts. Differential regulation of gene expression and selective splicing of the mRNA transcript may allow rapid adaptation of silk functional properties to different physical environments.

Enhanced Cellular Adhesion on Titanium by Silk Functionalized with titanium binding and RGD peptides

PubMed Central

Vidal, Guillaume; Blanchi, Thomas; Mieszawska, Aneta J.; Calabrese, Rossella; Rossi, Claire; Vigneron, Pascale; Duval, Jean-Luc; Kaplan, David L.; Egles, Christophe

2012-01-01

Soft tissue adhesion on titanium represents a challenge for implantable materials. In order to improve adhesion at the cell/material interface we used a new approach based on the molecular recognition of titanium by specific peptides. Silk fibroin protein was chemically grafted with titanium binding peptide (TiBP) to increase adsorption of these chimeric proteins to the metal surface. Quartz Crystal Microbalance was used to quantify the specific adsorption of TiBP-functionalized silk and an increase in protein deposition by more than 35% was demonstrated due to the presence of the binding peptide. A silk protein grafted with TiBP and fibronectin-derived RGD peptide was then prepared. The adherence of fibroblasts on the titanium surface modified with the multifunctional silk coating demonstrated an increase in the number of adhering cells by 60%. The improved adhesion was demonstrated by Scanning Electron Microscopy and immunocytochemical staining of focal contact points. Chick embryo organotypic culture also revealed strong adhesion of endothelial cells expanding on the multifunctional silk-peptide coating. These results demonstrated that silk functionalized with TiBP and RGD represents a promising approach to modify cell-biomaterial interfaces, opening new perspectives for implantable medical devices, especially when reendothelialization is required. PMID:22975628

Photoluminescent properties of spider silk coated with Eu-doped nanoceria

NASA Astrophysics Data System (ADS)

Dmitrović, Svetlana; Nikolić, Marko G.; Jelenković, Branislav; Prekajski, Marija; Rabasović, Mihailo; Zarubica, Aleksandra; Branković, Goran; Matović, Branko

2017-02-01

Spider dragline silk was coated with pure as well as Eu-doped ceria nanopowders at the room temperature. The treatment was done by immersion of the spider silk mesh into aqueous solutions of cerium nitrate (Ce(NO3)3) and ammonium hydroxide (NH4OH). Depending on the relationship between Ce3+ ion and ammonium hydroxide concentration, coated fibers exhibited a different thickness. Obtained materials were studied by means of FESEM. It was found that ceria nanoparticles of average size of 3 nm were coated along spider thread. X-ray diffraction (XRD) and selected-area electron diffraction (SAED) confirmed crystal nature of nanoparticle coating of spider silk. By using Williamson-Hall plots, crystallite size and strain were estimated. EDS measurement confirmed the presence of Eu in spider-Eu-doped ceria composite, and according to FTIR analysis, the interaction between CeO2 and spider silk was proposed. The morphology of obtained composite was observed by TEM. The photoluminescence emission spectra of spider silk coated with Eu-doped ceria were measured with two different excitations of 385 and 466 nm. The two-photon excited auto-fluorescence of spider silk coated with Eu-doped ceria was detected using a nonlinear laser scanning microscope. Obtained composite has a potential as a fluorescent labeling material in diverse applications.

Amorphous Silk Fibroin Membranes for Separation of CO2

NASA Technical Reports Server (NTRS)

Aberg, Christopher M.; Patel, Anand K.; Gil, Eun Seok; Spontak, Richard J.; Hagg, May-Britt

2009-01-01

Amorphous silk fibroin has shown promise as a polymeric material derivable from natural sources for making membranes for use in removing CO2 from mixed-gas streams. For most applications of silk fibroin, for purposes other than gas separation, this material is used in its highly crystalline, nearly natural form because this form has uncommonly high tensile strength. However, the crystalline phase of silk fibroin is impermeable, making it necessary to convert the material to amorphous form to obtain the high permeability needed for gas separation. Accordingly, one aspect of the present development is a process for generating amorphous silk fibroin by treating native silk fibroin in an aqueous methanol/salt solution. The resulting material remains self-standing and can be prepared as thin film suitable for permeation testing. The permeability of this material by pure CO2 has been found to be highly improved, and its mixed-gas permeability has been found to exceed the mixed-gas permeabilities of several ultrahigh-CO2-permeable synthetic polymers. Only one of the synthetic polymers poly(trimethylsilylpropyne) [PTMSP] may be more highly permeable by CO2. PTMSP becomes unstable with time, whereas amorphous silk should not, although at the time of this reporting this has not been conclusively proven.

Sodium ion effect on silk fibroin conformation characterized by solid-state NMR and generalized 2D NMR NMR correlation

NASA Astrophysics Data System (ADS)

Ruan, Qing-Xia; Zhou, Ping

2008-07-01

In the present work, we investigated Na + ion effect on the silk fibroin (SF) conformation. Samples are Na +-involved regenerated silk fibroin films. 13C CP-MAS NMR demonstrates that as added [Na +] increases, partial silk fibroin conformation transit from helix-form to β-form at certain Na + ion concentration which is much higher than that in Bombyx mori silkworm gland. The generalized two-dimensional NMR-NMR correlation analysis reveals that silk fibroin undergoes several intermediate states during its conformation transition process as [Na +] increase. The appearance order of the intermediates is followed as: helix and/or random coil → helix-like → β-sheet-like → β-sheet, which is the same as that produced by pH decrease from 6.8 to 4.8 in the resultant regenerated silk fibroin films. The binding sites of Na + to silk fibroin might involve the carbonyl oxygen atom of certain amino acids sequence which could promote the formation of β-sheet conformation. Since the Na +sbnd O bond is weak, the ability of Na + inducing the secondary structure transition is weaker than those of Ca 2+, Cu 2+ and even K +. It is maybe a reason why the sodium content is much lower than potassium in the silkworm gland.

Highly-transparent multi-layered spin-coated silk fibroin film

NASA Astrophysics Data System (ADS)

Wasapinyokul, Kamol; Kaewpirom, Supranee; Chuwongin, Santhad; Boonsang, Siridech

2017-10-01

In this study, the silk fibroin films with different numbers of layers were fabricated by the spin-coating method and their optical transmittances were observed. The process to synthesise the silk fibroin solution was explained - starting from the silk cocoon until the silk-fibroin solution, approximately 7.5% concentration wt/vol, was obtained. The solution was spin-coated onto clean glass substrates to fabricate samples. Totally 10 samples with different numbers of layers, from 1 to 5 layers, were obtained. All samples can be separated into two groups: those left dried at room temperature after spin-coating and those heated at 60°C. They were then measured for their transmittance over the visible-to-near-infrared region. All samples exhibited the high transmittance where the values were at 95% and 98%, for the samples at room temperature and those at 60°C, respectively. This was believed to be due to the heating effect that caused the silk fibroin to arrange itself after being heated, hence the higher transmittance. These high transmittances were maintained regardless of the number of layers and length of heating time. Results from this study could be used to fabricate a silk fibroin film with high optical transmittance and adjustable other properties.

Silk Fibroin as Edible Coating for Perishable Food Preservation

PubMed Central

Marelli, B.; Brenckle, M. A.; Kaplan, D. L.; Omenetto, F. G.

2016-01-01

The regeneration of structural biopolymers into micelles or nanoparticles suspended in water has enabled the design of new materials with unique and compelling properties that can serve at the interface between the biotic and the abiotic worlds. In this study, we leveraged silk fibroin quintessential properties (i.e. polymorphism, conformability and hydrophobicity) to design a water-based protein suspension that self-assembles on the surface of food upon dip coating. The water-based post-processing control of the protein polymorphism enables the modulation of the diffusion of gases through the silk fibroin thin membranes (e.g. O2 and CO2 diffusion, water vapour permeability), which is a key parameter to manage food freshness. In particular, an increased beta-sheet content corresponds to a reduction in oxygen diffusion through silk fibroin thin films. By using the dip coating of strawberries and bananas as proof of principle, we have shown that the formation of micrometre-thin silk fibroin membranes around the fruits helps the management of postharvest physiology of the fruits. Thus, silk fibroin coatings enhance fruits’ shelf life at room conditions by reducing cell respiration rate and water evaporation. The water-based processing and edible nature of silk fibroin makes this approach a promising alternative for food preservation with a naturally derived material. PMID:27151492

Injectable silk foams for the treatment of cervical insufficiency

NASA Astrophysics Data System (ADS)

Fournier, Eric P.

Preterm birth is the leading cause of neonatal mortality, resulting in over 4,000 deaths each year. A significant risk factor for preterm birth is cervical insufficiency, the weakening and subsequent deformation of cervical tissue. Cervical insufficiency is both detectable and treatable but current treatments are lacking. The most common approach requires multiple invasive procedures. This work investigates the injection of silk foams, a minimally-invasive method for supporting cervical tissue. Silk offers many advantages for use as a biomaterial including strength, versatility, and biocompatibility. Injectable silk foams will minimize patient discomfort while also providing more targeted and personalized treatment. A battery of mechanical testing was undertaken to determine silk foam response under physiologically relevant loading and environmental conditions. Mechanical testing was paired with analysis of foam morphology and structure that illustrated the effects of injection on pore geometry and size. Biological response to silk foams was evaluated using an in vitro degradation study and subcutaneous in vivo implantation in a mouse model. Results showed that foams exceeded the mechanical requirements for stiffening cervical tissue, although the current injection process limits foam size. Injection was shown to cause measurable but localized foam deformation. This work indicates that silk foams are a feasible treatment option for cervical insufficiency but challenges remain with foam delivery.

Physical properties of organic and biomaterials: Fundamentals and applications

NASA Astrophysics Data System (ADS)

Steven, Eden

Silk materials are natural protein-based materials with an exceptional toughness. In addition to their toughness, silk materials also possess complex physical properties and functions resulting from a particular set of amino-acid arrangement that produces structures with crystalline beta-sheets connected by amorphous chains. Extensive studies have been performed to study their structure-function relationship leading to recent advancements in bio-integrated devices. Applications to fields other than textiles and biomedicine, however, have been scarce. In this dissertation, an investigation of the electronic properties, functionalization, and role of silk materials (spider silk and Bombyx mori cocoon silk) in the field of organic materials research is presented. The investigation is conducted from an experimental physics point of view where correlations with charge transport mechanisms in disordered, semiconducting, and insulating materials are made when appropriate. First, I present the electronic properties of spider silk fibers under ambient, humidified, iodized, polar solvent exposure, and pyrolized conditions. The conductivity is exponentially dependent on relative humidity changes and the solvent polarity. Iodine doping increases the conductivity only slightly but has pronounced effects on the pyrolization process, increasing the yield and flexibility of the pyrolized silk fibers. The iodized samples were further studied using magic angle spinning nuclear magnetic resonance (MAS-NMR) and Fourier transform infrared spectroscopy (FTIR) revealing non-homogenous iodine doping and I2 induced hydrogenation that are responsible for the minimal conductivity improvement and the pyrolization effects, respectively. Next, I present the investigation of silk fiber functionalization with gold and its role in electrical measurements. The gold functionalized silk fiber (Au-SS) is metallic down to cryogenic temperatures, has a certain amount of flexibility, and possesses magnetic field independent conductivity at low temperatures. This allows their use as micro-wires and flexible electrodes for transport measurements of small organic samples. I also found that neat spider silk fiber can be used as the mask for lithographic processes, providing a simple route of fabricating adhesive stamp electrodes for measuring transport properties of supra-micron samples in the lateral range of 15 mum--100 mum and thickness > 1 mum at low temperatures and high magnetic fields. The current-voltage characteristic of the insulating channel in tape adhesive electrodes revealed Fowler-Nordheim tunneling mechanism. For electronic sensing and actuating device applications, I have developed a simple method for silk functionalization with carbon nanotubes (CNT) facilitated by polar attraction and supercontraction, a phenomenon where silk is softened when exposed to water. Uniform CNT coating and CNT penetration into the silk fiber surface are evident from the SEM and cross-sectional TEM studies. The conductivity of the carbon nanotube functionalized silk fiber (CNT-SS) follows variable range hopping behavior with activation energy similar to that observed in buckpaper. In addition to being electrically conducting, the CNT-SS is custom-shapeable, flexible, and sensitive to humidity, allowing its use as a heart-pulse and humidity resistive sensors, as well as for current-driven actuators. Finally, I present the investigation of the processed Bombyx mori silk thin film. The silk thin film exhibits actuating and self-healing properties similar to those of a biological muscle. Proof-of-concept silk-based bio-mimetic muscle and water-based memory device are demonstrated. The silk thin film is also used as the dielectric layer of a diF-TESADT organic field effect transistor (FET) where I observed a lower operating voltage and an enhancement in the mobility of the device compared with the FET using SiO 2 dielectric layer, accompanied with an anomalous source-drain current-voltage characteristics. This dissertation aims to demonstrate the different aspects of exercising experimental physics to an inter-disciplinary research subject. The fundamental characterization and instrumentation developed in this work are intended to stimulate future discoveries by providing new experimental tools to study electronic transport properties of new materials. In addition, the device fabrication principles will be valuable for development of more environmental-friendly electronics. The treatment presented in this dissertation should serve as a roadmap for future studies of natural materials from an experimental physics point of view.

Enhancing analysis of cells and proteins by fluorescence imaging on silk-based biomaterials: modulating the autofluorescence of silk.

PubMed

Neo, Puay Yong; Tan, Daryl Jian-An; Shi, Pujiang; Toh, Siew Lok; Goh, James Cho-Hong

2015-02-01

Silk is a versatile and established biomaterial for various tissue engineering purposes. However, it also exhibits strong autofluorescence signals-thereby hindering fluorescence imaging analysis of cells and proteins on silk-derived biomaterials. Sudan Black B (SB) is a lysochrome dye commonly used to stain lipids in histology. It has also been reported to be able to quench autofluorescence of tissues in histology and has been tested on artificial biomedical polymers in recent years. It was hypothesized that SB would exert similar quenching effects on silk, modulating the autofluorescence signals, and thereby enabling improved imaging analysis of cells and molecules of interests. The quenching effect of SB on the intrinsic fluorescence properties of silk and on commercial fluorescent dyes were first investigated in this study. SB was then incorporated into typical fluorescence-based staining protocols to study its effectiveness in improving fluorescence-based imaging of the cells and proteins residing with the silk-based biomaterials. Silk processed into various forms of biomaterials (e.g., films, sponges, fibers, and electrospun mats) was seeded with cells and cultured in vitro. At sacrificial time points, specimens were harvested, fixed, and prepared for fluorescence staining. SB, available commercially as a powder, was dissolved in 70% ethanol (0.3% [w/v]) to form staining solutions. SB treatment was introduced at the last step of typical immunofluorescence staining protocols for 15-120 min. For actin staining protocols by phalloidin toxin, SB staining solutions were added before and after permeabilization with Triton-X for 15-30 min. Results showed that ideal SB treatment duration is about 15 min. Apart from being able to suppress the autofluorescence of silk, this treatment duration was also not too long to adversely affect the fluorescent labeling probes used. The relative improvement brought about by SB treatment was most evident in the blue and green emission wavelengths compared with the red emission wavelength. This study has showed that the use of SB is a cost and time effective approach to enhance fluorescence-based imaging analyses of cell-seeded silk biomaterials, which otherwise would have been hindered by the unmodulated autofluorescence signals.

Physical characterization of functionalized spider silk: electronic and sensing properties

PubMed Central

Steven, Eden; Park, Jin Gyu; Paravastu, Anant; Lopes, Elsa Branco; Brooks, James S; Englander, Ongi; Siegrist, Theo; Kaner, Papatya; Alamo, Rufina G

2011-01-01

This work explores functional, fundamental and applied aspects of naturally harvested spider silk fibers. Natural silk is a protein polymer where different amino acids control the physical properties of fibroin bundles, producing, for example, combinations of β-sheet (crystalline) and amorphous (helical) structural regions. This complexity presents opportunities for functional modification to obtain new types of material properties. Electrical conductivity is the starting point of this investigation, where the insulating nature of neat silk under ambient conditions is described first. Modification of the conductivity by humidity, exposure to polar solvents, iodine doping, pyrolization and deposition of a thin metallic film are explored next. The conductivity increases exponentially with relative humidity and/or solvent, whereas only an incremental increase occurs after iodine doping. In contrast, iodine doping, optimal at 70 °C, has a strong effect on the morphology of silk bundles (increasing their size), on the process of pyrolization (suppressing mass loss rates) and on the resulting carbonized fiber structure (that becomes more robust against bending and strain). The effects of iodine doping and other functional parameters (vacuum and thin film coating) motivated an investigation with magic angle spinning nuclear magnetic resonance (MAS-NMR) to monitor doping-induced changes in the amino acid-protein backbone signature. MAS-NMR revealed a moderate effect of iodine on the helical and β-sheet structures, and a lesser effect of gold sputtering. The effects of iodine doping were further probed by Fourier transform infrared (FTIR) spectroscopy, revealing a partial transformation of β-sheet-to-amorphous constituency. A model is proposed, based on the findings from the MAS-NMR and FTIR, which involves iodine-induced changes in the silk fibroin bundle environment that can account for the altered physical properties. Finally, proof-of-concept applications of functionalized spider silk are presented for thermoelectric (Seebeck) effects and incandescence in iodine-doped pyrolized silk fibers, and metallic conductivity and flexibility of micron-sized gold-sputtered silk fibers. In the latter case, we demonstrate the application of gold-sputtered neat spider silk to make four-terminal, flexible, ohmic contacts to organic superconductor samples. PMID:27877440

Comparative evaluation of in vivo biocompatibility and biodegradability of regenerated silk scaffolds reinforced with/without natural silk fibers.

PubMed

Mobini, Sahba; Taghizadeh-Jahed, Masoud; Khanmohammadi, Manijeh; Moshiri, Ali; Naderi, Mohammad-Mehdi; Heidari-Vala, Hamed; Ashrafi Helan, Javad; Khanjani, Sayeh; Springer, Armin; Akhondi, Mohammad-Mehdi; Kazemnejad, Somaieh

2016-01-01

Nowadays, exceptional advantages of silk fibroin over synthetic and natural polymers have impelled the scientists to application of this biomaterial for tissue engineering purposes. Recently, we showed that embedding natural degummed silk fibers in regenerated Bombyx mori silk-based scaffold significantly increases the mechanical stiffness, while the porosity of the scaffolds remains the same. In the present study, we evaluated degradation rate, biocompatibility and regenerative properties of the regenerated 2% and 4% wt silk-based composite scaffolds with or without embedded natural degummed silk fibers within 90 days in both athymic nude and wild-type C57BL/6 mice through subcutaneous implantation. In all scaffolds, a suitable interconnected porous structure for cell penetration was seen under scanning electron microscopy. Compressive tests revealed a functional relationship between fiber reinforcement and compressive modulus. In addition, the fiber/fibroin composite scaffolds support cell attachment and proliferation. On days 30 to 90 after subcutaneous implantation, the retrieved tissues were examined via gross morphology, histopathology, immunofluorescence staining and reverse transcription-polymerase chain reaction as shown in Figure 1. Results showed that embedding the silk fibers within the matrix enhances the biodegradability of the matrix resulting in replacement of the composite scaffolds with the fresh connective tissue. Fortification of the composites with degummed fibers not only regulates the degradation profile but also increases the mechanical performance of the scaffolds. This report also confirmed that pore size and structure play an important role in the degradation rate. In conclusion, the findings of the present study narrate key role of additional surface area in improving in vitro and in vivo biological properties of the scaffolds and suggest the potential ability of these fabricated composite scaffolds for connective tissue regeneration. spjba;30/6/793/FIG10885328215601925F1fig1-0885328215601925Figure 1.Illustrative summary of the main methods and findings.RS: regenerated silk; RSF: regenerated fibroin/ silk fiber composite scaffolds; H&E: Hematoxylin and eosin; COX-1: Cyclooxygenase. © The Author(s) 2015.

Maize pollen coat xylanase facilitates pollen tube penetration into silk during sexual reproduction.

PubMed

Suen, Der Fen; Huang, Anthony H C

2007-01-05

Cell wall hydrolases are well documented to be present on pollen, but their roles on the stigma during sexual reproduction have not been previously demonstrated. We explored the function of the tapetum-synthesized xylanase, ZmXYN1, on maize (Zea mays L.) pollen. Transgenic lines (xyl-less) containing little or no xylanase in the pollen coat were generated with use of an antisense construct of the xylanase gene-coding region driven by the XYN1 gene promoter. Xyl-less and wild-type plants had similar vegetative growth. Electron microscopy revealed no appreciable morphological difference in anther cells and pollen between xyl-less lines and the wild type, whereas immunofluorescence microscopy and biochemical analyses indicated an absence of xylanase on xyl-less pollen. Xyl-less pollen germinated as efficiently as wild-type pollen in vitro in a liquid medium but less so on gel media of increasing solidity or on silk, which is indicative of partial impaired water uptake. Once germinated in vitro or on silk, the xyl-less and wild-type pollen tubes elongated at comparable rates. Tubes of germinated xyl-less pollen on silk did not penetrate into the silk as efficiently as tubes of wild-type pollen, and this lower efficiency could be overcome by the addition of xylanase to the silk. For wild-type pollen, coat xylanase activity on oat spelled xylan in vitro and tube penetration into silk were inhibited by xylose but not glucose. The overall findings indicate that maize pollen coat xylanase facilitates pollen tube penetration into silk via enzymatic xylan hydrolysis.

Combinatorial effects of charge characteristics and hydrophobicity of silk fibroin on the sorption and release of charged dyes.

PubMed

Wongpanit, Panya; Rujiravanit, Ratana

2012-01-01

The present study was designed to examine the influence of the charge characteristics of silk fibroin on the sorption and release of charged dyes by varying the pH values of the sorption and release media as well as types of charged dyes. Negatively charged dyes (phenol red and chromotrope 2R) and positively charged dyes (crystal violet and indoine blue) were used as the model compounds. Silk fibroin films were prepared by using a solution casting technique. The prepared films were then treated with an aqueous methanol solution or annealed with water to control their conformation. The sorption behavior of the model compounds made by the methanol-treated and water-annealed silk fibroin films was investigated. Compared to the water- annealed silk fibroin films, a higher hydrophobicity of the methanol-treated silk fibroin films caused a higher sorption of the hydrophobic dyes. The dye molecules had a fairly high affinity to the silk fibroin film, even though the dye and the matrix possessed the same charge. However, in the presence of two charged groups in a single dye molecule, the electrostatic repulsion become more dominant. Stronger interaction was observed when the charges of the film and the dye were opposite. The results of dye sorption and release experiments showed that the degree of synergism or competition between electrostatic and hydrophobic interactions directly depended on the charges and chemical structure of the dye molecules and the environmental pH conditions of the existing silk fibroin film.

Structural and Mechanical Properties of Cocoons of Antherina suraka (Saturniidae, Lepidoptera), an Endemic Species Used for Silk Production in Madagascar

PubMed Central

Wu, Wen-Yen; Carney, David A.; Wagoner Johnson, Amy J.; Berenbaum, May R.

2017-01-01

Antherina suraka Boisduval (Saturniidae, Lepidoptera) produces a silken cocoon that has been the focus of efforts to create a commercial wild silk industry in Madagascar. In this study, structural and mechanical properties of the cocoon of A. suraka from two sites were measured and compared to the cocoon of Bombyx mori L. (Bombycidae, Lepidoptera) the world's most common source for silk. Results of environmental scanning electron microscopy and mechanical testing showed that the silk sheet of A. suraka cocoon is less compact, with greater thickness and lower tensile strength and stiffness than that of B. mori. Confirming these results, stiffness and cell and thread density were found to be negatively correlated with thickness, and the cell and thread volumes were positively correlated with thickness. Antherina suraka showed no major differences between silk sheets from Kirindy and Isalo sites in either structural or mechanical properties, except for mean cell volume, which was greater in cocoons from Kirindy. Comparison between the two layers forming the cocoon showed that the inner layer has greater elastic modulus, denser silk distribution and lower porosity. Cocoons from both Kirindy and Isalo are suitable for sericulture. Although the inner layer of cocoon silk is of higher quality than the outer layer, the fact that both layers are of great but lower tensile strength than B. mori silk suggests that the current practice of sewing the two layers together for making one single layer fabric should be continued in efforts to produce a commercially viable product. PMID:28130459

Durable flame retardant finish for silk fabric using boron hybrid silica sol

NASA Astrophysics Data System (ADS)

Zhang, Qiang-hua; Gu, Jiali; Chen, Guo-qiang; Xing, Tie-ling

2016-11-01

A hybrid silica sol was prepared via sol gel method using tetraethoxysilane (TEOS) as a precursor and boric acid (H3BO3) as flame retardant additive and then applied to silk fabric. In order to endow silk fabric with durable flame retardancy, 1,2,3,4-butanetetracarboxylic acid (BTCA) was used as cross-linking agent for the sake of strong linkage formation between the hybrid silica sol and silk fabric. The FT-IR and XPS analysis demonstrated the Si-O-B formation in the sol system, as well as the linkage between the sol and silk after the treatment. The limiting oxygen index (LOI) and smoke density test indicated good flame retardancy and smoke suppression of the treated silk fabrics. The micro calorimeter combustion (MCC) test and thermo gravimetric (TG) analysis showed that the treated samples had less weight loss in the high temperature and lower heat release rate when burning. The washing durability evaluation results indicated that there was a distinct improvement for the silk samples treated with BTCA even after 30 times washing. In addition, the influence of the processing order of BTCA and silica sol treatment on the limiting oxygen index (LOI) of the finished silk fabric was also investigated. And the results demonstrated that the sample treated with BTCA first and then with the silica sol exhibited better LOI value (32.3%) than that of the sample by the conversed treatment order. Moreover the tensile property of treated samples was nearly unchanged, but the handle of sol treated samples obviously decreased.

Silk protein hydrolysate increases glucose uptake through up-regulation of GLUT 4 and reduces the expression of leptin in 3T3-L1 fibroblast.

PubMed

Lee, Hyun-Sun; Lee, Hyun Jung; Suh, Hyung Joo

2011-12-01

The purpose of our research was to test the hypothesis that silk protein hydrolysate increases glucose uptake in cultured murine embryonic fibroblasts. Insulin sensitizing activity was observed in a cell-based glucose uptake assay using 3T3-L1 embryonic fibroblasts. The treatment of 1 mg/mL of silk peptide E5K6 plus 0.2 nM insulin was associated with a significant increase in glucose uptake (124.0% ± 2.5%) compared to treatment with 0.2 nM insulin alone. When the 3T3-L1 cells were induced to differentiate into fibroblasts, fat droplets formed inside the cells. Silk peptide E5K6 reduced the formation of fat droplets at the 1-mg/mL dosage (86.1% ± 2.5%) when compared to the control (100.0% ± 5.8%). A 1 mg/mL dose of silk peptide E5K6 significantly increased GLUT 4 expression (131.5% ± 4.0%). The treatment of 1 mg/mL of silk peptide E5K6 did not present any changes for adipogenic expressed genes, but leptin expression was significantly increased by silk peptide E5K6 supplementation (175.9% ± 11.1%). From these results, silk peptide E5K6 increased glucose uptake via up-regulation of GLUT 4 and decreased fat accumulation via the up-regulation of leptin. Copyright © 2011 Elsevier Inc. All rights reserved.

Mechanical Properties of Robust Ultrathin Silk Fibroin Films

DTIC Science & Technology

2007-01-01

extracted from the cocoons prior to sericin removal in order to avoid contamination of the fibroin protein. Silk fibers were prepared as previously...the glue-like sericin proteins. The extracted silk fibroin was dissolved in 9.3 M LiBr solution at 60 °C for 4 h, yielding a 20 wt % solution. The

Biosynthesis and Characterization of AgNPs–Silk/PVA Film for Potential Packaging Application

PubMed Central

Tao, Gang; Cai, Rui; Wang, Yejing; Song, Kai; Guo, Pengchao; Zhao, Ping; Zuo, Hua; He, Huawei

2017-01-01

Bionanocomposite packaging materials have a bright future for a broad range of applications in the food and biomedical industries. Antimicrobial packaging is one of the bionanocomposite packaging materials. Silver nanoparticle (AgNP) is one of the most attractive antimicrobial agents for its broad spectrum of antimicrobial activity against microorganisms. However, the traditional method of preparing AgNPs-functionalized packaging material is cumbersome and not environmentally friendly. To develop an efficient and convenient biosynthesis method to prepare AgNPs-modified bionanocomposite material for packaging applications, we synthesized AgNPs in situ in a silk fibroin solution via the reduction of Ag+ by the tyrosine residue of fibroin, and then prepared AgNPs–silk/poly(vinyl alcohol) (PVA) composite film by blending with PVA. AgNPs were synthesized evenly on the surface or embedded in the interior of silk/PVA film. The prepared AgNPs–silk/PVA film exhibited excellent mechanical performance and stability, as well as good antibacterial activity against both Gram-negative and Gram-positive bacteria. AgNPs–silk/PVA film offers more choices to be potentially applied in the active packaging field. PMID:28773026

Silk: a potential medium for tissue engineering.

PubMed

Sobajo, Cassandra; Behzad, Farhad; Yuan, Xue-Feng; Bayat, Ardeshir

2008-01-01

Human skin is a complex bilayered organ that serves as a protective barrier against the environment. The loss of integrity of skin by traumatic experiences such as burns and ulcers may result in considerable disability or ultimately death. Therefore, in skin injuries, adequate dermal substitutes are among primary care targets, aimed at replacing the structural and functional properties of native skin. To date, there are very few single application tissue-engineered dermal constructs fulfilling this criterion. Silk produced by the domestic silkworm, Bombyx mori, has a long history of use in medicine. It has recently been increasingly investigated as a promising biomaterial for dermal constructs. Silk contains 2 fibrous proteins, sericin and fibroin. Each one exhibits unique mechanical and biological properties. Comprehensive review of randomized-controlled trials investigating current dermal constructs and the structures and properties of silk-based constructs on wound healing. This review revealed that silk-fibroin is regarded as the most promising biomaterial, providing options for the construction of tissue-engineered skin. The research available indicates that silk fibroin is a suitable biomaterial scaffold for the provision of adequate dermal constructs.

Biosynthesis and Characterization of AgNPs-Silk/PVA Film for Potential Packaging Application.

PubMed

Tao, Gang; Cai, Rui; Wang, Yejing; Song, Kai; Guo, Pengchao; Zhao, Ping; Zuo, Hua; He, Huawei

2017-06-17

Bionanocomposite packaging materials have a bright future for a broad range of applications in the food and biomedical industries. Antimicrobial packaging is one of the bionanocomposite packaging materials. Silver nanoparticle (AgNP) is one of the most attractive antimicrobial agents for its broad spectrum of antimicrobial activity against microorganisms. However, the traditional method of preparing AgNPs-functionalized packaging material is cumbersome and not environmentally friendly. To develop an efficient and convenient biosynthesis method to prepare AgNPs-modified bionanocomposite material for packaging applications, we synthesized AgNPs in situ in a silk fibroin solution via the reduction of Ag⁺ by the tyrosine residue of fibroin, and then prepared AgNPs-silk/poly(vinyl alcohol) (PVA) composite film by blending with PVA. AgNPs were synthesized evenly on the surface or embedded in the interior of silk/PVA film. The prepared AgNPs-silk/PVA film exhibited excellent mechanical performance and stability, as well as good antibacterial activity against both Gram-negative and Gram-positive bacteria. AgNPs-silk/PVA film offers more choices to be potentially applied in the active packaging field.

Precipitation of hydroxyapatite on electrospun polycaprolactone/aloe vera/silk fibroin nanofibrous scaffolds for bone tissue engineering.

PubMed

Shanmugavel, Suganya; Reddy, Venugopal Jayarama; Ramakrishna, Seeram; Lakshmi, B S; Dev, Vr Giri

2014-07-01

Advances in electrospun nanofibres with bioactive materials have enhanced the scope of fabricating biomimetic scaffolds for tissue engineering. The present research focuses on fabrication of polycaprolactone/aloe vera/silk fibroin nanofibrous scaffolds by electrospinning followed by hydroxyapatite deposition by calcium-phosphate dipping method for bone tissue engineering. Morphology, composition, hydrophilicity and mechanical properties of polycaprolactone/aloe vera/silk fibroin-hydroxyapatite nanofibrous scaffolds along with controls polycaprolactone and polycaprolactone/aloe vera/silk fibroin nanofibrous scaffolds were examined by field emission scanning electron microscopy, Fourier transform infrared spectroscopy, contact angle and tensile tests, respectively. Adipose-derived stem cells cultured on polycaprolactone/aloe vera/silk fibroin-hydroxyapatite nanofibrous scaffolds displayed highest cell proliferation, increased osteogenic markers expression (alkaline phosphatase and osteocalcin), osteogenic differentiation and increased mineralization in comparison with polycaprolactone control. The obtained results indicate that polycaprolactone/aloe vera/silk fibroin-hydroxyapatite nanofibrous scaffolds have appropriate physico-chemical and biological properties to be used as biomimetic scaffolds for bone tissue regeneration. © The Author(s) 2013 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

Spider web and silk performance landscapes across nutrient space

PubMed Central

Blamires, Sean J.; Tseng, Yi-Hsuan; Wu, Chung-Lin; Toft, Søren; Raubenheimer, David; Tso, I.-Min

2016-01-01

Predators have been shown to alter their foraging as a regulatory response to recent feeding history, but it remains unknown whether trap building predators modulate their traps similarly as a regulatory strategy. Here we fed the orb web spider Nephila pilipes either live crickets, dead crickets with webs stimulated by flies, or dead crickets without web stimulation, over 21 days to enforce spiders to differentially extract nutrients from a single prey source. In addition to the nutrients extracted we measured web architectures, silk tensile properties, silk amino acid compositions, and web tension after each feeding round. We then plotted web and silk “performance landscapes” across nutrient space. The landscapes had multiple peaks and troughs for each web and silk performance parameter. The findings suggest that N. pilipes plastically adjusts the chemical and physical properties of their web and silk in accordance with its nutritional history. Our study expands the application of the geometric framework foraging model to include a type of predatory trap. Whether it can be applied to other predatory traps requires further testing. PMID:27216252

KSC-06pd2059

NASA Image and Video Library

2006-09-06

KENNEDY SPACE CENTER, FLA. - Among the palmettos near a road in NASA's Kennedy Space Center, a large web supports this female Golden-silk Spider, along with the considerably smaller male in front of her (more visible in an enlargement). Golden-silk spiders build a roundish web, with an orb-shaped center like a fishnet. Like the spider, the silk is bright yellow, leading to the alternate reference of "banana spider." In Florida, a single golden-silk spider can place a web across a 12-foot wide trail overnight. It is frequently about 6 to 9 feet above the ground and normally has an area from 8 to 36 square feet. They eat almost all insects; their natural enemies are wasps. Golden-silk spiders are found in Florida to the Carolinas, the West Indies, Central and South America. Photo credit: NASA/Ken Thornsley

Hierarchical charge distribution controls self-assembly process of silk in vitro

NASA Astrophysics Data System (ADS)

Zhang, Yi; Zhang, Cencen; Liu, Lijie; Kaplan, David L.; Zhu, Hesun; Lu, Qiang

2015-12-01

Silk materials with different nanostructures have been developed without the understanding of the inherent transformation mechanism. Here we attempt to reveal the conversion road of the various nanostructures and determine the critical regulating factors. The regulating conversion processes influenced by a hierarchical charge distribution were investigated, showing different transformations between molecules, nanoparticles and nanofibers. Various repulsion and compressive forces existed among silk fibroin molecules and aggregates due to the exterior and interior distribution of charge, which further controlled their aggregating and deaggregating behaviors and finally formed nanofibers with different sizes. Synergistic action derived from molecular mobility and concentrations could also tune the assembly process and final nanostructures. It is suggested that the complicated silk fibroin assembly processes comply a same rule based on charge distribution, offering a promising way to develop silk-based materials with designed nanostructures.

Characterization of a novel glycine-rich protein from the cell wall of maize silk tissues.

PubMed

Tao, T Y; Ouellet, T; Dadej, K; Miller, S S; Johnson, D A; Singh, J

2006-08-01

The isolation, characterization and regulation of expression of a maize silk-specific gene is described. zmgrp5 (Zea mays glycine-rich protein 5) encodes a 187 amino acid glycine-rich protein that displays developmentally regulated silk-specific expression. Northern, Western, in situ mRNA hybridization and transient gene expression analyses indicate that zmgrp5 is expressed in silk hair and in cells of the vascular bundle and pollen tube transmitting tissue elements. The protein is secreted into the extracellular matrix and is localized in the cell wall fraction mainly through interactions mediated by covalent disulphide bridges. Taken together, these results suggest that the protein may play a role in maintaining silk structure during development. This is the first documented isolation of a stigma-specific gene from maize, an important agronomic member of the Poaceae family.

A simple method for orienting silk and other flexible fibres in transmission electron microscopy specimens.

PubMed

Trancik, J E; Czernuszka, J T; Merriman, C; Viney, C

2001-09-01

When microstructures are characterized by transmission electron microscopy (TEM), the interpretation of results is facilitated if the material can be sectioned in defined orientations. In the case of fibres, it is especially useful if transverse and longitudinal sections can be obtained reliably. Here we describe a procedure for orienting spider silk and other flexible fibres for TEM investigation. Prior to embedding in epoxy resin, the silk is wound around a notched support made from polyester film. No glue is required. After the silk and its supporting film have been embedded and the resin has been cured the film can be peeled away to reveal nearly perfectly orientated silk threads. Both transverse and longitudinal sections can then be cut with a microtome. The method can be extended to obtain sections at any intermediate orientation.

Modification of Silk Fibroin Using Diazonium Coupling Chemistry and the Effects on hMSC Proliferation and Differentiation

PubMed Central

Murphy, Amanda R.; John, Peter St.; Kaplan, David L.

2009-01-01

A simple chemical modification method using diazonium coupling chemistry was developed to tailor the structure and hydrophilicity of silk fibroin protein. The extent of modification using several aniline derivatives was characterized using UV/vis and 1H NMR spectroscopy, and the resulting protein structure was analyzed with ATR-FTIR spectroscopy. Introduction of hydrophobic functional groups facilitated rapid conversion of the protein from a random coil to a β-sheet structure, while addition of hydrophilic groups inhibited this process. hMSCs were grown on these modified silks to assess the biocompatibility of these materials. The hydrophilicity of the silk derivatives was found to affect the growth rate and morphology, but hMSCs were able to attach, proliferate and differentiate into an osteogenic lineage on all of the silk derivatives. PMID:18417206

Osiris9a is a major component of silk fiber in lepidopteran insects.

PubMed

Liu, Chun; Hu, Wenbo; Cheng, Tingcai; Peng, Zhangchuan; Mita, Kazuei; Xia, Qingyou

2017-10-01

In a previous high-throughput proteomics study, it was found that the silkworm cocoon contains hundreds of complex proteins, many of which have unknown functions, in addition to fibroins, sericins, and some protease inhibitors. Osiris was one of the proteins with no known function. In this study, we identified the Osiris gene family members and constructed a phylogenetic tree based on the sequences from different species. Our results indicate that the Osiris9 gene subfamily contains six members; it is specifically expressed in lepidopteran insects and has evolved by gene duplication. An Osiris gene family member from Bombyx mori was designated as BmOsiris9a (BmOsi9a) on the basis of its homology to Drosophila melanogaster Osiris9. The expression pattern of BmOsi9a showed that it was highly expressed only in the middle silk gland of silkworm larvae, similar to Sericin1 (Ser1). BmOsi9a was visualized as two bands in western blot analysis, implying that it probably undergoes post-translational modifications. Immunohistochemistry analysis revealed that BmOsi9a was synthesized and secreted into the lumen of the middle silk gland, and was localized in the sericin layer in the silk fiber. BmOsi9a was found in the silk fibers of not only three Bombycidae species, viz. B. mori, B. mandarina, and B. huttoni, but also in the fibers collected from Saturniidae species, including Antheraea assama, Antheraea mylitta, and Samia cynthia. Although the exact biological function of Osi9a in the silk fibers is unknown, our results are important because they demonstrate that Osi9a is a common structural component of silk fiber and is expressed widely among the silk-producing Bombycidae and Saturniidae insects. Our results should help in understanding the role of Osi9a in silk fibers. Copyright © 2017 Elsevier Ltd. All rights reserved.

Acellular bi-layer silk fibroin scaffolds support tissue regeneration in a rabbit model of onlay urethroplasty.

PubMed

Chung, Yeun Goo; Tu, Duong; Franck, Debra; Gil, Eun Seok; Algarrahi, Khalid; Adam, Rosalyn M; Kaplan, David L; Estrada, Carlos R; Mauney, Joshua R

2014-01-01

Acellular scaffolds derived from Bombyx mori silk fibroin were investigated for their ability to support functional tissue regeneration in a rabbit model of urethra repair. A bi-layer silk fibroin matrix was fabricated by a solvent-casting/salt leaching process in combination with silk fibroin film casting to generate porous foams buttressed by homogeneous silk fibroin films. Ventral onlay urethroplasty was performed with silk fibroin grafts (Group 1, N = 4) (Width × Length, 1 × 2 cm(2)) in adult male rabbits for 3 m of implantation. Parallel control groups consisted of animals receiving small intestinal submucosa (SIS) implants (Group 2, N = 4) or urethrotomy alone (Group 3, N = 3). Animals in all groups exhibited 100% survival prior to scheduled euthanasia and achieved voluntary voiding following 7 d of initial catheterization. Retrograde urethrography of each implant group at 3 m post-op revealed wide urethral calibers and preservation of organ continuity similar to pre-operative and urethrotomy controls with no evidence of contrast extravasation, strictures, fistulas, or stone formation. Histological (hematoxylin and eosin and Masson's trichrome), immunohistochemical, and histomorphometric analyses demonstrated that both silk fibroin and SIS scaffolds promoted similar extents of smooth muscle and epithelial tissue regeneration throughout the original defect sites with prominent contractile protein (α-smooth muscle actin and SM22α) and cytokeratin expression, respectively. De novo innervation and vascularization were also evident in all regenerated tissues indicated by synaptophysin-positive neuronal cells and vessels lined with CD31 expressing endothelial cells. Following 3 m post-op, minimal acute inflammatory reactions were elicited by silk fibroin scaffolds characterized by the presence of eosinophil granulocytes while SIS matrices promoted chronic inflammatory responses indicated by mobilization of mononuclear cell infiltrates. The results of this study demonstrate that bi-layer silk fibroin scaffolds represent promising biomaterials for onlay urethroplasty, capable of promoting similar degrees of tissue regeneration in comparison to conventional SIS scaffolds, but with reduced immunogenicity.

Acellular Bi-Layer Silk Fibroin Scaffolds Support Tissue Regeneration in a Rabbit Model of Onlay Urethroplasty

PubMed Central

Franck, Debra; Gil, Eun Seok; Algarrahi, Khalid; Adam, Rosalyn M.; Kaplan, David L.; Estrada Jr., Carlos R.; Mauney, Joshua R.

2014-01-01

Acellular scaffolds derived from Bombyx mori silk fibroin were investigated for their ability to support functional tissue regeneration in a rabbit model of urethra repair. A bi-layer silk fibroin matrix was fabricated by a solvent-casting/salt leaching process in combination with silk fibroin film casting to generate porous foams buttressed by homogeneous silk fibroin films. Ventral onlay urethroplasty was performed with silk fibroin grafts (Group 1, N = 4) (Width×Length, 1×2 cm2) in adult male rabbits for 3 m of implantation. Parallel control groups consisted of animals receiving small intestinal submucosa (SIS) implants (Group 2, N = 4) or urethrotomy alone (Group 3, N = 3). Animals in all groups exhibited 100% survival prior to scheduled euthanasia and achieved voluntary voiding following 7 d of initial catheterization. Retrograde urethrography of each implant group at 3 m post-op revealed wide urethral calibers and preservation of organ continuity similar to pre-operative and urethrotomy controls with no evidence of contrast extravasation, strictures, fistulas, or stone formation. Histological (hematoxylin and eosin and Masson's trichrome), immunohistochemical, and histomorphometric analyses demonstrated that both silk fibroin and SIS scaffolds promoted similar extents of smooth muscle and epithelial tissue regeneration throughout the original defect sites with prominent contractile protein (α-smooth muscle actin and SM22α) and cytokeratin expression, respectively. De novo innervation and vascularization were also evident in all regenerated tissues indicated by synaptophysin-positive neuronal cells and vessels lined with CD31 expressing endothelial cells. Following 3 m post-op, minimal acute inflammatory reactions were elicited by silk fibroin scaffolds characterized by the presence of eosinophil granulocytes while SIS matrices promoted chronic inflammatory responses indicated by mobilization of mononuclear cell infiltrates. The results of this study demonstrate that bi-layer silk fibroin scaffolds represent promising biomaterials for onlay urethroplasty, capable of promoting similar degrees of tissue regeneration in comparison to conventional SIS scaffolds, but with reduced immunogenicity. PMID:24632740

Comparative Study of Ultrasonication-Induced and Naturally Self-Assembled Silk Fibroin-Wool Keratin Hydrogel Biomaterials

PubMed Central

Vu, Trang; Xue, Ye; Vuong, Trinh; Erbe, Matthew; Bennet, Christopher; Palazzo, Ben; Popielski, Lucas; Rodriguez, Nelson; Hu, Xiao

2016-01-01

This study reports the formation of biocompatible hydrogels using protein polymers from natural silk cocoon fibroins and sheep wool keratins. Silk fibroin protein contains β-sheet secondary structures, allowing for the formation of physical cross-linkers in the hydrogels. Comparative studies were performed on two groups of samples. In the first group, ultrasonication was used to induce a quick gelation of a protein aqueous solution, enhancing the ability of Bombyx mori silk fibroin chains to quickly entrap the wool keratin protein molecules homogenously. In the second group, silk/keratin mixtures were left at room temperature for days, resulting in naturally-assembled gelled solutions. It was found that silk/wool blended solutions can form hydrogels at different mixing ratios, with perfectly interconnected gel structure when the wool content was less than 30 weight percent (wt %) for the first group (ultrasonication), and 10 wt % for the second group (natural gel). Differential scanning calorimetry (DSC) and temperature modulated DSC (TMDSC) were used to confirm that the fibroin/keratin hydrogel system was well-blended without phase separation. Fourier transform infrared spectroscopy (FTIR) was used to investigate the secondary structures of blended protein gels. It was found that intermolecular β-sheet contents significantly increase as the system contains more silk for both groups of samples, resulting in stable crystalline cross-linkers in the blended hydrogel structures. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to analyze the samples’ characteristic morphology on both micro- and nanoscales, which showed that ultrasonic waves can significantly enhance the cross-linker formation and avoid phase separation between silk and keratin molecules in the blended systems. With the ability to form cross-linkages non-chemically, these silk/wool hydrogels may be economically useful for various biomedical applications, thanks to the good biocompatibility of protein molecules and the various characteristics of hydrogel systems. PMID:27618011

The optical properties of regenerated silk fibroin films obtained from different sources

NASA Astrophysics Data System (ADS)

Perotto, Giovanni; Zhang, Yuji; Naskar, Deboki; Patel, Nereus; Kaplan, David L.; Kundu, Subhas C.; Omenetto, Fiorenzo G.

2017-09-01

Silk fibroin possesses unique properties for bio-functional optical interfaces and has been attracting increasing interest as an optical material. Here, we report on the refractive index and absorption coefficient of silk fibroin extracted from Bombyx mori, Antheraea mylitta, Samia ricini, and Antheraea assamensis. The influence of protein molecular weight, residual water content, and crystallinity on refractive index was investigated. The parameters for the Cauchy dispersion law and Urbach absorption were determined for each of the silk fibroins. By exploiting the differences in refractive index between the different fibroins, an all-protein slab waveguide was fabricated.

Spider silk reinforced by graphene or carbon nanotubes

NASA Astrophysics Data System (ADS)

Lepore, Emiliano; Bosia, Federico; Bonaccorso, Francesco; Bruna, Matteo; Taioli, Simone; Garberoglio, Giovanni; Ferrari, Andrea C.; Pugno, Nicola Maria

2017-09-01

Spider silk has promising mechanical properties, since it conjugates high strength (~1.5 GPa) and toughness (~150 J g-1). Here, we report the production of silk incorporating graphene and carbon nanotubes by spider spinning, after feeding spiders with the corresponding aqueous dispersions. We observe an increment of the mechanical properties with respect to pristine silk, up to a fracture strength ~5.4 GPa and a toughness modulus ~1570 J g-1. This approach could be extended to other biological systems and lead to a new class of artificially modified biological, or ‘bionic’, materials.

Gelation of Regenerated Fibroin Solution

NASA Astrophysics Data System (ADS)

Nagarkar, Shailesh; Lele, Ashish; Chassenieux, Christophe; Nicolai, Taco; Durand, Dominique

2008-07-01

Silk fibroin is a high molecular weight multiblock ampiphillic protein known for its ability to form high strength fibers. It is also biocompatible; silk sutures have been traditionally used for many centuries. Recently, there has been much interest in making silk hydrogels for applications ranging from tissue engineering to controlled delivery. Fibroin gels can be formed from aqueous solutions by changing one or more state variables such as pH, temperature and ionic strength. In this work we present our investigations on the gelation of aqueous fibroin solutions derived from Bombyx Mori silk using light scattering, confocal microscopy and rheological techniques.

Silk scaffolds in bone tissue engineering: An overview.

PubMed

Bhattacharjee, Promita; Kundu, Banani; Naskar, Deboki; Kim, Hae-Won; Maiti, Tapas K; Bhattacharya, Debasis; Kundu, Subhas C

2017-11-01

Bone tissue plays multiple roles in our day-to-day functionality. The frequency of accidental bone damage and disorder is increasing worldwide. Moreover, as the world population continues to grow, the percentage of the elderly population continues to grow, which results in an increased number of bone degenerative diseases. This increased elderly population pushes the need for artificial bone implants that specifically employ biocompatible materials. A vast body of literature is available on the use of silk in bone tissue engineering. The current work presents an overview of this literature from materials and fabrication perspective. As silk is an easy-to-process biopolymer; this allows silk-based biomaterials to be molded into diverse forms and architectures, which further affects the degradability. This makes silk-based scaffolds suitable for treating a variety of bone reconstruction and regeneration objectives. Silk surfaces offer active sites that aid the mineralization and/or bonding of bioactive molecules that facilitate bone regeneration. Silk has also been blended with a variety of polymers and minerals to enhance its advantageous properties or introduce new ones. Several successful works, both in vitro and in vivo, have been reported using silk-based scaffolds to regenerate bone tissues or other parts of the skeletal system such as cartilage and ligament. A growing trend is observed toward the use of mineralized and nanofibrous scaffolds along with the development of technology that allows to control scaffold architecture, its biodegradability and the sustained releasing property of scaffolds. Further development of silk-based scaffolds for bone tissue engineering, taking them up to and beyond the stage of human trials, is hoped to be achieved in the near future through a cross-disciplinary coalition of tissue engineers, material scientists and manufacturing engineers. The state-of-art of silk biomaterials in bone tissue engineering, covering their wide applications as cell scaffolding matrices to micro-nano carriers for delivering bone growth factors and therapeutic molecules to diseased or damaged sites to facilitate bone regeneration, is emphasized here. The review rationalizes that the choice of silk protein as a biomaterial is not only because of its natural polymeric nature, mechanical robustness, flexibility and wide range of cell compatibility but also because of its ability to template the growth of hydroxyapatite, the chief inorganic component of bone mineral matrix, resulting in improved osteointegration. The discussion extends to the role of inorganic ions such as Si and Ca as matrix components in combination with silk to influence bone regrowth. The effect of ions or growth factor-loaded vehicle incorporation into regenerative matrix, nanotopography is also considered. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Silk Fibroin Biomaterial Shows Safe and Effective Wound Healing in Animal Models and a Randomized Controlled Clinical Trial.

PubMed

Zhang, Wei; Chen, Longkun; Chen, Jialin; Wang, Lingshuang; Gui, Xuexian; Ran, Jisheng; Xu, Guowei; Zhao, Hongshi; Zeng, Mengfeng; Ji, Junfeng; Qian, Li; Zhou, Jianda; Ouyang, Hongwei; Zou, Xiaohui

2017-05-01

Due to its excellent biological and mechanical properties, silk fibroin has been intensively explored for tissue engineering and regenerative medicine applications. However, lack of translational evidence has hampered its clinical application for tissue repair. Here a silk fibroin film is developed and its translational potential is investigated for skin repair by performing comprehensive preclinical and clinical studies to fully evaluate its safety and effectiveness. The silk fibroin film fabricated using all green chemistry approaches demonstrates remarkable characteristics, including transmittance, fluid handling capacity, moisture vapor permeability, waterproofness, bacterial barrier properties, and biocompatibility. In vivo rabbit full-thickness skin defect study shows that the silk fibroin film effectively reduces the average wound healing time with better skin regeneration compared with the commercial wound dressings. Subsequent assessment in porcine model confirms its long-term safety and effectiveness for full-thickness skin defects. Finally, a randomized single-blind parallel controlled clinical trial with 71 patients shows that the silk fibroin film significantly reduces the time to wound healing and incidence of adverse events compared to commercial dressing. Therefore, the study provides systematic preclinical and clinical evidence that the silk fibroin film promotes wound healing thereby establishing a foundation towards its application for skin repair and regeneration in the clinic. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Recombinant spider silk genetically functionalized with affinity domains.

PubMed

Jansson, Ronnie; Thatikonda, Naresh; Lindberg, Diana; Rising, Anna; Johansson, Jan; Nygren, Per-Åke; Hedhammar, My

2014-05-12

Functionalization of biocompatible materials for presentation of active protein domains is an area of growing interest. Herein, we describe a strategy for functionalization of recombinant spider silk via gene fusion to affinity domains of broad biotechnological use. Four affinity domains of different origin and structure; the IgG-binding domains Z and C2, the albumin-binding domain ABD, and the biotin-binding domain M4, were all successfully produced as soluble silk fusion proteins under nondenaturing purification conditions. Silk films and fibers produced from the fusion proteins were demonstrated to be chemically and thermally stable. Still, the bioactive domains are concluded to be folded and accessible, since their respective targets could be selectively captured from complex samples, including rabbit serum and human plasma. Interestingly, materials produced from mixtures of two different silk fusion proteins displayed combined binding properties, suggesting that tailor-made materials with desired stoichiometry and surface distributions of several binding domains can be produced. Further, use of the IgG binding ability as a general mean for presentation of desired biomolecules could be demonstrated for a human vascular endothelial growth factor (hVEGF) model system, via a first capture of anti-VEGF IgG to silk containing the Z-domain, followed by incubation with hVEGF. Taken together, this study demonstrates the potential of recombinant silk, genetically functionalized with affinity domains, for construction of biomaterials capable of presentation of almost any desired biomolecule.

Comparative acoustic performance and mechanical properties of silk membranes for the repair of chronic tympanic membrane perforations.

PubMed

Allardyce, Benjamin J; Rajkhowa, Rangam; Dilley, Rodney J; Xie, Zhigang; Campbell, Luke; Keating, Adrian; Atlas, Marcus D; von Unge, Magnus; Wang, Xungai

2016-12-01

The acoustic and mechanical properties of silk membranes of different thicknesses were tested to determine their suitability as a repair material for tympanic membrane perforations. Membranes of different thickness (10-100μm) were tested to determine their frequency response and their resistance to pressure loads in a simulated ear canal model. Their mechanical rigidity to pressure loads was confirmed by tensile testing. These membranes were tested alongside animal cartilage, currently the strongest available myringoplasty graft as well as paper, which is commonly used for simpler procedures. Silk membranes showed resonant frequencies within the human hearing range and a higher vibrational amplitude than cartilage, suggesting that silk may offer good acoustic energy transfer characteristics. Silk membranes were also highly resistant to simulated pressure changes in the middle ear, suggesting they can resist retraction, a common cause of graft failure resulting from chronic negative pressures in the middle ear. Part of this strength can be explained by the substantially higher modulus of silk films compared with cartilage. This allows for the production of films that are much thinner than cartilage, with superior acoustic properties, but that still provide the same level of mechanical support as thicker cartilage. Together, these in vitro results suggest that silk membranes may provide good hearing outcomes while offering similar levels of mechanical support to the reconstructed middle ear. Copyright © 2016 Elsevier Ltd. All rights reserved.

Improving the mechanical properties of collagen-based membranes using silk fibroin for corneal tissue engineering.

PubMed

Long, Kai; Liu, Yang; Li, Weichang; Wang, Lin; Liu, Sa; Wang, Yingjun; Wang, Zhichong; Ren, Li

2015-03-01

Although collagen with outstanding biocompatibility has promising application in corneal tissue engineering, the mechanical properties of collagen-based scaffolds, especially suture retention strength, must be further improved to satisfy the requirements of clinical applications. This article describes a toughness reinforced collagen-based membrane using silk fibroin. The collagen-silk fibroin membranes based on collagen [silk fibroin (w/w) ratios of 100:5, 100:10, and 100:20] were prepared by using silk fibroin and cross-linking by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide. These membranes were analyzed by scanning electron microscopy and their optical property, and NaCl and tryptophan diffusivity had been tested. The water content was found to be dependent on the content of silk fibroin, and CS10 membrane (loading 10 wt % of silk fibroin) performed the optimal mechanical properties. Also the suture experiments have proved CS10 has high suture retention strength, which can be sutured in rabbit eyes integrally. Moreover, the composite membrane proved good biocompatibility for the proliferation of human corneal epithelial cells in vitro. Lamellar keratoplasty shows that CS10 membrane promoted complete epithelialization in 35 ± 5 days, and their transparency is restored quickly in the first month. Corneal rejection reaction, neovascularization, and keratoconus are not observed. The composite films show potential for use in the field of corneal tissue engineering. © 2014 Wiley Periodicals, Inc.

Genomic perspectives of spider silk genes through target capture sequencing: Conservation of stabilization mechanisms and homology-based structural models of spidroin terminal regions.

PubMed

Collin, Matthew A; Clarke, Thomas H; Ayoub, Nadia A; Hayashi, Cheryl Y

2018-07-01

A powerful system for studying protein aggregation, particularly rapid self-assembly, is spider silk. Spider silks are proteinaceous and silk proteins are synthesized and stored within silk glands as liquid dope. As needed, liquid dope is near-instantaneously transformed into solid fibers or viscous adhesives. The dominant constituents of silks are spidroins (spider fibroins) and their terminal domains are vital for the tight control of silk self-assembly. To better understand spidroin termini, we used target capture and deep sequencing to identify spidroin gene sequences from six species representing the araneoid families of Araneidae, Nephilidae, and Theridiidae. We obtained 145 terminal regions, of which 103 are newly annotated here, as well as novel variants within nine diverse spidroin types. Our comparative analyses demonstrated the conservation of acidic, basic, and cysteine amino acid residues across spidroin types that had been proposed to be important for monomer stability, dimer formation, and self-assembly from a limited sampling of spidroins. Computational, protein homology modeling revealed areas of spidroin terminal regions that are highly conserved in three-dimensions despite sequence divergence across spidroin types. Analyses of our dense sampling of terminal regions suggest that most spidroins share stabilization mechanisms, dimer formation, and tertiary structure, despite producing functionally distinct materials. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

Silk flame retardant finish by ternary silica sol containing boron and nitrogen

NASA Astrophysics Data System (ADS)

Zhang, Qiang-hua; Chen, Guo-qiang; Xing, Tie-ling

2017-11-01

A ternary flame retardant sol system containing Si, B and N was prepared via sol gel method using tetraethoxysilane (TEOS) as a precursor, boric acid (H3BO3) and urea (CO(NH2)2) as flame retardant additives and then applied to silk fabric flame retardant finish. The FT-IR and SEM results showed that the nitrogen-boron-silica ternary sol was successfully prepared and entrapped onto the surface of silk fibers. The limiting oxygen index (LOI) test indicated that the silk fabric treated with 24% boric acid and 6% urea (relative to the TEOS) doped ternary silica sol system performed excellent flame retardancy with the LOI value of 34.6%. Furthermore, in order to endow silk fabric with durable flame retardancy, the silk fabric was pretreated with 1,2,3,4-butanetetracarboxylic acid (BTCA) before the ternary sol system treatment. The BTCA pretreat ment applied to silk could effectively promote the washing durability of the ternary sol, and the LOI value of the treated sample after 10 times washing could still maintain at 30.8% compared with that of 31.0% before washing. Thermo gravimetric (TG), micro calorimeter combustion (MCC) and smoke density test results demonstrated that the thermal stability, heat release and smoke suppression of the nitrogen-boron-silica ternary system decreased somewhat compared with the boron-silica binary flame retardant system.

Geographic Perspectives with Elementary Students: The Silk Road

ERIC Educational Resources Information Center

Bisland, Beverly Milner

2006-01-01

The purpose of this study is to investigate elementary students' explanations of how physical features of the land influence the location of humanly defined structures including trade routes, such as the silk routes. The silk routes were a series of caravan trade routes that extended from Turkey to China and were located as far south as India and…

Chemical Communications

DTIC Science & Technology

2012-10-26

the need for alignment. We have also demonstrated the use of this technique with various materials as masks for silk biopolymer RIE processing and a...project. The automatization of silk solution was developed. Examination of different processing conditions for the raw material showed promise for...higher durability and higher flexibility optical substrates. Progress on interfaces was solidified. The previous findings on silk -metal interfaces

Alliance for NanoHealth Competitive Research Program

DTIC Science & Technology

2009-10-28

25-35 Guided Microvasculature Formation and Cellular Infiltration for Tissue Regeneration Applications in Nano-Structured Silk ...V, Davis G, Gordon A, Altman A, Reece G, Gascoyne P, Mathur AB, Endothelial and Stem Cell Interactions on Dielectrophoretically Aligned Fibrous Silk ...Interactions on Dielectrophoretically Aligned Fibrous Silk Fibroin-­‐Chitosan Scaffolds, Journal of Biomedical Materials Research, Accepted October

Integration of Natural Polymers and Synthetic Nanostructures

DTIC Science & Technology

2014-11-20

interphase reinforcement. Reconstituted silk fibroin from Bombyx Mori silkworm silks is an mass- production available source of the excellent biopolymeric ...we replaced traditional synthetic binders in GO papers with universal biopolymer “binder”-silk fibroin. The fabrication of GO-SF microfilms using ...selectively patterning its secondary structure using capillary transfer lithography (CTL) and solvent-assisted micro -contact molding (SAMIM) (Figure

Sequence-structure correlations in silk: Poly-Ala repeat of N. clavipes MaSp1 is naturally optimized at a critical length scale.

PubMed

Bratzel, Graham; Buehler, Markus J

2012-03-01

Spider silk is a self-assembling biopolymer that outperforms many known materials in terms of its mechanical performance despite being constructed from simple and inferior building blocks. While experimental studies have shown that the molecular structure of silk has a direct influence on the stiffness, toughness, and failure strength of silk, few molecular-level analyses of the nanostructure of silk assemblies in particular under variations of genetic sequences have been reported. Here we report atomistic-level structures of the MaSp1 protein from the Nephila Clavipes spider dragline silk sequence, obtained using an in silico approach based on replica exchange molecular dynamics (REMD) and explicit water molecular dynamics. We apply this method to study the effects of a systematic variation of the poly-alanine repeat lengths, a parameter controlled by the genetic makeup of silk, on the resulting molecular structure of silk at the nanoscale. Confirming earlier experimental and computational work, a structural analysis reveals that poly-alanine regions in silk predominantly form distinct and orderly β-sheet crystal domains while disorderly regions are formed by glycine-rich repeats that consist of 3(10)-helix type structures and β-turns. Our predictions are directly validated against experimental data based on dihedral angle pair calculations presented in Ramachandran plots combined with an analysis of the secondary structure content. The key result of our study is our finding of a strong dependence of the resulting silk nanostructure depending on the poly-alanine length. We observe that the wildtype poly-alanine repeat length of six residues defines a critical minimum length that consistently results in clearly defined β-sheet nanocrystals. For poly-alanine lengths below six, the β-sheet nanocrystals are not well-defined or not visible at all, while for poly-alanine lengths at and above six, the characteristic nanocomposite structure of silk emerges with no significant improvement of the quality of the β-sheet nanocrystal geometry. We present a simple biophysical model that explains these computational observations based on the mechanistic insight gained from the molecular simulations. Our findings set the stage for understanding how variations in the spidroin sequence can be used to engineer the structure and thereby functional properties of this biological superfiber, and present a design strategy for the genetic optimization of spidroins for enhanced mechanical properties. The approach used here may also find application in the design of other self-assembled molecular structures and fibers and in particular biologically inspired or completely synthetic systems. Copyright © 2011 Elsevier Ltd. All rights reserved.

'Silk Road', the virtual drug marketplace: a single case study of user experiences.

PubMed

Van Hout, Marie Claire; Bingham, Tim

2013-09-01

The online promotion of 'drug shopping' and user information networks is of increasing public health and law enforcement concern. An online drug marketplace called 'Silk Road' has been operating on the 'Deep Web' since February 2011 and was designed to revolutionise contemporary drug consumerism. A single case study approach explored a 'Silk Road' user's motives for online drug purchasing, experiences of accessing and using the website, drug information sourcing, decision making and purchasing, outcomes and settings for use, and perspectives around security. The participant was recruited following a lengthy relationship building phase on the 'Silk Road' chat forum. The male participant described his motives, experiences of purchasing processes and drugs used from 'Silk Road'. Consumer experiences on 'Silk Road' were described as 'euphoric' due to the wide choice of drugs available, relatively easy once navigating the Tor Browser (encryption software) and using 'Bitcoins' for transactions, and perceived as safer than negotiating illicit drug markets. Online researching of drug outcomes, particularly for new psychoactive substances was reported. Relationships between vendors and consumers were described as based on cyber levels of trust and professionalism, and supported by 'stealth modes', user feedback and resolution modes. The reality of his drug use was described as covert and solitary with psychonautic characteristics, which contrasted with his membership, participation and feelings of safety within the 'Silk Road' community. 'Silk Road' as online drug marketplace presents an interesting displacement away from 'traditional' online and street sources of drug supply. Member support and harm reduction ethos within this virtual community maximises consumer decision-making and positive drug experiences, and minimises potential harms and consumer perceived risks. Future research is necessary to explore experiences and backgrounds of other users. Copyright © 2013 Elsevier B.V. All rights reserved.

Molecular mechanisms of phoxim-induced silk gland damage and TiO2 nanoparticle-attenuated damage in Bombyx mori.

PubMed

Li, Bing; Yu, Xiaohong; Gui, Suxin; Xie, Yi; Zhao, Xiaoyang; Hong, Jie; Sun, Qingqing; Sang, Xuezi; Sheng, Lei; Cheng, Zhe; Cheng, Jie; Hu, Rengping; Wang, Ling; Shen, Weide; Hong, Fashui

2014-06-01

Phoxim is a useful organophosphate (OP) pesticide used in agriculture in China, however, exposure to this pesticide can result in a significant reduction in cocooning in Bombyx mori (B. mori). Titanium dioxide nanoparticles (TiO2 NPs) have been shown to decrease phoxim-induced toxicity in B. mori; however, very little is known about the molecular mechanisms of silk gland damage due to OP exposure and repair of gland damage by TiO2 NP pretreatment. In the present study, exposure to phoxim resulted in a significant reduction in cocooning rate in addition to silk gland damage, whereas TiO2 NP attenuated phoxim-induced gland damage, increased the antioxidant capacity of the gland, and increased cocooning rate in B. mori. Furthermore, digital gene expression data suggested that phoxim exposure led to significant alterations in the expression of 833 genes. In particular, phoxim exposure caused significant down-regulation of Fib-L, Ser2, Ser3, and P25 genes involved in silk protein synthesis, and up-regulation of SFGH, UCH3, and Salhh genes involved in silk protein hydrolysis. A combination of both phoxim and TiO2 NP treatment resulted in marked changes in the expression of 754 genes, while treatment with TiO2 NPs led to significant alterations in the expression of 308 genes. Importantly, pretreatment with TiO2 NPs increased Fib-L, Ser2, Ser3, and P25 expression, and decreased SFGH, UCH3, and Salhh expression in silk protein in the silk gland under phoxim stress. Therefore, Fib-L, Ser2, Ser3, P25, SFGH, UCH3, and Salhh may be potential biomarkers of silk gland toxicity in B. mori caused by phoxim exposure. Copyright © 2013 Elsevier Ltd. All rights reserved.

Biomimetic Nucleation of Hydroxyapatite Crystals Mediated by Antheraea pernyi Silk Sericin Promotes Osteogenic Differentiation of Human Bone Marrow Derived Mesenchymal Stem Cells

PubMed Central

2015-01-01

Biomacromolecules have been used as templates to grow hydroxyapatite crystals (HAps) by biomineralization to fabricate mineralized materials for potential application in bone tissue engineering. Silk sericin is a protein with features desirable as a biomaterial, such as increased hydrophilicity and biodegradation. Mineralization of the silk sericin from Antheraea pernyi (A. pernyi) silkworm has rarely been reported. Here, for the first time, nucleation of HAps on A. pernyi silk sericin (AS) was attempted through a wet precipitation method and consequently the cell viability and osteogenic differentiation of BMSCs on mineralized AS were investigated. It was found that AS mediated the nucleation of HAps in the form of nanoneedles while self-assembling into β-sheet conformation, leading to the formation of a biomineralized protein based biomaterial. The cell viability assay of BMSCs showed that the mineralization of AS stimulated cell adhesion and proliferation, showing that the resultant AS biomaterial is biocompatible. The differentiation assay confirmed that the mineralized AS significantly promoted the osteogenic differentiation of BMSCs when compared to nonmineralized AS as well as other types of sericin (B. mori sericin), suggesting that the resultant mineralized AS biomaterial has potential in promoting bone formation. This result represented the first work proving the osteogenic differentiation of BMSCs directed by silk sericin. Therefore, the biomineralization of A. pernyi silk sericin coupled with seeding BMSCs on the resultant mineralized biomaterials is a useful strategy to develop the potential application of this unexplored silk sericin in the field of bone tissue engineering. This study lays the foundation for the use of A. pernyi silk sericin as a potential scaffold for tissue engineering. PMID:24666022

Clinical potential of a silk sericin-releasing bioactive wound dressing for the treatment of split-thickness skin graft donor sites.

PubMed

Siritientong, Tippawan; Angspatt, Apichai; Ratanavaraporn, Juthamas; Aramwit, Pornanong

2014-01-01

An ethyl alcohol-precipitated silk sericin/PVA scaffold that controlled the release of silk sericin was previously developed and applied for the treatment of full-thickness wounds in rats and demonstrated efficient healing. In this study, we aimed to further evaluate the clinical potential of this scaffold, hereafter called "silk sericin-releasing wound dressing", for the treatment of split-thickness skin graft donor sites by comparison with the clinically available wound dressing known as "Bactigras®". In vitro characterization and in vivo evaluation for safety of the wound dressings were performed. A clinical trial of the wound dressings was conducted according to standard protocols. The sericin released from the wound dressing was not toxic to HaCat human keratinocytes. A peel test indicated that the silk sericin-releasing wound dressing was less adhesive than Bactigras®, potentially reducing trauma and the risk of repeated injury upon removal. There was no evidence of skin irritation upon treatment with either wound dressing. When tested in patients with split-thickness skin graft donor sites, the wounds treated with the silk sericin-releasing wound dressing exhibited complete healing at 12 ± 5.0 days, whereas those treated with Bactigras® were completely healed at 14 ± 5.2 days (p = 1.99 × 10(-4)). In addition, treatment with the silk sericin-releasing wound dressing significantly reduced pain compared with Bactigras® particularly during the first 4 postoperative days (p = 2.70 × 10(-5) on day 1). We introduce this novel silk sericin-releasing wound dressing as an alternative treatment for split-thickness skin graft donor sites.

Biomimetic nucleation of hydroxyapatite crystals mediated by Antheraea pernyi silk sericin promotes osteogenic differentiation of human bone marrow derived mesenchymal stem cells.

PubMed

Yang, Mingying; Shuai, Yajun; Zhang, Can; Chen, Yuyin; Zhu, Liangjun; Mao, Chuanbin; OuYang, Hongwei

2014-04-14

Biomacromolecules have been used as templates to grow hydroxyapatite crystals (HAps) by biomineralization to fabricate mineralized materials for potential application in bone tissue engineering. Silk sericin is a protein with features desirable as a biomaterial, such as increased hydrophilicity and biodegradation. Mineralization of the silk sericin from Antheraea pernyi (A. pernyi) silkworm has rarely been reported. Here, for the first time, nucleation of HAps on A. pernyi silk sericin (AS) was attempted through a wet precipitation method and consequently the cell viability and osteogenic differentiation of BMSCs on mineralized AS were investigated. It was found that AS mediated the nucleation of HAps in the form of nanoneedles while self-assembling into β-sheet conformation, leading to the formation of a biomineralized protein based biomaterial. The cell viability assay of BMSCs showed that the mineralization of AS stimulated cell adhesion and proliferation, showing that the resultant AS biomaterial is biocompatible. The differentiation assay confirmed that the mineralized AS significantly promoted the osteogenic differentiation of BMSCs when compared to nonmineralized AS as well as other types of sericin (B. mori sericin), suggesting that the resultant mineralized AS biomaterial has potential in promoting bone formation. This result represented the first work proving the osteogenic differentiation of BMSCs directed by silk sericin. Therefore, the biomineralization of A. pernyi silk sericin coupled with seeding BMSCs on the resultant mineralized biomaterials is a useful strategy to develop the potential application of this unexplored silk sericin in the field of bone tissue engineering. This study lays the foundation for the use of A. pernyi silk sericin as a potential scaffold for tissue engineering.

Corn silk aqueous extracts and intraocular pressure of systemic and non-systemic hypertensive subjects.

PubMed

George, Gladys O; Idu, Faustina K

2015-03-01

Hypotensive properties have been attributed to the stigma/style of Zea mays L (corn silk). Although the effect of corn silk extract on blood pressure has been documented in animal studies, we are not aware of any study on its effect on human blood pressure and intraocular pressure. A randomised study was carried out on the effect of water only, masked doses of corn silk aqueous extract (60, 130, 192.5 and 260 mg/kg body weight) on intraocular pressure and blood pressure of 20 systemic and 20 non-systemic hypertensive subjects. Intraocular pressure and blood pressure were measured at baseline and every hour for eight hours after administering water or a masked dose of corn silk aqueous extract. Each dose was administered at two-week intervals to each subject in the two study groups. The results showed that the last three doses of corn silk aqueous extract gave a statistically significant reduction (p < 0.001) in mean intraocular pressure and blood pressure within eight hours of administration. The peak effect on intraocular pressure was observed after four hours and this was preceded by the peak effect on blood pressure, which occurred after three hours of administration. The hypotensive effect was dose-dependent in the two groups. Corn silk aqueous extract has a lowering effect on intraocular pressure in systemic and non-systemic hypertensive subjects. This may have resulted from the fall in blood pressure that is due to potassium-induced natriuresis and diuresis caused by the high potassium content in the high doses of the corn silk extract. © 2015 The Authors. Clinical and Experimental Optometry © 2015 Optometry Australia.

Corn Silk Extract and Its Bioactive Peptide Ameliorated Lipopolysaccharide-Induced Inflammation in Mice via the Nuclear Factor-κB Signaling Pathway.

PubMed

Ho, Tin-Yun; Li, Chia-Cheng; Lo, Hsin-Yi; Chen, Feng-Yuan; Hsiang, Chien-Yun

2017-02-01

Bioactive peptides derived from foods have shown beneficial anti-inflammatory potential. Inhibitory κB kinase-β (IKKβ) plays a crucial role in the activation of nuclear factor-κB (NF-κB), a transcription factor involved in inflammation. Here we applied proteomic and bioinformatics approaches to identify anti-inflammatory peptides that target IKKβ from corn silk. Corn silk extract significantly suppressed lipopolysaccharide (LPS)-induced NF-κB activities [(1.7 ± 0.2)-fold vs (3.0 ± 0.6)-fold, p < 0.05] in cells. Trypsin hydrolysate of corn silk also suppressed LPS-induced NF-κB activities [(1.1 ± 0.3)-fold vs 3.3 ± 0.5 fold, p < 0.01]. In addition, both corn silk extract and trypsin hydrolysate significantly inhibited LPS-induced interleukin-1β (IL-1β) production by 58.3 ± 4.5 and 55.1 ± 7.4%, respectively. A novel peptide, FK2, docked into the ATP-binding pocket of IKKβ, was further identified from trypsin hydrolysis of corn silk. FK2 inhibited IKKβ activities, IκB phosphorylation, and subsequent NF-κB activation [(2.3 ± 0.4)-fold vs (5.5 ± 0.4)-fold, p < 0.001]. Moreover, FK2 significantly reduced NF-κB-driven luminescent signals in organs by 5-11-fold and suppressed LPS-induced NF-κB activities and IL-β production in tissues. In conclusion, our findings indicated that corn silk displayed anti-inflammatory abilities. In addition, we first identified an anti-inflammatory peptide FK2 from corn silk. Moreover, the anti-inflammatory effect of FK2 might be through IKKβ-NF-κB signaling pathways.

Molecular mechanics of silk nanostructures under varied mechanical loading.

PubMed

Bratzel, Graham; Buehler, Markus J

2012-06-01

Spider dragline silk is a self-assembling tunable protein composite fiber that rivals many engineering fibers in tensile strength, extensibility, and toughness, making it one of the most versatile biocompatible materials and most inviting for synthetic mimicry. While experimental studies have shown that the peptide sequence and molecular structure of silk have a direct influence on the stiffness, toughness, and failure strength of silk, few molecular-level analyses of the nanostructure of silk assemblies, in particular, under variations of genetic sequences have been reported. In this study, atomistic-level structures of wildtype as well as modified MaSp1 protein from the Nephila clavipes spider dragline silk sequences, obtained using an in silico approach based on replica exchange molecular dynamics and explicit water molecular dynamics, are subjected to simulated nanomechanical testing using different force-control loading conditions including stretch, pull-out, and peel. The authors have explored the effects of the poly-alanine length of the N. clavipes MaSp1 peptide sequence and identify differences in nanomechanical loading conditions on the behavior of a unit cell of 15 strands with 840-990 total residues used to represent a cross-linking β-sheet crystal node in the network within a fibril of the dragline silk thread. The specific loading condition used, representing concepts derived from the protein network connectivity at larger scales, have a significant effect on the mechanical behavior. Our analysis incorporates stretching, pull-out, and peel testing to connect biochemical features to mechanical behavior. The method used in this study could find broad applications in de novo design of silk-like tunable materials for an array of applications. Copyright © 2011 Wiley Periodicals, Inc.

Structural and Mechanical Properties of Cocoons of Antherina suraka (Saturniidae, Lepidoptera), an Endemic Species Used for Silk Production in Madagascar.

PubMed

Randrianandrasana, Maminirina; Wu, Wen-Yen; Carney, David A; Wagoner Johnson, Amy J; Berenbaum, May R

2017-01-01

Antherina suraka Boisduval (Saturniidae, Lepidoptera) produces a silken cocoon that has been the focus of efforts to create a commercial wild silk industry in Madagascar. In this study, structural and mechanical properties of the cocoon of A. suraka from two sites were measured and compared to the cocoon of Bombyx mori L. (Bombycidae, Lepidoptera) the world's most common source for silk. Results of environmental scanning electron microscopy and mechanical testing showed that the silk sheet of A. suraka cocoon is less compact, with greater thickness and lower tensile strength and stiffness than that of B. mori Confirming these results, stiffness and cell and thread density were found to be negatively correlated with thickness, and the cell and thread volumes were positively correlated with thickness. Antherina suraka showed no major differences between silk sheets from Kirindy and Isalo sites in either structural or mechanical properties, except for mean cell volume, which was greater in cocoons from Kirindy. Comparison between the two layers forming the cocoon showed that the inner layer has greater elastic modulus, denser silk distribution and lower porosity. Cocoons from both Kirindy and Isalo are suitable for sericulture. Although the inner layer of cocoon silk is of higher quality than the outer layer, the fact that both layers are of great but lower tensile strength than B. mori silk suggests that the current practice of sewing the two layers together for making one single layer fabric should be continued in efforts to produce a commercially viable product. © The Author 2017. Published by Oxford University Press on behalf of the Entomological Society of America.

'Surfing the Silk Road': a study of users' experiences.

PubMed

Van Hout, Marie Claire; Bingham, Tim

2013-11-01

The online drug marketplace called 'Silk Road' has operated anonymously on the 'Deep Web' since 2011. It is accessible through computer encrypting software (Tor) and is supported by online transactions using peer to peer anonymous and untraceable crypto-currency (Bit Coins). The study aimed to describe user motives and realities of accessing, navigating and purchasing on the 'Silk Road' marketplace. Systematic online observations, monitoring of discussion threads on the site during four months of fieldwork and analysis of anonymous online interviews (n=20) with a convenience sample of adult 'Silk Road' users was conducted. The majority of participants were male, in professional employment or in tertiary education. Drug trajectories ranged from 18 months to 25 years, with favourite drugs including MDMA, 2C-B, mephedrone, nitrous oxide, ketamine, cannabis and cocaine. Few reported prior experience of online drug sourcing. Reasons for utilizing 'Silk Road' included curiosity, concerns for street drug quality and personal safety, variety of products, anonymous transactioning, and ease of product delivery. Vendor selection appeared to be based on trust, speed of transaction, stealth modes and quality of product. Forums on the site provided user advice, trip reports, product and transaction reviews. Some users reported solitary drug use for psychonautic and introspective purposes. A minority reported customs seizures, and in general a displacement away from traditional drug sourcing (street and closed markets) was described. Several reported intentions to commence vending on the site. The study provides an insight into 'Silk Road' purchasing motives and processes, the interplay between traditional and 'Silk Road' drug markets, the 'Silk Road' online community and its communication networks. Copyright © 2013 Elsevier B.V. All rights reserved.

Preparation of collagen/polyurethane/knitted silk as a composite scaffold for tendon tissue engineering.

PubMed

Sharifi-Aghdam, Maryam; Faridi-Majidi, Reza; Derakhshan, Mohammad Ali; Chegeni, Arash; Azami, Mahmoud

2017-07-01

The main objective of this study was to prepare a hybrid three-dimensional scaffold that mimics natural tendon tissues. It has been found that a knitted silk shows good mechanical strength; however, cell growth on the bare silk is not desirable. Hence, electrospun collagen/polyurethane combination was used to cover knitted silk. A series of collagen and polyurethane solutions (4%-7% w/v) in aqueous acetic acid were prepared and electrospun. According to obtained scanning electron microscopy images from pure collagen and polyurethane nanofibers, concentration was set constant at 5% (w/v) for blend solutions of collagen/polyurethane. Afterward, blend solutions with the weight ratios of 75/25, 50/50 and 25/75 were electrospun. Scanning electron microscopy images demonstrated the smooth and uniform morphology for the optimized nanofibers. The least fibers diameter among three weight ratios was found for collagen/polyurethane (25/75) which was 100.86 ± 40 nm and therefore was selected to be electrospun on the knitted silk. Attenuated total reflectance-Fourier transform infrared spectra confirmed the chemical composition of obtained electrospun nanofibers on the knitted silk. Tensile test of the specimens including blend nanofiber, knitted silk and commercial tendon substitute examined and indicated that collagen/polyurethane-coated knitted silk has appropriate mechanical properties as a scaffold for tendon tissue engineering. Then, Alamar Blue assay of the L929 fibroblast cell line seeded on the prepared scaffolds demonstrated appropriate viability of the cells with a significant proliferation on the scaffold containing more collagen content. The results illustrate that the designed structure would be promising for being used as a temporary substitute for tendon repair.

Basic Helix-Loop-Helix Transcription Factor Bmsage Is Involved in Regulation of fibroin H-chain Gene via Interaction with SGF1 in Bombyx mori

PubMed Central

Li, Qiong-Yan; Hu, Wen-Bo; Zhou, Meng-Ting; Nie, Hong-Yi; Zhang, Yin-Xia; Peng, Zhang-Chuan; Zhao, Ping; Xia, Qing-You

2014-01-01

Silk glands are specialized in the synthesis of several secretory proteins. Expression of genes encoding the silk proteins in Bombyx mori silk glands with strict territorial and developmental specificities is regulated by many transcription factors. In this study, we have characterized B. mori sage, which is closely related to sage in the fruitfly Drosophila melanogaster. It is termed Bmsage; it encodes transcription factor Bmsage, which belongs to the Mesp subfamily, containing a basic helix–loop–helix motif. Bmsage transcripts were detected specifically in the silk glands of B. mori larvae through RT-PCR analysis. Immunoblotting analysis confirmed the Bmsage protein existed exclusively in B. mori middle and posterior silk gland cells. Bmsage has a low level of expression in the 4th instar molting stages, which increases gradually in the 5th instar feeding stages and then declines from the wandering to the pupation stages. Quantitative PCR analysis suggested the expression level of Bmsage in a high silk strain was higher compared to a lower silk strain on day 3 of the larval 5th instar. Furthermore, far western blotting and co-immunoprecipitation assays showed the Bmsage protein interacted with the fork head transcription factor silk gland factor 1 (SGF1). An electrophoretic mobility shift assay showed the complex of Bmsage and SGF1 proteins bound to the A and B elements in the promoter of fibroin H-chain gene(fib-H), respectively. Luciferase reporter gene assays confirmed the complex of Bmsage and SGF1 proteins increased the expression of fib-H. Together, these results suggest Bmsage is involved in the regulation of the expression of fib-H by being together with SGF1 in B. mori PSG cells. PMID:24740008

Correlation between fibroin amino acid sequence and physical silk properties.

PubMed

Fedic, Robert; Zurovec, Michal; Sehnal, Frantisek

2003-09-12

The fiber properties of lepidopteran silk depend on the amino acid repeats that interact during H-fibroin polymerization. The aim of our research was to relate repeat composition to insect biology and fiber strength. Representative regions of the H-fibroin genes were sequenced and analyzed in three pyralid species: wax moth (Galleria mellonella), European flour moth (Ephestia kuehniella), and Indian meal moth (Plodia interpunctella). The amino acid repeats are species-specific, evidently a diversification of an ancestral region of 43 residues, and include three types of regularly dispersed motifs: modifications of GSSAASAA sequence, stretches of tripeptides GXZ where X and Z represent bulky residues, and sequences similar to PVIVIEE. No concatenations of GX dipeptide or alanine, which are typical for Bombyx silkworms and Antheraea silk moths, respectively, were found. Despite different repeat structure, the silks of G. mellonella and E. kuehniella exhibit similar tensile strength as the Bombyx and Antheraea silks. We suggest that in these latter two species, variations in the repeat length obstruct repeat alignment, but sufficiently long stretches of iterated residues get superposed to interact. In the pyralid H-fibroins, interactions of the widely separated and diverse motifs depend on the precision of repeat matching; silk is strong in G. mellonella and E. kuehniella, with 2-3 types of long homogeneous repeats, and nearly 10 times weaker in P. interpunctella, with seven types of shorter erratic repeats. The high proportion of large amino acids in the H-fibroin of pyralids has probably evolved in connection with the spinning habit of caterpillars that live in protective silk tubes and spin continuously, enlarging the tubes on one end and partly devouring the other one. The silk serves as a depot of energetically rich and essential amino acids that may be scarce in the diet.

Synthetic spider silk production on a laboratory scale.

PubMed

Hsia, Yang; Gnesa, Eric; Pacheco, Ryan; Kohler, Kristin; Jeffery, Felicia; Vierra, Craig

2012-07-18

As society progresses and resources become scarcer, it is becoming increasingly important to cultivate new technologies that engineer next generation biomaterials with high performance properties. The development of these new structural materials must be rapid, cost-efficient and involve processing methodologies and products that are environmentally friendly and sustainable. Spiders spin a multitude of different fiber types with diverse mechanical properties, offering a rich source of next generation engineering materials for biomimicry that rival the best manmade and natural materials. Since the collection of large quantities of natural spider silk is impractical, synthetic silk production has the ability to provide scientists with access to an unlimited supply of threads. Therefore, if the spinning process can be streamlined and perfected, artificial spider fibers have the potential use for a broad range of applications ranging from body armor, surgical sutures, ropes and cables, tires, strings for musical instruments, and composites for aviation and aerospace technology. In order to advance the synthetic silk production process and to yield fibers that display low variance in their material properties from spin to spin, we developed a wet-spinning protocol that integrates expression of recombinant spider silk proteins in bacteria, purification and concentration of the proteins, followed by fiber extrusion and a mechanical post-spin treatment. This is the first visual representation that reveals a step-by-step process to spin and analyze artificial silk fibers on a laboratory scale. It also provides details to minimize the introduction of variability among fibers spun from the same spinning dope. Collectively, these methods will propel the process of artificial silk production, leading to higher quality fibers that surpass natural spider silks.

Synthetic Spider Silk Production on a Laboratory Scale

PubMed Central

Hsia, Yang; Gnesa, Eric; Pacheco, Ryan; Kohler, Kristin; Jeffery, Felicia; Vierra, Craig

2012-01-01

As society progresses and resources become scarcer, it is becoming increasingly important to cultivate new technologies that engineer next generation biomaterials with high performance properties. The development of these new structural materials must be rapid, cost-efficient and involve processing methodologies and products that are environmentally friendly and sustainable. Spiders spin a multitude of different fiber types with diverse mechanical properties, offering a rich source of next generation engineering materials for biomimicry that rival the best manmade and natural materials. Since the collection of large quantities of natural spider silk is impractical, synthetic silk production has the ability to provide scientists with access to an unlimited supply of threads. Therefore, if the spinning process can be streamlined and perfected, artificial spider fibers have the potential use for a broad range of applications ranging from body armor, surgical sutures, ropes and cables, tires, strings for musical instruments, and composites for aviation and aerospace technology. In order to advance the synthetic silk production process and to yield fibers that display low variance in their material properties from spin to spin, we developed a wet-spinning protocol that integrates expression of recombinant spider silk proteins in bacteria, purification and concentration of the proteins, followed by fiber extrusion and a mechanical post-spin treatment. This is the first visual representation that reveals a step-by-step process to spin and analyze artificial silk fibers on a laboratory scale. It also provides details to minimize the introduction of variability among fibers spun from the same spinning dope. Collectively, these methods will propel the process of artificial silk production, leading to higher quality fibers that surpass natural spider silks. PMID:22847722

Effect of silk sericin on morphology and structure of calcium carbonate crystal

NASA Astrophysics Data System (ADS)

Zhao, Rui-Bo; Han, Hua-Feng; Ding, Shao; Li, Ze-Hao; Kong, Xiang-Dong

2013-06-01

In this paper, silk sericin was employed to regulate the mineralization of calcium carbonate (CaCO3). CaCO3 composite particles were prepared by the precipitation reaction of sodium carbonate with calcium chloride solution in the presence of silk sericin. The as-prepared samples were collected at different reaction time to study the crystallization process of CaCO3 by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and X-ray diffraction (XRD). The results showed that silk sericin significantly affected the morphology and crystallographic polymorph of CaCO3. With increasing the reaction time, the crystal phase of CaCO3 transferred from calcite dominated to vaterite dominated mixtures, while the morphology of CaCO3 changed from disk-like calcite crystal to spherical vaterite crystal. These studies showed the potential of silk sericin used as a template molecule to control the growth of inorganic crystal.

Silk-polypyrrole biocompatible actuator performance under biologically relevant conditions

NASA Astrophysics Data System (ADS)

Hagler, Jo'elen; Peterson, Ben; Murphy, Amanda; Leger, Janelle

Biocompatible actuators that are capable of controlled movement and can function under biologically relevant conditions are of significant interest in biomedical fields. Previously, we have demonstrated that a composite material of silk biopolymer and the conducting polymer polypyrrole (PPy) can be formed into a bilayer device that can bend under applied voltage. Further, these silk-PPy composites can generate forces comparable to human muscle (>0.1 MPa) making them ideal candidates for interfacing with biological tissues. Here silk-PPy composite films are tested for performance under biologically relevant conditions including exposure to a complex protein serum and biologically relevant temperatures. Free-end bending actuation performance, current response, force generation and, mass degradation were investigated . Preliminary results show that when exposed to proteins and biologically relevant temperatures, these silk-PPy composites show minimal degradation and are able to generate forces and conduct currents comparable to devices tested under standard conditions. NSF.

Scale-up of water-based spider silk film casting using a film applicator.

PubMed

Agostini, Elisa; Winter, Gerhard; Engert, Julia

2017-10-30

Spider silk proteins for applications in drug delivery have attracted an increased interest during the past years. Some possible future medical applications for this biocompatible and biodegradable material are scaffolds for tissue engineering, implantable drug delivery systems and coatings for implants. Recently, we reported on the preparation of water-based spider silk films for drug delivery applications. In the current study, we describe the development of a manufacturing technique for casting larger spider silk films from aqueous solution employing a film applicator. Films were characterized in terms of morphology, water solubility, protein secondary structure, thermal stability, and mechanical properties. Different post-treatments were evaluated (phosphate ions, ethanol, steam sterilization and water vapor) to increase the content of β-sheets thereby achieving water insolubility of the films. Finally, the mechanical properties of the spider silk films were improved by incorporating 2-pyrrolidone as plasticizer. Copyright © 2017 Elsevier B.V. All rights reserved.

Native Silk Feedstock as a Model Biopolymer: A Rheological Perspective.

PubMed

Laity, Peter R; Holland, Chris

2016-08-08

Variability in silk's rheology is often regarded as an impediment to understanding or successfully copying the natural spinning process. We have previously reported such variability in unspun native silk extracted straight from the gland of the domesticated silkworm Bombyx mori and discounted classical explanations such as differences in molecular weight and concentration. We now report that variability in oscillatory measurements can be reduced onto a simple master-curve through normalizing with respect to the crossover. This remarkable result suggests that differences between silk feedstocks are rheologically simple and not as complex as originally thought. By comparison, solutions of poly(ethylene-oxide) and hydroxypropyl-methyl-cellulose showed similar normalization behavior; however, the resulting curves were broader than for silk, suggesting greater polydispersity in the (semi)synthetic materials. Thus, we conclude Nature may in fact produce polymer feedstocks that are more consistent than typical man-made counterparts as a model for future rheological investigations.

Acid extraction and purification of recombinant spider silk proteins.

PubMed

Mello, Charlene M; Soares, Jason W; Arcidiacono, Steven; Butler, Michelle M

2004-01-01

A procedure has been developed for the isolation of recombinant spider silk proteins based upon their unique stability and solubilization characteristics. Three recombinant silk proteins, (SpI)7, NcDS, and [(SpI)4/(SpII)1]4, were purified by extraction with organic acids followed by affinity or ion exchange chromatography resulting in 90-95% pure silk solutions. The protein yield of NcDS (15 mg/L culture) and (SpI)7 (35 mg/L) increased 4- and 5-fold, respectively, from previously reported values presumably due to a more complete solubilization of the expressed recombinant protein. [(SpI)4/(SpII)1]4, a hybrid protein based on the repeat sequences of spidroin I and spidroin II, had a yield of 12.4 mg/L. This method is an effective, reproducible technique that has broad applicability for a variety of silk proteins as well as other acid stable biopolymers.

Biopatterning of Silk Proteins for Soft Micro-optics.

PubMed

Pal, Ramendra K; Kurland, Nicholas E; Wang, Congzhou; Kundu, Subhas C; Yadavalli, Vamsi K

2015-04-29

Silk proteins from spiders and silkworms have been proposed as outstanding candidates for soft micro-optic and photonic applications because of their optical transparency, unique biological properties, and mechanical robustness. Here, we present a method to form microstructures of the two constituent silk proteins, fibroin and sericin for use as an optical biomaterial. Using photolithography, chemically modified silk protein photoresists are patterned in 2D arrays of periodic patterns and Fresnel zone plates. Angle-dependent iridescent colors are produced in these periodic micropatterns because of the Bragg diffraction. Silk protein photolithography can used to form patterns on different substrates including flexible sheets with features of any shape with high fidelity and resolution over large areas. Finally, we show that these mechanically stable and transparent iridescent architectures are also completely biodegradable. This versatile and scalable technique can therefore be used to develop biocompatible, soft micro-optic devices that can be degraded in a controlled manner.

Nanoscale probing of electron-regulated structural transitions in silk proteins by near-field IR imaging and nano-spectroscopy

PubMed Central

Qin, Nan; Zhang, Shaoqing; Jiang, Jianjuan; Corder, Stephanie Gilbert; Qian, Zhigang; Zhou, Zhitao; Lee, Woonsoo; Liu, Keyin; Wang, Xiaohan; Li, Xinxin; Shi, Zhifeng; Mao, Ying; Bechtel, Hans A.; Martin, Michael C.; Xia, Xiaoxia; Marelli, Benedetto; Kaplan, David L.; Omenetto, Fiorenzo G.; Liu, Mengkun; Tao, Tiger H.

2016-01-01

Silk protein fibres produced by silkworms and spiders are renowned for their unparalleled mechanical strength and extensibility arising from their high-β-sheet crystal contents as natural materials. Investigation of β-sheet-oriented conformational transitions in silk proteins at the nanoscale remains a challenge using conventional imaging techniques given their limitations in chemical sensitivity or limited spatial resolution. Here, we report on electron-regulated nanoscale polymorphic transitions in silk proteins revealed by near-field infrared imaging and nano-spectroscopy at resolutions approaching the molecular level. The ability to locally probe nanoscale protein structural transitions combined with nanometre-precision electron-beam lithography offers us the capability to finely control the structure of silk proteins in two and three dimensions. Our work paves the way for unlocking essential nanoscopic protein structures and critical conditions for electron-induced conformational transitions, offering new rules to design protein-based nanoarchitectures. PMID:27713412

In Vivo Coating of Bacterial Magnetic Nanoparticles by Magnetosome Expression of Spider Silk-Inspired Peptides.

PubMed

Mickoleit, Frank; Borkner, Christian B; Toro-Nahuelpan, Mauricio; Herold, Heike M; Maier, Denis S; Plitzko, Jürgen M; Scheibel, Thomas; Schüler, Dirk

2018-03-12

Magnetosomes are natural magnetic nanoparticles with exceptional properties that are synthesized in magnetotactic bacteria by a highly regulated biomineralization process. Their usability in many applications could be further improved by encapsulation in biocompatible polymers. In this study, we explored the production of spider silk-inspired peptides on magnetosomes of the alphaproteobacterium Magnetospirillum gryphiswaldense. Genetic fusion of different silk sequence-like variants to abundant magnetosome membrane proteins enhanced magnetite biomineralization and caused the formation of a proteinaceous capsule, which increased the colloidal stability of isolated particles. Furthermore, we show that spider silk peptides fused to a magnetosome membrane protein can be used as seeds for silk fibril growth on the magnetosome surface. In summary, we demonstrate that the combination of two different biogenic materials generates a genetically encoded hybrid composite with engineerable new properties and enhanced potential for various applications.

Genipin-crosslinked gelatin-silk fibroin hydrogels for modulating the behaviour of pluripotent cells.

PubMed

Sun, Wei; Incitti, Tania; Migliaresi, Claudio; Quattrone, Alessandro; Casarosa, Simona; Motta, Antonella

2016-10-01

Different hydrogel materials have been prepared to investigate the effects of culture substrate on the behaviour of pluripotent cells. In particular, genipin-crosslinked gelatin-silk fibroin hydrogels of different compositions have been prepared, physically characterized and used as substrates for the culture of pluripotent cells. Pluripotent cells cultured on hydrogels remained viable and proliferated. Gelatin and silk fibroin promoted the proliferation of cells in the short and long term, respectively. Moreover, cells cultured on genipin-crosslinked gelatin-silk fibroin blended hydrogels were induced to an epithelial ectodermal differentiation fate, instead of the neural ectodermal fate obtained by culturing on tissue culture plates. This work confirms that specific culture substrates can be used to modulate the behaviour of pluripotent cells and that our genipin-crosslinked gelatin-silk fibroin blended hydrogels can induce pluripotent cells differentiation to an epithelial ectodermal fate. Copyright © 2014 John Wiley & Sons, Ltd. Copyright © 2014 John Wiley & Sons, Ltd.

Impact of Protein-Metal Ion Interactions on the Crystallization of Silk Fibroin Protein

NASA Astrophysics Data System (ADS)

Hu, Xiao; Lu, Qiang; Kaplan, David; Cebe, Peggy

2009-03-01

Proteins can easily form bonds with a variety of metal ions, which provides many unique biological functions for the protein structures, and therefore controls the overall structural transformation of proteins. We use advanced thermal analysis methods such as temperature modulated differential scanning calorimetry and quasi-isothermal TMDSC, combined with Fourier transform infrared spectroscopy, and scanning electron microscopy, to investigate the protein-metallic ion interactions in Bombyx mori silk fibroin proteins. Silk samples were mixed with different metal ions (Ca^2+, K^+, Ma^2+, Na^+, Cu^2+, Mn^2+) with different mass ratios, and compared with the physical conditions in the silkworm gland. Results show that all metallic ions can directly affect the crystallization behavior and glass transition of silk fibroin. However, different ions tend to have different structural impact, including their role as plasticizer or anti-plasticizer. Detailed studies reveal important information allowing us better to understand the natural silk spinning and crystallization process.

Dynamic behaviour of silks: Nature's precision nanocomposites

NASA Astrophysics Data System (ADS)

Drodge, D. R.; Mortimer, B.; Siviour, C. R.; Holland, C.

2012-08-01

Silk is often cited as a material worth imitating, due to its high strength and toughness. In order to produce a synthetic analogue, or enhanced natural version, the microstructural basis of these properties must be understood. Current understanding is that silk deforms through the detachment of nano-scale crystallites, in the manner of a damaged composite. This picture forms the basis for constitutive models, but validation data is limited to low strain-rates. Here we present a programme of research in which high-rate behaviour is studied through ballistic impact experiments. These have been applied to the silk of the Bombyx mori moth, as harvested from cocoons, and to the major ampullate thread of the golden orb weaver spider Nephila edulis. Longitudinal wave-speeds, and air drag coefficients, have been calculated for selected cases. Differences between the response of various silks and a similar synthetic fibre, nylon, are discussed, and future plans are presented.

Unravelling the biodiversity of nanoscale signatures of spider silk fibres

NASA Astrophysics Data System (ADS)

Silva, Luciano P.; Rech, Elibio L.

2013-12-01

Living organisms are masters at designing outstanding self-assembled nanostructures through a hierarchical organization of modular proteins. Protein-based biopolymers improved and selected by the driving forces of molecular evolution are among the most impressive archetypes of nanomaterials. One of these biomacromolecules is the myriad of compound fibroins of spider silks, which combine surprisingly high tensile strength with great elasticity. However, no consensus on the nano-organization of spider silk fibres has been reached. Here we explore the biodiversity of spider silk fibres, focusing on nanoscale characterization with high-resolution atomic force microscopy. Our results reveal an evolution of the nanoroughness, nanostiffness, nanoviscoelastic, nanotribological and nanoelectric organization of microfibres, even when they share similar sizes and shapes. These features are related to unique aspects of their molecular structures. The results show that combined nanoscale analyses of spider silks may enable the screening of appropriate motifs for bioengineering synthetic fibres from recombinant proteins.

Review the role of terminal domains during storage and assembly of spider silk proteins.

PubMed

Eisoldt, Lukas; Thamm, Christopher; Scheibel, Thomas

2012-06-01

Fibrous proteins in nature fulfill a wide variety of functions in different structures ranging from cellular scaffolds to very resilient structures like tendons and even extra-corporal fibers such as silks in spider webs or silkworm cocoons. Despite their different origins and sequence varieties many of these fibrous proteins share a common building principle: they consist of a large repetitive core domain flanked by relatively small non-repetitive terminal domains. Amongst protein fibers, spider dragline silk shows prominent mechanical properties that exceed those of man-made fibers like Kevlar. Spider silk fibers assemble in a spinning process allowing the transformation from an aqueous solution into a solid fiber within milliseconds. Here, we highlight the role of the non-repetitive terminal domains of spider dragline silk proteins during storage in the gland and initiation of the fiber assembly process. Copyright © 2011 Wiley Periodicals, Inc.

Visual Literacy with Picture Books: The Silk Road

ERIC Educational Resources Information Center

Bisland, Beverly Milner Lee

2007-01-01

The ancient Silk Routes connecting China to Europe across the rugged mountains and deserts of central Asia are one of the primary examples of transculturation in world history. Traders on these routes dealt not only in goods such as silk and horses but also made possible the spread of art forms as well as two major religions, Buddhism and Islam. …

Spinning of Fibers from Aqueous Solutions

DTIC Science & Technology

2003-08-01

recombinant silk product BioSteel . Publications, patents and presentations 1. Arcidiacono, S., et al., Purification and characterization of recombinant...ABSTRACT Previous funding supporting this research focused primarily on development of the aqueous-based method for processing silk into spin solutions. Much...of this effort consisted of production of recombinant silk protein in bacterial and yeast expression systems. In spite of the small quantities

Beneficial Effects of Corn Silk on Metabolic Syndrome.

PubMed

Wang, Bing; Xiao, Tiegang; Ruan, Jun; Liu, Wensheng

2017-01-01

Metabolic syndrome (MS) is a very common medical problem worldwide. It includes obesity, hypertension, hyperglycemia, and abnormal levels of triglycerides and high-density lipoprotein cholesterol. It is closely associated with insulin resistance and may lead to diabetes mellitus, liver diseases, or cardiovascular diseases. Corn silk (CS), a traditional Chinese medicine, has been reported to have multiple beneficial effects, including hypotensive, anti-diabetic, and hypolipidemic properties. This suggests that corn silk could be used to treat or prevent metabolic syndrome. In this review, we will discuss the potential role of corn silk in different components of metabolic syndrome. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Smart assembly of polymer fibers: lessons from major ampullate spider silk

NASA Astrophysics Data System (ADS)

Viney, Christopher

1996-02-01

Studies of major ampullate silk (MAS), especially the secretions and fibers produced by the spider Nephila clavipes (golden orb weaver), have yielded several results of potential value to the materials scientist/engineer. There are lessons to be learned about synthesis, processing and microstructural design of high-tensile polymer fibers. The 'smart' aspect of silk production in nature concerns the ability of the spider to rapidly process a concentrated, viscous aqueous solution of silk protein (stored in the gland) into water-insoluble fiber on demand. This process centers on the assembly of a shear-sensitive supramolecular liquid crystalline phase by aggregation of the solubilized globular protein molecules.

Bioengineered Chimeric Spider Silk-Uranium Binding Proteins

PubMed Central

Krishnaji, Sreevidhya Tarakkad; Kaplan, David L.

2014-01-01

Heavy metals constitute a source of environmental pollution. Here, novel functional hybrid biomaterials for specific interactions with heavy metals are designed by bioengineering consensus sequence repeats from spider silk of Nephila clavipes with repeats of a uranium peptide recognition motif from a mutated 33-residue of calmodulin protein from Paramecium tetraurelia. The self-assembly features of the silk to control nanoscale organic/inorganic material interfaces provides new biomaterials for uranium recovery. With subsequent enzymatic digestion of the silk to concentrate the sequestered metals, options can be envisaged to use these new chimeric protein systems in environmental engineering, including to remediate environments contaminated by uranium. PMID:23212989

Towards a new generation of fibre optic chemical sensors based on spider silk threads

NASA Astrophysics Data System (ADS)

Hey Tow, Kenny; Chow, Desmond M.; Vollrath, Fritz; Dicaire, Isabelle; Gheysens, Tom; Thévenaz, Luc

2017-04-01

A spider uses up to seven different types of silk, all having specific functions, to build its web. For scientists, native silk - directly extracted from spiders - is a tough, biodegradable and biocompatible thread used mainly for tissue engineering and textile applications. Blessed with outstanding optical properties, this protein strand can also be used as an optical fibre and is, moreover, intrinsically sensitive to chemical compounds. In this communication, a pioneering proof-of-concept experiment using spider silk, in its pristine condition, as a new type of fibre-optic relative humidity sensor will be demonstrated and its potential for future applications discussed.

Processing and characterization of silk sericin from Bombyx mori and its application in biomaterials and biomedicines.

PubMed

Cao, Ting-Ting; Zhang, Yu-Qing

2016-04-01

Bombyx mori silk is composed of 60-80% fibroin, 15-35% sericin and 1-5% non-sericin component including wax, pigments, sugars and other impurities. For two decades, the protein-based silk fibroin was extensively used in the research and development of medical biomaterials and biomedicines. Sericin is frequently ignored and abandoned as a byproduct or waste in the processing of traditional silk fabrics, silk floss or modern silk biomaterials. However, similar to fibroin, sericin is not only a highly useful biological material, but also a lot of biological activity. Moreover, the non-sericin component present with sericin in the cocoon shell also has a strong biological activity. In this review, the extraction and recovery methods of sericin and the non-sericin component from the cocoon layer are reported, and their composition, properties and biological activity are described to produce a comprehensive report on biomedical materials and biological drugs. In addition, related problems or concerns present in the research and development of sericin are discussed, and a potential application of sericin in sustainable development is also presented. Copyright © 2015 Elsevier B.V. All rights reserved.

Biomimetic Nanofibrillation in Two-Component Biopolymer Blends with Structural Analogs to Spider Silk

NASA Astrophysics Data System (ADS)

Xie, Lan; Xu, Huan; Li, Liang-Bin; Hsiao, Benjamin S.; Zhong, Gan-Ji; Li, Zhong-Ming

2016-10-01

Despite the enormous potential in bioinspired fabrication of high-strength structure by mimicking the spinning process of spider silk, currently accessible routes (e.g., microfluidic and electrospinning approaches) still have substantial function gaps in providing precision control over the nanofibrillar superstructure, crystalline morphology or molecular orientation. Here the concept of biomimetic nanofibrillation, by copying the spiders’ spinning principles, was conceived to build silk-mimicking hierarchies in two-phase biodegradable blends, strategically involving the stepwise integration of elongational shear and high-pressure shear. Phase separation confined on nanoscale, together with deformation of discrete phases and pre-alignment of polymer chains, was triggered in the elongational shear, conferring the readiness for direct nanofibrillation in the latter shearing stage. The orderly aligned nanofibrils, featuring an ultralow diameter of around 100 nm and the “rigid-soft” system crosslinked by nanocrystal domains like silk protein dopes, were secreted by fine nanochannels. The incorporation of multiscale silk-mimicking structures afforded exceptional combination of strength, ductility and toughness for the nanofibrillar polymer composites. The proposed spider spinning-mimicking strategy, offering the biomimetic function integration unattainable with current approaches, may prompt materials scientists to pursue biopolymer mimics of silk with high performance yet light weight.

Biomimetic Nanofibrillation in Two-Component Biopolymer Blends with Structural Analogs to Spider Silk.

PubMed

Xie, Lan; Xu, Huan; Li, Liang-Bin; Hsiao, Benjamin S; Zhong, Gan-Ji; Li, Zhong-Ming

2016-10-03

Despite the enormous potential in bioinspired fabrication of high-strength structure by mimicking the spinning process of spider silk, currently accessible routes (e.g., microfluidic and electrospinning approaches) still have substantial function gaps in providing precision control over the nanofibrillar superstructure, crystalline morphology or molecular orientation. Here the concept of biomimetic nanofibrillation, by copying the spiders' spinning principles, was conceived to build silk-mimicking hierarchies in two-phase biodegradable blends, strategically involving the stepwise integration of elongational shear and high-pressure shear. Phase separation confined on nanoscale, together with deformation of discrete phases and pre-alignment of polymer chains, was triggered in the elongational shear, conferring the readiness for direct nanofibrillation in the latter shearing stage. The orderly aligned nanofibrils, featuring an ultralow diameter of around 100 nm and the "rigid-soft" system crosslinked by nanocrystal domains like silk protein dopes, were secreted by fine nanochannels. The incorporation of multiscale silk-mimicking structures afforded exceptional combination of strength, ductility and toughness for the nanofibrillar polymer composites. The proposed spider spinning-mimicking strategy, offering the biomimetic function integration unattainable with current approaches, may prompt materials scientists to pursue biopolymer mimics of silk with high performance yet light weight.

Natural Non-Mulberry Silk Nanoparticles for Potential-Controlled Drug Release

PubMed Central

Wang, Juan; Yin, Zhuping; Xue, Xiang; Kundu, Subhas C.; Mo, Xiumei; Lu, Shenzhou

2016-01-01

Natural silk protein nanoparticles are a promising biomaterial for drug delivery due to their pleiotropic properties, including biocompatibility, high bioavailability, and biodegradability. Chinese oak tasar Antheraea pernyi silk fibroin (ApF) nanoparticles are easily obtained using cations as reagents under mild conditions. The mild conditions are potentially advantageous for the encapsulation of sensitive drugs and therapeutic molecules. In the present study, silk fibroin protein nanoparticles are loaded with differently-charged small-molecule drugs, such as doxorubicin hydrochloride, ibuprofen, and ibuprofen-Na, by simple absorption based on electrostatic interactions. The structure, morphology and biocompatibility of the silk nanoparticles in vitro are investigated. In vitro release of the drugs from the nanoparticles depends on charge-charge interactions between the drugs and the nanoparticles. The release behavior of the compounds from the nanoparticles demonstrates that positively-charged molecules are released in a more prolonged or sustained manner. Cell viability studies with L929 demonstrated that the ApF nanoparticles significantly promoted cell growth. The results suggest that Chinese oak tasar Antheraea pernyi silk fibroin nanoparticles can be used as an alternative matrix for drug carrying and controlled release in diverse biomedical applications. PMID:27916946

Viability and neuronal differentiation of neural stem cells encapsulated in silk fibroin hydrogel functionalized with an IKVAV peptide.

PubMed

Sun, Wei; Incitti, Tania; Migliaresi, Claudio; Quattrone, Alessandro; Casarosa, Simona; Motta, Antonella

2017-05-01

Three-dimensional (3D) porous scaffolds combined with therapeutic stem cells play vital roles in tissue engineering. The adult brain has very limited regeneration ability after injuries such as trauma and stroke. In this study, injectable 3D silk fibroin-based hydrogel scaffolds with encapsulated neural stem cells were developed, aiming at supporting brain regeneration. To improve the function of the hydrogel towards neural stem cells, silk fibroin was modified by an IKVAV peptide through covalent binding. Both unmodified and modified silk fibroin hydrogels were obtained, through sonication, with mechanical stiffness comparable to that of brain tissue. Human neural stem cells were encapsulated in both hydrogels and the effects of IKVAV peptide conjugation on cell viability and neural differentiation were assessed. The silk fibroin hydrogel modified by IKVAV peptide showed increased cell viability and an enhanced neuronal differentiation capability, which contributed to understanding the effects of IKVAV peptide on the behaviour of neural stem cells. For these reasons, IKVAV-modified silk fibroin is a promising material for brain tissue engineering. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

Unraveling the Molecular Requirements for Macroscopic Silk Supercontraction.

PubMed

Giesa, Tristan; Schuetz, Roman; Fratzl, Peter; Buehler, Markus J; Masic, Admir

2017-10-24

Spider dragline silk is a protein material that has evolved over millions of years to achieve finely tuned mechanical properties. A less known feature of some dragline silk fibers is that they shrink along the main axis by up to 50% when exposed to high humidity, a phenomenon called supercontraction. This contrasts the typical behavior of many other materials that swell when exposed to humidity. Molecular level details and mechanisms of the supercontraction effect are heavily debated. Here we report a molecular dynamics analysis of supercontraction in Nephila clavipes silk combined with in situ mechanical testing and Raman spectroscopy linking the reorganization of the nanostructure to the polar and charged amino acids in the sequence. We further show in our in silico approach that point mutations of these groups not only suppress the supercontraction effect, but even reverse it, while maintaining the exceptional mechanical properties of the silk material. This work has imminent impact on the design of biomimetic equivalents and recombinant silks for which supercontraction may or may not be a desirable feature. The approach applied is appropriate to explore the effect of point mutations on the overall physical properties of protein based materials.

Bio-functionalized silk hydrogel microfluidic systems.

PubMed

Zhao, Siwei; Chen, Ying; Partlow, Benjamin P; Golding, Anne S; Tseng, Peter; Coburn, Jeannine; Applegate, Matthew B; Moreau, Jodie E; Omenetto, Fiorenzo G; Kaplan, David L

2016-07-01

Bio-functionalized microfluidic systems were developed based on a silk protein hydrogel elastomeric materials. A facile multilayer fabrication method using gelatin sacrificial molding and layer-by-layer assembly was implemented to construct interconnected, three dimensional (3D) microchannel networks in silk hydrogels at 100 μm minimum feature resolution. Mechanically activated valves were implemented to demonstrate pneumatic control of microflow. The silk hydrogel microfluidics exhibit controllable mechanical properties, long-term stability in various environmental conditions, tunable in vitro and in vivo degradability in addition to optical transparency, providing unique features for cell/tissue-related applications than conventional polydimethylsiloxane (PDMS) and existing hydrogel-based microfluidic options. As demonstrated in the work here, the all aqueous-based fabrication process at ambient conditions enabled the incorporation of active biological substances in the bulk phase of these new silk microfluidic systems during device fabrication, including enzymes and living cells, which are able to interact with the fluid flow in the microchannels. These silk hydrogel-based microfluidic systems offer new opportunities in engineering active diagnostic devices, tissues and organs that could be integrated in vivo, and for on-chip cell sensing systems. Copyright © 2016 Elsevier Ltd. All rights reserved.

Impact of silk biomaterial structure on proteolysis.

PubMed

Brown, Joseph; Lu, Chia-Li; Coburn, Jeannine; Kaplan, David L

2015-01-01

The goal of this study was to determine the impact of silk biomaterial structure (e.g. solution, hydrogel, film) on proteolytic susceptibility. In vitro enzymatic degradation of silk fibroin hydrogels and films was studied using a variety of proteases, including proteinase K, protease XIV, α-chymotrypsin, collagenase, matrix metalloproteinase-1 (MMP-1) and MMP-2. Hydrogels were used to assess bulk degradation while films were used to assess surface degradation. Weight loss, secondary structure determined by Fourier transform infrared spectroscopy and degradation products analyzed via sodium dodecyl sulfate-polyacrylamide gel electrophoresis were used to evaluate degradation over 5 days. Silk films were significantly degraded by proteinase K, while silk hydrogels were degraded more extensively by protease XIV and proteinase K. Collagenase preferentially degraded the β-sheet content in hydrogels while protease XIV and α-chymotrypsin degraded the amorphous structures. MMP-1 and MMP-2 degraded silk fibroin in solution, resulting in a decrease in peptide fragment sizes over time. The link between primary sequence mapping with protease susceptibility provides insight into the role of secondary structure in impacting proteolytic access by comparing solution vs. solid state proteolytic susceptibility. Copyright © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Biomimetic Nanofibrillation in Two-Component Biopolymer Blends with Structural Analogs to Spider Silk

PubMed Central

Xie, Lan; Xu, Huan; Li, Liang-Bin; Hsiao, Benjamin S.; Zhong, Gan-Ji; Li, Zhong-Ming

2016-01-01

Despite the enormous potential in bioinspired fabrication of high-strength structure by mimicking the spinning process of spider silk, currently accessible routes (e.g., microfluidic and electrospinning approaches) still have substantial function gaps in providing precision control over the nanofibrillar superstructure, crystalline morphology or molecular orientation. Here the concept of biomimetic nanofibrillation, by copying the spiders’ spinning principles, was conceived to build silk-mimicking hierarchies in two-phase biodegradable blends, strategically involving the stepwise integration of elongational shear and high-pressure shear. Phase separation confined on nanoscale, together with deformation of discrete phases and pre-alignment of polymer chains, was triggered in the elongational shear, conferring the readiness for direct nanofibrillation in the latter shearing stage. The orderly aligned nanofibrils, featuring an ultralow diameter of around 100 nm and the “rigid−soft” system crosslinked by nanocrystal domains like silk protein dopes, were secreted by fine nanochannels. The incorporation of multiscale silk-mimicking structures afforded exceptional combination of strength, ductility and toughness for the nanofibrillar polymer composites. The proposed spider spinning-mimicking strategy, offering the biomimetic function integration unattainable with current approaches, may prompt materials scientists to pursue biopolymer mimics of silk with high performance yet light weight. PMID:27694989

Egg Case Silk Gene Sequences from Argiope Spiders: Evidence for Multiple Loci and a Loss of Function Between Paralogs

PubMed Central

Chaw, R. Crystal; Collin, Matthew; Wimmer, Marjorie; Helmrick, Kara-Leigh; Hayashi, Cheryl Y.

2017-01-01

Spiders swath their eggs with silk to protect developing embryos and hatchlings. Egg case silks, like other fibrous spider silks, are primarily composed of proteins called spidroins (spidroin = spider-fibroin). Silks, and thus spidroins, are important throughout the lives of spiders, yet the evolution of spidroin genes has been relatively understudied. Spidroin genes are notoriously difficult to sequence because they are typically very long (≥ 10 kb of coding sequence) and highly repetitive. Here, we investigate the evolution of spider silk genes through long-read sequencing of Bacterial Artificial Chromosome (BAC) clones. We demonstrate that the silver garden spider Argiope argentata has multiple egg case spidroin loci with a loss of function at one locus. We also use degenerate PCR primers to search the genomic DNA of congeneric species and find evidence for multiple egg case spidroin loci in other Argiope spiders. Comparative analyses show that these multiple loci are more similar at the nucleotide level within a species than between species. This pattern is consistent with concerted evolution homogenizing gene copies within a genome. More complicated explanations include convergent evolution or recent independent gene duplications within each species. PMID:29127108

Transmission Electron Microscopy of Bombyx Mori Silk Fibers

NASA Astrophysics Data System (ADS)

Shen, Y.; Martin, D. C.

1997-03-01

The microstructure of B. Mori silk fibers before and after degumming was examined by TEM, selected area electron diffraction (SAED), WAXS and low voltage SEM. SEM micrographs of the neat cocoon revealed a network of pairs of twisting filaments. After degumming, there were only individual filaments showing a surface texture consistent with an oriented fibrillar structure in the fiber interior. WAXS patterns confirmed the oriented beta-sheet crystal structure common to silkworm and spider silks. Low dose SAED results were fully consistent with the WAXS data, and revealed that the crystallographic texture did not vary significantly across the fiber diameter. TEM observations of microtomed fiber cross sections indicated a somewhat irregular shape, and also revealed a 0.5-2 micron sericin coating which was removed by the degumming process. TEM observations of the degummed silk fiber showed banded features with a characteristic spacing of nominally 600 nm along the fiber axis. These bands were oriented in a roughly parabolic or V-shape pointing along one axis within a given fiber. We hypothesize that this orientation is induced by the extrusion during the spinning process. Equatorial DF images revealed that axial and lateral sizes of the β-sheet crystallites in silk fibroin ranged from 20 to 170 nm and from 1 to 24 nm, respectively. Crazes developed in the degummed silk fiber parallel to the fiber direction. The formation of these crazes suggests that there are significant lateral interactions between fibrils in silk fibers.

Silk fibroin hydrogel as physical barrier for prevention of post hernia adhesion.

PubMed

Konar, S; Guha, R; Kundu, B; Nandi, S; Ghosh, T K; Kundu, S C; Konar, A; Hazra, S

2017-02-01

Adhesion formation remains a major complication following hernia repair surgery. Physical barriers though effective for adhesion prevention in clinical settings are associated with major disadvantages, therefore, needs further investigation. This study evaluates silk fibroin hydrogel as a physical barrier on polypropylene mesh for the prevention of adhesion following ventral hernia repair. Peritoneal explants were cultured on silk fibroin scaffold to evaluate its support for mesothelial cell growth. Full thickness uniform sized defects were created on the ventral abdominal wall of rabbits, and the defects were covered either with silk hydrogel coated polypropylene mesh or with plain polypropylene mesh as a control. The animals were killed after 1 month, and the adhesion formation was graded; healing response of peritoneum was evaluated by immunohistochemistry with calretinin, collagen staining of peritoneal sections, and expression of PCNA, collagen-I, TNFα, IL6 by real time PCR; and its adverse effect if any was determined. Silk fibroin scaffold showed excellent support for peritoneal cell growth in vitro and the cells expressed calretinin. A remarkable prevention of adhesion formation was observed in the animals implanted with silk hydrogel coated mesh compared to the control group; in these animals peritoneal healing was complete and predominantly by mesothelial cells with minimum fibrotic changes. Expression of inflammatory cytokines decreased compared to control animals, histology of abdominal organs, haematological and blood biochemical parameters remained normal. Therefore, silk hydrogel coating of polypropylene mesh can improve peritoneal healing, minimize adhesion formation, is safe and can augment the outcome of hernia surgery.

Wind induces variations in spider web geometry and sticky spiral droplet volume.

PubMed

Wu, Chao-Chia; Blamires, Sean J; Wu, Chung-Lin; Tso, I-Min

2013-09-01

Trap building by animals is rare because it comes at a substantial cost. Using materials with properties that vary across environments maintains trap functionality. The sticky spiral silks of spider orb webs are used to catch flying prey. Web geometry, accompanied by compensatory changes in silk properties, may change across environments to sustain web functionality. We exposed the spider Cyclosa mulmeinensis to wind to test whether wind-induced changes in web geometry are accompanied by changes in aggregate silk droplet morphology, axial thread width or spiral stickiness. We compared: (i) web catching area, (ii) length of total silks, (iii) mesh height, (iv) number of radii, (v) aggregate droplet morphology and (vi) spiral thread stickiness, between webs made by spiders exposed to wind and those made by spiders not exposed to wind. We interpreted co-variation in droplet morphology or spiral stickiness with web capture area, mesh height or spiral length as the silk properties functionally compensating for changes in web geometry to reduce wind drag. Wind-exposed C. mulmeinensis built webs with smaller capture areas, shorter capture spiral lengths and more widely spaced capture spirals, resulting in the expenditure of less silk. Individuals that were exposed to wind also deposited larger droplets of sticky silk but the stickiness of the spiral threads remained unchanged. The larger droplets may be a product of a greater investment in water, or low molecular weight compounds facilitating atmospheric water uptake. Either way, droplet dehydration in wind is likely to be minimized.

Production of Curcumin-Loaded Silk Fibroin Nanoparticles for Cancer Therapy.

PubMed

Montalbán, Mercedes G; Coburn, Jeannine M; Lozano-Pérez, A Abel; Cenis, José L; Víllora, Gloria; Kaplan, David L

2018-02-24

Curcumin, extracted from the rhizome of Curcuma longa , has been widely used in medicine for centuries due to its anti-inflammatory, anti-cancer, anti-oxidant and anti-microbial effects. However, its bioavailability during treatments is poor because of its low solubility in water, slow dissolution rate and rapid intestinal metabolism. For these reasons, improving the therapeutic efficiency of curcumin using nanocarriers (e.g., biopolymer nanoparticles) has been a research focus, to foster delivery of the curcumin inside cells due to their small size and large surface area. Silk fibroin from the Bombyx mori silkworm is a biopolymer characterized by its biocompatibility, biodegradability, amphiphilic chemistry, and excellent mechanical properties in various material formats. These features make silk fibroin nanoparticles useful vehicles for delivering therapeutic drugs, such as curcumin. Curcumin-loaded silk fibroin nanoparticles were synthesized using two procedures (physical adsorption and coprecipitation) more scalable than methods previously described using ionic liquids. The results showed that nanoparticle formulations were 155 to 170 nm in diameter with a zeta potential of approximately -45 mV. The curcumin-loaded silk fibroin nanoparticles obtained by both processing methods were cytotoxic to carcinogenic cells, while not decreasing viability of healthy cells. In the case of tumor cells, curcumin-loaded silk fibroin nanoparticles presented higher efficacy in cytotoxicity against neuroblastoma cells than hepatocarcinoma cells. In conclusion, curcumin-loaded silk fibroin nanoparticles constitute a biodegradable and biocompatible delivery system with the potential to treat tumors by local, long-term sustained drug delivery.

Production of Curcumin-Loaded Silk Fibroin Nanoparticles for Cancer Therapy

PubMed Central

Coburn, Jeannine M.; Cenis, José L.; Víllora, Gloria; Kaplan, David L.

2018-01-01

Curcumin, extracted from the rhizome of Curcuma longa, has been widely used in medicine for centuries due to its anti-inflammatory, anti-cancer, anti-oxidant and anti-microbial effects. However, its bioavailability during treatments is poor because of its low solubility in water, slow dissolution rate and rapid intestinal metabolism. For these reasons, improving the therapeutic efficiency of curcumin using nanocarriers (e.g., biopolymer nanoparticles) has been a research focus, to foster delivery of the curcumin inside cells due to their small size and large surface area. Silk fibroin from the Bombyx mori silkworm is a biopolymer characterized by its biocompatibility, biodegradability, amphiphilic chemistry, and excellent mechanical properties in various material formats. These features make silk fibroin nanoparticles useful vehicles for delivering therapeutic drugs, such as curcumin. Curcumin-loaded silk fibroin nanoparticles were synthesized using two procedures (physical adsorption and coprecipitation) more scalable than methods previously described using ionic liquids. The results showed that nanoparticle formulations were 155 to 170 nm in diameter with a zeta potential of approximately −45 mV. The curcumin-loaded silk fibroin nanoparticles obtained by both processing methods were cytotoxic to carcinogenic cells, while not decreasing viability of healthy cells. In the case of tumor cells, curcumin-loaded silk fibroin nanoparticles presented higher efficacy in cytotoxicity against neuroblastoma cells than hepatocarcinoma cells. In conclusion, curcumin-loaded silk fibroin nanoparticles constitute a biodegradable and biocompatible delivery system with the potential to treat tumors by local, long-term sustained drug delivery. PMID:29495296

Glycerin-Induced Conformational Changes in Bombyx mori Silk Fibroin Film Monitored by (13)C CP/MAS NMR and ¹H DQMAS NMR.

PubMed

Asakura, Tetsuo; Endo, Masanori; Hirayama, Misaki; Arai, Hiroki; Aoki, Akihiro; Tasei, Yugo

2016-09-09

In order to improve the stiff and brittle characteristics of pure Bombyx mori (B. mori) silk fibroin (SF) film in the dry state, glycerin (Glyc) has been used as a plasticizer. However, there have been very limited studies on the structural characterization of the Glyc-blended SF film. In this study, (13)C Cross Polarization/Magic Angle Spinning nuclear magnetic resonance (CP/MAS NMR) was used to monitor the conformational changes in the films by changing the Glyc concentration. The presence of only 5 wt % Glyc in the film induced a significant conformational change in SF where Silk I* (repeated type II β-turn and no α-helix) newly appeared. Upon further increase in Glyc concentration, the percentage of Silk I* increased linearly up to 9 wt % Glyc and then tended to be almost constant (30%). This value (30%) was the same as the fraction of Ala residue within the Silk I* form out of all Ala residues of SF present in B. mori mature silkworm. The ¹H DQMAS NMR spectra of Glyc-blended SF films confirmed the appearance of Silk I* in the Glyc-blended SF film. A structural model of Glyc-SF complex including the Silk I* form was proposed with the guidance of the Molecular Dynamics (MD) simulation using ¹H-¹H distance constraints obtained from the ¹H Double-Quantum Magic Angle Spinning (DQMAS) NMR spectra.

Facile and eco-friendly fabrication of AgNPs coated silk for antibacterial and antioxidant textiles using honeysuckle extract.

PubMed

Zhou, Yuyang; Tang, Ren-Cheng

2018-01-01

Recently, there is a growing trend towards the functionalization of silk through nanotechnology for the prevention of fiber damage from microbial attack and the enhancement of hygienic aspects. Considering sustainable development and environmental protection, the eco-friendly fabrication of silver nanoparticles (AgNPs)-modified silk using natural extracts has currently become a hot research area. This study presents a facile strategy for the fabrication of colorful and multifunctional silk fabric using biogenic AgNPs prepared by honeysuckle extract as natural reductant and stabilizing agents. The influences of pH and reactant concentrations on the AgNPs synthesis were investigated. The color characteristics and functionalities of AgNPs treated silk were evaluated. The results revealed that the particle size of AgNPs decreased with increasing pH. The diameter of AgNPs decreased with increasing amount of honeysuckle extract and reducing amount of silver nitrate. The transmission electron microscopy image showed that the AgNPs were spherical in shape with a narrow size distribution. The treated silk showed excellent antibacterial activities against E. coli and S. aureus, and certain antioxidant activity. Both of the antibacterial and antioxidant activities were well maintained even after 30 washing cycles. This work provides a sustainable and eco-friendly approach to the fabrication of AgNPs coated silk for colorful and long-term multifunctional textiles using honeysuckle extract. Copyright © 2017 Elsevier B.V. All rights reserved.

Silk or Spandex : Chinas Problematic One Road, One Belt Plan to Expand its Economic Boundaries as Seen Through the Lens of American, British, and Japanese Experience

DTIC Science & Technology

2016-04-04

Yahoo News Website, entry posted February 15, 2016, http://news.yahoo.com/first-silk-road-train-arrives-tehran-china- 134703954.html (accessed on...Intentionally left blank 85 Bibliography Agence France-Presse. “First ’Silk Road’ train arrives in Tehran from China,” Yahoo News

Differential scanning fluorimetry illuminates silk feedstock stability and processability.

PubMed

Dicko, C; Kasoju, N; Hawkins, N; Vollrath, F

2016-01-07

The ability to design and implement silk feedstock formulations for tailored spinning has so far eluded the bioengineers. Recently, the high throughput screening technique of differential scanning fluorimetry (DSF) demonstrated the link between the instability transition temperature (Ti) and the processability of the silk feedstock. Using DSF we screened a large set of chemicals known to affect solvent quality. A multivariate analysis of the results shows that, regardless of the diversity of chemicals, three groupings are significantly distinguishable: G1 = similar to native silk; G2 = largely dominated by electrostatic interactions; and G3 = dominated by chelating interactions. We propose a thermodynamic analysis based on a pre- and post-transition fit to estimate the van't Hoff enthalpies (ΔHv) and the instability temperature (Ti). Our analysis shows that the ΔTi and ΔHv values were distinct: G1 (ΔTi = 0.23 ± 0.2; ΔHv = -159.1 ± 5.6 kcal mol(-1)), G2 (ΔTi = -7.3 ± 0.7; ΔHv = -191.4 ± 5.5 kcal mol(-1)), and G3 (ΔTi = -19.9 ± 3.3; ΔHv = -68.8 ± 6.0 kcal mol(-1)). Our analysis further combined the ΔTi value and the ΔHv value using stability ΔΔG to find that G1 only marginally stabilizes native silks (ΔΔG = -0.15 ± 0.04 kcal mol(-1)), whereas G2 and G3 destabilize native silk (ΔΔG = 3.8 ± 0.11 and ΔΔG = 3.8 ± 0.3 kcal mol(-1), respectively). Here our analysis shows that native silk has a complex multistep transition that is possibly non-cooperative. However, all three groupings also show a direct and cooperative transition with varied stabilization effects. This analysis suggests that native silks are able to sample multiple substates prior to undergoing (or to delay) the final transition. We conclude by hypothesizing that the observed energetic plasticity may be mediated by a fragile packaging of the silk tertiary structure that is readily lost when the solvent quality changes.

Restriction fragment length polymorphism markers associated with silk maysin, antibiosis to corn earworm (Lepidoptera: Noctuidae) larvae, in a dent and sweet corn cross.

PubMed

Guo, B Z; Zhang, Z J; Li, R G; Widstrom, N W; Snook, M E; Lynch, R E; Plaisted, D

2001-04-01

Maysin, a C-glycosylflavone in maize silk, has insecticidal activity against corn earworm, Helicoverpa zea (Boddie), larvae. Sweet corn, Zea mays L., is a vulnerable crop to ear-feeding insects and requires pesticide protection from ear damage. This study was conducted to identify maize chromosome regions associated with silk maysin concentration and eventually to transfer and develop high silk maysin sweet corn lines with marker-assisted selection (MAS). Using an F2 population derived from SC102 (high maysin dent corn) and B31857 (low maysin sh2 sweet corn), we detected two major quantitative trait loci (QTL). It was estimated that 25.6% of the silk maysin variance was associated with segregation in the genomic region of npi286 (flanking to p1) on chromosome 1S. We also demonstrated that a1 on chromosome 3L had major contribution to silk maysin (accounted for 15.7% of the variance). Locus a1 has a recessive gene action for high maysin with the presence of functional p1 allele. Markers umc66a (near c2) and umc105a on chromosome 9S also were detected in this analysis with minor contribution. A multiple-locus model, which included npi286, a1, csu3 (Bin 1.05), umc245 (Bin 7.05), agrr21 (Bin 8.09), umc105a, and the epistatic interactions npi286 x a1, a1 x agrr21, csu3 x umc245, and umc105a x umc245, accounted for 76.3% of the total silk maysin variance. Tester crosses showed that at the a1 locus, SC102 has functional A1 alleles and B31857 has homozygous recessive a1 alleles. Individuals of (SC102 x B31857) x B31857 were examined with MAS and plants with p1 allele from SC102 and homozygous a1 alleles from B31857 had consistent high silk maysin. Marker-assisted selection seems to be a suitable method to transfer silk maysin to sweet corn lines to reduce pesticide application.

Regeneration of Bombyx mori silk nanofibers and nanocomposite fibrils by the electrospinning process

NASA Astrophysics Data System (ADS)

Ayutsede, Jonathan Eyitouyo

In recent years, there has been significant interest in the utilization of natural materials for novel nanoproducts such as tissue engineered scaffolds. Silkworm silk fibers represent one of the strongest natural fibers known. Silkworm silk, a protein-based natural biopolymer, has received renewed interest in recent years due to its unique properties (strength, toughness) and potential applications such as smart textiles, protective clothing and tissue engineering. The traditional 10--20 mum diameter, triangular-shaped Bombyx mori fibers have remained unchanged over the years. However, in our study, we examine the scientific implication and potential applications of reducing the diameter to the nanoscale, changing the triangular shape of the fiber and adding nanofillers in the form of single wall carbon nanotubes (SWNT) by the electrospinning process. The electrospinning process preserves the natural conformation of the silk (random and beta-sheet). The feasibility of changing the properties of the electrospun nanofibers by post processing treatments (annealing and chemical treatment) was investigated. B. mori silk fibroin solution (formic acid) was successfully electrospun to produce uniform nanofibers (as small as 12 nm). Response Surface Methodology (RSM) was applied for the first time to experimental results of electrospinning, to develop a processing window that can reproduce regenerated silk nanofibers of a predictable size (d < 100nm). SWNT-silk multifunctional nanocomposite fibers were fabricated for the first time with anticipated properties (mechanical, thermal and electrically conductive) that may have scientific applications (nerve regeneration, stimulation of cell-scaffold interaction). In order to realize these applications, the following areas need to be addressed: a systematic investigation of the dispersion of the nanotubes in the silk matrix, a determination of new methodologies for characterizing the nanofiber properties and establishing the nature of the silk-SWNT interactions. A new visualization system was developed to characterize the transport properties of the nanofibrous assemblies. The morphological, chemical, structural and mechanical properties of the nanofibers were determined by field emission environmental scanning microscopy, Fourier transform infrared and Raman spectroscopy, wide angle x-ray diffraction and microtensile tester respectively.

Development of structure in natural silk spinning and poly(vinyl alcohol) hydrogel formation

NASA Astrophysics Data System (ADS)

Willcox, Patricia Jeanene

This research involves the characterization of structure and structure formation in aqueous systems. Particularly, these studies investigate the effect of various processing variables on the structure formation that occurs upon conversion from aqueous solution to fiber or hydrogel. The two processes studied include natural silk fiber spinning and physical gelation of poly(vinyl alcohol), PVOH, in water. The techniques employed combine cryogenic technology for sample preparation and direct observation by transmission electron microscopy with electron diffraction, atomic force microscopy, optical rheometry, X-ray scattering and optical microscopy. In order to explore the full range of structure formation in natural silk spinning, studies are conducted in vivo and in vitro. In vivo structural investigations are accomplished through the cryogenic quenching and subsequent microtoming of live silk-spinning animals, Nephila clavipes (spider) and Bombyx mori (silkworm). Observations made using transmission electron microscopy, electron diffraction and atomic force microscopy indicate a cholesteric liquid crystalline mesophase of aqueous silk fibroin in both species. The mechanism of structure formation in solution is studied in vitro using optical rheometry on aqueous solutions made from regenerated Bombyx mori cocoon silk. Concentrated solutions exhibit birefringence under flow, with a wormlike conformation of the silk molecules in concentrated salt solution. Changes in salt concentration and pH of the aqueous silk solutions result in differing degrees of alignment and aggregation. These results suggest that structural control in the natural silk spinning process is accomplished by chemical manipulation of the electrostatic interactions and hydrogen bonding between chains. Application of cryogenic methods in transmission electron microscopy also provides a unique look at hydration-dependent structures in gels of poly(vinyl alcohol) produced by freeze-thaw processing. Morphologies ranging from circular pores to fibrillar networks are observed in gels formed from aqueous PVOH solutions subjected to cycles of freezing and thawing. These morphologies can be directly associated with the progressive nature of the mechanism of gelation as it proceeds from liquid-liquid phase separation to crystallization with increased cycling. A comparison of the structures produced by cycling and by aging suggests that there is a similarity in structural changes, but a superposition of the effects of cycling and aging is not possible.

Spiders spinning electrically charged nano-fibres

PubMed Central

Kronenberger, Katrin; Vollrath, Fritz

2015-01-01

Most spider threads are on the micrometre and sub-micrometre scale. Yet, there are some spiders that spin true nano-scale fibres such as the cribellate orb spider, Uloborus plumipes. Here, we analyse the highly specialized capture silk-spinning system of this spider and compare it with the silk extrusion systems of the more standard spider dragline threads. The cribellar silk extrusion system consists of tiny, morphologically basic glands each terminating through exceptionally long and narrow ducts in uniquely shaped silk outlets. Depending on spider size, hundreds to thousands of these outlet spigots cover the cribellum, a phylogenetically ancient spinning plate. We present details on the unique functional design of the cribellate gland–duct–spigot system and discuss design requirements for its specialist fibrils. The spinning of fibres on the nano-scale seems to have been facilitated by the evolution of a highly specialist way of direct spinning, which differs from the aqua-melt silk extrusion set-up more typical for other spiders. PMID:25631231

Mild process to design silk scaffolds with reduced β-sheet structure and various topographies at nanometer scale

PubMed Central

Pei, Yazhen; Liu, Xi; Liu, Shanshan; Lu, Qiang; Liu, Jing; Kaplan, David L; Zhu, Hesun

2014-01-01

Three-dimensional (3D) porous silk scaffolds with good biocompatibility and minimal immunogenicity, have promising applications in different tissue regenerations. However, a challenge remains to effectively fabricate their microstructures and mechanical properties to satisfy specific requirements of different tissues. In this study, silk scaffolds were fabricated to form extracellular matrix (ECM) mimetic nanofibrous architecture in a mild process. A slowly increasing concentration process was applied to regulate silk self-assembly into nanofibers in aqueous solution. Then glycerol was blended with the nanofiber solution and induced silk crystallization in lyophilization process, endowing freeze-dried scaffolds water-stability. The glycerol was leached from the scaffolds, leaving similar porous structure at a micrometer scale but different topographies at nanoscale. Compared to previous salt-leached and methanol annealed scaffolds, the present scaffolds showed lower β-sheet content, softer mechanical property, and improved cell growth and differentiation behaviors, implying their promising future as platforms for controlling stem cell fate and soft tissue regeneration. PMID:25463497

Identification and classification of silks using infrared spectroscopy

PubMed Central

Boulet-Audet, Maxime; Vollrath, Fritz; Holland, Chris

2015-01-01

ABSTRACT Lepidopteran silks number in the thousands and display a vast diversity of structures, properties and industrial potential. To map this remarkable biochemical diversity, we present an identification and screening method based on the infrared spectra of native silk feedstock and cocoons. Multivariate analysis of over 1214 infrared spectra obtained from 35 species allowed us to group silks into distinct hierarchies and a classification that agrees well with current phylogenetic data and taxonomies. This approach also provides information on the relative content of sericin, calcium oxalate, phenolic compounds, poly-alanine and poly(alanine-glycine) β-sheets. It emerged that the domesticated mulberry silkmoth Bombyx mori represents an outlier compared with other silkmoth taxa in terms of spectral properties. Interestingly, Epiphora bauhiniae was found to contain the highest amount of β-sheets reported to date for any wild silkmoth. We conclude that our approach provides a new route to determine cocoon chemical composition and in turn a novel, biological as well as material, classification of silks. PMID:26347557

Influence of variety and harvest maturity on phytochemical content in corn silk.

PubMed

Sarepoua, Eakrin; Tangwongchai, Ratchada; Suriharn, Bhalang; Lertrat, Kamol

2015-02-15

Corn silk has been used as a traditional herb in Asia. The objective of this study was to evaluate variability in phytochemicals in corn varieties at three maturity stages of corn silk. Ten vegetable corn varieties were evaluated in a completely randomized design with three replications. Data were recorded for total phenolic (TPC), total flavonoids (TFC), total anthocyanin (TAC) and antioxidant activity (AA) by DPPH free-radical-scavenging assays. Differences among corn varieties were observed for all parameters at all maturity stages, and the interactions between maturity stage and corn variety were significant. TPC and TAC were highest at the milky stage, whereas TFC and AA were highest at the silking stage. TPC, TFC and AA were highest in super sweet corn and white corn at the silking stage. PWC5 variety of purple waxy corn at the milky stage had the highest values for all parameters, and it is useful for further development of functional food products. Copyright © 2014 Elsevier Ltd. All rights reserved.

The potential of turmeric (Curcuma xanthorrhiza) in agroforestry system based on silk tree (Albizia chinensis)

NASA Astrophysics Data System (ADS)

Purnomo, D.; Budiastuti, M. S.; Sakya, A. T.; Cholid, M. I.

2018-03-01

Turmeric (Curcuma xanthorrhiza Roxb.) is a traditional medicinal plant. In Indonesia, it is generally cultivated in village home gardens. Famers conducted very simpple cultivation method of turmeric, without specific maintenance and below varies tree. The experiment was conducted by cultivating turmeric below silk trees as in agroforetry system. The experiment was arranged split plot design, the first factor was three level of irradiation (turmeric monoculture/full irradiation, turmeric below silktree with pruning canopy, and turmeric below silk tree no pruning). The second factor was fertilizer NPK 15-15-15 with three levels of doses (100, 150, and 200 kg ha-1). Cultivating turmeric in agroforestry system based on silk tree which were one year old and not yet needed pruning, application of NPK 15-15-15 fertilizer 100 kg ha-1 was enough. The rhizome yield of turmeric 3 months age reaches 139 g per plant (fresh weight). Litter fall from a silk tree one year old in one year is 30 kg per tree per year.

Inducing β-Sheets Formation in Synthetic Spider Silk Fibers by Aqueous Post-Spin Stretching

PubMed Central

Hinman, Michael B.; Holland, Gregory P.; Yarger, Jeffery L.; Lewis, Randolph V.

2012-01-01

As a promising biomaterial with numerous potential applications, various types of synthetic spider silk fibers have been produced and studied in an effort to produce manmade fibers with mechanical and physical properties comparable to those of native spider silk. In this study, two recombinant proteins based on Nephila clavipes Major ampullate Spidroin 1 (MaSp1) consensus repeat sequence were expressed and spun into fibers. Mechanical test results showed that fiber spun from the higher molecular weight protein had better overall mechanical properties (70 KD versus 46 KD), whereas postspin stretch treatment in water helped increase fiber tensile strength significantly. Carbon-13 solid-state NMR studies of those fibers further revealed that the postspin stretch in water promoted protein molecule rearrangement and the formation of β-sheets in the polyalanine region of the silk. The rearrangement correlated with improved fiber mechanical properties and indicated that postspin stretch is key to helping the spider silk proteins in the fiber form correct secondary structures, leading to better quality fibers. PMID:21574576

Studies on Application of Aroma Finish on Silk Fabric

NASA Astrophysics Data System (ADS)

Hipparagi, Sanganna Aminappa; Srinivasa, Thirumalappa; Das, Brojeswari; Naik, Subhas Venkatappa; Purushotham, Serampur Parappa

2016-10-01

Aromatic treatments on textiles have gained importance in the recent years. In the present article work has been done on fragrance finish application on silk material. Silk is an expensive natural fibre used for apparel purpose and known for its feel and appeal. Incorporation of fragrance material in silk product, will add more value to it. Present work focuses to impart durable aroma finish for silk products to be home washed or subjected to dry cleaning. Microencapsulated aroma chemical has been used for the treatment. Impregnation method, Exhaust method, Dip-Pad-Dry method and Spray method have been used to see the influence of application method on the uptake and performance. Evaluation of the aroma treated material has been done through subjective evaluation as per Odor Intensity Reference Scaling (OIRS). Effect of the aroma finishing on the physical properties of the fabric has also been studied. No adverse effect has been observed on the stiffness of the fabric after the aroma treatment.

Spiders spinning electrically charged nano-fibres.

PubMed

Kronenberger, Katrin; Vollrath, Fritz

2015-01-01

Most spider threads are on the micrometre and sub-micrometre scale. Yet, there are some spiders that spin true nano-scale fibres such as the cribellate orb spider, Uloborus plumipes. Here, we analyse the highly specialized capture silk-spinning system of this spider and compare it with the silk extrusion systems of the more standard spider dragline threads. The cribellar silk extrusion system consists of tiny, morphologically basic glands each terminating through exceptionally long and narrow ducts in uniquely shaped silk outlets. Depending on spider size, hundreds to thousands of these outlet spigots cover the cribellum, a phylogenetically ancient spinning plate. We present details on the unique functional design of the cribellate gland-duct-spigot system and discuss design requirements for its specialist fibrils. The spinning of fibres on the nano-scale seems to have been facilitated by the evolution of a highly specialist way of direct spinning, which differs from the aqua-melt silk extrusion set-up more typical for other spiders. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

Mechanical and Physical Properties of Recombinant Spider Silk Films Using Organic and Aqueous Solvents

PubMed Central

2015-01-01

Spider silk has exceptional mechanical and biocompatibility properties. The goal of this study was optimization of the mechanical properties of synthetic spider silk thin films made from synthetic forms of MaSp1 and MaSp2, which compose the dragline silk of Nephila clavipes. We increased the mechanical stress of MaSp1 and 2 films solubilized in both HFIP and water by adding glutaraldehyde and then stretching them in an alcohol based stretch bath. This resulted in stresses as high as 206 MPa and elongations up to 35%, which is 4× higher than the as-poured controls. Films were analyzed using NMR, XRD, and Raman, which showed that the secondary structure after solubilization and film formation in as-poured films is mainly a helical conformation. After the post-pour stretch in a methanol/water bath, the MaSp proteins in both the HFIP and water-based films formed aligned β-sheets similar to those in spider silk fibers. PMID:25030809

Molecular characterization and silk gland expression of Bombyx engrailed and invected genes.

PubMed Central

Hui, C C; Matsuno, K; Ueno, K; Suzuki, Y

1992-01-01

Genetic analysis in Drosophila has shown that engrailed (en) plays an important role in segmentation and neurogenesis. A closely related gene, invected (in), is coexpressed with en in the posterior developmental compartments where en is known to specify cell state. We report here the isolation of two en-like cDNAs from the middle silk glands of Bombyx mori larvae. Sequence analysis revealed that they are the counterparts of Drosophila en and in. Four highly conserved domains, including the homeodomain, were identified in these En and In proteins from Bombyx and Drosophila. In addition, two en-specific and one in-specific domains could also be found. These structurally homologous genes might share a similar role in Bombyx development. They were found to be coexpressed in the middle silk gland but not in the posterior silk gland during the fourth molt/fifth intermolt period. We speculate that these Bombyx en-like genes might be involved in the compartmentalization of the silk gland. Images PMID:1346065

Folding behavior of four silks of giant honey bee reflects the evolutionary conservation of aculeate silk proteins.

PubMed

Maitip, Jakkrawut; Trueman, Holly E; Kaehler, Benjamin D; Huttley, Gavin A; Chantawannakul, Panuwan; Sutherland, Tara D

2015-04-01

Multiple gene duplication events in the precursor of the Aculeata (bees, ants, hornets) gave rise to four silk genes. Whilst these homologs encode proteins with similar amino acid composition and coiled coil structure, the retention of all four homologs implies they each are important. In this study we identified, produced and characterized the four silk proteins from Apis dorsata, the giant Asian honeybee. The proteins were readily purified, allowing us to investigate the folding behavior of solutions of individual proteins in comparison to mixtures of all four proteins at concentrations where they assemble into their native coiled coil structure. In contrast to solutions of any one protein type, solutions of a mixture of the four proteins formed coiled coils that were stable against dilution and detergent denaturation. The results are consistent with the formation of a heteromeric coiled coil protein complex. The mechanism of silk protein coiled coil formation and evolution is discussed in light of these results. Copyright © 2015 Elsevier Ltd. All rights reserved.

An amperometric new methylene blue N-mediating sensor for hydrogen peroxide based on regenerated silk fibroin as an immobilization matrix for peroxidase.

PubMed

Qian, J; Liu, Y; Liu, H; Yu, T; Deng, J

1996-05-01

A simple and effective procedure was described for the immobilization of peroxidase in regenerated silk fibroin membrane prepared from waste silk. The membranes of regenerated silk fibroin with or without peroxidase, before or after the ethanol treatment, were characterized by ir spectra. An amperometric H202 sensor, based on the immobilized peroxidase in regenerated silk fibroin membrane, in the use of new methylene blue N as an electron transfer mediator, was fabricated. The characteristics of the sensor with respect to linearity, response time, effect of pH and temperature, stability, and reproducibility were investigated. Dependences of Michaelis-Menten constant KMapp on the concentration of the mediator, and the applied potential were also studied and the results were presented. The sensor was highly sensitive to H2O2 with a detection limit of 1.0 x 10(-7)M and with response time of less than 40 s.

Construction of a functional silk-based biomaterial complex with immortalized chondrocytes in vivo.

PubMed

Ni, Yusu; Jiang, Yi; Wen, Jianchuan; Shao, Zhenzhong; Chen, Xin; Sun, Shan; Yu, Huiqian; Li, Wen

2014-04-01

To explore the feasibility of constructing a functional biomaterial complex with regenerated silk fibroin membrane and immortalized chondrocytes in vivo. Rat auricular chondrocytes (RACs) were transfected with the lentivirus vector pGC-FU-hTERT-3FLAG or pGC-FU-GFP-3FLAG, encoding the human telomerase reverse transcriptase (hTERT) or GFP gene. The effects of regenerated silk fibroin film on the adhesion, growth of immortalized chondrocytes and expression of collagen II in vitro were analyzed with immunofluorescent histochemistry. Immortalized RACs were transformed. Induction by nutrient medium promoted higher expression levels of collagen II in transformed chondrocytes. The regenerated silk fibroin film was not cytotoxic to immortalized chondrocytes and had no adverse influence on their adhesion. Collagen II expression was good in the immortalized chondrocytes in vivo. The construction of a silk-based biomaterial complex with immortalized chondrocytes may provide a feasible kind of functional biomaterial for the repair of cartilage defects in clinical applications. Copyright © 2013 Wiley Periodicals, Inc.

Microphase Separation Controlled Beta Sheet Crystallization Kinetics in Silk Fibroin Protein.

NASA Astrophysics Data System (ADS)

Hu, Xiao; Lu, Qiang; Kaplan, David; Cebe, Peggy

2009-03-01

We investigate the mechanism of isothermal crystallization kinetics of beta-sheet crystals in silk multiblock fibrous proteins. The Avrami analysis kinetic theory, for studies of synthetic polymer crystal growth, is for the first time extended to investigate protein self-assembly in beta-sheet rich Bombyx mori silk fibroin samples, using time-resolved Fourier transform infrared spectroscopy, differential scanning calorimetry and synchrotron real-time wide-angle X-ray scattering. Results indicate formation of beta sheet crystals in silk proteins is different from the 3-D spherulitic crystal growth found in synthetic homopolymers. Observations by scanning electron microscopy support the view that the protein structures vary during the different stages of crystal growth, and show a microphase separation pattern after chymotrypsin enzyme biodegradation. We present a model to explain the crystallization of the multiblock silk fibroin protein, by analogy to synthetic block copolymers. This model could be widely applicable in other proteins with multiblock (i.e., crystallizable and non-crystallizable) domains.

Ballistic impact to access the high-rate behaviour of individual silk fibres

NASA Astrophysics Data System (ADS)

Drodge, Daniel R.; Mortimer, Beth; Holland, Chris; Siviour, Clive R.

2012-10-01

A revision of a classic transverse fibre impact technique is presented, as applied to the problem of obtaining the high strain-rate constitutive behaviour of commercial Bombyx mori silk. Medium tenacity nylon was also studied. Two approaches are presented: firstly a fixed pre-stress, varied impact velocity method that derives stress-strain behaviour by inverse fit; and secondly a fixed impact velocity, varied pre-stress approach, assuming basic elastic jump conditions to obtain a locus of post-impact states. The post-impact stress-strain states obtained using the two approaches converge for silk but diverge for nylon. This we attribute to silk's fine structure being able to homogenise energy dissipation at static and dynamic deformation rates. However, the coarser microstructure of nylon results in a different loading path dependence, thus divergence in the two approaches. It was also noted that silk exhibited a comparatively stable level of impact energy absorption under varying pre-stress, when compared to nylon.

Structural Properties of Silk Electro-Gels

NASA Astrophysics Data System (ADS)

Tabatabai, A. P.; Urbach, J. S.; Blair, D. L.; Kaplan, D. L.

2013-03-01

The interest in Bombyx Mori silk emerges from its biocompatibility and its structural superiority to synthetic polymers. Our particular interest lies in understanding the capabilities of silk electro-gels because of their reversibility and tunable adhesion. We create an electro-gel by applying a DC electric potential across a reconstituted silk fibroin solution derived directly from Bombyx Mori cocoons. This process leads to the intermolecular self-assembly of fibroin proteins into a weak gel. In this talk we will present our results on the effects of applied shear on electro-gels. We quantify the structural properties while dynamically imaging shear induced fiber formation; known as fibrillogenesis. It is observed that the mechanical properties and microstructure of these materials are highly dependent on shear history. We will also discuss the role of surface modification, through micro-patterning, on the observed gel structure. Our results provide an understanding of both the viscoelastiticity and microstucture of reconstituted silks that are being utilized as tissue scaffolds. This work is supported by a grant from the AFOSR FA9550-07-1-0130.

Along the Silk Road: People, Interaction, and Cultural Exchange. A Social Studies Unit Recommended for Grades 6-10.

ERIC Educational Resources Information Center

Stanford Univ., CA. Stanford Program on International and Cross Cultural Education.

This curriculum unit introduces students to the travelers and traders from the early part of the Han-Roman times up to the 14th century who took great risks in pursuit of silk. A variety of activities explore the development of the Silk Road trade routes, including journal writing, small group reading and writing activities, role play and…

Biomechanics of Spider Silks

DTIC Science & Technology

2006-03-02

observed attachment to the sericin coat (sem picture above) and slippage of the silk fibroin fibres. Hence it appears that choosing silk cocoon thin...several thick layers of sericin coating 9,10. Both fibroin and sericin are proteins, but of very different composition and properties 𔃺. The two brins...produced and coated in separate ducts, are pressed together while still inside the animal; the sericin hardens in air and typically on the cocoon to

Natural Materials, Systems & Extremophiles

DTIC Science & Technology

2012-03-06

system. Linked: FY11 AFRL/RX pgm • Structural Coloration – new area, several PIs moving in and out; MURI (Harvard) • Biopolymers – Mainly silk but...looking at other biopolymers . The silk work is well integrated with AFRL; many exchanges of personnel & material. Some PIs moving out with...it pertains to marking items. • Silk – DARPA has contributed to my existing program. ARO has a single grantee. ONR funds a single investigator. NSF

Optics of Spider Sticky Orb Webs

DTIC Science & Technology

2011-01-01

biopolymer which is almost exclusively protein with repeated sequences of the amino acids glycine and alanine [16]. The capture silk is spiraled...Herberstein, M. E., Craig, C. L. and Separovic, F., "Solid-state NMR relaxation studies of Australian spider silks ", Biopolymers 61, 287-297 (2002). [17... silks , scattering from rough/structured surfaces and thin film effects as the primary causes. We report systematic studies carried out using the

Spider Silk: From Protein-Rich Gland Fluids to Diverse Biopolymer Fibers

DTIC Science & Technology

2016-01-06

characterize the protein-rich fluid in the various spider silk producing glands. We have been using a battery of magnetic resonance methods including...solution and solid-state nuclear magnetic resonance (NMR) and micro imaging (MRI) in combination with wide angle and small angle X-ray diffraction...range of magnetic resonance methods. We successfully developed magnetic resonance imaging (MRI) techniques with localized spectroscopy to probe the silk

Characterization of Natural Dyes and Traditional Korean Silk Fabric by Surface Analytical Techniques.

PubMed

Lee, Jihye; Kang, Min Hwa; Lee, Kang-Bong; Lee, Yeonhee

2013-05-15

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) and X-ray photoelectron spectroscopy (XPS) are well established surface techniques that provide both elemental and organic information from several monolayers of a sample surface, while also allowing depth profiling or image mapping to be carried out. The static TOF-SIMS with improved performances has expanded the application of TOF-SIMS to the study of a variety of organic, polymeric and biological materials. In this work, TOF-SIMS, XPS and Fourier Transform Infrared (FTIR) measurements were used to characterize commercial natural dyes and traditional silk fabric dyed with plant extracts dyes avoiding the time-consuming and destructive extraction procedures necessary for the spectrophotometric and chromatographic methods previously used. Silk textiles dyed with plant extracts were then analyzed for chemical and functional group identification of their dye components and mordants. TOF-SIMS spectra for the dyed silk fabric showed element ions from metallic mordants, specific fragment ions and molecular ions from plant-extracted dyes. The results of TOF-SIMS, XPS and FTIR are very useful as a reference database for comparison with data about traditional Korean silk fabric and to provide an understanding of traditional dyeing materials. Therefore, this study shows that surface techniques are useful for micro-destructive analysis of plant-extracted dyes and Korean dyed silk fabric.

Neural Responses to Electrical Stimulation on Patterned Silk Films

PubMed Central

Hronik-Tupaj, Marie; Raja, Waseem Khan; Tang-Schomer, Min; Omenetto, Fiorenzo G.; Kaplan, David L.

2013-01-01

Peripheral nerve injury is a critical issue for trauma patients. Following injury, incomplete axon regeneration or misguided axon innervation into tissue will result in loss of sensory and motor functions. The objective of this study was to examine axon outgrowth and axon alignment in response to surface patterning and electrical stimulation. To accomplish our objective, metal electrodes with dimensions of 1.5 mm × 4 cm, were sputter coated onto micropatterned silk protein films, with surface grooves 3.5 μm wide × 500 nm deep. P19 neurons were seeded on the patterned electronic silk films and stimulated at 120 mV, 1 kHz, for 45 minutes each day for 7 days. Responses were compared to neurons on flat electronic silk films, patterned silk films without stimulation, and flat silk films without stimulation. Significant alignment was found on the patterned film groups compared to the flat film groups. Axon outgrowth was greater (p < 0.05) on electronic films on day 5 and day 7 compared to the unstimulated groups. In conclusion, electrical stimulation, at 120 mV, 1 kHz, for 45 minutes daily, in addition to surface patterning, of 3.5 μm wide × 500 nm deep grooves, offered control of nerve axon outgrowth and alignment. PMID:23401351

Sericin Composition in the Silk of Antheraea yamamai.

PubMed

Zurovec, Michal; Yonemura, Naoyuki; Kludkiewicz, Barbara; Sehnal, František; Kodrik, Dalibor; Vieira, Ligia Cota; Kucerova, Lucie; Strnad, Hynek; Konik, Peter; Sehadova, Hana

2016-05-09

The silks produced by caterpillars consist of fibroin proteins that form two core filaments, and sericin proteins that seal filaments into a fiber and conglutinate fibers in the cocoon. Sericin genes are well-known in Bombyx mori (Bombycidae) but have received little attention in other insects. This paper shows that Antheraea yamamai (Saturniidae) contains five sericin genes very different from the three sericin genes of B. mori. In spite of differences, all known sericins are characterized by short exons 1 and 2 (out of 3-12 exons), expression in the middle silk gland section, presence of repeats with high contents of Ser and charged amino acid residues, and secretion as a sticky silk component soluble in hot water. The B. mori sericins represent tentative phylogenetic lineages (I) BmSer1 and orthologs in Saturniidae, (II) BmSer2, and (III) BmSer3 and related sericins of Saturniidae and of the pyralid Galleria mellonella. The lineage (IV) seems to be limited to Saturniidae. Concerted evolution of the sericin genes was apparently associated with gene amplifications as well as gene loses. Differences in the silk fiber morphology indicate that the cocktail of sericins linking the filaments and coating the fiber is modified during spinning. Silks are composite biomaterials of conserved function in spite of great diversity of their composition.

Subchronic toxicity study of corn silk with rats.

PubMed

Wang, Cuina; Zhang, Tiehua; Liu, Jun; Lu, Shuang; Zhang, Cheng; Wang, Erlei; Wang, Zuozhao; Zhang, Yan; Liu, Jingbo

2011-09-01

Corn silk is a traditional herbal medicine in China, which has been used in many parts of the world for the treatment of edema as well as for cystitis, gout, kidney stones, nephritis, prostatitis and similar ailments. However, there is little scientific evidence about its safety. As a part of its safety assessment, a subchronic toxicity was performed in this paper. The subchronic toxicity was investigated in male and female Wistar rats by dietary administration at concentrations of 0.5%, 2.0% and 8.0% (w/w) for 90 days. Overall health, body weight, food consumption, hematology, blood chemistry, organ weights, gross and microscopic appearance of tissues were compared between test and control groups. A number of significant differences were seen between groups, but none of them was considered to be adverse. Based on the present study, the no-observed-adverse-effect level (NOAEL) of corn silk is at least 8.0% which corresponds to a mean daily corn silk intake of approximately 9.354 and 10.308 g/day/kg body weight for males and females, respectively. The results obtained in the present study suggest that consumption of corn silk has no adverse effects and support the safety of corn silk for humans. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

Silk-ionomer and silk-tropoelastin hydrogels as charged three-dimensional culture platforms for the regulation of hMSC response.

PubMed

Calabrese, Rossella; Raia, Nicole; Huang, Wenwen; Ghezzi, Chiara E; Simon, Marc; Staii, Cristian; Weiss, Anthony S; Kaplan, David L

2017-09-01

The response of human bone marrow-derived mesenchymal stem cells (hMSCs) encapsulated in three-dimensional (3D) charged protein hydrogels was studied. Combining silk fibroin (S) with recombinant human tropoelastin (E) or silk ionomers (I) provided protein composite alloys with tunable physicochemical and biological features for regulating the bioactivity of encapsulated hMSCs. The effects of the biomaterial charges on hMSC viability, proliferation and chondrogenic or osteogenic differentiation were assessed. The silk-tropoelastin or silk-ionomers hydrogels supported hMSC viability, proliferation and differentiation. Gene expression of markers for chondrogenesis and osteogenesis, as well as biochemical and histological analysis, showed that hydrogels with different S/E and S/I ratios had different effects on cell fate. The negatively charged hydrogels upregulated hMSC chondrogenesis or osteogenesis, with or without specific differentiation media, and hydrogels with higher tropoelastin content inhibited the differentiation potential even in the presence of the differentiation media. The results provide insight on charge-tunable features of protein-based biomaterials to control hMSC differentiation in 3D hydrogels, as well as providing a new set of hydrogels for the compatible encapsulation and utility for cell functions. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Shape Memory Silk Protein Sponges for Minimally Invasive Tissue Regeneration.

PubMed

Brown, Joseph E; Moreau, Jodie E; Berman, Alison M; McSherry, Heather J; Coburn, Jeannine M; Schmidt, Daniel F; Kaplan, David L

2017-01-01

Porous silk protein scaffolds are designed to display shape memory characteristics and volumetric recovery following compression. Two strategies are utilized to realize shape recovery: addition of hygroscopic plasticizers like glycerol, and tyrosine modifications with hydrophilic sulfonic acid chemistries. Silk sponges are evaluated for recovery following 80% compressive strain, total porosity, pore size distribution, secondary structure development, in vivo volume retention, cell infiltration, and inflammatory responses. Glycerol-modified sponges recover up to 98.3% of their original dimensions following compression, while sulfonic acid/glycerol modified sponges swell in water up to 71 times their compressed volume, well in excess of their original size. Longer silk extraction times (lower silk molecular weights) and higher glycerol concentrations yielded greater flexibility and shape fidelity, with no loss in modulus following compression. Sponges are over 95% porous, with secondary structure analysis indicating glycerol-induced β-sheet physical crosslinking. Tyrosine modifications with sulfonic acid interfere with β-sheet formation. Glycerol-modified sponges exhibit improved rates of cellular infiltration at subcutaneous implant sites with minimal immune response in mice. They also degrade more rapidly than unmodified sponges, a result posited to be cell-mediated. Overall, this work suggests that silk sponges may be useful for minimally invasive deployment in soft tissue augmentation procedures. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

3D Printing of Hierarchical Silk Fibroin Structures.

PubMed

Sommer, Marianne R; Schaffner, Manuel; Carnelli, Davide; Studart, André R

2016-12-21

Like many other natural materials, silk is hierarchically structured from the amino acid level up to the cocoon or spider web macroscopic structures. Despite being used industrially in a number of applications, hierarchically structured silk fibroin objects with a similar degree of architectural control as in natural structures have not been produced yet due to limitations in fabrication processes. In a combined top-down and bottom-up approach, we exploit the freedom in macroscopic design offered by 3D printing and the template-guided assembly of ink building blocks at the meso- and nanolevel to fabricate hierarchical silk porous materials with unprecedented structural control. Pores with tunable sizes in the range 40-350 μm are generated by adding sacrificial organic microparticles as templates to a silk fibroin-based ink. Commercially available wax particles or monodisperse polycaprolactone made by microfluidics can be used as microparticle templates. Since closed pores are generated after template removal, an ultrasonication treatment can optionally be used to achieve open porosity. Such pore templating particles can be further modified with nanoparticles to create a hierarchical template that results in porous structures with a defined nanotopography on the pore walls. The hierarchically porous silk structures obtained with this processing technique can potentially be utilized in various application fields from structural materials to thermal insulation to tissue engineering scaffolds.

Glycerol-plasticised silk membranes made using formic acid are ductile, transparent and degradation-resistant.

PubMed

Allardyce, Benjamin J; Rajkhowa, Rangam; Dilley, Rodney J; Redmond, Sharon L; Atlas, Marcus D; Wang, Xungai

2017-11-01

Regenerated silk fibroin membranes tend to be brittle when dry. The use of plasticisers such as glycerol improve membrane ductility, but, when combined with aqueous processing, can lead to a higher degradation rate than solvent-annealed membranes. This study investigated the use of formic acid as the solvent with glycerol to make deformable yet degradation-resistant silk membranes. Here we show that membranes cast using formic acid had low light scattering, with a diffuse transmittance of less than 5% over the visible wavelengths, significantly lower than the 20% transmittance of aqueous derived silk/glycerol membranes. They had 64% β-sheet content and lost just 30% of the initial silk weight over 6h when tested with an accelerated enzymatic degradation assay, in comparison the aqueous membranes completely degraded within this timeframe. The addition of glycerol also improved the maximum elongation of formic acid derived membranes from under 3% to over 100%. They also showed good cytocompatibility and supported the adhesion and migration of human tympanic membrane keratinocytes. Formic acid based, silk/glycerol membranes may be of great use in medical applications such as repair of tympanic membrane perforation or ocular applications where transparency and resistance to enzymatic degradation are important. Copyright © 2017 Elsevier B.V. All rights reserved.

Processing and characterisation of a novel electropolymerized silk fibroin hydrogel membrane

PubMed Central

Wang, Hai-Yan; Zhang, Yu-Qing

2014-01-01

Silk fibroin can be made into various forms of biocompatible medical materials, including hydrogel due to its excellent properties. Here, we report a novel method for the preparation of electropolymerized silk fibroin hydrogel membrane (ESFHM), which is formed on a nanoporous film as a barrier using a homemade device at a higher DC voltage. Regenerated silk fibroin solution in Tris buffer (pH 6.55–7.55) was added into a reservoir with a negative charge, and the silk molecules migrated toward the positive charge at 80VDC, resulting in the formation of the ESFHM on the barrier film. Barrier film with a MWCO of 10 kDa is favourable to the formation of the ESFHM. Semi-transparent ESFHM with a swelling ratio of 1056.4% predominantly consisted of a mixture of β-sheets and α-helix crystalline structures. SEM studies revealed that the ESFHM consisted of a 3D mesh structure woven by a chain of silk fibroin nanoparticles with a size of approximately 30 nanometres, similar to a pearl necklace. In vitro studies indicated that the ESFHM was degradable and was sufficient for cell adhesion and growth. Thus, ESFHM is a promising candidate for loading bioactive protein and appropriate cells, as artificial skin or for use in transplantation. PMID:25154713

Optics of spider "sticky" orb webs

NASA Astrophysics Data System (ADS)

Kane, Deb M.; Staib, Gregory R.; Naidoo, Nishen; Little, Douglas J.; Herberstein, Marie E.

2011-04-01

Spider orb webs are known to produce colour displays in nature, both in reflection and transmission of sunlight, under certain illumination conditions. The cause of these colours has been the subject of speculation since the time of Newton. It has also been the topic of observational interpretation and some experiment which has proposed diffraction by the fine silks, scattering from rough/structured surfaces and thin film effects as the primary causes. We report systematic studies carried out using the silks of Australian orb web weaving spiders. Studies of both white light and laser light scattering/propagation by natural spider silks have definitively determined the primary cause of the colour displays is rainbows that can be understood by the application of geometric optics combined with new knowledge of the optical properties of the spider web strands, silks, and proteins as optical materials. Additionally, a range of microscopies (optical, AFM, optical surface profiling) show the silks to be optically flat. Overall, spider silks emerge as fascinating optical materials with high dispersion, high birefringence and the potential for future research to show they have high nonlinear optical coefficients. Their importance as a bioinspiration in optics is only just beginning to be realised. Their special optical properties have been achieved by ~136 million years of evolution driven by the need for the web to evade detection by insect prey.

Quantifying Osteogenic Cell Degradation of Silk Biomaterials

PubMed Central

Sengupta, Sejuti; Park, Sang-Hyug; Seok, Gil Eun; Patel, Atur; Numata, Keiji; Lu, Chia-Li; Kaplan, David L.

2010-01-01

The degradation of silk protein films by human mesenchymal stem cells (hMSCs), osteoblasts and osteoclasts, cells involved in osteogenic functions in normal and diseased bone, was assessed in vitro. The involvement of specific matrix metalloproteinases (MMPs) and integrin signaling in the degradation process was determined. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to quantitatively compare degradation by the different cell types using surface patterned silk films. Osteoblasts and osteoclasts demonstrated significant degradation of the silk films in vitro in comparison to the hMSCs and the film controls without cells. The osteoclasts degraded the silk films the most and also generated the highest level of MMPs 1 and 2. The osteoblasts upregulated integrins α5 and β1 while the osteoclasts upregulated integrins α2 and β1. There was significant contrast in responses on the silk matrices between osteogenic cells vs undifferentiated hMSCs to illustrate in vitro the role of cell type on matrix remodeling. These are important issues in matching biomaterial matrix features and studies in vitro to remodeling in vivo, in both normal and disease tissue systems. Cell populations and niche factors impact tissue regeneration, wound healing and physiological state and the ability to better understand the role of different cell types is critical to overall regenerative outcomes. PMID:21105641

Identification and quantification and antioxidant activity of flavonoids in different strains of silk cocoon, Bombyx mori.

PubMed

Napavichayanun, Supamas; Lutz, Oliver; Fischnaller, Martin; Jakschitz, Thomas; Bonn, Günther; Aramwit, Pornanong

2017-10-01

Silk cocoon is produced from silkworm (Bombyx mori) to protect itself from outer environment. Various strains of cocoon contain different forms and amounts of flavonoids, which may affect on their antioxidant activity. Moreover, the extraction method would influence the amount of flavonoids extracted. Therefore, the objectives of this study were to identify and quantify the flavonoids in 3 strains of bivoltine Bombyx mori silk cocoon (Chul 1/1; white cocoon, Chul 3/2; greenish cocoon, and Chul 4/2; yellow cocoon) extracted by 6 different solvents including acetone, ethyl acetate, dimethyl sulfoxide (DMSO), ethanol, methanol, and purified water. The flavonoids extracted were identified and quantified by liquid chromatography-mass spectrometry (LC-MS). The antioxidant activity of flavonoids extracted was also investigated by visible spectroscopy at 517 nm. The results showed that Chul 3/2 silk cocoon contained the highest amount of flavonoids. Purified water seemed to be the best solvent that preserved most antioxidant activity of the flavonoids extracted. Flavonoids in Chul 1/1 and Chul 4/2 silk cocoon were rarely found, however they contained some antioxidant activities. The data from this study can provide basic information for flavonoid extraction from silk cocoon which can also apply for other flavonoid-containing natural biomaterials. Copyright © 2017 Elsevier Inc. All rights reserved.

Porous CaP/silk composite scaffolds to repair femur defects in an osteoporotic model

PubMed Central

Cheng, Ning; Dai, Jing; Cheng, Xiangrong; Li, Shu’e; Miron, Richard J.; Wu, Tao; Chen, Wenli; Zhang, Yufeng

2018-01-01

The most common complication for patients with postmenopausal osteoporosis is bone-related defects and fractures. While routine medication has a high probability of undesirable side effects, new approaches have aimed to develop regeneration procedures that stimulate new bone formation while reversing bone loss. Recently, we have synthesized a new hybrid CaP/silk scaffold with a CaP-phase distribution and pore architecture better suited to facilitate cell differentiation and bone formation. The aim of the present study was to compare the involved remodeling process and therapeutic effect of porous CaP/silk composite scaffolds upon local implantation into osteoporotic defects. Wistar rats were used to induce postmenopausal osteoporotic model by bilateral ovariectomy. The pure silk and hybrid CaP/silk scaffolds were implanted into critical sized defects created in distal femoral epiphysis. After 14 and 28 days, the in vivo osteogenetic efficiency was evaluated by μCT analysis, hematoxylin and eosin staining, Safranin O staining, tartrate-resistant acid phosphatase staining, and immunohistochemical assessment. Animals with or without critical-sized defects were used as drill or blank controls, respectively. The osteoporotic defect model was well established with significantly decreased μCT parameters of BV/TV, Tb.N and increased Tb.Sp, porosity, combined with changes in histological observations. During the healing process, the critical-sized drill control defects failed to regenerate appreciable bone tissue, while more significantly increased bone formation and mineralization with dynamic scaffold degradation and decreased osteoclastic bone resorption could be detected within defects with hybrid CaP/silk scaffolds compared to pure silk scaffolds. PMID:23674058

Porous CaP/silk composite scaffolds to repair femur defects in an osteoporotic model.

PubMed

Cheng, Ning; Dai, Jing; Cheng, Xiangrong; Li, Shu'e; Miron, Richard J; Wu, Tao; Chen, Wenli; Zhang, Yufeng; Shi, Bin

2013-08-01

The most common complication for patients with postmenopausal osteoporosis is bone-related defects and fractures. While routine medication has a high probability of undesirable side effects, new approaches have aimed to develop regeneration procedures that stimulate new bone formation while reversing bone loss. Recently, we have synthesized a new hybrid CaP/silk scaffold with a CaP-phase distribution and pore architecture better suited to facilitate cell differentiation and bone formation. The aim of the present study was to compare the involved remodeling process and therapeutic effect of porous CaP/silk composite scaffolds upon local implantation into osteoporotic defects. Wistar rats were used to induce postmenopausal osteoporotic model by bilateral ovariectomy. The pure silk and hybrid CaP/silk scaffolds were implanted into critical sized defects created in distal femoral epiphysis. After 14 and 28 days, the in vivo osteogenetic efficiency was evaluated by μCT analysis, hematoxylin and eosin staining, Safranin O staining, tartrate-resistant acid phosphatase staining, and immunohistochemical assessment. Animals with or without critical-sized defects were used as drill or blank controls, respectively. The osteoporotic defect model was well established with significantly decreased μCT parameters of BV/TV, Tb.N and increased Tb.Sp, porosity, combined with changes in histological observations. During the healing process, the critical-sized drill control defects failed to regenerate appreciable bone tissue, while more significantly increased bone formation and mineralization with dynamic scaffold degradation and decreased osteoclastic bone resorption could be detected within defects with hybrid CaP/silk scaffolds compared to pure silk scaffolds.

High-throughput sequencing of small RNAs from pollen and silk and characterization of miRNAs as candidate factors involved in pollen-silk interactions in maize.

PubMed

Li, Xiao Ming; Sang, Ya Lin; Zhao, Xiang Yu; Zhang, Xian Sheng

2013-01-01

In angiosperms, successful pollen-pistil interactions are the prerequisite and guarantee of subsequent fertilization and seed production. Recent profile analyses have helped elucidate molecular mechanisms underlying these processes at both transcriptomic and proteomic levels, but the involvement of miRNAs in pollen-pistil interactions is still speculative. In this study, we sequenced four small RNA libraries derived from mature pollen, in vitro germinated pollen, mature silks, and pollinated silks of maize (Zea mays L.). We identified 161 known miRNAs belonging to 27 families and 82 novel miRNAs. Of these, 40 conserved and 16 novel miRNAs showed different expression levels between mature and germinated pollen, and 30 conserved and eight novel miRNAs were differentially expressed between mature and pollinated silks. As candidates for factors associated with pollen-silk (pistil) interactions, expression patterns of the two sets of differentially expressed miRNAs were confirmed by stem-loop real-time RT-PCR. Transcript levels of 22 predicted target genes were also validated using real-time RT-PCR; most of these exhibited expression patterns contrasting with those of their corresponding miRNAs. In addition, GO analysis of target genes of differentially expressed miRNAs revealed that functional categories related to auxin signal transduction and gene expression regulation were overrepresented. These results suggest that miRNA-mediated auxin signal transduction and transcriptional regulation have roles in pollen-silk interactions. The results of our study provide novel information for understanding miRNA regulatory roles in pollen-pistil interactions.

Effect of pH on polyethylene glycol (PEG)-induced silk microsphere formation for drug delivery.

PubMed

Wu, Jianbing; Xie, Xusheng; Zheng, Zhaozhu; Li, Gang; Wang, Xiaoqin; Wang, Yansong

2017-11-01

The effects of changing solution pH in the range of 3.6-10.0 during a one-step silk microsphere preparation process, by mixing silk and polyethylene glycol (PEG), was assessed. The microspheres prepared at low pH (3.6) showed a more homogeneous size (1-3μm) and less porous texture than those prepared at neutral pH. High pH (10.0) inhibited microsphere formation, yielding small and inhomogeneous microspheres. Compared to neutral pH, low pH also increased the content of silk crystalline β-sheet structure from approx. 30% to above 40%. As a result, the microspheres produced at low pH were more thermally stable as well as resistant to chemical (8M urea) and enzymatic (protease XIV) degradation when compared to microspheres prepared at neutral pH. Doxorubicin hydrochloride (DOX) and curcumin (CUR) were successfully loaded in silk microspheres via control of solution pH. The loading efficiency of DOX was approx. 95% at pH7.0 and approx. 60% for CUR at pH3.6, attributed to charge-charge interactions and hydrophobic interactions between the silk and drug molecules, respectively. When PBS, pH7.4, was used as a medium for release studies, the pH3.6 microspheres released both drugs more slowly than the pH7.0 microspheres, likely due to the high content of crystalline β-sheet structure that enhanced drug-silk interactions as well as restricted drug molecule diffusion. Copyright © 2017. Published by Elsevier B.V.