Compressive and swelling behavior of cuttlebone derived hydroxyapatite loaded PVA hydrogel implants for articular cartilage

NASA Astrophysics Data System (ADS)

Kumar, B. Y. Santosh; Kumar, G. C. Mohan; Isloor, Arun M.

2018-04-01

Developing a novel antibacterial, nontoxic and biocompatible hydrogel with superior physio mechanical properties is still becoming a challenge. Herein, we synthesize hydroxyapatite (HA) powder from cuttlefish bone and prepare a series of stiff, tough, high strength, biocompatible hydrogel reinforced with HA by integrating glutaraldehyde into PVA/HA. Powder was characterized by SEM and XRD. Compressive strength and swelling properties are studied and compare the results with the properties of healthy natural articular cartilage.

A Solid-State NMR Study of Selenium Substitution into Nanocrystalline Hydroxyapatite

PubMed Central

Kolmas, Joanna; Kuras, Marzena; Oledzka, Ewa; Sobczak, Marcin

2015-01-01

The substitution of selenium oxyanions in the hydroxyapatite structure was examined using multinuclear solid-state resonance spectroscopy (ssNMR). The study was supported by powder X-ray diffractometry (PXRD) and wavelength dispersion X-ray fluorescence (WD-XRF). Samples of pure hydroxyapatite (HA300) and selenate (HA300-1.2SeO4) or selenite (HA300-1.2SeO3) substituted hydroxyapatites were synthesized using the standard wet method and heated at 300 °C to remove loosely bonded water. PXRD data showed that all samples are single-phase, nanocrystalline hydroxyapatite. The incorporation of selenite and selenate ions affected the lattice constants. In selenium-containing samples the concentration of Se was very similar and amounted to 9.55% and 9.64%, for HA300-1.2SeO4 and HA300-1.2SeO3, respectively. PXRD and ssNMR data showed that the selenite doping significantly decreases the crystallite size and crystallinity degree. 31P and 1H NMR experiments demonstrated the developed surface hydrated layer in all samples, especially in HA300-1.2SeO3. 1H NMR studies showed the dehydroxylation of HA during the selenium oxyanions substitution and the existence of hydrogen bonding in structural hydroxyl group channels. 1H→77Se cross polarization NMR experiments indicated that selenites and selenates are located in the crystal lattice and on the crystal surface. PMID:25997001

Electrospinning of calcium carbonate fibers and their conversion to nanocrystalline hydroxyapatite.

PubMed

Holopainen, Jani; Santala, Eero; Heikkilä, Mikko; Ritala, Mikko

2014-12-01

Calcium carbonate (CaCO3) fibers were prepared by electrospinning followed by annealing. Solutions consisting of calcium nitrate tetrahydrate (Ca(NO3)2·4H2O) and polyvinylpyrrolidone (PVP) dissolved in ethanol or 2-methoxyethanol were used for the fiber preparation. By varying the precursor concentrations in the electrospinning solutions CaCO3 fibers with average diameters from 140 to 290 nm were obtained. After calcination the fibers were identified as calcite by X-ray diffraction (XRD). The calcination process was studied in detail with high temperature X-ray diffraction (HTXRD) and thermogravimetric analysis (TGA). The initially weak fiber-to-substrate adhesion was improved by adding a strengthening CaCO3 layer by spin or dip coating Ca(NO3)2/PVP precursor solution on the CaCO3 fibers followed by annealing of the gel formed inside the fiber layer. The CaCO3 fibers were converted to nanocrystalline hydroxyapatite (HA) fibers by treatment in a dilute phosphate solution. The resulting hydroxyapatite had a plate-like crystal structure with resemblance to bone mineral. The calcium carbonate and hydroxyapatite fibers are interesting materials for bone scaffolds and bioactive coatings. Copyright © 2014 Elsevier B.V. All rights reserved.

Biomineralization of hydroxyapatite in silver ion-exchanged nanocrystalline ZSM-5 zeolite using simulated body fluid.

PubMed

Kaur, Balwinder; Srivastava, Rajendra; Satpati, Biswarup; Kondepudi, Kanthi Kiran; Bishnoi, Mahendra

2015-11-01

Silver ion-exchanged nanocrystalline zeolite (Ag-Nano-ZSM-5) and silver ion-exchanged conventional zeolite (Ag-ZSM-5) were synthesized. Zeolites were incubated in simulated body fluid at 310K for different time periods to grow hydroxyapatite in their matrixes. Significant large amount of hydroxyapatite was grown in Ag-Nano-ZSM-5 matrix after incubation in simulated body fluid when compared to Ag-ZSM-5. The resultant material was characterized using X-ray diffraction, N2-adsorption, scanning/transmission electron microscopy, energy dispersive X-ray, and inductively coupled plasma analysis. Mechanical properties such as compressive modulus, compressive strength, and strain at failure of the parent materials were evaluated. Biocompatibility assays suggested that Ag-Nano-ZSM-5 and hydroxyapatite grown in Ag-Nano-ZSM-5 were compatible and did not impose any toxicity to RAW 264.7 cells macrophase and Caco2 cells suggesting considerable potential for biomedical applications such as bone implants. Copyright © 2015 Elsevier B.V. All rights reserved.

Clinical and radiographic evaluation of intrabony periodontal defect treatment by open flap debridement alone or in combination with nanocrystalline hydroxyapatite bone substitute.

PubMed

Pietruska, Małgorzata; Skurska, Anna; Pietruski, Jan; Dolińska, Ewa; Arweiler, Nicole; Milewski, Robert; Duraj, Ewa; Sculean, Anton

2012-11-01

The aim of this study has been to compare the clinical and radiographic outcome of periodontal intrabony defect treatment by open flap debridement alone or in combination with nanocrystalline hydroxyapatite bone substitute application. Thirty patients diagnosed with advanced periodontits were divided into two groups: the control group (OFD), in which an open flap debridement procedure was performed and the test group (OFD+NHA), in which defects were additionally filled with nanocrystalline hydroxyapatite bone substitute material. Plaque index (PI), gingival index (GI), bleeding on probing (BOP), pocket depth (PD), gingival recession (GR) and clinical attachment level (CAL) were measured prior to, then 6 and 12months following treatment. Radiographic depth and width of defects were also evaluated. There were no differences in any clinical and radiographic parameters between the examined groups prior to treatment. After treatment, BOP, GI, PD, CAL, radiographic depth and width parameter values improved statistically significantly in both groups. The PI value did not change, but the GR value increased significantly after treatment. There were no statistical differences in evaluated parameters between OFD and OFD+NHA groups 6 and 12months after treatment. Within the limits of the study, it can be concluded that the additional use of nanocrystalline hydroxyapatite bone substitute material after open flap procedure does not improve clinical and radiographic treatment outcome. Copyright © 2012 Elsevier GmbH. All rights reserved.

A novel route for synthesis of nanocrystalline hydroxyapatite from eggshell waste.

PubMed

Siva Rama Krishna, D; Siddharthan, A; Seshadri, S K; Sampath Kumar, T S

2007-09-01

The eggshell waste has been value engineered to a nanocrystalline hydroxyapatite (HA) by microwave processing. To highlight the advantages of eggshell as calcium precursor in the synthesis of HA (OHA), synthetic calcium hydroxide was also used to form HA (SHA) following similar procedure and were compared with a commercially available pure HA (CHA). All the HAs were characterized by X-ray powder diffraction (XRD) method, Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and specific surface area measurements. Nanocrystalline nature of OHA is revealed through characteristic broad peaks in XRD patterns, platelets of length 33-50 nm and width 8-14 nm in TEM micrograph and size calculations from specific surface area measurements. FT-IR spectra showed characteristic bands of HA and additionally peaks of carbonate ions. The cell parameter calculations suggest the formation of carbonated HA of B-type. The OHA exhibits superior sinterability in terms of hardness and density than both SHA and CHA may be due to larger surface area of its spherulite structure. The in vitro dissolution study shows longer stability in phosphate buffer and cell culture test using osteoblast cells establishes biocompatibility of OHA.

Self-assembled high-strength hydroxyapatite/graphene oxide/chitosan composite hydrogel for bone tissue engineering.

PubMed

Yu, Peng; Bao, Rui-Ying; Shi, Xiao-Jun; Yang, Wei; Yang, Ming-Bo

2017-01-02

Graphene hydrogel has shown greatly potentials in bone tissue engineering recently, but it is relatively weak in the practical use. Here we report a facile method to synthesize high strength composite graphene hydrogel. Graphene oxide (GO), hydroxyapatite (HA) nanoparticles (NPs) and chitosan (CS) self-assemble into a 3-dimensional hydrogel with the assistance of crosslinking agent genipin (GNP) for CS and reducing agent sodium ascorbate (NaVC) for GO simultaneously. The dense and oriented microstructure of the resulted composite gel endows it with high mechanical strength, high fixing capacity of HA and high porosity. These properties together with the good biocompatibility make the ternary composite gel a promising material for bone tissue engineering. Such a simultaneous crosslinking and reduction strategy can also be applied to produce a variety of 3D graphene-polymer based nanocomposites for biomaterials, energy storage materials and adsorbent materials. Copyright © 2016 Elsevier Ltd. All rights reserved.

Photo-cross-linkable methacrylated gelatin and hydroxyapatite hybrid hydrogel for modularly engineering biomimetic osteon.

PubMed

Zuo, Yicong; Liu, Xiaolu; Wei, Dan; Sun, Jing; Xiao, Wenqian; Zhao, Huan; Guo, Likun; Wei, Qingrong; Fan, Hongsong; Zhang, Xingdong

2015-05-20

Modular tissue engineering holds great potential in regenerating natural complex tissues by engineering three-dimensional modular scaffolds with predefined geometry and biological characters. In modular tissue-like construction, a scaffold with an appropriate mechanical rigidity for assembling fabrication and high biocompatibility for cell survival is the key to the successful bioconstruction. In this work, a series of composite hydrogels (GH0, GH1, GH2, and GH3) based on a combination of methacrylated gelatin (GelMA) and hydroxyapatite (HA) was exploited to enhance hydrogel mechanical rigidity and promote cell functional expression for osteon biofabrication. These composite hydrogels presented a lower swelling ratio, higher mechanical moduli, and better biocompatibility when compared to the pure GelMA hydrogel. Furthermore, on the basis of the composite hydrogel and photolithograph technology, we successfully constructed an osteon-like concentric double-ring structure in which the inner ring encapsulating human umbilical vascular endothelial cells (HUVECs) was designed to imitate blood vessel tubule while the outer ring encapsulating human osteoblast-like cells (MG63s) acts as part of bone. During the coculture period, MG63s and HUVECs exhibited not only satisfying growth status but also the enhanced genic expression of osteogenesis-related and angiogenesis-related differentiations. These results demonstrate this GelMA-HA composite hydrogel system is promising for modular tissue engineering.

Poly(vinyl alcohol) hydrogel coatings with tunable surface exposure of hydroxyapatite

PubMed Central

Moreau, David; Villain, Arthur; Ku, David N; Corté, Laurent

2014-01-01

Insufficient bone anchoring is a major limitation of artificial substitutes for connective osteoarticular tissues. The use of coatings containing osseoconductive ceramic particles is one of the actively explored strategies to improve osseointegration and strengthen the bone-implant interface for general tissue engineering. Our hypothesis is that hydroxyapatite (HA) particles can be coated robustly on specific assemblies of PVA hydrogel fibers for the potential anchoring of ligament replacements. A simple dip-coating method is described to produce composite coatings made of microscopic hydroxyapatite (HA) particles dispersed in a poly(vinyl alcohol) (PVA) matrix. The materials are compatible with the requirements for implant Good Manufacturing Practices. They are applied to coat bundles of PVA hydrogel fibers used for the development of ligament implants. By means of optical and electronic microscopy, we show that the coating thickness and surface state can be adjusted by varying the composition of the dipping solution. Quantitative analysis based on backscattered electron microscopy show that the exposure of HA at the coating surface can be tuned from 0 to over 55% by decreasing the weight ratio of PVA over HA from 0.4 to 0.1. Abrasion experiments simulating bone-implant contact illustrate how the coating cohesion and wear resistance increase by increasing the content of PVA relative to HA. Using pullout experiments, we find that these coatings adhere well to the fiber bundles and detach by propagation of a crack inside the coating. These results provide a guide to select coated implants for anchoring artificial ligaments. PMID:25482413

Excitation of luminescence of the nanoporous bioactive nanocrystalline carbonate-substituted hydroxyapatite for early tooth disease detection

NASA Astrophysics Data System (ADS)

Goloshchapov, D. L.; Minakov, D. A.; Domashevskaya, E. P.; Seredin, P. V.

This paper deals with the luminescence characteristics of an analogue of the mineral component of dental enamel of the nanocrystalline B-type carbonate-substituted hydroxyapatite (CHAP) with 3D defects (i.e. nanopores of ∼2-5 nm) on the nanocrystalline surface. The laser-induced luminescence (LIL) of the synthesized CHAP samples was in the range of ∼515 nm (∼2.4 eV) and is due to CO3 groups replacing the PO4 group. It was found that the intensity of the luminescence of the CHAP is caused by structurally incorporated CO3 groups in the HAP structure. Furthermore, the intensity of the luminescence also decreases as the number of the above intracentre defects (CO3) in the apatite structure declines. These results are potentially promising for developing the foundations for precise methods for the early detection of caries in human solid dental tissue.

In situ synthesis of bilayered gradient poly(vinyl alcohol)/hydroxyapatite composite hydrogel by directional freezing-thawing and electrophoresis method.

PubMed

Su, Cui; Su, Yunlan; Li, Zhiyong; Haq, Muhammad Abdul; Zhou, Yong; Wang, Dujin

2017-08-01

Bilayered poly(vinyl alcohol) (PVA)/hydroxyapatite (HA) composite hydrogels with anisotropic and gradient mechanical properties were prepared by the combination of directional freezing-thawing (DFT) and electrophoresis method. Firstly, PVA hydrogels with aligned channel structure were prepared by the DFT method. Then, HA nanoparticles were in situ synthesized within the PVA hydrogels via electrophoresis. By controlling the time of the electrophoresis process, a bilayered gradient hydrogel containing HA particles in only half of the gel region was obtained. The PVA/HA composite hydrogel exhibited gradient mechanical strength depending on the distance to the cathode. The gradient initial tensile modulus ranging from 0.18MPa to 0.27MPa and the gradient initial compressive modulus from 0.33MPa to 0.51MPa were achieved. The binding strength of the two regions was relatively high and no apparent internal stress or defect was observed at the boundary. The two regions of the bilayered hydrogel also showed different osteoblast cell adhesion properties. Copyright © 2017 Elsevier B.V. All rights reserved.

Preparation and bioactive properties of nanocrystalline hydroxyapatite thin films obtained by conversion of atomic layer deposited calcium carbonate.

PubMed

Holopainen, Jani; Kauppinen, Kyösti; Mizohata, Kenichiro; Santala, Eero; Mikkola, Esa; Heikkilä, Mikko; Kokkonen, Hanna; Leskelä, Markku; Lehenkari, Petri; Tuukkanen, Juha; Ritala, Mikko

2014-09-01

Nanocrystalline hydroxyapatite thin films were fabricated on silicon and titanium by atomic layer deposition (ALD) of CaCO3 and its subsequent conversion to hydroxyapatite by diammonium hydrogen phosphate (DAP) solution. The effects of conversion process parameters to crystallinity and morphology of the films were examined. DAP concentration was found to be critical in controlling the crystal size and homogeneity of the films. The hydroxyapatite phase was identified by XRD. ToF-elastic recoil detection analysis studies revealed that the films are calcium deficient in relation to hydroxyapatite with a Ca/P ratio of 1.39 for films converted with 0.2 M DAP at 95 °C. The coatings prepared on titanium conformally follow the rough surface topography of the substrate, verifying that the good step coverage of the ALD method was maintained in the conversion process. The dissolution tests revealed that the coating was nondissolvable in the cell culture medium. Annealing the coated sample at 700 °C for 1 h seemed to enhance its bonding properties to the substrate. Also, the biocompatibility of the coatings was confirmed by human bone marrow derived cells in vitro. The developed method provides a new possibility to produce thin film coatings on titanium implants with bone-type hydroxyapatite that is biocompatible with human osteoblasts and osteoclasts.

Synthesis of nano-crystalline hydroxyapatite and ammonium sulfate from phosphogypsum waste

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

Mousa, Sahar, E-mail: dollyriri@yahoo.com; King Abdulaziz University, Science and Art College, Chemistry Department, Rabigh Campus, P.O. Box:344, Postal code: 21911 Rabigh; Hanna, Adly

2013-02-15

Graphical abstract: TEM micrograph of dried HAP at 800 °C. -- Abstract: Phosphogypsum (PG) waste which is derived from phosphoric acid manufacture by using wet method was converted into hydroxyapatite (HAP) and ammonium sulfate. Very simple method was applied by reacting PG with phosphoric acid in alkaline medium with adjusting pH using ammonia solution. The obtained nano-HAP was dried at 80 °C and calcined at 600 °C and 900 °C for 2 h. Both of HAP and ammonium sulfate were characterized by X-ray diffraction (XRD) and infrared spectroscopy (IR) to study the structural evolution. The thermal behavior of nano-HAP wasmore » studied; the particle size and morphology were estimated by using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). All the results showed that HAP nano-crystalline and ammonium sulfate can successfully be produced from phosphogypsum waste.« less

A novel thermo-sensitive hydrogel based on thiolated chitosan/hydroxyapatite/beta-glycerophosphate.

PubMed

Liu, Xujie; Chen, Yan; Huang, Qianli; He, Wei; Feng, Qingling; Yu, Bo

2014-09-22

In order to get a water-soluble in situ gel-forming system, a thiolated chitosan, chitosan-4-thio-butylamidine (CS-TBA) conjugate was synthesized and used to replace the unmodified chitosan in the application of the in situ gel-forming system. A novel thermo-sensitive hydrogel was prepared based on CS-TBA/hydroxyapatite (HA)/beta-glycerophosphate disodium (β-GP). The gel formation, rheological properties, morphology, degradation, cytotoxicity, as well as protein release process of the novel gel system were investigated in this study. The CS-TBA/HA/β-GP gel showed a higher storage modulus (G') and loss modulus (G″) and a decreased bovine serum albumin (BSA) release rate which was maintained the protein release for a longer time compared with the unmodified chitosan (CS)/HA/β-GP gel, due to the existence of thiol groups and/or disulfide bonds. The CS-TBA/HA/β-GP gel has a porous structure with a uniform distribution of nano-hydroxyapatite, an appropriate degradation rate and low cytotoxicity, showing potential applications in drug delivery and tissue engineering. Copyright © 2014 Elsevier Ltd. All rights reserved.

Biocompatible nanocrystalline natural bonelike carbonated hydroxyapatite synthesized by mechanical alloying in a record minimum time.

PubMed

Lala, S; Brahmachari, S; Das, P K; Das, D; Kar, T; Pradhan, S K

2014-09-01

Single phase nanocrystalline biocompatible A-type carbonated hydroxyapatite (A-cHAp) powder has been synthesized by mechanical alloying the stoichiometric mixture of CaCO3 and CaHPO4.2H2O powders in open air at room temperature within 2h of milling. The A-type carbonation in HAp is confirmed by FTIR analysis. Structural and microstructure parameters of as-milled powders are obtained from both Rietveld's powder structure refinement analysis and transmission electron microscopy. Size and lattice strain of nanocrystalline HAp particles are found to be anisotropic in nature. Mechanical alloying causes amorphization of a part of crystalline A-cHAp which is analogous to native bone mineral. Some primary bond lengths of as-milled samples are critically measured. MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay test reveals high percentage of cell viability and hence confirms the biocompatibility of the sample. The overall results indicate that the processed A-cHAp has a chemical composition very close to that of biological apatite. Copyright © 2014 Elsevier B.V. All rights reserved.

Micro- and nano-hydroxyapatite as active reinforcement for soft biocomposites.

PubMed

Munarin, F; Petrini, P; Gentilini, R; Pillai, R S; Dirè, S; Tanzi, M C; Sglavo, V M

2015-01-01

Pectin-based biocomposite hydrogels were produced by internal gelation, using different hydroxyapatite (HA) powders from commercial source or synthesized by the wet chemical method. HA possesses the double functionality of cross-linking agent and inorganic reinforcement. The mineralogical composition, grain size, specific surface area and microstructure of the hydroxyapatite powders are shown to strongly influence the properties of the biocomposites. Specifically, the grain size and specific surface area of the HA powders are strictly correlated to the gelling time and rheological properties of the hydrogels at room temperature. Pectin pH is also significant for the formation of ionic cross-links and therefore for the hydrogels stability at higher temperatures. The obtained results point out that micrometric-size hydroxyapatite can be proposed for applications which require rapid gelling kinetics and improved mechanical properties; conversely the nanometric hydroxyapatite synthesized in the present work seems the best choice to obtain homogeneous hydrogels with more easily controlled gelling kinetics. Copyright © 2014 Elsevier B.V. All rights reserved.

[Ridge preservation with synthetic nanocrystalline hydroxyapatite reduces the severity of gingival invaginations-a prospective clinical study].

PubMed

Reichert, Christoph; Wenghoefer, Matthias; Kutschera, Eric; Götz, Werner; Jäger, Andreas

2014-01-01

Gingival invaginations develop after tooth extraction and subsequent orthodontic space closure. Aetiological factors and long-term effects of gingival invaginations on oral health are nearly unknown. In addition, preventive or therapeutic strategies are rare. This prospective clinical study employing the split mouth technique was performed to investigate the effect of extraction socket augmentation with a synthetic nanocrystalline hydroxyapatite (NanoBone(®) Artoss, Rostock, Germany) on the incidence and degree of gingival invaginations. A total of 10 orthodontic patients with need for symmetric premolar extractions offering a total of 28 extractions were included in this trial. The study plan provided one extraction site to be augmented with synthetic nanocrystalline hydroxyapatite (NanoBone(®)), the other served as control. After primary wound healing, space closure was performed under defined biomechanical conditions. After space closure was accomplished, occurrence and degree of gingival invaginations as well as probing depths of the adjacent teeth mesial and distal to the extractions were determined and dental radiographs were taken. The degree of gingival invaginations and probing depths mesial and distal of the extraction were significantly reduced on NanoBone(®) augmented extraction sites. In addition, 70% of the radiographs revealed translucent and hyperdense areas on the intervention side after space closure. Apical root resorption was found in 2 patients on both the NanoBone(®) side and the control side. Ridge preservation with NanoBone(®) appeared to reduce the severity of gingival invaginations. Further investigation on long-term effects is mandatory to eliminate the appearance of adverse effects.

Hydroxyapatite-coated double network hydrogel directly bondable to the bone: Biological and biomechanical evaluations of the bonding property in an osteochondral defect.

PubMed

Wada, Susumu; Kitamura, Nobuto; Nonoyama, Takayuki; Kiyama, Ryuji; Kurokawa, Takayuki; Gong, Jian Ping; Yasuda, Kazunori

2016-10-15

We have developed a novel hydroxyapatite (HAp)-coated double-network (DN) hydrogel (HAp/DN gel). The purpose of this study was to determine details of the cell and tissue responses around the implanted HAp/DN gel and to determine how quickly and strongly the HAp/DN gel bonds to the bone in a rabbit osteochondral defect model. Immature osteoid tissue was formed in the space between the HAp/DN gel and the bone at 2weeks, and the osteoid tissue was mineralized at 4weeks. The push-out load of the HAp/DN gel averaged 37.54N and 42.15N at 4 and 12weeks, respectively, while the push-out load of the DN gel averaged less than 5N. The bonding area of the HAp/DN gel to the bone was above 80% by 4weeks, and above 90% at 12weeks. This study demonstrated that the HAp/DN gel enhanced osseointegration at an early stage after implantation. The presence of nanoscale structures in addition to osseointegration of HAp promoted osteoblast adhesion onto the surface of the HAp/DN gel. The HAp/DN gel has the potential to improve the implant-tissue interface in next-generation orthopaedic implants such as artificial cartilage. Recent studies have reported the development of various hydrogels that are sufficiently tough for application as soft supporting tissues. However, fixation of hydrogels on bone surfaces with appropriate strength is a great challenge. We have developed a novel, tough hydrogel hybridizing hydroxyapatite (HAp/DN gel), which is directly bondable to the bone. The present study demonstrated that the HAp/DN gel enhanced osseointegration in the early stage after implantation. The presence of nanoscale structures in addition to the osseointegration ability of hydroxyapatite promoted osteoblast adhesion onto the surface of the HAp/DN gel. The HAp/DN gel has the potential to improve the implant-tissue interface in next-generation orthopaedic implants such as artificial cartilage. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Reactive hydroxyapatite fillers for pectin biocomposites.

PubMed

Munarin, Fabiola; Petrini, Paola; Barcellona, Giulia; Roversi, Tommaso; Piazza, Laura; Visai, Livia; Tanzi, Maria Cristina

2014-12-01

In this work, a novel injectable biocomposite hydrogel is produced by internal gelation, using pectin as organic matrix and hydroxyapatite either as crosslinking agent and inorganic reinforcement. Tunable gelling kinetics and rheological properties are obtained varying the hydrogels' composition, with the final aim of developing systems for cell immobilization. The reversibility by dissolution of pectin-hydroxyapatite hydrogels is achieved with saline solutions, to possibly accelerate the release of the cells or active agents immobilized. Texture analysis confirms the possibility of extruding the biocomposites from needles with diameters from 20 G to 30 G, indicating that they can be implanted with minimally-invasive approaches, minimizing the pain during injection and the side effects of the open surgery. L929 fibroblasts entrapped in the hydrogels survive to the immobilization procedure and exhibit high cell viability. On the overall, these systems result to be suitable supports for the immobilization of cells for tissue regeneration applications. Copyright © 2014 Elsevier B.V. All rights reserved.

Evaluation of BSA protein release from hollow hydroxyapatite microspheres into PEG hydrogel

PubMed Central

Fu, Hailuo; Rahaman, Mohamed N.; Brown, Roger F.; Day, Delbert E.

2013-01-01

Implants that simultaneously function as an osteoconductive matrix and as a device for local drug or growth factor delivery could provide an attractive system for bone regeneration. In our previous work, we prepared hollow hydroxyapatite (abbreviated HA) microspheres with a high surface area, mesoporous shell wall and studied the release of a model protein, bovine serum albumin (BSA), from the microspheres into phosphate-buffered saline (PBS). The present work is an extension of our previous work to study the release of BSA from similar HA microspheres into a biocompatible hydrogel, poly(ethylene glycol) (PEG). BSA-loaded HA microspheres were placed in a PEG solution which was rapidly gelled using ultraviolet radiation. The BSA release rate into the PEG hydrogel, measured using a spectrophotometric method, was slower than into PBS, and it was dependent on the initial BSA loading and on the microstructure of the microsphere shell wall. A total of 35–40% of the BSA initially loaded into the microspheres was released into PEG over ~14 days. The results indicate that these hollow HA microspheres have promising potential as an osteoconductive device for local drug or growth factor delivery in bone regeneration and in the treatment of bone diseases. PMID:23498254

Rheological, mechanical and degradable properties of injectable chitosan/silk fibroin/hydroxyapatite/glycerophosphate hydrogels.

PubMed

Wu, Jingjing; Liu, Jiaoyan; Shi, Yanmei; Wan, Ying

2016-12-01

Silk fibroin (SF) and hydroxyapatite (HA) were incorporated into chitosan/glycerophosphate (GP) system to prepare new types of hydrogels. The formulated chitosan/SF/GP and chitosan/SF/HA/GP solutions were found to be injectable at room temperature, and able to form into hydrogels at near-physiological temperature and pH. Rheological measurements showed that elastic modulus of certain chitosan/SF/GP and chitosan/SF/HA/GP gels could reach around 1.8 and 15kPa, respectively, and was much higher than their respective viscous modulus. Compressive measurements revealed that some chitosan/SF/GP and chitosan/SF/HA/GP gels had 8 and 20-fold modulus and strength higher than the chitosan/GP gel, respectively, confirming that compressive properties of these gels were greatly improved. Results obtained from in vivo degradation demonstrated that degradation endurance of the optimized chitosan/SF/GP and chitosan/SF/HA/GP gels was significantly enhanced as compared to the chitosan/GP gel, and the degradation rate of the gels could be regulated by the SF component alone or by the combination of SF and HA components. Copyright © 2016 Elsevier Ltd. All rights reserved.

Interconnectivity of macroporous molecularly imprinted polymers fabricated by hydroxyapatite-stabilized Pickering high internal phase emulsions-hydrogels for the selective recognition of protein.

PubMed

Sun, Yanhua; Li, Yuqing; Xu, Jiangfeng; Huang, Ling; Qiu, Tianyun; Zhong, Shian

2017-07-01

Hydroxyapatite hybridized molecularly imprinted polydopamine polymers with selective recognition of bovine hemoglobin (BHb) were successfully prepared via Pickering oil-in-water high internal phase emulsions-hydrogels and molecularly imprinting technique. The emulsions were stabilized by hydroxyapatite of which the wettability was modified by 3-methacryloxypropyltrimethoxysilane. The materials were characterized by SEM, IR and TGA. The results showed that the BHb imprinted polymers based on Pickering hydrogels (Hydro-MIPs) possess macropores ranging from 20μm to 50μm, and their large numbers of amino groups and hydroxyl groups result in a favorable adsorption capacity for BHb. The maximum adsorption capacity of Hydro-MIPs for BHb was 438mg/g, 3.27 times more than that of the non-imprinted polymers (Hydro-NIPs). The results indicated that Hydro-MIPs possessing well-defined hierarchical porous structures exhibited outstanding recognition behavior towards the target protein molecules. This work provided a promising alternative method for the fabrication of polymer materials with tunable and interconnected pores structures for the separation and purification of protein in vitro. Copyright © 2017. Published by Elsevier B.V.

Sinus Floor Elevation and Augmentation Using Synthetic Nanocrystalline and Nanoporous Hydroxyapatite Bone Substitute Materials: Preliminary Histologic Results.

PubMed

Belouka, Sofia-Maria; Strietzel, Frank Peter

To compare the tissue composition of augmented sites after using two different synthetic bone substitute materials, nanocrystalline and nanoporous hydroxyapatite (HA), for sinus floor elevation and augmentation. Forty-four patients received 88 titanium screw implants (Camlog Promote plus) of 4.3-mm diameter and 11- or 13-mm length, placed simultaneously during sinus floor elevation and augmentation. Nanocrystalline (Ostim) or nanoporous (NanoBone) HA were used exclusively. Bone substitute materials and implant lengths were allocated by randomization. Bone biopsy specimens were obtained from the former area of the lateral access window at implant exposure during healing abutment placement after 6 months. Biopsy specimens were prepared and examined histologically and histomorphometrically. All implants were osseointegrated at the time of exposure. Clinically and histologically, no signs of inflammation in the augmented sites were present. The histomorphometric analysis of 44 biopsy specimens revealed 31.8% ± 11.6% newly formed bone for sites augmented with nanocrystalline HA and 34.6% ± 9.2% for nanoporous HA (P = .467). The proportion of remaining bone substitute material was 28.4% ± 18.6% and 30% ± 13%, respectively (P = .453). The proportion of soft tissue within the biopsy specimens was 39.9% ± 11.1% and 35.4% ± 6.8%, respectively (P = .064). No significant differences were found between the area fractions of bone, bone substitute material, and soft tissue concerning the bone substitute material utilized. Within the present study, both synthetic bone substitute materials, nanocrystalline and nanoporous HA, were found to support bone formation in sinus floor elevation and augmentation procedures by osteoconductivity. They were not completely resorbed after 6 months. The amounts of newly formed bone, soft tissue, and bone substitute material remnants were found to be similar, indicating that both materials are likewise suitable for sinus floor elevation and

Structural characterization of nanocrystalline hydroxyapatite and adhesion of pre-osteoblast cells

NASA Astrophysics Data System (ADS)

Zhu, Xiaolong; Eibl, Oliver; Berthold, Christoph; Scheideler, Lutz; Geis-Gerstorfer, Jürgen

2006-06-01

Nanocrystalline hydroxyapatite (Nano HA), a prototype of minerals of bones and teeth, attracts increasing interest in medicine and dentistry. Different parameters for synthesis and post-treatment were investigated to determine their effects on crystallinity of nano HA, and in vitro cell responses to nano HA were studied. XRD and TEM analyses indicate that the crystallinity of nano HA synthesized by a chemical method was within the range of 15-50 nm, which is adapted to natural minerals of hard tissues. Increasing the ageing temperature significantly increased the crystallinity of nano HA, while lengthening the ageing time or varying the post-ageing drying process did not have any influence on its crystallinity. Nano HA annealed between 300 and 900 °C showed a small increase in crystallinity with increasing annealing temperature due to the long-range ordering effect. Cell attachment and spreading on nano HA were lower than those on pure titanium, and decreased as the crystallinity of nano HA increased. However, cells on nano HA demonstrated well-developed filopodia and lamelliopodia, which facilitate migration of the cells on it. This may benefit osteogenesis at the interface between bone and nano HA in vivo.

Influence of Dispersant and Heat Treatment on the Morphology of Nanocrystalline Hydroxyapatite

NASA Astrophysics Data System (ADS)

Pan, Yusong; Xiong, Dangsheng

2010-10-01

Natural biological hard tissues are biocomposites of proteins and hydroxyapatite (HA) with superior strength. Nanometer scale HAp is the key material to manufacture bone substitute. In this work, nano-sized HA particles were synthesized by a wet method using orthophosphoric acid and calcium hydroxide as raw materials. The prepared nanocrystalline HAp was characterized for its phase purity and nano-scale morphological structure by XRD, TEM, and FTIR. The influences of heat treatment temperature and dispersant on the properties of HAp were also investigated. The results indicated that nano-particles were pure single-phase HAp with a diameter of 25-70 nm and length of 50-180 nm depending on heat treatment temperature. The morphology and crystallite size of HAp change with heat treatment temperature. After heat treating, the crystallinity of these nano-particles increased and its morphology transformed from needle-like to sphere-like structure. The dispersant is beneficial to prevent the growth of HA particles and provide a uniform particle size distribution. Moreover, the HAp tends to form small agglomerates in the absence of dispersant.

Synthesis and antimicrobial activity of silver-doped hydroxyapatite nanoparticles.

PubMed

Ciobanu, Carmen Steluta; Iconaru, Simona Liliana; Chifiriuc, Mariana Carmen; Costescu, Adrian; Le Coustumer, Philippe; Predoi, Daniela

2013-01-01

The synthesis of nanosized particles of Ag-doped hydroxyapatite with antibacterial properties is of great interest for the development of new biomedical applications. The aim of this study was the evaluation of Ca(10-x)Ag(x)(PO4)6(OH)2 nanoparticles (Ag:HAp-NPs) for their antibacterial and antifungal activity. Resistance to antimicrobial agents by pathogenic bacteria has emerged in the recent years and became a major health problem. Here, we report a method for synthesizing Ag doped nanocrystalline hydroxyapatite. A silver-doped nanocrystalline hydroxyapatite was synthesized at 100°C in deionised water. Also, in this paper Ag:HAp-NPs are evaluated for their antimicrobial activity against gram-positive and gram-negative bacteria and fungal strains. The specific antimicrobial activity revealed by the qualitative assay is demonstrating that our compounds are interacting differently with the microbial targets, probably due to the differences in the microbial wall structures.

Synthesis and Antimicrobial Activity of Silver-Doped Hydroxyapatite Nanoparticles

PubMed Central

Ciobanu, Carmen Steluta; Iconaru, Simona Liliana; Chifiriuc, Mariana Carmen; Costescu, Adrian; Le Coustumer, Philippe; Predoi, Daniela

2013-01-01

The synthesis of nanosized particles of Ag-doped hydroxyapatite with antibacterial properties is of great interest for the development of new biomedical applications. The aim of this study was the evaluation of Ca10−xAgx(PO4)6(OH)2 nanoparticles (Ag:HAp-NPs) for their antibacterial and antifungal activity. Resistance to antimicrobial agents by pathogenic bacteria has emerged in the recent years and became a major health problem. Here, we report a method for synthesizing Ag doped nanocrystalline hydroxyapatite. A silver-doped nanocrystalline hydroxyapatite was synthesized at 100°C in deionised water. Also, in this paper Ag:HAp-NPs are evaluated for their antimicrobial activity against Gram-positive and Gram-negative bacteria and fungal strains. The specific antimicrobial activity revealed by the qualitative assay is demonstrating that our compounds are interacting differently with the microbial targets, probably due to the differences in the microbial wall structures. PMID:23509801

Differentiation of osteoclast precursors on gellan gum-based spongy-like hydrogels for bone tissue engineering.

PubMed

Maia, F Raquel; Musson, David S; Naot, Dorit; da Silva, Lucilia P; Bastos, Ana R; Costa, João B; Oliveira, Joaquim M; Correlo, Vitor M; Reis, Rui L; Cornish, Jillian

2018-03-16

Bone tissue engineering with cell-scaffold constructs has been attracting a lot of attention, in particular as a tool for the efficient guiding of new tissue formation. However, the majority of the current strategies used to evaluate novel biomaterials focus on osteoblasts and bone formation, while osteoclasts are often overlooked. Consequently, there is limited knowledge on the interaction between osteoclasts and biomaterials. In this study, the ability of spongy-like gellan gum and hydroxyapatite-reinforced gellan gum hydrogels to support osteoclastogenesis was investigated in vitro. First, the spongy-like gellan gum and hydroxyapatite-reinforced gellan gum hydrogels were characterized in terms of microstructure, water uptake and mechanical properties. Then, bone marrow cells isolated from the long bones of mice and cultured in spongy-like hydrogels were treated with 1,25-dihydroxyvitamin D3 to promote osteoclastogenesis. It was shown that the addition of HAp to spongy-like gellan gum hydrogels enables the formation of larger pores and thicker walls, promoting an increase in stiffness. Hydroxyapatite-reinforced spongy-like gellan gum hydrogels support the formation of the aggregates of tartrate-resistant acid phosphatase-stained cells and the expression of genes encoding DC-STAMP and Cathepsin K, suggesting the differentiation of bone marrow cells into pre-osteoclasts. The hydroxyapatite-reinforced spongy-like gellan gum hydrogels developed in this work show promise for future use in bone tissue scaffolding applications.

Development of a novel alginate-polyvinyl alcohol-hydroxyapatite hydrogel for 3D bioprinting bone tissue engineered scaffolds.

PubMed

Bendtsen, Stephanie T; Quinnell, Sean P; Wei, Mei

2017-05-01

Three-dimensional printed biomaterials used as personalized tissue substitutes have the ability to promote and enhance regeneration in areas of defected tissue. The challenge with 3D printing for bone tissue engineering remains the selection of a material with optimal rheological properties for printing in addition to biocompatibility and capacity for uniform cell incorporation. Hydrogel biomaterials may provide sufficient printability to allow cell encapsulation and bioprinting of scaffolds with uniform cell distribution. In this study, a novel alginate-polyvinyl alcohol (PVA)-hydroxyapatite (HA) hydrogel formulation with optimal rheological properties for 3D bioprinting of mouse calvaria 3T3-E1 (MC3T3) cells into scaffolds of high shape fidelity has been developed. A systematic investigation was conducted to determine the effect of varying concentrations of alginate, phosphate, calcium, and the PVA-HA suspension in the formulation on the resulting viscosity and thus printability of the hydrogel. HA, the main mineral component in natural bone, was incorporated into the hydrogel formulation to create a favorable bone-forming environment due to its excellent osteoconductivity. Degradation studies in α-MEM cell culture media showed that the 3D printed alginate-PVA-HA scaffolds remained in-tact for 14 days. MC3T3 cells were well distributed and encapsulated throughout the optimal hydrogel formulation and expressed high viability through the completion of the 3D printing process. Thus, the development of this novel, osteoconductive, biodegradable, alginate-PVA-HA formulation and its ability to 3D bioprint tissue engineered scaffolds make it a promising candidate for treating personalized bone defects. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1457-1468, 2017. © 2017 Wiley Periodicals, Inc.

Sinus lift using a nanocrystalline hydroxyapatite silica gel in severely resorbed maxillae: histological preliminary study.

PubMed

Canullo, Luigi; Dellavia, Claudia

2009-10-01

The aim of this preliminary study was to evaluate histologically a nanocrystalline hydroxyapatite silica gel in maxillary sinus floor grafting in severely resorbed maxillae. A total of 16 consecutive patients scheduled for sinus lift were recruited during this study. Patients were randomly divided in two groups, eight patients each. In both groups, preoperative residual bone level ranged between 1 and 3 mm (mean value of 2.03 mm). No membrane was used to occlude the buccal window. Second surgery was carried out after a healing period of 3 months in Group 1 and 6 months in Group 2. Using a trephine bur, one bone specimen was harvested from each augmented sinus and underwent histological and histomorphometric analysis. Histological analysis showed significant new bone formation and remodeling of the grafted material. In the cores obtained at 6 months, regenerated bone, residual NanoBone, and bone marrow occupied respectively 48 +/- 4.63%, 28 +/- 5.33%, and 24 +/- 7.23% of the grafted volume. In the specimens taken 3 months after grafting, mean new bone was 8 +/- 3.34%, mean NanoBone was 45 +/- 5.10%, and mean bone marrow was 47 +/- 6.81% of the bioptical volume. Within the limits of this preliminary prospective study, it was concluded that grafting of maxillary sinus using nanostructured hydroxyapatite silica gel as only bone filler is a reliable procedure also in critical anatomic conditions and after early healing period.

Histologic and histomorphometric evaluation of bone regeneration using nanocrystalline hydroxyapatite and human freeze-dried bone graft : An experimental study in rabbit.

PubMed

Sadeghi, Rokhsareh; Najafi, Mohammad; Semyari, Hassan; Mashhadiabbas, Fatemeh

2017-03-01

Bone regeneration is an important concern in periodontal treatment and implant dentistry. Different biomaterials and surgical techniques have been used for this purpose. The aim of the present study was to compare the effect of nanocrystalline hydroxyapatite and human freeze-dried bone graft (FDBG) in regeneration of rabbit calvarium bony defects by histologic and histomorphometric evaluation. In this experimental study, three similar defects, measuring 8 mm in diameter, were created in the calvaria of 16 white New Zealand rabbits. Two defects were filled with FDBG and nanocrystalline hydroxyapatite silica gel, while the other one remained unfilled to be considered as control. All the defects were covered with collagen membranes. During the healing period, two animals perished; so 14 rabbits were divided into two groups: half of them were euthanized after 6 weeks of healing and the other half after 12 weeks. The specimens were subjected to histologic and histomorphometric examinations for assessment of the following variables: percentage of bone formation and residual graft material, inflammation scores, patterns of bone formation and type of newly formed bone. The percentages of new bone formation after 6 weeks were 14.22 ± 7.85, 21.57 ± 6.91, and 20.54 ± 10.07% in FDBG, NanoBone, and control defects. These values were 27.54 ± 20.19, 23.86 ± 6.27, and 26.48 ± 14.18% in 12-week specimens, respectively. No significant differences were found in the amount of bone formation between the groups. With regard to inflammation, the control and NanoBone groups showed significantly less inflammation compared to FDBG at the 6-week healing phase (P = 0.04); this difference was not significant in the 12-week specimens. Based on the results of this experimental study, both NanoBone and FDBG exhibited a similar effect on bone formation.

Nanocrystalline hydroxyapatite ceramics prepared by hydrolysis in polyol medium

NASA Astrophysics Data System (ADS)

Mechay, Abderrahmen; Feki, Hafed E. L.; Schoenstein, Fréderic; Jouini, Noureddine

2012-07-01

This Letter describes a new approach for the synthesis of hydroxyapatite nanoparticles, which involves precipitation and hydrolysis reactions conducted in polyol medium. In fact, ammonium-hydrogen phosphate and calcium nitrate were dissolved in polyol, and then heated at the boiling point of the polyol (ethane1, 2diol or propane1, 2diol). Besides, the phase and composition of the polycrystalline were studied by TGA/DTA, FT-IR, TEM and XRD techniques. The nanoparticles thus obtained present interesting morphological characters varying from needle to very thin platelet. Moreover, the hydroxyapatite prepared in ployol shows higher cristallinity in comparison with that obtained by other 'chimie douce' methods.

Nanocrystalline hydroxyapatite enriched in selenite and manganese ions: physicochemical and antibacterial properties

NASA Astrophysics Data System (ADS)

Kolmas, Joanna; Groszyk, Ewa; Piotrowska, Urszula

2015-07-01

In this work, we used the co-precipitation method to synthesize hydroxyapatite (Mn-SeO3-HA) containing both selenium IV (approximately 3.60 wt.%) and manganese II (approximately 0.29 wt.%). Pure hydroxyapatite (HA), hydroxyapatite-containing manganese (II) ions (Mn-HA), and hydroxyapatite-containing selenite ions alone (SeO3-HA), prepared with the same method, were used as reference materials. The structures and physicochemical properties of all the obtained samples were investigated. PXRD studies showed that the obtained materials were homogeneous and consisted of apatite phase. Introducing selenites into the hydroxyapatite crystals considerably affects the size and degree of ordering. Experiments with transmission electron microscopy (TEM) showed that Mn-SeO3-HA crystals are very small, needle-like, and tend to form agglomerates. Fourier transform infrared spectroscopy (FT-IR) and solid-state nuclear magnetic resonance (ssNMR) were used to analyze the structure of the obtained material. Preliminary microbiological tests showed that the material demonstrated antibacterial activity against Staphylococcus aureus, yet such properties were not confirmed regarding Escherichia coli. PACS codes: 61, 76, 81

Pullulan-based composite scaffolds for bone tissue engineering: Improved osteoconductivity by pore wall mineralization.

PubMed

Amrita; Arora, Aditya; Sharma, Poonam; Katti, Dhirendra S

2015-06-05

Porous hydrogels have been explored for bone tissue engineering; however their poor mechanical properties make them less suitable as bone graft substitutes. Since incorporation of fillers is a well-accepted method for improving mechanical properties of hydrogels, in this work pullulan hydrogels were reinforced with nano-crystalline hydroxyapatite (nHAp) (5 wt% nHAp in hydrogel) and poly(3-hydroxybutyrate) (PHB) fibers (3 wt% fibers in hydrogel) containing nHAp (3 wt% nHAp in fibers). Addition of these fillers to pullulan hydrogel improved compressive modulus of the scaffold by 10 fold. However, the hydrophilicity of pullulan did not support adhesion and spreading of cells. To overcome this limitation, porous composite scaffolds were modified using a double diffusion method that enabled deposition of hydroxyapatite on pore walls. This method resulted in rapid and uniform coating of HAp throughout the three-dimensional scaffolds which not only rendered them osteoconductive in vitro but also led to an improvement in their compressive modulus. These results demonstrate the potential of mineralized pullulan-based composite scaffolds in non-load bearing bone tissue engineering. Copyright © 2015 Elsevier Ltd. All rights reserved.

Effect of nanocrystalline hydroxyapatite socket preservation on orthodontically induced inflammatory root resorption.

PubMed

Seifi, Massoud; Arayesh, Ali; Shamloo, Nafise; Hamedi, Roya

2015-01-01

Orthodontically induced inflammatory root resorption (OIIRR) is considered to be an important sequel associated with orthodontic tooth movement (OTM). OTM after Socket preservation enhances the periodontal condition before orthodontic space closure. The purpose of this study is to investigate the histologic effects of NanoBone®, a new highly nonsintered porous nano-crystalline hydroxyapatite bone on root resorption following OTM. This experimental study was conducted on four male dogs. In each dog, four defects were created at the mesial aspects of the maxillary and mandibular first premolars. The defects were filled with NanoBone®. We used the NiTi closed coil for mesial movement of the first premolar tooth. When the experimental teeth moved approximately halfway into the defects, after two months, the animals were sacrificed and we harvested the area of interest. The first premolar root and adjacent tissues were histologically evaluated. The three-way ANOVA statistical test was used for comparison. The mean root resorption in the synthetic bone substitute group was 22.87 ± 11.25×10(-4)mm(2) in the maxilla and 21.41 ± 11.25×10(-4)mm(2) in the mandible. Statistically, there was no significant difference compared to the control group (p>0.05). The use of a substitution graft in the nano particle has some positive effects in accessing healthy periodontal tissue following orthodontic procedures without significant influence on root resorption (RR). Histological evaluation in the present study showed osteoblastic activity and remodeling environment of nanoparticles in NanoBone®.

Effect of Nanocrystalline Hydroxyapatite Socket Preservation on Orthodontically Induced Inflammatory Root Resorption

PubMed Central

Seifi, Massoud; Arayesh, Ali; Shamloo, Nafise; Hamedi, Roya

2015-01-01

Objective Orthodontically induced inflammatory root resorption (OIIRR) is considered to be an important sequel associated with orthodontic tooth movement (OTM). OTM after Socket preservation enhances the periodontal condition before orthodontic space closure. The purpose of this study is to investigate the histologic effects of NanoBone®, a new highly nonsintered porous nano-crystalline hydroxyapatite bone on root resorption following OTM. Materials and Methods This experimental study was conducted on four male dogs. In each dog, four defects were created at the mesial aspects of the maxillary and mandibular first premolars. The defects were filled with NanoBone®. We used the NiTi closed coil for mesial movement of the first premolar tooth. When the experimental teeth moved approximately halfway into the defects, after two months, the animals were sacrificed and we harvested the area of interest. The first premolar root and adjacent tissues were histologically evaluated. The three-way ANOVA statistical test was used for comparison. Results The mean root resorption in the synthetic bone substitute group was 22.87 ± 11.25×10-4mm2 in the maxilla and 21.41 ± 11.25×10-4mm2 in the mandible. Statistically, there was no significant difference compared to the control group (p>0.05). Conclusion The use of a substitution graft in the nano particle has some positive effects in accessing healthy periodontal tissue following orthodontic procedures without significant influence on root resorption (RR). Histological evaluation in the present study showed osteoblastic activity and remodeling environment of nanoparticles in NanoBone®. PMID:25685742

Electric field-assisted formation of organically modified hydroxyapatite (ormoHAP) spheres in carboxymethylated gelatin gels.

PubMed

Heinemann, C; Heinemann, S; Kruppke, B; Worch, H; Thomas, J; Wiesmann, H P; Hanke, T

2016-10-15

A biomimetic strategy was developed in order to prepare organically modified hydroxyapatite (ormoHAP) with spherical shape. The technical approach is based on electric field-assisted migration of calcium ions and phosphate ions into a hydrogel composed of carboxymethylated gelatin. The electric field as well as the carboxymethylation using glucuronic acid (GlcA) significantly accelerates the mineralization process, which makes the process feasible for lab scale production of ormoHAP spheres and probably beyond. A further process was developed for gentle separation of the ormoHAP spheres from the gelatin gel without compromising the morphology of the mineral. The term ormoHAP was chosen since morphological analyses using electron microscopy (SEM, TEM) and element analysis (EDX, FT-IR, XRD) confirmed that carboxymethylated gelatin molecules use to act as organic templates for the formation of nanocrystalline HAP. The hydroxyapatite (HAP) crystals self-organize to form hollow spheres with diameters ranging from 100 to 500nm. The combination of the biocompatible chemical composition and the unique structure of the nanocomposites is considered to be a useful basis for future applications in functionalized degradable biomaterials. A novel bioinspired mineralization process was developed based on electric field-assisted migration of calcium and phosphate ions into biochemically carboxymethylated gelatin acting as organic template. Advantages over conventional hydroxyapatite include particle size distribution and homogeneity as well as achievable mechanical properties of relevant composites. Moreover, specifically developed calcium ion or phosphate ion release during degradation can be useful to adjust the fate of bone cells in order to manipulate remodeling processes. The hollow structure of the spheres can be useful for embedding drugs in the core, encapsulated by the highly mineralized outer shell. In this way, controlled drug release could be achieved, which enables

Sulfobetaine as a zwitterionic mediator for 3D hydroxyapatite mineralization

PubMed Central

Liu, Pingsheng; Song, Jie

2013-01-01

Both positively and negatively charged residues play pivotal roles in recruiting precursor ions or ion clusters, and lowering interfacial energy in natural biomineralization process. Synergistic utilization of opposite charges, however, has rarely been implemented in the design of cytocompatible synthetic scaffolds promoting hydroxyapatite (HA)-mineralization and osteointegration. We report the use of cytocompatible zwitterionic sulfobetaine ligands to enable 3-dimensional in vitro mineralization of HA across covalently crosslinked hydrogels. The overall charge-neutral zwitterionic hydrogel effectively recruited oppositely charged precursor ions while overcame excessive swelling exhibited by anionic and cationic hydrogels under physiological conditions, resulting in denser and structurally well-integrated mineralized composites. Further controls over the size, content, and spatial distribution of the mineral domains within the zwitterionic hydrogel are accomplished by facile adjustments of hydrogel crosslinking densities and the supersaturation rate governing heterogeneous mineral nucleation and growth. These findings should inspire many creative uses of zwitterionic polymers and polymer coatings for skeletal tissue repair and regeneration. PMID:23332320

Sulfobetaine as a zwitterionic mediator for 3D hydroxyapatite mineralization.

PubMed

Liu, Pingsheng; Song, Jie

2013-03-01

Both positively and negatively charged residues play pivotal roles in recruiting precursor ions or ion clusters, and lowering interfacial energy in natural biomineralization process. Synergistic utilization of opposite charges, however, has rarely been implemented in the design of cytocompatible synthetic scaffolds promoting hydroxyapatite (HA)-mineralization and osteointegration. We report the use of cytocompatible zwitterionic sulfobetaine ligands to enable 3-dimensional in vitro mineralization of HA across covalently crosslinked hydrogels. The overall charge-neutral zwitterionic hydrogel effectively recruited oppositely charged precursor ions while overcame excessive swelling exhibited by anionic and cationic hydrogels under physiological conditions, resulting in denser and structurally well-integrated mineralized composites. Further controls over the size, content, and spatial distribution of the mineral domains within the zwitterionic hydrogel are accomplished by facile adjustments of hydrogel crosslinking densities and the supersaturation rate governing heterogeneous mineral nucleation and growth. These findings should inspire many creative uses of zwitterionic polymers and polymer coatings for skeletal tissue repair and regeneration. Copyright © 2012 Elsevier Ltd. All rights reserved.

Robust Bonding of Tough Double Network Hydrogel to Bone

NASA Astrophysics Data System (ADS)

Nonoyama, Takayuki; Wada, Susumu; Kiyama, Ryuji; Kitamura, Nobuto; Kurokawa, Takayuki; Nakajima, Tasuku; Yasuda, Kazunori; Gong, Jian Ping

Tough Double Network (DN) hydrogels are one of candidates as next-generation artificial cartilage from the viewpoints of low friction, water storage capability and toughness. For practical use, the hydrogel must be strongly fixed at the joint. However, strong fixation of such hydrogel to other materials (tissues) has not been achieved yet because the surface property of hydrogel is almost equal to water due to its high water content. Therefore, robust adhesion for fixation and low friction for lithe motion are trade-off relation. Here, we report robust fixation of hydroxyapatite (HAp) mineralized DN hydrogel to the bone without any toxicity. HAp is main inorganic component of bone tissues and has osteoconductive capability. After 4 weeks implantation of HAp/DN gel into rabbit femoral groove, The robust fixation between bone and HAp/DN gel, more than strength of gel matrix, was achieved. The methodology is universal for new biomaterials, which should be fixed on bone, such as ligament and tendon systems.

Preparation and characterization of selenite substituted hydroxyapatite.

PubMed

Ma, Jun; Wang, Yanhua; Zhou, Lei; Zhang, Shengmin

2013-01-01

Selenite-substituted hydroxyapatite (Se-HA) with different Se/P ratios was synthesized by a co-precipitation method, using sodium selenite (Na2SeO3) as a Se source. Selenium has been incorporated into the hydroxyapatite lattice by partially replacing phosphate (PO4(3-)) groups with selenite (SeO3(2-)) groups. X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM) techniques reveal that substitutions of phosphate groups by selenite groups cause lower carbonate groups occupying at phosphate sites and change the lattice parameters of hydroxyapatite. The powders obtained are nano-crystalline hydroxyapatite when the Se/P ratios are not more than 0.1. The particle shape of Se-HA has not been altered compared with selenite-free hydroxyapatite but Se-incorporation reduces the crystallite size. The crystallinity was reduced as the Se/P ratios increased until amorphous phase (Se/P=0.3) appeared in the Se-HA powder obtained, and then another crystal phase presented as calcium selenite hydrate (Se/P=10). In addition, the sintering tests show that the Se-HA powders with the Se/P ratio of 0.1 have thermal stability at 900 °C for 2 h; hence they have great potential in the fabrication of bone repair scaffolds. Copyright © 2012 Elsevier B.V. All rights reserved.

In vivo evaluation of the bone integration of coated poly(vinyl-alcohol) hydrogel fiber implants.

PubMed

Moreau, David; Villain, Arthur; Bachy, Manon; Proudhon, Henry; Ku, David N; Hannouche, Didier; Petite, Hervé; Corté, Laurent

2017-08-01

Recently, it has been shown that constructs of poly(vinyl alcohol) (PVA) hydrogel fibers reproduce closely the tensile behavior of ligaments. However, the biological response to these systems has not been explored yet. Here, we report the first in vivo evaluation of these implants and focus on the integration in bone, using a rabbit model of bone tunnel healing. Implants consisted in bundles of PVA hydrogel fibers embedded in a PVA hydrogel matrix. Half of the samples were coated with a composite coating of hydroxyapatite (HA) particles embedded in PVA hydrogel. The biological integration was evaluated at 6 weeks using histology and micro-CT imaging. For all implants, a good biological tolerance and growth of new bone tissue are reported. All the implants were surrounded by a fibrous layer comparable to what was previously observed for poly(ethylene terephthalate) (PET) fibers currently used in humans for ligament reconstruction. An image analysis method is proposed to quantify the thickness of this fibrous capsule. Implants coated with HA were not significantly osteoconductive, which can be attributed to the slow dissolution of the selected hydroxyapatite. Overall, these results confirm the relevance of PVA hydrogel fibers for ligament reconstruction and adjustments are proposed to enhance its osseointegration.

Preparation and Characterization of Hydroxyapatite-Silica Composite Nanopowders

NASA Astrophysics Data System (ADS)

Latifi, S. M.; Fathi, M. H.; Golozar, M. A.

One of the most important objectives in the field of biomaterials science and engineering is development of new materials as bone substitutes. Silica (SiO2) has an important role in the biomineralization and biological responses. The aim of this research was to prepare and characterize hydroxyapatite-silica (HA-SiO2) composite nanopowder with different content of silica. Hydroxyapatite-silica composite nanopowders with 20 and 40 wt% silica were prepared using a sol-gel method at 600°C with phosphoric pentoxide and calcium nitrate tetrahydrate as a source of hydroxyapatite; also, tetraethylorthosilicate and methyltriethoxisilane as a source of silica. Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) techniques were used for characterization and evaluation of the products. The results indicated the presence of nanocrystalline hydroxyapatite phase beside amorphous silica phase in prepared composite nanopowders. Moreover, by increasing the content of silica in composite nanopowders, the crystallinity will be decreased,and the ability of the product as a bone substitute material might be controlled by changing the content of the ingredients and subsequently its structure.

Determination of Microstructural Parameters of Nanocrystalline Hydroxyapatite Prepared by Mechanical Alloying Method

NASA Astrophysics Data System (ADS)

Joughehdoust, Sedigheh; Manafi, Sahebali

2011-12-01

Hydroxyapatite [HA, Ca10(PO4)6(OH)2] is chemically similar to the mineral component of bones and hard tissues. HA can support bone ingrowth and osseointegration when used in orthopaedic, dental and maxillofacial applications. In this research, HA nanostructure was synthesized by mechanical alloying method. Phase development, particle size and morphology of HA were investigated by X-ray diffraction (XRD) pattern, zetasizer instrument, scanning electron microscopy (SEM), respectively. XRD pattern has been used to determination of the microstructural parameters (crystallite size, lattice parameters and crystallinity percent) by Williamson-Hall equation, Nelson-Riley method and calculating the areas under the peaks, respectively. The crystallite size and particle size of HA powders were in nanometric scales. SEM images showed that some parts of HA particles have agglomerates. The ratio of lattice parameters of synthetic hydroxyapatite (c/a = 0.73) was determined in this study is the same as natural hydroxyapatite structure.

Structural and physical properties of antibacterial Ag-doped nano-hydroxyapatite synthesized at 100°C

PubMed Central

2011-01-01

Synthesis of nanosized particle of Ag-doped hydroxyapatite with antibacterial properties is in the great interest in the development of new biomedical applications. In this article, we propose a method for synthesized the Ag-doped nanocrystalline hydroxyapatite. A silver-doped nanocrystalline hydroxyapatite was synthesized at 100°C in deionized water. Other phase or impurities were not observed. Silver-doped hydroxyapatite nanoparticles (Ag:HAp) were performed by setting the atomic ratio of Ag/[Ag + Ca] at 20% and [Ca + Ag]/P as 1.67. The X-ray diffraction studies demonstrate that powders made by co-precipitation at 100°C exhibit the apatite characteristics with good crystal structure and no new phase or impurity is found. The scanning electron microscopy (SEM) observations suggest that these materials present a little different morphology, which reveals a homogeneous aspect of the synthesized particles for all samples. The presence of calcium (Ca), phosphor (P), oxygen (O), and silver (Ag) in the Ag:HAp is confirmed by energy dispersive X-ray (EDAX) analysis. FT-IR and FT-Raman spectroscopies revealed that the presence of the various vibrational modes corresponds to phosphates and hydroxyl groups. The strain of Staphylococcus aureus was used to evaluate the antibacterial activity of the Ca10-xAgx(PO4)6(OH)2 (x = 0 and 0.2). In vitro bacterial adhesion study indicated a significant difference between HAp (x = 0) and Ag:HAp (x = 0.2). The Ag:Hap nanopowder showed higher inhibition. PMID:22136671

Structural and physical properties of antibacterial Ag-doped nano-hydroxyapatite synthesized at 100°C

NASA Astrophysics Data System (ADS)

Ciobanu, Carmen Steluta; Massuyeau, Florian; Constantin, Liliana Violeta; Predoi, Daniela

2011-12-01

Synthesis of nanosized particle of Ag-doped hydroxyapatite with antibacterial properties is in the great interest in the development of new biomedical applications. In this article, we propose a method for synthesized the Ag-doped nanocrystalline hydroxyapatite. A silver-doped nanocrystalline hydroxyapatite was synthesized at 100°C in deionized water. Other phase or impurities were not observed. Silver-doped hydroxyapatite nanoparticles (Ag:HAp) were performed by setting the atomic ratio of Ag/[Ag + Ca] at 20% and [Ca + Ag]/P as 1.67. The X-ray diffraction studies demonstrate that powders made by co-precipitation at 100°C exhibit the apatite characteristics with good crystal structure and no new phase or impurity is found. The scanning electron microscopy (SEM) observations suggest that these materials present a little different morphology, which reveals a homogeneous aspect of the synthesized particles for all samples. The presence of calcium (Ca), phosphor (P), oxygen (O), and silver (Ag) in the Ag:HAp is confirmed by energy dispersive X-ray (EDAX) analysis. FT-IR and FT-Raman spectroscopies revealed that the presence of the various vibrational modes corresponds to phosphates and hydroxyl groups. The strain of Staphylococcus aureus was used to evaluate the antibacterial activity of the Ca10- x Ag x (PO4)6(OH)2 ( x = 0 and 0.2). In vitro bacterial adhesion study indicated a significant difference between HAp ( x = 0) and Ag:HAp ( x = 0.2). The Ag:Hap nanopowder showed higher inhibition.

Ice templated and cross-linked xylan/nanocrystalline cellulose hydrogels

Treesearch

Tobias Köhnke; Thomas Elder; Hans Theliander; Arthur J. Ragauskas

2014-01-01

Structured xylan-based hydrogels, reinforced with cellulose nanocrystals (CNCs), have successfully been prepared from water suspensions by cross-linking during freeze-casting. In order to induce cross-linking during the solidification/sublimation operation, xylan was first oxidized using sodium periodate to introduce dialdehydes. The oxidized xylan was then mixed with...

Histological and histomorphometrical analysis of a silica matrix embedded nanocrystalline hydroxyapatite bone substitute using the subcutaneous implantation model in Wistar rats.

PubMed

Ghanaati, Shahram; Orth, Carina; Barbeck, Mike; Willershausen, Ines; Thimm, Benjamin W; Booms, Patrick; Stübinger, Stefan; Landes, Constantin; Sader, Robert Anton; Kirkpatrick, Charles James

2010-06-01

The clinical suitability of a bone substitute material is determined by the ability to induce a tissue reaction specific to its composition. The aim of this in vivo study was to analyze the tissue reaction to a silica matrix-embedded, nanocrystalline hydroxyapatite bone substitute.The subcutaneous implantation model in Wistar rats was chosen to assess the effect of silica degradation on the vascularization of the biomaterial and its biodegradation within a time period of 6 months. Already at day 10 after implantation, histomorphometrical analysis showed that the vascularization of the implantation bed reached its peak value compared to all other time points. Both vessel density and vascularization significantly decreased until day 90 after implantation. In this time period, the bone substitute underwent a significant degradation initiated by TRAP-positive and TRAP-negative multinucleated giant cells together with macrophages and lymphocytes. Although no specific tissue reaction could be related to the described silica degradation, the biomaterial was close to being fully degraded without a severe inflammatory response. These characteristics are advantageous for bone regeneration and remodeling processes.

Self Assembled Bi-functional Peptide Hydrogels with Biomineralization-Directing Peptides

PubMed Central

Gungormus, Mustafa; Branco, Monica; Fong, Hanson; Schneider, Joel P.; Tamerler, Candan; Sarikaya, Mehmet

2014-01-01

A peptide-based hydrogel has been designed that directs the formation of hydroxyapatite. MDG1, a twenty-seven residue peptide, undergoes triggered folding to form an unsymmetrical β-hairpin that self-assembles in response to an increase in solution ionic strength to yield a mechanically rigid, self supporting hydrogel. The C-terminal portion of MDG1 contains a heptapeptide (MLPHHGA) capable of directing the mineralization process. Circular dichroism spectroscopy indicates that the peptide folds and assembles to form a hydrogel network rich in β-sheet secondary structure. Oscillatory rheology indicates that the hydrogel is mechanical rigid (G′ ∼ 2500 Pa) before mineralization. In separate experiments, mineralization was induced both biochemically and with cementoblast cells. Mineralization-domain had little effect on the mechanical rigidity of the gel. SEM and EDS show that MDG1 gels are capable of directing the formation of hydroxapatite. Control hydrogels, prepared by peptides either lacking the mineral-directing portion or reversing its sequence, indicated that the heptapeptide is necessary and its actions are sequence specific. PMID:20591477

Nanophase hydroxyapatite coatings for dental and orthopedic applications

NASA Astrophysics Data System (ADS)

Sato, Michiko

In order to improve dental and orthopedic implant performance, the objective of this study was to synthesize nanocrystalline hydroxyapatite (HA) powders to coat metals (specifically, titanium and tantalum). Precipitated HA powders were either sintered in order to produce UltraCaP HA (or microcrystalline size HA) or were treated hydrothermally to produce nanocrystalline HA. Some of the UltraCaP and nanocrystalline HA powders were doped with yttrium (Y) since previous in vitro studies demonstrated that Y-doped HA in bulk improved osteoblast (or bone-forming cell) function over undoped HA. The nanocrystalline HA powders were also mixed with nanophase titania powders because previous studies demonstrated that titania/HA composite coatings increased coating adhesive strength and HA nucleation. These powders were then deposited onto titanium by a novel room-temperature process, called IonTiteT(TM). The results demonstrated that the chemical properties and crystallite size of the original HA powders were maintained in the coatings. More importantly, in vitro studies showed increased osteoblast (bone-forming cell) adhesion on the single phase nanocrystalline HA and nano-titania/HA coatings compared to traditionally used plasma-sprayed HA coatings and uncoated metals. Results further demonstrated greater amounts of calcium deposition by osteoblasts cultured on nanocrystalline HA coatings compared to UltraCaP coatings and conventionally used plasma-sprayed HA coatings. To elucidate mechanisms that influenced osteoblast functions on the HA coatings, the amount of proteins (fibronectin and vitronectin) onto the HA powders and the adsorbed fibronectin conformation were investigated. Exposure of cell integrin binding domains (in fibronectin III10 segments) was greater in fibronectin adsorbed onto 1.2 mole% Y-doped UltraCaP HA coatings compared to nanocrystalline HA coatings tested. However, 1.2 mole% Y-doped UltraCaP HA coatings did not increase mineralization by osteoblasts

Optical properties of hydroxyapatite obtained by mechanical alloying

NASA Astrophysics Data System (ADS)

Silva, C. C.; Thomazini, D.; Pinheiro, A. G.; Lanciotti, F.; Sasaki, J. M.; Góes, J. C.; Sombra, A. S. B.

2002-09-01

Calcium phosphate based bioceramics, mainly in the form of hydroxyapatite (HA), have been in use in medicine and dentistry for the last 20 years. Applications include coatings of orthopaedic and dental implants, alveolar ridge augmentation, maxillofacial surgery, otolaryngology, and scaffolds for bone growth and as powders in total hip and knee surgery. These materials exhibit several problems of handling and fabrication, which can be overcome by mixing with a suitable binder. In this paper, mechanical alloying has been used successfully to produce nanocrystalline powders of HA using five different experimental procedures. The milled HA were studied by X-ray powder diffraction, infrared and Raman scattering spectroscopy. For four different procedures, HA was obtained after a couple of hours of milling (on an average, 20 h of milling depending on the reaction procedure). The XRD patterns indicate that the grain size is within the range of 29-103 nm. This milling process, used to produce HA, presents the advantage that melting is not necessary and the powder obtained is nanocrystalline with extraordinary mechanical properties. The material can be compacted and transformed in solid ceramic samples. The high efficiency of the process opens a way to produce commercial amount of nanocrystalline HA. Due to the nanocrystalline character of this powder, their mechanical properties have changed and for this reason a pressure of 1 GPa is enough to shape the sample into any geometry.

In Situ Mineralization of Magnetite Nanoparticles in Chitosan Hydrogel

NASA Astrophysics Data System (ADS)

Wang, Yongliang; Li, Baoqiang; Zhou, Yu; Jia, Dechang

2009-09-01

Based on chelation effect between iron ions and amino groups of chitosan, in situ mineralization of magnetite nanoparticles in chitosan hydrogel under ambient conditions was proposed. The chelation effect between iron ions and amino groups in CS-Fe complex, which led to that chitosan hydrogel exerted a crucial control on the magnetite mineralization, was proved by X-ray photoelectron spectrum. The composition, morphology and size of the mineralized magnetite nanoparticles were characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy and thermal gravity. The mineralized nanoparticles were nonstoichiometric magnetite with a unit formula of Fe2.85O4 and coated by a thin layer of chitosan. The mineralized magnetite nanoparticles with mean diameter of 13 nm dispersed in chitosan hydrogel uniformly. Magnetization measurement indicated that superparamagnetism behavior was exhibited. These magnetite nanoparticles mineralized in chitosan hydrogel have potential applications in the field of biotechnology. Moreover, this method can also be used to synthesize other kinds of inorganic nanoparticles, such as ZnO, Fe2O3 and hydroxyapatite.

In vitro BMP-2 peptide release from thiolated chitosan based hydrogel.

PubMed

Liu, Xujie; Yu, Bo; Huang, Qianli; Liu, Rui; Feng, Qingling; Cai, Qiang; Mi, Shengli

2016-12-01

Thiolated chitosan based thermo-sensitive hydrogel is a water soluble system and the existing thiol groups are beneficial for the delivery of cysteine-rich peptides. In the present study, a kind of thiolated chitosan, i.e. chitosan-4-thio-butylamidine (CS-TBA) conjugate was characterized and used to prepare CS-TBA/hydroxyapatite (HA)/beta-glycerophosphate disodium (β-GP) thermo-sensitive hydrogel. The cysteine terminated peptide 24 (P24) containing residues 73-92 of the knuckle epitope of BMP-2 (N→C: KIPKASSVPTELSAISTLYLSGGC) was synthesized and characterized. The release behavior of P24 from CS-TBA based hydrogel was investigated in vitro. The thiol groups in CS-TBA may react with thiol groups in P24, thus decreases the P24 release rate and maintains the peptide release for a longer time compared with unmodified chitosan based hydrogel. Moreover, the bioactivity of P24 is preserved during release process. These results indicate that P24 loaded CS-TBA based thermosensitive hydrogel is a potential material for minimally invasive surgery of bone repair. Copyright © 2016 Elsevier B.V. All rights reserved.

Peptide Probe for Crystalline Hydroxyapatite: In Situ Detection of Biomineralization

NASA Astrophysics Data System (ADS)

Cicerone, Marcus; Becker, Matthew; Simon, Carl; Chatterjee, Kaushik

2009-03-01

While cells template mineralization in vitro and in vivo, specific detection strategies that impart chemical and structural information on this process have proven elusive. Recently we have developed an in situ based peptide probe via phage display methods that is specific to crystalline hydroxyapatite (HA). We are using this in fluorescence based assays to characterize mineralization. One application being explored is the screening of tissue engineering scaffolds for their ability to support osteogenesis. Specifically, osteoblasts are being cultured in hydrogel scaffolds possessing property gradients to provide a test bed for the HA peptide probe. Hydrogel properties that support osteogenesis and HA deposition will be identified using the probe to demonstrate its utility in optimizing design of tissue scaffolds.

Thermal and structural characterization of synthetic and natural nanocrystalline hydroxyapatite.

PubMed

Sofronia, Ancuta M; Baies, Radu; Anghel, Elena M; Marinescu, Cornelia A; Tanasescu, Speranta

2014-10-01

The aim of this work was to study the thermal stability on heating and to obtain the processing parameters of synthetic and bone-derived hydroxyapatite over temperatures between room temperature and 1400°C by thermal analysis (thermogravimetry (TG)/differential scanning calorimetry (DSC) and thermo-mechanical analysis-TMA). Structural and surface modifications related to samples origin and calcination temperature were investigated by Fourier transformed infrared (FTIR) and Raman spectroscopy, X-ray diffraction (XRD) and BET method. FTIR spectra indicated that the organic constituents and carbonate are no longer present in the natural sample calcined at 800°C. Raman spectra highlighted the decomposition products of the hydroxyapatite. The calcination treatment modifies the processes kinetics of the synthetic samples, being able to isolate lattice water desorption processes of decarbonization and the dehydroxylation processes. Shrinkage of calcined synthetic sample increases by 10% compared to uncalcined synthetic powder. From the TMA correlated with TG analysis and heat capacity data it can be concluded that sintering temperature of the synthetic samples should be chosen in the temperature range of the onset of dehydroxylation and the temperature at which oxyapatite decomposition begins. Copyright © 2014 Elsevier B.V. All rights reserved.

A Bioactive Hydrogel and 3D Printed Polycaprolactone System for Bone Tissue Engineering.

PubMed

Hernandez, Ivan; Kumar, Alok; Joddar, Binata

2017-09-01

In this study, a hybrid system consisting of 3D printed polycaprolactone (PCL) filled with hydrogel was developed as an application for reconstruction of long bone defects, which are innately difficult to repair due to large missing segments of bone. A 3D printed gyroid scaffold of PCL allowed a larger amount of hydrogel to be loaded within the scaffolds as compared to 3D printed mesh and honeycomb scaffolds of similar volumes and strut thicknesses. The hydrogel was a mixture of alginate, gelatin, and nano-hydroxyapatite, infiltrated with human mesenchymal stem cells (hMSC) to enhance the osteoconductivity and biocompatibility of the system. Adhesion and viability of hMSC in the PCL/hydrogel system confirmed its cytocompatibility. Biomineralization tests in simulated body fluid (SBF) showed the nucleation and growth of apatite crystals, which confirmed the bioactivity of the PCL/hydrogel system. Moreover, dissolution studies, in SBF revealed a sustained dissolution of the hydrogel with time. Overall, the present study provides a new approach in bone tissue engineering to repair bone defects with a bioactive hybrid system consisting of a polymeric scaffold, hydrogel, and hMSC.

Marine macromolecules cross-linked hydrogel scaffolds as physiochemically and biologically favorable entities for tissue engineering applications.

PubMed

Sumayya, A S; Muraleedhara Kurup, G

2017-06-01

Marine biopolymer composite materials provide a technological platform for launching biomedical applications. Biomaterials demand good biocompatibility without the possibility of inflammation or foreign body reactions. In this study, we prepared two biocomposite hydrogels namely; HAC (hydroxyapatite, alginate & chitosan) and HACF (hydroxyapatite, alginate, chitosan & fucoidan) followed by calcium chloride cross linking. The prepared scaffolds were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. Porosity measurement, swelling, biodegradation, hemolysis, RBC aggregation, plasma protein adsorption and cytotoxicity studies were also done. The hydrogel scaffold HACF possessed a well-defined porous architecture, sufficient water holding capacity, better hemocompatibility and biodegradability. The biocompatibility was confirmed through in vitro cytotoxicity studies such as MTT assay, Neutral red uptake, DAPI staining, Trypan blue dye exclusion test and direct contact assay in L929 mouse fibroblast cells. In addition, immunomodulatory and anti-inflammatory properties of both of these scaffolds were revealed by the mRNA expressions of major inflammatory marker genes in cytotoxic condition such as TNF-α, IL-6 and NF-κB. The physiochemical characterization and biological responses of HACF hydrogel signifies its suitability for various tissue engineering applications.

Development of carboxymethyl cellulose-based hydrogel and nanosilver composite as antimicrobial agents for UTI pathogens.

PubMed

Alshehri, Saad M; Aldalbahi, Ali; Al-Hajji, Abdullah Baker; Chaudhary, Anis Ahmad; Panhuis, Marc In Het; Alhokbany, Norah; Ahamad, Tansir

2016-03-15

Silver nanoparticles (AgNPs) containing hydrogel composite were first synthesized by preparing a new hydrogel from carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), and the cross-linker ethylene glycol diglycidyl ether (EGDE), followed by the incorporation of AgNPs by microwave radiation. The resulting neat hydrogels and AgNPs-hydrogel composites were characterized using spectral, thermal, microscopic analysis and X-ray diffraction (XRD) analyses. The SEM and TEM results demonstrated that the synthesized AgNPs were spherical with diameters ranging from 8 to 14nm. In addition, the XRD analysis confirmed the nanocrystalline phase of silver with face-centered cubic (FCC) crystal structure. Energy dispersive spectroscopy (EDS) analysis of the AgNPs confirmed the presence of an elemental silver signal, and no peaks of any other impurities were detected. Additionally, the antibacterial activities of the neat hydrogel and AgNPs-hydrogel composites were measured by Kirby-Bauer method against urinary tract infection (UTI) pathogens. The rheology measurement revealed that the values of storage modulus (G') were higher than that of loss modulus (G″). The AgNPs-hydrogel composites exhibited higher antibacterial activity against Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Proteus vulgaris, Staphylococcus aureus and Proteus mirabilis compared to the corresponding neat hydrogel. Copyright © 2015 Elsevier Ltd. All rights reserved.

Hydroxyapatite paste Ostim, without elevation of full-thickness flaps, improves alveolar healing stimulating BMP- and VEGF-mediated signal pathways: an experimental study in humans.

PubMed

Canuto, R A; Pol, R; Martinasso, G; Muzio, G; Gallesio, G; Mozzati, M

2013-08-01

Tooth extraction is considered as the starting point of jaw atrophy via osteoclast activity stimulation. The maintenance of dental alveolar bone depends on surgery procedure and use of materials to maintain prior space favoring bone regeneration. Among substitutes used in dentistry to fill bone defects, Ostim-Pastes (Ostim) is a nanocrystalline paste tested for treatment of severe clinical conditions. This research first investigated the effect of Ostim on alveolar healing, comparing in the same healthy subjects, an Ostim-filled socket with a not-filled one. Moreover, it also proposed a new surgical protocol for the post-extractive socket treatment using the graft materials without elevation of full-thickness flaps. Fourteen patients were enrolled to bilateral maxillary or mandibular extraction that was performed without elevation of full-thickness flaps. In each patient, one socket was filled using Ostim, and the other one was allowed to undergo natural healing. No suture was carried out. Clinical and biologic parameters were screened at 1, 7, and 14 days. Obtained results evidenced that nanocrystalline hydroxyapatite supports bone regeneration, increasing the synthesis of pro-osteogenic factors as bone morphogenetics protein (BMP)-4, BMP-7, alkaline phosphatase, and osteocalcin. Moreover, filling post-extractive socket with nanocrystalline hydroxyapatite paste leads to a complete epithelialization already at 7 days after extraction, despite the fact that the teeth were extracted without elevation of full-thickness flaps . The improved epithelialization is mediated by increased vascular endothelial growth factor (VEGF) expression. No significant change was observed in inflammatory parameters, with exception of an early and transient IL-1β induction, that could trigger and improve alveolar healing. Clinical and biomolecular observations of this explorative study evidenced that nanocrystalline hydroxyapatite improves alveolar socket healing, increasing angiogenesis

Histological evaluation of human intrabony periodontal defects treated with an unsintered nanocrystalline hydroxyapatite paste.

PubMed

Horváth, Attila; Stavropoulos, Andreas; Windisch, Péter; Lukács, László; Gera, István; Sculean, Anton

2013-03-01

The aim of the study was to clinically and histologically evaluate the healing of human intrabony defects treated with open flap surgery (OFD) and application of a new, resorbable, fully synthetic, unsintered, nanocrystalline, phase-pure hydroxyapatite (nano-HA). Six patients, each of them displaying very advanced intrabony defects around teeth scheduled for extraction due to advanced chronic periodontitis and further prosthodontic considerations, were included in the study. Following local anaesthesia, mucoperiosteal flaps were reflected; the granulation tissue was removed, and the roots were meticulously debrided by hand and ultrasonic instruments. A notch was placed at the most apical extent of the calculus present on the root surface or at the most apical part of the defect (if no calculus was present) in order to serve as a reference for the histological evaluation. Following defect fill with nano-HA, the flaps were sutured by means of mattress sutures to allow primary intention healing. At 7 months after regenerative surgery, the teeth were extracted together with some of their surrounding soft and hard tissues and processed for histological analysis. The postoperative healing was uneventful in all cases. At 7 months following surgery, mean PPD reduction and mean CAL gain measured 4.0 ± 0.8 and 2.5 ± 0.8 mm, respectively. The histological analysis revealed a healing predominantly characterized by epithelial downgrowth. Limited formation of new cementum with inserting connective tissue fibers and bone regeneration occurred in three out of the six biopsies (i.e. 0-0.86 and 0-1.33 mm, respectively). Complete resorption of the nano-HA was found in four out of the six biopsies. A few remnants of the graft particles (either surrounded by newly formed mineralized tissue or encapsulated in connective tissue) were found in two out of the six biopsies. Within their limits, the present results indicate that nano-HA has limited potential to promote periodontal

Immunohistochemical characterization of nanocrystalline hydroxyapatite silica gel (NanoBone(r)) osteogenesis: a study on biopsies from human jaws.

PubMed

Götz, Werner; Gerber, Thomas; Michel, Barbara; Lossdörfer, Stefan; Henkel, Kai-Olaf; Heinemann, Friedhelm

2008-10-01

Bone substitute biomaterials may be osteogenic, osteoconductive or osteoinductive. To test for these probable characteristics in a new nanoporous grafting material consisting of nanocrystalline hydroxyapatite embedded in a porous silica gel matrix (NanoBone(s)), applied in humans, we studied biopsies from 12 patients before dental implantation following various orofacial augmentation techniques with healing times of between 3.5 and 12 months. Sections from decalcified specimens were investigated using histology, histochemistry [periodic acid Schiff, alcian blue staining and tartrate-resistant acid phosphatase (TRAP)] and immunohistochemistry, with markers for osteogenesis, bone remodelling, resorption and vessel walls (alkaline phosphatase, bone morphogenetic protein-2, collagen type I, ED1, osteocalcin, osteopontin, runx2 and Von-Willebrand factor). Histologically, four specific stages of graft transformation into lamellar bone could be characterized. During early stages of healing, bone matrix proteins were absorbed by NanoBone(s) granules, forming a proteinaceous matrix, which was invaded by small vessels and cells. We assume that the deposition of these molecules promotes early osteogenesis in and around NanoBone(s) and supports the concomitant degradation probably by osteoclast-like cells. TRAP-positive osteoclast-like cells were localized directly on the granular surfaces. Runx2-immunoreactive pre-osteoblasts, which are probably involved in direct osteogenesis forming woven bone that is later transformed into lamellar bone, were attracted. Graft resorption and bone apposition around the graft granules appear concomitantly. We postulate that NanoBone(s) has osteoconductive and biomimetic properties and is integrated into the host's physiological bone turnover at a very early stage.

Preparation of thermally stable nanocrystalline hydroxyapatite by hydrothermal method.

PubMed

Prakash Parthiban, S; Elayaraja, K; Girija, E K; Yokogawa, Y; Kesavamoorthy, R; Palanichamy, M; Asokan, K; Narayana Kalkura, S

2009-12-01

Thermally stable hydroxyapatite (HAp) was synthesized by hydrothermal method in the presence of malic acid. X-ray diffraction (XRD), Fourier transform infra-red spectroscopy (FT-IR), Raman spectroscopy, scanning electron microscopy (SEM), differential thermal analysis (DTA), thermogravimetric analysis (TGA) was done on the synthesized powders. These analyses confirmed the sample to be free from impurities and other phases of calcium phosphates, and were of rhombus morphology along with nanosized particles. IR and Raman analyses indicated the adsorption of malic acid on HAp. Thermal stability of the synthesized HAp was confirmed by DTA and TGA. The synthesized powders were thermally stable upto 1,400 degrees C and showed no phase change. The proposed method might be useful for producing thermally stable HAp which is a necessity for high temperature coating applications.

Thin Bioactive Zn Substituted Hydroxyapatite Coating Deposited on Ultrafine Grained Titanium Substrate: Structure Analysis

NASA Astrophysics Data System (ADS)

Prosolov, Konstantin A.; Belyavskaya, Olga A.; Muehle, Uwe; Sharkeev, Yurii P.

2018-02-01

Nanocrystalline Zn substituted hydroxyapatite coatings were deposited by radiofrequency magnetron sputtering on the surface of ultrafine-grained titanium substrates. Cross section transmission electron microscopy provided information about the morphology and texture of the thin film while in-column energy dispersive X-ray analysis confirmed the presence of Zn in the coating. The Zn substituted hydroxyapatite coating was formed by an equiaxed polycrystalline grain structure. Effect of substrate crystallinity on the structure of deposited coating is discussed. An amorphous TiO2 sublayer of 8 nm thickness was detected in the interface between the polycrystalline coating and the Ti substrate. Its appearance in the amorphous state is attributed to prior to deposition etching of the substrate and subsequent condensation of oxygen-containing species sputtered from the target. This layer contributes to the high coating-to-substrate adhesion. The major P-O vibrational modes of high intensity were detected by Raman spectroscopy. The Zn substituted hydroxyapatite could be a material of choice when antibacterial osteoconductive coating with a possibility of withstanding mechanical stress during implantation and service is needed.

Hydroxyapatite formation on titania-based materials in a solution mimicking body fluid: Effects of manganese and iron addition in anatase.

PubMed

Shin, Euisup; Kim, Ill Yong; Cho, Sung Baek; Ohtsuki, Chikara

2015-03-01

Hydroxyapatite formation on the surfaces of implanted materials plays an important role in osteoconduction of bone substitutes in bone tissues. Titania hydrogels are known to instigate hydroxyapatite formation in a solution mimicking human blood plasma. To date, the relationship between the surface characteristics of titania and hydroxyapatite formation on its surface remains unclear. In this study, titania powders with varying surface characteristics were prepared by addition of manganese or iron to examine hydroxyapatite formation in a type of simulated body fluid (Kokubo solution). Hydroxyapatite formation was monitored by observation of deposited particles with scale-like morphology on the prepared titania powders. The effect of the titania surface characteristics, i.e., crystal structure, zeta potential, hydroxy group content, and specific surface area, on hydroxyapatite formation was examined. Hydroxyapatite formation was observed on the surface of titania powders that were primarily anatase, and featured a negative zeta potential and low specific surface areas irrespective of the hydroxy group content. High specific surface areas inhibited the formation of hydroxyapatite because calcium and phosphate ions were mostly consumed by adsorption on the titania surface. Thus, these surface characteristics of titania determine its osteoconductivity following exposure to body fluid. Copyright © 2014 Elsevier B.V. All rights reserved.

Adsorption of benzoxaboroles on hydroxyapatite phases.

PubMed

Pizzoccaro, Marie-Alix; Nikel, Ondrej; Sene, Saad; Philippe, Coralie; Mutin, P Hubert; Bégu, Sylvie; Vashishth, Deepak; Laurencin, Danielle

2016-09-01

Benzoxaboroles are a family of molecules that are finding an increasing number of applications in the biomedical field, particularly as a "privileged scaffold" for the design of new drugs. Here, for the first time, we determine the interaction of these molecules with hydroxyapatites, in view of establishing (i) how benzoxaborole drugs may adsorb onto biological apatites, as this could impact on their bioavailability, and (ii) how apatite-based materials can be used for their formulation. Studies on the adsorption of the benzoxaborole motif (C7H7BO2, referred to as BBzx) on two different apatite phases were thus performed, using a ceramic hydroxyapatite (HAceram) and a nanocrystalline hydroxyapatite (HAnano), the latter having a structure and composition more similar to the one found in bone mineral. In both cases, the grafting kinetics and mechanism were studied, and demonstration of the surface attachment of the benzoxaborole under the form of a tetrahedral benzoxaborolate anion was established using (11)B solid state NMR (including (11)B-(31)P correlation experiments). Irrespective of the apatite used, the grafting density of the benzoxaborolates was found to be low, and more generally, these anions demonstrated a poor affinity for apatite surfaces, notably in comparison with other anions commonly found in biological media, such as carboxylates and (organo)phosphates. The study was then extended to the adsorption of a molecule with antimicrobial and antifungal properties (3-piperazine-bis(benzoxaborole)), showing, on a more general perspective, how hydroxyapatites can be used for the development of novel formulations of benzoxaborole drugs. Benzoxaboroles are an emerging family of molecules which have attracted much attention in the biomedical field, notably for the design of new drugs. However, the way in which these molecules, once introduced in the body, may interact with bone mineral is still unknown, and the possibility of associating benzoxaboroles to

Clinical and radiographic evaluation of nanocrystalline hydroxyapatite with or without platelet-rich fibrin membrane in the treatment of periodontal intrabony defects

PubMed Central

Elgendy, Enas Ahmed; Abo Shady, Tamer Elamer

2015-01-01

Background: Nano-sized ceramics may represent a promising class of bone graft substitutes due to their improved osseointegrative properties. Nanocrystalline hydroxyapatite (NcHA) binds to bone and stimulate bone healing by stimulation of osteoblast activity. Platelet-rich fibrin (PRF), an intimate assembly of cytokines, glycan chains, and structural glycoproteins enmeshed within a slowly polymerized fibrin network, has the potential to accelerate soft and hard tissue healing. The present study aims to explore the clinical and radiographical outcome of NcHA bone graft with or without PRF, in the treatment of intrabony periodontal defects. Materials and Methods: In a split-mouth study design, 20 patients having two almost identical intrabony defects with clinical probing depth of at least 6 mm were selected for the study. Selected sites were randomly divided into two groups. In Group I, mucoperiosteal flap elevation followed by the placement of NcHA was done. In Group II, mucoperiosteal flap elevation, followed by the placement of NcHA with PRF was done. Clinical and radiographic parameters were recorded at baseline and at 6-month postoperatively. Results: Both treatment groups showed a significant probing pocket depth (PPD) reduction, clinical attachment gain, increase bone density 6-month after surgery compared with baseline. However, there was a significantly greater PPD reduction and clinical attachment gain when PRF was added to NcHA. Conclusion: The NcHA bone graft in combination with PRF demonstrated clinical advantages beyond that achieved by the NcHA alone. PMID:25810595

Nano-hydroxyapatite and its applications in preventive, restorative and regenerative dentistry: a review of literature.

PubMed

Pepla, Erlind; Besharat, Lait Kostantinos; Palaia, Gaspare; Tenore, Gianluca; Migliau, Guido

2014-07-01

This study aims to critically summarize the literature about nano-hydroxyapatite. The purpose of this work is to analyze the benefits of using nano-hydroxyapatite in dentistry, especially for its preventive, restorative and regenerative applications. We also provide an overview of new dental materials, still experimental, which contain the nano-hydroxyapatite in its nano-crystalline form. Hydroxyapatite is one of the most studied biomaterials in the medical field for its proven biocompatibility and for being the main constituent of the mineral part of bone and teeth. In terms of restorative and preventive dentistry, nano-hydroxyapatite has significant remineralizing effects on initial enamel lesions, certainly superior to conventional fluoride, and good results on the sensitivity of the teeth. The nano-HA has also been used as an additive material, in order to improve already existing and widely used dental materials, in the restorative field (experimental addition to conventional glass ionomer cements, that has led to significant improvements in their mechanical properties). Because of its unique properties, such as the ability to chemically bond to bone, to not induce toxicity or inflammation and to stimulate bone growth through a direct action on osteoblasts, nano-HA has been widely used in periodontology and in oral and maxillofacial surgery. Its use in oral implantology, however, is a widely used practice established for years, as this substance has excellent osteoinductive capacity and improves bone-to-implant integration.

Rheological performance of bacterial cellulose based nonmineralized and mineralized hydrogel scaffolds

NASA Astrophysics Data System (ADS)

Basu, Probal; Saha, Nabanita; Bandyopadhyay, Smarak; Saha, Petr

2017-05-01

Bacterial cellulose (BC) based hydrogels (BC-PVP and BC-CMC) are modified with β-tri-calcium phosphate (β-TCP) and hydroxyapatite (HA) to improve the structural and functional properties of the existing hydrogel scaffolds. The modified hydrogels are then biomineralized with CaCO3 following liquid diffusion technique, where salt solutions of Na2CO3 (5.25 g/100 mL) and CaCl2 (7.35 g/100 mL) were involved. The BC-PVP and BC-CMC are being compared with the non-mineralized (BC-PVP-β-TCP/HA and BC-CMC-β-TCP/HA) and biomineralized (BC-PVP-β-TCP/HA-CaCO3 and BC-CMC-β-TCP/HA-CaCO3) hydrogels on the basis of their structural and rheological properties. The Fourier Transform Infrared (FTIR) spectral analysis demonstrated the presence of BC, CMC, PVP, β-TCP, HA in the non-mineralized and BC, CMC, PVP, β-TCP, HA and CaCO3 in the biomineralized samples. Interestingly, the morphological property of non-mineralized and biomineralized, hydrogels are different than that of BC-PVP and BC-CMC based novel biomaterials. The Scanning Electron Microscopic (SEM) images of the before mentioned samples reveal the denser structures than BC-PVP and BC-CMC, which exhibits the changes in their pore sizes. Concerning rheological analysis point of view, all the non-mineralized and biomineralized hydrogel scaffolds have shown significant elastic property. Additionally, the complex viscosity (η*) values have also found in decreasing order with the increase of angular frequency (ω) 0.1 rad.sec-1 to 100 rad.sec-1. All these BC based hydrogel scaffolds are elastic in nature, can be recommended for their application as an implant for bone tissue engineering.

Graft shrinkage and survival rate of implants after sinus floor elevation using a nanocrystalline hydroxyapatite embedded in silica gel matrix: a 1-year prospective study.

PubMed

El Hage, Marc; Abi Najm, Semaan; Bischof, Mvark; Nedir, Rabah; Carrel, Jean-Pierre; Bernard, Jean-Pierre

2012-06-01

The aims of this study were (1) to evaluate the vertical shrinkage percentage of nanocrystalline hydroxyapatite embedded in silica gel used for maxillary sinus floor elevation (SFE) and (2) to determine the survival rate of the implants 1 year after placement in the healed grafted sinuses. Eleven maxillary sinuses were augmented in eight patients with NanoBone. After a healing period averaging 14.42 months, 19 implants were placed and followed up with clinical and radiographic evaluation. Panoramic radiographs were taken immediately after SFE and at 12 months after grafting. Measurements of changes in height were made by a computerized measuring technique using an image editing software. The mean graft height shrinkage percentage at 12 months after surgery was 8.84% (±5.32). One implant was lost before loading. All the 18 remaining osseointegrated implants received the prosthetic rehabilitation and were controlled after 3 months of functional loading. The implant survival rate at the 1-year interval was 94.74%. A 100% NanoBone alloplastic graft used in lateral SFE procedures presented limited height shrinkage. Implants placed in these grafted sinuses showed survival rates similar to those found in published data. These results should be interpreted cautiously considering the study's reduced sample size.

Nanocrystalline hydroxyapatite bone substitute leads to sufficient bone tissue formation already after 3 months: histological and histomorphometrical analysis 3 and 6 months following human sinus cavity augmentation.

PubMed

Ghanaati, Shahram; Barbeck, Mike; Willershausen, Ines; Thimm, Benjamin; Stuebinger, Stefan; Korzinskas, Tadas; Obreja, Karina; Landes, Constantin; Kirkpatrick, Charles J; Sader, Robert A

2013-12-01

In this study the de novo bone formation capacity of a nanocrystalline hydroxyapatite bone substitute was assessed 3 and 6 months after its insertion into the human sinus cavity. Sinus cavity augmentation was performed in a total of 14 patients (n = 7 implantation after 3 months; n = 7 implantation after 6 months) with severely atrophic maxillary bone. The specimens obtained after 3 and 6 months were analyzed histologically and histomorphometrically with special focus on bone metabolism within the residual bone and the augmented region. This study revealed that bone tissue formation started from the bone-biomaterial-interface and was directed into the most cranial parts of the augmented region. There was no statistically significant difference in new bone formation after 3 and 6 months (24.89 ± 10.22% vs 31.29 ± 2.29%), respectively. Within the limits of the present study and according to previously published data, implant insertion in regions augmented with this bone substitute material could be considered already after 3 months. Further clinical studies with bone substitute materials are necessary to validate these findings. © 2012 Wiley Periodicals, Inc.

A bioprintable form of chitosan hydrogel for bone tissue engineering.

PubMed

Demirtaş, Tuğrul Tolga; Irmak, Gülseren; Gümüşderelioğlu, Menemşe

2017-07-13

Bioprinting can be defined as 3D patterning of living cells and other biologics by filling and assembling them using a computer-aided layer-by-layer deposition approach to fabricate living tissue and organ analogs for tissue engineering. The presence of cells within the ink to use a 'bio-ink' presents the potential to print 3D structures that can be implanted or printed into damaged/diseased bone tissue to promote highly controlled cell-based regeneration and remineralization of bone. In this study, it was shown for the first time that chitosan solution and its composite with nanostructured bone-like hydroxyapatite (HA) can be mixed with cells and printed successfully. MC3T3-E1 pre-osteoblast cell laden chitosan and chitosan-HA hydrogels, which were printed with the use of an extruder-based bioprinter, were characterized by comparing these hydrogels to alginate and alginate-HA hydrogels. Rheological analysis showed that all groups had viscoelastic properties. It was also shown that under simulated physiological conditions, chitosan and chitosan-HA hydrogels were stable. Also, the viscosity values of the bio-solutions were in an applicable range to be used in 3D bio-printers. Cell viability and proliferation analyses documented that after printing with bio-solutions, cells continued to be viable in all groups. It was observed that cells printed within chitosan-HA composite hydrogel had peak expression levels for early and late stages osteogenic markers. It was concluded that cells within chitosan and chitosan-HA hydrogels had mineralized and differentiated osteogenically after 21 days of culture. It was also discovered that chitosan is superior to alginate, which is the most widely used solution preferred in bioprinting systems, in terms of cell proliferation and differentiation. Thus, applicability and printability of chitosan as a bio-printing solution were clearly demonstrated. Furthermore, it was proven that the presence of bone-like nanostructured HA in

In vitro and in vivo investigation of bisphosphonate-loaded hydroxyapatite particles for peri-implant bone augmentation.

PubMed

Kettenberger, Ulrike; Luginbuehl, Vera; Procter, Philip; Pioletti, Dominique P

2017-07-01

Locally applied bisphosphonates, such as zoledronate, have been shown in several studies to inhibit peri-implant bone resorption and recently to enhance peri-implant bone formation. Studies have also demonstrated positive effects of hydroxyapatite (HA) particles on peri-implant bone regeneration and an enhancement of the anti-resorptive effect of bisphosphonates in the presence of calcium. In the present study, both hydroxyapatite nanoparticles (nHA) and zoledronate were combined to achieve a strong reinforcing effect on peri-implant bone. The nHA-zoledronate combination was first investigated in vitro with a pre-osteoclastic cell assay (RAW 264.7) and then in vivo in a rat model of postmenopausal osteoporosis. The in vitro study confirmed that the inhibitory effect of zoledronate on murine osteoclast precursor cells was enhanced by loading the drug on nHA. For the in vivo investigation, either zoledronate-loaded or pure nHA were integrated in hyaluronic acid hydrogel. The gels were injected in screw holes that had been predrilled in rat femoral condyles before the insertion of miniature screws. Micro-CT-based dynamic histomorphometry and histology revealed an unexpected rapid mineralization of the hydrogel in vivo through formation of granules, which served as scaffold for new bone formation. The delivery of zoledronate-loaded nHA further inhibited a degradation of the mineralized hydrogel as well as a resorption of the peri-implant bone as effectively as unbound zoledronate. Hyaluronic acid with zoledronate-loaded nHA, thanks to its dual effect on inducing a rapid mineralization and preventing resorption, is a promising versatile material for bone repair and augmentation. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

Novel self-gelling injectable hydrogel/alpha-tricalcium phosphate composites for bone regeneration: Physiochemical and microcomputer tomographical characterization.

PubMed

Douglas, Timothy E L; Schietse, Josefien; Zima, Aneta; Gorodzha, Svetlana; Parakhonskiy, Bogdan V; KhaleNkow, Dmitry; Shkarin, Roman; Ivanova, Anna; Baumbach, Tilo; Weinhardt, Venera; Stevens, Christian V; Vanhoorne, Valérie; Vervaet, Chris; Balcaen, Lieve; Vanhaecke, Frank; Slośarczyk, Anna; Surmeneva, Maria A; Surmenev, Roman A; Skirtach, Andre G

2018-03-01

Mineralized hydrogels are increasingly gaining attention as biomaterials for bone regeneration. The most common mineralization strategy has been addition of preformed inorganic particles during hydrogel formation. This maintains injectability. One common form of bone cement is formed by mixing particles of the highly reactive calcium phosphate alpha-tricalcium phosphate (α-TCP) with water to form hydroxyapatite (HA). The calcium ions released during this reaction can be exploited to crosslink anionic, calcium-binding polymers such as the polysaccharide gellan gum (GG) to induce hydrogel formation. In this study, three different amounts of α-TCP particles were added to GG polymer solution to generate novel, injectable hydrogel-inorganic composites. Distribution of the inorganic phase in the hydrogel was studied by high resolution microcomputer tomography (µCT). Gelation occurred within 30 min. α-TCP converted to HA. µCT revealed inhomogeneous distribution of the inorganic phase in the composites. These results demonstrate the potential of the composites as alternatives to traditional α-TCP bone cement and pave the way for incorporation of biologically active substances and in vitro and in vivo testing. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 822-828, 2018. © 2017 Wiley Periodicals, Inc.

Multiscale Modulation of Nanocrystalline Cellulose Hydrogel via Nanocarbon Hybridization for 3D Neuronal Bilayer Formation.

PubMed

Kim, Dongyoon; Park, Subeom; Jo, Insu; Kim, Seong-Min; Kang, Dong Hee; Cho, Sung-Pyo; Park, Jong Bo; Hong, Byung Hee; Yoon, Myung-Han

2017-07-01

Bacterial biopolymers have drawn much attention owing to their unconventional three-dimensional structures and interesting functions, which are closely integrated with bacterial physiology. The nongenetic modulation of bacterial (Acetobacter xylinum) cellulose synthesis via nanocarbon hybridization, and its application to the emulation of layered neuronal tissue, is reported. The controlled dispersion of graphene oxide (GO) nanoflakes into bacterial cellulose (BC) culture media not only induces structural changes within a crystalline cellulose nanofibril, but also modulates their 3D collective association, leading to substantial reduction in Young's modulus (≈50%) and clear definition of water-hydrogel interfaces. Furthermore, real-time investigation of 3D neuronal networks constructed in this GO-incorporated BC hydrogel with broken chiral nematic ordering revealed the vertical locomotion of growth cones, the accelerated neurite outgrowth (≈100 µm per day) with reduced backward travel length, and the efficient formation of synaptic connectivity with distinct axonal bifurcation abundancy at the ≈750 µm outgrowth from a cell body. In comparison with the pristine BC, GO-BC supports the formation of well-defined neuronal bilayer networks with flattened interfacial profiles and vertical axonal outgrowth, apparently emulating the neuronal development in vivo. We envisioned that our findings may contribute to various applications of engineered BC hydrogel to fundamental neurobiology studies and neural engineering. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nanocrystalline ceramic materials

DOEpatents

Siegel, Richard W.; Nieman, G. William; Weertman, Julia R.

1994-01-01

A method for preparing a treated nanocrystalline metallic material. The method of preparation includes providing a starting nanocrystalline metallic material with a grain size less than about 35 nm, compacting the starting nanocrystalline metallic material in an inert atmosphere and annealing the compacted metallic material at a temperature less than about one-half the melting point of the metallic material.

Nanocrystalline ceramic materials

DOEpatents

Siegel, R.W.; Nieman, G.W.; Weertman, J.R.

1994-06-14

A method is disclosed for preparing a treated nanocrystalline metallic material. The method of preparation includes providing a starting nanocrystalline metallic material with a grain size less than about 35 nm, compacting the starting nanocrystalline metallic material in an inert atmosphere and annealing the compacted metallic material at a temperature less than about one-half the melting point of the metallic material. 19 figs.

Microscale Characterization of the Viscoelastic Properties of Hydrogel Biomaterials using Dual-Mode Ultrasound Elastography

PubMed Central

Hong, Xiaowei; Stegemann, Jan P.; Deng, Cheri X.

2016-01-01

Characterization of the microscale mechanical properties of biomaterials is a key challenge in the field of mechanobiology. Dual-mode ultrasound elastography (DUE) uses high frequency focused ultrasound to induce compression in a sample, combined with interleaved ultrasound imaging to measure the resulting deformation. This technique can be used to non-invasively perform creep testing on hydrogel biomaterials to characterize their viscoelastic properties. DUE was applied to a range of hydrogel constructs consisting of either hydroxyapatite (HA)-doped agarose, HA-collagen, HA-fibrin, or preosteoblast-seeded collagen constructs. DUE provided spatial and temporal mapping of local and bulk displacements and strains at high resolution. Hydrogel materials exhibited characteristic creep behavior, and the maximum strain and residual strain were both material- and concentration-dependent. Burger’s viscoelastic model was used to extract characteristic parameters describing material behavior. Increased protein concentration resulted in greater stiffness and viscosity, but did not affect the viscoelastic time constant of acellular constructs. Collagen constructs exhibited significantly higher modulus and viscosity than fibrin constructs. Cell-seeded collagen constructs became stiffer with altered mechanical behavior as they developed over time. Importantly, DUE also provides insight into the spatial variation of viscoelastic properties at sub-millimeter resolution, allowing interrogation of the interior of constructs. DUE presents a novel technique for non-invasively characterizing hydrogel materials at the microscale, and therefore may have unique utility in the study of mechanobiology and the characterization of hydrogel biomaterials. PMID:26928595

Microscale characterization of the viscoelastic properties of hydrogel biomaterials using dual-mode ultrasound elastography.

PubMed

Hong, Xiaowei; Stegemann, Jan P; Deng, Cheri X

2016-05-01

Characterization of the microscale mechanical properties of biomaterials is a key challenge in the field of mechanobiology. Dual-mode ultrasound elastography (DUE) uses high frequency focused ultrasound to induce compression in a sample, combined with interleaved ultrasound imaging to measure the resulting deformation. This technique can be used to non-invasively perform creep testing on hydrogel biomaterials to characterize their viscoelastic properties. DUE was applied to a range of hydrogel constructs consisting of either hydroxyapatite (HA)-doped agarose, HA-collagen, HA-fibrin, or preosteoblast-seeded collagen constructs. DUE provided spatial and temporal mapping of local and bulk displacements and strains at high resolution. Hydrogel materials exhibited characteristic creep behavior, and the maximum strain and residual strain were both material- and concentration-dependent. Burger's viscoelastic model was used to extract characteristic parameters describing material behavior. Increased protein concentration resulted in greater stiffness and viscosity, but did not affect the viscoelastic time constant of acellular constructs. Collagen constructs exhibited significantly higher modulus and viscosity than fibrin constructs. Cell-seeded collagen constructs became stiffer with altered mechanical behavior as they developed over time. Importantly, DUE also provides insight into the spatial variation of viscoelastic properties at sub-millimeter resolution, allowing interrogation of the interior of constructs. DUE presents a novel technique for non-invasively characterizing hydrogel materials at the microscale, and therefore may have unique utility in the study of mechanobiology and the characterization of hydrogel biomaterials. Copyright © 2016 Elsevier Ltd. All rights reserved.

XPS and XANES studies of biomimetic composites based on B-type nano-hydroxyapatite

NASA Astrophysics Data System (ADS)

Goloshchapov, D. L.; Gushchin, M. S.; Kashkarov, V. M.; Seredin, P. V.; Ippolitov, Y. A.; Khmelevsky, N. O.; Aksenenko, A. Yu.

2018-06-01

The paper presents an investigation of the local atomic structure of nanocrystalline carbonate-substituted hydroxyapatite (CHAP) contained in biomimetic composites - analogues of intact human tooth tissues. Using the XPS technique, the presence of impurity Mg and F atoms and structurally bound carbon in CHAP, at the concentrations typical of apatite enamel and dentine was determined. The XANES method was used to study the changes occurring in P L2,3 spectra of biocomposites with CHAP, depending on the percentage of the amino acid matrix. The appearance of maxima in the spectra of XANES P L2,3 near 135.7 eV for the samples with the composition of amino acid complex/hydroxyapatite - 5/95, 25/75 and the splitting of a broad peak of 146.9 eV in the spectrum of a biocomposite with a composition of 40/60 indicates at the interaction of molecular complex of amino acids with atomic environment of phosphorus. This fact can be used in the fundamental medicine for synthesizing of new biomaterials in dentistry.

Host cell recruitment patterns by bone morphogenetic protein-2 releasing hyaluronic acid hydrogels in a mouse subcutaneous environment.

PubMed

Todeschi, Maria R; El Backly, Rania M; Varghese, Oommen P; Hilborn, Jöns; Cancedda, Ranieri; Mastrogiacomo, Maddalena

2017-07-01

This study aimed to identify host cell recruitment patterns in a mouse model in response to rhBMP-2 releasing hyaluronic acid hydrogels and influence of added nano-hydroxyapatite particles on rhBMP-2 release and pattern of bone formation. Implanted gels were retrieved after implantation and cells were enzymatically dissociated for flow cytometric analysis. Percentages of macrophages, progenitor endothelial cells and putative mesenchymal stem cells were measured. Implants were evaluated for BMP-2 release by ELISA and by histology to monitor tissue formation. Hyaluronic acid+BMP-2 gels influenced the inflammatory response in the bone healing microenvironment. Host-derived putative mesenchymal stem cells were major contributors. Addition of hydroxyapatite nanoparticles modified the release pattern of rhBMP-2, resulting in enhanced bone formation.

Prevascularization of 3D printed bone scaffolds by bioactive hydrogels and cell co-culture.

PubMed

Kuss, Mitchell A; Wu, Shaohua; Wang, Ying; Untrauer, Jason B; Li, Wenlong; Lim, Jung Yul; Duan, Bin

2017-09-13

Vascularization is a fundamental prerequisite for large bone construct development and remains one of the main challenges of bone tissue engineering. Our current study presents the combination of 3D printing technique with a hydrogel-based prevascularization strategy to generate prevascularized bone constructs. Human adipose derived mesenchymal stem cells (ADMSC) and human umbilical vein endothelial cells (HUVEC) were encapsulated within our bioactive hydrogels, and the effects of culture conditions on in vitro vascularization were determined. We further generated composite constructs by forming 3D printed polycaprolactone/hydroxyapatite scaffolds coated with cell-laden hydrogels and determined how the co-culture affected vascularization and osteogenesis. It was demonstrated that 3D co-cultured ADMSC-HUVEC generated capillary-like networks within the porous 3D printed scaffold. The co-culture systems promoted in vitro vascularization, but had no significant effects on osteogenesis. The prevascularized constructs were subcutaneously implanted into nude mice to evaluate the in vivo vascularization capacity and the functionality of engineered vessels. The hydrogel systems facilitated microvessel and lumen formation and promoted anastomosis of vascular networks of human origin with host murine vasculature. These findings demonstrate the potential of prevascularized 3D printed scaffolds with anatomical shape for the healing of larger bone defects. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2017. © 2017 Wiley Periodicals, Inc.

Mechanical properties of nanocrystalline cobalt

NASA Astrophysics Data System (ADS)

Karimpoor, Amir A.; Erb, Uwe

2006-05-01

Due to their excellent wear and corrosion properties, nanocrystalline cobalt and several cobalt alloys made by electrodeposition are currently being developed as environmentally benign replacement coatings for hard chromium electrodeposits. The focus of this study is on the mechanical properties of nanocrystalline cobalt, which are currently not well understood. A comparison is presented for hardness, tensile properties, Charpy impact properties and fracture surface analysis of both nanocrystalline (grain size: 12 nm) and conventional polycrystalline (grain size: 4.8 m) cobalt. It is shown that the hardness and tensile strength of nanocrystalline cobalt is 2-3 times higher than for polycrystalline cobalt. However, in contrast to other nanocrystalline materials tested previously, nanocrystalline cobalt retains considerable ductility with elongation to fracture values up to 7%.

Implantation of silicon dioxide-based nanocrystalline hydroxyapatite and pure phase beta-tricalciumphosphate bone substitute granules in caprine muscle tissue does not induce new bone formation.

PubMed

Ghanaati, Shahram; Udeabor, Samuel E; Barbeck, Mike; Willershausen, Ines; Kuenzel, Oliver; Sader, Robert A; Kirkpatrick, C James

2013-01-04

Osteoinductive bone substitutes are defined by their ability to induce new bone formation even at heterotopic implantation sites. The present study was designed to analyze the potential osteoinductivity of two different bone substitute materials in caprine muscle tissue. One gram each of either a porous beta-tricalcium phosphate (β-TCP) or an hydroxyapatite/silicon dioxide (HA/SiO2)-based nanocrystalline bone substitute material was implanted in several muscle pouches of goats. The biomaterials were explanted at 29, 91 and 181 days after implantation. Conventional histology and special histochemical stains were performed to detect osteoblast precursor cells as well as mineralized and unmineralized bone matrix. Both materials underwent cellular degradation in which tartrate-resistant acid phosphatase (TRAP)-positive osteoclast-like cells and TRAP-negative multinucleated giant cells were involved. The ß-TCP was completely resorbed within the observation period, whereas some granules of the HA-groups were still detectable after 180 days. Neither osteoblasts, osteoblast precursor cells nor extracellular bone matrix were found within the implantation bed of any of the analyzed biomaterials at any of the observed time points. This study showed that ß-TCP underwent a faster degradation than the HA-based material. The lack of osteoinductivity for both materials might be due to their granular shape, as osteoinductivity in goat muscle has been mainly attributed to cylindrical or disc-shaped bone substitute materials. This hypothesis however requires further investigation to systematically analyze various materials with comparable characteristics in the same experimental setting.

Antibacterial activity of silver-doped hydroxyapatite nanoparticles against gram-positive and gram-negative bacteria

NASA Astrophysics Data System (ADS)

Ciobanu, Carmen Steluta; Iconaru, Simona Liliana; Le Coustumer, Phillippe; Constantin, Liliana Violeta; Predoi, Daniela

2012-06-01

Ag-doped nanocrystalline hydroxyapatite nanoparticles (Ag:HAp-NPs) (Ca10- x Ag x (PO4)6(OH)2, x Ag = 0.05, 0.2, and 0.3) with antibacterial properties are of great interest in the development of new products. Coprecipitation method is a promising route for obtaining nanocrystalline Ag:HAp with antibacterial properties. X-ray diffraction identified HAp as an unique crystalline phase in each sample. The calculated lattice constants of a = b = 9.435 Å, c = 6.876 Å for x Ag = 0.05, a = b = 9.443 Å, c = 6.875 Å for x Ag = 0.2, and a = b = 9.445 Å, c = 6.877 Å for x Ag = 0.3 are in good agreement with the standard of a = b = 9.418 Å, c = 6.884 Å (space group P63/m). The Fourier transform infrared and Raman spectra of the sintered HAp show the absorption bands characteristic to hydroxyapatite. The Ag:HAp nanoparticles are evaluated for their antibacterial activity against Staphylococcus aureus, Klebsiella pneumoniae, Providencia stuartii, Citrobacter freundii and Serratia marcescens. The results showed that the antibacterial activity of these materials, regardless of the sample types, was greatest against S. aureus, K. pneumoniae, P. stuartii, and C. freundii. The results of qualitative antibacterial tests revealed that the tested Ag:HAp-NPs had an important inhibitory activity on P. stuartii and C. freundii. The absorbance values measured at 490 nm of the P. stuartii and C. freundii in the presence of Ag:HAp-NPs decreased compared with those of organic solvent used (DMSO) for all the samples ( x Ag = 0.05, 0.2, and 0.3). Antibacterial activity increased with the increase of x Ag in the samples. The Ag:HAp-NP concentration had little influence on the bacterial growth ( P. stuartii).

Engineering the bone-ligament interface using polyethylene glycol diacrylate incorporated with hydroxyapatite.

PubMed

Paxton, Jennifer Z; Donnelly, Kenneth; Keatch, Robert P; Baar, Keith

2009-06-01

Ligaments and tendons have previously been tissue engineered. However, without the bone attachment, implantation of a tissue-engineered ligament would require it to be sutured to the remnant of the injured native tissue. Due to slow repair and remodeling, this would result in a chronically weak tissue that may never return to preinjury function. In contrast, orthopaedic autograft reconstruction of the ligament often uses a bone-to-bone technique for optimal repair. Since bone-to-bone repairs heal better than other methods, implantation of an artificial ligament should also occur from bone-to-bone. The aim of this study was to investigate the use of a poly(ethylene glycol) diacrylate (PEGDA) hydrogel incorporated with hydroxyapatite (HA) and the cell-adhesion peptide RGD (Arg-Gly-Asp) as a material for creating an in vitro tissue interface to engineer intact ligaments (i.e., bone-ligament-bone). Incorporation of HA into PEG hydrogels reduced the swelling ratio but increased mechanical strength and stiffness of the hydrogels. Further, HA addition increased the capacity for cell growth and interface formation. RGD incorporation increased the swelling ratio but decreased mechanical strength and stiffness of the material. Optimum levels of cell attachment were met using a combination of both HA and RGD, but this material had no better mechanical properties than PEG alone. Although adherence of the hydrogels containing HA was achieved, failure occurs at about 4 days with 5% HA. Increasing the proportion of HA improved interface formation; however, with high levels of HA, the PEG HA composite became brittle. This data suggests that HA, by itself or with other materials, might be well suited for engineering the ligament-bone interface.

Property-based design: optimization and characterization of polyvinyl alcohol (PVA) hydrogel and PVA-matrix composite for artificial cornea.

PubMed

Jiang, Hong; Zuo, Yi; Zhang, Li; Li, Jidong; Zhang, Aiming; Li, Yubao; Yang, Xiaochao

2014-03-01

Each approach for artificial cornea design is toward the same goal: to develop a material that best mimics the important properties of natural cornea. Accordingly, the selection and optimization of corneal substitute should be based on their physicochemical properties. In this study, three types of polyvinyl alcohol (PVA) hydrogels with different polymerization degree (PVA1799, PVA2499 and PVA2699) were prepared by freeze-thawing techniques. After characterization in terms of transparency, water content, water contact angle, mechanical property, root-mean-square roughness and protein adsorption behavior, the optimized PVA2499 hydrogel with similar properties of natural cornea was selected as a matrix material for artificial cornea. Based on this, a biomimetic artificial cornea was fabricated with core-and-skirt structure: a transparent PVA hydrogel core, surrounding by a ringed PVA-matrix composite skirt that composed of graphite, Fe-doped nano hydroxyapatite (n-Fe-HA) and PVA hydrogel. Different ratio of graphite/n-Fe-HA can tune the skirt color from dark brown to light brown, which well simulates the iris color of Oriental eyes. Moreover, morphologic and mechanical examination showed that an integrated core-and-skirt artificial cornea was formed from an interpenetrating polymer network, no phase separation appeared on the interface between the core and the skirt.

Ultrasound-assisted green economic synthesis of hydroxyapatite nanoparticles using eggshell biowaste and study of mechanical and biological properties for orthopedic applications.

PubMed

Ingole, Vijay H; Hany Hussein, Kamal; Kashale, Anil A; Ghule, Kalyani; Vuherer, Tomaž; Kokol, Vanja; Chang, Jia-Yaw; Ling, Yong-Chien; Vinchurkar, Aruna; Dhakal, Hom N; Ghule, Anil V

2017-11-01

Nanostructured hydroxyapatite (HAp) is the most favorable candidate biomaterial for bone tissue engineering because of its bioactive and osteoconductive properties. Herein, we report for the first time ultrasound-assisted facile and economic approach for the synthesis of nanocrystalline hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 ) using recycled eggshell biowaste referred as EHAp. The process involves the reaction of eggshell biowaste as a source of calcium and ammonium dihydrogen orthophosphate as a phosphate source. Ultrasound-mediated chemical synthesis of hydroxyapatite (HAp) is also carried out using similar approach wherein commercially available calcium hydroxide and ammonium dihydrogen orthophosphate were used as calcium and phosphate precursors, respectively and referred as CHAp for better comparison. The prepared materials were characterized by X-ray diffraction, field emission scanning electron microscopy, Fourier transform infrared spectroscopy, and Raman spectroscopy to determine crystal structure, particle morphology, and the presence of chemical functional groups. The nanocrystalline EHAp and CHAp were observed to have spherical morphology with uniform size distribution. Furthermore, mechanical properties such as Vickers hardness, fracture toughness, and compression tests have been studied of the EHAp and CHAp samples showing promising results. Mechanical properties show the influence of calcination at 600°C EHAp and CHAp material. After calcination, in the case of EHAp material an average hardness, mechanical strength, elastic modulus, and fracture toughness were found 552 MPa, 46.6 MPa, 2824 MPa, and 3.85 MPa m 1/2 , respectively, while in the case of CHAp 618 MPa, 47.5 MPa, 2071 MPa, and 3.13 MPa m 1/2 . In vitro cell studies revealed that the EHAp and CHAp nanoparticles significantly increased the attachment and proliferation of the hFOB cells. Here, we showed that EHAp and CHAp provide promising biocompatible materials that do not affect the cell

Cold Spray Coating of Submicronic Ceramic Particles on Poly(vinyl alcohol) in Dry and Hydrogel States

NASA Astrophysics Data System (ADS)

Moreau, David; Borit, François; Corté, Laurent; Guipont, Vincent

2017-06-01

We report an approach using cold spray technology to coat poly(vinyl alcohol) (PVA) in polymer and hydrogel states with hydroxyapatite (HA). Using porous aggregated HA powder, we hypothesized that fragmentation of the powder upon cold spray could lead to formation of a ceramic coating on the surface of the PVA substrate. However, direct spraying of this powder led to complete destruction of the swollen PVA hydrogel substrate. As an alternative, HA coatings were successfully produced by spraying onto dry PVA substrates prior to swelling in water. Dense homogeneous HA coatings composed of submicron particles were obtained using rather low-energy spraying parameters (temperature 200-250 °C, pressure 1-3 MPa). Coated PVA substrates could swell in water without removal of the ceramic layer to form HA-coated hydrogels. Microscopic observations and in situ measurements were used to explain how local heating and impact of sprayed aggregates induced surface roughening and strong binding of HA particles to the molten PVA substrate. Such an approach could lead to design of ceramic coatings whose roughness and crystallinity can be finely adjusted to improve interfacing with biological tissues.

Supramolecular Hydrogelators and Hydrogels: From Soft Matter to Molecular Biomaterials

PubMed Central

2015-01-01

In this review we intend to provide a relatively comprehensive summary of the work of supramolecular hydrogelators after 2004 and to put emphasis particularly on the applications of supramolecular hydrogels/hydrogelators as molecular biomaterials. After a brief introduction of methods for generating supramolecular hydrogels, we discuss supramolecular hydrogelators on the basis of their categories, such as small organic molecules, coordination complexes, peptides, nucleobases, and saccharides. Following molecular design, we focus on various potential applications of supramolecular hydrogels as molecular biomaterials, classified by their applications in cell cultures, tissue engineering, cell behavior, imaging, and unique applications of hydrogelators. Particularly, we discuss the applications of supramolecular hydrogelators after they form supramolecular assemblies but prior to reaching the critical gelation concentration because this subject is less explored but may hold equally great promise for helping address fundamental questions about the mechanisms or the consequences of the self-assembly of molecules, including low molecular weight ones. Finally, we provide a perspective on supramolecular hydrogelators. We hope that this review will serve as an updated introduction and reference for researchers who are interested in exploring supramolecular hydrogelators as molecular biomaterials for addressing the societal needs at various frontiers. PMID:26646318

Experimental and numerical measurements of adhesion energies between PHEMA and PGLYMA with hydroxyapatite crystal.

PubMed

Youssefian, Sina; Liu, Pingsheng; Askarinejad, Sina; Shalchy, Faezeh; Song, Jie; Rahbar, Nima

2015-07-16

Synthetic orthopaedic materials consisting of a single bioinert polymeric material do not meet the complex biological and physical requirements of scaffold-guided bone tissue repair and regeneration. Of particular interest is the design of biocompatible hydrogel-hydroxyapatite composite bone substitutes with outstanding interfacial adhesion that would warranty the ability for the composite to withstand functional loadings without exhibiting brittle fractures during the dynamic guided tissue regeneration. For this purpose, the hydroxylated side chain of chemically cross-linked poly (2-hydroxyethyl methacrylate) (pHEMA) is substitute with a carboxylated side chain to make poly (glycerol methacrylate) (pGLYMA). Here, we carry out atomistic simulations and atomic force microscopy to predict and experimentally determine the interfacial adhesion energies of pHEMA and pGLYMA with the surface of single-crystalline hydroxyapatite (HA) whiskers. Both experimental and numerical results showed that pGLYMA has stronger adhesion forces with HA and may be used for preparing a high-affinity polymer-HA composite. The high adhesive interactions between pGLYMA and HA were found to be due to strong electrostatic energies.

Implantation of silicon dioxide-based nanocrystalline hydroxyapatite and pure phase beta-tricalciumphosphate bone substitute granules in caprine muscle tissue does not induce new bone formation

PubMed Central

2013-01-01

Background Osteoinductive bone substitutes are defined by their ability to induce new bone formation even at heterotopic implantation sites. The present study was designed to analyze the potential osteoinductivity of two different bone substitute materials in caprine muscle tissue. Materials and methods One gram each of either a porous beta-tricalcium phosphate (β-TCP) or an hydroxyapatite/silicon dioxide (HA/SiO2)-based nanocrystalline bone substitute material was implanted in several muscle pouches of goats. The biomaterials were explanted at 29, 91 and 181 days after implantation. Conventional histology and special histochemical stains were performed to detect osteoblast precursor cells as well as mineralized and unmineralized bone matrix. Results Both materials underwent cellular degradation in which tartrate-resistant acid phosphatase (TRAP)-positive osteoclast-like cells and TRAP-negative multinucleated giant cells were involved. The ß-TCP was completely resorbed within the observation period, whereas some granules of the HA-groups were still detectable after 180 days. Neither osteoblasts, osteoblast precursor cells nor extracellular bone matrix were found within the implantation bed of any of the analyzed biomaterials at any of the observed time points. Conclusions This study showed that ß-TCP underwent a faster degradation than the HA-based material. The lack of osteoinductivity for both materials might be due to their granular shape, as osteoinductivity in goat muscle has been mainly attributed to cylindrical or disc-shaped bone substitute materials. This hypothesis however requires further investigation to systematically analyze various materials with comparable characteristics in the same experimental setting. PMID:23286366

Hydrogel ionotronics

NASA Astrophysics Data System (ADS)

Yang, Canhui; Suo, Zhigang

2018-06-01

An ionotronic device functions by a hybrid circuit of mobile ions and mobile electrons. Hydrogels are stretchable, transparent, ionic conductors that can transmit electrical signals of high frequency over long distance, enabling ionotronic devices such as artificial muscles, skins and axons. Moreover, ionotronic luminescent devices, ionotronic liquid crystal devices, touchpads, triboelectric generators, artificial eels and gel-elastomer-oil devices can be designed based on hydrogels. In this Review, we discuss first-generation hydrogel ionotronic devices and the challenges associated with the mechanical properties and the chemistry of the materials. We examine how strong and stretchable adhesion between hydrophilic and hydrophobic polymer networks can be achieved, how water can be retained in hydrogels and how to design hydrogels that resist fatigue under cyclic loads. Finally, we highlight applications of hydrogel ionotronic devices and discuss the future of the field.

Thermally Stable Nanocrystalline Steel

NASA Astrophysics Data System (ADS)

Hulme-Smith, Christopher Neil; Ooi, Shgh Woei; Bhadeshia, Harshad K. D. H.

2017-10-01

Two novel nanocrystalline steels were designed to withstand elevated temperatures without catastrophic microstructural changes. In the most successful alloy, a large quantity of nickel was added to stabilize austenite and allow a reduction in the carbon content. A 50 kg cast of the novel alloy was produced and used to verify the formation of nanocrystalline bainite. Synchrotron X-ray diffractometry using in situ heating showed that austenite was able to survive more than 1 hour at 773 K (500 °C) and subsequent cooling to ambient temperature. This is the first reported nanocrystalline steel with high-temperature capability.

Antibacterial activity of silver-doped hydroxyapatite nanoparticles against gram-positive and gram-negative bacteria

PubMed Central

2012-01-01

Ag-doped nanocrystalline hydroxyapatite nanoparticles (Ag:HAp-NPs) (Ca10-xAgx(PO4)6(OH)2, xAg = 0.05, 0.2, and 0.3) with antibacterial properties are of great interest in the development of new products. Coprecipitation method is a promising route for obtaining nanocrystalline Ag:HAp with antibacterial properties. X-ray diffraction identified HAp as an unique crystalline phase in each sample. The calculated lattice constants of a = b = 9.435 Å, c = 6.876 Å for xAg = 0.05, a = b = 9.443 Å, c = 6.875 Å for xAg = 0.2, and a = b = 9.445 Å, c = 6.877 Å for xAg = 0.3 are in good agreement with the standard of a = b = 9.418 Å, c = 6.884 Å (space group P63/m). The Fourier transform infrared and Raman spectra of the sintered HAp show the absorption bands characteristic to hydroxyapatite. The Ag:HAp nanoparticles are evaluated for their antibacterial activity against Staphylococcus aureus, Klebsiella pneumoniae, Providencia stuartii, Citrobacter freundii and Serratia marcescens. The results showed that the antibacterial activity of these materials, regardless of the sample types, was greatest against S. aureus, K. pneumoniae, P. stuartii, and C. freundii. The results of qualitative antibacterial tests revealed that the tested Ag:HAp-NPs had an important inhibitory activity on P. stuartii and C. freundii. The absorbance values measured at 490 nm of the P. stuartii and C. freundii in the presence of Ag:HAp-NPs decreased compared with those of organic solvent used (DMSO) for all the samples (xAg = 0.05, 0.2, and 0.3). Antibacterial activity increased with the increase of xAg in the samples. The Ag:HAp-NP concentration had little influence on the bacterial growth (P. stuartii). PMID:22721352

Antibacterial activity of silver-doped hydroxyapatite nanoparticles against gram-positive and gram-negative bacteria.

PubMed

Ciobanu, Carmen Steluta; Iconaru, Simona Liliana; Le Coustumer, Phillippe; Constantin, Liliana Violeta; Predoi, Daniela

2012-06-21

Ag-doped nanocrystalline hydroxyapatite nanoparticles (Ag:HAp-NPs) (Ca10-xAgx(PO4)6(OH)2, xAg = 0.05, 0.2, and 0.3) with antibacterial properties are of great interest in the development of new products. Coprecipitation method is a promising route for obtaining nanocrystalline Ag:HAp with antibacterial properties. X-ray diffraction identified HAp as an unique crystalline phase in each sample. The calculated lattice constants of a = b = 9.435 Å, c = 6.876 Å for xAg = 0.05, a = b = 9.443 Å, c = 6.875 Å for xAg = 0.2, and a = b = 9.445 Å, c = 6.877 Å for xAg = 0.3 are in good agreement with the standard of a = b = 9.418 Å, c = 6.884 Å (space group P63/m). The Fourier transform infrared and Raman spectra of the sintered HAp show the absorption bands characteristic to hydroxyapatite. The Ag:HAp nanoparticles are evaluated for their antibacterial activity against Staphylococcus aureus, Klebsiella pneumoniae, Providencia stuartii, Citrobacter freundii and Serratia marcescens. The results showed that the antibacterial activity of these materials, regardless of the sample types, was greatest against S. aureus, K. pneumoniae, P. stuartii, and C. freundii. The results of qualitative antibacterial tests revealed that the tested Ag:HAp-NPs had an important inhibitory activity on P. stuartii and C. freundii. The absorbance values measured at 490 nm of the P. stuartii and C. freundii in the presence of Ag:HAp-NPs decreased compared with those of organic solvent used (DMSO) for all the samples (xAg = 0.05, 0.2, and 0.3). Antibacterial activity increased with the increase of xAg in the samples. The Ag:HAp-NP concentration had little influence on the bacterial growth (P. stuartii).

Europium concentration effect on characteristics and luminescent properties of hydroxyapatite nanocrystalline powders

NASA Astrophysics Data System (ADS)

Nikolaev, Anton; Kolesnikov, Ilya; Frank-Kamenetskaya, Olga; Kuz'mina, Maria

2017-12-01

Series of Eu-apatites were synthesized by precipitation from aqueous solutions with the Eu/Ca atomic ratio from 0.5% to 5% at T = 90 °C. Resulting precipitates were studied using different experimental techniques including X-ray powder diffraction, infrared and raman spectroscopy, scanning elecrton microscopy, EDX and photoluminescent spectroscopy. Eu-doped Ca-deficit nanosized non-stoichiometric hydroxyapatite with high water content has been obtained throughout the experiment. Europium content in the synthesized apatites reaches 0.24 apfu (Eu/Ca = 2.5%). Relations between Eu content is the solution and precipitate have been established. It was shown that Eu-monacite starts to precipitate as secondary phase at Eu/Ca ratio in starting solution 1% or higher. Maximum luminescence is observed in apatite with ∼2% Eu/Ca ratio (which equals to ∼0.2 apfu and corresponds to 3% Eu/Ca ratio in the starting solution). As an important and brand-new result, apatite with 2% Eu/Ca ratio can be considered as the most appropriate material for the producing biolabels for luminescent research in medicine and biology.

Dynamic properties of hydrogels and fiber-reinforced hydrogels.

PubMed

Martin, Nicholas; Youssef, George

2018-06-07

Hydrophilic polymers, or hydrogels, are used for a wide variety of biomedical applications, due to their inherent ability to withhold a high-water content. In recent years, a large effort has been focused on tailoring the mechanical properties of these hydrogels to become more appropriate materials for use as anatomical and physiological structural supports. A few of these such methods include using diverse types of polymers, both natural and synthetic, varying the type of molecular cross-linking, as well as combining these efforts to form interpenetrating polymer network hydrogels. While multiple research groups have characterized these various hydrogels under quasi-static conditions, their dynamic properties, representative of native physiological loading scenarios, have been scarcely reported. In this study, an E-glass fiber reinforced family of alginate/PAAm hydrogels cross-linked by both divalent and trivalent cations are fabricated and investigated. The effect of the reinforcement phase on the dynamic and hydration behaviors is then explicated. Additionally, a micromechanics framework for short cylindrical chopped fibers is utilized to discern the contribution of the matrix and fiber constituents on the hydrogel composite. The addition of E-glass fibers resulted in the storage modulus exhibiting a ~50%, 5%, and ~120%, increase with a mere addition of 2 wt% of the reinforcing fibers to Na-, Sr-, and Al-alginate/PAAm, respectively. In studying the cross-linking effect of various divalent (Ba, Ca, Sr) and trivalent (Al, Fe) cations, it was noteworthy that the hydrogels were found to be effective in dissipating energy while resisting mechanical deformation when they are cross-linked with higher molecular weight elements, regardless of valency. This report on the dynamic properties of these hydrogels will help to improve their optimization for future use in biomedical load-bearing applications. Copyright © 2018 Elsevier Ltd. All rights reserved.

Programmable hydrogels.

PubMed

Wang, Yong

2018-03-05

Programmable hydrogels are defined as hydrogels that are able to change their properties and functions periodically, reversibly and/or sequentially on demand. They are different from those responsive hydrogels whose changes are passive or cannot be stopped or reversed once started and vice versa. The purpose of this review is to summarize major progress in developing programmable hydrogels from the viewpoints of principles, functions and biomedical applications. The principles are first introduced in three categories including biological, chemical and physical stimulation. With the stimulation, programmable hydrogels can undergo functional changes in dimension, mechanical support, cell attachment and molecular sequestration, which are introduced in the middle of this review. The last section is focused on the introduction and discussion of four biomedical applications including mechanistic studies in mechanobiology, tissue engineering, cell separation and protein delivery. Copyright © 2018 Elsevier Ltd. All rights reserved.

Hydrogel research in Germany: the priority programme, Intelligent Hydrogels

NASA Astrophysics Data System (ADS)

Wallmersperger, Thomas; Sadowski, Gabriele

2009-03-01

The priority programme "Intelligent Hydrogels" was established by the German Research Foundation (DFG) in 2006 in order to strengthen the hydrogel-related research in Germany. The programme is being coordinated by Gabriele Sadowski, Technische Universität Dortmund. The aim of this priority programme is to develop new methods for the synthesis and characterization of smart hydrogels and to develop new modelling strategies in order to a) prepare the hydrogels for special applications and/or b) to develop and extend their capabilities for any desired use. In this programme, 73 scientists (36 professors and 37 scientific assistants/PhD students) from all over Germany are involved, working in 23 projects.

Alginate-hydroxypropylcellulose hydrogel microbeads for alkaline phosphatase encapsulation.

PubMed

Karewicz, A; Zasada, K; Bielska, D; Douglas, T E L; Jansen, J A; Leeuwenburgh, S C G; Nowakowska, M

2014-01-01

There is a growing interest in using proteins as therapeutics agents. Unfortunately, they suffer from limited stability and bioavailability. We aimed to develop a new delivery system for proteins. ALP, a model protein, was successfully encapsulated in the physically cross-linked sodium alginate/hydroxypropylcellulose (ALG-HPC) hydrogel microparticles. The obtained objects had regular, spherical shape and a diameter of ∼4 µm, as confirmed by optical microscopy and SEM analysis. The properties of the obtained microbeads could be controlled by temperature and additional coating or crosslinking procedures. The slow, sustained release of ALP in its active form with no initial burst effect was observed for chitosan-coated microspheres at pH = 7.4 and 37 °C. Activity of ALP released from ALG/HPC microspheres was confirmed by the occurance of effectively induced mineralization. SEM and AFM images revealed formation of the interpenetrated three-dimensional network of mineral, originating from the microbeads' surfaces. FTIR and XRD analyses confirmed formation of hydroxyapatite.

Introduction to cell–hydrogel mechanosensing

PubMed Central

Ahearne, Mark

2014-01-01

The development of hydrogel-based biomaterials represents a promising approach to generating new strategies for tissue engineering and regenerative medicine. In order to develop more sophisticated cell-seeded hydrogel constructs, it is important to understand how cells mechanically interact with hydrogels. In this paper, we review the mechanisms by which cells remodel hydrogels, the influence that the hydrogel mechanical and structural properties have on cell behaviour and the role of mechanical stimulation in cell-seeded hydrogels. Cell-mediated remodelling of hydrogels is directed by several cellular processes, including adhesion, migration, contraction, degradation and extracellular matrix deposition. Variations in hydrogel stiffness, density, composition, orientation and viscoelastic characteristics all affect cell activity and phenotype. The application of mechanical force on cells encapsulated in hydrogels can also instigate changes in cell behaviour. By improving our understanding of cell–material mechano-interactions in hydrogels, this should enable a new generation of regenerative medical therapies to be developed. PMID:24748951

Characterisations of collagen-silver-hydroxyapatite nanocomposites

NASA Astrophysics Data System (ADS)

Ciobanu, C. S.; Popa, C. L.; Petre, C. C.; Jiga, G.; Trusca, R.; Predoi, D.

2016-05-01

The XRD analysis were performed to confirm the formation of hydroxyapatite structure in collagen-silver-hydroxyapatite nanocomposites. The molecular interaction in collagen-hydroxyapatite nanocomposites was highlighted by Fourier transform infrared spectroscopy (FTIR) analysis. The SEM showed a nanostructure of collagen-silverhydroxyapatite nanocomposites composed of nano needle-like particles in a veil with collagen texture. The presence of vibrational groups characteristics to the hydroxyapatite structure in collagen-silver-hydroxyapatite (AgHApColl) nanocomposites was investigated by FTIR.

Clinical, histologic and histomorphometric evaluation of socket preservation using a synthetic nanocrystalline hydroxyapatite in comparison with a bovine xenograft: a randomized clinical trial.

PubMed

Gholami, Gholam Ali; Najafi, Babak; Mashhadiabbas, Fatemeh; Goetz, Werner; Najafi, Siamak

2012-10-01

The aim of this study was to compare a nanocrystalline hydroxyapatite (NCHA), NanoBone(®) and a deproteinized bovine bone mineral (DBBM), Bio-Oss(®) with a collagen membrane on the horizontal ridge width alterations following tooth extraction, in addition to histologic aspects of the grafted extraction sockets. In this randomized clinical trial, 28 symmetrical, non-molar, extraction sockets using a split-mouth design in 12 patients (eight women and four men; aged 21-60; mean 44.6 ± 11.4 years), were randomly selected in the first group to be grafted with DBBM granules covered with a collagen membrane and in the other group grafted with NCHA covered with a collagen membrane. Following extraction horizontal ridge width was measured using caliper and was blindly compared to the dimensions measured prior to implant placement, at the 6- to 8-month follow-up. Subsequently, a 2 × 6 mm trephine core was obtained with aid of acrylic stent and routine histologic preparation was performed on the specimens. The width of the DBBM group decreased from 7.75 ± 1.55 to 6.68 ± 1.85 mm (P < 0.05), whereas the width of the NCHA group decreased from 7.36 ± 1.94 to 6.43 ± 2.08 mm (P < 0.05). The mean between-group difference did not reach statistical significance (P = 0.62). Furthermore, histologic and histomorphometric analyses revealed 28.63 ± 12.53% vital bone in NCHA group vs. 27.35 ± 12.39% in DBBM group, and no statistically significant difference between the groups (P = 0.68). Socket preservation using either NCHA or DBBM in combination with collagen membrane, results in similar, limited horizontal ridge width alterations following tooth extraction. © 2011 John Wiley & Sons A/S.

Hydrogel microparticles for biosensing

PubMed Central

Le Goff, Gaelle C.; Srinivas, Rathi L.; Hill, W. Adam; Doyle, Patrick S.

2015-01-01

Due to their hydrophilic, biocompatible, and highly tunable nature, hydrogel materials have attracted strong interest in the recent years for numerous biotechnological applications. In particular, their solution-like environment and non-fouling nature in complex biological samples render hydrogels as ideal substrates for biosensing applications. Hydrogel coatings, and later, gel dot surface microarrays, were successfully used in sensitive nucleic acid assays and immunoassays. More recently, new microfabrication techniques for synthesizing encoded particles from hydrogel materials have enabled the development of hydrogel-based suspension arrays. Lithography processes and droplet-based microfluidic techniques enable generation of libraries of particles with unique spectral or graphical codes, for multiplexed sensing in biological samples. In this review, we discuss the key questions arising when designing hydrogel particles dedicated to biosensing. How can the hydrogel material be engineered in order to tune its properties and immobilize bioprobes inside? What are the strategies to fabricate and encode gel particles, and how can particles be processed and decoded after the assay? Finally, we review the bioassays reported so far in the literature that have used hydrogel particle arrays and give an outlook of further developments of the field. PMID:26594056

Solid state consolidation nanocrystalline copper-tungsten using cold spray

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

Hall, Aaron Christopher; Sarobol, Pylin; Argibay, Nicolas

It is well known that nanostructured metals can exhibit significantly improved properties compared to metals with conventional grain size. Unfortunately, nanocrystalline metals typically are not thermodynamically stable and exhibit rapid grain growth at moderate temperatures. This severely limits their processing and use, making them impractical for most engineering applications. Recent work has shown that a number of thermodynamically stable nanocrystalline metal alloys exist. These alloys have been prepared as powders using severe plastic deformation (e.g. ball milling) processes. Consolidation of these powders without compromise of their nanocrystalline microstructure is a critical step to enabling their use as engineering materials. Wemore » demonstrate solid-state consolidation of ball milled copper-tantalum nanocrystalline metal powder using cold spray. Unfortunately, the nanocrystalline copper-tantalum powder that was consolidated did not contain the thermodynamically stable copper-tantalum nanostructure. Nevertheless, this does this demonstrates a pathway to preparation of bulk thermodynamically stable nanocrystalline copper-tantalum. Furthermore, it demonstrates a pathway to additive manufacturing (3D printing) of nanocrystalline copper-tantalum. Additive manufacturing of thermodynamically stable nanocrystalline metals is attractive because it enables maximum flexibility and efficiency in the use of these unique materials.« less

Microwave-induced biomimetic approach for hydroxyapatite coatings of chitosan scaffolds.

PubMed

Kaynak Bayrak, Gökçe; Demirtaş, T Tolga; Gümüşderelioğlu, Menemşe

2017-02-10

Simulated body fluid (SBF) can form calcium phosphates on osteoinductive materials, so it is widely used for coating of bone scaffolds to mimic natural extracellular matrix (ECM). However, difficulties of bulk coating in 3D scaffolds and the necessity of long process times are the common problems for coating with SBF. In the present study, a microwave-assisted process was developed for rapid and internal coating of chitosan scaffolds. The scaffolds were fabricated as superporous hydrogel (SPH) by combining microwave irradiation and gas foaming methods. Then, they were immersed into 10x  SBF-like solution and homogenous bone-like hydroxyapatite (HA) coating was achieved by microwave treatment at 600W without the need of any nucleating agent. Cell culture studies with MC3T3-E1 preosteoblasts showed that microwave-assisted biomimetic HA coating process could be evaluated as an efficient and rapid method to obtain composite scaffolds for bone tissue engineering. Copyright © 2016 Elsevier Ltd. All rights reserved.

Rapid self-healing hydrogels

PubMed Central

Phadke, Ameya; Zhang, Chao; Arman, Bedri; Hsu, Cheng-Chih; Mashelkar, Raghunath A.; Lele, Ashish K.; Tauber, Michael J.; Arya, Gaurav; Varghese, Shyni

2012-01-01

Synthetic materials that are capable of autonomous healing upon damage are being developed at a rapid pace because of their many potential applications. Despite these advancements, achieving self-healing in permanently cross-linked hydrogels has remained elusive because of the presence of water and irreversible cross-links. Here, we demonstrate that permanently cross-linked hydrogels can be engineered to exhibit self-healing in an aqueous environment. We achieve this feature by arming the hydrogel network with flexible-pendant side chains carrying an optimal balance of hydrophilic and hydrophobic moieties that allows the side chains to mediate hydrogen bonds across the hydrogel interfaces with minimal steric hindrance and hydrophobic collapse. The self-healing reported here is rapid, occurring within seconds of the insertion of a crack into the hydrogel or juxtaposition of two separate hydrogel pieces. The healing is reversible and can be switched on and off via changes in pH, allowing external control over the healing process. Moreover, the hydrogels can sustain multiple cycles of healing and separation without compromising their mechanical properties and healing kinetics. Beyond revealing how secondary interactions could be harnessed to introduce new functions to chemically cross-linked polymeric systems, we also demonstrate various potential applications of such easy-to-synthesize, smart, self-healing hydrogels. PMID:22392977

Microfluidic hydrogels for tissue engineering.

PubMed

Huang, Guo You; Zhou, Li Hong; Zhang, Qian Cheng; Chen, Yong Mei; Sun, Wei; Xu, Feng; Lu, Tian Jian

2011-03-01

With advanced properties similar to the native extracellular matrix, hydrogels have found widespread applications in tissue engineering. Hydrogel-based cellular constructs have been successfully developed to engineer different tissues such as skin, cartilage and bladder. Whilst significant advances have been made, it is still challenging to fabricate large and complex functional tissues due mainly to the limited diffusion capability of hydrogels. The integration of microfluidic networks and hydrogels can greatly enhance mass transport in hydrogels and spatiotemporally control the chemical microenvironment of cells, mimicking the function of native microvessels. In this review, we present and discuss recent advances in the fabrication of microfluidic hydrogels from the viewpoint of tissue engineering. Further development of new hydrogels and microengineering technologies will have a great impact on tissue engineering.

Micromechanics Modeling of Fracture in Nanocrystalline Metals

NASA Technical Reports Server (NTRS)

Glaessgen, E. H.; Piascik, R. S.; Raju, I. S.; Harris, C. E.

2002-01-01

Nanocrystalline metals have very high theoretical strength, but suffer from a lack of ductility and toughness. Therefore, it is critical to understand the mechanisms of deformation and fracture of these materials before their full potential can be achieved. Because classical fracture mechanics is based on the comparison of computed fracture parameters, such as stress intlmsity factors, to their empirically determined critical values, it does not adequately describe the fundamental physics of fracture required to predict the behavior of nanocrystalline metals. Thus, micromechanics-based techniques must be considered to quanti@ the physical processes of deformation and fracture within nanocrystalline metals. This paper discusses hndamental physicsbased modeling strategies that may be useful for the prediction Iof deformation, crack formation and crack growth within nanocrystalline metals.

Synthesis and Characterization of Hydroxyapatite/Fullerenol Nanocomposites.

PubMed

Djordjevic, Aleksandar; Ignjatovic, Nenad; Seke, Mariana; Jovic, Danica; Uskokovic, Dragan; Rakocevic, Zlatko

2015-02-01

Fullerenols are polyhydroxylated, water soluble derivatives of fullerene C60, with potential application in medicine as diagnostic agents, antioxidants or nano drug carriers. This paper describes synthesis and physical characterization of a new nanocomposite hydroxyapatite/fullerenol. Surface of the nanocomposite hydroxyapatite/fullerenol is inhomogeneous with the diameter of the particles in the range from 100 nm to 350 nm. The ζ potential of this nanocomposite is ten times lower when compared to hydroxyapatite. Surface phosphate groups of hydroxyapatite are prone to forming hydrogen bonds, when in close contact with hydroxyl groups, which could lead to formation of hydrogen bonds between hydroxyapatite and hydroxyl groups of fullerenol. The surface of hydroxyapatite particles (-2.5 mV) was modified by fullerenol particles, as confirmed by the obtained ζ potential value of the nanocomposite biomaterial hydroxyapatite/fullerenol (-25.0 mV). Keywords: Hydroxyapatite, Fullerenol, Nanocomposite, Surface Analysis.

[Thromboresistance of glucose-containing hydrogels].

PubMed

Valuev, I L; Valuev, L I; Vanchugova, L V; Obydennova, I V; Valueva, T A

2013-01-01

The thromboresistance of glucose-sensitive polymer hydrogels, modeling one of the functions of the pancreas, namely, the ability to secrete insulin in response to the introduction of glucose into the environment, has been studied. Hydrogels were synthesized by the copolymerization of hydroxyethyl methacrylate with N-acryloyl glucosamine in the presence of a cross-linking agent and subsequently treated with concanavalin A. Introduction of glucose residues into the hydrogel did not result in significant changes in either the number of trombocytes adhered to the hydrogel or the degree of denaturation of blood plasma proteins interacting with the hydrogel. Consequently, the biological activity of insulin did not change after release from the hydrogel. The use of glucose-sensitive hydrogels is supposed to contribute to the development of a novel strategy for the treatment of diabetes.

Hydrogel Biomaterials: A Smart Future?

PubMed Central

Kopeček, Jindřich

2007-01-01

Hydrogels were the first biomaterials developed for human use. The state-of-the-art and potential for the future are discussed. Recently, new designs have produced mechanically strong synthetic hydrogels. Protein based hydrogels and hybrid hydrogels containing protein domains present a novel advance; such biomaterials may self-assemble from block or graft copolymers containing biorecognition domains. One of the domains, the coiled-coil, ubiquitously found in nature, has been used as an example to demonstrate the developments in the design of smart hydrogels. The application potential of synthetic, protein-based, DNA-based, and hybrid hydrogels bodes well for the future of this class of biomaterials. PMID:17697712

Photonic hydrogel sensors.

PubMed

Yetisen, Ali K; Butt, Haider; Volpatti, Lisa R; Pavlichenko, Ida; Humar, Matjaž; Kwok, Sheldon J J; Koo, Heebeom; Kim, Ki Su; Naydenova, Izabela; Khademhosseini, Ali; Hahn, Sei Kwang; Yun, Seok Hyun

2016-01-01

Analyte-sensitive hydrogels that incorporate optical structures have emerged as sensing platforms for point-of-care diagnostics. The optical properties of the hydrogel sensors can be rationally designed and fabricated through self-assembly, microfabrication or laser writing. The advantages of photonic hydrogel sensors over conventional assay formats include label-free, quantitative, reusable, and continuous measurement capability that can be integrated with equipment-free text or image display. This Review explains the operation principles of photonic hydrogel sensors, presents syntheses of stimuli-responsive polymers, and provides an overview of qualitative and quantitative readout technologies. Applications in clinical samples are discussed, and potential future directions are identified. Copyright © 2015 Elsevier Inc. All rights reserved.

Enabling Surgical Placement of Hydrogels through Achieving Paste-Like Rheological Behavior in Hydrogel Precursor Solutions

PubMed Central

Beck, Emily C.; Lohman, Brooke L.; Tabakh, Daniel B.; Kieweg, Sarah L.; Gehrke, Stevin H.; Berkland, Cory J.; Detamore, Michael S.

2015-01-01

Hydrogels are a promising class of materials for tissue regeneration, but they lack the ability to be molded into a defect site by a surgeon because hydrogel precursors are liquid solutions that are prone to leaking during placement. Therefore, although the main focus of hydrogel technology and developments are on hydrogels in their crosslinked form, our primary focus is on improving the fluid behavior of hydrogel precursor solutions. In this work, we introduce a method to achieve paste-like hydrogel precursor solutions by combining hyaluronic acid nanoparticles with traditional crosslinked hyaluronic acid hydrogels. Prior to crosslinking, the samples underwent rheological testing to assess yield stress and recovery using linear hyaluronic acid as a control. The experimental groups containing nanoparticles were the only solutions that exhibited a yield stress, demonstrating that the nanoparticulate rather than the linear form of hyaluronic acid was necessary to achieve paste-like behavior. The gels were also photocrosslinked and further characterized as solids, where it was demonstrated that the inclusion of nanoparticles did not adversely affect the compressive modulus and that encapsulated bone marrow-derived mesenchymal stem cells remained viable. Overall, this nanoparticle-based approach provides a platform hydrogel system that exhibits a yield stress prior to crosslinking, and can then be crosslinked into a hydrogel that is capable of encapsulating cells that remain viable. This behavior may hold significant impact for hydrogel applications where a paste-like behavior is desired in the hydrogel precursor solution. PMID:25691398

Biodegradation and cytotoxicity of ciprofloxacin-loaded hydroxyapatite-polycaprolactone nanocomposite film for sustainable bone implants.

PubMed

Nithya, Rajendran; Meenakshi Sundaram, Nachiappan

2015-01-01

In recent years there has been a steep increase in the number of orthopedic patients for many reasons. One major reason is osteomyelitis, caused by pyrogenic bacteria, with progressive infection of the bone or bone marrow and surrounding tissues. So antibiotics must be introduced during bone implantation to avoid prolonged infection. The objective of the study reported here was to prepare a composite film of nanocrystalline hydroxyapatite (HAp) and polycaprolactone (PCL) polymer loaded with ciprofloxacin, a frequently used antibiotic agent for bone infections. Nanocrystalline HAp was synthesized by precipitation method using the precursor obtained from eggshell. The nanocomposite film (HAp-PCL-ciprofloxacin) was prepared by solvent evaporation. Drug-release and biodegradation studies were undertaken by immersing the composite film in phosphate-buffered saline solution, while a cytotoxicity test was performed using the fibroblast cell line NIH-3T3 and osteoblast cell line MG-63. The pure PCL film had quite a low dissolution rate after an initial sharp weight loss, whereas the ciprofloxacin-loaded HAp-PCL nanocomposite film had a large weight loss due to its fast drug release. The composite film had higher water absorption than the pure PCL, and increasing the concentration of the HAp increased the water absorption. The in vitro cell-line study showed a good biocompatibility and bioactivity of the developed nanocomposite film. The prepared film will act as a sustainable bone implant in addition to controlled drug delivery.

Biomimetic Hydrogel Materials

DOEpatents

Bertozzi, Carolyn , Mukkamala, Ravindranath , Chen, Oing , Hu, Hopin , Baude, Dominique

2003-04-22

Novel biomimetic hydrogel materials and methods for their preparation. Hydrogels containing acrylamide-functionalized carbohydrate, sulfoxide, sulfide or sulfone copolymerized with a hydrophilic or hydrophobic copolymerizing material selected from the group consisting of an acrylamide, methacrylamide, acrylate, methacrylate, vinyl and a derivative thereof present in concentration from about 1 to about 99 wt %. and methods for their preparation. The method of use of the new hydrogels for fabrication of soft contact lenses and biomedical implants.

Biomimetic hydrogel materials

DOEpatents

Bertozzi, Carolyn; Mukkamala, Ravindranath; Chen, Qing; Hu, Hopin; Baude, Dominique

2000-01-01

Novel biomimetic hydrogel materials and methods for their preparation. Hydrogels containing acrylamide-functionalized carbohydrate, sulfoxide, sulfide or sulfone copolymerized with a hydrophilic or hydrophobic copolymerizing material selected from the group consisting of an acrylamide, methacrylamide, acrylate, methacrylate, vinyl and a derivative thereof present in concentration from about 1 to about 99 wt %. and methods for their preparation. The method of use of the new hydrogels for fabrication of soft contact lenses and biomedical implants.

Synthesis, characterization, and photocatalytic properties of nanocrystalline NZO thin films

NASA Astrophysics Data System (ADS)

Aryanto, D.; Hastuti, E.; Husniya, N.; Sudiro, T.; Nuryadin, B. W.

2018-03-01

Nanocrystalline Ni-doped ZnO (NZO) thin films were synthesized on glass substrate using sol-gel spin coating methods. The effect of annealing on the structural and optical properties of nanocrystalline thin film was studied using X-ray diffractometer (XRD), field emission scanning electron microscopy (FESEM), UV-VIS spectrophotometry, and photoluminescence (PL). The results showed that the annealing temperature strongly influenced the physical properties of nanocrystalline NZO thin films. The photocatalytic properties of nanocrystalline NZO thin films were evaluated using an aqueous solution of Rhodamine-B. The photocatalytic activity of nanocrystalline NZO thin films increased with the increase of annealing temperature. The results indicated that the structure, morphology, and band gap energy of nanocrystalline NZO thin films played an important role in photocatalytic activity.

[Cytocompatibility of nanophase hydroxyapatite ceramics].

PubMed

Wen, Bo; Chen, Zhi-qing; Jiang, Yin-shan; Yang, Zheng-wen; Xu, Yong-zhong

2004-12-01

To evaluate the cytocompatibility of nanophase hydroxyapatite ceramics in vitro. Hydroxyapatite (HA) was prepared via wet method. The grain size of the hydroxyapatite in the study was determined by scanning electron microscope and atomic force microscope with image analysis software. Primary osteoblast culture was established from rat calvaria. Cell adherence and proliferation on nanophase hydroxyapatite ceramics and conventional hydroxyapatite ceramics were examined at 1, 3, 5, 7 days. Morphology of the cells was observed by microscope. The average grain size of the nanophase and conventional HA was 55 nm and 780 nm, respectively. Throughout 7 days period, osteoblast proliferation on the HA was similar to that on tissue culture borosilicate glass controls, osteoblasts could attach, spread and proliferate on HA. However, compared to conventional ceramics, osteoblast proliferation on nanophase HA was significantly better after 1, 3, 5 and 7 days. Cytocompatibility of nanophase HA was significantly better than conventional ceramics.

Enhanced osteoconductivity of sodium-substituted hydroxyapatite by system instability.

PubMed

Sang Cho, Jung; Um, Seung-Hoon; Su Yoo, Dong; Chung, Yong-Chae; Hye Chung, Shin; Lee, Jeong-Cheol; Rhee, Sang-Hoon

2014-07-01

The effect of substituting sodium for calcium on enhanced osteoconductivity of hydroxyapatite was newly investigated. Sodium-substituted hydroxyapatite was synthesized by reacting calcium hydroxide and phosphoric acid with sodium nitrate followed by sintering. As a control, pure hydroxyapatite was prepared under identical conditions, but without the addition of sodium nitrate. Substitution of calcium with sodium in hydroxyapatite produced the structural vacancies for carbonate ion from phosphate site and hydrogen ion from hydroxide site of hydroxyapatite after sintering. The total system energy of sodium-substituted hydroxyapatite with structural defects calculated by ab initio methods based on quantum mechanics was much higher than that of hydroxyapatite, suggesting that the sodium-substituted hydroxyapatite was energetically less stable compared with hydroxyapatite. Indeed, sodium-substituted hydroxyapatite exhibited higher dissolution behavior of constituent elements of hydroxyapatite in simulated body fluid (SBF) and Tris-buffered deionized water compared with hydroxyapatite, which directly affected low-crystalline hydroxyl-carbonate apatite forming capacity by increasing the degree of apatite supersaturation in SBF. Actually, sodium-substituted hydroxyapatite exhibited markedly improved low-crystalline hydroxyl-carbonate apatite forming capacity in SBF and noticeably higher osteoconductivity 4 weeks after implantation in calvarial defects of New Zealand white rabbits compared with hydroxyapatite. In addition, there were no statistically significant differences between hydroxyapatite and sodium-substituted hydroxyapatite on cytotoxicity as determined by BCA assay. Taken together, these results indicate that sodium-substituted hydroxyapatite with structural defects has promising potential for use as a bone grafting material due to its enhanced osteoconductivity compared with hydroxyapatite. © 2013 Wiley Periodicals, Inc.

Bioadhesive hydrogels for cosmetic applications.

PubMed

Parente, M E; Ochoa Andrade, A; Ares, G; Russo, F; Jiménez-Kairuz, Á

2015-10-01

The use of bioadhesive hydrogels for skin care presents important advantages such as long residence times on the application site and reduced product administration frequency. The aim of the present work was to develop bioadhesive hydrogels for skin application, using caffeine as a model active ingredient. Eight hydrogels were formulated using binary combinations of a primary polymer (carbomer homopolymer type C (Carbopol(®) 980) or kappa carrageenan potassium salt (Gelcarin(®) GP-812 NF)) and a secondary polymer (carbomer copolymer type B (Pemulen(™) TR-1), xanthan gum or guar gum). Hydrogels were characterized by means of physico-chemical (dynamic rheological measurements, spreadability and adhesion measurements) and sensory methods (projective mapping in combination with a check-all-that-apply (CATA) question). Caffeine hydrogels were formulated using two of the most promising formulations regarding adhesion properties and sensory characteristics. In vitro active ingredient release studies were carried out. Hydrogel formulations showed a prevalently elastic rheological behaviour. Complex viscosity of carbomer homopolymer type C hydrogels was higher than that of the kappa carrageenan hydrogels. Besides, complex viscosity values were dependent on the secondary polymer present in the formulation. Significant differences among hydrogels were found in detachment force, work of adhesion and spreading diameter results. Association of projective mapping with CATA allowed to determine similarities and dissimilarities among samples. Cluster analysis associated the samples in two groups. Two hydrogels were selected to study the release of caffeine. Both hydrogels presented similar release profiles which were well described by the Higuchi model. Caffeine release was exclusively controlled by a diffusive process. Physico-chemical and sensory techniques enabled the identification of bioadhesive hydrogel formulations with positive characteristics for cosmetic applications

Method of making nanocrystalline alpha alumina

DOEpatents

Siegel, Richard W.; Hahn, Horst; Eastman, Jeffrey A.

1992-01-01

Method of making selected phases of nanocrystalline ceramic materials. Various methods of controlling the production of nanocrystalline alpha alumina and titanium oxygen phases are described. Control of the gas atmosphere and use of particular oxidation treatments give rise to the ability to control the particular phases provided in the aluminum/oxygen and titanium/oxygen system.

A preliminary study in osteoinduction by a nano-crystalline hydroxyapatite in the mini pig.

PubMed

Götz, Werner; Lenz, Solvig; Reichert, Christoph; Henkel, Kai-Olaf; Bienengräber, Volker; Pernicka, Laura; Gundlach, Karsten K H; Gredes, Tomasz; Gerber, Thomas; Gedrange, Tomasz; Heinemann, Friedhelm

2010-12-01

To test the probable osteoinductive properties of NanoBone, a new highly non-sintered porous nano-crystalline hydroxylapatite bone substitute embedded into a silica gel matrix, granules were implanted subcutaneously and intramuscularly into the back region of 18 mini pigs. After periods of 5 and 10 weeks as well as 4 and 8 months, implantation sites were investigated using histological and histomorphometric procedures. Signs of early osteogenesis could already be detected after 5 weeks. The later periods were characterized by increasing membranous osteogenesis in and around the granules leading to the formation of bone-like structures showing periosteal and tendon-like structures with bone marrow and focal chondrogenesis. Bone formation was better in the subcutaneous than in the intramuscular implantation sites. This ectopic osteogenesis is discussed with regard to the nanoporosity and microporosity of the material, physico-chemical interactions at its surface, the differentiation of osteoblasts, the role of angiogenesis and the probable involvement of growth factors. The results of this preliminary study indicate that this biomaterial has osteoinductive potential and induces the formation of bone structures, mainly in subcutaneous adipose tissue in the pig.

Chitin-natural clay nanotubes hybrid hydrogel.

PubMed

Liu, Mingxian; Zhang, Yun; Li, Jingjing; Zhou, Changren

2013-07-01

Novel hybrid hydrogel was synthesized from chitin NaOH/urea aqueous solution in presence of halloysite nanotubes (HNTs) via crosslinking with epichlorohydrin. Fourier transform infrared (FT-IR) spectra and atomic force microscopy (AFM) results confirmed the interfacial interactions in the chitin-HNTs hybrid hydrogel. The compressive strength and shear modulus of chitin hydrogel were significantly increased by HNTs as shown in the static compressive experiment and rheology measurement. The hybrid hydrogels showed highly porous microstructures by scanning electron microscopy (SEM). The swelling ratio of chitin hydrogel decreased because of the addition of HNTs. The malachite green's absorption experiment result showed that the hybrid hydrogel exhibited much higher absorption rate than the pure chitin hydrogel. The prepared hybrid hydrogel had potential applications in waste treatment and biomedical areas. Copyright © 2013 Elsevier B.V. All rights reserved.

Facile and controllable synthesis of hydroxyapatite/graphene hybrid materials with enhanced sensing performance towards ammonia.

PubMed

Zhang, Qing; Liu, Yong; Zhang, Ying; Li, Huixia; Tan, Yanni; Luo, Lanlan; Duan, Junhao; Li, Kaiyang; Banks, Craig E

2015-08-07

In this work, needle-like and micro-spherical agglomerates of nanocrystalline hydroxyapatite (HA) were successfully assembled on the surface of graphene sheets with the aid of dopamine having two roles, as a template and a reductant for graphite oxide during the process of self-polymerization. The crystalline structure and micromorphology of HA can be conveniently regulated by controlling the mineralization route either with a precipitation (cHA/GR) or biomimetic methodology (bHA/GR). Both the composites exhibit improvements of ∼150% and ∼250% in sensitivity towards the sensing of ammonia at room temperature, compared with that of bare graphene. The combination of the multi-adsorption capability of HA and the electric conductivity of graphene is proposed to be the major reason for the observed enhancements. Gas sensing tests demonstrated that the HA/GR composites exhibit excellent selectivity, high sensitivity and repeatable stability towards the analytical sensing of ammonia.

The Bulk Nanocrystalline zn Produced by Mechanical Attrition

NASA Astrophysics Data System (ADS)

Zhu, X. K.; Zhao, K. Y.; Li, C. J.; Tao, J. M.; Chan, T. L.; Koch, C. C.

The purpose of experiment was to produce bulk nanocrystalline Zn by mechanical attrition. The bulk nanocrystalline Zn produced by mechanical attrition was studied. The microstructural evolution during cryomilling and subsequent room temperature milling was characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). In this paper, Nanocrystalline Zn was produced by insitu consolidation of Zn elemental powder using mechanical attrition at liquid nitrogen and room temperature. For the samples studied, the longest elongation of 65% and highest stress of 200 MPa is obtained in nanocrystalline Zn during tensile testing at the condition of strain rate (10-3 sec-1) and 20°C which is equal to 0.43 Tm (Tm is the melting temperature of pure Zn).

Novel injectable gellan gum hydrogel composites incorporating Zn- and Sr-enriched bioactive glass microparticles: High-resolution X-ray microcomputed tomography, antibacterial and in vitro testing.

PubMed

Douglas, Timothy E L; Dziadek, Michal; Gorodzha, Svetlana; Lišková, Jana; Brackman, Gilles; Vanhoorne, Valérie; Vervaet, Chris; Balcaen, Lieve; Del Rosario Florez Garcia, Maria; Boccaccini, Aldo R; Weinhardt, Venera; Baumbach, Tilo; Vanhaecke, Frank; Coenye, Tom; Bačáková, Lucie; Surmeneva, Maria A; Surmenev, Roman A; Cholewa-Kowalska, Katarzyna; Skirtach, Andre G

2018-06-01

Mineralization of hydrogel biomaterials is desirable to improve their suitability as materials for bone regeneration. In this study, gellan gum (GG) hydrogels were formed by simple mixing of GG solution with bioactive glass microparticles of 45S5 composition, leading to hydrogel formation by ion release from the amorphous bioactive glass microparticles. This resulted in novel injectable, self-gelling composites of GG hydrogels containing 20% bioactive glass. Gelation occurred within 20 min. Composites containing the standard 45S5 bioactive glass preparation were markedly less stiff. X-ray microcomputed tomography proved to be a highly sensitive technique capable of detecting microparticles of diameter approximately 8 μm, that is, individual microparticles, and accurately visualizing the size distribution of bioactive glass microparticles and their aggregates, and their distribution in GG hydrogels. The widely used melt-derived 45S5 preparation served as a standard and was compared with a calcium-rich, sol-gel derived preparation (A2), as well as A2 enriched with zinc (A2Zn5) and strontium (A2Sr5). A2, A2Zn, and A2Sr bioactive glass particles were more homogeneously dispersed in GG hydrogels than 45S5. Composites containing all four bioactive glass preparations exhibited antibacterial activity against methicillin-resistant Staphylococcus aureus. Composites containing A2Zn5 and A2Sr5 bioactive glasses supported the adhesion and growth of osteoblast-like cells and were considerably more cytocompatible than 45S5. All composites underwent mineralization with calcium-deficient hydroxyapatite upon incubation in simulated body fluid. The extent of mineralization appeared to be greatest for composites containing A2Zn5 and 45S5. The results underline the importance of the choice of bioactive glass when preparing injectable, self-gelling composites. Copyright © 2018 John Wiley & Sons, Ltd.

The Formation Mechanism of Hydrogels.

PubMed

Lu, Liyan; Yuan, Shiliang; Wang, Jing; Shen, Yun; Deng, Shuwen; Xie, Luyang; Yang, Qixiang

2017-06-12

Hydrogels are degradable polymeric networks, in which cross-links play a vital role in structure formation and degradation. Cross-linking is a stabilization process in polymer chemistry that leads to the multi-dimensional extension of polymeric chains, resulting in network structures. By cross-linking, hydrogels are formed into stable structures that differ from their raw materials. Generally, hydrogels can be prepared from either synthetic or natural polymers. Based on the types of cross-link junctions, hydrogels can be categorized into two groups: the chemically cross-linked and the physically cross-linked. Chemically cross-linked gels have permanent junctions, in which covalent bonds are present between different polymer chains, thus leading to excellent mechanical strength. Although chemical cross-linking is a highly resourceful method for the formation of hydrogels, the cross-linkers used in hydrogel preparation should be extracted from the hydrogels before use, due to their reported toxicity, while, in physically cross-linked gels, dissolution is prevented by physical interactions, such as ionic interactions, hydrogen bonds or hydrophobic interactions. Physically cross-linked methods for the preparation of hydrogels are the alternate solution for cross-linker toxicity. Both methods will be discussed in this essay. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Hydroxyapatite synthesis using EDTA

PubMed Central

Kang, Nak Heon; Kim, Soon Je; Song, Seung Han; Choi, Sang mun; Choi, Sik Young; Kim, Youn Jung

2013-01-01

Bone comprises structure of body and is consisted of inorganic substances. It exists in an organic structure in the body. Even though it is firm and has self healing mechanism, it can be damaged by trauma, cancer, or bone diseases. Allograft can be an alternative solution for autologous bone graft. Hydroxyapatite(Ca10(PO4)6(OH)2), an excellent candidate for allograft, can be applied to bone defect area. There are several methods to produce hydroxyapatite, however economical cost and time consuming make the production difficult. In this study we synthesized the hydroxyapatite with Ethyenediamine tetraacetic acid. Freeze Dried Bone Allograft(Hans Biomed) was used to be a control group. Synthesized hydroxyapatite was a rod shape, white powdery type substance with 2 ~ 5 μm length and 0.5 ~ 1 μm width. X-ray diffraction showed the highest sharp peak at 32° and high peaks at 25.8°, 39.8°, 46.8°, 49.5°, and 64.0° indicating a similar substance to the freeze Dried Bone Allograft. 3 days after the cell growth of synthesized hydroxyapatite showed 1.5 fold more than the Bone Allograft. Cellular and media alkaline phosphate activity increased similar to the bone alloagraft. In this study we came up with a new method to produce the hydroxyapatite. It is a convenient method that can be held in room temperature and low pressure. Also the the product can be manufactured in large quantity. It can be also transformed into scaffold structure which will perform a stronger configuration. The manufacturing method will help the bony defect patients and make future medical products. PMID:23714942

Hydroxyapatite synthesis using EDTA.

PubMed

Kang, Nak Heon; Kim, Soon Je; Song, Seung Han; Choi, Sang mun; Choi, Sik Young; Kim, Youn Jung

2013-05-01

Bone comprises structure of the body and consisted of inorganic substances. It exists in an organic structure in the body. Even though it is firm and has self-healing mechanism, it can be damaged by trauma, cancer, or bone diseases. Allograft can be an alternative solution for autologous bone graft. Hydroxyapatite (Ca10(PO4)6(OH)2), an excellent candidate for allograft, can be applied to bone defect area. There are several methods to produce hydroxyapatite; however, economical cost and being time consuming make the production difficult. In this study, we synthesized hydroxyapatite with EDTA. Freeze-dried bone allograft (Hans Biomed) was used as the control group. Synthesized hydroxyapatite was a rod-shaped, white powdery substance with 2- to 5-μm length and 0.5- to 1-μm width. X-ray diffraction showed the highest sharp peak at 32°C and high peaks at 25.8°C, 39.8°C, 46.8°C, 49.5°C, and 64.0°C, indicating a similar substance to the freeze-dried bone allograft. After 3 days, the cell growth of synthesized hydroxyapatite showed 1.5-fold more than did the bone allograft. Cellular and media alkaline phosphate activity increased similar to the bone allograft. In this study, we came up with a new method to produce the hydroxyapatite. It is a convenient method that can be held in room temperature and low pressure. Also, the product can be manufactured in large quantity. It can be also transformed into scaffold structure, which will perform a stronger configuration. The manufacturing method will help the bony defect patients and make future medical products.

Distributed vasculogenesis from modular agarose-hydroxyapatite-fibrinogen microbeads.

PubMed

Rioja, Ana Y; Daley, Ethan L H; Habif, Julia C; Putnam, Andrew J; Stegemann, Jan P

2017-06-01

Critical limb ischemia impairs circulation to the extremities, causing pain, disrupted wound healing, and potential tissue necrosis. Therapeutic angiogenesis seeks to repair the damaged microvasculature directly to restore blood flow. In this study, we developed modular, micro-scale constructs designed to possess robust handling qualities, allow in vitro pre-culture, and promote microvasculature formation. The microbead matrix consisted of an agarose (AG) base to prevent aggregation, combined with cell-adhesive components of fibrinogen (FGN) and/or hydroxyapatite (HA). Microbeads encapsulating a co-culture of human umbilical vein endothelial cells (HUVEC) and fibroblasts were prepared and characterized. Microbeads were generally 80-100µm in diameter, and the size increased with the addition of FGN and HA. Addition of HA increased the yield of microbeads, as well as the homogeneity of distribution of FGN within the matrix. Cell viability was high in all microbead types. When cell-seeded microbeads were embedded in fibrin hydrogels, HUVEC sprouting and inosculation between neighboring microbeads were observed over seven days. Pre-culture of microbeads for an additional seven days prior to embedding in fibrin resulted in significantly greater HUVEC network length in AG+HA+FGN microbeads, as compared to AG, AG+HA or AG+FGN microbeads. Importantly, composite microbeads resulted in more even and widespread endothelial network formation, relative to control microbeads consisting of pure fibrin. These results demonstrate that AG+HA+FGN microbeads support HUVEC sprouting both within and between adjacent microbeads, and can promote distributed vascularization of an external matrix. Such modular microtissues may have utility in treating ischemic tissue by rapidly re-establishing a microvascular network. Critical limb ischemia (CLI) is a chronic disease that can lead to tissue necrosis, amputation, and death. Cell-based therapies are being explored to restore blood flow and

The influence of Ca/P ratio on the properties of hydroxyapatite bioceramics

NASA Astrophysics Data System (ADS)

Ramesh, S.; Tan, C. Y.; Hamdi, M.; Sopyan, I.; Teng, W. D.

2007-07-01

The paper reports on the effect of Ca/P ratio (1.57, 1.67 and 1.87) on the densification behaviour of nanocrystalline hydroxyapatite (HA) prepared by a chemical precipitation method. Green compacts were prepared and sintered at temperatures ranging from 1000°C to 1350°C. The sintered samples were characterized to determine the HA phase stability, bulk density, hardness, fracture toughness and Young's modulus. XRD analysis revealed that the phase stability was not disrupted throughout the sintering regime employed for HA having Ca/P ratio of 1.57 and 1.67. However, secondary phases were observed for HA having a Ca/P ratio of 1.87 when sintered at high temperatures. In general, regardless of Ca/P ratio, the HA bodies achieved > 95% relative density when sintered at 1100°C-1250°C. The results indicated that the stoichiometric HA (Ca/P ratio = 1.67) exhibited the overall best properties, with the highest hardness of 7.23 GPa and fracture toughness of 1.28 MPam1/2 being attained when sintered at 1000°C-1050°C.

Poly(n-vinylpyrrolidone) hydrogels: 2.Hydrogel composites as wound dressing for tropical environment

NASA Astrophysics Data System (ADS)

Himly, N.; Darwis, D.; Hardiningsih, L.

1993-10-01

POLY(N-VINYLPYRROLIDONE) HYDROGELS: 2. HYDROGEL COMPOSITES AS WOUND DRESSING FOR TROPICAL ENVIRONMENT. The effects of irradiation on hydration and other properties of poly(vinylpyrrolidone) (PVP) hydrogel composites have been investigated. The aqueous solution of vinylpyrrolidone (VP) 10 wt % was mixed with several additives such as agar and polyethylen glycol (PEG). The solution was then irradiated with gamma rays from Cobalt-60 source at room temperature. Several parameters such as elongation at break (EB), tensile strength (TS), degree of swelling (DS), water vapor transmission rate (WVTR), equilibrium water content (EWC), microbial growth and penetration test, and water activity (Aw) were analysed at room temperature of 29 ±2°C humidity of 80 ± 10%. Results show that elongation at break of hydrogel membranes with initial composition of VP with agar, VP with agar and PEG were 240 % and 250 % kGy, the equilibrium water content of membranes were 96 to 90%, whereas degree of swelling were 55 to 10. The WVTR of hydrogel membranes with initial composition of VP with agar and PEG was 70 g m -2h -1, while the water activity was 0.9. Such hydrogel membranes exhibits the following properties: They are elastic, transparent, flexible, impermeable for bacteria. They absopt a high capacity of water, attached to healthy skin but not to the wound and they are easy to remove. These properties of the hydrogel membranes allow for applying as a wound dressings in tropical environment.

Bacterial adhesion to conventional hydrogel and new silicone-hydrogel contact lens materials.

PubMed

Kodjikian, Laurent; Casoli-Bergeron, Emmanuelle; Malet, Florence; Janin-Manificat, Hélène; Freney, Jean; Burillon, Carole; Colin, Joseph; Steghens, Jean-Paul

2008-02-01

As bacterial adhesion to contact lenses may contribute to the pathogenesis of keratitis, the aim of our study was to investigate in vitro adhesion of clinically relevant bacteria to conventional hydrogel (standard HEMA) and silicone-hydrogel contact lenses using a bioluminescent ATP assay. Four types of unworn contact lenses (Etafilcon A, Galyfilcon A, Balafilcon A, Lotrafilcon B) were incubated with Staphylococcus epidermidis (two different strains) and Pseudomonas aeruginosa suspended in phosphate buffered saline (PBS). Lenses were placed with the posterior surface facing up and were incubated in the bacterial suspension for 4 hours at 37 degrees C. Bacterial binding was then measured and studied by bioluminescent ATP assay. Six replicate experiments were performed for each lens and strain. Adhesion of all species of bacteria to standard HEMA contact lenses (Etafilcon A) was found to be significantly lower than that of three types of silicone-hydrogel contact lenses, whereas Lotrafilcon B material showed the highest level of bacterial binding. Differences between species in the overall level of adhesion to the different types of contact lenses were observed. Adhesion of P. aeruginosa was typically at least 20 times greater than that observed with both S. epidermidis strains. Conventional hydrogel contact lenses exhibit significantly lower bacterial adhesion in vitro than silicone-hydrogel ones. This could be due to the greater hydrophobicity but also to the higher oxygen transmissibility of silicone-hydrogel lenses.

Tough photoluminescent hydrogels doped with lanthanide.

PubMed

Wang, Mei Xiang; Yang, Can Hui; Liu, Zhen Qi; Zhou, Jinxiong; Xu, Feng; Suo, Zhigang; Yang, Jian Hai; Chen, Yong Mei

2015-03-01

Photoluminescent hydrogels have emerged as novel soft materials with potential applications in many fields. Although many photoluminescent hydrogels have been fabricated, their scope of usage has been severely limited by their poor mechanical performance. Here, a facile strategy is reported for preparing lanthanide (Ln)-alginate/polyacrylamide (PAAm) hydrogels with both high toughness and photoluminescence, which has been achieved by doping Ln(3+) ions (Ln = Eu, Tb, Eu/Tb) into alginate/PAAm hydrogel networks, where Ln(3+) ions serve as both photoluminescent emitters and physical cross-linkers. The resulting hydrogels exhibit versatile advantages including excellent mechanical properties (∼ MPa strength, ≈ 20 tensile strains, ≈ 10(4) kJ m(-3) energy dissipation), good photoluminescent performance, tunable emission color, excellent processability, and cytocompatibility. The developed tough photoluminescent hydrogels hold great promises for expanding the usage scope of hydrogels. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Aging of Nanocrystalline Mackinawite (FeS): Mineralogical and Physicochemical Properties

NASA Astrophysics Data System (ADS)

Jeong, H. Y.; Lee, H.

2011-12-01

Due to the extraordinary physical properties and high surface areas, nanocrystalline minerals have been widely investigated for their potential uses in treating contaminated groundwaters and surface waters. Most previous studies in this field have focused on either preparation of nanocrystalline minerals or measurement of their reactivity with environmental contaminants. Nanocrystalline minerals, due to the inherent thermodynamic instability, tend to change the physicochemical and mineralogical properties over time, usually resulting in the decreased reactivity. Thus, to better assess the long-term effectiveness of nanocrystalline minerals in field applications, such "aging" effects should be clearly delineated. In the present work, we have investigated the aging impact on nanocrystalline mackinawite (FeS), the ubiquitous Fe-bearing mineral in anoxic sulfidic sediments. Mackinawite (FeS) is known to be an effective scavenger for metal pollutants and a strong reducing reagent for chromate and chlorinated organic compounds. Our preliminary results indicate that nanocrystalline FeS ages via Ostwald ripening, particle aggregation, or mineralogical transformation. By X-ray diffraction (XRD) analysis, aging of nanocrystalline FeS via Ostwald ripening is found to be dominant at acidic pH. Cryogenic transmission electron microscopy (TEM) shows that particle aggregation is most evident at neutral pH. Transformation of nanosized FeS into a more thermodynamically stable greigite (Fe3S4) is observed in the presence of folic acid at acidic pH. The pH-dependent aging process may be linked with changes in the apparent solubility and surface charge of FeS with pH. The Ostwald ripening or particle aggregation of nanocrystalline FeS leads to the decrease surface area, thus causing the decreased reactivity. Given the less reactivity of greigite, the transformation of nanocrystalline FeS to greigite is also expected to result in the decreased reactivity.

Gelatin- and starch-based hydrogels. Part B: In vitro mesenchymal stem cell behavior on the hydrogels.

PubMed

Van Nieuwenhove, Ine; Salamon, Achim; Adam, Stefanie; Dubruel, Peter; Van Vlierberghe, Sandra; Peters, Kirsten

2017-04-01

Tissue regeneration often occurs only to a limited extent. By providing a three-dimensional matrix serving as a surrogate extracellular matrix that promotes adult stem cell adhesion, proliferation and differentiation, scaffold-guided tissue regeneration aims at overcoming this limitation. In this study, we applied hydrogels made from crosslinkable gelatin, the hydrolyzed form of collagen, and functionalized starch which were characterized in depth and optimized as described in Van Nieuwenhove et al., 2016. "Gelatin- and Starch-Based Hydrogels. Part A: Hydrogel Development, Characterization and Coating", Carbohydrate Polymers 152:129-39. Collagen is the main structural protein in animal connective tissue and the most abundant protein in mammals. Starch is a carbohydrate consisting of a mixture of amylose and amylopectin. Hydrogels were developed with varying chemical composition (ratio of starch to gelatin applied) and different degrees of methacrylation of the applied gelatin phase. The hydrogels used exhibited no adverse effect on viability of the stem cells cultured on them. Moreover, initial cell adhesion did not differ significantly between them, while the strongest proliferation was observed on the hydrogel with the highest degree of cross-linking. On the least crosslinked and thus most flexible hydrogels, the highest degree of adipogenic differentiation was found, while osteogenic differentiation was the strongest on the most rigid, starch-blended hydrogels. Hydrogel coating with extracellular matrix compounds aggrecan or fibronectin prior to cell seeding exhibited no significant effects. Thus, gelatin-based hydrogels can be optimized regarding maximum promotion of either adipogenic or osteogenic stem cell differentiation in vitro, which makes them promising candidates for in vivo evaluation in clinical studies aiming at either soft or hard tissue regeneration. Copyright © 2017 Elsevier Ltd. All rights reserved.

Periodontal regeneration with stem cells-seeded collagen-hydroxyapatite scaffold.

PubMed

Liu, Zeping; Yin, Xing; Ye, Qingsong; He, Wulin; Ge, Mengke; Zhou, Xiaofu; Hu, Jing; Zou, Shujuan

2016-07-01

Re-establishing compromised periodontium to its original structure, properties and function is demanding, but also challenging, for successful orthodontic treatment. In this study, the periodontal regeneration capability of collagen-hydroxyapatite scaffolds, seeded with bone marrow stem cells, was investigated in a canine labial alveolar bone defect model. Bone marrow stem cells were isolated, expanded and characterized. Porous collagen-hydroxyapatite scaffold and cross-linked collagen-hydroxyapatite scaffold were prepared. Attachment, migration, proliferation and morphology of bone marrow stem cells, co-cultured with porous collagen-hydroxyapatite or cross-linked collagen-hydroxyapatite, were evaluated in vitro. The periodontal regeneration capability of collagen-hydroxyapatite scaffold with or without bone marrow stem cells was tested in six beagle dogs, with each dog carrying one sham-operated site as healthy control, and three labial alveolar bone defects untreated to allow natural healing, treated with bone marrow stem cells - collagen-hydroxyapatite scaffold implant or collagen-hydroxyapatite scaffold implant, respectively. Animals were euthanized at 3 and 6 months (3 animals per group) after implantation and the resected maxillary and mandibular segments were examined using micro-computed tomography scan, H&E staining, Masson's staining and histometric evaluation. Bone marrow stem cells were successfully isolated and demonstrated self-renewal and multi-potency in vitro. The porous collagen-hydroxyapatite and cross-linked collagen-hydroxyapatite had average pore sizes of 415 ± 20 µm and 203 ± 18 µm and porosity of 69 ± 0.5% and 50 ± 0.2%, respectively. The attachment, proliferation and migration of bone marrow stem cells were satisfactory on both porous collagen-hydroxyapatite and cross-linked collagen-hydroxyapatite scaffolds. Implantation of bone marrow stem cells - collagen-hydroxyapatite or collagen-hydroxyapatite scaffold in

Gelatin- and starch-based hydrogels. Part A: Hydrogel development, characterization and coating.

PubMed

Van Nieuwenhove, Ine; Salamon, Achim; Peters, Kirsten; Graulus, Geert-Jan; Martins, José C; Frankel, Daniel; Kersemans, Ken; De Vos, Filip; Van Vlierberghe, Sandra; Dubruel, Peter

2016-11-05

The present work aims at constructing the ideal scaffold matrix of which the physico-chemical properties can be altered according to the targeted tissue regeneration application. Ideally, this scaffold should resemble the natural extracellular matrix (ECM) as close as possible both in terms of chemical composition and mechanical properties. Therefore, hydrogel films were developed consisting of methacrylamide-modified gelatin and starch-pentenoate building blocks because the ECM can be considered as a crosslinked hydrogel network consisting of both polysaccharides and structural, signaling and cell-adhesive proteins. For the gelatin hydrogels, three different substitution degrees were evaluated including 31%, 72% and 95%. A substitution degree of 32% was applied for the starch-pentenoate building block. Pure gelatin hydrogels films as well as interpenetrating networks with gelatin and starch were developed. Subsequently, these films were characterized using gel fraction and swelling experiments, high resolution-magic angle spinning (1)H NMR spectroscopy, rheology, infrared mapping and atomic force microscopy. The results indicate that both the mechanical properties and the swelling extent of the developed hydrogel films can be controlled by varying the chemical composition and the degree of substitution of the methacrylamide-modified gelatin applied. The storage moduli of the developed materials ranged between 14 and 63kPa. Phase separation was observed for the IPNs for which separated starch domains could be distinguished located in the surrounding gelatin matrix. Furthermore, we evaluated the affinity of aggrecan for gelatin by atomic force microscopy and radiolabeling experiments. We found that aggrecan can be applied as a bioactive coating for gelatin hydrogels by a straightforward physisorption procedure. Thus, we achieved distinct fine-tuning of the physico-chemical properties of these hydrogels which render them promising candidates for tissue engineering

Recent advances in research applications of nanophase hydroxyapatite.

PubMed

Fox, Kate; Tran, Phong A; Tran, Nhiem

2012-07-16

Hydroxyapatite, the main inorganic material in natural bone, has been used widely for orthopaedic applications. Due to size effects and surface phenomena at the nanoscale, nanophase hydroxyapatite possesses unique properties compared to its bulk-phase counterpart. The high surface-to-volume ratio, reactivities, and biomimetic morphologies make nano-hydroxyapatite more favourable in applications such as orthopaedic implant coating or bone substitute filler. Recently, more efforts have been focused on the possibility of combining hydroxyapatite with other drugs and materials for multipurpose applications, such as antimicrobial treatments, osteoporosis treatments and magnetic manipulation. To build more effective nano-hydroxyapatite and composite systems, the particle synthesis processes, chemistry, and toxicity have to be thoroughly investigated. In this Minireview, we report the recent advances in research regarding nano-hydroxyapatite. Synthesis routes and a wide range of applications of hydroxyapatite nanoparticles will be discussed. The Minireview also addresses several challenges concerning the biosafety of the nanoparticles. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Facial skeletal augmentation using hydroxyapatite cement.

PubMed

Shindo, M L; Costantino, P D; Friedman, C D; Chow, L C

1993-02-01

This study investigates the use of a new calcium phosphate cement, which sets to solid, microporous hydroxyapatite, for facial bone augmentation. In six dogs, the supraorbital ridges were augmented bilaterally with this hydroxyapatite cement. On one side, the hydroxyapatite cement was placed directly onto the bone within a subperiosteal pocket. On the opposite side, the cement was contained within a collagen membrane tubule and then inserted into a subperiosteal pocket. The use of collagen tubules facilitated easy, precise placement of the cement. All implants maintained their original augmented height throughout the duration of the study. They were well tolerated without extrusion or migration, and there was no significant sustained inflammatory response. Histologic studies, performed at 3, 6, and 9 months revealed that when the cement was placed directly onto bone, progressive replacement of the implant by bone (osseointegration of the hydroxyapatite with the underlying bone) without a loss of volume was observed. In contrast, when the cement-collagen tubule combination was inserted, primarily a fibrous union was noted. Despite such fibrous union, the hydroxyapatite-collagen implant solidly bonded to the underlying bone, and no implant resorption was observed. Hydroxyapatite cement can be used successfully for the experimental augmentation of the craniofacial skeleton and may be applicable for such uses in humans.

[Adsorption of Congo red from aqueous solution on hydroxyapatite].

PubMed

Zhan, Yan-Hui; Lin, Jian-Wei

2013-08-01

The adsorption of Congo red (CR) from aqueous solution on hydroxyapatite was investigated using batch experiments. The hydroxyapatite was effective for CR removal from aqueous solution. The adsorption kinetics of CR on hydroxyapatite well followed a pseudo-second-order model. The equilibrium adsorption data of CR on hydroxyapatite could be described by the Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm models. Thermodynamic parameters such as Gibbs free energy change, enthalpy change and entropy change were calculated and showed that the adsorption of CR on hydroxyapatite was spontaneous and exothermic in nature. The CR adsorption capacity for hydroxyapatite decreased significantly with increasing pH from 8 to 10. Thermal regeneration showed that hydroxyapatite could be used for six desorption-adsorption cycles with high removal efficiency for CR in each cycle. The mechanisms for CR adsorption on hydroxyapatite with pH value below the pH at point of zero charge (pH(PZC)) include electrostatic attraction, hydrogen bonding and Lewis acid-base interaction. The mechanisms for CR adsorption on hydroxyapatite with pH value above its pH(PZC) include hydrogen bonding and Lewis acid-base interaction. Results of this work indicate that hydroxyapatite is a promising adsorbent for CR removal from aqueous solution.

Bone regeneration in the presence of a synthetic hydroxyapatite/silica oxide-based and a xenogenic hydroxyapatite-based bone substitute material.

PubMed

Kruse, A; Jung, R E; Nicholls, F; Zwahlen, R A; Hämmerle, C H F; Weber, F E

2011-05-01

A comparison of synthetic hydroxyapatite/silica oxide, xenogenic hydroxyapatite-based bone substitute materials with empty control sites in terms of bone regeneration enhancement in a rabbit calvarial four non-critical-sized defect model. In each of six rabbits, four bicortical calvarial bone defects were generated. The following four treatment modalities were randomly allocated: (1) empty control site, (2) synthetic hydroxyapatite/silica oxide-based (HA/SiO) test granules, (3) xenogenic hydroxyapatite -based granules, (4) synthetic hydroxyapatite/silica oxide -based (HA/SiO) test two granules. The results of the latter granules have not been reported due to their size being three times bigger than the other two granule types. After 4 weeks, the animals were sacrificed and un-decalcified sections were obtained for histological analyses. For statistical analysis, the Kruskal-Wallis test was applied (P<0.05). Histomorphometric analysis showed an average area fraction of newly formed bone of 12.32±10.36% for the empty control, 17.47±6.42% for the xenogenic hydroxyapatite -based granules group, and 21.2±5.32% for the group treated with synthetic hydroxyapatite/silica oxide -based granules. Based on the middle section, newly formed bone bridged the defect to 38.33±37.55% in the empty control group, 54.33±22.12% in the xenogenic hydroxyapatite -based granules group, and to 79±13.31% in the synthetic hydroxyapatite/silica oxide -based granules group. The bone-to-bone substitute contact was 46.38±18.98% for the xenogenic and 59.86±14.92% for the synthetic hydroxyapatite/silica oxide-based granules group. No significant difference in terms of bone formation and defect bridging could be detected between the two bone substitute materials or the empty defect. There is evidence that the synthetic hydroxyapatite/silica oxide granules provide comparable results with a standard xenogenic bovine mineral in terms of bone formation and defect bridging in non-critical size

Mechanical Behavior of Tough Hydrogels for Structural Applications

NASA Astrophysics Data System (ADS)

Illeperuma, Widusha Ruwangi Kaushalya

Hydrogels are widely used in many commercial products including Jell-O, contact lenses, and superabsorbent diapers. In recent decades, hydrogels have been under intense development for biomedical applications, such as scaffolds in tissue engineering, carriers for drug delivery, and valves in microfluidic systems. But the scope is severely limited as conventional hydrogels are weak and brittle and are not very stretchable. This thesis investigates the approaches that enhance the mechanical properties of hydrogels and their structural applications. We discov¬ered a class of exceptionally stretchable and tough hydrogels made from poly-mers that form networks via ionic and covalent crosslinks. Although such a hydrogel contains ~90% water, it can be stretched beyond 20 times its initial length, and has a fracture energy of ~9000 J/m2. The combination of large stretchability, remarkable toughness, and recoverability of stiffness and toughness, along with easy synthesis makes this material much superior over existing hydrogels. Extreme stretchability and blunted crack tips of these hydrogels question the validity of traditional fracture testing methods. We re-examine a widely used pure shear test method to measure the fracture energy. With the experimental and simulation results, we conclude that the pure shear test method can be used to measure fracture energy of extremely stretchable materials. Even though polyacrylamide-alginate hydrogels have an extremely high toughness, it has a relatively low stiffness and strength. We improved the stiffness and strength by embedding fibers. Most hydrogels are brittle, allowing the fibers to cut through the hydrogel when the composite is loaded. But tough hydrogel composites do not fail by the fibers cutting the hydrogel; instead, it undergoes large deforming by fibers sliding through the matrix. Hydrogels were not considered as materials for structural applications. But with enhanced mechanical properties, they have opened up

Nanocrystalline heterojunction materials

DOEpatents

Elder, Scott H.; Su, Yali; Gao, Yufei; Heald, Steve M.

2003-07-15

Mesoporous nanocrystalline titanium dioxide heterojunction materials are disclosed. In one disclosed embodiment, materials comprising a core of titanium dioxide and a shell of a molybdenum oxide exhibit a decrease in their photoadsorption energy as the size of the titanium dioxide core decreases.

Spectral analysis of allogeneic hydroxyapatite powders

NASA Astrophysics Data System (ADS)

Timchenko, P. E.; Timchenko, E. V.; Pisareva, E. V.; Vlasov, M. Yu; Red'kin, N. A.; Frolov, O. O.

2017-01-01

In this paper we discuss the application of Raman spectroscopy to the in vitro analysis of the hydroxyapatite powder samples produced from different types of animal bone tissue during demineralization process at various acid concentrations and exposure durations. The derivation of the Raman spectrum of hydroxyapatite is attempted by the analysis of the pure powders of its known constituents. Were experimentally found spectral features of hydroxyapatite, based on analysis of the line amplitude at wave numbers 950-965 cm-1 ((PO4)3- (ν1) vibration) and 1065-1075 cm-1 ((CO3)2-(ν1) B-type replacement). Control of physicochemical properties of hydroxyapatite was carried out by Raman spectroscopy. Research results are compared with an infrared Fourier spectroscopy.

Carbon nanotubes play an important role in the spatial arrangement of calcium deposits in hydrogels for bone regeneration.

PubMed

Cancian, Giulia; Tozzi, Gianluca; Hussain, Amirul Ashraf Bin; De Mori, Arianna; Roldo, Marta

2016-08-01

Age related bone diseases such as osteoporosis are considered among the main causes of reduced bone mechanical stability and bone fractures. In order to restore both biological and mechanical function of diseased/fractured bones, novel bioactive scaffolds that mimic the bone structure are constantly under development in tissue engineering applications. Among the possible candidates, chitosan-based thermosensitive hydrogel scaffolds represent ideal systems due to their biocompatibility, biodegradability, enhanced antibacterial properties, promotion of osteoblast formation and ease of injection, which makes them suitable for less invasive surgical procedures. As a main drawback, these chitosan systems present poor mechanical performance that could not support load-bearing applications. In order to produce more mechanically-competent biomaterials, the combined addition of hydroxyapatite and carbon nanotubes (CNTs) is proposed in this study. Specifically, the aim of this work is to develop thermosensitive chitosan hydrogels containing stabilised single-walled and multi-walled CNTs, where their effect on the mechanical/physiochemical properties, calcium deposition patterns and ability to provide a platform for the controlled release of protein drugs was investigated. It was found that the addition of CNTs had a significant effect on the sol-gel transition time and significantly increased the resistance to compression for the hydrogels. Moreover, in vitro calcification studies revealed that CNTs played a major role in the spatial arrangements of newly formed calcium deposits in the composite materials studied, suggesting that they may have a role in the way the repair of fragile and/or fractured bones occurs in vivo.

In situ generation of sodium alginate/hydroxyapatite nanocomposite beads as drug-controlled release matrices.

PubMed

Zhang, J; Wang, Q; Wang, A

2010-02-01

In order to find a new way to slow down the release of drugs and to solve the burst release problem of drugs from traditionally used hydrogel matrices, a series of novel pH-sensitive sodium alginate/hydroxyapatite (SA/HA) nanocomposite beads was prepared by the in situ generation of HA micro-particles in the beads during the sol-gel transition process of SA. The SA/HA nanocomposites were characterized by Fourier transform IR spectroscopy, X-ray fluorescence spectrometry, scanning electron microscopy and field emission SEM in order to reveal their composition and surface morphology as well as the role that the in situ generated HA micro-particles play. The factors influencing the swelling behavior, drug loading and controlled release behavior of the SA/HA nanocomposite beads were also investigated using diclofenac sodium (DS) as the model drug. The HA micro-particles act as inorganic crosslinkers in the nanocomposites, which could contract and restrict the movability of the SA polymer chains, and then change the surface morphology and decrease the swell ratio. Meanwhile, the entrapment efficiency of DS was improved, and the burst release of DS was overcome. The factors (including concentration of Ca(2+), reaction time and temperature) affecting the growth of HA micro-particles have a clear influence on the entrapment efficiency and release rate of DS. In this work, the nanocomposite beads prepared under optimum condition could prolong the release of DS for 8h more compared with the pristine SA hydrogel beads.

Synthesis of Nano-Crystalline Gamma-TiAl Materials

NASA Technical Reports Server (NTRS)

Hales, Stephen J.; Vasquez, Peter

2003-01-01

One of the principal problems with nano-crystalline materials is producing them in quantities and sizes large enough for valid mechanical property evaluation. The purpose of this study was to explore an innovative method for producing nano-crystalline gamma-TiAl bulk materials using high energy ball milling and brief secondary processes. Nano-crystalline powder feedstock was produced using a Fritsch P4(TM) vario-planetary ball mill recently installed at NASA-LaRC. The high energy ball milling process employed tungsten carbide tooling (vials and balls) and no process control agents to minimize contamination. In a collaborative effort, two approaches were investigated, namely mechanical alloying of elemental powders and attrition milling of pre-alloyed powders. The objective was to subsequently use RF plasma spray deposition and short cycle vacuum hot pressing in order to effect consolidation while retaining nano-crystalline structure in bulk material. Results and discussion of the work performed to date are presented.

Initial stage corrosion of nanocrystalline copper particles and thin films

NASA Astrophysics Data System (ADS)

Tao, Weimin

1997-12-01

Corrosion behavior is an important issue in nanocrystalline materials research and development. A very fine grain size is expected to have significant effects on the corrosion resistance of these novel materials. However, both the macroscopic corrosion properties and the corresponding structure evolution during corrosion have not been fully studied. Under such circumstances, conducting fundamental research in this area is important and necessary. In this study, high purity nanocrystalline and coarse-grained copper were selected as our sample material, sodium nitrite aqueous solution at room temperature and air at a high temperature were employed as corrosive environments. The weight loss testing and electrochemical methods were used to obtain the macroscopic corrosion properties, whereas the high resolution transmission electron microscope was employed for the structure analysis. The weight loss tests indicate that the corrosion rate of nanocrystalline copper is about 5 times higher than that of coarse-grained copper at the initial stage of corrosion. The electrochemical measurements show that the corrosion potential of the nanocrystalline copper has a 230 mV negative shift in comparison with that of the coarse-grained copper. The nanocrystalline copper also exhibits a significantly higher exchange current density than the coarse-grained copper. High resolution TEM revealed that the surface structure changes at the initial stage of corrosion. It was found that the first copper oxide layer formed on the surface of nanocrystalline copper thin film contains a large density of high angle grain boundaries, whereas that formed on the surface of coarse-grained copper shows highly oriented oxide nuclei and appears to show a strong tendency for forming low angle grain boundaries. A correlation between the macroscopic corrosion properties and the structure characteristics is proposed for the nanocrystalline copper based on the concept of the "apparent" exchange current

Development of hydroxyapatite/polyvinyl alcohol bionanocomposite for prosthesis implants

NASA Astrophysics Data System (ADS)

Karthik, V.; Pabi, S. K.; Chowdhury, S. K. Roy

2018-02-01

Hydroxyapatite (Ca10(PO4)6(OH)2) has similar structural and chemical properties of natural bone mineral and hence widely used as a bone replacement substitute. Natural bone consists of hydroxyapatite and collagen. For mimicking the natural, in the present work, a sintered porous hydroxyapatite component has been vacuum impregnated with Polyvinyl alcohol (PVA), which has better properties like biocompatibility, biodegradability and water- solubility. Hydroxyapatite powders have been made into nanosize to reduce the melting point and hence the sintering temperature. In the present investigation high energy ball mill is used to produce nano-hydroxyapatite powders in bulk quantity by optimizing the milling parameters using stainless steel grinding media. Pellets of 10 mm diameter have been produced from nano- hydroxyapatite powders under different uniaxial compaction pressures. The pellets have been sintered to form porous compacts. The vacuum impregnation of sintered pallets with PVA solution of different strength has been done to find the optimum impregnation condition. Microhardness, compressive strength, wear loss and haemocompatibility of hydroxyapatite ceramics have been studied before and after impregnation of PVA. The nano- hydroxyapatite/PVA composites have superior mechanical properties and reduced wear loss than the non-impregnated porous nano-hydroxyapatite ceramics.

Hydrogels with covalent and noncovalent crosslinks

NASA Technical Reports Server (NTRS)

Kilck, Kristi L. (Inventor); Yamaguchi, Nori (Inventor)

2013-01-01

A method for targeted delivery of therapeutic compounds from hydrogels is presented. The method involves administering to a cell a hydrogel in which a therapeutic compound is noncovalently bound to heparin. The hydrogel may contain covalent and non-covalent crosslinks.

Energy conversion in polyelectrolyte hydrogels

NASA Astrophysics Data System (ADS)

Olvera de La Cruz, Monica; Erbas, Aykut; Olvera de la Cruz Team

Energy conversion and storage have been an active field of research in nanotechnology parallel to recent interests towards renewable energy. Polyelectrolyte (PE) hydrogels have attracted considerable attention in this field due to their mechanical flexibility and stimuli-responsive properties. Ideally, when a hydrogel is deformed, applied mechanical work can be converted into electrostatic, elastic and steric-interaction energies. In this talk, we discuss the results of our extensive molecular dynamics simulations of PE hydrogels. We demonstrate that, on deformation, hydrogels adjust their deformed state predominantly by altering electrostatic interactions between their charged groups rather than excluded-volume and bond energies. This is due to the hydrogel's inherent tendency to preserve electro-neutrality in its interior, in combination with correlations imposed by backbone charges. Our findings are valid for a wide range of compression ratios and ionic strengths. The electrostatic-energy alterations that we observe in our MD simulations may induce pH or redox-potential changes inside the hydrogels. The resulting energetic difference can be harvested, for instance, analogously to a Carnot engine, or facilitated for sensor applications. Center for Bio-inspired Energy Science (CBES).

The fabrication of well-interconnected polycaprolactone/hydroxyapatite composite scaffolds, enhancing the exposure of hydroxyapatite using the wire-network molding technique.

PubMed

Cho, Yong Sang; Hong, Myoung Wha; Jeong, Hoon-Jin; Lee, Seung-Jae; Kim, Young Yul; Cho, Young-Sam

2017-11-01

In this study, the fabrication method was proposed for the well-interconnected polycaprolactone/hydroxyapatite composite scaffold with exposed hydroxyapatite using modified WNM technique. To characterize well-interconnected scaffolds in terms of hydroxyapatite exposure, several assessments were performed as follows: morphology, mechanical property, wettability, calcium ion release, and cell response assessments. The results of these assessments were compared with those of control scaffolds which were fabricated by precision extruding deposition (PED) apparatus. The control PED scaffolds have interconnected pores with nonexposed hydroxyapatite. Consequently, cell attachment of proposed WNM scaffold was improved by increased hydrophilicity and surface roughness of scaffold surface resulting from the exposure of hydroxyapatite particles and fabrication process using powders. Moreover, cell proliferation and differentiation of WNM scaffold were increased, because the exposure of hydroxyapatite particles may enhance cell adhesion and calcium ion release. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2315-2325, 2017. © 2016 Wiley Periodicals, Inc.

Bone augmentation at peri-implant dehiscence defects comparing a synthetic polyethylene glycol hydrogel matrix vs. standard guided bone regeneration techniques.

PubMed

Thoma, Daniel S; Jung, Ui-Won; Park, Jin-Young; Bienz, Stefan P; Hüsler, Jürg; Jung, Ronald E

2017-07-01

The aim of the study was to test whether or not the use of a polyethylene glycol (PEG) hydrogel with or without the addition of an arginylglycylaspartic acid (RGD) sequence applied as a matrix in combination with hydroxyapatite/tricalciumphosphate (HA/TCP) results in similar peri-implant bone regeneration as traditional guided bone regeneration procedures. In 12 beagle dogs, implant placement and peri-implant bone regeneration were performed 2 months after tooth extraction in the maxilla. Two standardized box-shaped defects were bilaterally created, and dental implants were placed in the center of the defects with a dehiscence of 4 mm. Four treatment modalities were randomly applied: i)HA/TCP mixed with a synthetic PEG hydrogel, ii)HA/TCP mixed with a synthetic PEG hydrogel supplemented with an RGD sequence, iii)HA/TCP covered with a native collagen membrane (CM), iv)and no bone augmentation (empty). After a healing period of 8 or 16 weeks, micro-CT and histological analyses were performed. Histomorphometric analysis revealed a greater relative augmented area for groups with bone augmentation (43.3%-53.9% at 8 weeks, 31.2%-42.8% at 16 weeks) compared to empty controls (22.9% at 8 weeks, 1.1% at 16 weeks). The median amount of newly formed bone was greatest in group CM at both time-points. Regarding the first bone-to-implant contact, CM was statistically significantly superior to all other groups at 8 weeks. Bone can partially be regenerated at peri-implant buccal dehiscence defects using traditional guided bone regeneration techniques. The use of a PEG hydrogel applied as a matrix mixed with a synthetic bone substitute material might lack a sufficient stability over time for this kind of defect. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Supramolecular Hydrogels Based on DNA Self-Assembly.

PubMed

Shao, Yu; Jia, Haoyang; Cao, Tianyang; Liu, Dongsheng

2017-04-18

Extracellular matrix (ECM) provides essential supports three dimensionally to the cells in living organs, including mechanical support and signal, nutrition, oxygen, and waste transportation. Thus, using hydrogels to mimic its function has attracted much attention in recent years, especially in tissue engineering, cell biology, and drug screening. However, a hydrogel system that can merit all parameters of the natural ECM is still a challenge. In the past decade, deoxyribonucleic acid (DNA) has arisen as an outstanding building material for the hydrogels, as it has unique properties compared to most synthetic or natural polymers, such as sequence designability, precise recognition, structural rigidity, and minimal toxicity. By simple attachment to polymers as a side chain, DNA has been widely used as cross-links in hydrogel preparation. The formed secondary structures could confer on the hydrogel designable responsiveness, such as response to temperature, pH, metal ions, proteins, DNA, RNA, and small signal molecules like ATP. Moreover, single or multiple DNA restriction enzyme sites could be incorporated into the hydrogels by sequence design and greatly expand the latitude of their responses. Compared with most supramolecular hydrogels, these DNA cross-linked hydrogels could be relatively strong and easily adjustable via sequence variation, but it is noteworthy that these hydrogels still have excellent thixotropic properties and could be easily injected through a needle. In addition, the quick formation of duplex has also enabled the multilayer three-dimensional injection printing of living cells with the hydrogel as matrix. When the matrix is built purely by DNA assembly structures, the hydrogel inherits all the previously described characteristics; however, the long persistence length of DNA structures excluded the small size meshes of the network and made the hydrogel permeable to nutrition for cell proliferation. This unique property greatly expands the cell

Electrochemical immunoassay for tumor markers based on hydrogels.

PubMed

Yin, Shuang; Ma, Zhanfang

2018-05-08

Hydrogel-based electrochemical immunoassays exhibit a large surface-to-volume ratio, excellent biocompatibility, unique stimuli-responsive behavior, high permeability and hydrophilicity and, thus, have shown great potential in the sensitive and accurate detection of tumor markers. Electrochemical immunosensing techniques for tumor markers based on hydrogels have greatly progressed in recent years. Areas covered: In this review, the authors describe the recent advances of hydrogel-based electrochemical immunosensing interface of tumor markers based on the different functions of hydrogels including conductive, catalytic, redox, stimuli-responsive and antifouling hydrogels. Expert commentary: Hydrogels have been successfully employed in electrochemical immunoassay of tumor markers, which is accountable to their unique properties. For further exploitation of hydrogel-based electrochemical biosensors, more variety of hydrogels need be fabricated with improved functionality.

Bio-inspired self-healing structural color hydrogel

PubMed Central

Fu, Fanfan; Chen, Zhuoyue; Zhao, Ze; Wang, Huan; Shang, Luoran; Gu, Zhongze

2017-01-01

Biologically inspired self-healing structural color hydrogels were developed by adding a glucose oxidase (GOX)- and catalase (CAT)-filled glutaraldehyde cross-linked BSA hydrogel into methacrylated gelatin (GelMA) inverse opal scaffolds. The composite hydrogel materials with the polymerized GelMA scaffold could maintain the stability of an inverse opal structure and its resultant structural colors, whereas the protein hydrogel filler could impart self-healing capability through the reversible covalent attachment of glutaraldehyde to lysine residues of BSA and enzyme additives. A series of unprecedented structural color materials could be created by assembling and healing the elements of the composite hydrogel. In addition, as both the GelMA and the protein hydrogels were derived from organisms, the composite materials presented high biocompatibility and plasticity. These features of self-healing structural color hydrogels make them excellent functional materials for different applications. PMID:28533368

Valorization of Bone Waste of Saudi Arabia by Synthesizing Hydroxyapatite.

PubMed

Amna, Touseef

2018-05-09

At present, hydroxyapatite is being frequently used for diverse biomedical applications as it possesses excellent biocompatibility, osteoconductivity, and non-immunogenic characteristics. The aim of the present work was to recycle bone waste for synthesis of hydroxyapatite nanoparticles to be used as bone extracellular matrix. For this reason, we for the first time utilized bio-waste of cow bones of Albaha city. The residual bones were utilized for the extraction of natural bone precursor hydroxyapatite. A facile scientific technique has been used to synthesize hydroxyapatite nanoparticles through calcinations of wasted cow bones without further supplementation of chemicals/compounds. The obtained hydroxyapatite powder was ascertained using physicochemical techniques such as XRD, SEM, FTIR, and EDX. These analyses clearly show that hydroxyapatite from native cow bone wastes is biologically and physicochemically comparable to standard hydroxyapatite, commonly used for biomedical functions. The cell viability and proliferation over the prepared hydroxyapatite was confirmed with CCk-8 colorimetric assay. The morphology of the cells growing over the nano-hydroxyapatite shows that natural hydroxyapatite promotes cellular attachment and proliferation. Hence, the as-prepared nano-hydroxyapatite can be considered as cost-effective source of bone precursor hydroxyapatite for bone tissue engineering. Taking into account the projected demand for reliable bone implants, the present research work suggested using environment friendly methods to convert waste of Albaha city into nano-hydroxyapatite scaffolds. Therefore, besides being an initial step towards accomplishment of projected demands of bone implants in Saudi Arabia, our study will also help in reducing the environmental burden by recycling of bone wastes of Albaha city.

Application of micro- and nanocrystalline cellulose

NASA Astrophysics Data System (ADS)

Sotnikova, Yu S.; Demina, T. S.; Istomin, A. V.; Goncharuk, G. P.; Grandfils, Ch; Akopova, T. A.; Zelenetskii, A. N.; Babayevsky, P. G.

2018-04-01

Micro- and nanocrystalline forms of cellulose were extracted from flax stalks and evaluated in terms of their applicability for various materials science tasks. It was revealed that both form of cellulose had anisometric morphology with length of 27.1 μm and 159 nm; diameter of 8.7 μm and 85 nm, respectively. They were used as reinforcing fillers for fabrication of composite films based on hydroxyethylcellulose. Film-forming and mechanical properties of the composite materials were significantly varied in dependence on filler content (0–10 wt.%) and size. As a second option of micro- and nanocrystalline cellulose application, a study of their effectiveness as stabilizing agents for oil/water Pickering emulsions was carried out. In contrast to micron-sized cellulose the nanocrystalline form appeared to be successful in the process of CH2Cl2/water interface stabilization and fabrication of polylactide microparticles via oil/water Pickering emulsion solvent evaporation technique.

Chitosan based hydrogels: characteristics and pharmaceutical applications

PubMed Central

Ahmadi, F.; Oveisi, Z.; Samani, S. Mohammadi; Amoozgar, Z.

2015-01-01

Hydrogel scaffolds serve as semi synthetic or synthetic extra cellular matrix to provide an amenable environment for cellular adherence and cellular remodeling in three dimensional structures mimicking that of natural cellular environment. Additionally, hydrogels have the capacity to carry small molecule drugs and/or proteins, growth factors and other necessary components for cell growth and differentiation. In the context of drug delivery, hydrogels can be utilized to localize drugs, increase drugs concentration at the site of action and consequently reduce off-targeted side effects. The current review aims to describe and classify hydrogels and their methods of production. The main highlight is chitosan-based hydrogels as biocompatible and medically relevant hydrogels for drug delivery. PMID:26430453

Investigations of Nanocrystalline Alloy Electrospark Coating Made of Nanocrystalline Alloy Based on 5БДCP Ferrum

NASA Astrophysics Data System (ADS)

Kolomeichenko, A. V.; Kuznetsov, I. S.; Izmaylov, A. Yu; Solovyev, R. Yu; Sharifullin, S. N.

2017-09-01

The article describes the properties of wear resistant electrospark coating made of nanocrystalline alloy of type 5БДCP (Finemet). It is proved that electrospark coating has nanocrystalline structure which is like amorphous matrix with nanocrystals α - Fe. Coating thickness is 33 μm, micro-hardness is 8461 - 11357 MPa, wear resistance is 0,55×104s/g. Coating ofnanocrystalline alloy of type 5БДCP can be used to increase wear resistance of machinery working surfaces.

Methods of synthesizing hydroxyapatite powders and bulk materials

DOEpatents

Luo, Ping

1999-01-12

Methods are provided for producing non-porous controlled morphology hydroxyapatite granules of less than 8 .mu.m by a spray-drying process. Solid or hollow spheres or doughnuts can be formed by controlling the volume fraction and viscosity of the slurry as well as the spray-drying conditions. Methods of providing for homogenous cellular structure hydroxyapatite granules are also provided. Pores or channels or varying size and number can be formed by varying the temperature at which a hydroxyapatite slurry formed in basic, saturated ammonium hydroxide is spray-dried. Methods of providing non-porous controlled morphology hydroxyapatite granules in ammonium hydroxide are also provided. The hydroxyapatite granules and bulk materials formed by these methods are also provided.

Methods of synthesizing hydroxyapatite powders and bulk materials

DOEpatents

Luo, P.

1999-01-12

Methods are provided for producing non-porous controlled morphology hydroxyapatite granules of less than 8 {micro}m by a spray-drying process. Solid or hollow spheres or doughnuts can be formed by controlling the volume fraction and viscosity of the slurry as well as the spray-drying conditions. Methods of providing for homogeneous cellular structure hydroxyapatite granules are also provided. Pores or channels or varying size and number can be formed by varying the temperature at which a hydroxyapatite slurry formed in basic, saturated ammonium hydroxide is spray-dried. Methods of providing non-porous controlled morphology hydroxyapatite granules in ammonium hydroxide are also provided. The hydroxyapatite granules and bulk materials formed by these methods are also provided. 26 figs.

Characterization of Nanocrystalline Aluminum Alloy 5083 Powders Produced by Cryogenic Attrition

DTIC Science & Technology

2014-11-01

Characterization of Nanocrystalline Aluminum Alloy 5083 Powders Produced by Cryogenic Attrition by Tiffany Ngo ARL-TN-0643...November 2014 Characterization of Nanocrystalline Aluminum Alloy 5083 Powders Produced by Cryogenic Attrition Tiffany Ngo Weapons and...3. DATES COVERED (From - To) August 2014 4. TITLE AND SUBTITLE Characterization of Nanocrystalline Aluminum Alloy 5083 Powders Produced by

Cross-Linked Hydrogel for Pharmaceutical Applications: A Review

PubMed Central

2017-01-01

Hydrogels are promising biomaterials because of their important qualities such as biocompatibility, biodegradability, hydrophilicity and non-toxicity. These qualities make hydrogels suitable for application in medical and pharmaceutical field. Recently, a tremendous growth of hydrogel application is seen, especially as gel and patch form, in transdermal drug delivery. This review mainly focuses on the types of hydrogels based on cross-linking and; secondly to describe the possible synthesis methods to design hydrogels for different pharmaceutical applications. The synthesis and chemistry of these hydrogels are discussed using specific pharmaceutical examples. The structure and water content in a typical hydrogel have also been discussed. PMID:29399542

Nanocrystalline cellulose from coir fiber: preparation, properties, and applications

USDA-ARS?s Scientific Manuscript database

Nanocrystalline cellulose derived from various botanical sources offers unique and potentially useful characteristics. In principle, any cellulosic material can be considered as a potential source of a nanocrystalline material, including crops, crop residues, and agroindustrial wastes. Because of t...

Synthetic Hydroxyapatite as a Biomimetic Oral Care Agent.

PubMed

Enax, Joachim; Epple, Matthias

Human tooth enamel consists mostly of minerals, primarily hydroxyapatite, Ca10(PO4)6(OH)2, and thus synthetic hydroxyapatite can be used as a biomimetic oral care agent. This review describes the synthesis and characterization of hydroxyapatite from a chemist's perspective and provides an overview of its current use in oral care, with a focus on dentin hypersensitivity, caries, biofilm management, erosion, and enamel lesions. Reviews and original research papers published in English and German were included. The efficiency of synthetic hydroxyapatite in occluding open dentin tubules, resulting in a protection for sensitive teeth, has been well documented in a number of clinical studies. The first corresponding studies on caries, biofilm management and erosion have provided evidence for a positive effect of hydroxyapatite either as a main or synergistic agent in oral care products. However, more in situ and in vivo studies are needed due to the complexity of the oral milieu and to further clarify existing results. Due to its biocompatibility and similarity to biologically formed hydroxyapatite in natural tooth enamel, synthetic hydroxyapatite is a promising biomimetic oral care ingredient that may extend the scope of preventive dentistry.

Tunable hydrogel composite with two-step processing in combination with innovative hardware upgrade for cell-based three-dimensional bioprinting.

PubMed

Wüst, Silke; Godla, Marie E; Müller, Ralph; Hofmann, Sandra

2014-02-01

Three-dimensional (3-D) bioprinting is the layer-by-layer deposition of biological material with the aim of achieving stable 3-D constructs for application in tissue engineering. It is a powerful tool for the spatially directed placement of multiple materials and/or cells within the 3-D sample. Encapsulated cells are protected by the bioink during the printing process. Very few materials are available that fulfill requirements for bioprinting as well as provide adequate properties for cell encapsulation during and after the printing process. A hydrogel composite including alginate and gelatin precursors was tuned with different concentrations of hydroxyapatite (HA) and characterized in terms of rheology, swelling behavior and mechanical properties to assess the versatility of the system. Instantaneous as well as long-term structural integrity of the printed hydrogel was achieved with a two-step mechanism combining the thermosensitive properties of gelatin with chemical crosslinking of alginate. Novel syringe tip heaters were developed for improved temperature control of the bioink to avoid clogging. Human mesenchymal stem cells mixed into the hydrogel precursor survived the printing process and showed high cell viability of 85% living cells after 3 days of subsequent in vitro culture. HA enabled the visualization of the printed structures with micro-computed tomography. The inclusion of HA also favors the use of the bioink for bone tissue engineering applications. By adding factors other than HA, the composite could be used as a bioink for applications in drug delivery, microsphere deposition or soft tissue engineering. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Peptide hydrogelation triggered by enzymatic induced pH switch

NASA Astrophysics Data System (ADS)

Cheng, Wei; Li, Ying

2016-07-01

It remains challenging to develop methods that can precisely control the self-assembling kinetics and thermodynamics of peptide hydrogelators to achieve hydrogels with optimal properties. Here we report the hydrogelation of peptide hydrogelators by an enzymatically induced pH switch, which involves the combination of glucose oxidase and catalase with D-glucose as the substrate, in which both the gelation kinetics and thermodynamics can be controlled by the concentrations of D-glucose. This novel hydrogelation method could result in hydrogels with higher mechanical stability and lower hydrogelation concentrations. We further illustrate the application of this hydrogelation method to differentiate different D-glucose levels.

Nanocrystalline Heterojunction Materials

DOEpatents

Elder, Scott H.; Su, Yali; Gao, Yufei; Heald, Steve M.

2004-02-03

Mesoporous nanocrystalline titanium dioxide heterojunction materials and methods of making the same are disclosed. In one disclosed embodiment, materials comprising a core of titanium dioxide and a shell of a molybdenum oxide exhibit a decrease in their photoadsorption energy as the size of the titanium dioxide core decreases.

Mechanical properties and biocompatibility of the sputtered Ti doped hydroxyapatite.

PubMed

Vladescu, A; Padmanabhan, S C; Ak Azem, F; Braic, M; Titorencu, I; Birlik, I; Morris, M A; Braic, V

2016-10-01

The hydroxyapatite enriched with Ti were prepared as possible candidates for biomedical applications especially for implantable devices that are in direct contact to the bone. The hydroxyapatites with different Ti content were prepared by RF magnetron sputtering on Ti-6Al-4V alloy using pure hydroxyapatite and TiO2 targets. The content of Ti was modified by changing the RF power fed on TiO2 target. The XPS and FTIR analyses revealed the presence of hydroxyapatite structure. The hardness and elastic modulus of the hydroxyapatite were increased by Ti addition. After 5 days of culture, the cell viability of the Ti-6Al-4V was enhanced by depositing with undoped or doped hydroxyapatite. The Ti additions led to an increase in cell viability of hydroxyapatite, after 5 days of culture. The electron microscopy showed the presence of more cells on the surface of Ti-enriched hydroxyapatite than those observed on the surface of the uncoated alloys or undoped hydroxyapatite. Copyright © 2016 Elsevier Ltd. All rights reserved.

Enzymatically crosslinked silk-hyaluronic acid hydrogels.

PubMed

Raia, Nicole R; Partlow, Benjamin P; McGill, Meghan; Kimmerling, Erica Palma; Ghezzi, Chiara E; Kaplan, David L

2017-07-01

In this study, silk fibroin and hyaluronic acid (HA) were enzymatically crosslinked to form biocompatible composite hydrogels with tunable mechanical properties similar to that of native tissues. The formation of di-tyrosine crosslinks between silk fibroin proteins via horseradish peroxidase has resulted in a highly elastic hydrogel but exhibits time-dependent stiffening related to silk self-assembly and crystallization. Utilizing the same method of crosslinking, tyramine-substituted HA forms hydrophilic and bioactive hydrogels that tend to have limited mechanics and degrade rapidly. To address the limitations of these singular component scaffolds, HA was covalently crosslinked with silk, forming a composite hydrogel that exhibited both mechanical integrity and hydrophilicity. The composite hydrogels were assessed using unconfined compression and infrared spectroscopy to reveal of the physical properties over time in relation to polymer concentration. In addition, the hydrogels were characterized by enzymatic degradation and for cytotoxicity. Results showed that increasing HA concentration, decreased gelation time, increased degradation rate, and reduced changes that were observed over time in mechanics, water retention, and crystallization. These hydrogel composites provide a biologically relevant system with controllable temporal stiffening and elasticity, thus offering enhanced tunable scaffolds for short or long term applications in tissue engineering. Copyright © 2017 Elsevier Ltd. All rights reserved.

Injectable hydrogels for delivering biotherapeutic molecules.

PubMed

Mathew, Ansuja Pulickal; Uthaman, Saji; Cho, Ki-Hyun; Cho, Chong-Su; Park, In-Kyu

2018-04-15

To date, numerous delivery systems based on either organic or inorganic material have been developed to achieve efficient and sustained delivery of therapeutics. Hydrogels, which are three dimensional networks of crosslinked hydrophilic polymers, have a significant role in solving the clinical and pharmacological limitations of present systems because of their biocompatibility, ease of preparation and unique physical properties such as a tunable porous nature and affinity for biological fluids. Development of an in situ forming injectable hydrogel system has allowed excellent spatial and temporal control, unlike systemically administered therapeutics. Injectable hydrogel systems can offset difficulties with conventional hydrogel-based drug delivery systems in the clinic by forming a drug/gene delivery or cell-growing depot in the body with a single injection, thereby enabling patient compliance and comfort. Carbohydrate polymers are widely used for the synthesis of injectable in situ-forming hydrogels because of ready availability, presence of modifiable functional groups, biocompatibility and other physiochemical properties. In this review, we discuss different aspects of injectable hydrogels, such as bulk hydrogels/macrogels, microgels, and nanogels derived from natural polymers, and their importance in the delivery of therapeutics such as genes, drugs, cells or other biomolecules and how these revolutionary systems can complement existing therapeutic delivery systems. Copyright © 2017 Elsevier B.V. All rights reserved.

Methods for preparation of nanocrystalline rare earth phosphates for lighting applications

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

Comanzo, Holly Ann; Manoharan, Mohan; Martins Loureiro, Sergio Paulo

Disclosed here are methods for the preparation of optionally activated nanocrystalline rare earth phosphates. The optionally activated nanocrystalline rare earth phosphates may be used as one or more of quantum-splitting phosphor, visible-light emitting phosphor, vacuum-UV absorbing phosphor, and UV-emitting phosphor. Also disclosed herein are discharge lamps comprising the optionally activated nanocrystalline rare earth phosphates provided by these methods.

Photopolymerizable chitosan-collagen hydrogels for bone tissue engineering.

PubMed

Arakawa, Christopher; Ng, Ronald; Tan, Steven; Kim, Soyon; Wu, Benjamin; Lee, Min

2017-01-01

Photopolymerizable hydrogels derived from naturally occurring polymers have attracted significant interest in tissue-engineering applications due to their excellent biocompatibility, hydrophilic nature favourable for cell ingrowth and ability to be cured in situ through a minimally invasive procedure. In this study, we developed a composite hydrogel consisting of photocrosslinkable methacrylated glycol chitosan (MeGC) and semi-interpenetrating collagen (Col) with a riboflavin photoinitiator under blue light. The incorporation of Col in MeGC hydrogels enhanced the compressive modulus and slowed the degradation rate of the hydrogels. MeGC-Col composite hydrogels significantly enhanced cellular attachment, spreading, proliferation and osteogenic differentiation of mouse bone marrow stromal cells (BMSCs) seeded on the hydrogels compared with pure MeGC hydrogels, as observed by upregulated alkaline phosphatase (ALP) activity as well as increased mineralization. Similarly, when cells were encapsulated within hydrogels, BMSCs exhibited greater proliferation, ALP activity and mineral deposits in the presence of Col. These findings demonstrate that MeGC-Col composite hydrogels may be useful in promoting bone regeneration. Copyright © 2014 John Wiley & Sons, Ltd. Copyright © 2014 John Wiley & Sons, Ltd.

Novel Hydrogels from Renewable Resources

NASA Astrophysics Data System (ADS)

Karaaslan, Muzafer Ahmet

2011-12-01

The cell wall of most plant biomass from forest and agricultural resources consists of three major polymers, cellulose, hemicellulose and lignin. Of these, hemicelluloses have gained increasing attention as sustainable raw materials. In the first part of this study, novel pH-sensitive semi-IPN hydrogels based on hemicelluloses and chitosan were prepared using glutaraldehyde as the crosslinking agent. The hemicellulose isolated from aspen was analyzed for sugar content by HPLC, and its molecular weight distribution was determined by high performance size exclusion chromatography. Results revealed that hemicellulose had a broad molecular weight distribution with a fair amount of polymeric units, together with xylose, arabinose and glucose. The effect of hemicellulose content on mechanical properties and swelling behavior of hydrogels were investigated. The semi-IPNs hydrogel structure was confirmed by FT-IR, X-ray study and ninhydrin assay method. X-ray analysis showed that higher hemicellulose contents yielded higher crystallinity. Mechanical properties were mainly dependent on the crosslink density and average molecular weight between crosslinks. Swelling ratios increased with increasing hemicellulose content and were high at low pH values due to repulsion between similarly charged groups. In vitro release study of a model drug showed that these semi-IPN hydrogels could be used for controlled drug delivery into gastric fluid. The aim of the second part of this study was to control the crosslink density and the mechanical properties of hemicellulose/chitosan semi-IPN hydrogels by changing the crosslinking sequence. It has been hypothesized that by performing the crosslinking step before introducing hemicellulose, covalent crosslinking of chitosan would not be hindered and therefore more and/or shorter crosslinks could be formed. Furthermore, additional secondary interactions and crystalline domains introduced through hemicellulose could be favorable in terms of

Hydroxyapatite-silver nanoparticles coatings on porous polyurethane scaffold.

PubMed

Ciobanu, Gabriela; Ilisei, Simona; Luca, Constantin

2014-02-01

The present paper is focused on a study regarding the possibility of obtaining hydroxyapatite-silver nanoparticle coatings on porous polyurethane scaffold. The method applied is based on a combined strategy involving hydroxyapatite biomimetic deposition on polyurethane surface using a Supersaturated Calcification Solution (SCS), combined with silver ions reduction and in-situ crystallization processes on hydroxyapatite-polyurethane surface by sample immersing in AgNO3 solution. The morphology, composition and phase structure of the prepared samples were characterized by scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX), X-ray diffraction (XRD), UV-Vis spectroscopy and X-ray photoelectron spectroscopy (XPS) measurements. The data obtained show that a layer of hydroxyapatite was deposited on porous polyurethane support and the silver nanoparticles (average size 34.71 nm) were dispersed among and even on the hydroxyapatite crystals. Hydroxyapatite/polyurethane surface acts as a reducer and a stabilizing agent for silver ions. The surface plasmon resonance peak in UV-Vis absorption spectra showed an absorption maximum at 415 nm, indicating formation of silver nanoparticles. The hydroxyapatite-silver polyurethane scaffolds were tested against Staphylococcus aureus and Escherichia coli and the obtained data were indicative of good antibacterial properties of the materials. © 2013.

Nanocrystalline cerium oxide materials for solid fuel cell systems

DOEpatents

Brinkman, Kyle S

2015-05-05

Disclosed are solid fuel cells, including solid oxide fuel cells and PEM fuel cells that include nanocrystalline cerium oxide materials as a component of the fuel cells. A solid oxide fuel cell can include nanocrystalline cerium oxide as a cathode component and microcrystalline cerium oxide as an electrolyte component, which can prevent mechanical failure and interdiffusion common in other fuel cells. A solid oxide fuel cell can also include nanocrystalline cerium oxide in the anode. A PEM fuel cell can include cerium oxide as a catalyst support in the cathode and optionally also in the anode.

Electromechanical response of silk fibroin hydrogel and conductive polycarbazole/silk fibroin hydrogel composites as actuator material.

PubMed

Srisawasdi, Thanida; Petcharoen, Karat; Sirivat, Anuvat; Jamieson, Alexander M

2015-11-01

Pure silk fibroin (SF) hydrogel and polycarbazole/silk fibroin (SF/PCZ) hydrogels were fabricated by solvent casting technique to evaluate electromechanical responses, dielectric properties, and cantilever deflection properties as functions of electric field strength, SF concentration, glutaraldehyde concentration, and PCZ concentration in the blends. Electromechanical properties were characterized in oscillatory shear mode at electric field strengths ranging from 0 to 600V/mm and at a temperature of 27°C. For both the pristine SF and SF/PCZ hydrogels, the storage modulus response (ΔG') and the storage modulus sensitivity (ΔG'/G'0) increased dramatically with increasing electric field strength. The pristine hydrogel possessed the highest storage modulus sensitivity value of 5.87, a relatively high value when compared with other previously studied electroactive polymers. With the addition of conductive PCZ in SF hydrogel, the storage modulus sensitivity and the relative dielectric constant decreased; the conductive polymer thus provided the softening effect under electric field. In the deflection response, the dielectrophoresis force and deflection distance increased monotonically with electric field strength, where the pure SF hydrogel showed the highest deflection distance and dielectrophoresis force. Copyright © 2015 Elsevier B.V. All rights reserved.

Photocrosslinked Tyramine-Substituted Hyaluronate Hydrogels with Tunable Mechanical Properties Improve Immediate Tissue‐Hydrogel Interfacial Strength in Articular Cartilage

PubMed Central

Donnelly, Patrick E.; Chen, Tony; Finch, Anthony; Brial, Caroline; Maher, Suzanne A.; Torzilli, Peter A.

2017-01-01

Articular cartilage lacks the ability to self-repair and a permanent solution for cartilage repair remains elusive. Hydrogel implantation is a promising technique for cartilage repair; however for the technique to be successful hydrogels must interface with the surrounding tissue. The objective of this study was to investigate the tunability of mechanical properties in a hydrogel system using a phenol-substituted polymer, tyramine-substituted hyaluronate (TA-HA), and to determine if the hydrogels could form an interface with cartilage. We hypothesized that tyramine moieties on hyaluronate could crosslink to aromatic amino acids in the cartilage extracellular matrix. Ultraviolet (UV) light and a riboflavin photosensitizer were used to create a hydrogel by tyramine self‐crosslinking. The gel mechanical properties were tuned by varying riboflavin concentration, TA-HA concentration, and UV exposure time. Hydrogels formed with a minimum of 2.5 min of UV exposure. The compressive modulus varied from 5–16 kPa. Fluorescence spectroscopy analysis found differences in dityramine content. Cyanine-3 labelled tyramide reactivity at the surface of cartilage was dependent on the presence of riboflavin and UV exposure time. Hydrogels fabricated within articular cartilage defects had increasing peak interfacial shear stress at the cartilage-hydrogel interface with increasing UV exposure time, reaching a maximum shear stress 3.5× greater than a press‐fit control. Our results found that phenol-substituted polymer/riboflavin systems can be used to fabricate hydrogels with tunable mechanical properties and can interface with the surface tissue, such as articular cartilage. PMID:28134036

Phase-separation induced extraordinary toughening of magnetic hydrogels

NASA Astrophysics Data System (ADS)

Tang, Jingda; Li, Chenghai; Li, Haomin; Lv, Zengyao; Sheng, Hao; Lu, Tongqing; Wang, T. J.

2018-05-01

Phase separation markedly influences the physical properties of hydrogels. Here, we find that poly (N, N-dimethylacrylamide) (PDMA) hydrogels suffer from phase separation in aqueous sodium hydroxide solutions when the concentration is higher than 2 M. The polymer volume fraction and mechanical properties show an abrupt change around the transition point. We utilize this phase separation mechanism to synthesize tough magnetic PDMA hydrogels with the in-situ precipitation method. For comparison, we also prepared magnetic poly (2-acrylamido-2-methyl-propane sulfonic acid sodium) (PNaAMPS) magnetic hydrogels, where no phase separation occurs. The phase-separated magnetic PDMA hydrogels exhibit an extraordinarily high toughness of ˜1000 J m-2; while non-phase-separated magnetic PNaAMPS hydrogels only show a toughness of ˜1 J m-2, three orders of magnitude lower than that of PDMA hydrogels. This phase separation mechanism may become a new approach to prepare tough magnetic hydrogels and inspire more applications.

Hydrogels for Hydrophobic Drug Delivery. Classification, Synthesis and Applications

PubMed Central

Stewart, Sarah; Ervine, Michael; Al-Kasasbeh, Rehan; Donnelly, Ryan F.

2018-01-01

Hydrogels have been shown to be very useful in the field of drug delivery due to their high biocompatibility and ability to sustain delivery. Therefore, the tuning of their properties should be the focus of study to optimise their potential. Hydrogels have been generally limited to the delivery of hydrophilic drugs. However, as many of the new drugs coming to market are hydrophobic in nature, new approaches for integrating hydrophobic drugs into hydrogels should be developed. This article discusses the possible new ways to incorporate hydrophobic drugs within hydrogel structures that have been developed through research. This review describes hydrogel-based systems for hydrophobic compound delivery included in the literature. The section covers all the main types of hydrogels, including physical hydrogels and chemical hydrogels. Additionally, reported applications of these hydrogels are described in the subsequent sections. PMID:29364833

Fatigue stress concentration and notch sensitivity in nanocrystalline metals

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

Furnish, Timothy A.; Boyce, Brad L.; Sharon, John A.

Recent studies have shown the potential for nanocrystalline metals to possess excellent fatigue resistance compared to their coarse-grained counterparts. Although the mechanical properties of nanocrystalline metals are believed to be particularly susceptible to material defects, a systematic study of the effects of geometric discontinuities on their fatigue performance has not yet been performed. In the present work, nanocrystalline Ni–40 wt%Fe containing both intrinsic and extrinsic defects were tested in tension–tension fatigue. The defects were found to dramatically reduce the fatigue resistance, which was attributed to the relatively high notch sensitivity in the nanocrystalline material. Microstructural analysis within the crack-initiation zonesmore » underneath the defects revealed cyclically-induced abnormal grain growth (AGG) as a predominant deformation and crack initiation mechanism during high-cycle fatigue. Furthermore, the onset of AGG and the ensuing fracture is likely accelerated by the stress concentrations, resulting in the reduced fatigue resistance compared to the relatively defect-free counterparts.« less

Fatigue stress concentration and notch sensitivity in nanocrystalline metals

DOE PAGES

Furnish, Timothy A.; Boyce, Brad L.; Sharon, John A.; ...

2016-03-11

Recent studies have shown the potential for nanocrystalline metals to possess excellent fatigue resistance compared to their coarse-grained counterparts. Although the mechanical properties of nanocrystalline metals are believed to be particularly susceptible to material defects, a systematic study of the effects of geometric discontinuities on their fatigue performance has not yet been performed. In the present work, nanocrystalline Ni–40 wt%Fe containing both intrinsic and extrinsic defects were tested in tension–tension fatigue. The defects were found to dramatically reduce the fatigue resistance, which was attributed to the relatively high notch sensitivity in the nanocrystalline material. Microstructural analysis within the crack-initiation zonesmore » underneath the defects revealed cyclically-induced abnormal grain growth (AGG) as a predominant deformation and crack initiation mechanism during high-cycle fatigue. Furthermore, the onset of AGG and the ensuing fracture is likely accelerated by the stress concentrations, resulting in the reduced fatigue resistance compared to the relatively defect-free counterparts.« less

Hydrogels for Engineering of Perfusable Vascular Networks

PubMed Central

Liu, Juan; Zheng, Huaiyuan; Poh, Patrina S. P.; Machens, Hans-Günther; Schilling, Arndt F.

2015-01-01

Hydrogels are commonly used biomaterials for tissue engineering. With their high-water content, good biocompatibility and biodegradability they resemble the natural extracellular environment and have been widely used as scaffolds for 3D cell culture and studies of cell biology. The possible size of such hydrogel constructs with embedded cells is limited by the cellular demand for oxygen and nutrients. For the fabrication of large and complex tissue constructs, vascular structures become necessary within the hydrogels to supply the encapsulated cells. In this review, we discuss the types of hydrogels that are currently used for the fabrication of constructs with embedded vascular networks, the key properties of hydrogels needed for this purpose and current techniques to engineer perfusable vascular structures into these hydrogels. We then discuss directions for future research aimed at engineering of vascularized tissue for implantation. PMID:26184185

Highly stretchable HA/SA hydrogels for tissue engineering.

PubMed

Zhu, Chengcheng; Yang, Rui; Hua, Xiaobin; Chen, Hong; Xu, Jumei; Wu, Rile; Cen, Lian

2018-04-01

A highly stretchable hyaluronic acid (HA)/sodium alginate (SA) hydrogel was developed in this study based on an interpenetrating polymer network. HA/SA hydrogels were prepared by mixing two polysaccharides followed by covalent crosslinking via epoxy groups on HA molecules and ionic crosslinking via divalent ions on SA chains sequentially. The effect of HA/SA ratio on the pore size and distribution, swelling ratio, elongation and rheological properties as well as protein loading and release properties of HA/SA hydrogels was explored. Moreover, a surface modification method, layer-by-layer (LBL) assembly technique, was applied to modify the hydrogel to evaluate the hydrogel's tenability in varying biological performance. It was then shown that the hydrogels had the pore sizes ranging from 100 to 50 μm. With the increase in SA content of the resulting hydrogels, the pore size, swelling ratio, and storage modulus (G') and loss modulus (G″) of the hydrogel all decreased, whereas the in vitro bulk weight loss was fastened. Moreover, elongation at break (EB) value increased first, reached a peak value and then decreased, that is HA8/SA1 (HA:SA = 8:1) had the highest EB value of 417%. This hydrogel could retain 33.2% of the pre-loaded protein even after 72 h, which could be further attenuated when LBL was used to shell the hydrogel. The growth of fibroblasts on HA8/SA1 hydrogel gave preliminary assessment on its suitability as a cellular carrier, while the LBL modified HA8/SA1 hydrogel also favored the anchoring of keratinocytes, further enhancing its cell carrier role for tissue regeneration, especially skin engineering.

On the Interaction between Superabsorbent Hydrogels and Cementitious Materials

NASA Astrophysics Data System (ADS)

Farzanian, Khashayar

Autogenous shrinkage induced cracking is a major concern in high performance concretes (HPC), which are produced with low water to cement ratios. Internal curing to maintain high relative humidity in HPC with the use of an internal water reservoir has proven effective in mitigating autogenous shrinkage in HPC. Superabsorbent polymers (SAP) or hydrogels have received increasing attention as an internal curing agent in recent years. A key advantage of SAP is its versatility in size distribution and absorption/desorption characteristics, which allow it to be adapted to specific mix designs. Understanding the behavior of superabsorbent hydrogels in cementitious materials is critical for accurate design of internal curing. The primary goal of this study is to fundamentally understand the interaction between superabsorbent hydrogels and cementitious materials. In the first step, the effect of chemical and mechanical conditions on the absorption of hydrogels is investigated. In the second step, the desorption of hydrogels in contact with porous cementitious materials is examined to aid in understanding the mechanisms of water release from superabsorbent hydrogels (SAP) into cementitious materials. The dependence of hydrogel desorption on the microstructure of cementitious materials and relative humidity is studied. It is shown that the capillary forces developed at the interface between the hydrogel and cementitious materials increased the desorption of the hydrogels. The size of hydrogels is shown to influence desorption, beyond the known size dependence of bulk diffusion, through debonding from the cementitious matrix, thereby decreasing the effect of the Laplace pressure on desorption. In the third step, the desorption of hydrogels synthesized with varied chemical compositions in cementitious materials are investigated. The absorption, chemical structure and mechanical response of hydrogels swollen in a cement mixture are studied. The effect of the capillary forces on

Cytotoxic evaluation of hydroxyapatite-filled and silica/hydroxyapatite-filled acrylate-based restorative composite resins: An in vitro study.

PubMed

Chadda, Harshita; Naveen, Sangeetha Vasudevaraj; Mohan, Saktiswaren; Satapathy, Bhabani K; Ray, Alok R; Kamarul, Tunku

2016-07-01

Although the physical and mechanical properties of hydroxyapatite-filled dental restorative composite resins have been examined, the biocompatibility of these materials has not been studied in detail. The purpose of this in vitro study was to analyze the toxicity of acrylate-based restorative composite resins filled with hydroxyapatite and a silica/hydroxyapatite combination. Five different restorative materials based on bisphenol A-glycidyl methacrylate (bis-GMA) and tri-ethylene glycol dimethacrylate (TEGDMA) were developed: unfilled (H0), hydroxyapatite-filled (H30, H50), and silica/hydroxyapatite-filled (SH30, SH50) composite resins. These were tested for in vitro cytotoxicity by using human bone marrow mesenchymal stromal cells. Surface morphology, elemental composition, and functional groups were determined by scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDX), and Fourier-transformed infrared spectroscopy (FTIR). The spectra normalization, baseline corrections, and peak integration were carried out by OPUS v4.0 software. Both in vitro cytotoxicity results and SEM analysis indicated that the composite resins developed were nontoxic and supported cell adherence. Elemental analysis with EDX revealed the presence of carbon, oxygen, calcium, silicon, and gold, while the presence of methacrylate, hydroxyl, and methylene functional groups was confirmed through FTIR analysis. The characterization and compatibility studies showed that these hydroxyapatite-filled and silica/hydroxyapatite-filled bis-GMA/TEGDMA-based restorative composite resins are nontoxic to human bone marrow mesenchymal stromal cells and show a favorable biologic response, making them potential biomaterials. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

[Chitosan-collagen polymer induced remineralization of tooth hard tissue through self-growing methods].

PubMed

Xun, Ren; Jing, Yao; Qin, Du; Chuhang, Liao; Kun, Tian

2014-10-01

To modify biomacromolecules, such as chitosan and collagen, to synthesize a mineralized template that will induce self-growing remineralization of tooth enamel. Natural polycation polysaccharide chitosan was modified through phosphorylation to synthesize the polyanion derivative ofphosphorylated chitosan. Parent hydrogels com- bined with chitosan and collagen I were built through peptide binding reaction using genipin as a crosslinker. The gels self- assembled on the tooth's inert surface, which was stimulated by ultraviolet radiation. The bionic saliva provided mineralized ion, and then the hydroxyapatite assembled and grew in situ on the tooth. The functional group P04(3-) (3,446 cm(-1)) was grafted on chitosan as confirmed by the Fourier transform infrared spectroscopy. The porous polyelectrolyte complex hydrogel formed by the interaction between the polycation chitosan and the polyanion phosphorylated chitosan could induce hydroxyapatite crystal nucleation and growth on the hydrogel fiber surfaces. The neonatal crystal was hydroxyapatite as confirmed by X-ray diffraction and was tightly connected to the tooth. A continuous structure of column crystals with sizes ranging from 30 nm to 60 nm was observed. The structure was in parallel direction similar to the direction of the enamel rod, and its hardness was close to dentin. The parent hydrogels that were easily obtained and controlled could mimic the template of the enamel mineralization and induce a self-growing hydroxyapatite, which is an important step in the structural bionics of enamel.

Simple route for nano-hydroxyapatite properties expansion.

PubMed

Rojas, L; Olmedo, H; García-Piñeres, A J; Silveira, C; Tasic, L; Fraga, F; Montero, M L

2015-10-20

Simple surface modification of nano-hydroxyapatite, through acid-basic reactions, allows expanding the properties of this material. Introduction of organic groups such as hydrophobic alkyl chains, carboxylic acid, and amide or amine basic groups on the hydroxyapatite surface systematically change the polarity, surface area, and reactivity of hydroxyapatite without modifying its phase. Physical and chemical properties of the new derivative particles were analyzed. The biocompatibility of modified Nano-Hap on Raw 264.7 cells was also assessed.

Reversible Polymer Hydrogels

DTIC Science & Technology

2008-12-01

glucosamine hydrochloride was dissolved in 100 mL of de- ionized water and placed in an ice bath at >5oC and purged with N2 gas for 20 minutes; 3.25...Temperature sensitive hydrogels based on N-isopropyl acrylamide (NIPA) and acryloyl glucosamine (AG) were synthesized using ammonium persulfate (APS) as...hydrogels by copolymerization of poly (N-isopropylacrylamide) (NIPA), and acryloyl glucosamine (AG) a derivative of chi- tosan, a biopolymer from

Development of hydroxyapatite derived from Indian coral.

PubMed

Sivakumar, M; Kumar, T S; Shantha, K L; Rao, K P

1996-09-01

A simple method of converting the calcium carbonate skeleton of the corals available in the Indian coast into hydroxyapatite granules has been developed. By heating the coral to 900 degrees C, the organic materials were eliminated. Powder X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) were employed to characterize the coral and to optimize the processing parameters as well as to confirm the hydroxyapatite formation. The coral used exhibits the presence of both aragonite and calcite phases (dimorphism). At a temperature of 900 degrees C the coral was found to decompose all the carbonate phases. The pre-heated coral is converted into hydroxyapatite by a chemical exchange reaction with di-ammonium phosphate under hydrothermal conditions. The hydroxyapatite obtained was in powder form and does not contain any impurities. The in vitro solubility test of the apatite granules performed in Gomoris, Michalelis, Sorensens, Ringer's and phosphate buffer of pH 7.2 and de-ionized water indicated the stability of the coralline hydroxyapatite.

Synthesis and Characterization of Hydroxyapatite Powder by Wet Precipitation Method

NASA Astrophysics Data System (ADS)

Cahyaningrum, S. E.; Herdyastuty, N.; Devina, B.; Supangat, D.

2018-01-01

Hydroxyapatite is main inorganic component of the bone with formula Ca10(PO4)6(OH)2. Hydroxyapatite can be used as substituted bone biomaterial because biocompatible, non toxic, and osteoconductive. In this study, hydroxyapatite is synthesized using wet precipitation method from egg shell. The product was sintered at different temperatures of 800°C to 1000°C to improve its crystallinity. The hydroxyapatite was characterized by X-ray analysis, Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR) to reveal its phase content, morphology and types of bond present within it. The analytical results showed hydroxyapatite had range in crystallinity from 85.527 to 98.753%. The analytical functional groups showed that presence of functional groups such as OH, (PO4)3 2-, and CO3 2- that indicated as hydroxyapatite. The result of characterization SEM indicated that hydroxyapatite without sintering and HAp sintering at 800 °C were irregular shape without pore. The best hydroxyapatite with temperature sintering at 900 °C showed oval shaped with pores without agglomerated.

Encoding Hydrogel Mechanics via Network Cross-Linking Structure.

PubMed

Schweller, Ryan M; West, Jennifer L

2015-05-11

The effects of mechanical cues on cell behaviors in 3D remain difficult to characterize as the ability to tune hydrogel mechanics often requires changes in the polymer density, potentially altering the material's biochemical and physical characteristics. Additionally, with most PEG diacrylate (PEGDA) hydrogels, forming materials with compressive moduli less than ∼10 kPa has been virtually impossible. Here, we present a new method of controlling the mechanical properties of PEGDA hydrogels independent of polymer chain density through the incorporation of additional vinyl group moieties that interfere with the cross-linking of the network. This modification can tune hydrogel mechanics in a concentration dependent manner from <1 to 17 kPa, a more physiologically relevant range than previously possible with PEG-based hydrogels, without altering the hydrogel's degradation and permeability. Across this range of mechanical properties, endothelial cells (ECs) encapsulated within MMP-2/MMP-9 degradable hydrogels with RGDS adhesive peptides revealed increased cell spreading as hydrogel stiffness decreased in contrast to behavior typically observed for cells on 2D surfaces. EC-pericyte cocultures exhibited vessel-like networks within 3 days in highly compliant hydrogels as compared to a week in stiffer hydrogels. These vessel networks persisted for at least 4 weeks and deposited laminin and collagen IV perivascularly. These results indicate that EC morphogenesis can be regulated using mechanical cues in 3D. Furthermore, controlling hydrogel compliance independent of density allows for the attainment of highly compliant mechanical regimes in materials that can act as customizable cell microenvironments.

Hybrid hydrogels produced by ionizing radiation technique

NASA Astrophysics Data System (ADS)

Oliveira, M. J. A.; Amato, V. S.; Lugão, A. B.; Parra, D. F.

2012-09-01

The interest in biocompatible hydrogels with particular properties has increased considerably in recent years due to their versatile applications in biomedicine, biotechnology, pharmacy, agriculture and controlled release of drugs. The use of hydrogels matrices for particular drug-release applications has been investigated with the synthesis of modified polymeric hydrogel of PVAl and 0.5, 1.0, 1.5% nano-clay. They were processed using gamma radiation from Cobalt-60 source at 25 kGy dose. The characterization of the hydrogels was conducted and toxicity was evaluated. The dried hydrogel was analyzed for thermogravimetry analysis (TGA), infrared spectroscopy (FTIR) and swelling in solutions of different pH. The membranes have no toxicity. The nano-clay influences directly the equilibrium swelling.

Tough bonding of hydrogels to diverse non-porous surfaces

NASA Astrophysics Data System (ADS)

Yuk, Hyunwoo; Zhang, Teng; Lin, Shaoting; Parada, German Alberto; Zhao, Xuanhe

2016-02-01

In many animals, the bonding of tendon and cartilage to bone is extremely tough (for example, interfacial toughness ~800 J m-2 refs ,), yet such tough interfaces have not been achieved between synthetic hydrogels and non-porous surfaces of engineered solids. Here, we report a strategy to design tough transparent and conductive bonding of synthetic hydrogels containing 90% water to non-porous surfaces of diverse solids, including glass, silicon, ceramics, titanium and aluminium. The design strategy is to anchor the long-chain polymer networks of tough hydrogels covalently to non-porous solid surfaces, which can be achieved by the silanation of such surfaces. Compared with physical interactions, the chemical anchorage results in a higher intrinsic work of adhesion and in significant energy dissipation of bulk hydrogel during detachment, which lead to interfacial toughness values over 1,000 J m-2. We also demonstrate applications of robust hydrogel-solid hybrids, including hydrogel superglues, mechanically protective hydrogel coatings, hydrogel joints for robotic structures and robust hydrogel-metal conductors.

Multi-scale Multi-mechanism Toughening of Hydrogels

NASA Astrophysics Data System (ADS)

Zhao, Xuanhe

Hydrogels are widely used as scaffolds for tissue engineering, vehicles for drug delivery, actuators for optics and fluidics, and model extracellular matrices for biological studies. The scope of hydrogel applications, however, is often severely limited by their mechanical properties. Inspired by the mechanics and hierarchical structures of tough biological tissues, we propose that a general principle for the design of tough hydrogels is to implement two mechanisms for dissipating mechanical energy and maintaining high elasticity in hydrogels. A particularly promising strategy for the design is to integrate multiple pairs of mechanisms across multiple length scales into a hydrogel. We develop a multiscale theoretical framework to quantitatively guide the design of tough hydrogels. On the network level, we have developed micro-physical models to characterize the evolution of polymer networks under deformation. On the continuum level, we have implemented constitutive laws formulated from the network-level models into a coupled cohesive-zone and Mullins-effect model to quantitatively predict crack propagation and fracture toughness of hydrogels. Guided by the design principle and quantitative model, we will demonstrate a set of new hydrogels, based on diverse types of polymers, yet can achieve extremely high toughness superior to their natural counterparts such as cartilages. The work was supported by NSF(No. CMMI- 1253495) and ONR (No. N00014-14-1-0528).

Establishment of a Physical Model for Solute Diffusion in Hydrogel: Understanding the Diffusion of Proteins in Poly(sulfobetaine methacrylate) Hydrogel.

PubMed

Zhou, Yuhang; Li, Junjie; Zhang, Ying; Dong, Dianyu; Zhang, Ershuai; Ji, Feng; Qin, Zhihui; Yang, Jun; Yao, Fanglian

2017-02-02

Prediction of the diffusion coefficient of solute, especially bioactive molecules, in hydrogel is significant in the biomedical field. Considering the randomness of solute movement in a hydrogel network, a physical diffusion RMP-1 model based on obstruction theory was established in this study. The physical properties of the solute and the polymer chain and their interactions were introduced into this model. Furthermore, models RMP-2 and RMP-3 were established to understand and predict the diffusion behaviors of proteins in hydrogel. In addition, zwitterionic poly(sulfobetaine methacrylate) (PSBMA) hydrogels with wide range and fine adjustable mesh sizes were prepared and used as efficient experimental platforms for model validation. The Flory characteristic ratios, Flory-Huggins parameter, mesh size, and polymer chain radii of PSBMA hydrogels were determined. The diffusion coefficients of the proteins (bovine serum albumin, immunoglobulin G, and lysozyme) in PSBMA hydrogels were studied by the fluorescence recovery after photobleaching technique. The measured diffusion coefficients were compared with the predictions of obstruction models, and it was found that our model presented an excellent predictive ability. Furthermore, the assessment of our model revealed that protein diffusion in PSBMA hydrogel would be affected by the physical properties of the protein and the PSBMA network. It was also confirmed that the diffusion behaviors of protein in zwitterionic hydrogels can be adjusted by changing the cross-linking density of the hydrogel and the ionic strength of the swelling medium. Our model is expected to possess accurate predictive ability for the diffusion coefficient of solute in hydrogel, which will be widely used in the biomedical field.

Biodegradable HEMA-based hydrogels with enhanced mechanical properties.

PubMed

Moghadam, Mohamadreza Nassajian; Pioletti, Dominique P

2016-08-01

Hydrogels are widely used in the biomedical field. Their main purposes are either to deliver biological active agents or to temporarily fill a defect until they degrade and are followed by new host tissue formation. However, for this latter application, biodegradable hydrogels are usually not capable to sustain any significant load. The development of biodegradable hydrogels presenting load-bearing capabilities would open new possibilities to utilize this class of material in the biomedical field. In this work, an original formulation of biodegradable photo-crosslinked hydrogels based on hydroxyethyl methacrylate (HEMA) is presented. The hydrogels consist of short-length poly(2-hydroxyethyl methacrylate) (PHEMA) chains in a star shape structure, obtained by introducing a tetra-functional chain transfer agent in the backbone of the hydrogels. They are cross-linked with a biodegradable N,O-dimethacryloyl hydroxylamine (DMHA) molecule sensitive to hydrolytic cleavage. We characterized the degradation properties of these hydrogels submitted to mechanical loadings. We showed that the developed hydrogels undergo long-term degradation and specially meet the two essential requirements of a biodegradable hydrogel suitable for load bearing applications: enhanced mechanical properties and low molecular weight degradation products. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1161-1169, 2016. © 2015 Wiley Periodicals, Inc.

Some aspects of pulsed laser deposition of Si nanocrystalline films

NASA Astrophysics Data System (ADS)

Polyakov, B.; Petruhins, A.; Butikova, J.; Kuzmin, A.; Tale, I.

2009-11-01

Nanocrystalline silicon films were deposited by a picosecond laser ablation on different substrates in vacuum at room temperature. A nanocrystalline structure of the films was evidenced by atomic force microscopy (AFM), optical and Raman spectroscopies. A blue shift of the absorption edge was observed in optical absorption spectra, and a decrease of the optical phonon energy at the Brillouin zone centre was detected by Raman scattering. Early stages of nanocrystalline film formation on mica and HOPG substrates were studied by AFM. Mechanism of nanocrystal growth on substrate is discussed. in here

Injectable Solid Peptide Hydrogel as Cell Carrier: Effects of Shear Flow on Hydrogel and Cell Payload

PubMed Central

Yan, Congqi; Mackay, Michael E.; Czymmek, Kirk; Nagarkar, Radhika P.; Schneider, Joel P.; Pochan, Darrin J.

2012-01-01

β-hairpin peptide-based hydrogels are a class of injectable solid hydrogels that can deliver encapsulated cells or molecular therapies to a target site via syringe or catheter injection as a carrier material. These physical hydrogels can shear-thin and consequently flow as a low-viscosity material under a sufficient shear stress but immediately recover back into a solid upon removal of the stress, allowing them to be injected as preformed gel solids. Hydrogel behavior during flow was studied in a cylindrical capillary geometry that mimicked the actual situation of injection through a syringe needle in order to quantify effects of shear-thin injection delivery on hydrogel flow behavior and encapsulated cell payloads. It was observed that all β-hairpin peptide hydrogels investigated displayed a promising flow profile for injectable cell delivery: a central wide plug flow region where gel material and cell payloads experienced little or no shear rate and a narrow shear zone close to the capillary wall where gel and cells were subject to shear deformation. The width of the plug flow region was found to be weakly dependent on hydrogel rigidity and flow rate. Live-dead assays were performed on encapsulated MG63 cells three hours after injection flow and revealed that shear-thin delivery through the capillary had little impact on cell viability and the spatial distribution of encapsulated cell payloads. These observations help us to fundamentally understand how the gels flow during injection through a thin catheter and how they immediately restore mechanically and morphologically relative to pre-flow, static gels. PMID:22390812

Electrodeposition of Nanocrystalline Co-P Coatings as a Hard Chrome Alternative

DTIC Science & Technology

2009-09-02

Electrodeposition  of Nanocrystalline Co‐P  Coatings as a Hard Chrome Alternative Report Documentation Page Form ApprovedOMB No. 0704-0188 Public reporting burden...AND SUBTITLE Electrodeposition of Nanocrystalline Co‐P Coatings as a Hard Chrome Alternative 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c...Defense Conference – 2 September 2009 Conventional  Electrodeposits Polycrystalline (10‐100 µm) Electrodeposited Nanocrystalline Materials Pulsed

Structural, optical and magnetic behaviour of nanocrystalline Volborthite

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

Arvind, Hemant K., E-mail: hemantarvind@gmail.com; Kumar, Sudhish, E-mail: skmlsu@gmail.com; Kalal, Sangeeta

2016-05-06

Nanocrystalline sample of Volborthite (Copper Pyrovanadate: Cu{sub 3}V{sub 2} (OH){sub 2}O{sub 7}.2H{sub 2}O) has been synthesized using wet chemical route and characterized by XRD, SEM, FTIR, UV-Vis-NIR spectroscopic and magnetization measurements. Room temperature X-ray diffraction analysis confirms the single phase monoclinic structure and nanocrystalline nature of Volborthite. The UV-Visible optical absorption spectrum displays two broad absorption peaks in the range of 200-350 nm and 400-1000 nm. The direct band gap is found to be E{sub g}= ∼2.74 eV. Bulk Volborthite was reported to be a natural frustrated antiferromagnet, however our nanocrystalline Volborthite display week ferromagnetic hysteresis loop with very small coercivity andmore » retentivity at room temperature.« less

Development of injectable hydrogels for nucleus pulposus replacement

NASA Astrophysics Data System (ADS)

Thomas, Jonathan D.

Intervertebral disc degeneration has been reported as the underlying cause for 75% of cases of lower back pain and is marked by dehydration of the nucleus pulposus within the intervertebral disc. There have been many implant designs to replace the nucleus pulposus. Some researchers have proposed the replacement of the nucleus pulposus with hydrogel materials. The insertion of devices made from these materials further compromises the annulus of the disc. An ideal nucleus replacement could be injected into the disc space and form a solid in vivo. However, injectable replacements using curing elastomers and thermoplastic materials are not ideal because of the potentially harmful exothermic heat evolved from their reactions and the toxicity of the reactants used. We propose a hydrogel system that can be injected as a liquid at 25°C and solidified to yield a hydrogel within the intervertebral disc at 37°C. In aqueous solutions, these polymers have Lower Critical Solution Temperatures (LCST) between 25-37°C, making them unique candidate materials for this application. Poly(N-isopropylacrylamide) (PNIPAAm) is the most widely studied LCST polymer due to its drastic transition near body temperature. However, by itself, pure PNIPAAm forms a hydrogel that has low water content and can readily undergo plastic deformation. To increase the water content and impart elasticity to PNIPAAm hydrogels, grafted and branched hydrogel systems were created that incorporated the thermogelling PNIPAAm and hydrophilic poly(ethylene glycol) (PEG). In this research, the effects of polymer composition and monomer to initiator ratio, which controls polymer MW, on the in vitro swelling properties (mass, chemical, and compressive mechanical stability) of hydrogels formed from aqueous solutions of these polymers were evaluated. Immersion studies were also conducted in solutions to simulate the osmotic environment of the nucleus pulposus. The effects of repeated compression and unloading cycles

Programmable DNA Hydrogels Assembled from Multidomain DNA Strands.

PubMed

Jiang, Huiling; Pan, Victor; Vivek, Skanda; Weeks, Eric R; Ke, Yonggang

2016-06-16

Hydrogels are important in biological and medical applications, such as drug delivery and tissue engineering. DNA hydrogels have attracted significant attention due to the programmability and biocompatibility of the material. We developed a series of low-cost one-strand DNA hydrogels self-assembled from single-stranded DNA monomers containing multiple palindromic domains. This new hydrogel design is simple and programmable. Thermal stability, mechanical properties, and loading capacity of these one-strand DNA hydrogels can be readily regulated by simply adjusting the DNA domains. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Poly(ethylene glycol) hydrogel microstructures encapsulating living cells

NASA Technical Reports Server (NTRS)

Koh, Won-Gun; Revzin, Alexander; Pishko, Michael V.

2002-01-01

We present an easy and effective method for the encapsulation of cells inside PEG-based hydrogel microstructures fabricated using photolithography. High-density arrays of three-dimensional microstructures were created on substrates using this method. Mammalian cells were encapsulated in cylindrical hydrogel microstructures of 600 and 50 micrometers in diameter or in cubic hydrogel structures in microfluidic channels. Reducing lateral dimension of the individual hydrogel microstructure to 50 micrometers allowed us to isolate 1-3 cells per microstructure. Viability assays demonstrated that cells remained viable inside these hydrogels after encapsulation for up to 7 days.

Stable environmentally sensitive cationic hydrogels for controlled delivery applications.

PubMed

Deo, Namita; Ruetsch, S; Ramaprasad, K R; Kamath, Y

2010-01-01

New thermosensitive, cationic hydrogels were synthesized by the dispersion copolymerization of N-isopropylacrylamide (NIPAM) and (3-acrylamidopropyl)trimethylammonium chloride (AAPTAC). In the polymerization protocol, an amide-based comonomer, (3-acrylamidopropyl)trimethylammonium chloride, was reacted as a new alternative monomer for introducing positive charges into the thermosensitive hydrogel. The hydrogels were synthesized without making any pH adjustment in the aqueous medium. These hydrogel particles exhibited colloidal stability in the pH range of 1.5 to 11.0, while similar cationic hydrogels were reported to be unstable at pHs higher than 6. The stronger cationic character of the selected comonomer provided higher colloidal stability to the poly(NIPAM-co-AAPTAC) hydrogels. Furthermore, these hydrogels displayed sensitivity towards temperature, pH, and salt concentration. Interestingly, the particle size of hydrogels was found to be decreased significantly with an increase in temperature and salt concentration. In addition, using pyrene fluorescence spectroscopy, it was established that the hydrophobicity/hydrophilicity of the hydrogel particles was largely controlled by both pH and temperature. The thermosensitive hydrogels reported in this paper may be suitable for delivering different actives for cosmetic and medical applications. Although direct application of these hydrogel particles in cosmetics has not been shown at this stage, the methodology of making them and controlling their absorption and release properties as a function of temperature and pH has been demonstrated. Furthermore, these hydrogels may also have applications in scavenging organic and inorganic toxics.

Polymer-induced compression of biological hydrogels

NASA Astrophysics Data System (ADS)

Datta, Sujit; Preska Steinberg, Asher; Ismagilov, Rustem

Hydrogels - such as mucus, blood clots, and the extracellular matrix - provide critical functions in biological systems. However, little is known about how their structure is influenced by many of the polymeric materials they come into contact with regularly. Here, we focus on one critically important biological hydrogel: colonic mucus. While several biological processes are thought to potentially regulate the mucus hydrogel structure, the polymeric composition of the gut environment has been ignored. We use Flory-Huggins solution theory to characterize polymer-mucus interactions. We find that gut polymers, including those small enough to penetrate the mucus hydrogel, can in fact alter mucus structure, changing its equilibrium degree of swelling and forcing it to compress. The extent of compression increases with increasing polymer concentration and size. We use experiments on mice to verify these predictions with common dietary and therapeutic gut polymers. Our results provide a foundation for investigating similar, previously overlooked, polymer-induced effects in other biological hydrogels.

Design properties of hydrogel tissue-engineering scaffolds

PubMed Central

Zhu, Junmin; Marchant, Roger E

2011-01-01

This article summarizes the recent progress in the design and synthesis of hydrogels as tissue-engineering scaffolds. Hydrogels are attractive scaffolding materials owing to their highly swollen network structure, ability to encapsulate cells and bioactive molecules, and efficient mass transfer. Various polymers, including natural, synthetic and natural/synthetic hybrid polymers, have been used to make hydrogels via chemical or physical crosslinking. Recently, bioactive synthetic hydrogels have emerged as promising scaffolds because they can provide molecularly tailored biofunctions and adjustable mechanical properties, as well as an extracellular matrix-like microenvironment for cell growth and tissue formation. This article addresses various strategies that have been explored to design synthetic hydrogels with extracellular matrix-mimetic bioactive properties, such as cell adhesion, proteolytic degradation and growth factor-binding. PMID:22026626

[Raman studies of nanocrystalline BaTiO3 ceramics].

PubMed

Xiao, Chang-jiang; Jin, Chang-qing; Wang, Xiao-hui

2008-12-01

High pressure can significantly increase the densification. Further, during the high pressure assisted sintering, the nucleation rate is increased due to reduced energy barrier and the growth rate is suppressed due to the decreased diffusivity. Thus high pressure enables the specimen to be fabricated with relatively lower temperature and shorter sintering period that assures to obtain dense nanocrystalline ceramics. Dense nanocrystalline BaTiO3 ceramics with uniform grain sizes of 60 and 30 nm, respectively, were obtained by pressure assisted sintering. The crystal structure and phase transitions were investigated by Raman scattering at temperatures ranging from -190 to 200 degrees C. The Raman results indicated that the evolution of Raman spectrum with grain size is characterized by an intensity decrease, a broadening of the line width, a frequency shift, and the disappearance of the Raman mode. With increasing temperature, similar to 3 mm BaTiO3 normal ceramics, the successive phase transitions from rhombohedral to orthorhombic, orthorhombic to tetragonal, and tetragonal to cubic were also observed in nanocrystalline BaTiO3 ceramics. In addition, when particle size is reduced to the nanoscale, one will find some unusual physical properties in nanocrystalline ceramics, compared with those of coarse-grained BaTiO3 ceramics. The different coexistences of multiphase were found at different temperature. Especially, the ferroelectric tetragonal and orthorhombic phase can coexist at room temperature in nanocrystalline BaTiO3 ceramics. The phenomenon can be explained by the internal stress. The coexistences of different ferroelectric phases at room temperature indicate that the critical grain size for the disappearance of ferroelectricity in nanocrystalline BaTiO3 ceramics fabricated by pressure assisted sintering is below 30 nm.

Hydrogel scaffolds for tissue engineering: Progress and challenges

PubMed Central

El-Sherbiny, Ibrahim M.; Yacoub, Magdi H.

2013-01-01

Designing of biologically active scaffolds with optimal characteristics is one of the key factors for successful tissue engineering. Recently, hydrogels have received a considerable interest as leading candidates for engineered tissue scaffolds due to their unique compositional and structural similarities to the natural extracellular matrix, in addition to their desirable framework for cellular proliferation and survival. More recently, the ability to control the shape, porosity, surface morphology, and size of hydrogel scaffolds has created new opportunities to overcome various challenges in tissue engineering such as vascularization, tissue architecture and simultaneous seeding of multiple cells. This review provides an overview of the different types of hydrogels, the approaches that can be used to fabricate hydrogel matrices with specific features and the recent applications of hydrogels in tissue engineering. Special attention was given to the various design considerations for an efficient hydrogel scaffold in tissue engineering. Also, the challenges associated with the use of hydrogel scaffolds were described. PMID:24689032

Facile synthesis of degradable and electrically conductive polysaccharide hydrogels.

PubMed

Guo, Baolin; Finne-Wistrand, Anna; Albertsson, Ann-Christine

2011-07-11

Degradable and electrically conductive polysaccharide hydrogels (DECPHs) have been synthesized by functionalizing polysaccharide with conductive aniline oligomers. DECPHs based on chitosan (CS), aniline tetramer (AT), and glutaraldehyde were obtained by a facile one-pot reaction by using the amine group of CS and AT under mild conditions, which avoids the multistep reactions and tedious purification involved in the synthesis of degradable conductive hydrogels in our previous work. Interestingly, these one-pot hydrogels possess good film-forming properties, electrical conductivity, and a pH-sensitive swelling behavior. The chemical structure and morphology before and after swelling of the hydrogels were verified by FT-IR, NMR, and SEM. The conductivity of the hydrogels was tuned by adjusting the content of AT. The swelling ratio of the hydrogels was altered by the content of tetraaniline and cross-linker. The hydrogels underwent slow degradation in a buffer solution. The hydrogels obtained by this facile approach provide new possibilities in biomedical applications, for example, biodegradable conductive hydrogels, films, and scaffolds for cardiovascular tissue engineering and controlled drug delivery.

Development of hydrogels for regenerative engineering.

PubMed

Guan, Xiaofei; Avci-Adali, Meltem; Alarçin, Emine; Cheng, Hao; Kashaf, Sara Saheb; Li, Yuxiao; Chawla, Aditya; Jang, Hae Lin; Khademhosseini, Ali

2017-05-01

The aim of regenerative engineering is to restore complex tissues and biological systems through convergence in the fields of advanced biomaterials, stem cell science, and developmental biology. Hydrogels are one of the most attractive biomaterials for regenerative engineering, since they can be engineered into tissue mimetic 3D scaffolds to support cell growth due to their similarity to native extracellular matrix. Advanced nano- and micro-technologies have dramatically increased the ability to control properties and functionalities of hydrogel materials by facilitating biomimetic fabrication of more sophisticated compositions and architectures, thus extending our understanding of cell-matrix interactions at the nanoscale. With this perspective, this review discusses the most commonly used hydrogel materials and their fabrication strategies for regenerative engineering. We highlight the physical, chemical, and functional modulation of hydrogels to design and engineer biomimetic tissues based on recent achievements in nano- and micro-technologies. In addition, current hydrogel-based regenerative engineering strategies for treating multiple tissues, such as musculoskeletal, nervous and cardiac tissue, are also covered in this review. The interaction of multiple disciplines including materials science, cell biology, and chemistry, will further play an important role in the design of functional hydrogels for the regeneration of complex tissues. Copyright © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Free radical scavenging injectable hydrogels for regenerative therapy.

PubMed

Komeri, Remya; Thankam, Finosh Gnanaprakasam; Muthu, Jayabalan

2017-02-01

Pathological free radicals generated from inflamed and infarcted cardiac tissues interferes natural tissue repair mechanisms. Hypoxic microenvironment at the injured zone of non-regenerating cardiac tissues hinders the therapeutic attempts including cell therapy. Here we report an injectable, cytocompatible, free radical scavenging synthetic hydrogel formulation for regenerative therapy. New hydrogel (PEAX-P) is prepared with D-xylitol-co-fumarate-co-poly ethylene adipate-co-PEG comaromer (PEAX) and PEGDiacrylate. PEAX-P hydrogel swells 4.9 times the initial weight and retains 100.07kPa Young modulus at equilibrium swelling, which is suitable for cardiac applications. PEAX-P hydrogel retains elastic nature even at 60% compressive strain, which is favorable to fit with the dynamic and elastic natural tissue counterparts. PEAX-P hydrogel scavenges 51% DPPH radical, 40% hydroxyl radicals 41% nitrate radicals with 31% reducing power. The presence of hydrogel protects 62% cardiomyoblast cells treated with stress inducing media at LD 50 concentration. The free hydroxyl groups in sugar alcohols of the comacromer influence the free radical scavenging. Comparatively, PEAX-P hydrogel based on xylitol evinces slightly lower scavenging characteristics than with previously reported PEAM-P hydrogel containing mannitol having more hydroxyl groups. The possible free radical scavenging mechanism of the present hydrogel relies on the free π electrons associated with uncrosslinked fumarate bonds, hydrogen atoms associated with sugar alcohols/PEG and radical dilution by free water in the matrix. Briefly, the present PEAX-P hydrogel is a potential injectable system for combined antioxidant and regenerative therapy. Copyright © 2016 Elsevier B.V. All rights reserved.

Chitosan composite hydrogels reinforced with natural clay nanotubes.

PubMed

Huang, Biao; Liu, Mingxian; Zhou, Changren

2017-11-01

Here, chitosan composites hydrogels were prepared by addition of halloysite nanotubes (HNTs) in the chitosan KOH/LiOH/urea solution. The raw chitosan and chitosan/HNTs composite hydrogels were obtained by heat treatment at 60°C for 8h and then regeneration in ethanol solution. The viscosity of the composite solution is increased with HNTs content. The Fourier transform infrared spectroscopy (FT-IR) shows that the hydrogen bonds interactions exist between the HNTs and the chitosan. X-ray diffraction (XRD) results show that the crystal structure of HNT is not changed in the composite hydrogels. The compressive property test and storage modulus determination show that the mechanical properties and anti-deformation ability of the composite hydrogel significantly increase owing to the reinforcing effect of HNTs. The composites hydrogel with 66.7% HNTs can undergo 7 times compression cycles without breaking with compressive strength of 0.71MPa at 70% deformation, while pure chitosan hydrogel is broken after bearing 5 compression cycles with compressive strength of 0.14MPa and a maximum deformation of 59%. A porous structure with pore size of 100-500μm is found in the composite hydrogels by scanning electron microscopy (SEM), and the pore size and the swelling ratio in NaCl solution decrease by the addition of HNTs and the immersing of ethanol. Chitosan/HNTs composite hydrogels show low cytotoxicity towards MC3T3-E1 cells. Also, the composite hydrogels show a maximum drug entrapment efficiency of 45.7% for doxorubicin (DOX) which is much higher than that of pure chitosan hydrogel (27.5%). All the results illustrate that the chitosan/HNTs composite hydrogels show promising applications as biomaterials. Copyright © 2017 Elsevier Ltd. All rights reserved.

On-Demand Dissolution of Chemically Cross-Linked Hydrogels.

PubMed

Konieczynska, Marlena D; Grinstaff, Mark W

2017-02-21

The formation and subsequent on-demand dissolution of chemically cross-linked hydrogels is of keen interest to chemists, engineers, and clinicians. In this Account, we summarize our recent advances in the area of dissolvable chemically cross-linked hydrogels and provide a comparative discussion of other recent hydrogel systems. Using biocompatible macromonomers, we developed a library of cross-linked dendritic hydrogels that possess favorable properties, including biocompatibility, tissue adhesion, and swelling. Additionally, these hydrogels possess the unique ability to dissolve on-demand via application of a biocompatible aqueous solution. Each of the three hydrogel systems described employs a thiol-thioester exchange reaction as the mechanism of dissolution. These new materials successfully decrease bleeding in in vivo models of hepatic and aortic hemorrhage and dissolve on-demand, providing easy removal. In addition, we evaluated these hydrogels as dressings for second-degree burn wounds and performed proof-of-concept in vivo studies. These hydrogel wound dressings provide a means of repeatedly changing the dressing in a minimally invasive and atraumatic manner while also serving as a protective barrier against bacterial infection. Finally, we highlight the seminal work of other researchers in the field of dissolvable chemically cross-linked hydrogels using thiol-disulfide exchange, retro-Michael-type, and retro-Diels-Alder reactions. These chemistries provide a versatile synthetic toolbox to dissolve hydrogels in a controlled manner on time scales from minutes to weeks. Continued investigation of these dissolution approaches as well as the development of new chemical reactions will open doors to other avenues of on-demand dissolution and expand the application space for these materials. In summary, the management and closure of wounds after traumatic injury or surgical intervention are of significant clinical importance. Stimuli-responsive hydrogels that

Photothermal fabrication of microscale patterned DNA hydrogels

NASA Astrophysics Data System (ADS)

Shimomura, Suguru; Nishimura, Takahiro; Ogura, Yusuke; Tanida, Jun

2018-02-01

This paper introduces a method for fabricating microscale DNA hydrogels using irradiation with patterned light. Optical fabrication allows for the flexible and tunable formation of DNA hydrogels without changing the environmental conditions. Our scheme is based on local heat generation via the photothermal effect, which is induced by light irradiation on a quenching species. We demonstrate experimentally that, depending on the power and irradiation time, light irradiation enables the creation of local microscale DNA hydrogels, while the shapes of the DNA hydrogels are controlled by the irradiation patterns.

Preparation and characterization of collagen-hydroxyapatite/pectin composite.

PubMed

Wenpo, Feng; Gaofeng, Liang; Shuying, Feng; Yuanming, Qi; Keyong, Tang

2015-03-01

Pectin, a kind of plant polysaccharide, was introduced into collagen-hydroxyapatite composite system, and prepared collagen-hydroxyapatite/pectin (Col-HA/pectin) composite in situ. The structure of the composite was investigated by XRD, SEM, and FT-IR. The mechanical properties, water absorption, enzyme degradation, and cytotoxicity of the composite were investigated as well. The results show that the inorganic substance in the composite materials is hydroxyapatite in relatively low crystallinity. A new interface appeared by the interaction among hydroxyapatite and collagen-pectin, and formed smooth fine particles. The mechanical properties, water absorption, enzyme degradation, and cytotoxicity indicate a potential use in bone replacement for the new composite. Copyright © 2014 Elsevier B.V. All rights reserved.

Preparation of hydroxyapatite from animal bones.

PubMed

Sobczak, Agnieszka; Kowalski, Zygmunt; Wzorek, Zbigniew

2009-01-01

This paper presents the method of obtaining hydroxyapatite from animal bones. Bone sludge and calcined products were characterized by X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). Calcium concentration was determined with titration, and phosphorus--spectrophotometrically. Making use of the AAS and ICP methods the content of microelements was determined. In all the products, hydroxyapatite was the only crystalline phase indicated. The FT-IR spectra confirmed that calcination removed the total of organic substances. Calcium and phosphorus contents were 38% and 18%, respectively, which corresponded to the Ca/P molar ratio of nonstoichiometric hydroxyapatite. The specific surfaces of products were measured by BET method. The volume of micro- and mesopores was determined.

A precision structured smart hydrogel for sensing applications

NASA Astrophysics Data System (ADS)

Menges, J.; Kleinschmidt, P.; Bart, H.-J.; Oesterschulze, E.

2017-10-01

We report on a macroinitiator based smart hydrogel film applied on a microcantilever for sensing applications. The studied hydrogel features a comparatively wide dynamic range for changes in the electrolyte's ionic strength. Furthermore, it offers a simple spin coating process for thin film deposition as well as the capability to obtain high aspect ratio microstructures by reactive ion etching. This makes the hydrogel compatible to microelectromechanical system integration. As a proof of concept, we study the response of hydrogel functionalized cantilevers in aqueous sodium chloride solutions of varying ionic strength. In contrast to the majority of hydrogel materials reported in the literature, we found that our hydrogel still responds in high ionic strength environments. This may be of future interest for sensing e.g., in sea water or physiological environments like urine.

Glucose-specific poly(allylamine) hydrogels--a reassessment.

PubMed

Fazal, Furqan M; Hansen, David E

2007-01-01

Polymer hydrogels synthesized by crosslinking poly(allylamine hydrochloride) with (+/-)-epichlorohydrin in the presence of d-glucose-6-phosphate monobarium salt do not show imprinting on the molecular level. A series of hydrogels was prepared using the following five templates: d-glucose-6-phosphate monobarium salt, d-glucose, l-glucose, barium hydrogen phosphate (BaHPO(4)), and d-gluconamide; a hydrogel was also prepared in the absence of a template. For all six hydrogels, batch binding studies were conducted with d-glucose, l-glucose, d-fructose, and d-gluconamide. The extent of analyte sugar binding was determined using (1)H NMR. Each hydrogel shows approximately the same relative binding affinity for the different sugar derivatives, and none displays selectivity for either glucose enantiomer. The results of the binding studies correlate with the octanol-water partition coefficients of the sugars, indicative that differential solubilities in the bulk polymer account for the binding affinities observed. Thus, in contrast to templated hydrogels prepared using methacrylate- or acrylamide-based reagents, true imprinting does not occur in this novel, crosslinked-poly(allylamine hydrochloride) system.

Equilibrium swelling properties of polyampholytic hydrogels

NASA Astrophysics Data System (ADS)

English, Anthony E.; Mafé, Salvador; Manzanares, José A.; Yu, Xiahong; Grosberg, Alexander Yu.; Tanaka, Toyoichi

1996-06-01

The role of counter ions and ion dissociation in establishing the equilibrium swelling of balanced and unbalanced polyampholytic hydrogels has been investigated experimentally and theoretically. The swelling dependence on both the net charge offset and the external bath salt concentration has been examined using an acrylamide based polyampholytic hydrogels. By careful consideration of the swelling kinetics, we illustrate the effects of ion dissociation equilibria and counter ion shielding in polyampholytic hydrogels near their balance point where both polyelectrolyte and polyampholyte effects are present. The theory considers a Flory type swelling model where the Coulombic interactions between fixed ions in the hydrogel resemble those of an ionic solid with a Debye screening factor. Theoretical predictions from this model are in qualitative agreement with our experimental results.

Application of Hydrogels in Heart Valve Tissue Engineering

PubMed Central

Zhang, Xing; Xu, Bin; Puperi, Daniel S.; Wu, Yan; West, Jennifer L.; Grande-Allen, K. Jane

2015-01-01

With an increasing number of patients requiring valve replacement, there is heightened interest in advancing heart valve tissue engineering (HVTE) to provide solutions to the many limitations of current surgical treatments. A variety of materials have been developed as scaffolds for HVTE including natural polymers, synthetic polymers, and decellularized valvular matrices. Among them, biocompatible hydrogels are generating growing interest. Natural hydrogels, such as collagen and fibrin, generally show good bioactivity, but poor mechanical durability. Synthetic hydrogels, on the other hand, have tunable mechanical properties; however, appropriate cell-matrix interactions are difficult to obtain. Moreover, hydrogels can be used as cell carriers when the cellular component is seeded into the polymer meshes or decellularized valve scaffolds. In this review, we discuss current research strategies for HVTE with an emphasis on hydrogel applications. The physicochemical properties and fabrication methods of these hydrogels, as well as their mechanical properties and bioactivities are described. Performance of some hydrogels including in vitro evaluation using bioreactors and in vivo tests in different animal models are also discussed. For future HVTE, it will be compelling to examine how hydrogels can be constructed from composite materials to replicate mechanical properties and mimic biological functions of the native heart valve. PMID:25955010

Method to produce nanocrystalline powders of oxide-based phosphors for lighting applications

DOEpatents

Loureiro, Sergio Paulo Martins; Setlur, Anant Achyut; Williams, Darryl Stephen; Manoharan, Mohan; Srivastava, Alok Mani

2007-12-25

Some embodiments of the present invention are directed toward nanocrystalline oxide-based phosphor materials, and methods for making same. Typically, such methods comprise a steric entrapment route for converting precursors into such phosphor material. In some embodiments, the nanocrystalline oxide-based phosphor materials are quantum splitting phosphors. In some or other embodiments, such nanocrystalline oxide based phosphor materials provide reduced scattering, leading to greater efficiency, when used in lighting applications.

Hydrogel Actuation by Electric Field Driven Effects

NASA Astrophysics Data System (ADS)

Morales, Daniel Humphrey

Hydrogels are networks of crosslinked, hydrophilic polymers capable of absorbing and releasing large amounts of water while maintaining their structural integrity. Polyelectrolyte hydrogels are a subset of hydrogels that contain ionizable moieties, which render the network sensitive to the pH and the ionic strength of the media and provide mobile counterions, which impart conductivity. These networks are part of a class of "smart" material systems that can sense and adjust their shape in response to the external environment. Hence, the ability to program and modulate hydrogel shape change has great potential for novel biomaterial and soft robotics applications. We utilized electric field driven effects to manipulate the interaction of ions within polyelectrolyte hydrogels in order to induce controlled deformation and patterning. Additionally, electric fields can be used to promote the interactions of separate gel networks, as modular components, and particle assemblies within gel networks to develop new types of soft composite systems. First, we present and analyze a walking gel actuator comprised of cationic and anionic gel legs attached by electric field-promoted polyion complexation. We characterize the electro-osmotic response of the hydrogels as a function of charge density and external salt concentration. The gel walkers achieve unidirectional motion on flat elastomer substrates and exemplify a simple way to move and manipulate soft matter devices in aqueous solutions. An 'ionoprinting' technique is presented with the capability to topographically structure and actuate hydrated gels in two and three dimensions by locally patterning ions induced by electric fields. The bound charges change the local mechanical properties of the gel to induce relief patterns and evoke localized stress, causing rapid folding in air. The ionically patterned hydrogels exhibit programmable temporal and spatial shape transitions which can be tuned by the duration and/or strength of

Bioinspired Smart Actuator Based on Graphene Oxide-Polymer Hybrid Hydrogels.

PubMed

Wang, Tao; Huang, Jiahe; Yang, Yiqing; Zhang, Enzhong; Sun, Weixiang; Tong, Zhen

2015-10-28

Rapid response and strong mechanical properties are desired for smart materials used in soft actuators. A bioinspired hybrid hydrogel actuator was designed and prepared by series combination of three trunks of tough polymer-clay hydrogels to accomplish the comprehensive actuation of "extension-grasp-retraction" like a fishing rod. The hydrogels with thermo-creep and thermo-shrinking features were successively irradiated by near-infrared (NIR) to execute extension and retraction, respectively. The GO in the hydrogels absorbed the NIR energy and transformed it into thermo-energy rapidly and effectively. The hydrogel with adhesion or magnetic force was adopted as the "hook" of the hybrid hydrogel actuator for grasping object. The hook of the hybrid hydrogel actuator was replaceable according to applications, even with functional materials other than hydrogels. This study provides an innovative concept to explore new soft actuators through combining response hydrogels and programming the same stimulus.

Detection of hydroxyapatite in calcified cardiovascular tissues.

PubMed

Lee, Jae Sam; Morrisett, Joel D; Tung, Ching-Hsuan

2012-10-01

The objective of this study is to develop a method for selective detection of the calcific (hydroxyapatite) component in human aortic smooth muscle cells in vitro and in calcified cardiovascular tissues ex vivo. This method uses a novel optical molecular imaging contrast dye, Cy-HABP-19, to target calcified cells and tissues. A peptide that mimics the binding affinity of osteocalcin was used to label hydroxyapatite in vitro and ex vivo. Morphological changes in vascular smooth muscle cells were evaluated at an early stage of the mineralization process induced by extrinsic stimuli, osteogenic factors and a magnetic suspension cell culture. Hydroxyapatite components were detected in monolayers of these cells in the presence of osteogenic factors and a magnetic suspension environment. Atherosclerotic plaque contains multiple components including lipidic, fibrotic, thrombotic, and calcific materials. Using optical imaging and the Cy-HABP-19 molecular imaging probe, we demonstrated that hydroxyapatite components could be selectively distinguished from various calcium salts in human aortic smooth muscle cells in vitro and in calcified cardiovascular tissues, carotid endarterectomy samples and aortic valves, ex vivo. Hydroxyapatite deposits in cardiovascular tissues were selectively detected in the early stage of the calcification process using our Cy-HABP-19 probe. This new probe makes it possible to study the earliest events associated with vascular hydroxyapatite deposition at the cellular and molecular levels. This target-selective molecular imaging probe approach holds high potential for revealing early pathophysiological changes, leading to progression, regression, or stabilization of cardiovascular diseases. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Detection of Hydroxyapatite in Calcified Cardiovascular Tissues

PubMed Central

Lee, Jae Sam; Morrisett, Joel D.; Tung, Ching-Hsuan

2012-01-01

Objective The objective of this study is to develop a method for selective detection of the calcific (hydroxyapatite) component in human aortic smooth muscle cells in vitro and in calcified cardiovascular tissues ex vivo. This method uses a novel optical molecular imaging contrast dye, Cy-HABP-19, to target calcified cells and tissues. Methods A peptide that mimics the binding affinity of osteocalcin was used to label hydroxyapatite in vitro and ex vivo. Morphological changes in vascular smooth muscle cells were evaluated at an early stage of the mineralization process induced by extrinsic stimuli, osteogenic factors and a magnetic suspension cell culture. Hydroxyapatite components were detected in monolayers of these cells in the presence of osteogenic factors and a magnetic suspension environment. Results Atherosclerotic plaque contains multiple components including lipidic, fibrotic, thrombotic, and calcific materials. Using optical imaging and the Cy-HABP-19 molecular imaging probe, we demonstrated that hydroxyapatite components could be selectively distinguished from various calcium salts in human aortic smooth muscle cells in vitro and in calcified cardiovascular tissues, carotid endarterectomy samples and aortic valves, ex vivo. Conclusion Hydroxyapatite deposits in cardiovascular tissues were selectively detected in the early stage of the calcification process using our Cy-HABP-19 probe. This new probe makes it possible to study the earliest events associated with vascular hydroxyapatite deposition at the cellular and molecular levels. This target-selective molecular imaging probe approach holds high potential for revealing early pathophysiological changes, leading to progression, regression, or stabilization of cardiovascular diseases. PMID:22877867

Enzyme actuated bioresponsive hydrogels

NASA Astrophysics Data System (ADS)

Wilson, Andrew Nolan

Bioresponsive hydrogels are emerging with technological significance in targeted drug delivery, biosensors and regenerative medicine. Conferred with the ability to respond to specific biologically derived stimuli, the design challenge is in effectively linking the conferred biospecificity with an engineered response tailored to the needs of a particular application. Moreover, the fundamental phenomena governing the response must support an appropriate dynamic range and limit of detection. The design of these systems is inherently complicated due to the high interdependency of the governing phenomena that guide the sensing, transduction, and the actuation response of hydrogels. To investigate the dynamics of these materials, model systems may be used which seek to interrogate the system dynamics by uni-variable experimentation and limit confounding phenomena such as: polymer-solute interactions, polymer swelling dynamics and biomolecular reaction-diffusion concerns. To this end, a model system, alpha-chymotrypsin (Cht) (a protease) and a cleavable peptide-chromogen (pro-drug) covalently incorporated into a hydrogel, was investigated to understand the mechanisms of covalent loading and release by enzymatic cleavage in bio-responsive delivery systems. Using EDC and Sulfo-NHS, terminal carboxyl groups of N-succinyl-Ala-Ala-Pro-Phe p-nitroanilide, a cleavable chromogen, were conjugated to primary amines of a hydrated poly(HEMA)-based hydrogel. Hydrogel discs were incubated in buffered Cht causing enzyme-mediated cleavage of the peptide and concomitant release of the chromophore for monitoring. To investigate substrate loading and the effects of hydrogel morphology on the system, the concentration of the amino groups (5, 10, 20, and 30 mol%) and the cross-linked density (1, 5, 7, 9 and 12 mol%) were independently varied. Loading-Release Efficiency of the chromogen was shown to exhibit a positive relation to increasing amino groups (AEMA). The release rates demonstrated a

Polyisocyanopeptide hydrogels: A novel thermo-responsive hydrogel supporting pre-vascularization and the development of organotypic structures.

PubMed

Zimoch, Jakub; Padial, Joan Simó; Klar, Agnes S; Vallmajo-Martin, Queralt; Meuli, Martin; Biedermann, Thomas; Wilson, Christopher J; Rowan, Alan; Reichmann, Ernst

2018-04-01

Molecular and mechanical interactions with the 3D extracellular matrix are essential for cell functions such as survival, proliferation, migration, and differentiation. Thermo-responsive biomimetic polyisocyanopeptide (PIC) hydrogels are promising new candidates for 3D cell, tissue, and organ cultures. This is a synthetic, thermo-responsive and stress-stiffening material synthesized via polymerization of the corresponding monomers using a nickel perchlorate as a catalyst. It can be tailored to meet various demands of cells by modulating its stiffness and through the decoration of the polymer with short GRGDS peptides using copper free click chemistry. These peptides make the hydrogels biocompatible by mimicking the binding sites of certain integrins. This study focuses on the optimization of the PIC polymer properties for efficient cell, tissue and organ development. Screening for the optimal stiffness of the hydrogel and the ideal concentration of the GRGDS ligand conjugated with the polymer, enabled cell proliferation, migration and differentiation of various primary cell types of human origin. We demonstrate that fibroblasts, endothelial cells, adipose-derived stem cells and melanoma cells, do survive, thrive and differentiate in optimized PIC hydrogels. Importantly, these hydrogels support the spontaneous formation of complex structures like blood capillaries in vitro. Additionally, we utilized the thermo-responsive properties of the hydrogels for a rapid and gentle recovery of viable cells. Finally, we show that organotypic structures of human origin grown in PIC hydrogels can be successfully transplanted subcutaneously onto immune-compromised rats, on which they survive and integrate into the surrounding tissue. Molecular and mechanical interactions with the surrounding environment are essential for cell functions. Although 2D culture systems greatly contributed to our understanding of complex biological phenomena, they cannot substitute for crucial

Biodegradable synthetic bone composites

DOEpatents

Liu, Gao; Zhao, Dacheng; Saiz, Eduardo; Tomsia, Antoni P.

2013-01-01

The invention provides for a biodegradable synthetic bone composition comprising a biodegradable hydrogel polymer scaffold comprising a plurality of hydrolytically unstable linkages, and an inorganic component; such as a biodegradable poly(hydroxyethylmethacrylate)/hydroxyapatite (pHEMA/HA) hydrogel composite possessing mineral content approximately that of human bone.

Designing degradable hydrogels for orthogonal control of cell microenvironments

PubMed Central

Kharkar, Prathamesh M.

2013-01-01

Degradable and cell-compatible hydrogels can be designed to mimic the physical and biochemical characteristics of native extracellular matrices and provide tunability of degradation rates and related properties under physiological conditions. Hence, such hydrogels are finding widespread application in many bioengineering fields, including controlled bioactive molecule delivery, cell encapsulation for controlled three-dimensional culture, and tissue engineering. Cellular processes, such as adhesion, proliferation, spreading, migration, and differentiation, can be controlled within degradable, cell-compatible hydrogels with temporal tuning of biochemical or biophysical cues, such as growth factor presentation or hydrogel stiffness. However, thoughtful selection of hydrogel base materials, formation chemistries, and degradable moieties is necessary to achieve the appropriate level of property control and desired cellular response. In this review, hydrogel design considerations and materials for hydrogel preparation, ranging from natural polymers to synthetic polymers, are overviewed. Recent advances in chemical and physical methods to crosslink hydrogels are highlighted, as well as recent developments in controlling hydrogel degradation rates and modes of degradation. Special attention is given to spatial or temporal presentation of various biochemical and biophysical cues to modulate cell response in static (i.e., non-degradable) or dynamic (i.e., degradable) microenvironments. This review provides insight into the design of new cell-compatible, degradable hydrogels to understand and modulate cellular processes for various biomedical applications. PMID:23609001

Mechanical properties, structure, bioadhesion, and biocompatibility of pectin hydrogels.

PubMed

Markov, Pavel A; Krachkovsky, Nikita S; Durnev, Eugene A; Martinson, Ekaterina A; Litvinets, Sergey G; Popov, Sergey V

2017-09-01

The surface structure, biocompatibility, textural, and adhesive properties of calcium hydrogels derived from 1, 2, and 4% solutions of apple pectin were examined in this study. An increase in the pectin concentration in hydrogels was shown to improve their stability toward elastic and plastic deformation. The elasticity of pectin hydrogels, measured as Young's modulus, ranged from 6 to 100 kPa. The mechanical properties of the pectin hydrogels were shown to correspond to those of soft tissues. The characterization of surface roughness in terms of the roughness profile (Ra) and the root-mean-square deviation of the roughness profile (Rq) indicated an increased roughness profile for hydrogels depending on their pectin concentration. The adhesion of AU2% and AU4% hydrogels to the serosa abdominal wall, liver, and colon was higher than that of the AU1% hydrogel. The adhesion of macrophages and the non-specific adsorption of blood plasma proteins were found to increase as the pectin concentration in the hydrogels increased. The rate of degradation of all hydrogels was higher in phosphate buffered saline (PBS) than that in DMEM and a fibroblast cell monolayer. The pectin hydrogel was also found to have a low cytotoxicity. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2572-2581, 2017. © 2017 Wiley Periodicals, Inc.

A phytomodulatory hydrogel with enhanced healing effects.

PubMed

Vasconcelos, Mirele S; Souza, Tamiris F G; Figueiredo, Ingrid S; Sousa, Emília T; Sousa, Felipe D; Moreira, Renato A; Alencar, Nylane M N; Lima-Filho, José V; Ramos, Márcio V

2018-04-01

The healing performance of a hydrogel composed of hemicelluloses extracted from seeds of Caesalpinia pulcherrima (Fabaceae) and mixed with phytomodulatory proteins obtained from the latex of Calotropis procera was characterized on excisional wounds. The hydrogel did not induce dermal irritability. When topically used on excisional wounds, the hydrogel enhanced healing by wound contraction. Histology and the measurement of inflammatory mediators (myeloperoxidase, interleukin-1β, and interleukin-6) suggested that the inflammatory phase of the healing process was intensified, stimulating fibroplasia and neovascularization (proliferative phase) and tissue remodeling by increasing new collagen fiber deposition. In addition, reduction on levels of malondialdehyde in the groups that the hydrogel was applied suggested that the oxidative stress was reduced. The hydrogel performed better than the reference drug used, as revealed by the extended thickness of the remodeled epithelium. Copyright © 2018 John Wiley & Sons, Ltd.

Mechanical characterization and modeling of sponge-reinforced hydrogel composites under compression.

PubMed

Wu, Lei; Mao, Guoyong; Nian, Guodong; Xiang, Yuhai; Qian, Jin; Qu, Shaoxing

2018-05-30

Load-bearing applications of hydrogels call for materials with excellent mechanical properties. Despite the considerable progress in developing tough hydrogels, there is still a requirement to prepare high-performance hydrogels using simple strategies. In this paper, a sponge-reinforced hydrogel composite is synthesized by combining poly(acrylamide) (PAAm) hydrogel and polyurethane (PU) sponge. Uniaxial compressive testing of the hydrogel composites reveals that both the compressive modulus and the strength of the hydrogel composites are much higher than those of the PAAm hydrogel or sponge. In order to predict the compressive modulus of the hydrogel composite, we develop a theoretical model that is validated by experiments and numerical simulations. The present work may guide the design and manufacture of hydrogel-based composite materials, especially for biomaterial scaffolds and soft transducers.

Nanocrystalline Aluminum Truss Cores for Lightweight Sandwich Structures

NASA Astrophysics Data System (ADS)

Schaedler, Tobias A.; Chan, Lisa J.; Clough, Eric C.; Stilke, Morgan A.; Hundley, Jacob M.; Masur, Lawrence J.

2017-12-01

Substitution of conventional honeycomb composite sandwich structures with lighter alternatives has the potential to reduce the mass of future vehicles. Here we demonstrate nanocrystalline aluminum-manganese truss cores that achieve 2-4 times higher strength than aluminum alloy 5056 honeycombs of the same density. The scalable fabrication approach starts with additive manufacturing of polymer templates, followed by electrodeposition of nanocrystalline Al-Mn alloy, removal of the polymer, and facesheet integration. This facilitates curved and net-shaped sandwich structures, as well as co-curing of the facesheets, which eliminates the need for extra adhesive. The nanocrystalline Al-Mn alloy thin-film material exhibits high strength and ductility and can be converted into a three-dimensional hollow truss structure with this approach. Ultra-lightweight sandwich structures are of interest for a range of applications in aerospace, such as fairings, wings, and flaps, as well as for the automotive and sports industries.

A process for the development of strontium hydroxyapatite

NASA Astrophysics Data System (ADS)

Zahra, N.; Fayyaz, M.; Iqbal, W.; Irfan, M.; Alam, S.

2014-06-01

A procedure for the preparation of Strontium Hydroxyapatite is adapted to produce high purity and better homogeneity ceramic with good Crystallinity. The strontium substituted bone cement has potential for use in orthopedic surgeries. Ionic Strontium (Sr) in humans shares the same physiological pathway as calcium and can be deposited in the mineral structure of the bone. In the present study, a novel concept of preparing Sr-contained Hydroxyapatite bone cement by using a precipitation method is proposed to get an ideal biomaterial that possesses potential degradability and more excellent pharmacological effect. Chemical analysis, Fourier Transform Infra Red analysis and Thermogravimetric/ Differential Scanning Calorimetric studies were conducted on prepared Strontium Hydroxyapatite sample to characterize the incorporation of 15% Sr2+ into the crystal lattice of Hydroxyapatite. Strontium was quantitatively incorporated into Hydroxyapatite where its substitution for calcium provoked a linear shift of the infrared absorption bands of the hydroxyl and phosphate groups. Thus, the formation of Sr-HAp was confirmed by Chemical Analysis, FT-IR and TGA/DSC results.

Three-dimensional analysis by electron diffraction methods of nanocrystalline materials.

PubMed

Gammer, Christoph; Mangler, Clemens; Karnthaler, Hans-Peter; Rentenberger, Christian

2011-12-01

To analyze nanocrystalline structures quantitatively in 3D, a novel method is presented based on electron diffraction. It allows determination of the average size and morphology of the coherently scattering domains (CSD) in a straightforward way without the need to prepare multiple sections. The method is applicable to all kinds of bulk nanocrystalline materials. As an example, the average size of the CSD in nanocrystalline FeAl made by severe plastic deformation is determined in 3D. Assuming ellipsoidal CSD, it is deduced that the CSD have a width of 19 ± 2 nm, a length of 18 ± 1 nm, and a height of 10 ± 1 nm.

Nanocrystalline copper films are never flat

NASA Astrophysics Data System (ADS)

Zhang, Xiaopu; Han, Jian; Plombon, John J.; Sutton, Adrian P.; Srolovitz, David J.; Boland, John J.

2017-07-01

We used scanning tunneling microscopy to study low-angle grain boundaries at the surface of nearly planar copper nanocrystalline (111) films. The presence of grain boundaries and their emergence at the film surface create valleys composed of dissociated edge dislocations and ridges where partial dislocations have recombined. Geometric analysis and simulations indicated that valleys and ridges were created by an out-of-plane grain rotation driven by reduction of grain boundary energy. These results suggest that in general, it is impossible to form flat two-dimensional nanocrystalline films of copper and other metals exhibiting small stacking fault energies and/or large elastic anisotropy, which induce a large anisotropy in the dislocation-line energy.

Optimizing Double-Network Hydrogel for Biomedical Soft Robots.

PubMed

Banerjee, Hritwick; Ren, Hongliang

2017-09-01

Double-network hydrogel with standardized chemical parameters demonstrates a reasonable and viable alternative to silicone in soft robotic fabrication due to its biocompatibility, comparable mechanical properties, and customizability through the alterations of key variables. The most viable hydrogel sample in our article shows tensile strain of 851% and maximum tensile strength of 0.273 MPa. The elasticity and strength range of this hydrogel can be customized according to application requirements by simple alterations in the recipe. Furthermore, we incorporated Agar/PAM hydrogel into our highly constrained soft pneumatic actuator (SPA) design and eventually produced SPAs with escalated capabilities, such as larger range of motion, higher force output, and power efficiency. Incorporating SPAs made of Agar/PAM hydrogel resulted in low viscosity, thermos-reversibility, and ultralow elasticity, which we believe can help to combine with the other functions of hydrogel, tailoring a better solution for fabricating biocompatible soft robots.

Syntheses of nanocrystalline BaTiO3 and their optical properties

NASA Astrophysics Data System (ADS)

Yu, J.; Chu, J.; Zhang, M.

Stoichiometric and titanium-excess nanocrystalline barium titanates were synthesized using a hydrothermal process at various hydrothermal temperatures and with further heat treatment at 500 °C and 900 °C. Owing to the different process conditions, the excess titanium exists in different states and configurations within the nanocrystalline BaTiO3 matrix; this was demonstrated by X-ray diffraction, Raman scattering, and photoluminescence. In these nanocrystalline BaTiO3, the 590, 571, 543 and 694 nm light emission bands were observed; mechanisms leading to such emissions were also discussed.

Application of Hydrogel in Reconstruction Surgery: Hydrogel/Fat Graft Complex Filler for Volume Reconstruction in Critical Sized Muscle Defects.

PubMed

Lui, Y F; Ip, W Y

2016-01-01

Autogenic fat graft usually suffers from degeneration and volume shrinkage in volume reconstruction applications. How to maintain graft viability and graft volume is an essential consideration in reconstruction therapies. In this presented investigation, a new fat graft transplantation method was developed aiming to improve long term graft viability and volume reconstruction effect by incorporation of hydrogel. The harvested fat graft is dissociated into small fragments and incorporated into a collagen based hydrogel to form a hydrogel/fat graft complex for volume reconstruction purpose. In vitro results indicate that the collagen based hydrogel can significantly improve the survivability of cells inside isolated graft. In a 6-month investigation on artificial created defect model, this hydrogel/fat graft complex filler has demonstrated the ability of promoting fat pad formation inside the targeted defect area. The newly generated fat pad can cover the whole defect and restore its original dimension in 6-month time point. Compared to simple fat transplantation, this hydrogel/fat graft complex system provides much improvement on long term volume restoration effect against degeneration and volume shrinkage. One notable effect is that there is continuous proliferation of adipose tissue throughout the 6-month period. In summary, the hydrogel/fat graft system presented in this investigation demonstrated a better and more significant effect on volume reconstruction in large sized volume defect than simple fat transplantation.

Hydroxyapatite nanorods: soft-template synthesis, characterization and preliminary in vitro tests.

PubMed

Nguyen, Nga Kim; Leoni, Matteo; Maniglio, Devid; Migliaresi, Claudio

2013-07-01

Synthetic hydroxyapatite nanorods are excellent candidates for bone tissue engineering applications. In this study, hydroxyapatite nanorods resembling bone minerals were produced by using soft-template method with cetyltrimethylammonium bromide. Composite hydroxyapatite/poly(D, L)lactic acid films were prepared to evaluate the prepared hydroxyapatite nanorods in terms of cell affinity. Preliminary in vitro experiments showed that aspect ratio and film surface roughness play a vital role in controlling adhesion and proliferation of human osteoblast cell line MG 63. The hydroxyapatite nanorods with aspect ratios in the range of 5.94-7 were found to possess distinctive properties, with the corresponding hydroxyapatite/poly(D, L)lactic acid films promoting cellular confluence and a fast formation of collagen fibers as early as after 7 days of culture.

An improved biofunction of titanium for keratoprosthesis by hydroxyapatite-coating.

PubMed

Dong, Ying; Yang, Jingxin; Wang, Liqiang; Ma, Xiao; Huang, Yifei; Qiu, Zhiye; Cui, Fuzhai

2014-03-01

Titanium framework keratoprosthesis has been commonly used in the severe corneal blindness, but the tissue melting occurred frequently around titanium. Since hydroxyapatite has been approved to possess a good tissue integration characteristic, nanostructured hydroxyapatite was coated on the surface of titanium through the aerosol deposition method. In this study, nanostructured hydroxyapatite coating was characterized by X-ray diffraction, scanning electron microscopy, atomic force microscopy, and auger electronic spectrometer. Biological evaluations were performed with rabbit cornea fibroblast in vitro and an animal model in vivo. The outcomes showed the coating had a grain-like surface topography and a good atomic mixed area with substrate. The rabbit cornea fibroblasts appeared a good adhesion on the surface of nanostructured hydroxyapatite in vitro. In the animal model, nanostructured hydroxyapatite-titanium implants were stably retained in the rabbit cornea, and by contrast, the corneal stroma became thinner anterior to the implants in the control. Therefore, our findings proved that nanostructured hydroxyapatite-titanium could not only provide an improved bond for substrate but also enhance the tissue integration with implants in host. As a promising material, nanostructured hydroxyapatite-titanium-based keratoprosthesis prepared by the aerosol deposition method could be utilized for the corneal blindness treatment.

Tumor Growth Suppression Induced by Biomimetic Silk Fibroin Hydrogels

NASA Astrophysics Data System (ADS)

Yan, Le-Ping; Silva-Correia, Joana; Ribeiro, Viviana P.; Miranda-Gonçalves, Vera; Correia, Cristina; da Silva Morais, Alain; Sousa, Rui A.; Reis, Rui M.; Oliveira, Ana L.; Oliveira, Joaquim M.; Reis, Rui L.

2016-08-01

Protein-based hydrogels with distinct conformations which enable encapsulation or differentiation of cells are of great interest in 3D cancer research models. Conformational changes may cause macroscopic shifts in the hydrogels, allowing for its use as biosensors and drug carriers. In depth knowledge on how 3D conformational changes in proteins may affect cell fate and tumor formation is required. Thus, this study reports an enzymatically crosslinked silk fibroin (SF) hydrogel system that can undergo intrinsic conformation changes from random coil to β-sheet conformation. In random coil status, the SF hydrogels are transparent, elastic, and present ionic strength and pH stimuli-responses. The random coil hydrogels become β-sheet conformation after 10 days in vitro incubation and 14 days in vivo subcutaneous implantation in rat. When encapsulated with ATDC-5 cells, the random coil SF hydrogel promotes cell survival up to 7 days, whereas the subsequent β-sheet transition induces cell apoptosis in vitro. HeLa cells are further incorporated in SF hydrogels and the constructs are investigated in vitro and in an in vivo chick chorioallantoic membrane model for tumor formation. In vivo, Angiogenesis and tumor formation are suppressed in SF hydrogels. Therefore, these hydrogels provide new insights for cancer research and uses of biomaterials.

Distinctive glial and neuronal interfacing on nanocrystalline diamond.

PubMed

Bendali, Amel; Agnès, Charles; Meffert, Simone; Forster, Valérie; Bongrain, Alexandre; Arnault, Jean-Charles; Sahel, José-Alain; Offenhäusser, Andreas; Bergonzo, Philippe; Picaud, Serge

2014-01-01

Direct electrode/neuron interfacing is a key challenge to achieve high resolution of neuronal stimulation required for visual prostheses. Neuronal interfacing on biomaterials commonly requires the presence of glial cells and/or protein coating. Nanocrystalline diamond is a highly mechanically stable biomaterial with a remarkably large potential window for the electrical stimulation of tissues. Using adult retinal cell cultures from rats, we found that glial cells and retinal neurons grew equally well on glass and nanocrystalline diamond. The use of a protein coating increased cell survival, particularly for glial cells. However, bipolar neurons appeared to grow even in direct contact with bare diamond. We investigated whether the presence of glial cells contributed to this direct neuron/diamond interface, by using purified adult retinal ganglion cells to seed diamond and glass surfaces with and without protein coatings. Surprisingly, these fully differentiated spiking neurons survived better on nanocrystalline diamond without any protein coating. This greater survival was indicated by larger cell numbers and the presence of longer neurites. When a protein pattern was drawn on diamond, neurons did not grow preferentially on the coated area, by contrast to their behavior on a patterned glass. This study highlights the interesting biocompatibility properties of nanocrystalline diamond, allowing direct neuronal interfacing, whereas a protein coating was required for glial cell growth.

Distinctive Glial and Neuronal Interfacing on Nanocrystalline Diamond

PubMed Central

Bendali, Amel; Agnès, Charles; Meffert, Simone; Forster, Valérie; Bongrain, Alexandre; Arnault, Jean-Charles; Sahel, José-Alain; Offenhäusser, Andreas; Bergonzo, Philippe; Picaud, Serge

2014-01-01

Direct electrode/neuron interfacing is a key challenge to achieve high resolution of neuronal stimulation required for visual prostheses. Neuronal interfacing on biomaterials commonly requires the presence of glial cells and/or protein coating. Nanocrystalline diamond is a highly mechanically stable biomaterial with a remarkably large potential window for the electrical stimulation of tissues. Using adult retinal cell cultures from rats, we found that glial cells and retinal neurons grew equally well on glass and nanocrystalline diamond. The use of a protein coating increased cell survival, particularly for glial cells. However, bipolar neurons appeared to grow even in direct contact with bare diamond. We investigated whether the presence of glial cells contributed to this direct neuron/diamond interface, by using purified adult retinal ganglion cells to seed diamond and glass surfaces with and without protein coatings. Surprisingly, these fully differentiated spiking neurons survived better on nanocrystalline diamond without any protein coating. This greater survival was indicated by larger cell numbers and the presence of longer neurites. When a protein pattern was drawn on diamond, neurons did not grow preferentially on the coated area, by contrast to their behavior on a patterned glass. This study highlights the interesting biocompatibility properties of nanocrystalline diamond, allowing direct neuronal interfacing, whereas a protein coating was required for glial cell growth. PMID:24664111

Synthesis of hydroxyapatite nanoparticles from egg shells by sol-gel method

NASA Astrophysics Data System (ADS)

Azis, Y.; Adrian, M.; Alfarisi, C. D.; Khairat; Sri, R. M.

2018-04-01

Hydroxyapatite, [Ca10(PO4)6(OH)2, (HAp)] is widely used in medical fields especially as a bone and teeth substitute. Hydroxyapatite nanoparticles have been succesfully synthesized from egg shells as a source of calcium by using sol-gel method. The egg shells were calcined, hydrated (slaking) and undergone carbonation to form Precipitated Calcium Carbonate (PCC).Then the PCC was added (NH4)2HPO4 to form HAp with variation the mole ratio Ca and P (1.57; 1.67 and 1.77), aging time (24, 48, and 72 hr) and under basic condition pH (9, 10 and 11). The formation of hydroxyapatite biomaterial was characterized using XRD, FTIR, SEM-EDX. The XRD patterns showed that the products were hydroxyapatite crystals. The best result was obtained at 24 hr aging time, pH 9 with hexagonal structure of hydroxyapatite. Particle size of HAp was 35-54 nm and the morphology of hydroxyapatite observed using SEM, it showed that the uniformity crystal of hydroxyapatite.

Antimicrobial hydrogels: promising materials for medical application

PubMed Central

Yang, Kerong; Han, Qing; Chen, Bingpeng; Zheng, Yuhao; Zhang, Kesong; Li, Qiang; Wang, Jincheng

2018-01-01

The rapid emergence of antibiotic resistance in pathogenic microbes is becoming an imminent global public health problem. Local application of antibiotics might be a solution. In local application, materials need to act as the drug delivery system. The drug delivery system should be biodegradable and prolonged antibacterial effect should be provided to satisfy clinical demand. Hydrogel is a promising material for local antibacterial application. Hydrogel refers to a kind of biomaterial synthesized by a water-soluble natural polymer or a synthesized polymer, which turns into gel according to the change in different signals such as temperature, ionic strength, pH, ultraviolet exposure etc. Because of its high hydrophilicity, unique three-dimensional network, fine biocompatibility and cell adhesion, hydrogel is one of the suitable biomaterials for drug delivery in antimicrobial areas. In this review, studies from the past 5 years were reviewed, and several types of antimicrobial hydrogels according to different ingredients, different preparations, different antimicrobial mechanisms, different antimicrobial agents they contained and different applications, were summarized. The hydrogels loaded with metal nanoparticles as a potential method to solve antibiotic resistance were highlighted. Finally, future prospects of development and application of antimicrobial hydrogels are suggested. PMID:29695904

Hydrogel: Preparation, characterization, and applications: A review

PubMed Central

Ahmed, Enas M.

2013-01-01

Hydrogel products constitute a group of polymeric materials, the hydrophilic structure of which renders them capable of holding large amounts of water in their three-dimensional networks. Extensive employment of these products in a number of industrial and environmental areas of application is considered to be of prime importance. As expected, natural hydrogels were gradually replaced by synthetic types due to their higher water absorption capacity, long service life, and wide varieties of raw chemical resources. Literature on this subject was found to be expanding, especially in the scientific areas of research. However, a number of publications and technical reports dealing with hydrogel products from the engineering points of view were examined to overview technological aspects covering this growing multidisciplinary field of research. The primary objective of this article is to review the literature concerning classification of hydrogels on different bases, physical and chemical characteristics of these products, and technical feasibility of their utilization. It also involved technologies adopted for hydrogel production together with process design implications, block diagrams, and optimized conditions of the preparation process. An innovated category of recent generations of hydrogel materials was also presented in some details. PMID:25750745

Hydrogel based QCM aptasensor for detection of avian influenza virus.

PubMed

Wang, Ronghui; Li, Yanbin

2013-04-15

The objective of this study was to develop a quartz crystal microbalance (QCM) aptasensor based on ssDNA crosslinked polymeric hydrogel for rapid, sensitive and specific detection of avian influenza virus (AIV) H5N1. A selected aptamer with high affinity and specificity against AIV H5N1 surface protein was used, and hybridization between the aptamer and ssDNA formed the crosslinker in the polymer hydrogel. The aptamer hydrogel was immobilized on the gold surface of QCM sensor using a self-assembled monolayer method. The hydrogel remained in the state of shrink if no H5N1 virus was present in the sample because of the crosslinking between the aptamer and ssDNA in the polymer network. When it exposed to target virus, the binding reaction between the aptamer and H5N1 virus caused the dissolution of the linkage between the aptamer and ssDNA, resulting in the abrupt swelling of the hydrogel. The swollen hydrogel was monitored by the QCM sensor in terms of decreased frequency. Three polymeric hydrogels with different ratio (100:1 hydrogel I, 10:1 hydrogel II, 1:1 hydrogel III) of acrylamide and the aptamer monomer were synthesized, respectively, and then were used as the QCM sensor coating material. The results showed that the developed hydrogel QCM aptasensor was capable of detecting target H5N1 virus, and among the three developed aptamer hydrogels, hydrogel III coated QCM aptasensor achieved the highest sensitivity with the detection limit of 0.0128 HAU (HA unit). The total detection time from sampling to detection was only 30 min. In comparison with the anti-H5 antibody coated QCM immunosensor, the hydrogel QCM aptasensor lowered the detection limit and reduced the detection time. Copyright © 2012 Elsevier B.V. All rights reserved.

Thin Hydrogel Films for Optical Biosensor Applications

PubMed Central

Mateescu, Anca; Wang, Yi; Dostalek, Jakub; Jonas, Ulrich

2012-01-01

Hydrogel materials consisting of water-swollen polymer networks exhibit a large number of specific properties highly attractive for a variety of optical biosensor applications. This properties profile embraces the aqueous swelling medium as the basis of biocompatibility, non-fouling behavior, and being not cell toxic, while providing high optical quality and transparency. The present review focuses on some of the most interesting aspects of surface-attached hydrogel films as active binding matrices in optical biosensors based on surface plasmon resonance and optical waveguide mode spectroscopy. In particular, the chemical nature, specific properties, and applications of such hydrogel surface architectures for highly sensitive affinity biosensors based on evanescent wave optics are discussed. The specific class of responsive hydrogel systems, which can change their physical state in response to externally applied stimuli, have found large interest as sophisticated materials that provide a complex behavior to hydrogel-based sensing devices. PMID:24957962

Extreme creep resistance in a microstructurally stable nanocrystalline alloy

NASA Astrophysics Data System (ADS)

Darling, K. A.; Rajagopalan, M.; Komarasamy, M.; Bhatia, M. A.; Hornbuckle, B. C.; Mishra, R. S.; Solanki, K. N.

2016-09-01

Nanocrystalline metals, with a mean grain size of less than 100 nanometres, have greater room-temperature strength than their coarse-grained equivalents, in part owing to a large reduction in grain size. However, this high strength generally comes with substantial losses in other mechanical properties, such as creep resistance, which limits their practical utility; for example, creep rates in nanocrystalline copper are about four orders of magnitude higher than those in typical coarse-grained copper. The degradation of creep resistance in nanocrystalline materials is in part due to an increase in the volume fraction of grain boundaries, which lack long-range crystalline order and lead to processes such as diffusional creep, sliding and rotation. Here we show that nanocrystalline copper-tantalum alloys possess an unprecedented combination of properties: high strength combined with extremely high-temperature creep resistance, while maintaining mechanical and thermal stability. Precursory work on this family of immiscible alloys has previously highlighted their thermo-mechanical stability and strength, which has motivated their study under more extreme conditions, such as creep. We find a steady-state creep rate of less than 10-6 per second—six to eight orders of magnitude lower than most nanocrystalline metals—at various temperatures between 0.5 and 0.64 times the melting temperature of the matrix (1,356 kelvin) under an applied stress ranging from 0.85 per cent to 1.2 per cent of the shear modulus. The unusual combination of properties in our nanocrystalline alloy is achieved via a processing route that creates distinct nanoclusters of atoms that pin grain boundaries within the alloy. This pinning improves the kinetic stability of the grains by increasing the energy barrier for grain-boundary sliding and rotation and by inhibiting grain coarsening, under extremely long-term creep conditions. Our processing approach should enable the development of

Protein-based hydrogels for tissue engineering

PubMed Central

Schloss, Ashley C.; Williams, Danielle M.; Regan, Lynne J.

2017-01-01

The tunable mechanical and structural properties of protein-based hydrogels make them excellent scaffolds for tissue engineering and repair. Moreover, using protein-based components provides the option to insert sequences associated with the promoting both cellular adhesion to the substrate and overall cell growth. Protein-based hydrogel components are appealing for their structural designability, specific biological functionality, and stimuli-responsiveness. Here we present highlights in the field of protein-based hydrogels for tissue engineering applications including design requirements, components, and gel types. PMID:27677513

Hydrogel-Based Drug Delivery Systems for Poorly Water-Soluble Drugs.

PubMed

McKenzie, Matthew; Betts, David; Suh, Amy; Bui, Kathryn; Kim, London Doyoung; Cho, Hyunah

2015-11-13

Hydrogels are three-dimensional materials that can withstand a great amount of water incorporation while maintaining integrity. This allows hydrogels to be very unique biomedical materials, especially for drug delivery. Much effort has been made to incorporate hydrophilic molecules in hydrogels in the field of drug delivery, while loading of hydrophobic drugs has not been vastly studied. However, in recent years, research has also been conducted on incorporating hydrophobic molecules within hydrogel matrices for achieving a steady release of drugs to treat various ailments. Here, we summarize the types of hydrogels used as drug delivery vehicles, various methods to incorporate hydrophobic molecules in hydrogel matrices, and the potential therapeutic applications of hydrogels in cancer.

Glucose-responsive hydrogel electrode for biocompatible glucose transistor

NASA Astrophysics Data System (ADS)

Kajisa, Taira; Sakata, Toshiya

2017-12-01

In this paper, we propose a highly sensitive and biocompatible glucose sensor using a semiconductor-based field effect transistor (FET) with a functionalized hydrogel. The principle of the FET device contributes to the easy detection of ionic charges with high sensitivity, and the hydrogel coated on the electrode enables the specific detection of glucose with biocompatibility. The copolymerized hydrogel on the Au gate electrode of the FET device is optimized by controlling the mixture ratio of biocompatible 2-hydroxyethylmethacrylate (HEMA) as the main monomer and vinylphenylboronic acid (VPBA) as a glucose-responsive monomer. The gate surface potential of the hydrogel FETs shifts in the negative direction with increasing glucose concentration from 10 μM to 40 mM, which results from the increase in the negative charges on the basis of the diol-binding of PBA derivatives with glucose molecules in the hydrogel. Moreover, the hydrogel coated on the gate suppresses the signal noise caused by the nonspecific adsorption of proteins such as albumin. The hydrogel FET can serve as a highly sensitive and biocompatible glucose sensor in in vivo or ex vivo applications such as eye contact lenses and sheets adhering to the skin.

Enzymatic regulation of functional vascular networks using gelatin hydrogels

PubMed Central

Chuang, Chia-Hui; Lin, Ruei-Zeng; Tien, Han-Wen; Chu, Ya-Chun; Li, Yen-Cheng; Melero-Martin, Juan M.; Chen, Ying-Chieh

2015-01-01

To manufacture tissue engineering-based functional tissues, scaffold materials that can be sufficiently vascularized to mimic the functionality and complexity of native tissues are needed. Currently, vascular network bioengineering is largely carried out using natural hydrogels as embedding scaffolds, but most natural hydrogels have poor mechanical stability and durability, factors that critically limit their widespread use. In this study, we examined the suitability of gelatin-phenolic hydroxyl (gelatin-Ph) hydrogels that can be enzymatically crosslinked, allowing tuning of the storage modulus and the proteolytic degradation rate, for use as injectable hydrogels to support the human progenitor cell-based formation of a stable and mature vascular network. Porcine gelatin-Ph hydrogels were found to be cytocompatible with human blood-derived endothelial colony-forming cells and white adipose tissue-derived mesenchymal stem cells, resulting in >87% viability, and cell proliferation and spreading could be modulated by using hydrogels with different proteolytic degradability and stiffness. In addition, gelatin was extracted from mouse dermis and murine gelatin-Ph hydrogels were prepared. Importantly, implantation of human cell-laden porcine or murine gelatin-Ph hydrogels into immunodeficient mice resulted in the rapid formation of functional anastomoses between the bioengineered human vascular network and the mouse vasculature. Furthermore, the degree of enzymatic crosslinking of the gelatin-Ph hydrogels could be used to modulate cell behavior and the extent of vascular network formation in vivo. Our report details a technique for the synthesis of gelatin-Ph hydrogels from allogeneic or xenogeneic dermal skin and suggests that these hydrogels can be used for biomedical applications that require the formation of microvascular networks, including the development of complex engineered tissues. PMID:25749296

Luminescence and related properties of nanocrystalline porous silicon

NASA Astrophysics Data System (ADS)

Koshida, N.

This document is part of subvolume C3 'Optical Properties' of volume 34 'Semiconductor quantum structures' of Landolt-Börnstein, Group III, Condensed Matter, on the optical properties of quantum structures based on group IV semiconductors. It discusses luminescence and related properties of nanocrystalline porous silicon. Topics include an overview of nanostructured silicon, its fabrication technology, and properties of nanocrystalline porous silicon such as confinement effects, photoluminescence, electroluminesce, carrier charging effects, ballistic transport and emission, and thermally induced acoustic emission.

Hydroxyapatites and europium(III) doped hydroxyapatites as a carrier of silver nanoparticles and their antimicrobial activity.

PubMed

Wiglusz, Rafal J; Kedziora, Anna; Lukowiak, Anna; Doroszkiewicz, Wlodzimierz; Strek, Wieslaw

2012-08-01

Hydroxyapatites (Ca10(PO4)6(OH)2 and Eu3+:Ca10(PO4)6(OH)2) were synthesized by aqueous synthesis route. Hydroxyapatites were impregnated with silver ions that were subsequently reduced. XRD, TEM, and SAED measurements were used in order to determine the crystal structure and morphology of the final products. The results showed the well crystallized hydroxyapatite grains with diameter of about 35 nm and with silver nanoparticles on their surface. The antimicrobial activity of the nanoparticles against: Staphylococcus aureus ATCC 6538 as model of the Gram-positive bacteria, Escherichia coli ATCC 11229, and Klebsiella pneumoniae ATCC 4352 as model of Gram-negative bacteria, were shown with the best activity against K. pneumoniae. These nanocomposite powders can be a promising antimicrobial agent and a fluorescent material for biodetection due to their optical and bioactive properties.

Antimicrobial cellulosic hydrogel from olive oil industrial residue.

PubMed

Dacrory, Sawsan; Abou-Yousef, Hussein; Abouzeid, Ragab E; Kamel, Samir; Abdel-Aziz, Mohamed S; El-Badry, Mohamed

2018-05-25

The cellulose-based antimicrobial hydrogel was prepared from seed and husk cellulosic fibers of olive industry residues by load silver nanoparticles (AgNPs) onto grafted acrylamide monomer (Am) cellulosic fibers. The grafting approach was the free radical mechanism by utilizing ceric ammonium nitrate (CAN) as initiator in aqueous medium and N,N methylene bisacrylamide (MBAm) as a cross linker. The effect of different grafting conditions on the properties of produced hydrogels has been studied by determining the grafting parameters, i.e. concentration of Am, MBAm, grafting time and temperature to optimize grafting yield (G %), grafting efficiency (GE %), and swelling %. Characterizations of the obtained hydrogels were performed through monitoring swelling behavior, FTIR spectroscopy, SEM, and EDX. AgNPs were grown into the prepared hydrogel. Hydrogel/AgNPs were characterized by FT-IR spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The hydrogel loaded AgNPs exhibit high efficient antimicrobial activity against Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans. Copyright © 2018. Published by Elsevier B.V.

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.

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

Nucleation of hydroxyapatite by bone sialoprotein.

PubMed Central

Hunter, G K; Goldberg, H A

1993-01-01

Bone sialoprotein (BSP) and osteopontin, the major phosphorylated proteins of mammalian bone, have been proposed to function in the initiation of mineralization. To test this hypothesis, the effects of BSP and osteopontin on hydroxyapatite crystal formation were determined by using a steady-state agarose gel system. At low calcium phosphate concentrations, no accumulation of calcium and phosphate occurred in control gels or gels containing osteopontin. Gels containing BSP at 1-5 micrograms/ml, however, exhibited a visible precipitation band and significantly elevated Ca + PO4 contents. By powder x-ray diffraction, the precipitate formed in the presence of BSP was shown to be hydroxyapatite. These findings suggest that bone sialoprotein may be involved in the nucleation of hydroxyapatite at the mineralization front of bone. Images Fig. 4 PMID:8397409

Biodegradable and photocrosslinkable polyphosphoester hydrogel

PubMed Central

Li, Qiang; Wang, Jun; Shahani, Shilpa; Sun, Danny D.N.; Sharma, Blanka; Elisseeff, Jennifer H.; Leong, Kam W.

2008-01-01

A new biodegradable, photocrosslinkable and multifunctional macromer, poly(6-aminohexyl propylene phosphate) (PPE-HA)-ACRL, was synthesized by conjugation of acrylate groups to the side chains of PPE-HA. By controlling the synthetic conditions, different weight fractions of acrylate in the macromers were achieved as confirmed by 1H NMR. The hydrogels obtained from PPE-HA-ACRL through photocrosslinking were dominantly elastic. With increasing acrylate contents in the macromers, the hydrogels exhibited a lower swelling ratio and higher mechanical strength. The hydrogels with different crosslinking densities lost between 4.3% and 37.4% of their mass in 84 days when incubated in phosphate-buffered saline at 37 °C. No significant cytotoxicity of the macromers against bone marrow-derived mesenchymal stem cells from goat (GMSC) was observed at a concentration up to 10 mg/ml. Finally, GMSCs encapsulated in the photopolymerized gel maintained their viability when cultured in osteogenic medium for three weeks. Clear mineralization in the hydrogel scaffold was revealed by Von Kossa staining. This study suggests the potential of these biodegradable and photocrosslinkable as injectable tissue engineering scaffolds. PMID:16125222

Gigacycle fatigue behavior by ultrasonic nanocrystalline surface modification.

PubMed

Ahn, D G; Amanov, A; Cho, I S; Shin, K S; Pyoun, Y S; Lee, C S; Park, I G

2012-07-01

Nanocrystalline surface layer up to 84 microm in thick is produced on a specimen made of Al6061-T6 alloy by means of surface treatment called ultrasonic nanocrystalline surface modification (UNSM) technique. The refined grain size is produced in the top-layer and it is increased with increasing depth from the top surface. Vickers microhardness measurement for each nanocrystalline surface layer is performed and measurement results showed that the microhardness is increased from 116 HV up to 150 HV, respectively. In this study, fatigue behavior of Al6061-T6 alloy was studied up to 10(7)-10(9) cycles by using a newly developed ultrasonic fatigue testing (UFT) rig. The fatigue results of the UNSM-treated Al6061-T6 alloy specimens were compared with those of the untreated specimens. The microstructure of the untreated and UNSM-treated specimens was characterized by means of scanning electron microscopey (SEM) and transmission electron microscopey (TEM).

Two-dimensional inverse opal hydrogel for pH sensing.

PubMed

Xue, Fei; Meng, Zihui; Qi, Fenglian; Xue, Min; Wang, Fengyan; Chen, Wei; Yan, Zequn

2014-12-07

A novel hydrogel film with a highly ordered macropore monolayer on its surface was prepared by templated photo-polymerization of hydrogel monomers on a two-dimensional (2D) polystyrene colloidal array. The 2D inverse opal hydrogel has prominent advantages over traditional three-dimensional (3D) inverse opal hydrogels. First, the formation of the 2D array template through a self-assembly method is considerably faster and simpler. Second, the stable ordering structure of the 2D array template makes it easier to introduce the polymerization solution into the template. Third, a simple measurement, a Debye diffraction ring, is utilized to characterize the neighboring pore spacing of the 2D inverse opal hydrogel. Acrylic acid was copolymerized into the hydrogel; thus, the hydrogel responded to pH through volume change, which resulted from the formation of the Donnan potential. The 2D inverse opal hydrogel showed that the neighboring pore spacing increased by about 150 nm and diffracted color red-shifted from blue to red as the pH increased from pH 2 to 7. In addition, the pH response kinetics and ionic strength effect of this 2D mesoporous polymer film were also investigated.

Development of lattice-inserted 5-Fluorouracil-hydroxyapatite nanoparticles as a chemotherapeutic delivery system.

PubMed

Tseng, Ching-Li; Chen, Jung-Chih; Wu, Yu-Chun; Fang, Hsu-Wei; Lin, Feng-Huei; Tang, Tzu-Piao

2015-10-01

Developing an effective vehicle for cancer treatment, hydroxyapatite nanoparticles were fabricated for drug delivery. When 5-Fluorouracil, a major chemoagent, is combined with hydroxyapatite nanocarriers by interclay insertion, the modified hydroxyapatite nanoparticles have superior lysosomal degradation profiles, which could be leveraged as controlled drug release. The decomposition of the hydroxyapatite nanocarriers facilitates the release of 5-Fluorouracil into the cytoplasm causing cell death. Hydroxyapatite nanoparticles with/without 5-Fluorouracil were synthesized and analyzed in this study. Their crystallization properties and chemical composition were examined by X-ray diffraction and Fourier transforms infrared spectroscopy. The 5-Fluorouracil release rate was determined by UV spectroscopy. The biocompatibility of hydroxyapatite-5-Fluorouracil extraction solution was assessed using 3T3 cells via a WST-8 assay. The effect of hydroxyapatite-5-Fluorouracil particles which directly work on the human lung adenocarcinoma (A549) cells was evaluated by a lactate dehydrogenase assay via contact cultivation. A 5-Fluorouracil-absorbed hydroxyapatite particles were also tested. Overall, hydroxyapatite-5-Fluorouracils were prepared using a co-precipitation method wherein 5-Fluorouracil was intercalated in the hydroxyapatite lattice as determined by X-ray diffraction. Energy dispersive scanning examination showed the 5-Fluorouracil content was higher in hydroxyapatite-5-Fluorouracil than in a prepared absorption formulation. With 5-Fluorouracil insertion in the lattice, the widths of the a and c axial constants of the hydroxyapatite crystal increased. The extraction solution of hydroxyapatite-5-Fluorouracil was nontoxic to 3T3 cells, in which 5-Fluorouracil was not released in a neutral phosphate buffer solution. In contrast, at a lower pH value (2.5), 5-Fluorouracil was released by the acidic decomposition of hydroxyapatite. Finally, the results of the lactate

Carbonate Hydroxyapatite and Silicon-Substituted Carbonate Hydroxyapatite: Synthesis, Mechanical Properties, and Solubility Evaluations

PubMed Central

Bang, L. T.; Long, B. D.; Othman, R.

2014-01-01

The present study investigates the chemical composition, solubility, and physical and mechanical properties of carbonate hydroxyapatite (CO3Ap) and silicon-substituted carbonate hydroxyapatite (Si-CO3Ap) which have been prepared by a simple precipitation method. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence (XRF) spectroscopy, and inductively coupled plasma (ICP) techniques were used to characterize the formation of CO3Ap and Si-CO3Ap. The results revealed that the silicate (SiO4 4−) and carbonate (CO3 2−) ions competed to occupy the phosphate (PO4 3−) site and also entered simultaneously into the hydroxyapatite structure. The Si-substituted CO3Ap reduced the powder crystallinity and promoted ion release which resulted in a better solubility compared to that of Si-free CO3Ap. The mean particle size of Si-CO3Ap was much finer than that of CO3Ap. At 750°C heat-treatment temperature, the diametral tensile strengths (DTS) of Si-CO3Ap and CO3Ap were about 10.8 ± 0.3 and 11.8 ± 0.4 MPa, respectively. PMID:24723840

Tough and tunable adhesion of hydrogels: experiments and models

NASA Astrophysics Data System (ADS)

Zhang, Teng; Yuk, Hyunwoo; Lin, Shaoting; Parada, German A.; Zhao, Xuanhe

2017-06-01

As polymer networks infiltrated with water, hydrogels are major constituents of animal and plant bodies and have diverse engineering applications. While natural hydrogels can robustly adhere to other biological materials, such as bonding of tendons and cartilage on bones and adhesive plaques of mussels, it is challenging to achieve such tough adhesions between synthetic hydrogels and engineering materials. Recent experiments show that chemically anchoring long-chain polymer networks of tough synthetic hydrogels on solid surfaces create adhesions tougher than their natural counterparts, but the underlying mechanism has not been well understood. It is also challenging to tune systematically the adhesion of hydrogels on solids. Here, we provide a quantitative understanding of the mechanism for tough adhesions of hydrogels on solid materials via a combination of experiments, theory, and numerical simulations. Using a coupled cohesive-zone and Mullins-effect model validated by experiments, we reveal the interplays of intrinsic work of adhesion, interfacial strength, and energy dissipation in bulk hydrogels in order to achieve tough adhesions. We further show that hydrogel adhesion can be systematically tuned by tailoring the hydrogel geometry and silanization time of solid substrates, corresponding to the control of energy dissipation zone and intrinsic work of adhesion, respectively. The current work further provides a theoretical foundation for rational design of future biocompatible and underwater adhesives.

Cellular Response to Reagent-Free Electron-Irradiated Gelatin Hydrogels.

PubMed

Wisotzki, Emilia I; Friedrich, Ralf P; Weidt, Astrid; Alexiou, Christoph; Mayr, Stefan G; Zink, Mareike

2016-06-01

As a biomaterial, it is well established that gelatin exhibits low cytotoxicity and can promote cellular growth. However, to circumvent the potential toxicity of chemical crosslinkers, reagent-free crosslinking methods such as electron irradiation are highly desirable. While high energy irradiation has been shown to exhibit precise control over the degree of crosslinking, these hydrogels have not been thoroughly investigated for biocompatibility and degradability. Here, NIH 3T3 murine fibroblasts are seeded onto irradiated gelatin hydrogels to examine the hydrogel's influence on cellular viability and morphology. The average projected area of cells seeded onto the hydrogels increases with irradiation dose, which correlates with an increase in the hydrogel's shear modulus up to 10 kPa. Cells on these hydrogels are highly viable and exhibits normal cell cycles, particularly when compared to those grown on glutaraldehyde crosslinked gelatin hydrogels. However, proliferation is reduced on both types of crosslinked samples. To mimic the response of the hydrogels in physiological conditions, degradability is monitored in simulated body fluid to reveal strongly dose-dependent degradation times. Overall, given the low cytotoxicity, influence on cellular morphology and variability in degradation times of the electron irradiated gelatin hydrogels, there is significant potential for application in areas ranging from regenerative medicine to mechanobiology. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis of Mesoporous Nanocrystalline Zirconia by Surfactant-Assisted Hydrothermal Approach.

PubMed

Nath, Soumav; Biswas, Ashik; Kour, Prachi P; Sarma, Loka S; Sur, Ujjal Kumar; Ankamwar, Balaprasad G

2018-08-01

In this paper, we have reported the chemical synthesis of thermally stable mesoporous nanocrystalline zirconia with high surface area using a surfactant-assisted hydrothermal approach. We have employed different type of surfactants such as CTAB, SDS and Triton X-100 in our synthesis. The synthesized nanocrystalline zirconia multistructures exhibit various morphologies such as rod, mortar-pestle with different particle sizes. We have characterized the zirconia multistructures by X-ray diffraction study, Field emission scanning electron microscopy, Attenuated total refection infrared spectroscopy, UV-Vis spectroscopy and photoluminescence spectroscopy. The thermal stability of as synthesized zirconia multistructures was studied by thermo gravimetric analysis, which shows the high thermal stability of nanocrystalline zirconia around 900 °C temperature.

Friction of sodium alginate hydrogel scaffold fabricated by 3-D printing.

PubMed

Yang, Qian; Li, Jian; Xu, Heng; Long, Shijun; Li, Xuefeng

2017-04-01

A rapid prototyping technology, formed by three-dimensional (3-D) printing and then crosslinked by spraying Ca 2+ solution, is developed to fabricate a sodium alginate (SA) hydrogel scaffold. The porosity, swelling ratio, and compression modulus of the scaffold are investigated. A friction mechanism is developed by studying the reproducible friction behavior. Our results show that the scaffold can have 3-D structure with a porosity of 52%. The degree of swelling of the SA hydrogel scaffold is 8.5, which is nearly the same as bulk SA hydrogel. SA hydrogel exhibits better compressive resilience than bulk hydrogel despite its lower compressive modulus compared to bulk hydrogel. The SA hydrogel scaffold exhibits a higher frictional force at low sliding velocity (10 -6 to 10 -3  m/s) compared to bulk SA hydrogel, and they are equal at high sliding velocity (10 -2 to 1 m/s). For a small pressure (0.3 kPa), the SA hydrogel scaffold shows good friction reproducibility. In contrast, bulk SA hydrogel shows poor reproducibility with respect to friction behavior. The differences in friction behaviors between the SA hydrogel scaffold and bulk SA hydrogel are related to the structure of the scaffold, which can keep a stable hydrated lubrication layer.

DNA-templated assembly of viral protein hydrogel

NASA Astrophysics Data System (ADS)

Xu, Xin; Tao, Ailin; Xu, Yun

2014-11-01

Hydrogels are a promising class of biomaterials that can be easily tailored to produce a native extracellular matrix that exhibits desirable mechanical and chemical properties. Here we report the construction of a hydrogel via the assembly of cucumber mosaic virus (CMV) capsid protein and Y-shaped and cross-shaped DNAs.Hydrogels are a promising class of biomaterials that can be easily tailored to produce a native extracellular matrix that exhibits desirable mechanical and chemical properties. Here we report the construction of a hydrogel via the assembly of cucumber mosaic virus (CMV) capsid protein and Y-shaped and cross-shaped DNAs. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr02414a

Biodegradable Cellulose-based Hydrogels: Design and Applications

PubMed Central

Sannino, Alessandro; Demitri, Christian; Madaghiele, Marta

2009-01-01

Hydrogels are macromolecular networks able to absorb and release water solutions in a reversible manner, in response to specific environmental stimuli. Such stimuli-sensitive behaviour makes hydrogels appealing for the design of ‘smart’ devices, applicable in a variety of technological fields. In particular, in cases where either ecological or biocompatibility issues are concerned, the biodegradability of the hydrogel network, together with the control of the degradation rate, may provide additional value to the developed device. This review surveys the design and the applications of cellulose-based hydrogels, which are extensively investigated due to the large availability of cellulose in nature, the intrinsic degradability of cellulose and the smart behaviour displayed by some cellulose derivatives.

Dextran/Albumin hydrogel sealant for Dacron(R) vascular prosthesis.

PubMed

Lisman, Anna; Butruk, Beata; Wasiak, Iga; Ciach, Tomasz

2014-05-01

In this paper, the authors describe a novel type of hydrogel coating prepared from the copolymer of human serum albumin and oxidized dextran. The material was designed as a hydrogel sealant for polyester (Dacron®)-based vascular grafts. Dextran was chosen as a coating material due to its anti-thrombogenic properties. Prepared hydrogels were compared with similar, already known biomaterial made from gelatine with the same cross-linking agent. Obtained hydrogels, prepared from various ratios of oxidized dextran/albumin or oxidized dextran/gelatine, showed different cross-linking densities, which caused differences in swelling, degradation rate and mechanical properties. Permeability tests confirmed the complete tightness of the hydrogel-modified prosthesis. Results showed that application of the hydrogel coating provided leakage-free prosthesis and eliminated the need of pre-clotting.

Adaptable Hydrogel Networks with Reversible Linkages for Tissue Engineering

PubMed Central

Wang, Huiyuan

2015-01-01

Adaptable hydrogels have recently emerged as a promising platform for three-dimensional (3D) cell encapsulation and culture. In conventional, covalently crosslinked hydrogels, degradation is typically required to allow complex cellular functions to occur, leading to bulk material degradation. In contrast, adaptable hydrogels are formed by reversible crosslinks. Through breaking and re-forming of the reversible linkages, adaptable hydrogels can be locally modified to permit complex cellular functions while maintaining their long-term integrity. In addition, these adaptable materials can have biomimetic viscoelastic properties that make them well suited for several biotechnology and medical applications. In this review, adaptable hydrogel design considerations and linkage selections are overviewed, with a focus on various cell compatible crosslinking mechanisms that can be exploited to form adaptable hydrogels for tissue engineering. PMID:25989348

Development of functionalized hydroxyapatite/poly(vinyl alcohol) composites

NASA Astrophysics Data System (ADS)

Stipniece, Liga; Salma-Ancane, Kristine; Rjabovs, Vitalijs; Juhnevica, Inna; Turks, Maris; Narkevica, Inga; Berzina-Cimdina, Liga

2016-06-01

Based on the well-known pharmaceutical excipient potential of poly(vinyl alcohol) (PVA) and clinical success of hydroxyapatite (HAp), the objective of this work was to fabricate functionalized composite microgranules. PVA was modified with succinic anhydride to introduce carboxyl groups (-COOH), respectively, by reaction between the -OH groups of PVA and succinic anhydride, for attachment of drug molecules. For the first time, the functionalized composite microgranules containing HAp/PVA in the ratio of 1:1 were prepared through in situ precipitation of HAp in modified PVA aqueous solutions followed by spray drying of obtained suspensions. The microgranules were characterized by Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and differential scanning calorimetry (DSC). The presence of -COOH groups was verified by FT-IR, and the amount of functional groups added to PVA molecules (averaging 15 mol%) was determined by nuclear magnetic resonance spectroscopy (NMR). DSC results showed that modification with -COOH groups slightly decreased the thermal stability of PVA. FT-IR and XRD analysis confirmed that the resulting composites contain mainly nanocrystalline HAp and PVA. Moreover, the images taken by FE-SEM revealed that the microgranules consisted of nanosized HAp crystallites homogenously embedded in the PVA matrix. DSC measurements indicated that decomposition mechanism of the HAp/PVA differs from that of pure PVA and occurs at lower temperatures. However, the presence of HAp had minor influence on the thermal decomposition of the PVA modified with succinic anhydride. The investigation of composite microgranules confirmed interaction and integration between the HAp and PVA.

Covalent attachment and growth of nanocrystalline films of photocatalytic TiOF2

NASA Astrophysics Data System (ADS)

Zhu, Jian; Lv, Fujian; Xiao, Shengxiong; Bian, Zhenfeng; Buntkowsky, Gerd; Nuckolls, Colin; Li, Hexing

2014-11-01

This manuscript describes a synthesis of nanocrystalline TiOF2 film. The nanocrystalline TiOF2 becomes chemically attached to the surface of the glass slide. These films are robust and can be recycled as photocatalysts for the degradation of organic dyes and solvents. These films also have significant antibacterial properties upon irradiation.This manuscript describes a synthesis of nanocrystalline TiOF2 film. The nanocrystalline TiOF2 becomes chemically attached to the surface of the glass slide. These films are robust and can be recycled as photocatalysts for the degradation of organic dyes and solvents. These films also have significant antibacterial properties upon irradiation. Electronic supplementary information (ESI) available: Methods for sample preparation, characterization and Fig. S1-S8. See DOI: 10.1039/c4nr05598e

Liquid-liquid two phase systems for the production of porous hydrogels and hydrogel microspheres for biomedical applications: A tutorial review

PubMed Central

Elbert, Donald L.

2010-01-01

Macroporous hydrogels may have direct applications in regenerative medicine as scaffolds to support tissue formation. Hydrogel microspheres may be used as drug delivery vehicles or as building blocks to assemble modular scaffolds. A variety of techniques exist to produce macroporous hydrogels and hydrogel microspheres. A subset of these relies on liquid-liquid two phase systems. Within this subset, vastly different types of polymerization processes are found. In this review, the history, terminology and classification of liquid-liquid two phase polymerization and crosslinking are described. Instructive examples of hydrogel microsphere and macroporous scaffold formation by precipitation/dispersion, emulsion and suspension polymerizations are used to illustrate the nature of these processes. The role of the kinetics of phase separation in determining the morphology of scaffolds and microspheres is also delineated. Brief descriptions of miniemulsion, microemulsion polymerization and ionotropic gelation are also included. PMID:20659596

Soft poly(2-chloroaniline)/pectin hydrogel and its electromechanical properties.

PubMed

Kongkaew, Wanar; Sangwan, Watchara; Lerdwijitjarud, Wanchai; Sirivat, Anuvat

2018-01-01

Pectin hydrogels were successfully fabricated with various physical crosslinkers and concentrations for soft actuator applications. A small amount of synthesized P2ClAn was added as a dispersed phase into the pectin matrix. The electromechanical properties of the pectin hydrogels and blends were investigated under the effects of electric field strength, ionic crosslinker type and concentration, and P2ClAn concentration. The electromechanical properties of the pectin hydrogel as crosslinked by Fe 2+ were superior to other pectin hydrogels. The pristine pectin hydrogel and the P2ClAn/Pectin hydrogel blended with 0.10%v/v P2ClAn provided the high storage modulus sensitivity values of 8.61 and 14.01, respectively, under the electric field strength of 800 V/mm. The P2ClAn/Pectin hydrogel blend responded to the electric field with higher dielectrophoretic forces, but lower deflections relative to the pristine pectin hydrogel due to the additional P2ClAn polarization and the latter lower rigidity.

Ciprofloxacin as ocular liposomal hydrogel.

PubMed

Hosny, Khaled Mohamed

2010-03-01

The purpose of this study was to prepare and characterize an ocular effective prolonged-release liposomal hydrogel formulation containing ciprofloxacin. Reverse-phase evaporation was used for preparation of liposomes consisting of soybean phosphatidylcholine (PC) and cholesterol (CH). The effect of PC/CH molar ratio on the percentage drug encapsulation was investigated. The effect of additives such as stearylamine (SA) or dicetyl phosphate (DP) as positive and negative charge inducers, respectively, were studied. Morphology, mean size, encapsulation efficiency, and in vitro release of ciprofloxacin from liposomes were evaluated. For hydrogel preparation, Carbopol 940 was applied. In vitro transcorneal permeation through excised albino rabbit cornea was also determined. Optimal encapsulation efficiency of 73.04 +/- 3.06% was obtained from liposomes formulated with PC/CH at molar ratio of 5:3 and by increasing CH content above this limit, the encapsulation decreased. Positively charged liposomes showed superior entrapment efficiency (82.01 +/- 0.52) over the negatively charged and the neutral liposomes. Hydrogel containing liposomes with lipid content PC, CH, and SA in molar ratio 5:3:1, respectively, showed the best release and transcorneal permeation with the percentage permeation of 30.6%. These results suggest that the degree of encapsulation of ciprofloxacin into liposomes and prolonged in vitro release depend on composition of the vesicles. In addition, the polymer hydrogel used in preparation ensure steady and prolonged transcorneal permeation. In conclusion, ciprofloxacin liposomal hydrogel is a suitable delivery system for improving the ocular bioavailability of ciprofloxacin.

Thermodynamic model for polyelectrolyte hydrogels.

PubMed

Arndt, Markus C; Sadowski, Gabriele

2014-09-04

The composition and swelling behavior of hydrogels may be dramatically influenced by external stimuli. Polyelectrolyte hydrogels consisting of charged polymers are particularly well-known for a high sensitivity to the presence of ionic species. For a thermodynamic description of such systems, the polyelectrolyte Perturbed-Chain Statistical Association Fluid Theory (pePC-SAFT) equation of state was augmented and merged with an extension of the modeling of hydrogels. This combined approach allowed for two effects to be taken into account: first, charges along the polymer chain and their interaction with mobile ions of the same or opposite charge in aqueous solutions and, second, the elastic interactions of swellable networks and their effect on Helmholtz energy and pressure. Thus, predictions of the degree of counterion condensation on the polymer chains could be made both for vapor-liquid equilibria of aqueous polyelectrolyte solutions and for polyelectrolyte hydrogels in aqueous salt solutions. The influence of temperature and molecular weight thereon was predicted successfully, and the impact of the degree of neutralization and the effect of additional salts were examined in comparison to literature data. With the inclusion of the influence of the Donnan potential, our model gave good predictions of swellable polyelectrolyte hydrogel systems in salt solutions. Poly(acrylic acid) and poly(methacrylic acid) gels were studied along with their corresponding sodium salts. Their swelling behavior in aqueous NaCl and NaNO3 solutions was examined.

Functional nucleic acid-based hydrogels for bioanalytical and biomedical applications

PubMed Central

Mo, Liuting; Lu, Chun-Hua; Fu, Ting

2016-01-01

Hydrogels are crosslinked hydrophilic polymers that can absorb a large amount of water. By their hydrophilic, biocompatible and highly tunable nature, hydrogels can be tailored for applications in bioanalysis and biomedicine. Of particular interest are DNA-based hydrogels owing to the unique features of nucleic acids. Since the discovery of DNA double helical structure, interest in DNA has expanded beyond its genetic role to applications in nanotechnology and materials science. In particular, DNA-based hydrogels present such remarkable features as stability, flexibility, precise programmability, stimuli-responsive DNA conformations, facile synthesis and modification. Moreover, functional nucleic acids (FNAs) have allowed the construction of hydrogels based on aptamers, DNAzymes, i-motif nanostructures, siRNAs and CpG oligodeoxynucleotides to provide additional molecular recognition, catalytic activities and therapeutic potential, making them key players in biological analysis and biomedical applications. To date, a variety of applications have been demonstrated with FNA-based hydrogels, including biosensing, environmental analysis, controlled drug release, cell adhesion and targeted cancer therapy. In this review, we focus on advances in the development of FNA-based hydrogels, which have fully incorporated both the unique features of FNAs and DNA-based hydrogels. We first introduce different strategies for constructing DNA-based hydrogels. Subsequently, various types of FNAs and the most recent developments of FNA-based hydrogels for bioanalytical and biomedical applications are described with some selected examples. Finally, the review provides an insight into the remaining challenges and future perspectives of FNA-based hydrogels. PMID:26758955

C-Axis-Oriented Hydroxyapatite Film Grown Using ZnO Buffer Layer

NASA Astrophysics Data System (ADS)

Sakoishi, Yasuhiro; Iguchi, Ryo; Nishikawa, Hiroaki; Hontsu, Shigeki; Hayami, Takashi; Kusunoki, Masanobu

2013-11-01

A method of fabricating c-axis-oriented hydroxyapatite film on a quartz crystal microbalance (QCM) sensor was investigated. ZnO was used as a template to obtain a hexagonal hydroxyapatite crystal of uniaxial orientation. The ZnO was grown as a c-axis film on a Au/quartz with the surface structure of a QCM sensor. Under optimized conditions, hydroxyapatite was deposited by pulsed laser deposition. X-ray diffraction showed the hydroxyapatite film to be oriented along the c-axis. Because Au and ZnO are applied to many devices, the anisotropic properties of hydroxyapatite may be incorporated into these devices as well as QCM sensors.

The hydroxyapatite-binding regions of a rat salivary glycoprotein.

PubMed

Embery, G; Green, D R

1989-09-01

The regions of a salivary sulphated glycoprotein which are involved in its attachment to hydroxyapatite (Biogel HTP) have been characterised. The sulphated glycoprotein, a 35S-labelled preparation from mixed palatal and buccal minor gland secretions of the rat was bound onto hydroxyapatite and the resultant glycoprotein-hydroxyapatite complex was sequentially digested with pronase E and alpha-L-fucosidase, a treatment which released 86.8% +/- 1.7% of the radioactivity of the initially bound glycoprotein. The fragments which remained attached to the hydroxyapatite after enzymic digestion were fractionated on Sephadex G-25 and analysed for carbohydrate and amino acid components. A range of amino acids were detected which could reflect both glycosylated and non-glycosylated-binding regions. Sialic acid, although considered to be involved in the attachment process was not detected in any of the fragments remaining after enzymic digestion, a finding which provides indirect evidence that the enzymically liberated products do not subsequently re-attach to the hydroxyapatite surface. The notable feature of the fractions with average Mr estimated at 1000 or less is the high proportion of N-acetylhexosamine and N-acetylgalactosamine. It is apparent that the hexosamine residues, which normally bear the ester sulphate moieties of sulphated glycoproteins, play an important role in the attachment of sulphated glycoproteins to hydroxyapatite.

Evaluation of the interaction between hydroxyapatite and bisphosphonate by nonlinear capillary electrochromatography.

PubMed

Kong, Deying; Chen, Zilin

2017-05-01

Bisphosphonates are a class of chemical compounds used to treat diseases caused by increased bone resorption. Zoledronate is a third-generation bisphosphonate drug. Hydroxyapatite is main mineral constituent of bones, which can be bound by bisphosphonates in vivo. In this work, we report a method of nonlinear capillary electrochromatography for study on the interaction between hydroxyapatite and bisphosphonate. Hydroxyapatite was modified on the inner wall of capillary by a biomimetic-mineralization method. Then nonlinear chromatography was used to fit and analyze the interaction between zoledronate and hydroxyapatite. The association rate constants of zoledronate in hydroxyapatite-modified capillary and bare capillary are 642.3 and 195/M/min, respectively. This indicates that there is strong binding interactions and affinity between zoledronate and hydroxyapatite. Besides, the interaction between zoledronate and hydroxyapatite was confirmed further by ultraviolet spectroscopy. The method of nonlinear capillary electrochromatography provides a fast and effect approach for studying of bone metabolism disease by evaluation of interaction between hydroxyapatite and bisphosphonates. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Characterization and inhibitive study of gel-grown hydroxyapatite crystals at physiological temperature

NASA Astrophysics Data System (ADS)

Parekh, Bharat; Joshi, Mihir; Vaidya, Ashok

2008-04-01

Hydroxyapatite is very useful for various biomedical applications, due to its chemical similarity with mineralized bone of human. Hydroxyapatite is also responsible for arthropathy (joint disease). In the present study, the growth of hydroxyapatite crystals was carried out by using single-diffusion gel growth technique in silica hydro gel media, at physiological temperature. The growth of hydroxyapatite crystals under slow and controlled environment in gel medium can be simulated in a simple manner to the growth in human body. The crystals, formed in the Liesegang rings, were characterized by powder XRD, FTIR and dielectric study. The diffusion study is also carried out for the hydroxyapatite crystals using the moving boundary model. The inhibitive influence of various Ayurvedic medicinal plant extracts such as Boswellia serrata gum resin , Tribulus terrestris fruits, Rotula aquatica roots, Boerhaavia diffusa roots and Commiphora wightii, on the growth of hydroxyapatite was studied. Roots of R. aquatica and B. diffusa show some inhibition of the hydroxyapatite crystals in vitro. This preclinical study will be helpful to design the therapy for prevention of hydroxyapatite-based ailments.

Improvement of the stability of hydroxyapatite through glass ceramic reinforcement.

PubMed

Ha, Na Ra; Yang, Zheng Xun; Hwang, Kyu Hong; Kim, Tae Suk; Lee, Jong Kook

2010-05-01

Hydroxyapatite has achieved significant application in orthopedic and dental implants due to its excellent biocompatibility. Sintered hydroxyapatites showed significant dissolution, however, after their immersion in water or simulated body fluid (SBF). This grain boundary dissolution, even in pure hydroxyapatites, resulted in grain separation at the surfaces, and finally, in fracture. In this study, hydroxyapatite ceramics containing apatite-wollastonite (AW) or calcium silicate (SG) glass ceramics as additives were prepared to prevent the dissolution. AW and SG glass ceramics were added at 0-7 wt% and powder-compacted uniaxially followed by firing at moisture conditions. The glass phase was incorporated into the hydroxyapatite to act as a sintering aid, followed by crystallization, to improve the mechanical properties without reducing the biocompatibility. As seen in the results of the dissolution test, a significant amount of damage was reduced even after more than 14 days. TEM and SEM showed no decomposition of HA to the secondary phase, and the fracture toughness increased, becoming even higher than that of the commercial hydroxyapatite.

Classification, processing and application of hydrogels: A review.

PubMed

Ullah, Faheem; Othman, Muhammad Bisyrul Hafi; Javed, Fatima; Ahmad, Zulkifli; Md Akil, Hazizan

2015-12-01

This article aims to review the literature concerning the choice of selectivity for hydrogels based on classification, application and processing. Super porous hydrogels (SPHs) and superabsorbent polymers (SAPs) represent an innovative category of recent generation highlighted as an ideal mould system for the study of solution-dependent phenomena. Hydrogels, also termed as smart and/or hungry networks, are currently subject of considerable scientific research due to their potential in hi-tech applications in the biomedical, pharmaceutical, biotechnology, bioseparation, biosensor, agriculture, oil recovery and cosmetics fields. Smart hydrogels display a significant physiochemical change in response to small changes in the surroundings. However, such changes are reversible; therefore, the hydrogels are capable of returning to its initial state after a reaction as soon as the trigger is removed. Copyright © 2015 Elsevier B.V. All rights reserved.

Nutrient-substituted hydroxyapatites: synthesis and characterization

NASA Technical Reports Server (NTRS)

Golden, D. C.; Ming, D. W.

1999-01-01

Incorporation of Mg, S, and plant-essential micronutrients into the structure of synthetic hydroxyapatite (HA) may be advantageous for closed-loop systems, such as will be required on Lunar and Martian outposts, because these apatites can be used as slow-release fertilizers. Our objective was to synthesize HA with Ca, P, Mg, S, Fe, Cu, Mn, Zn, Mo, B, and Cl incorporated into the structure, i.e., nutrient-substituted apatites. Hydroxyapatite, carbonate hydroxyapatite (CHA), nutrient-substituted hydroxyapatite (NHA), and nutrient-substituted carbonate hydroxyapatite (NCHA) were synthesized by precipitating from solution. Chemical and mineralogical analysis of precipitated samples indicated a considerable fraction of the added cations were incorporated into HA, without mineral impurities. Particle size of the HA was in the 1 to 40 nm range, and decreased with increased substitution of nutrient elements. The particle shape of HA was elongated in the c-direction in unsubstituted HA and NHA but more spherical in CHA and NCHA. The substitution of cations and anions in the HA structure was confirmed by the decrease of the d[002] spacing of HA with substitution of ions with an ionic radius less than that of Ca or P. The DTPA-extractable Cu ranged from 8 to 8429 mg kg-1, Zn ranged from 57 to 1279 mg kg-1, Fe from 211 to 2573 mg kg-1, and Mn from 190 to 1719 mg kg-1, depending on the substitution level of each element in HA. Nutrient-substituted HA has the potential to be used as a slow-release fertilizer to supply micronutrients, S, and Mg in addition to Ca and P.

Electrical impedance spectroscopy of neutron-irradiated nanocrystalline silicon carbide (3C-SiC)

NASA Astrophysics Data System (ADS)

Huseynov, Elchin M.

2018-01-01

It the present work, impedance spectra of nanocrystalline 3C-SiC particles have been comparatively analyzed before and after neutron irradiation. Resonance states and shifts were observed at the impedance spectra of nanocrystalline 3C-SiC particles after neutron irradiation. Relaxation time has been calculated from interdependence of real and imaginary parts of impedance of nanocrystalline 3C-SiC particles. Calculated relaxation times have been investigated as a function of neutron irradiation period. Neutron transmutation (31P isotopes production) effects on the impedance spectra and relaxation times have been studied. Moreover, influence of agglomeration and amorphous transformation to the impedance spectra and relaxation times of nanocrystalline 3C-SiC particles have been investigated.

Preparation, optimization and property of PVA-HA/PAA composite hydrogel.

PubMed

Chen, Kai; Liu, Jinlong; Yang, Xuehui; Zhang, Dekun

2017-09-01

PVA-HA/PAA composite hydrogel is prepared by freezing-thawing, PEG dehydration and annealing method. Orthogonal design method is used to choose the optimization combination. Results showed that HA and PVA have the maximum effect on water content. PVA and freezing-thawing cycles have the maximum effect on creep resistance and stress relaxation rate of hydrogel. Annealing temperature and freezing-thawing cycles have the maximum effect on compressive elastic modulus of hydrogel. Comparing with the water content and mechanical properties of 16 kinds of combination, PVA-HA/PAA composite hydrogel with freezing-thawing cycles of 3, annealing temperature of 120°C, PVA of 16%, HA of 2%, PAA of 4% has the optimization comprehensive properties. PVA-HA/PAA composite hydrogel has a porous network structure. There are some interactions between PVA, HA and PAA in hydrogel and the properties of hydrogel are strengthened. The annealing treatment improves the crystalline and crosslinking of hydrogel. Therefore, the annealing PVA-HA/PAA composite hydrogel has good thermostability, strength and mechanical properties. It also has good lubrication property and its friction coefficient is relative low. Copyright © 2017 Elsevier B.V. All rights reserved.

Poroelasticity-driven lubrication in hydrogel interfaces.

PubMed

Reale, Erik R; Dunn, Alison C

2017-01-04

It is widely accepted that hydrogel surfaces are slippery, and have low friction, but dynamic applied stresses alter the hydrogel composition at the interface as water is displaced. The induced osmotic imbalance of compressed hydrogel which cannot swell to equilibrium should drive the resistance to slip against it. This paper demonstrates the driving role of poroelasticity in the friction of hydrogel-glass interfaces, specifically how poroelastic relaxation of hydrogels increases adhesion. We translate the work of adhesion into an effective surface energy density that increases with the duration of applied pressure from 10 to 50 mJ m -2 , as measured by micro-indentation. A model of static friction coefficient is derived from an area-based rules of mixture for the surface energies, and predicts the friction coefficient changes upon initiation of slip. For kinetic friction, the competition between duration of contact and relaxation time is quantified by a contacting Péclet number, Pe C . A single length parameter on the scale of micrometers fits these two models to experimental micro-friction data. These models predict how short durations of applied pressure and faster sliding speeds, do not disrupt interfacial hydration; this prevailing water maintains low friction. At low speeds where interface drainage dominates, the osmotic suction works against slip for higher friction. The prediction of friction coefficients after adhesion characterization by micro-indentation makes use of the interplay between poroelasticity, adhesion, and friction. This approach provides a starting point for prediction of, and design for, hydrogel interfacial friction.

Stimulus-responsive hydrogels: Theory, modern advances, and applications

PubMed Central

Koetting, Michael C.; Peters, Jonathan T.; Steichen, Stephanie D.; Peppas, Nicholas A.

2016-01-01

Over the past century, hydrogels have emerged as effective materials for an immense variety of applications. The unique network structure of hydrogels enables very high levels of hydrophilicity and biocompatibility, while at the same time exhibiting the soft physical properties associated with living tissue, making them ideal biomaterials. Stimulus-responsive hydrogels have been especially impactful, allowing for unprecedented levels of control over material properties in response to external cues. This enhanced control has enabled groundbreaking advances in healthcare, allowing for more effective treatment of a vast array of diseases and improved approaches for tissue engineering and wound healing. In this extensive review, we identify and discuss the multitude of response modalities that have been developed, including temperature, pH, chemical, light, electro, and shear-sensitive hydrogels. We discuss the theoretical analysis of hydrogel properties and the mechanisms used to create these responses, highlighting both the pioneering and most recent work in all of these fields. Finally, we review the many current and proposed applications of these hydrogels in medicine and industry. PMID:27134415

Silver film on nanocrystalline TiO{sub 2} support: Photocatalytic and antimicrobial ability

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

Vukoje, Ivana D., E-mail: ivanav@vinca.rs; Tomašević-Ilić, Tijana D., E-mail: tommashev@gmail.com; Zarubica, Aleksandra R., E-mail: zarubica2000@yahoo.com

Highlights: • Simple photocatalytic rout for deposition of Ag on nanocrystalline TiO{sub 2} films. • High antibactericidal efficiency of deposited Ag on TiO{sub 2} support. • Improved photocatalytic performance of TiO{sub 2} films in the presence of deposited Ag. - Abstract: Nanocrystalline TiO{sub 2} films were prepared on glass slides by the dip coating technique using colloidal solutions consisting of 4.5 nm particles as a precursor. Photoirradiation of nanocrystalline TiO{sub 2} film modified with alanine that covalently binds to the surface of TiO{sub 2} and at the same time chelate silver ions induced formation of metallic silver film. Optical andmore » morphological properties of thin silver films on nanocrystalline TiO{sub 2} support were studied by absorption spectroscopy and atomic force microscopy. Improvement of photocatalytic performance of nanocrystalline TiO{sub 2} films after deposition of silver was observed in degradation reaction of crystal violet. Antimicrobial ability of deposited silver films on nanocrystalline TiO{sub 2} support was tested in dark as a function of time against Escherichia coli, Staphylococcus aureus, and Candida albicans. The silver films ensured maximum cells reduction of both bacteria, while the fungi reduction reached satisfactory 98.45% after 24 h of contact.« less

Direct Coating of Nanocrystalline Diamond on Steel

NASA Astrophysics Data System (ADS)

Tsugawa, Kazuo; Kawaki, Shyunsuke; Ishihara, Masatou; Hasegawa, Masataka

2012-09-01

Nanocrystalline diamond films have been successfully deposited on stainless steel substrates without any substrate pretreatments to promote diamond nucleation, including the formation of interlayers. A low-temperature growth technique, 400 °C or lower, in microwave plasma chemical vapor deposition using a surface-wave plasma has cleared up problems in diamond growth on ferrous materials, such as the surface graphitization, long incubation time, substrate softening, and poor adhesion. The deposited nanocrystalline diamond films on stainless steel exhibit good adhesion and tribological properties, such as a high wear resistance, a low friction coefficient, and a low aggression strength, at room temperature in air without lubrication.

Injectable Hydrogels for Cardiac Tissue Repair after Myocardial Infarction

PubMed Central

Khattab, Ahmad; Islam, Mohammad Ariful; Hweij, Khaled Abou; Zeitouny, Joya; Waters, Renae; Sayegh, Malek; Hossain, Md Monowar; Paul, Arghya

2015-01-01

Cardiac tissue damage due to myocardial infarction (MI) is one of the leading causes of mortality worldwide. The available treatments of MI include pharmaceutical therapy, medical device implants, and organ transplants, all of which have severe limitations including high invasiveness, scarcity of donor organs, thrombosis or stenosis of devices, immune rejection, and prolonged hospitalization time. Injectable hydrogels have emerged as a promising solution for in situ cardiac tissue repair in infarcted hearts after MI. In this review, an overview of various natural and synthetic hydrogels for potential application as injectable hydrogels in cardiac tissue repair and regeneration is presented. The review starts with brief discussions about the pathology of MI, its current clinical treatments and their limitations, and the emergence of injectable hydrogels as a potential solution for post MI cardiac regeneration. It then summarizes various hydrogels, their compositions, structures and properties for potential application in post MI cardiac repair, and recent advancements in the application of injectable hydrogels in treatment of MI. Finally, the current challenges associated with the clinical application of injectable hydrogels to MI and their potential solutions are discussed to help guide the future research on injectable hydrogels for translational therapeutic applications in regeneration of cardiac tissue after MI. PMID:27668147

Hierarchical nanostructured conducting polymer hydrogel with high electrochemical activity

PubMed Central

Pan, Lijia; Yu, Guihua; Zhai, Dongyuan; Lee, Hye Ryoung; Zhao, Wenting; Liu, Nian; Wang, Huiliang; Tee, Benjamin C.-K.; Shi, Yi; Cui, Yi; Bao, Zhenan

2012-01-01

Conducting polymer hydrogels represent a unique class of materials that synergizes the advantageous features of hydrogels and organic conductors and have been used in many applications such as bioelectronics and energy storage devices. They are often synthesized by polymerizing conductive polymer monomer within a nonconducting hydrogel matrix, resulting in deterioration of their electrical properties. Here, we report a scalable and versatile synthesis of multifunctional polyaniline (PAni) hydrogel with excellent electronic conductivity and electrochemical properties. With high surface area and three-dimensional porous nanostructures, the PAni hydrogels demonstrated potential as high-performance supercapacitor electrodes with high specific capacitance (∼480 F·g-1), unprecedented rate capability, and cycling stability (∼83% capacitance retention after 10,000 cycles). The PAni hydrogels can also function as the active component of glucose oxidase sensors with fast response time (∼0.3 s) and superior sensitivity (∼16.7 μA·mM-1). The scalable synthesis and excellent electrode performance of the PAni hydrogel make it an attractive candidate for bioelectronics and future-generation energy storage electrodes. PMID:22645374

Hydrogel Walkers with Electro-Driven Motility for Cargo Transport.

PubMed

Yang, Chao; Wang, Wei; Yao, Chen; Xie, Rui; Ju, Xiao-Jie; Liu, Zhuang; Chu, Liang-Yin

2015-08-28

In this study, soft hydrogel walkers with electro-driven motility for cargo transport have been developed via a facile mould-assisted strategy. The hydrogel walkers consisting of polyanionic poly(2-acrylamido-2-methylpropanesulfonic acid-co-acrylamide) exhibit an arc looper-like shape with two "legs" for walking. The hydrogel walkers can reversibly bend and stretch via repeated "on/off" electro-triggers in electrolyte solution. Based on such bending/stretching behaviors, the hydrogel walkers can move their two "legs" to achieve one-directional walking motion on a rough surface via repeated "on/off" electro-triggering cycles. Moreover, the hydrogel walkers loaded with very heavy cargo also exhibit excellent walking motion for cargo transport. Such hydrogel systems create new opportunities for developing electro-controlled soft systems with simple design/fabrication strategies in the soft robotic field for remote manipulation and transportation.

Biodegradation of PVP-CMC hydrogel film: a useful food packaging material.

PubMed

Roy, Niladri; Saha, Nabanita; Kitano, Takeshi; Saha, Petr

2012-06-20

Hydrogels can offer new opportunities for the design of efficient packaging materials with desirable properties (i.e. durability, biodegradability and mechanical strength). It is a promising and emerging concept, as most of the biopolymer based hydrogels are supposed to be biodegradable, they can be considered as alternative eco-friendly packaging materials. This article reports about synthetic (polyvinylpyrrolidone (PVP)) and biopolymer (carboxymethyl cellulose (CMC)) based a novel hydrogel film and its nature of biodegradability under controlled environmental condition. The dry hydrogel films were prepared by solution casting method and designated as 'PVP-CMC hydrogel films'. The hydrogel film containing PVP and CMC in a ratio of 20:80 shows best mechanical properties among all the test samples (i.e. 10:90, 20:80, 50:50, 80:20 and 90:10). Thus, PVP-CMC hydrogel film of 20:80 was considered as a useful food packaging material and further experiments were carried out with this particular hydrogel film. Biodegradation of the PVP-CMC hydrogel films were studied in liquid state (Czapec-Dox liquid medium+soil extracts) until 8 weeks. Variation in mechanical, viscoelastic properties and weight loss of the hydrogel films with time provide the direct evidence of biodegradation of the hydrogels. About 38% weight loss was observed within 8 weeks. FTIR spectra of the hydrogel films (before and after biodegradation) show shifts of the peaks and also change in the peak intensities, which refer to the physico-chemical change in the hydrogel structure and SEM views of the hydrogels show how internal structure of the PVP-CMC film changes in the course of biodegradation. Copyright © 2012 Elsevier Ltd. All rights reserved.

Chiral betulin-imino-chitosan hydrogels by dynamic covalent sonochemistry.

PubMed

Iftime, Manuela Maria; Marin, Luminita

2018-07-01

A series of chiral hydrogels was prepared from a homogeneous mixture of chitosan and betulinic aldehyde in different molar ratios, under the effect of ultrasound. The hydrogelation mechanism has been investigated by FTIR and CD spectroscopy, wide angle X-ray diffraction and polarized light microscopy. The morphology of hydrogels was examined by SEM. The swelling ability has been tested in three media of different pH. It was concluded that hydrogelation occurred by different pathways, closely related to the peculiarities of the chitosan-betulin systems. Circular dichroism measurements revealed chiroptical properties of the hydrogels, correlated to their content and crosslinking pathway. Copyright © 2018 Elsevier B.V. All rights reserved.

Heterogeneous nucleation of hydroxyapatite on protein: structural effect of silk sericin

PubMed Central

Takeuchi, Akari; Ohtsuki, Chikara; Miyazaki, Toshiki; Kamitakahara, Masanobu; Ogata, Shin-ichi; Yamazaki, Masao; Furutani, Yoshiaki; Kinoshita, Hisao; Tanihara, Masao

2005-01-01

Acidic proteins play an important role during mineral formation in biological systems, but the mechanism of mineral formation is far from understood. In this paper, we report on the relationship between the structure of a protein and hydroxyapatite deposition under biomimetic conditions. Sericin, a type of silk protein, was adopted as a suitable protein for studying structural effect on hydroxyapatite deposition, since it forms a hydroxyapatite layer on its surface in a metastable calcium phosphate solution, and its structure has been reported. Sericin effectively induced hydroxyapatite nucleation when it has high molecular weight and a β sheet structure. This indicates that the specific structure of a protein can effectively induce heterogeneous nucleation of hydroxyapatite in a biomimetic solution, i.e. a metastable calcium phosphate solution. This finding is useful in understanding biomineralization, as well as for the design of organic polymers that can effectively induce hydroxyapatite nucleation. PMID:16849195

Structural characterization of nanocrystalline cadmium sulphide powder prepared by solvent evaporation technique

NASA Astrophysics Data System (ADS)

Pandya, Samir; Tandel, Digisha; Chodavadiya, Nisarg

2018-05-01

CdS is one of the most important compounds in the II-VI group of semiconductor. There are numerous applications of CdS in the form of nanoparticles and nanocrystalline. Semiconductors nanoparticles (also known as quantum dots), belong to state of matter in the transition region between molecules and solids, have attracted a great deal of attention because of their unique electrical and optical properties, compared to bulk materials. In the field of optoelectronic, nanocrystalline form utilizes mostly in the field of catalysis and fluid technology. Considering these observations, presented work had been carried out, i.e. based on the nanocrystalline material preparation. In the present work CdS nano-crystalline powder was synthesized by a simple and cost effective chemical technique to grow cadmium sulphide (CdS) nanoparticles at 200 °C with different concentrations of cadmium. The synthesis parameters were optimized. The synthesized powder was structurally characterized by X-ray diffraction and particle size analyzer. In the XRD analysis, Micro-structural parameters such as lattice strain, dislocation density and crystallite size were analysed. The broadened diffraction peaks indicated nanocrystalline particles of the film material. In addition to that the size of the prepared particles was analyzed by particle size analyzer. The results show the average size of CdS particles ranging from 80 to 100 nm. The overall conclusion of the work can be very useful in the synthesis of nanocrystalline CdS powder.

Enzymatic Inverse Opal Hydrogel Particles for Biocatalyst.

PubMed

Wang, Huan; Gu, Hongcheng; Chen, Zhuoyue; Shang, Luoran; Zhao, Ze; Gu, Zhongze; Zhao, Yuanjin

2017-04-19

Enzymatic carriers have a demonstrated value for chemical reactions and industrial applications. Here, we present a novel kind of inverse opal hydrogel particles as the enzymatic carriers. The particles were negatively replicated from spherical colloidal crystal templates by using magnetic nanoparticles tagged acrylamide hydrogel. Thus, they were endowed with the features of monodispersity, small volume, complete penetrating structure, and controllable motion, which are all beneficial for improving the efficiency of biocatalysis. In addition, due to the ordered porous nanostructure, the inverse opal hydrogel particles were imparted with unique photonic band gaps (PBGs) and vivid structural colors for encoding varieties of immobilized enzymes and for constructing a multienzymes biocatalysis system. These features of the inverse opal hydrogel particles indicate that they are ideal enzymatic carriers for biocatalysis.

Hydroxyapatite Growth Inhibition Effect of Pellicle Statherin Peptides.

PubMed

Xiao, Y; Karttunen, M; Jalkanen, J; Mussi, M C M; Liao, Y; Grohe, B; Lagugné-Labarthet, F; Siqueira, W L

2015-08-01

In our recent studies, we have shown that in vivo-acquired enamel pellicle is a sophisticated biological structure containing a significant portion of naturally occurring salivary peptides. From a functional aspect, the identification of peptides in the acquired enamel pellicle is of interest because many salivary proteins exhibit functional domains that maintain the activities of the native protein. Among the in vivo-acquired enamel pellicle peptides that have been newly identified, 5 peptides are derived from statherin. Here, we assessed the ability of these statherin pellicle peptides to inhibit hydroxyapatite crystal growth. In addition, atomistic molecular dynamics (MD) simulations were performed to better understand the underlying physical mechanisms of hydroxyapatite growth inhibition. A microplate colorimetric assay was used to quantify hydroxyapatite growth. Statherin protein, 5 statherin-derived peptides, and a peptide lacking phosphate at residues 2 and 3 were analyzed. Statherin peptide phosphorylated on residues 2 and 3 indicated a significant inhibitory effect when compared with the 5 other peptides (P < 0.05). MD simulations showed a strong affinity and fast adsorption to hydroxyapatite for phosphopeptides, whereas unphosphorylated peptides interacted weakly with the hydroxyapatite. Our data suggest that the presence of a covalently linked phosphate group (at residues 2 and 3) in statherin peptides modulates the effect of hydroxyapatite growth inhibition. This study provides a mechanism to account for the composition and function of acquired enamel pellicle statherin peptides that will contribute as a base for the development of biologically stable and functional synthetic peptides for therapeutic use against dental caries and/or periodontal disease. © International & American Associations for Dental Research 2015.

Bulk Nanocrystalline Metals: Review of the Current State of the Art and Future Opportunities for Copper and Copper Alloys

DTIC Science & Technology

2014-05-13

nanocrystalline materials using mechanical alloying, the alloy development and synthesis process for stabilizing these materials at elevated temperatures, and...the physical and mechanical properties of nanocrystalline materials with a focus throughout on nanocrystalline copper and a nanocrystalline Cu-Ta...approaches as well as experimental results for grain growth, grain boundary processes, and deformation mechanisms in nanocrystalline copper are

Polyvinyl alcohol hydrogels for iontohporesis

NASA Astrophysics Data System (ADS)

Bera, Prasanta; Alam, Asif Ali; Arora, Neha; Tibarewala, Dewaki Nandan; Basak, Piyali

2013-06-01

Transdermal therapeutic systems propound controlled release of active ingredients through the skin into the systemic circulation in a predictive manner. Drugs administered through these systems escape first-pass metabolism and maintain a steady state scenario similar to a continuous intravenous infusion for up to several days. The iontophoresis deal with the systemic delivery of the bioactive agents (drug) by applying an electric current. It is basically an injection without the needle. The iontophoretic system requires a gel-based matrix to accommodate the bioactive agent. Hydrogels have been used by many investigators in controlled-release drug delivery systems because of their good tissue compatibility and easy manipulation of swelling level and, thereby, solute permeability. In this work we have prepared polyvinyl alcohol (PVA) hydrogel. We have cross linked polyvinyl alcohol chemically with Glutaraldehyde with different wt%. FTIR study reveals the chemical changes during cross linking. Swelling in water, is done to have an idea about drug loading and drug release from the membrane. After drug loading to the hydrogels, we have studied the drug release property of the hydrogels using salicylic acid as a model drug.

Electrode characteristics of nanocrystalline AB{sub 5} compounds prepared by mechanical alloying

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

Chen, Z.; Chen, Z.; Zhou, D.

1998-10-01

Nanocrystalline LaNi{sub 5} and LaNi{sub 4.5}Si{sub 0.5} synthesized by mechanical alloying were used as negative materials for Ni-MH batteries. It was found that the electrodes prepared with the nanocrystalline powders had similar discharge capacities, better activation behaviors, and longer cycle lifetimes, compared with the negative electrode prepared with polycrystalline coarse-grained LaNi{sub 5} alloy. The properties of the electrodes prepared with these nanocrystalline materials were attributed to the structural characteristics of the compounds caused by mechanical alloying.

Synthesis of nanocrystalline ZnO thin films by electron beam evaporation

NASA Astrophysics Data System (ADS)

Kondkar, V.; Rukade, D.; Bhattacharyya, V.

2018-05-01

Nanocrystalline ZnO thin films have potential for applications in variety of optoelectronic devices. In the present study, nanocrystalline thin films of ZnO are grown on fused silica substrate using electron beam (e-beam) evaporation technique. Phase identification is carried out using Glancing angle X-ray diffraction (GAXRD) and Raman spectroscopy. Ultraviolet-Visible (UV-Vis) spectroscopic analysis is carried out to calculate energy band gap of the ZnO film. Surface morphology of the film is investigated using atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM). Highly quality nanocrystalline thin films of hexagonal wurtzite ZnO are synthesized using e-beam evaporation technique.

Gelam (Melaleuca spp.) Honey-Based Hydrogel as Burn Wound Dressing

PubMed Central

Mohd Zohdi, Rozaini; Abu Bakar Zakaria, Zuki; Yusof, Norimah; Mohamed Mustapha, Noordin; Abdullah, Muhammad Nazrul Hakim

2012-01-01

A novel cross-linked honey hydrogel dressing was developed by incorporating Malaysian honey into hydrogel dressing formulation, cross-linked and sterilized using electron beam irradiation (25 kGy). In this study, the physical properties of the prepared honey hydrogel and its wound healing efficacy on deep partial thickness burn wounds in rats were assessed. Skin samples were taken at 7, 14, 21, and 28 days after burn for histopathological and molecular evaluations. Application of honey hydrogel dressings significantly enhanced (P < 0.05) wound closure and accelerated the rate of re-epithelialization as compared to control hydrogel and OpSite film dressing. A significant decrease in inflammatory response was observed in honey hydrogel treated wounds as early as 7 days after burn (P < 0.05). Semiquantitative analysis using RT-PCR revealed that treatment with honey hydrogel significantly (P < 0.05) suppressed the expression of proinflammatory cytokines (IL-1α, IL-1β, and IL-6). The present study substantiates the potential efficacy of honey hydrogel dressings in accelerating burn wound healing. PMID:21941590

Engineering three-dimensional cell mechanical microenvironment with hydrogels.

PubMed

Huang, Guoyou; Wang, Lin; Wang, Shuqi; Han, Yulong; Wu, Jinhui; Zhang, Qiancheng; Xu, Feng; Lu, Tian Jian

2012-12-01

Cell mechanical microenvironment (CMM) significantly affects cell behaviors such as spreading, migration, proliferation and differentiation. However, most studies on cell response to mechanical stimulation are based on two-dimensional (2D) planar substrates, which cannot mimic native three-dimensional (3D) CMM. Accumulating evidence has shown that there is a significant difference in cell behavior in 2D and 3D microenvironments. Among the materials used for engineering 3D CMM, hydrogels have gained increasing attention due to their tunable properties (e.g. chemical and mechanical properties). In this paper, we provide an overview of recent advances in engineering hydrogel-based 3D CMM. Effects of mechanical cues (e.g. hydrogel stiffness and externally induced stress/strain in hydrogels) on cell behaviors are described. A variety of approaches to load mechanical stimuli in 3D hydrogel-based constructs are also discussed.

Rationally designed synthetic protein hydrogels with predictable mechanical properties.

PubMed

Wu, Junhua; Li, Pengfei; Dong, Chenling; Jiang, Heting; Bin Xue; Gao, Xiang; Qin, Meng; Wang, Wei; Bin Chen; Cao, Yi

2018-02-12

Designing synthetic protein hydrogels with tailored mechanical properties similar to naturally occurring tissues is an eternal pursuit in tissue engineering and stem cell and cancer research. However, it remains challenging to correlate the mechanical properties of protein hydrogels with the nanomechanics of individual building blocks. Here we use single-molecule force spectroscopy, protein engineering and theoretical modeling to prove that the mechanical properties of protein hydrogels are predictable based on the mechanical hierarchy of the cross-linkers and the load-bearing modules at the molecular level. These findings provide a framework for rationally designing protein hydrogels with independently tunable elasticity, extensibility, toughness and self-healing. Using this principle, we demonstrate the engineering of self-healable muscle-mimicking hydrogels that can significantly dissipate energy through protein unfolding. We expect that this principle can be generalized for the construction of protein hydrogels with customized mechanical properties for biomedical applications.

Deposition and characterization of ZnSe nanocrystalline thin films

NASA Astrophysics Data System (ADS)

Temel, Sinan; Gökmen, F. Özge; Yaman, Elif; Nebi, Murat

2018-02-01

ZnSe nanocrystalline thin films were deposited at different deposition times by using the Chemical Bath Deposition (CBD) technique. Effects of deposition time on structural, morphological and optical properties of the obtained thin films were characterized. X-ray diffraction (XRD) analysis was used to study the structural properties of ZnSe nanocrystalline thin films. It was found that ZnSe thin films have a cubic structure with a preferentially orientation of (111). The calculated average grain size value was about 28-30 nm. The surface morphology of these films was studied by the Field Emission Scanning Electron Microscope (FESEM). The surfaces of the thin films were occurred from small stacks and nano-sized particles. The band gap values of the ZnSe nanocrystalline thin films were determined by UV-Visible absorption spectrum and the band gap values were found to be between 2.65-2.86 eV.

Transparent hydrogel with enhanced water retention capacity by introducing highly hydratable salt

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

Bai, Yuanyuan; Xiang, Feng; Wang, Hong, E-mail: hwang@mail.xjtu.edu.cn, E-mail: suo@seas.harvard.edu

2014-10-13

Polyacrylamide hydrogels containing salt as electrolyte have been used as highly stretchable transparent electrodes in flexible electronics, but those hydrogels are easy to dry out due to water evaporation. Targeted, we try to enhance water retention capacity of polyacrylamide hydrogel by introducing highly hydratable salts into the hydrogel. These hydrogels show enhanced water retention capacity in different level. Specially, polyacrylamide hydrogel containing high content of lithium chloride can retain over 70% of its initial water even in environment with relative humidity of only 10% RH. The excellent water retention capacities of these hydrogels will make more applications of hydrogels becomemore » possible.« less

In vivo biofunctional evaluation of hydrogels for disc regeneration.

PubMed

Reitmaier, Sandra; Kreja, Ludwika; Gruchenberg, Katharina; Kanter, Britta; Silva-Correia, Joana; Oliveira, Joaquim Miguel; Reis, Rui Luís; Perugini, Valeria; Santin, Matteo; Ignatius, Anita; Wilke, Hans-Joachim

2014-01-01

Regenerative strategies aim to restore the original biofunctionality of the intervertebral disc. Different biomaterials are available, which might support disc regeneration. In the present study, the prospects of success of two hydrogels functionalized with anti-angiogenic peptides and seeded with bone marrow derived mononuclear cells (BMC), respectively, were investigated in an ovine nucleotomy model. In a one-step procedure iliac crest aspirates were harvested and, subsequently, separated BMC were seeded on hydrogels and implanted into the ovine disc. For the cell-seeded approach a hyaluronic acid-based hydrogel was used. The anti-angiogenic potential of newly developed VEGF-blockers was investigated on ionically crosslinked metacrylated gellan gum hydrogels. Untreated discs served as nucleotomy controls. 24 adult merino sheep were used. After 6 weeks histological, after 12 weeks histological and biomechanical analyses were conducted. Biomechanical tests revealed no differences between any of the implanted and nucleotomized discs. All implanted discs significantly degenerated compared to intact discs. In contrast, there was no marked difference between implanted and nucleotomized discs. In tendency, albeit not significant, degeneration score and disc height index deteriorated for all but not for the cell-seeded hydrogels from 6 to 12 weeks. Cell-seeded hydrogels slightly decelerated degeneration. None of the hydrogel configurations was able to regenerate biofunctionality of the intervertebral disc. This might presumably be caused by hydrogel extrusion. Great importance should be given to the development of annulus sealants, which effectively exploit the potential of (cell-seeded) hydrogels for biological disc regeneration and restoration of intervertebral disc functioning.

Hydrogel-coated microfluidic channels for cardiomyocyte culture

PubMed Central

Annabi, Nasim; Selimović, Šeila; Cox, Juan Pablo Acevedo; Ribas, João; Bakooshli, Mohsen Afshar; Heintze, Déborah; Weiss, Anthony S.; Cropek, Donald; Khademhosseini, Ali

2013-01-01

The research areas of tissue engineering and drug development have displayed increased interest in organ-on-a-chip studies, in which physiologically or pathologically relevant tissues can be engineered to test pharmaceutical candidates. Microfluidic technologies enable the control of the cellular microenvironment for these applications through the topography, size, and elastic properties of the microscale cell culture environment, while delivering nutrients and chemical cues to the cells through continuous media perfusion. Traditional materials used in the fabrication of microfluidic devices, such as poly(dimethylsiloxane) (PDMS), offer high fidelity and high feature resolution, but do not facilitate cell attachment. To overcome this challenge, we have developed a method for coating microfluidic channels inside a closed PDMS device with a cell-compatible hydrogel layer. We have synthesized photocrosslinkable gelatin and tropoelastin-based hydrogel solutions that were used to coat the surfaces under continuous flow inside 50 μm wide, straight microfluidic channels to generate a hydrogel layer on the channel walls. Our observation of primary cardiomyocytes seeded on these hydrogel layers showed preferred attachment as well as higher spontaneous beating rates on tropoelastin coatings compared to gelatin. In addition, cellular attachment, alignment and beating were stronger on 5 % (w/v) hydrogel-coated devices than on 10 % (w/v) gel-coated channels. Our results demonstrate that cardiomyocytes respond favorably to the elastic, soft tropoelastin culture substrates, indicating that tropoelastin-based hydrogels may be a suitable coating choice for some organ-on-a-chip applications. We anticipate that the proposed hydrogel coating method and tropoelastin as a cell culture substrate may be useful for the generation of elastic tissues, e.g. blood vessels, using microfluidic approaches. PMID:23728018

Topography, wetting, and corrosion responses of electrodeposited hydroxyapatite and fluoridated hydroxyapatite on magnesium.

PubMed

Assadian, Mahtab; Jafari, Hassan; Ghaffari Shahri, Seyed Morteza; Idris, Mohd Hasbullah; Almasi, Davood

2016-08-12

In this study, different types of calcium-phosphate phases were coated on NaOH pre-treated pure magnesium. The coating was applied by electrodeposition method in order to provide higher corrosion resistance and improve biocompatibility for magnesium. Thickness, surface morphology and topography of the coatings were analyzed using optical, scanning electron and atomic-force microscopies, respectively. Composition and chemical bonding, crystalline structures and wettability of the coatings were characterized using energy-dispersive and attenuated total reflectance-Fourier transform infrared spectroscopies, grazing incidence X-ray diffraction and contact angle measurement, respectively. Degradation behavior of the coated specimens was also investigated by potentiodynamic polarization and immersion tests. The experiments proved the presence of a porous coating dominated by dicalcium-phosphate dehydrate on the specimens. It was also verified that the developed hydroxyapatite was crystallized by alkali post-treatment. Addition of supplemental fluoride to the coating electrolyte resulted in stable and highly crystallized structures of fluoridated hydroxyapatite. The coatings were found effective to improve biocompatibility combined with corrosion resistance of the specimens. Noticeably, the fluoride supplemented layer was efficient in lowering corrosion rate and increasing surface roughness of the specimens compared to hydroxyapatite and dicalcium-phosphate dehydrates layers.

Photodegradable, Photoadaptable Hydrogels via Radical-Mediated Disulfide Fragmentation Reaction.

PubMed

Fairbanks, Benjamin D; Singh, Samir P; Bowman, Christopher N; Anseth, Kristi S

2011-04-26

Various techniques have been adopted to impart a biological responsiveness to synthetic hydrogels for the delivery of therapeutic agents as well as the study and manipulation of biological processes and tissue development. Such techniques and materials include polyelectrolyte gels that swell and deswell with changes in pH, thermosensitive gels that contract at physiological temperatures, and peptide cross-linked hydrogels that degrade upon peptidolysis by cell-secreted enzymes. Herein we report a unique approach to photochemically deform and degrade disulfide cross-linked hydrogels, mitigating the challenges of light attenuation and low quantum yield, permitting the degradation of hydrogels up to 2 mm thick within 120 s at low light intensities (10 mW/cm(2) at 365 nm). Hydrogels were formed by the oxidation of thiol-functionalized 4-armed poly(ethylene glycol) macromolecules. These disulfide cross-linked hydrogels were then swollen in a lithium acylphosphinate photoinitiator solution. Upon exposure to light, photogenerated radicals initiate multiple fragmentation and disulfide exchange reactions, permitting and promoting photodeformation, photowelding, and photodegradation. This novel, but simple, approach to generate photoadaptable hydrogels portends the study of cellular response to mechanically and topographically dynamic substrates as well as novel encapsulations by the welding of solid substrates. The principles and techniques described herein hold implications for more than hydrogel materials but also for photoadaptable polymers more generally.

Extracellular matrix hydrogels from decellularized tissues: Structure and function.

PubMed

Saldin, Lindsey T; Cramer, Madeline C; Velankar, Sachin S; White, Lisa J; Badylak, Stephen F

2017-02-01

Extracellular matrix (ECM) bioscaffolds prepared from decellularized tissues have been used to facilitate constructive and functional tissue remodeling in a variety of clinical applications. The discovery that these ECM materials could be solubilized and subsequently manipulated to form hydrogels expanded their potential in vitro and in vivo utility; i.e. as culture substrates comparable to collagen or Matrigel, and as injectable materials that fill irregularly-shaped defects. The mechanisms by which ECM hydrogels direct cell behavior and influence remodeling outcomes are only partially understood, but likely include structural and biological signals retained from the native source tissue. The present review describes the utility, formation, and physical and biological characterization of ECM hydrogels. Two examples of clinical application are presented to demonstrate in vivo utility of ECM hydrogels in different organ systems. Finally, new research directions and clinical translation of ECM hydrogels are discussed. More than 70 papers have been published on extracellular matrix (ECM) hydrogels created from source tissue in almost every organ system. The present manuscript represents a review of ECM hydrogels and attempts to identify structure-function relationships that influence the tissue remodeling outcomes and gaps in the understanding thereof. There is a Phase 1 clinical trial now in progress for an ECM hydrogel. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Dual-responsive and Multi-functional Plasmonic Hydrogel Valves and Biomimetic Architectures Formed with Hydrogel and Gold Nanocolloids

PubMed Central

Song, Ji Eun; Cho, Eun Chul

2016-01-01

We present a straightforward approach with high moldability for producing dual-responsive and multi-functional plasmonic hydrogel valves and biomimetic architectures that reversibly change volumes and colors in response to temperature and ion variations. Heating of a mixture of hybrid colloids (gold nanoparticles assembled on a hydrogel colloid) and hydrogel colloids rapidly induces (within 30 min) the formation of hydrogel architectures resembling mold shapes (cylinder, fish, butterfly). The biomimetic fish and butterfly display reversible changes in volumes and colors with variations of temperature and ionic conditions in aqueous solutions. The cylindrical plasmonic valves installed in flow tubes rapidly control water flow rate in on-off manner by responding to these stimuli. They also report these changes in terms of their colors. Therefore, the approach presented here might be helpful in developing new class of biomimetic and flow control systems where liquid conditions should be visually notified (e.g., glucose or ion concentration changes). PMID:27703195

[In Situ Polymerization and Characterization of Hydroxyapatite/polyurethane Implanted Material].

PubMed

Gu, Muqing; Xiao, Fengjuan; Liang, Ye; Yue, Lin; Li, Song; Li, Lanlan; Feng, Feifei

2015-08-01

In order to improve the interfacial bonding strength of hydroxyapatite/polyurethane implanted material and dispersion of hydroxyapatite in the polyurethane matrix, we in the present study synthesized nano-hydroxyapatite/polyurethane composites by in situ polymerization. We then characterized and analyzed the fracture morphology, thermal stability, glass transition temperature and mechanical properties. We seeded MG63 cells on composites to evaluate the cytocompatibility of the composites. In situ polymerization could improve the interfacial bonding strength, ameliorate dispersion of hydroxyapatite in the properties of the composites. After adding 20 wt% hydroxyapatite into the polyurethane, the thermal stability was improved and the glass transition temperatures were increased. The tensile strength and maximum elongation were 6.83 MPa and 861.17%, respectively. Compared with those of pure polyurethane the tensile strength and maximum elongation increased by 236.45% and 143.30%, respectively. The composites were helpful for cell adhesion and proliferation in cultivation.

Synthetically Simple, Highly Resilient Hydrogels

PubMed Central

Cui, Jun; Lackey, Melissa A.; Madkour, Ahmad E.; Saffer, Erika M.; Griffin, David M.; Bhatia, Surita R.; Crosby, Alfred J.; Tew, Gregory N.

2014-01-01

Highly resilient synthetic hydrogels were synthesized by using the efficient thiol-norbornene chemistry to cross-link hydrophilic poly(ethylene glycol) (PEG) and hydrophobic polydimethylsiloxane (PDMS) polymer chains. The swelling and mechanical properties of the hydrogels were well-controlled by the relative amounts of PEG and PDMS. In addition, the mechanical energy storage efficiency (resilience) was more than 97% at strains up to 300%. This is comparable with one of the most resilient materials known: natural resilin, an elastic protein found in many insects, such as in the tendons of fleas and the wings of dragonflies. The high resilience of these hydrogels can be attributed to the well-defined network structure provided by the versatile chemistry, low cross-link density, and lack of secondary structure in the polymer chains. PMID:22372639

Morphology and electronic structure of nanoscale powders of calcium hydroxyapatite

NASA Astrophysics Data System (ADS)

Kurgan, Nataly; Karbivskyy, Volodymyr; Kasyanenko, Vasyl

2015-02-01

Atomic force microscopy, infrared spectroscopy and NMR studied morphological and physicochemical properties of calcium hydroxyapatite powders produced by changing the temperature parameters of synthesis. Features of morphology formation of calcium hydroxyapatite nanoparticles with an annealing temperature within 200°C to 1,100°C were determined. It is shown that the particle size of the apatite obtained that annealed 700°C is 40 nm corresponding to the particle size of apatite in native bone. The effect of dimension factor on structural parameters of calcium hydroxyapatite is manifested in a more local symmetry of the PO4 3- tetrahedra at nanodispersed calcium hydroxyapatite.

Identification of glycosaminoglycans using high-performance liquid chromatography on a hydroxyapatite column.

PubMed

Narita, H; Takeda, Y; Takagaki, K; Nakamura, T; Harata, S; Endo, M

1995-11-20

Glycosaminoglycans (heparin, heparan sulfate, dermatan sulfate, chondroitin sulfate, and hyaluronic acid) were labeled with a fluorescent reagent, 2-aminopyridine. The fluoro-labeled glycosaminoglycans were subjected to high-performance liquid chromatography on a hydroxyapatite column. The binding property of each glycosaminoglycan to hydroxyapatite was different. The structural properties of glycosaminoglycans bound to hydroxyapatite were then investigated using chemical desulfated or enzymic depolymerized glycosaminoglycans. This revealed that the sulfate content and molecular weight of the glycosaminoglycans correlated with their binding properties to hydroxyapatite. Desulfated dermatan sulfate but not desulfated chondroitin 6-sulfate bound to the hydroxyapatite. These data indicate that iduronic acid residues of glycosaminoglycans are important for the binding property. The method described which uses hydroxyapatite columns facilitates rapid separation and microanalysis of the glycosaminoglycans, especially dermatan sulfate and chondroitin sulfate.

Use of radiation in the production of hydrogels

NASA Astrophysics Data System (ADS)

Lugao, Ademar B.; Malmonge, Sônia Maria

2001-12-01

The first hydrogel for wound dressing processed by radiation left the laboratories in Poland in 1986 by the hands of its inventor Janusz M. Rosiak and soon, after formal tests, arrived in the local market (1992). It was a technological breakthrough due to its product characteristics as pain reliever and enhanced healing properties besides its clever production process combining sterilization and crosslinking in a simultaneous operation. IAEA invited professor Rosiak to support the transference of his technology for many laboratories around the world. The laboratories of developing countries, which face all kinds of restrictions, were seduced by the simplicity of the process and low cost of its raw materials. This was the seed of the flourishing activities in hydrogel dressings in Brazil and other developing countries. The technology transfer of the radiation production of hydrogel dressings and other hydrogels to the Brazilian industry is under way. The usual issues associated with radiation processing arise from this experience, i.e. capital costs, misinformation about radiation and lack of expertise on radiation processing. Some other issues concerning local market and social peculiarities also add to the problem. Notwithstanding, many different opportunities arise from those challenges. These technical and commercial issues are roughly: (i) There are plenty of new hydrogels in the market and all say the same. What else radiation processed hydrogels can say? (ii) Regarding to hydrogels and its industrial production as market product, what are the unique characteristics of radiation processing? It was shown that the radiation is a powerful tool for producing hydrogels the same basic formula with improved flexibility, control and purity.

Mechanical, dielectric and surface analysis of hydroxyapatite doped anions for implantations

NASA Astrophysics Data System (ADS)

Helen, S.; Kumar, A. Ruban

2018-04-01

Calcium Phosphate has broad applications in field of medicine and in tissue engineering. In that hydroxyapatite is one of the calcium phosphate similar to bone and teeth mineral phase. The aim of this paper is to improve mechanical property of hydroxyapatite which has less mechanical strength by doping of ions. The ions increase its strength which can be used in various medical applications. Surface property of hydroxyapatite and electrical property of ion doped hydroxyapatite analyzed and shown that it can be used in implantations, coatings.

Therapeutic applications of hydrogels in oral drug delivery

PubMed Central

Sharpe, Lindsey A; Daily, Adam M; Horava, Sarena D; Peppas, Nicholas A

2015-01-01

Introduction Oral delivery of therapeutics, particularly protein-based pharmaceutics, is of great interest for safe and controlled drug delivery for patients. Hydrogels offer excellent potential as oral therapeutic systems due to inherent biocompatibility, diversity of both natural and synthetic material options and tunable properties. In particular, stimuli-responsive hydrogels exploit physiological changes along the intestinal tract to achieve site-specific, controlled release of protein, peptide and chemotherapeutic molecules for both local and systemic treatment applications. Areas covered This review provides a wide perspective on the therapeutic use of hydrogels in oral delivery systems. General features and advantages of hydrogels are addressed, with more considerable focus on stimuli-responsive systems that respond to pH or enzymatic changes in the gastrointestinal environment to achieve controlled drug release. Specific examples of therapeutics are given. Last, in vitro and in vivo methods to evaluate hydrogel performance are discussed. Expert opinion Hydrogels are excellent candidates for oral drug delivery, due to the number of adaptable parameters that enable controlled delivery of diverse therapeutic molecules. However, further work is required to more accurately simulate physiological conditions and enhance performance, which is important to achieve improved bioavailability and increase commercial interest. PMID:24848309

"Bulk" Nanocrystalline Metals: Review of the Current State of the Art and Future Opportunities for Copper and Copper Alloys

NASA Astrophysics Data System (ADS)

Tschopp, M. A.; Murdoch, H. A.; Kecskes, L. J.; Darling, K. A.

2014-06-01

It is a new beginning for innovative fundamental and applied science in nanocrystalline materials. Many of the processing and consolidation challenges that have haunted nanocrystalline materials are now more fully understood, opening the doors for bulk nanocrystalline materials and parts to be produced. While challenges remain, recent advances in experimental, computational, and theoretical capability have allowed for bulk specimens that have heretofore been pursued only on a limited basis. This article discusses the methodology for synthesis and consolidation of bulk nanocrystalline materials using mechanical alloying, the alloy development and synthesis process for stabilizing these materials at elevated temperatures, and the physical and mechanical properties of nanocrystalline materials with a focus throughout on nanocrystalline copper and a nanocrystalline Cu-Ta system, consolidated via equal channel angular extrusion, with properties rivaling that of nanocrystalline pure Ta. Moreover, modeling and simulation approaches as well as experimental results for grain growth, grain boundary processes, and deformation mechanisms in nanocrystalline copper are briefly reviewed and discussed. Integrating experiments and computational materials science for synthesizing bulk nanocrystalline materials can bring about the next generation of ultrahigh strength materials for defense and energy applications.

Skin-inspired hydrogel-elastomer hybrids with robust interfaces and functional microstructures

NASA Astrophysics Data System (ADS)

Yuk, Hyunwoo; Zhang, Teng; Parada, German Alberto; Liu, Xinyue; Zhao, Xuanhe

2016-06-01

Inspired by mammalian skins, soft hybrids integrating the merits of elastomers and hydrogels have potential applications in diverse areas including stretchable and bio-integrated electronics, microfluidics, tissue engineering, soft robotics and biomedical devices. However, existing hydrogel-elastomer hybrids have limitations such as weak interfacial bonding, low robustness and difficulties in patterning microstructures. Here, we report a simple yet versatile method to assemble hydrogels and elastomers into hybrids with extremely robust interfaces (interfacial toughness over 1,000 Jm-2) and functional microstructures such as microfluidic channels and electrical circuits. The proposed method is generally applicable to various types of tough hydrogels and diverse commonly used elastomers including polydimethylsiloxane Sylgard 184, polyurethane, latex, VHB and Ecoflex. We further demonstrate applications enabled by the robust and microstructured hydrogel-elastomer hybrids including anti-dehydration hydrogel-elastomer hybrids, stretchable and reactive hydrogel-elastomer microfluidics, and stretchable hydrogel circuit boards patterned on elastomer.

Reusable self-healing hydrogels realized via in situ polymerization.

PubMed

Vivek, Balachandran; Prasad, Edamana

2015-04-09

In this work, a self-healing hydrogel has been prepared using in situ polymerization of acrylic acid and acrylamide in the presence of glycogen. The hydrogel was characterized using NMR, SEM, FT-IR, rheology, and dynamic light scattering (DLS) studies. The developed hydrogel exhibits self-healing properties at neutral pH, high swelling ability, high elasticity, and excellent mechanical strength. The hydrogel exhibits modulus values (G', G″) as high as 10(6) Pa and shows an exceptionally high degree of swelling ratio (∼3.5 × 10(3)). Further, the polymer based hydrogel adsorbs toxic metal ions (Cd(2+), Pb(2+), and Hg(2+)) and organic dyes (methylene blue and methyl orange) from contaminated water with remarkable efficiency (90-98%). The mechanistic analysis indicated the presence of pseudo-second-order reaction kinetics. The reusability of the hydrogel has been demonstrated by repeating the adsorption-desorption process over five cycles with identical results in the adsorption efficiency.

Gradient Material Strategies for Hydrogel Optimization in Tissue Engineering Applications

PubMed Central

2018-01-01

Although a number of combinatorial/high-throughput approaches have been developed for biomaterial hydrogel optimization, a gradient sample approach is particularly well suited to identify hydrogel property thresholds that alter cellular behavior in response to interacting with the hydrogel due to reduced variation in material preparation and the ability to screen biological response over a range instead of discrete samples each containing only one condition. This review highlights recent work on cell–hydrogel interactions using a gradient material sample approach. Fabrication strategies for composition, material and mechanical property, and bioactive signaling gradient hydrogels that can be used to examine cell–hydrogel interactions will be discussed. The effects of gradients in hydrogel samples on cellular adhesion, migration, proliferation, and differentiation will then be examined, providing an assessment of the current state of the field and the potential of wider use of the gradient sample approach to accelerate our understanding of matrices on cellular behavior. PMID:29485612

Gelator-polysaccharide hybrid hydrogel for selective and controllable dye release.

PubMed

Li, Ping; Dou, Xiao-Qiu; Tang, Yi-Tian; Zhu, Shenmin; Gu, Jiajun; Feng, Chuan-Liang; Zhang, Di

2012-12-01

In this paper, 1,4-bi(phenylalanine-diglycol)-benzene (PDB) based Low-Molecular-Weight-Gelator (LMWG) hydrogels are modified using hydrophilic polysaccharide (sodium alginate). A set of techniques including Fourier transform infrared (FT-IR) spectroscopy, (1)H Nuclear Magnetic Resonance ((1)H NMR), X-ray powder diffraction (XRD), Ultraviolet-Visible (UV-Vis), and circular dichroism (CD) had confirmed a β-turn arrangement of PDB gelators and a semi-interpenetrating network (semi-IPN), which was formed through hydrogen bonds between LMWG fibers and polysaccharide chains. The evaluation of physicochemical properties of hydrogels indicates that gelator-polysaccharide hybrid hydrogels possess better mechanical and water retention properties than LMWG hydrogels. The release study of dyes (model drug) from both LMWG and hybrid hydrogels was carried out. Compared with PDB based hydrogels, hybrid hydrogels show a selective and controllable release property for certain dyes. The results suggest LMWG-polysaccharide hybrid gels may find potential applications as promising drug delivery vehicles for drug molecules. Copyright © 2012 Elsevier Inc. All rights reserved.

Polymer Structure and Water States in Salt-Containing Polyampholyte Hydrogels

NASA Astrophysics Data System (ADS)

Li, Xinda; Elliott, Janet A. W.; Lee, Byeongdu; Chung, Hyun-Joong

The phase behavior of water in hydrogels has broad impact on various applications, such as lubrication, adhesion, and electrical conductivity, as well as the hydrogel's low temperature properties. The status of the water molecules is correlated to the structure of the polymer chains in the hydrogel. In this study, the structure and water status of a model charge-balanced polyampholyte poly(4-vinylbenzenesulfonate-co-[3-(methacryloylamino) propyl] trimethylammonium chloride), were investigated by using differential scanning calorimetry (DSC) and small-angle x-ray scattering (SAXS). A globular network structure suggested by SAXS results dictated the depression of the freezing point of water in the hydrogel, as supported by the DSC results. The polyampholyte chains undergo an irreversible collapse during dialysis in deionized water. Such collapsed hydrogels are not able to prevent freezing of water molecules. The results of both synthesis condition and post-synthesis treatments for polyampholyte hydrogels provide us insights to design optimal polyampholyte hydrogels for low temperature applications.

Electrophoretic deposition of zinc-substituted hydroxyapatite coatings.

PubMed

Sun, Guangfei; Ma, Jun; Zhang, Shengmin

2014-06-01

Zinc-substituted hydroxyapatite nanoparticles synthesized by the co-precipitation method were used to coat stainless steel plates by electrophoretic deposition in n-butanol with triethanolamine as a dispersant. The effect of zinc concentration in the synthesis on the morphology and microstructure of coatings was investigated. It is found that the deposition current densities significantly increase with the increasing zinc concentration. The zinc-substituted hydroxyapatite coatings were analyzed by X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectroscopy. It is inferred that hydroxyapatite and triethanolamine predominate in the chemical composition of coatings. With the increasing Zn/Ca ratios, the contents of triethanolamine decrease in the final products. The triethanolamine can be burnt out by heat treatment. The tests of adhesive strength have confirmed good adhesion between the coatings and substrates. The formation of new apatite layer on the coatings has been observed after 7days of immersion in a simulated body fluid. In summary, the results show that dense, uniform zinc-substituted hydroxyapatite coatings are obtained by electrophoretic deposition when the Zn/Ca ratio reaches 5%. Copyright © 2014 Elsevier B.V. All rights reserved.

Artificial Auricular Cartilage Using Silk Fibroin and Polyvinyl Alcohol Hydrogel

PubMed Central

Lee, Jung Min; Sultan, Md. Tipu; Kim, Soon Hee; Kumar, Vijay; Yeon, Yeung Kyu; Lee, Ok Joo; Park, Chan Hum

2017-01-01

Several methods for auricular cartilage engineering use tissue engineering techniques. However, an ideal method for engineering auricular cartilage has not been reported. To address this issue, we developed a strategy to engineer auricular cartilage using silk fibroin (SF) and polyvinyl alcohol (PVA) hydrogel. We constructed different hydrogels with various ratios of SF and PVA by using salt leaching, silicone mold casting, and freeze-thawing methods. We characterized each of the hydrogels in terms of the swelling ratio, tensile strength, pore size, thermal properties, morphologies, and chemical properties. Based on the cell viability results, we found a blended hydrogel composed of 50% PVA and 50% SF (P50/S50) to be the best hydrogel among the fabricated hydrogels. An intact 3D ear-shaped auricular cartilage formed six weeks after the subcutaneous implantation of a chondrocyte-seeded 3D ear-shaped P50/S50 hydrogel in rats. We observed mature cartilage with a typical lacunar structure both in vitro and in vivo via histological analysis. This study may have potential applications in auricular tissue engineering with a human ear-shaped hydrogel. PMID:28777314

Injectable dual redox responsive diselenide-containing poly(ethylene glycol) hydrogel.

PubMed

Gong, Chu; Shan, Meng; Li, Bingqiang; Wu, Guolin

2017-09-01

An injectable dual redox responsive diselenide-containing poly(ethylene glycol) (PEG) hydrogel was successfully developed by combining the conceptions of injectable hydrogels and dual redox responsive diselenides. In the first step, four-armed PEG was modified with N-hydroxysuccinimide (NHS)-activated esters and thereafter, crosslinked by selenocystamine crosslinkers to form injectable hydrogels via the rapid reaction between NHS-activated esters and amino groups. The cross-sectional morphology, mechanical properties, and crosslinking modes of hydrogels were well characterized via scanning electron microscope (SEM), rheological measurements, and Fourier transform infrared spectra, respectively. In addition, the oxidation- and reduction-responsive degradation behaviors of hydrogels were observed and analyzed. The model drug, rhodamine B, was encapsulated in the hydrogel. The drug-loaded hydrogel exhibited a dual redox responsive release profile, which was consistent with the degradation experiments. The results of all experiments indicated that the formulated injectable dual redox responsive diselenide-containing PEG hydrogel can have potential applications in various biomedical fields such as drug delivery and stimuli-responsive drug release. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2451-2460, 2017. © 2017 Wiley Periodicals, Inc.

A novel chitosan-tussah silk fibroin/nano-hydroxyapatite composite bone scaffold platform with tunable mechanical strength in a wide range.

PubMed

Ran, Jiabing; Hu, Jingxiao; Sun, Guanglin; Chen, Si; Jiang, Pei; Shen, Xinyu; Tong, Hua

2016-12-01

Currently, great efforts have been made to enhance the mechanical strength of bone tissue engineering (BTE) scaffolds, which are composed of biopolymeric matrices and inorganic nano-fillers. But the tunability of mechanical strength in a wide range for BTE scaffolds has seldom been investigated in spite of the great importance of this performance. In this work, a chitosan-tussah silk fibroin/hydroxyapatite (CS-TSF/HAp) hydrogel was synthesized by using a novel in situ precipitation method. Through in situ inducing the conformation transition of TSF in the CS-TSF/HAp hydrogel, which could be monitored by XRD, FT-IR, TGA, and DTA, the elastic modulus and fracture strength of the final CS-TSF/HAp composite could be tailored in a wide range without changing its composition, morphology, roughness, and crystal structures. The elastic modulus of the CS-TSF/HAp composite ranged from ∼250 to ∼400MPa while its fracture strength ranged from ∼45 to ∼100MPa. In order to clarify the rationale behind this process, a speculative explanation was provided. In vitro cell culture indicated that MC3T3-E1 cells cultured on the CS-TSF/HAp composite had positive adhesion, proliferation, and differentiation potential. We believed that the CS-TSF/HAp composite could be used as an ideal scaffold platform for cell culture and implantation of bone reconstruction. Copyright © 2016 Elsevier B.V. All rights reserved.

Tribological properties of PVA/PVP blend hydrogels against articular cartilage.

PubMed

Kanca, Yusuf; Milner, Piers; Dini, Daniele; Amis, Andrew A

2018-02-01

This research investigated in-vitro tribological performance of the articulation of cartilage-on- polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP) blend hydrogels using a custom-designed multi-directional wear rig. The hydrogels were prepared by repeated freezing-thawing cycles at different concentrations and PVA to PVP fractions at a given concentration. PVA/PVP blend hydrogels showed low coefficient of friction (COF) values (between 0.12 ± 0.01 and 0.14 ± 0.02) which were closer to the cartilage-on-cartilage articulation (0.03 ± 0.01) compared to the cartilage-on-stainless steel articulation (0.46 ± 0.06). The COF increased with increasing hydrogel concentration (p = 0.03) and decreasing PVP content at a given concentration (p < 0.05). The cartilage-on-hydrogel tests showed only the surface layers of the cartilage being removed (average volume loss of the condyles was 12.5 ± 4.2mm 3 ). However, the hydrogels were found to be worn/deformed. The hydrogels prepared at a higher concentration showed lower apparent volume loss. A strong correlation (R 2 = 0.94) was found between the COF and compressive moduli of the hydrogel groups, resulting from decreasing contact congruency. It was concluded that the hydrogels were promising as hemiarthroplasty materials, but that improved mechanical behaviour was required for clinical use. Copyright © 2017 Elsevier Ltd. All rights reserved.

Growth characteristics of nanocrystalline silicon films fabricated by using chlorinated precursors at low temperatures.

PubMed

Huang, Rui; Ding, Honglin; Song, Jie; Guo, Yanqing; Wang, Xiang; Lin, Xuanying

2010-11-01

We employed plasma enhanced chemical vapor deposition technique to fabricate nanocrystalline Si films at a low temperature of 250 degrees C by using SiCl4 and H2 as source gases. The evolution of microstructure of the films with deposition periods shows that nanocrystalline Si can be directly grown on amorphous substrate at the initial growth process, which is in contrast to the growth behavior observed in the SiH4/H2 system. Furthermore, it is interesting to find that the area density of nanocrystalline Si as well as grain size can be controlled by modulating the concentration of SiCl4. By decreasing the SiCl4 concentration, the area density of nanocrystalline Si can be enhanced up to 10(11) cm(-2), while the grain size is shown to decrease down to 10 nm. It is suggested that Cl plays an important role in the low-temperature growth of nanocrystalline Si.

Adhesion of Pseudomonas aeruginosa and Staphylococcus epidermidis to silicone-hydrogel contact lenses.

PubMed

Henriques, Mariana; Sousa, Cláudia; Lira, Madalena; Elisabete, M; Oliveira, Real; Oliveira, Rosário; Azeredo, Joana

2005-06-01

The purpose of this study is to compare the adhesion capabilities of the most important etiologic agents of microbial ocular infection to the recently available silicone-hydrogel lenses with those to a conventional hydrogel lens. In vitro static adhesion assays of Pseudomonas aeruginosa 10,145, Staphylococcus epidermidis 9142 (biofilm-positive), and 12,228 (biofilm-negative) to two extended-wear silicone-hydrogel lenses (balafilcon A and lotrafilcon A), a daily wear silicone-hydrogel lens (galyfilcon A) and a conventional hydrogel (etafilcon A) were performed. To interpret the adhesion results, lens surface relative hydrophobicity was assessed by water contact angle measurements. P. aeruginosa and S. epidermidis 9142 exhibited greater adhesion capabilities to the extended wear silicone-hydrogel lenses than to the daily wear silicone- and conventional hydrogel lenses (p < 0.05). No statistical differences were found between the adhesion extent of these strains to galyfilcon A and etafilcon A. The biofilm negative strain of S. epidermidis adhered in larger extents to the silicone-hydrogel lenses than to the conventional hydrogel (p < 0.05), but in much lower amounts than the biofilm-positive strain. The water contact angle measurements revealed that the extended wear silicone-hydrogel lenses are hydrophobic, whereas the daily wear silicone- and conventional hydrogel lenses are hydrophilic. As a result of their hydrophobicity, the extended wear silicone-hydrogel lenses (lotrafilcon A and balafilcon A) may carry higher risk of microbial contamination than both the hydrophilic daily wear silicone-hydrogel lens, galyfilcon A and the conventional hydrogel lens, etafilcon A.

Grain Size Threshold for Enhanced Irradiation Resistance in Nanocrystalline and Ultrafine Tungsten

DOE PAGES

El Atwani, Osman; Hinks, Jonathan; Greaves, Graeme; ...

2017-02-21

Nanocrystalline metals are considered highly radiation-resistant materials due to their large grain boundary areas. Here, the existence of a grain size threshold for enhanced irradiation resistance in high-temperature helium-irradiated nanocrystalline and ultrafine tungsten is demonstrated. Average bubble density, projected bubble area and the corresponding change in volume were measured via transmission electron microscopy and plotted as a function of grain size for two ion fluences. Nanocrystalline grains of less than 35 nm size possess ~10–20 times lower change in volume than ultrafine grains and this is discussed in terms of the grain boundaries defect sink efficiency.

Hydroxyapatite Reinforced Coatings with Incorporated Detonationally Generated Nanodiamonds

NASA Astrophysics Data System (ADS)

Pramatarova, L.; Pecheva, E.; Dimitrova, R.; Spassov, T.; Krasteva, N.; Hikov, T.; Fingarova, D.; Mitev, D.

2010-01-01

We studied the effect of the substrate chemistry on the morphology of hydroxyapatite-detonational nanodiamond composite coatings grown by a biomimetic approach (immersion in a supersaturated simulated body fluid). When detonational nanodiamond particles were added to the solution, the morphology of the grown for 2 h composite particles was porous but more compact then that of pure hydroxyapatite particles. The nanodiamond particles stimulated the hydroxyapatite growth with different morphology on the various substrates (Ti, Ti alloys, glasses, Si, opal). Biocompatibility assay with MG63 osteoblast cells revealed that the detonational nanodiamond water suspension with low and average concentration of the detonational nanodiamond powder is not toxic to living cells.

Reversible Modulation of DNA-Based Hydrogel Shapes by Internal Stress Interactions.

PubMed

Hu, Yuwei; Kahn, Jason S; Guo, Weiwei; Huang, Fujian; Fadeev, Michael; Harries, Daniel; Willner, Itamar

2016-12-14

We present the assembly of asymmetric two-layer hybrid DNA-based hydrogels revealing stimuli-triggered reversibly modulated shape transitions. Asymmetric, linear hydrogels that include layer-selective switchable stimuli-responsive elements that control the hydrogel stiffness are designed. Trigger-induced stress in one of the layers results in the bending of the linear hybrid structure, thereby minimizing the elastic free energy of the systems. The removal of the stress by a counter-trigger restores the original linear bilayer hydrogel. The stiffness of the DNA hydrogel layers is controlled by thermal, pH (i-motif), K + ion/crown ether (G-quadruplexes), chemical (pH-doped polyaniline), or biocatalytic (glucose oxidase/urease) triggers. A theoretical model relating the experimental bending radius of curvatures of the hydrogels with the Young's moduli and geometrical parameters of the hydrogels is provided. Promising applications of shape-regulated stimuli-responsive asymmetric hydrogels include their use as valves, actuators, sensors, and drug delivery devices.

Nanocrystalline Iron-Ore-Based Catalysts for Fischer-Tropsch Synthesis.

PubMed

Yong, Seok; Park, Ji Chan; Lee, Ho-Tae; Yang, Jung-Il; Hong, SungJun; Jung, Heon; Chun, Dong Hyun

2016-02-01

Nanocrystalline iron ore particles were fabricated by a wet-milling process using an Ultra Apex Mill, after which they were used as raw materials of iron-based catalysts for low-temperature Fischer-Tropsch synthesis (FTS) below 280 degrees C, which usually requires catalysts with a high surface area, a large pore volume, and a small crystallite size. The wet-milling process using the Ultra Apex Mill effectively destroyed the initial crystallite structure of the natural iron ores of several tens to hundreds of nanometers in size, resulting in the generation of nanocrystalline iron ore particles with a high surface area and a large pore volume. The iron-ore-based catalysts prepared from the nanocrystalline iron ore particles effectively catalyzed the low-temperature FTS, displaying a high CO conversion (about 90%) and good C5+ hydrocarbon productivity (about 0.22 g/g(cat)(-h)). This demonstrates the feasibility of using the iron-ore-based catalysts as inexpensive and disposable catalysts for the low-temperature FTS.

The Effect of Zirconia in Hydroxyapatite on Staphylococcus epidermidis Growth.

PubMed

Siswomihardjo, Widowati; Sunarintyas, Siti; Tontowi, Alva Edy

2012-01-01

Synthetic hydroxyapatite (HA) has been widely used and developed as the material for bone substitute in medical applications. The addition of zirconia is needed to improve the strength of hydroxyapatite as the bone substitute. One of the drawbacks in the use of biomedical materials is the occurrence of biomaterial-centred infections. The recent method of limiting the presence of microorganism on biomaterials is by providing biomaterial-bound metal-containing compositions. In this case, S. epidermidis is the most common infectious organism in biomedical-centred infection. Objective. This study was designed to evaluate the effect of zirconia concentrations in hydroxyapatite on the growth of S. epidermidis. Methods and Materials. The subjects of this study were twenty hydroxyapatite discs, divided into four groups in which one was the control and the other three were the treatment groups. Zirconia powder with the concentrations of 20%, 30%, and 40% was added into the three different treatment groups. Scanning electron microscope analysis was performed according to the hydroxyapatite and hydroxyapatite-zirconia specimens. All discs were immersed into S. epidermidis culture for 24 hours and later on they were soaked into a medium of PBS. The cultured medium was spread on mannitol salt agar. After incubation for 24 hours at 37°C , the number of colonies was measured with colony counter. Data obtained were analyzed using the ANOVA followed by the pairwise comparison. Result. The statistical analysis showed that different concentrations of zirconia powder significantly influenced the number of S. epidermidis colony (P < 0.05) . Conclusion. The addition of zirconia into hydroxyapatite affected the growth of S. epidermidis. Hydroxyapatite with 20% zirconia proved to be an effective concentration to inhibit the growth of S. epidermidis colony.

The Effect of Zirconia in Hydroxyapatite on Staphylococcus epidermidis Growth

PubMed Central

Siswomihardjo, Widowati; Sunarintyas, Siti; Tontowi, Alva Edy

2012-01-01

Synthetic hydroxyapatite (HA) has been widely used and developed as the material for bone substitute in medical applications. The addition of zirconia is needed to improve the strength of hydroxyapatite as the bone substitute. One of the drawbacks in the use of biomedical materials is the occurrence of biomaterial-centred infections. The recent method of limiting the presence of microorganism on biomaterials is by providing biomaterial-bound metal-containing compositions. In this case, S. epidermidis is the most common infectious organism in biomedical-centred infection. Objective. This study was designed to evaluate the effect of zirconia concentrations in hydroxyapatite on the growth of S. epidermidis. Methods and Materials. The subjects of this study were twenty hydroxyapatite discs, divided into four groups in which one was the control and the other three were the treatment groups. Zirconia powder with the concentrations of 20%, 30%, and 40% was added into the three different treatment groups. Scanning electron microscope analysis was performed according to the hydroxyapatite and hydroxyapatite-zirconia specimens. All discs were immersed into S. epidermidis culture for 24 hours and later on they were soaked into a medium of PBS. The cultured medium was spread on mannitol salt agar. After incubation for 24 hours at 37°C , the number of colonies was measured with colony counter. Data obtained were analyzed using the ANOVA followed by the pairwise comparison. Result. The statistical analysis showed that different concentrations of zirconia powder significantly influenced the number of S. epidermidis colony (P < 0.05) . Conclusion. The addition of zirconia into hydroxyapatite affected the growth of S. epidermidis. Hydroxyapatite with 20% zirconia proved to be an effective concentration to inhibit the growth of S. epidermidis colony. PMID:22919390

Biomimetic hydrogel with tunable mechanical properties for vitreous substitutes.

PubMed

Santhanam, Sruthi; Liang, Jue; Struckhoff, Jessica; Hamilton, Paul D; Ravi, Nathan

2016-10-01

The vitreous humor of the eye is a biological hydrogel principally composed of collagen fibers interspersed with hyaluronic acid. Certain pathological conditions necessitate its removal and replacement. Current substitutes, like silicone oils and perfluorocarbons, are not biomimetic and have known complications. In this study, we have developed an in situ forming two-component biomimetic hydrogel with tunable mechanical and osmotic properties. The components are gellan, an analogue of collagen, and poly(methacrylamide-co-methacrylate), an analogue of hyaluronic acid; both endowed with thiol side groups. We used response surface methodology to consider seventeen possible hydrogels to determine how each component affects the optical, mechanical, sol-gel transition temperature and swelling properties. The optical and physical properties of the hydrogels were similar to vitreous. The shear storage moduli ranged from 3 to 358Pa at 1Hz and sol-gel transition temperatures from 35.5 to 43°C. The hydrogel had the ability to remain swollen without degradation for four weeks in vitro. Three hydrogels were tested for biocompatibility on primary porcine retinal pigment epithelial cells, human retinal pigment epithelial cells, and fibroblast (3T3/NIH) cells, by electric cell-substrate impedance sensing system. The two-component hydrogels allowed for the tuning and optimizing of mechanical, swelling, and transition temperature to obtain three biocompatible hydrogels with properties similar to the vitreous. Future studies include testing of the optimized hydrogels in animal models for use as a long-term substitute, whose preliminary results are mentioned. Although hydrogels are researched as long-term vitreous substitute, none have advanced sufficiently to reach clinical application. Our work focuses on the development of a novel two component in situ forming hydrogel that bio-mimic the natural vitreous. Our thiol-containing copolymers can be injected as an aqueous solution into

Mussel-inspired tough hydrogels with self-repairing and tissue adhesion

NASA Astrophysics Data System (ADS)

Gao, Zijian; Duan, Lijie; Yang, Yongqi; Hu, Wei; Gao, Guanghui

2018-01-01

The mussel-inspired polymeric hydrogels have been attractively explored owing to their self-repairing or adhesive property when the catechol groups of dopamine could chelate metal ions. However, it was a challenge for self-repairing hydrogels owning high mechanical properties. Herein, a synergistic strategy was proposed by combining catechol-Fe3+ complexes and hydrophobic association. The resulting hydrogels exhibited seamless self-repairing behavior, tissue adhesion and high mechanical property. Moreover, the pH-dependent stoichiometry of catechol-Fe3+ and temperature-sensitive hydrophobic association endue hydrogels with pH/thermo responsive characteristics. Subsequently, the self-repairing rate and mechanical property of hydrogels were investigated at different pH and temperature. This bio-inspired strategy would build an avenue for designing and constructing a new generation of self-repairing, tissue-adhesive and tough hydrogel.

A novel thermoresponsive hydrogel based on chitosan.

PubMed

Schuetz, Yannic B; Gurny, Robert; Jordan, Olivier

2008-01-01

Injectable thermosetting chitosan hydrogels are attractive systems for drug delivery and tissue engineering that combine biodegradability, biocompatibility and the ability to form in situ gel-like implants. Thermally-induced gelation relies advantageously on biopolymer secondary interactions, avoiding potentially toxic polymerization reactions that may occur with in situ polymerizing formulations. In view of a biomedical use, such formulations have to be sterilizable and storable on extended periods without losing their thermosetting properties. These two key features have been studied in the present paper. Chitosans from two different sources were added with several phosphate-free polyols or polyoses as gelling agents. Despite a reduction in chitosan molecular weight following autoclaving, the hydrogels prepared with autoclaved chitosan showed the desired thermosetting properties. Hence, chitosan steam sterilization combined with aseptic preparation of the hydrogel allows a sterile formulation to be obtained. Whereas thermosetting hydrogels were shown to be unstable when refrigerated, freezing was shown to be conceivable as a storage method. When trehalose or mannitol was used as stabilizing agent, the formulation reconstituted from a lyophilizate displayed thermosetting properties and was still injectable, paving the way to the development of a clinically utilizable, novel chitosan thermosetting hydrogel.

Biocompatibility of hydrogel-based scaffolds for tissue engineering applications.

PubMed

Naahidi, Sheva; Jafari, Mousa; Logan, Megan; Wang, Yujie; Yuan, Yongfang; Bae, Hojae; Dixon, Brian; Chen, P

2017-09-01

Recently, understanding of the extracellular matrix (ECM) has expanded rapidly due to the accessibility of cellular and molecular techniques and the growing potential and value for hydrogels in tissue engineering. The fabrication of hydrogel-based cellular scaffolds for the generation of bioengineered tissues has been based on knowledge of the composition and structure of ECM. Attempts at recreating ECM have used either naturally-derived ECM components or synthetic polymers with structural integrity derived from hydrogels. Due to their increasing use, their biocompatibility has been questioned since the use of these biomaterials needs to be effective and safe. It is not surprising then that the evaluation of biocompatibility of these types of biomaterials for regenerative and tissue engineering applications has been expanded from being primarily investigated in a laboratory setting to being applied in the multi-billion dollar medicinal industry. This review will aid in the improvement of design of non-invasive, smart hydrogels that can be utilized for tissue engineering and other biomedical applications. In this review, the biocompatibility of hydrogels and design criteria for fabricating effective scaffolds are examined. Examples of natural and synthetic hydrogels, their biocompatibility and use in tissue engineering are discussed. The merits and clinical complications of hydrogel scaffold use are also reviewed. The article concludes with a future outlook of the field of biocompatibility within the context of hydrogel-based scaffolds. Copyright © 2017 Elsevier Inc. All rights reserved.

Solution blowing of chitosan/PVA hydrogel nanofiber mats.

PubMed

Liu, Ruifang; Xu, Xianlin; Zhuang, Xupin; Cheng, Bowen

2014-01-30

Both nanofiber mats and hydrogel have their own advantages in wound healing. In this study, a novel hydrogel nanofiber mats were fabricated via solution blowing of chitosan and PVA solution, with various content of ethylene glycol diglycidyl ether (EGDE) as cross-linker. SEM observation showed that the fibers were several hundred nanometers in diameter with smooth surface and distributed randomly forming three-dimensional mats. The structure of the chitosan/PVA nanofibers was examined by FTIR and XPS, and the results showed that the cross-linking reaction occurred between EGDE and the hydroxyl groups. The mats could quickly hydrate in an aqueous environment to form hydrogel. Their value of equilibrate water absorption varied from 680 to 459% various content of EGDE. The nanofiber mats showed good bactericidal activity against Escherichia coli. The chitosan/PVA hydrogel nanofiber mats showed the combination advantages of nanofibrous mats and hydrogel dressing, and were suggested as potential application in wound healing. Copyright © 2013 Elsevier Ltd. All rights reserved.

In situ cell manipulation through enzymatic hydrogel photopatterning

NASA Astrophysics Data System (ADS)

Mosiewicz, Katarzyna A.; Kolb, Laura; van der Vlies, André J.; Martino, Mikaël M.; Lienemann, Philipp S.; Hubbell, Jeffrey A.; Ehrbar, Martin; Lutolf, Matthias P.

2013-11-01

The physicochemical properties of hydrogels can be manipulated in both space and time through the controlled application of a light beam. However, methods for hydrogel photopatterning either fail to maintain the bioactivity of fragile proteins and are thus limited to short peptides, or have been used in hydrogels that often do not support three-dimensional (3D) cell growth. Here, we show that the 3D invasion of primary human mesenchymal stem cells can be spatiotemporally controlled by micropatterning the hydrogel with desired extracellular matrix (ECM) proteins and growth factors. A peptide substrate of activated transglutaminase factor XIII (FXIIIa)—a key ECM crosslinking enzyme—is rendered photosensitive by masking its active site with a photolabile cage group. Covalent incorporation of the caged FXIIIa substrate into poly(ethylene glycol) hydrogels and subsequent laser-scanning lithography affords highly localized biomolecule tethering. This approach for the 3D manipulation of cells within gels should open up avenues for the study and manipulation of cell signalling.

Is hydroxyapatite a reliable fixation option in unicompartmental knee arthroplasty? A 5- to 13-year experience with the hydroxyapatite-coated unix prosthesis.

PubMed

Epinette, Jean-Alain; Manley, Michael T

2008-10-01

Hydroxyapatite-coated unicompartmental knee arthroplasty (UKA) is a debatable approach to unicompartmental knee arthritis because UKA isoften viewed as a short-term solution, at best, fora condition that will eventually require a total knee arthroplasty (TKA). Unicompartmental knee arthroplasty is a more technically demanding procedure than TKA, and appropriate patient selection, careful surgical technique, and correct choice of implant geometry are all critical components to its success. A fundamental issue surrounding UKA is whether hydroxyapatite-coated unicompartmental components can provide a long-term solution to unicondylar arthritis. We address this issue in the current study, which is based on a prospective series of 125 hydroxyapatite-coated Unix knee prostheses implanted consecutively between 1994 and 2002, with a 5-year minimum follow-up and a 13-year maximum follow-up. The results of our study indicate that uncemented hydroxyapatite-coated UKA can be successful in the long term.

Sustained and localized in vitro release of BMP-2/7, RANKL, and tetracycline from FlexBone, an elastomeric osteoconductive bone substitute.

PubMed

Xu, Jianwen; Li, Xinning; Lian, Jane B; Ayers, David C; Song, Jie

2009-10-01

We tested the hypothesis that synthetic composites containing a high percentage of osteoconductive biominerals well-integrated with a hydrophilic polymer matrix can be engineered to provide both the structural and biochemical framework of a viable synthetic bone substitute. FlexBone, an elastic hydrogel-mineral composite exhibiting excellent structural integration was prepared by crosslinking poly(2-hydroxyethyl methacrylate) hydrogel in the presence of 25 wt% nanocrystalline hydroxyapatite and 25 wt% tricalcium phosphate. Biologically active factors tetracycline, BMP-2/7, and RANKL that stimulate bone formation and remodeling were encapsulated into FlexBone during polymerization or via postpolymerization adsorption. SEM and dynamic mechanical analyses showed that the encapsulation of tetracycline (5.0 wt%) did not compromise the structural integrity and compressive behavior of FlexBone, which could withstand repetitive megapascal-compressive loadings and be securely press-fitted into critical femoral defects. Dose-dependent, sustained in vitro release of tetracycline was characterized by spectroscopy and bacterial inhibition. A single dose of 40 ng BMP-2/7 or 10 ng RANKL pre-encapsulated with 50 mg FlexBone, released over 1 week, was able to induce local osteogenic differentiation of myoblast C2C12 cells and osteoclastogenesis of macrophage RAW264.7 cells, respectively. With a bonelike structural composition, useful surgical handling characteristics, and tunable biochemical microenvironment, FlexBone provides an exciting opportunity for the treatment of hard-to-heal skeletal defects with minimal systemic side effects. (c) 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

Template-directed synthesis and selective adsorption of oligoadenylates in hydroxyapatite

NASA Technical Reports Server (NTRS)

Gibbs, D.; Lohrmann, R.; Orgel, L. E.

1980-01-01

Polyuridylic acid is adsorbed completely from aqueous solution by hydroxyapatite under conditions that permit template-directed synthesis of oligoadenylates in free solution. The yield of oligoadenylates is enhanced to almost the same extent by poly(U) in the presence or the absence of hydroxyapatite. Under very similar conditions small quantities of hydroxyapatite adsorb higher-molecular-weight oligoadenylates selectively from a mixture of oligomers. On the basis of these results a mechanism for prebiotic oligonucleotide formation is proposed in which selective adsorption on hydroxyapatite or some other immobilized anion-exchanging material plays a major role. Monomers are released from the surface for reactivation, while oligomers are retained in a protected environment by adsorption to the apatite surface.

Bio resorbability of the modified hydroxyapatite in Tris-HCL buffer

NASA Astrophysics Data System (ADS)

Golovanova, O. A.; Izmailov, R. R.; Ghyngazov, S. A.

2016-02-01

The solubility of carbonated hydroxyapatite powders and granulated carbonated hydroxyapatite produced from the synovial biofluid model solution has been studied. The kinetic characteristics of dissolution were determined. It was found that the solubility of carbonated hydroxyapatite is higher as compared to that of hydroxyapatite. The impact of the organic matrix on the rate of sample dissolution was revealed. For HA-gelatin composites, as the gelatin concentration grows, the dissolution rate becomes greater, and a sample of 6.0 g / L concentration has higher resorbability. The results of the research can be used to study the kinetics of dissolution and the biocompatibility of ceramic materials for medicine, namely for reconstructive surgery, dentistry, and development of drug delivery systems.

Nanocrystalline copper films are never flat.

PubMed

Zhang, Xiaopu; Han, Jian; Plombon, John J; Sutton, Adrian P; Srolovitz, David J; Boland, John J

2017-07-28

We used scanning tunneling microscopy to study low-angle grain boundaries at the surface of nearly planar copper nanocrystalline (111) films. The presence of grain boundaries and their emergence at the film surface create valleys composed of dissociated edge dislocations and ridges where partial dislocations have recombined. Geometric analysis and simulations indicated that valleys and ridges were created by an out-of-plane grain rotation driven by reduction of grain boundary energy. These results suggest that in general, it is impossible to form flat two-dimensional nanocrystalline films of copper and other metals exhibiting small stacking fault energies and/or large elastic anisotropy, which induce a large anisotropy in the dislocation-line energy. Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

Cobalt doped proangiogenic hydroxyapatite for bone tissue engineering application.

PubMed

Kulanthaivel, Senthilguru; Roy, Bibhas; Agarwal, Tarun; Giri, Supratim; Pramanik, Krishna; Pal, Kunal; Ray, Sirsendu S; Maiti, Tapas K; Banerjee, Indranil

2016-01-01

The present study delineates the synthesis and characterization of cobalt doped proangiogenic-osteogenic hydroxyapatite. Hydroxyapatite samples, doped with varying concentrations of bivalent cobalt (Co(2+)) were prepared by the ammoniacal precipitation method and the extent of doping was measured by ICP-OES. The crystalline structure of the doped hydroxyapatite samples was confirmed by XRD and FTIR studies. Analysis pertaining to the effect of doped hydroxyapatite on cell cycle progression and proliferation of MG-63 cells revealed that the doping of cobalt supported the cell viability and proliferation up to a threshold limit. Furthermore, such level of doping also induced differentiation of the bone cells, which was evident from the higher expression of differentiation markers (Runx2 and Osterix) and better nodule formation (SEM study). Western blot analysis in conjugation with ELISA study confirmed that the doped HAp samples significantly increased the expression of HIF-1α and VEGF in MG-63 cells. The analysis described here confirms the proangiogenic-osteogenic properties of the cobalt doped hydroxyapatite and indicates its potential application in bone tissue engineering. Copyright © 2015 Elsevier B.V. All rights reserved.

Hot pressing of nanocrystalline tantalum using high frequency induction heating and pulse plasma sintering

NASA Astrophysics Data System (ADS)

Jakubowicz, J.; Adamek, G.; Sopata, M.; Koper, J. K.; Siwak, P.

2017-12-01

The paper presents the results of nanocrystalline powder tantalum consolidation using hot pressing. The authors used two different heating techniques during hot pressing: high-frequency induction heating (HFIH) and pulse plasma sintering (PPS). A comparison of the structure, microstructure, mechanical properties and corrosion resistance of the bulk nanocrystalline tantalum obtained in both techniques was performed. The nanocrystalline powder was made to start from the microcrystalline one using the high-energy ball milling process. The nanocrystalline powder was hot-pressed at 1000 °C, whereas, for comparison, the microcrystalline powder was hot pressed up to 1500 °C for proper consolidation. The authors found that during hot pressing, the powder partially reacts with the graphite die covered by boron nitride, which facilitated punches and powder displacement in the die during densification. Tantalum carbide and boride in the nanocrystalline material was found, which can improve the mechanical properties. The hardness of the HFIH and PPS nanocrystalline tantalum was as high as 625 and 615 HV, respectively. The microstructure was more uniform in the PPS nanomaterial. The corrosion resistance in both cases deteriorated, in comparison to the microcrystalline material, while the PPS material corrosion resistance was slightly better than that of the HFIH one.

A protocol for rheological characterization of hydrogels for tissue engineering strategies.

PubMed

Zuidema, Jonathan M; Rivet, Christopher J; Gilbert, Ryan J; Morrison, Faith A

2014-07-01

Hydrogels are studied extensively for many tissue engineering applications, and their mechanical properties influence both cellular and tissue compatibility. However, it is difficult to compare the mechanical properties of hydrogels between studies due to a lack of continuity between rheological protocols. This study outlines a straightforward protocol to accurately determine hydrogel equilibrium modulus and gelation time using a series of rheological tests. These protocols are applied to several hydrogel systems used within tissue engineering applications: agarose, collagen, fibrin, Matrigel™, and methylcellulose. The protocol is outlined in four steps: (1) Time sweep to determine the gelation time of the hydrogel. (2) Strain sweep to determine the linear-viscoelastic region of the hydrogel with respect to strain. (3) Frequency sweep to determine the linear equilibrium modulus plateau of the hydrogel. (4) Time sweep with values obtained from strain and frequency sweeps to accurately report the equilibrium moduli and gelation time. Finally, the rheological characterization protocol was evaluated using a composite Matrigel™-methylcellulose hydrogel blend whose mechanical properties were previously unknown. The protocol described herein provides a standardized approach for proper analysis of hydrogel rheological properties. © 2013 Wiley Periodicals, Inc.

Microstructures and mechanical properties of nanocrystalline NiTi intermetallics formed by mechanosynthesis

NASA Astrophysics Data System (ADS)

Arunkumar, S.; Kumaravel, P.; Velmurugan, C.; Senthilkumar, V.

2018-01-01

The formulation of nanocrystalline NiTi shape memory alloys has potential effects in mechanical stimulation and medical implantology. The present work elucidates the effect of milling time on the product's structural characteristics, chemical composition, and microhardness for NiTi synthesized by mechanical alloying for different milling durations. Increasing the milling duration led to the formation of a nanocrystalline NiTi intermetallic at a higher level. The formation of nanocrystalline materials was directed through cold fusion, fracturing, and the development of a steady state, which were influenced by the accumulation of strain energy. In the morphological study, uninterrupted cold diffusion and fracturing were visualized using transmission electron microscopy. Particle size analysis revealed that the mean particle size was reduced to 93 μm after 20 h of milling. The mechanical strength was enhanced by the formation of a nanocrystalline intermetallic phase at longer milling time, which was confirmed by the results of Vickers hardness analyses.

Biocompatibility of hydroxyapatite scaffolds processed by lithography-based additive manufacturing.

PubMed

Tesavibul, Passakorn; Chantaweroad, Surapol; Laohaprapanon, Apinya; Channasanon, Somruethai; Uppanan, Paweena; Tanodekaew, Siriporn; Chalermkarnnon, Prasert; Sitthiseripratip, Kriskrai

2015-01-01

The fabrication of hydroxyapatite scaffolds for bone tissue engineering applications by using lithography-based additive manufacturing techniques has been introduced due to the abilities to control porous structures with suitable resolutions. In this research, the use of hydroxyapatite cellular structures, which are processed by lithography-based additive manufacturing machine, as a bone tissue engineering scaffold was investigated. The utilization of digital light processing system for additive manufacturing machine in laboratory scale was performed in order to fabricate the hydroxyapatite scaffold, of which biocompatibilities were eventually evaluated by direct contact and cell-culturing tests. In addition, the density and compressive strength of the scaffolds were also characterized. The results show that the hydroxyapatite scaffold at 77% of porosity with 91% of theoretical density and 0.36 MPa of the compressive strength are able to be processed. In comparison with a conventionally sintered hydroxyapatite, the scaffold did not present any cytotoxic signs while the viability of cells at 95.1% was reported. After 14 days of cell-culturing tests, the scaffold was able to be attached by pre-osteoblasts (MC3T3-E1) leading to cell proliferation and differentiation. The hydroxyapatite scaffold for bone tissue engineering was able to be processed by the lithography-based additive manufacturing machine while the biocompatibilities were also confirmed.

Injectable shear-thinning nanoengineered hydrogels for stem cell delivery

NASA Astrophysics Data System (ADS)

Thakur, Ashish; Jaiswal, Manish K.; Peak, Charles W.; Carrow, James K.; Gentry, James; Dolatshahi-Pirouz, Alireza; Gaharwar, Akhilesh K.

2016-06-01

Injectable hydrogels are investigated for cell encapsulation and delivery as they can shield cells from high shear forces. One of the approaches to obtain injectable hydrogels is to reinforce polymeric networks with high aspect ratio nanoparticles such as two-dimensional (2D) nanomaterials. 2D nanomaterials are an emerging class of ultrathin materials with a high degree of anisotropy and they strongly interact with polymers resulting in the formation of shear-thinning hydrogels. Here, we present 2D nanosilicate reinforced kappa-carrageenan (κCA) hydrogels for cellular delivery. κCA is a natural polysaccharide that resembles native glycosaminoglycans and can form brittle hydrogels via ionic crosslinking. The chemical modification of κCA with photocrosslinkable methacrylate groups renders the formation of a covalently crosslinked network (MκCA). Reinforcing the MκCA with 2D nanosilicates results in shear-thinning characteristics, and enhanced mechanical stiffness, elastomeric properties, and physiological stability. The shear-thinning characteristics of nanocomposite hydrogels are investigated for human mesenchymal stem cell (hMSC) delivery. The hMSCs showed high cell viability after injection and encapsulated cells showed a circular morphology. The proposed shear-thinning nanoengineered hydrogels can be used for cell delivery for cartilage tissue regeneration and 3D bioprinting.

Density gradients at hydrogel interfaces for enhanced cell penetration.

PubMed

Simona, B R; Hirt, L; Demkó, L; Zambelli, T; Vörös, J; Ehrbar, M; Milleret, V

2015-04-01

We report that stiffness gradients facilitate infiltration of cells through otherwise cell-impermeable hydrogel interfaces. By enabling the separation of hydrogel manufacturing and cell seeding, and by improving cell colonization of additively manufactured hydrogel elements, interfacial density gradients present a promising strategy to progress in the creation of 3D tissue models.

Polymer blend of PLA/PHBV based bionanocomposites reinforced with nanocrystalline cellulose for potential application as packaging material.

PubMed

Dasan, Y K; Bhat, A H; Ahmad, Faiz

2017-02-10

The current research discusses the development of poly (lactic acid) (PLA) and poly-(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) reinforced nanocrystalline cellulose bionanocomposites. The nanocrystalline cellulose was derived from waste oil palm empty fruit bunch fiber by acid hydrolysis process. The resulting nanocrystalline cellulose suspension was then surface functionalized by TEMPO-mediated oxidation and solvent exchange process. Furthermore, the PLA/PHBV/nanocrystalline cellulose bionanocomposites were produced by solvent casting method. The effect of the addition of nanocrystalline cellulose on structural, morphology, mechanical and barrier properties of bionanocomposites was investigated. The results revealed that the developed bionanocomposites showed improved mechanical properties and decrease in oxygen permeability rate. Therefore, the developed bio-based composite incorporated with an optimal composition of nanocrystalline cellulose exhibits properties as compared to the polymer blend. Copyright © 2016 Elsevier Ltd. All rights reserved.

Design and development of hydrogel nanoparticles for mercaptopurine

PubMed Central

Senthil, V.; Kumar, R. Suresh; Nagaraju, C. V. V.; Jawahar, N.; Ganesh, G. N. K.; Gowthamarajan, K.

2010-01-01

Hydrogel nanoparticles have gained attention in recent years as they demonstrate the features and characters of hydrogels and nanoparticles at the same time. In the present study chitosan and carrageenan have been used, as hydrogel nanoparticles of mercaptopurine are developed using natural, biodegradable, and biocompatible polymers like chitosan and carrageenan. As these polymers are hydrophilic in nature, the particles will have a long life span in systemic circulation. Hydrogel nanoparticles with mercaptopurine is form an antileukemia drug by the counter polymer gelation method. Fourier-Transform Infrared (FT-IR) studies have shown a compatibility of polymers with the drug. The diameter of hydrogel nanoparticles was about 370 – 800 nm with a positive zeta potential of 26 – 30 mV. The hydrogel nanoparticles were almost spherical in shape, as revealed by scanning electron microscopy (SEM). Drug loading varied from 9 to 17%. Mercaptopurine released from the nanoparticles at the end of the twenty-fourth hour was about 69.48 – 76.52% at pH 7.4. The drug release from the formulation was following zero order kinetics, which was evident from the release kinetic studies and the mechanism of drug release was anomalous diffusion, which indicated that the drug release was controlled by more than one process. PMID:22247867

Reinforcing the inner phase of the filled hydrogels with CNTs alters drug release properties and human keratinocyte morphology: A study on the gelatin- tamarind gum filled hydrogels.

PubMed

Maharana, Vivek; Gaur, Deepanjali; Nayak, Suraj K; Singh, Vinay K; Chakraborty, Subhabrata; Banerjee, Indranil; Ray, Sirsendu S; Anis, Arfat; Pal, Kunal

2017-11-01

The study reports the synthesis and characterization of gelatin-tamarind gum (TG) based filled hydrogels for drug delivery applications. In this study, three different types of carbon nanotubes (CNTs) were incorporated within the dispersed TG phase of the filled hydrogels. The prepared hydrogels were thoroughly characterised using bright field microscope, FESEM, FTIR spectroscopy, differential scanning calorimeter, and mechanical tester. The swelling and the drug (salicylic acid) release properties of the filled hydrogels were also evaluated. The micrographs revealed the formation of biphasic systems. The internal phase appeared as agglomerates, and the CNTs were confined within the dispersed TG phase. FTIR and XRD studies revealed that CNTs promoted associative interactions among the components of the hydrogel, which promoted the formation of large crystallite size. The mechanical study indicated better resistance to the breakdown of the architecture of the CNT-containing filled hydrogels. Drug release studies, both passive and iontophoretic, suggested that the non-Fickian diffusion of the drug was prevalent during its release from hydrogel matrices. The prepared hydrogels were cytocompatible with human keratinocytes. The results suggested the probable use of such hydrogels in wound healing, tissue engineering and drug delivery applications. Copyright © 2017 Elsevier Ltd. All rights reserved.

Ultrasound stimulated release of mimosa medicine from cellulose hydrogel matrix.

PubMed

Jiang, Huixin; Tovar-Carrillo, Karla; Kobayashi, Takaomi

2016-09-01

Ultrasound (US) drug release system using cellulose based hydrogel films was developed as triggered to mimosa. Here, the mimosa, a fascinating drug to cure injured skin, was employed as the loading drug in cellulose hydrogel films prepared with phase inversion method. The mimosa hydrogels were fabricated from dimethylacetamide (DMAc)/LiCl solution in the presence of mimosa, when the solution was exposed to ethanol vapor. The US triggered release of the mimosa from the hydrogel matrix was carried out under following conditions of US powers (0-30W) and frequencies (23, 43 and 96kHz) for different mimosa hydrogel matrix from 0.5wt% to 2wt% cellulose solution. To release the drug by US trigger from the matrix, the better medicine release was observed in the matrix prepared from the 0.5wt% cellulose solution when the 43kHz US was exposed to the aqueous solution with the hydrogel matrix. The release efficiency increased with the increase of the US power from 5 to 30W at 43kHz. Viscoelasticity of the hydrogel matrix showed that the hydrogel became somewhat rigid after the US exposure. FT-IR analysis of the mimosa hydrogel matrixes showed that during the US exposure, hydrogen bonds in the structure of mimosa-water and mimosa-cellulose were broken. This suggested that the enhancement of the mimosa release was caused by the US exposure. Copyright © 2016 Elsevier B.V. All rights reserved.

Gellan gum-based hydrogels for intervertebral disc tissue-engineering applications.

PubMed

Silva-Correia, J; Oliveira, J M; Caridade, S G; Oliveira, J T; Sousa, R A; Mano, J F; Reis, R L

2011-06-01

Intervertebral disc (IVD) degeneration is a challenging clinical problem that urgently demands viable nucleus pulposus (NP) implant materials. The best suited biomaterial for NP regeneration has yet to be identified, but it is believed that biodegradable hydrogel-based materials are promising candidates. In this work, we have developed ionic- and photo-crosslinked methacrylated gellan gum (GG-MA) hydrogels to be used in acellular and cellular tissue-engineering strategies for the regeneration of IVDs. The physicochemical properties of the developed hydrogels were investigated by Fourier-transform infrared spectroscopy, (1) H nuclear magnetic resonance and differential scanning calorimetry. The swelling ability and degradation rate of hydrogels were also analysed in phosphate-buffered saline solution at physiological pH for a period of 30 days. Additionally, the morphology and mechanical properties of the hydrogels were assessed under a scanning electron microscope and dynamic compression, respectively. An in vitro study was carried out to screen possible cytotoxicity of the gellan gum-based hydrogels by culturing rat lung fibroblasts (L929 cells) with hydrogel leachables up to 7 days. The results demonstrated that gellan gum was successfully methacrylated. We observed that the produced GG-MA hydrogels possess improved mechanical properties and lower water uptake ability and degradation rate as compared to gellan gum. This work also revealed that GG-MA hydrogels are non-cytotoxic in vitro, thus being promising biomaterials to be used in IVD tissue-engineering strategies. Copyright © 2010 John Wiley & Sons, Ltd.

Three-dimensional bioprinting of complex cell laden alginate hydrogel structures.

PubMed

Tabriz, Atabak Ghanizadeh; Hermida, Miguel A; Leslie, Nicholas R; Shu, Wenmiao

2015-12-21

Different bioprinting techniques have been used to produce cell-laden alginate hydrogel structures, however these approaches have been limited to 2D or simple three-dimension (3D) structures. In this study, a new extrusion based bioprinting technique was developed to produce more complex alginate hydrogel structures. This was achieved by dividing the alginate hydrogel cross-linking process into three stages: primary calcium ion cross-linking for printability of the gel, secondary calcium cross-linking for rigidity of the alginate hydrogel immediately after printing and tertiary barium ion cross-linking for long-term stability of the alginate hydrogel in culture medium. Simple 3D structures including tubes were first printed to ensure the feasibility of the bioprinting technique and then complex 3D structures such as branched vascular structures were successfully printed. The static stiffness of the alginate hydrogel after printing was 20.18 ± 1.62 KPa which was rigid enough to sustain the integrity of the complex 3D alginate hydrogel structure during the printing. The addition of 60 mM barium chloride was found to significantly extend the stability of the cross-linked alginate hydrogel from 3 d to beyond 11 d without compromising the cellular viability. The results based on cell bioprinting suggested that viability of U87-MG cells was 93 ± 0.9% immediately after bioprinting and cell viability maintained above 88% ± 4.3% in the alginate hydrogel over the period of 11 d.

A novel gelatin hydrogel carrier sheet for corneal endothelial transplantation.

PubMed

Watanabe, Ryou; Hayashi, Ryuhei; Kimura, Yu; Tanaka, Yuji; Kageyama, Tomofumi; Hara, Susumu; Tabata, Yasuhiko; Nishida, Kohji

2011-09-01

We examined the feasibility of using gelatin hydrogels as carrier sheets for the transplantation of cultivated corneal endothelial cells. The mechanical properties, transparency, and permeability of gelatin hydrogel sheets were compared with those of atelocollagen sheets. Immunohistochemistry (ZO-1, Na(+)/K(+)-ATPase, and N-cadherin), hematoxylin and eosin staining, and scanning electron microscopy were performed to assess the integrity of corneal endothelial cells that were cultured on gelatin hydrogel sheets. The gelatin hydrogel sheets displayed greater transparency, elastic modulus, and albumin permeability compared to those of atelocollagen sheets. The corneal endothelial cells on gelatin hydrogel sheets showed normal expression levels of ZO-1, Na(+)/K(+)-ATPase, and N-cadherin. Hematoxylin and eosin staining revealed the formation of a continuous monolayer of cells attached to the gelatin hydrogel sheet. Scanning electron microscopy observations showed that the corneal endothelial cells were arranged in a regular, mosaic, and polygonal pattern with normal cilia. These results indicate that the gelatin hydrogel sheet is a promising material to transport corneal endothelial cells during transplantation.

On the anisotropic elastic properties of hydroxyapatite.

NASA Technical Reports Server (NTRS)

Katz, J. L.; Ukraincik, K.

1971-01-01

Experimental measurements of the isotropic elastic moduli on polycrystalline specimens of hydroxyapatite and fluorapatite are compared with elastic constants measured directly from single crystals of fluorapatite in order to derive a set of pseudo single crystal elastic constants for hydroxyapatite. The stiffness coefficients thus derived are given. The anisotropic and isotropic elastic properties are then computed and compared with similar properties derived from experimental observations of the anisotropic behavior of bone.

Thermo-responsive hydrogels for intravitreal injection and biomolecule release

NASA Astrophysics Data System (ADS)

Drapala, Pawel

In this dissertation, we develop an injectable polymer system to enable localized and prolonged release of therapeutic biomolecules for improved treatment of Age-Related Macular Degeneration (AMD). Thermo-responsive hydrogels derived from N-isopropylacrylamide (NIPAAm) and cross-linked with poly(ethylene glycol) (PEG) poly(L-Lactic acid) (PLLA) copolymer were synthesized via free-radical polymerization. These materials were investigated for (a) phase change behavior, (b) in-vitro degradation, (c) capacity for controlled drug delivery, and (d) biocompatibility. The volume-phase transition temperature (VPTT) of the PNIPAAm- co-PEG-b-PLLA hydrogels was adjusted using hydrophilic and hydrophobic moieties so that it is ca. 33°C. These hydrogels did not initially show evidence of degradation at 37°C due to physical cross-links of collapsed PNIPAAm. Only after addition of glutathione chain transfer agents (CTA)s to the precursor did the collapsed hydrogels become fully soluble at 37°C. CTAs significantly affected the release kinetics of biomolecules; addition of 1.0 mg/mL glutathione to 3 mM cross-linker accelerated hydrogel degradation, resulting in 100% release in less than 2 days. This work also explored the effect of PEGylation in order to tether biomolecules to the polymer matrix. It was demonstrated that non-site-specific PEGylation can postpone the burst release of solutes (up to 10 days in hydrogels with 0.5 mg/mL glutathione). Cell viability assays showed that at least two 20-minute buffer extraction steps were needed to remove cytotoxic elements from the hydrogels. Clinically-used therapeutic biomolecules LucentisRTM and AvastinRTM were demonstrated to be both stable and bioactive after release form PNIPAAm-co-PEG-b-PLLA hydrogels. The thermo-responsive hydrogels presented here offer a promising platform for the localized delivery of proteins such as recombinant antibodies.

An Injectable, Self-Healing Hydrogel to Repair the Central Nervous System.

PubMed

Tseng, Ting-Chen; Tao, Lei; Hsieh, Fu-Yu; Wei, Yen; Chiu, Ing-Ming; Hsu, Shan-hui

2015-06-17

An injectable, self-healing hydrogel (≈1.5 kPa) is developed for healing nerve-system deficits. Neurosphere-like progenitors proliferate in the hydrogel and differentiate into neuron-like cells. In the zebrafish injury model, the central nervous system function is partially rescued by injection of the hydrogel and significantly rescued by injection of the neurosphere-laden hydrogel. The self-healing hydrogel may thus potentially repair the central nervous system. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Weak Bond-Based Injectable and Stimuli Responsive Hydrogels for Biomedical Applications

PubMed Central

Ding, Xiaochu; Wang, Yadong

2017-01-01

Here we define hydrogels crosslinked by weak bonds as physical hydrogels. They possess unique features including reversible bonding, shear thinning and stimuli-responsiveness. Unlike covalently crosslinked hydrogels, physical hydrogels do not require triggers to initiate chemical reactions for in situ gelation. The drug can be fully loaded in a pre-formed hydrogel for delivery with minimal cargo leakage during injection. These benefits make physical hydrogels useful as delivery vehicles for applications in biomedical engineering. This review focuses on recent advances of physical hydrogels crosslinked by weak bonds: hydrogen bonds, ionic interactions, host-guest chemistry, hydrophobic interactions, coordination bonds and π-π stacking interactions. Understanding the principles and the state of the art of gels with these dynamic bonds may give rise to breakthroughs in many biomedical research areas including drug delivery and tissue engineering. PMID:29062484

Framework Stability of Nanocrystalline NaY in Aqueous Solution at Varying pH

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

Petushkov, Anton; Freeman, Jasmine; Larsen, Sarah C.

Nanocrystalline zeolites (with crystal sizes of less than 50 nm) are versatile, porous nanomaterials with potential applications in a broad range of areas including bifunctional catalysis, drug delivery, environmental protection, and sensing, to name a few. The characterization of the properties of nanocrystalline zeolites on a fundamental level is critical to the realization of these innovative applications. Nanocrystalline zeolites have unique surface chemistry that is distinct from conventional microcrystalline zeolite materials and that will result in novel applications. In the proposed work, magnetic resonance techniques (solid state nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR)) will be used tomore » elucidate the structure and reactivity of nanocrystalline zeolites and to motivate bifunctional applications. Density functional theory (DFT) calculations will enhance data interpretation through chemical shift, quadrupole coupling constant, g-value and hyperfine calculations.« less

Engineering Protein Hydrogels Using SpyCatcher-SpyTag Chemistry.

PubMed

Gao, Xiaoye; Fang, Jie; Xue, Bin; Fu, Linglan; Li, Hongbin

2016-09-12

Constructing hydrogels from engineered proteins has attracted significant attention within the material sciences, owing to their myriad potential applications in biomedical engineering. Developing efficient methods to cross-link tailored protein building blocks into hydrogels with desirable mechanical, physical, and functional properties is of paramount importance. By making use of the recently developed SpyCatcher-SpyTag chemistry, we successfully engineered protein hydrogels on the basis of engineered tandem modular elastomeric proteins. Our resultant protein hydrogels are soft but stable, and show excellent biocompatibility. As the first step, we tested the use of these hydrogels as a drug carrier, as well as in encapsulating human lung fibroblast cells. Our results demonstrate the robustness of the SpyCatcher-SpyTag chemistry, even when the SpyTag (or SpyCatcher) is flanked by folded globular domains. These results demonstrate that SpyCatcher-SpyTag chemistry can be used to engineer protein hydrogels from tandem modular elastomeric proteins that can find applications in tissue engineering, in fundamental mechano-biological studies, and as a controlled drug release vehicle.

Transient Dynamic Mechanical Analysis of Resilin-based Elastomeric Hydrogels

NASA Astrophysics Data System (ADS)

Li, Linqing; Kiick, Kristi

2014-04-01

The outstanding high-frequency properties of emerging resilin-like polypeptides (RLPs) have motivated their development for vocal fold tissue regeneration and other applications. Recombinant RLP hydrogels show efficient gelation, tunable mechanical properties, and display excellent extensibility, but little has been reported about their transient mechanical properties. In this manuscript, we describe the transient mechanical behavior of new RLP hydrogels investigated via both sinusoidal oscillatory shear deformation and uniaxial tensile testing. Oscillatory stress relaxation and creep experiments confirm that RLP-based hydrogels display significantly reduced stress relaxation and improved strain recovery compared to PEG-based control hydrogels. Uniaxial tensile testing confirms the negligible hysteresis, reversible elasticity and superior resilience (up to 98%) of hydrated RLP hydrogels, with Young’s modulus values that compare favorably with those previously reported for resilin and that mimic the tensile properties of the vocal fold ligament at low strain (< 15%). These studies expand our understanding of the properties of these RLP materials under a variety of conditions, and confirm the unique applicability, for mechanically demanding tissue engineering applications, of a range of RLP hydrogels.

Microplasma-assisted hydrogel fabrication: A novel method for gelatin-graphene oxide nano composite hydrogel synthesis for biomedical application

PubMed Central

2017-01-01

Toxicity issues and biocompatibility concerns with traditional classical chemical cross-linking processes prevent them from being universal approaches for hydrogel fabrication for tissue engineering. Physical cross-linking methods are non-toxic and widely used to obtain cross-linked polymers in a tunable manner. Therefore, in the current study, argon micro-plasma was introduced as a neutral energy source for cross-linking in fabrication of the desired gelatin-graphene oxide (gel-GO) nanocomposite hydrogel scaffolds. Argon microplasma was used to treat purified gelatin (8% w/v) containing 0.1∼1 wt% of high-functionality nano-graphene oxide (GO). Optimized plasma conditions (2,500 V and 8.7 mA) for 15 min with a gas flow rate of 100 standard cm3/min was found to be most suitable for producing the gel-GO nanocomposite hydrogels. The developed hydrogel was characterized by the degree of cross-linking, FTIR spectroscopy, SEM, confocal microscopy, swelling behavior, contact angle measurement, and rheology. The cell viability was examined by an MTT assay and a live/dead assay. The pore size of the hydrogel was found to be 287 ± 27 µm with a contact angle of 78° ± 3.7°. Rheological data revealed improved storage as well as a loss modulus of up to 50% with tunable viscoelasticity, gel strength, and mechanical properties at 37 °C temperature in the microplasma-treated groups. The swelling behavior demonstrated a better water-holding capacity of the gel-GO hydrogels for cell growth and proliferation. Results of the MTT assay, microscopy, and live/dead assay exhibited better cell viability at 1% (w/w) of high-functionality GO in gelatin. The highlight of the present study is the first successful attempt of microplasma-assisted gelatin-GO nano composite hydrogel fabrication that offers great promise and optimism for further biomedical tissue engineering applications. PMID:28663938

The precursors effects on biomimetic hydroxyapatite ceramic powders.

PubMed

Yoruç, Afife Binnaz Hazar; Aydınoğlu, Aysu

2017-06-01

In this study, effects of the starting material on chemical, physical, and biological properties of biomimetic hydroxyapatite ceramic powders (BHA) were investigated. Characterization and chemical analysis of BHA powders were performed by using XRD, FT-IR, and ICP-AES. Microstructural features such as size and morphology of the resulting BHA powders were characterized by using BET, nano particle sizer, pycnometer, and SEM. Additionally, biological properties of the BHA ceramic powders were also investigated by using water-soluble tetrazolium salts test (WST-1). According to the chemical analysis of BHA ceramic powders, chemical structures of ceramics which are prepared under different conditions and by using different starting materials show differences. Ceramic powders which are produced at 80°C are mainly composed of hydroxyapatite, dental hydroxyapatite (contain Na and Mg elements in addition to Ca), and calcium phosphate sulfide. However, these structures are altered at high temperatures such as 900°C depending on the features of starting materials and form various calcium phosphate ceramics and/or their mixtures such as Na-Mg-hydroxyapatite, hydroxyapatite, Mg-Whitlockit, and chloroapatite. In vitro cytotoxicity studies showed that amorphous ceramics produced at 80°C and ceramics containing chloroapatite structure as main or secondary phases were found to be extremely cytotoxic. Furthermore, cell culture studies showed that highly crystalline pure hydroxyapatite structures were extremely cytotoxic due to their high crystallinity values. Consequently, the current study indicates that the selection of starting materials which can be used in the production of calcium phosphate ceramics is very important. It is possible to produce calcium phosphate ceramics which have sufficient biocompatibility at physiological pH values and by using appropriate starting materials. Copyright © 2017 Elsevier B.V. All rights reserved.

Electrodeposition of Nanocrystalline Cobalt Phosphorous Coatings as a Hard Chrome Alternative

DTIC Science & Technology

2014-11-01

1 ASETSDefense 2014 Electrodeposition of Nanocrystalline Cobalt Phosphorous Coatings as a Hard Chrome Alternative Ruben A. Prado, CEF...COVERED 00-00-2014 to 00-00-2014 4. TITLE AND SUBTITLE Electrodeposition of Nanocrystalline Cobalt Phosphorous Coatings as a Hard Chrome Alternative...coatings as a Hard Chrome (EHC) electroplating alternative for DoD manufacturing and repair. – Fully define deposition parameters and properties

Biomimetic membrane arrays on cast hydrogel supports.

PubMed

Roerdink Lander, Monique; Ibragimova, Sania; Rein, Christian; Vogel, Jörg; Stibius, Karin; Geschke, Oliver; Perry, Mark; Hélix-Nielsen, Claus

2011-06-07

Lipid bilayers are intrinsically fragile and require mechanical support in technical applications based on biomimetic membranes. Tethering the lipid bilayer membranes to solid substrates, either directly through covalent or ionic substrate-lipid links or indirectly on substrate-supported cushions, provides mechanical support but at the cost of small molecule transport through the membrane-support sandwich. To stabilize biomimetic membranes while allowing transport through a membrane-support sandwich, we have investigated the feasibility of using an ethylene tetrafluoroethylene (ETFE)/hydrogel sandwich as the support. The sandwich is realized as a perforated surface-treated ETFE film onto which a hydrogel composite support structure is cast. We report a simple method to prepare arrays of lipid bilayer membranes with low intrinsic electrical conductance on the highly permeable, self-supporting ETFE/hydrogel sandwiches. We demonstrate how the ETFE/hydrogel sandwich support promotes rapid self-thinning of lipid bilayers suitable for hosting membrane-spanning proteins.

Mechanically enhanced nested-network hydrogels as a coating material for biomedical devices.

PubMed

Wang, Zhengmu; Zhang, Hongbin; Chu, Axel J; Jackson, John; Lin, Karen; Lim, Chinten James; Lange, Dirk; Chiao, Mu

2018-04-01

Well-organized composite formations such as hierarchical nested-network (NN) structure in bone tissue and reticular connective tissue present remarkable mechanical strength and play a crucial role in achieving physical and biological functions for living organisms. Inspired by these delicate microstructures in nature, an analogous scaffold of double network hydrogel was fabricated by creating a poly(2-hydroxyethyl methacrylate) (pHEMA) network in the porous structure of alginate hydrogels. The resulting hydrogel possessed hierarchical NN structure and showed significantly improved mechanical strength but still maintained high elasticity comparable to soft tissues due to a mutual strengthening effect between the two networks. The tough hydrogel is also self-lubricated, exhibiting a surface friction coefficient comparable with polydimethylsiloxane (PDMS) substrates lubricated by a commercial aqueous lubricant (K-Y Jelly) and other low surface friction hydrogels. Additional properties of this hydrogel include high hydrophilicity, good biocompatibility, tunable cell adhesion and bacterial resistance after incorporation of silver nanoparticles. Firm bonding of the hydrogel on silicone substrates could be achieved through facile chemical modification, thus enabling the use of this hydrogel as a versatile coating material for biomedical applications. In this study, we developed a tough hydrogel by crosslinking HEMA monomers in alginate hydrogels and forming a well-organized structure of hierarchical nested network (NN). Different from most reported stretchable alginate-based hydrogels, the NN hydrogel shows higher compressive strength but retains comparable softness to alginate counterparts. This work further demonstrated the good integration of the tough hydrogel with silicone substrates through chemical modification and micropillar structures. Other properties including surface friction, biocompatibility and bacterial resistance were investigated and the hydrogel shows

Model for temperature-dependent magnetization of nanocrystalline materials

NASA Astrophysics Data System (ADS)

Bian, Q.; Niewczas, M.

2015-01-01

A magnetization model of nanocrystalline materials incorporating intragrain anisotropies, intergrain interactions, and texture effects has been extended to include the thermal fluctuations. The method relies on the stochastic Landau-Lifshitz-Gilbert theory of magnetization dynamics and permits to study the magnetic properties of nanocrystalline materials at arbitrary temperature below the Currie temperature. The model has been used to determine the intergrain exchange constant and grain boundary anisotropy constant of nanocrystalline Ni at 100 K and 298 K. It is found that the thermal fluctuations suppress the strength of the intergrain exchange coupling and also reduce the grain boundary anisotropy. In comparison with its value at 2 K, the interparticle exchange constant decreases by 16% and 42% and the grain boundary anisotropy constant decreases by 28% and 40% at 100 K and 298 K, respectively. An application of the model to study the grain size-dependent magnetization indicates that when the thermal activation energy is comparable to the free energy of grains, the decrease in the grain size leads to the decrease in the magnetic permeability and saturation magnetization. The mechanism by which the grain size influences the magnetic properties of nc-Ni is discussed.

Formation of pyrophosphate on hydroxyapatite with thioesters as condensing agents

NASA Technical Reports Server (NTRS)

Weber, A. L.

1982-01-01

'Energy-rich' thioesters are shown to act as condensing agents in the formation of pyrophosphate on hydroxyapatite in the presence of water at ambient temperature. The yield of pyrophosphate based on thioester ranges from 2.5% to 11.4% and depends upon the pH and concentration of reactants. Reaction of 0.130 M hydroxyapatite suspended in a solution of 0.08 M sodium phosphate and 0.20 M imidazole hydrochloride (pH 7.0) with 0.10 M N,S-diacetylcysteamine for 6 days gives the highest yield of pyrophosphate (11.4%). Pyrophosphate formation requires the presence of hydroxyapatite, sodium phosphate and the thioester, N,S-diacetylcysteamine. The related thioester, N,S-diacetylcysteine, also yields pyrophosphate in reactions on hydroxyapatite.

Continuous microwave flow synthesis of mesoporous hydroxyapatite.

PubMed

Akram, Muhammad; Alshemary, Ammar Z; Goh, Yi-Fan; Wan Ibrahim, Wan Aini; Lintang, Hendrik O; Hussain, Rafaqat

2015-11-01

We have successfully used continuous microwave flow synthesis (CMFS) technique for the template free synthesis of mesoporous hydroxyapatite. The continuous microwave flow reactor consisted of a modified 2.45GHz household microwave, peristaltic pumps and a Teflon coil. This cost effective and efficient system was exploited to produce semi-crystalline phase pure nano-sized hydroxyapatite. Effect of microwave power, retention time and the concentration of reactants on the phase purity, degree of crystallinity and surface area of the final product was studied in detail. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) were used to study the phase purity and composition of the product, while transmission electron microscopy (TEM) was used to study the effect of process parameters on the morphology of hydroxyapatite. The TEM analysis confirmed the formation of spherical particles at low microwave power; however the morphology of the particles changed to mesoporous needle and rod-like structure upon exposing the reaction mixture to higher microwave power and longer retention time inside the microwave. The in-vitro ion dissolution behavior of the as synthesized hydroxyapatite was studied by determining the amount of Ca(2+) ion released in SBF solution. Copyright © 2015 Elsevier B.V. All rights reserved.

Methods To Assess Shear-Thinning Hydrogels for Application As Injectable Biomaterials

PubMed Central

2017-01-01

Injectable hydrogels have gained popularity as a vehicle for the delivery of cells, growth factors, and other molecules to localize and improve their retention at the injection site, as well as for the mechanical bulking of tissues. However, there are many factors, such as viscosity, storage and loss moduli, and injection force, to consider when evaluating hydrogels for such applications. There are now numerous tools that can be used to quantitatively assess these factors, including for shear-thinning hydrogels because their properties change under mechanical load. Here, we describe relevant rheological tests and ways to measure injection force using a force sensor or a mechanical testing machine toward the evaluation of injectable hydrogels. Injectable, shear-thinning hydrogels can be used in a variety of clinical applications, and as an example we focus on methods for injection into the heart, where an understanding of injection properties and mechanical forces is imperative for consistent hydrogel delivery and retention. We discuss methods for delivery of hydrogels to mouse, rat, and pig hearts in models of myocardial infarction, and compare methods of tissue postprocessing for hydrogel preservation. Our intent is that the methods described herein can be helpful in the design and assessment of shear-thinning hydrogels for widespread biomedical applications. PMID:29250593

Anisotropic contraction of hydrogel reinforced by aligned fibers

NASA Astrophysics Data System (ADS)

Olvera de La Cruz, Monica; Liu, Shuangping

Hydrogel reinforced by aligned fibers can have strong anisotropic contraction or swelling behavior triggered by external stimuli, which has been largely employed in realizing soft actuators for artificial muscles as well as many biological systems. In this work, we investigate how this anisotropic behavior is controlled by the dimension of the embedded fibers and their reinforcement to the surrounding hydrogel. We describe the anisotropic contraction of hydrogels with rigid fibers using the Flory-Rehner thermodynamic model under periodic boundary conditions. It is found that a hydrogel reinforced by aligned fibers exhibits larger anisotropy when it is pre-stretched before contraction. Using finite element method, we further observe that the anisotropic contraction is dampened by reducing the fiber-fiber distance due to the finite size of the fibers.

Hydraulic hydrogel actuators and robots optically and sonically camouflaged in water.

PubMed

Yuk, Hyunwoo; Lin, Shaoting; Ma, Chu; Takaffoli, Mahdi; Fang, Nicolas X; Zhao, Xuanhe

2017-02-01

Sea animals such as leptocephali develop tissues and organs composed of active transparent hydrogels to achieve agile motions and natural camouflage in water. Hydrogel-based actuators that can imitate the capabilities of leptocephali will enable new applications in diverse fields. However, existing hydrogel actuators, mostly osmotic-driven, are intrinsically low-speed and/or low-force; and their camouflage capabilities have not been explored. Here we show that hydraulic actuations of hydrogels with designed structures and properties can give soft actuators and robots that are high-speed, high-force, and optically and sonically camouflaged in water. The hydrogel actuators and robots can maintain their robustness and functionality over multiple cycles of actuations, owing to the anti-fatigue property of the hydrogel under moderate stresses. We further demonstrate that the agile and transparent hydrogel actuators and robots perform extraordinary functions including swimming, kicking rubber-balls and even catching a live fish in water.

Hydraulic hydrogel actuators and robots optically and sonically camouflaged in water

NASA Astrophysics Data System (ADS)

Yuk, Hyunwoo; Lin, Shaoting; Ma, Chu; Takaffoli, Mahdi; Fang, Nicolas X.; Zhao, Xuanhe

2017-02-01

Sea animals such as leptocephali develop tissues and organs composed of active transparent hydrogels to achieve agile motions and natural camouflage in water. Hydrogel-based actuators that can imitate the capabilities of leptocephali will enable new applications in diverse fields. However, existing hydrogel actuators, mostly osmotic-driven, are intrinsically low-speed and/or low-force; and their camouflage capabilities have not been explored. Here we show that hydraulic actuations of hydrogels with designed structures and properties can give soft actuators and robots that are high-speed, high-force, and optically and sonically camouflaged in water. The hydrogel actuators and robots can maintain their robustness and functionality over multiple cycles of actuations, owing to the anti-fatigue property of the hydrogel under moderate stresses. We further demonstrate that the agile and transparent hydrogel actuators and robots perform extraordinary functions including swimming, kicking rubber-balls and even catching a live fish in water.

Keratin sponge/hydrogel II, active agent delivery

USDA-ARS?s Scientific Manuscript database

Keratin sponge/hydrogels from oxidation and reduction hydrolysis of fine and coarse wool fibers were formed to behave as cationic hydrogels to swell and release active agents in the specific region of the gastro-intestinal (GI) tract. Their porous, interpenetrating networks (IPN) were effective for...

Construction of Injectable Double-Network Hydrogels for Cell Delivery.

PubMed

Yan, Yan; Li, Mengnan; Yang, Di; Wang, Qian; Liang, Fuxin; Qu, Xiaozhong; Qiu, Dong; Yang, Zhenzhong

2017-07-10

Herein we present a unique method of using dynamic cross-links, which are dynamic covalent bonding and ionic interaction, for the construction of injectable double-network (DN) hydrogels, with the objective of cell delivery for cartilage repair. Glycol chitosan and dibenzaldhyde capped poly(ethylene oxide) formed the first network, while calcium alginate formed the second one, and in the resultant DN hydrogel, either of the networks could be selectively removed. The moduli of the DN hydrogel were significantly improved compared to that of the parent single-network hydrogels and were tunable by changing the chemical components. In situ 3D cell encapsulation could be easily performed by mixing cell suspension to the polymer solutions and transferred through a syringe needle before sol-gel transition. Cell proliferation and mediated differentiation of mouse chondrogenic cells were achieved in the DN hydrogel extracellular matrix.

Cell encapsulation in biodegradable hydrogels for tissue engineering applications.

PubMed

Nicodemus, Garret D; Bryant, Stephanie J

2008-06-01

Encapsulating cells in biodegradable hydrogels offers numerous attractive features for tissue engineering, including ease of handling, a highly hydrated tissue-like environment for cell and tissue growth, and the ability to form in vivo. Many properties important to the design of a hydrogel scaffold, such as swelling, mechanical properties, degradation, and diffusion, are closely linked to the crosslinked structure of the hydrogel, which is controlled through a variety of different processing conditions. Degradation may be tuned by incorporating hydrolytically or enzymatically labile segments into the hydrogel or by using natural biopolymers that are susceptible to enzymatic degradation. Because cells are present during the gelation process, the number of suitable chemistries and formulations are limited. In this review, we describe important considerations for designing biodegradable hydrogels for cell encapsulation and highlight recent advances in material design and their applications in tissue engineering.

[PREPARATION AND BIOCOMPATIBILITY OF IN SITU CROSSLINKING HYALURONIC ACID HYDROGEL].

PubMed

Liang, Jiabi; Li, Jun; Wang, Ting; Liang, Yuhong; Zou, Xuenong; Zhou, Guangqian; Zhou, Zhiyu

2016-06-08

To fabricate in situ crosslinking hyaluronic acid hydrogel and evaluate its biocompatibility in vitro. The acrylic acid chloride and polyethylene glycol were added to prepare crosslinking agent polyethylene glycol acrylate (PEGDA), and the molecular structure of PEGDA was analyzed by Flourier transformation infrared spectroscopy and 1H nuclear magnetic resonance spectroscopy. Hyaluronic acid hydrogel was chemically modified to prepare hyaluronic acid thiolation (HA-SH). And the degree of HA-SH was analyzed qualitatively and quantitatively by Ellman method. HA-SH solution in concentrations ( W/V ) of 0.5%, 1.0%, and 1.5% and PEGDA solution in concentrations ( W/V ) of 2%, 4%, and 6% were prepared with PBS. The two solutions were mixed in different ratios, and in situ crosslinking hyaluronic acid hydrogel was obtained; the crosslinking time was recorded. The cellular toxicity of in situ crosslinking hyaluronic acid hydrogel (1.5% HA-SH and 4% PEGDA mixed) was tested by L929 cells. Meanwhile, the biocompatibility of hydrogel was tested by co-cultured with human bone mesenchymal stem cells (hBMSCs). Flourier transformation infrared spectroscopy showed that most hydroxyl groups were replaced by acrylate groups; 1H nuclear magnetic resonance spectroscopy showed 3 characteristic peaks of hydrogen representing acrylate and olefinic bond at 5-7 ppm. The thiolation yield of HA-SH was 65.4%. In situ crosslinking time of hyaluronic acid hydrogel was 2 to 70 minutes in the PEGDA concentrations of 2%-6% and HA-SH concentrations of 0.5%-1.5%. The hyaluronic acid hydrogel appeared to be transparent. The toxicity grade of leaching solution of hydrogel was grade 1. hBMSCs grew well and distributed evenly in hydrogel with a very high viability. In situ crosslinking hyaluronic acid hydrogel has low cytotoxicity, good biocompatibility, and controllable crosslinking time, so it could be used as a potential tissue engineered scaffold or repairing material for tissue regeneration.

Sundew-Inspired Adhesive Hydrogels Combined with Adipose-Derived Stem Cells for Wound Healing.

PubMed

Sun, Leming; Huang, Yujian; Bian, Zehua; Petrosino, Jennifer; Fan, Zhen; Wang, Yongzhong; Park, Ki Ho; Yue, Tao; Schmidt, Michael; Galster, Scott; Ma, Jianjie; Zhu, Hua; Zhang, Mingjun

2016-01-27

The potential to harness the unique physical, chemical, and biological properties of the sundew (Drosera) plant's adhesive hydrogels has long intrigued researchers searching for novel wound-healing applications. However, the ability to collect sufficient quantities of the sundew plant's adhesive hydrogels is problematic and has eclipsed their therapeutic promise. Inspired by these natural hydrogels, we asked if sundew-inspired adhesive hydrogels could overcome the drawbacks associated with natural sundew hydrogels and be used in combination with stem-cell-based therapy to enhance wound-healing therapeutics. Using a bioinspired approach, we synthesized adhesive hydrogels comprised of sodium alginate, gum arabic, and calcium ions to mimic the properties of the natural sundew-derived adhesive hydrogels. We then characterized and showed that these sundew-inspired hydrogels promote wound healing through their superior adhesive strength, nanostructure, and resistance to shearing when compared to other hydrogels in vitro. In vivo, sundew-inspired hydrogels promoted a "suturing" effect to wound sites, which was demonstrated by enhanced wound closure following topical application of the hydrogels. In combination with mouse adipose-derived stem cells (ADSCs) and compared to other therapeutic biomaterials, the sundew-inspired hydrogels demonstrated superior wound-healing capabilities. Collectively, our studies show that sundew-inspired hydrogels contain ideal properties that promote wound healing and suggest that sundew-inspired-ADSCs combination therapy is an efficacious approach for treating wounds without eliciting noticeable toxicity or inflammation.

Multifunctionality of nanocrystalline lanthanum ferrite

NASA Astrophysics Data System (ADS)

Rai, Atma; Thakur, Awalendra K.

2016-05-01

Nanocrystalline lanthanum ferrite has been synthesized by adopting modified Pechini route. No evidence of impurity or secondary phase has been detected up to the detection of error limit of X-ray diffractometer (XRD). Rietveld refinement of X-ray diffraction pattern reveals orthorhombic crystal system with space group Pnma (62).Crystallite size and lattice strain was found to be ˜42.8nm and 0.306% respectively. Optical band gap was found to be 2.109 eV, by UV-Visible diffused reflectance spectrum (DRS). Brunauer-Emmet-Teller (BET) surface area was found to be ˜3.45 m2/g. Magnetization-hysteresis (M-H) loop was recorded at room temperature (300K) reveals weak ferromagnetism in Nanocrystalline lanthanum ferrite. The weak ferromagnetism in lanthanum ferrite is due to the uncompensated antiferromagnetic spin ordering. Ferroelectric loop hysteresis observed at room temperature at 100Hz depicts the presence of ferroelectric ordering in LaFeO3.Simultanious presence of magnetic and ferroelectric ordering at room temperature makes it suitable candidate of Multiferroic family.

Multifunctionality of nanocrystalline lanthanum ferrite

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

Rai, Atma, E-mail: atma@iitp.ac.in; Thakur, Awalendra K.; Centre for Energy and Environment, Indian Institute of Technology Patna 800013 India

2016-05-06

Nanocrystalline lanthanum ferrite has been synthesized by adopting modified Pechini route. No evidence of impurity or secondary phase has been detected up to the detection of error limit of X-ray diffractometer (XRD). Rietveld refinement of X-ray diffraction pattern reveals orthorhombic crystal system with space group Pnma (62).Crystallite size and lattice strain was found to be ∼42.8nm and 0.306% respectively. Optical band gap was found to be 2.109 eV, by UV-Visible diffused reflectance spectrum (DRS). Brunauer-Emmet-Teller (BET) surface area was found to be ∼3.45 m{sup 2}/g. Magnetization-hysteresis (M-H) loop was recorded at room temperature (300K) reveals weak ferromagnetism in Nanocrystalline lanthanummore » ferrite. The weak ferromagnetism in lanthanum ferrite is due to the uncompensated antiferromagnetic spin ordering. Ferroelectric loop hysteresis observed at room temperature at 100Hz depicts the presence of ferroelectric ordering in LaFeO{sub 3}.Simultanious presence of magnetic and ferroelectric ordering at room temperature makes it suitable candidate of Multiferroic family.« less

The epidemiology of microbial keratitis with silicone hydrogel contact lenses.

PubMed

Stapleton, Fiona; Keay, Lisa; Edwards, Katie; Holden, Brien

2013-01-01

It was widely anticipated that after the introduction of silicone hydrogel lenses, the risk of microbial keratitis would be lower than with hydrogel lenses because of the reduction in hypoxic effects on the corneal epithelium. Large-scale epidemiological studies have confirmed that the absolute and relative risk of microbial keratitis is unchanged with overnight use of silicone hydrogel materials. The key findings include the following: (1) The risk of infection with 30 nights of silicone hydrogel use is equivalent to 6 nights of hydrogel extended wear; (2) Occasional overnight lens use is associated with a greater risk than daily lens use; (3) The rate of vision loss due to corneal infection with silicone hydrogel contact lenses is similar to that seen in hydrogel lenses; (4) The spectrum of causative organisms is similar to that seen in hydrogel lenses, and the material type does not impact the corneal location of presumed microbial keratitis; and (5) Modifiable risk factors for infection include overnight lens use, the degree of exposure, failing to wash hands before lens handling, and storage case hygiene practice. The lack of change in the absolute risk of disease would suggest that exposure to large number of pathogenic organisms can overcome any advantages obtained from eliminating the hypoxic effects of contact lenses. Epidemiological studies remain important in the assessment of new materials and modalities. Consideration of an early adopter effect with studies involving new materials and modalities and further investigation of the impact of second-generation silicone hydrogel materials is warranted.

Electroactive SWNT/PEGDA hybrid hydrogel coating for bio-electrode interface.

PubMed

He, Lei; Lin, Demeng; Wang, Yanping; Xiao, Yinghong; Che, Jianfei

2011-10-15

Electric interface between neural tissue and electrode plays a significant role in the development of implanted devices for continuous monitoring and functional stimulation of central nervous system in terms of electroactivity, biocompatibility and long-term stability. To engineer an interface that possesses these merits, a polymeric hydrogel based on poly(ethylene glycol) diacrylate (PEGDA) and single-walled carbon nanotubes (SWNTs) were employed to fabricate a hybrid hydrogel via covalent anchoring strategy, i.e., self-assembly of cysteamine (Cys) followed by Michael addition between Cys and PEGDA. XPS characterization proves that the Cys molecules are linked to gold surface via the strong S-Au bond and that the PEGDA macromers are covalently bonded to Cys. FTIR spectra indicate the formation of hybrid hydrogel coating during photopolymerization. Electrochemical measurements using cyclic voltammetry (CV) and impedance spectrum clearly show the enhancement of electric properties to the hydrogel by the SWNTs. The charge transfer of the hybrid hydrogel-based electrode is quasi-reversible and charge transfer resistance decreases to the tenth of that of the pure hydrogel due to electron hopping along the SWNTs. Additionally, this hybrid hydrogel provides a favorable biomimetic microenvironment for cell attachment and growth due to its inherent biocompatibility. Combination of these merits yields hybrid hydrogels that can be good candidates for application to biosensors and biomedical devices. More importantly, the hybrid hydrogel coatings fabricated via the current strategy have good adhesion to the electrode substrate which is highly desired for chronically implantable devices. Copyright © 2011 Elsevier B.V. All rights reserved.

Carbon foam/hydroxyapatite coating for carbon/carbon composites: Microstructure and biocompatibility

NASA Astrophysics Data System (ADS)

Zhang, Leilei; Li, Hejun; Li, Kezhi; Zhang, Shouyang; Lu, Jinhua; Li, Wei; Cao, Sheng; Wang, Bin

2013-12-01

To improve the surface biocompatibility of carbon/carbon composites, a carbon foam/hydroxyapatite coating was applied using a combination method of slurry procedure and ultrasound-assisted electrochemical deposition procedure. The morphology, microstructure and chemical composition of the coating were investigated by scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy and X-ray diffraction. The biocompatibility of the carbon foam/hydroxyapatite coating was investigated by osteoblast-like MG63 cell culture tests. The results showed that the carbon foam could provide a large number of pores on the surface of carbon/carbon composites. The hydroxyapatite crystals could infiltrate into the pores and form the carbon foam/hydroxyapatite coating. The coating covered the carbon/carbon composites fully and uniformly with slice morphology. The cell response tests showed that the MG63 cells on carbon foam/hydroxyapatite coating had a better cell adhesion and cell proliferation than those on uncoated carbon/carbon composites. The carbon foam/hydroxyapatite coatings were cytocompatible and were beneficial to improve the biocompatibility. The approach presented here may be exploited for fabrication of carbon/carbon composite implant surfaces.

Cell-laden hydrogels for osteochondral and cartilage tissue engineering.

PubMed

Yang, Jingzhou; Zhang, Yu Shrike; Yue, Kan; Khademhosseini, Ali

2017-07-15

Despite tremendous advances in the field of regenerative medicine, it still remains challenging to repair the osteochondral interface and full-thickness articular cartilage defects. This inefficiency largely originates from the lack of appropriate tissue-engineered artificial matrices that can replace the damaged regions and promote tissue regeneration. Hydrogels are emerging as a promising class of biomaterials for both soft and hard tissue regeneration. Many critical properties of hydrogels, such as mechanical stiffness, elasticity, water content, bioactivity, and degradation, can be rationally designed and conveniently tuned by proper selection of the material and chemistry. Particularly, advances in the development of cell-laden hydrogels have opened up new possibilities for cell therapy. In this article, we describe the problems encountered in this field and review recent progress in designing cell-hydrogel hybrid constructs for promoting the reestablishment of osteochondral/cartilage tissues. Our focus centers on the effects of hydrogel type, cell type, and growth factor delivery on achieving efficient chondrogenesis and osteogenesis. We give our perspective on developing next-generation matrices with improved physical and biological properties for osteochondral/cartilage tissue engineering. We also highlight recent advances in biomanufacturing technologies (e.g. molding, bioprinting, and assembly) for fabrication of hydrogel-based osteochondral and cartilage constructs with complex compositions and microarchitectures to mimic their native counterparts. Despite tremendous advances in the field of regenerative medicine, it still remains challenging to repair the osteochondral interface and full-thickness articular cartilage defects. This inefficiency largely originates from the lack of appropriate tissue-engineered biomaterials that replace the damaged regions and promote tissue regeneration. Cell-laden hydrogel systems have emerged as a promising tissue

Suspension thermal spraying of hydroxyapatite: microstructure and in vitro behaviour.

PubMed

Bolelli, Giovanni; Bellucci, Devis; Cannillo, Valeria; Lusvarghi, Luca; Sola, Antonella; Stiegler, Nico; Müller, Philipp; Killinger, Andreas; Gadow, Rainer; Altomare, Lina; De Nardo, Luigi

2014-01-01

In cementless fixation of metallic prostheses, bony ingrowth onto the implant surface is often promoted by osteoconductive plasma-sprayed hydroxyapatite coatings. The present work explores the use of the innovative High Velocity Suspension Flame Spraying (HVSFS) process to coat Ti substrates with thin homogeneous hydroxyapatite coatings. The HVSFS hydroxyapatite coatings studied were dense, 27-37μm thick, with some transverse microcracks. Lamellae were sintered together and nearly unidentifiable, unlike conventional plasma-sprayed hydroxyapatite. Crystallinities of 10%-70% were obtained, depending on the deposition parameters and the use of a TiO2 bond coat. The average hardness of layers with low (<24%) and high (70%) crystallinity was ≈3.5GPa and ≈4.5GPa respectively. The distributions of hardness values, all characterised by Weibull modulus in the 5-7 range, were narrower than that of conventional plasma-sprayed hydroxyapatite, with a Weibull modulus of ≈3.3. During soaking in simulated body fluid, glassy coatings were progressively resorbed and replaced by a new, precipitated hydroxyapatite layer, whereas coatings with 70% crystallinity were stable up to 14days of immersion. The interpretation of the precipitation behaviour was also assisted by surface charge assessments, performed through Z-potential measurements. During in vitro tests, HA coatings showed no cytotoxicity towards the SAOS-2 osteoblast cell line, and surface cell proliferation was comparable with proliferation on reference polystyrene culture plates. © 2013.

Design of multimodal degradable hydrogels for controlled therapeutic delivery

NASA Astrophysics Data System (ADS)

Kharkar, Prathamesh Madhav

Hydrogels are of growing interest for the delivery of therapeutics to specific sites in the body. For localized drug delivery, hydrophilic polymeric precursors often are laden with bioactive moieties and then directly injected to the site of interest for in situ gel formation. The release of physically entrapped cargo is dictated by Fickian diffusion, degradation of the drug carrier, or a combination of both. The goal of this work was to design and characterize degradable hydrogel formulations that are responsive to multiple biologically relevant stimuli for degradation-mediated delivery of cargo molecules such as therapeutic proteins, growth factors, and immunomodulatory agents. We began by demonstrating the use of cleavable click linkages formed by Michael-type addition reactions in conjunction with hydrolytically cleavable functionalities for the degradation of injectable hydrogels by endogenous stimuli for controlled protein release. Specifically, the reaction between maleimides and thiols was utilized for hydrogel formation, where thiol selection dictates the degradability of the resulting linkage under thiol-rich reducing conditions. Relevant microenvironments where degradation would occur in vivo include those rich in glutathione (GSH), a tripeptide that is found at elevated concentrations in carcinoma tissues. Degradation of the hydrogels was monitored with rheometry and volumetric swelling measurements. Arylthiol-based thioether succinimide linkages underwent degradation via click cleavage and thiol exchange reaction in the presence of GSH and via ester hydrolysis, whereas alkylthiol-based thioether succinimide linkages only undergo degradation by only ester hydrolysis. The resulting control over the degradation rate within a reducing microenvironment resulted in 2.5 fold differences in the release profile of the model protein, a fluorescently-labeled bovine serum albumin, from dually degradable hydrogels compared to non-degradable hydrogels, where the

Structure of Biocompatible Coatings Produced from Hydroxyapatite Nanoparticles by Detonation Spraying

NASA Astrophysics Data System (ADS)

Nosenko, Valentyna; Strutynska, Nataliia; Vorona, Igor; Zatovsky, Igor; Dzhagan, Volodymyr; Lemishko, Sergiy; Epple, Matthias; Prymak, Oleg; Baran, Nikolai; Ishchenko, Stanislav; Slobodyanik, Nikolai; Prylutskyy, Yuriy; Klyui, Nickolai; Temchenko, Volodymyr

2015-12-01

Detonation-produced hydroxyapatite coatings were studied by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), Raman spectroscopy, and electron paramagnetic resonance (EPR) spectroscopy. The source material for detonation spraying was a B-type carbonated hydroxyapatite powder. The coatings consisted of tetracalcium phosphate and apatite. The ratio depended slightly on the degree of crystallinity of the initial powder and processing parameters of the coating preparation. The tetracalcium phosphate phase was homogeneous; the apatite phase contained defects localized on the sixfold axis and consisted of hydroxyapatite and oxyapatite. Technological factors contributing to the transformation of hydroxyapatite powder structure during coating formation by detonation spraying are discussed.

Structure of Biocompatible Coatings Produced from Hydroxyapatite Nanoparticles by Detonation Spraying.

PubMed

Nosenko, Valentyna; Strutynska, Nataliia; Vorona, Igor; Zatovsky, Igor; Dzhagan, Volodymyr; Lemishko, Sergiy; Epple, Matthias; Prymak, Oleg; Baran, Nikolai; Ishchenko, Stanislav; Slobodyanik, Nikolai; Prylutskyy, Yuriy; Klyui, Nickolai; Temchenko, Volodymyr

2015-12-01

Detonation-produced hydroxyapatite coatings were studied by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), Raman spectroscopy, and electron paramagnetic resonance (EPR) spectroscopy. The source material for detonation spraying was a B-type carbonated hydroxyapatite powder. The coatings consisted of tetracalcium phosphate and apatite. The ratio depended slightly on the degree of crystallinity of the initial powder and processing parameters of the coating preparation. The tetracalcium phosphate phase was homogeneous; the apatite phase contained defects localized on the sixfold axis and consisted of hydroxyapatite and oxyapatite. Technological factors contributing to the transformation of hydroxyapatite powder structure during coating formation by detonation spraying are discussed.

On the assessment of hydroxyapatite fluoridation by means of Raman scattering

NASA Astrophysics Data System (ADS)

Campillo, M.; Lacharmoise, P. D.; Reparaz, J. S.; Goñi, A. R.; Valiente, M.

2010-06-01

Hydroxyapatite is the main mineral component of bones and teeth. Fluorapatite, a bioceramic that can be obtained from hydroxyapatite by chemical substitution of the hydroxide ions with fluoride, exhibits lower mineral solubility and larger mechanical strength. Despite the widespread use of fluoride against caries, a reliable technique for unambiguous assessment of fluoridation in in vitro tests is still lacking. Here we present a method to probe fluorapatite formation in fluoridated hydroxyapatite by combining Raman scattering with thermal annealing. In synthetic minerals, we found that effectively fluoride substituted hydroxyapatite transforms into fluorapatite only after heat treatment, due to the high activation energy for this first order phase transition.

Sintering Effects on Morphology, Thermal Stability and Surface Area of Sol-Gel Derived Nano-Hydroxyapatite Powder

NASA Astrophysics Data System (ADS)

Kapoor, Seema; Batra, Uma; Kohli, Suchita

2011-12-01

Hydroxyapatite (HAP) ceramics have been recognized as substitute materials for bone and teeth in orthopedic and dentistry field due to their chemical and biological similarity to human hard tissue. The nanosized and nanocrystalline forms of HAP have great potential to revolutionize the hard tissue-engineering field, starting from bone repair and augmentation to controlled drug delivery systems. This paper reports the synthesis of biomimetic nano-hydroxyapatite (HAP) by sol-gel method using calcium nitrate tetrahydrate (CNT) and potassium dihydrogen phosphate (KDP) as calcium and phosphorus precursors, respectively to obtain a desired Ca/P ratio of 1.67. Deionized water was used as a diluting media for HAP sol preparation and ammonia was used to adjust the pH to 11. After aging, the HAP gel was dried at 55 °C and sintered to different temperatures (200 °C, 400 °C, 600 °C, 800 °C, 1000 °C and 1200 °C). The dried and sintered powders were characterized for phase composition using Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). The particle size and morphology was studied using transmission electron microscopy (TEM). The thermal behavior of the dried HAP nanopowder was studied in the temperature range of 55 °C to 1000 °C using thermal gravimetric analyser (TGA). The BET surface area of absorbance was determined by Nitrogen adsorption using Brunauer-Emmett-Teller (BET) method. The presence of characteristic peaks of the phosphate and OH groups in FTIR spectrums confirmed the formation of pure HAP in dried as well as sintered powders. XRD results also confirmed the formation of stoichiometric nano-HAP. Sintering revealed that with increase in temperature, both the crystallinity and crystallite size of nano-HAP particles increased. The synthesized nano-HAP powder was found to be stable upto 1000 °C without any additional phase other than HAP, whereas peak of β-TCP (tricalcium phosphate) was observed at 1200 °C. Photomicrograph of

Hydrogels Derived from Central Nervous System Extracellular Matrix

PubMed Central

Medberry, Christopher J.; Crapo, Peter M.; Siu, Bernard F.; Carruthers, Christopher A.; Wolf, Matthew T.; Nagarkar, Shailesh P.; Agrawal, Vineet; Jones, Kristen E.; Kelly, Jeremy; Johnson, Scott A.; Velankar, Sachin S.; Watkins, Simon C.; Modo, Michel

2012-01-01

Biologic scaffolds composed of extracellular matrix (ECM) are commonly used repair devices in preclinical and clinical settings; however the use of these scaffolds for peripheral and central nervous system (CNS) repair has been limited. Biologic scaffolds developed from brain and spinal cord tissue have recently been described, yet the conformation of the harvested ECM limits therapeutic utility. An injectable CNS-ECM derived hydrogel capable of in vivo polymerization and conformation to irregular lesion geometries may aid in tissue reconstruction efforts following complex neurologic trauma. The objectives of the present study were to develop hydrogel forms of brain and spinal cord ECM and compare the resulting biochemical composition, mechanical properties, and neurotrophic potential of a brain derived cell line to a non-CNS-ECM hydrogel, urinary bladder matrix. Results showed distinct differences between compositions of brain ECM, spinal cord ECM, and urinary bladder matrix. The rheologic modulus of spinal cord ECM hydrogel was greater than that of brain ECM and urinary bladder matrix. All ECMs increased the number of cells expressing neurites, but only brain ECM increased neurite length, suggesting a possible tissue-specific effect. All hydrogels promoted three-dimensional uni- or bi-polar neurite outgrowth following 7 days in culture. These results suggest that CNS-ECM hydrogels may provide supportive scaffolding to promote in vivo axonal repair. PMID:23158935

Capillary Origami Inspired Fabrication of Complex 3D Hydrogel Constructs.

PubMed

Li, Moxiao; Yang, Qingzhen; Liu, Hao; Qiu, Mushu; Lu, Tian Jian; Xu, Feng

2016-09-01

Hydrogels have found broad applications in various engineering and biomedical fields, where the shape and size of hydrogels can profoundly influence their functions. Although numerous methods have been developed to tailor 3D hydrogel structures, it is still challenging to fabricate complex 3D hydrogel constructs. Inspired by the capillary origami phenomenon where surface tension of a droplet on an elastic membrane can induce spontaneous folding of the membrane into 3D structures along with droplet evaporation, a facile strategy is established for the fabrication of complex 3D hydrogel constructs with programmable shapes and sizes by crosslinking hydrogels during the folding process. A mathematical model is further proposed to predict the temporal structure evolution of the folded 3D hydrogel constructs. Using this model, precise control is achieved over the 3D shapes (e.g., pyramid, pentahedron, and cube) and sizes (ranging from hundreds of micrometers to millimeters) through tuning membrane shape, dimensionless parameter of the process (elastocapillary number Ce ), and evaporation time. This work would be favorable to multiple areas, such as flexible electronics, tissue regeneration, and drug delivery. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Preparation and antibacterial properties of O-carboxymethyl chitosan/lincomycin hydrogels.

PubMed

He, Guanghua; Chen, Xiang; Yin, Yihua; Cai, Weiquan; Ke, Wanwan; Kong, Yahui; Zheng, Hua

2016-01-01

In this study, O-carboxymethyl chitosan (O-CMCS) was synthesized from chitosan and monochloroacetic acid. Then O-CMCS hydrogel was prepared by 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) in which the lincomycin was packaged. The Fourier transform infrared spectrum and scanning electron microscopy were adopted to characterize the structure and morphology of the product. The influences of dosage of EDC/NHS and concentration of O-CMCS on the swelling properties of the hydrogels were investigated. The hydrogels performed good swelling capacities and obvious pH-sensitive properties. The antibacterial activities of the hydrogels were tested against Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus). Compared with pure O-CMCS hydrogels, the antibacterial activities of O-CMCS/lincomycin hydrogels were significantly improved with the increase in the concentration of lincomycin against E. coli and S. aureus. With the increase in dosage of crosslinking agent or concentration of O-CMCS, the antibacterial activities both decreased gradually against the two bacteria. O-CMCS/lincomycin hydrogel was expected to be used for antibacterial material in view of its significant antibacterial activities.

Hydrogels That Allow and Facilitate Bone Repair, Remodeling, and Regeneration

PubMed Central

Short, Aaron R.; Koralla, Deepthi; Deshmukh, Ameya; Wissel, Benjamin; Stocker, Benjamin; Calhoun, Mark; Dean, David; Winter, Jessica O.

2015-01-01

Bone defects can originate from a variety of causes, including trauma, cancer, congenital deformity, and surgical reconstruction. Success of the current “gold standard” treatment (i.e., autologous bone grafts) is greatly influenced by insufficient or inappropriate bone stock. There is thus a critical need for the development of new, engineered materials for bone repair. This review describes the use of natural and synthetic hydrogels as scaffolds for bone tissue engineering. We discuss many of the advantages that hydrogels offer as bone repair materials, including their potential for osteoconductivity, biodegradability, controlled growth factor release, and cell encapsulation. We also discuss the use of hydrogels in composite devices with metals, ceramics, or polymers. These composites are useful because of the low mechanical moduli of hydrogels. Finally, the potential for thermosetting and photo-cross-linked hydrogels as three-dimensionally (3D) printed, patient-specific devices is highlighted. Three-dimensional printing enables controlled spatial distribution of scaffold materials, cells, and growth factors. Hydrogels, especially natural hydrogels present in bone matrix, have great potential to augment existing bone tissue engineering devices for the treatment of critical size bone defects. PMID:26693013

Cyclodextrin modified hydrogels of PVP/PEG for sustained drug release.

PubMed

Nielsen, Anne Louise; Madsen, Flemming; Larsen, Kim Lambertsen

2009-02-01

Hydrogels are water swollen networks of polymers and especially hydrogels consisting of poly vinylpyrrolidone/poly ethyleneglycol-dimethacrylate (PVP/PEG-DMA) blends show promising wound care properties. Enhanced functionality of the hydrogels can be achieved by incorporating drugs and other substances that may assist wound healing into the gel matrix. Controlling the release of active compounds from the hydrogels may be possible by carefully modifying the polymer matrix. For this purpose, cyclodextrins (CD) were grafted to the polymer matrix in 4-5 w/w% in an attempt to retard the release of water-soluble drugs. Ibuprofenate (IBU) was chosen as model drug and loaded in IBU/CD ratios of 0.6, 1.2, and 2.5. Vinyl derivatives of alpha-, beta- and gamma-CD were produced, added to the prepolymer blend and cured by UV-light. During this curing process the CD derivatives were covalently incorporated into the hydrogel matrix. The modified hydrogels were loaded with ibuprofenate by swelling. The release of the model drug from CD modified hydrogels show that especially covalently bonded beta-cyclodextrin can change both the release rate and the release profile of ibuprofen.

Hydrogels That Allow and Facilitate Bone Repair, Remodeling, and Regeneration.

PubMed

Short, Aaron R; Koralla, Deepthi; Deshmukh, Ameya; Wissel, Benjamin; Stocker, Benjamin; Calhoun, Mark; Dean, David; Winter, Jessica O

2015-10-28

Bone defects can originate from a variety of causes, including trauma, cancer, congenital deformity, and surgical reconstruction. Success of the current "gold standard" treatment (i.e., autologous bone grafts) is greatly influenced by insufficient or inappropriate bone stock. There is thus a critical need for the development of new, engineered materials for bone repair. This review describes the use of natural and synthetic hydrogels as scaffolds for bone tissue engineering. We discuss many of the advantages that hydrogels offer as bone repair materials, including their potential for osteoconductivity, biodegradability, controlled growth factor release, and cell encapsulation. We also discuss the use of hydrogels in composite devices with metals, ceramics, or polymers. These composites are useful because of the low mechanical moduli of hydrogels. Finally, the potential for thermosetting and photo-cross-linked hydrogels as three-dimensionally (3D) printed, patient-specific devices is highlighted. Three-dimensional printing enables controlled spatial distribution of scaffold materials, cells, and growth factors. Hydrogels, especially natural hydrogels present in bone matrix, have great potential to augment existing bone tissue engineering devices for the treatment of critical size bone defects.

Hydraulic hydrogel actuators and robots optically and sonically camouflaged in water

PubMed Central

Yuk, Hyunwoo; Lin, Shaoting; Ma, Chu; Takaffoli, Mahdi; Fang, Nicolas X.; Zhao, Xuanhe

2017-01-01

Sea animals such as leptocephali develop tissues and organs composed of active transparent hydrogels to achieve agile motions and natural camouflage in water. Hydrogel-based actuators that can imitate the capabilities of leptocephali will enable new applications in diverse fields. However, existing hydrogel actuators, mostly osmotic-driven, are intrinsically low-speed and/or low-force; and their camouflage capabilities have not been explored. Here we show that hydraulic actuations of hydrogels with designed structures and properties can give soft actuators and robots that are high-speed, high-force, and optically and sonically camouflaged in water. The hydrogel actuators and robots can maintain their robustness and functionality over multiple cycles of actuations, owing to the anti-fatigue property of the hydrogel under moderate stresses. We further demonstrate that the agile and transparent hydrogel actuators and robots perform extraordinary functions including swimming, kicking rubber-balls and even catching a live fish in water. PMID:28145412

Characteristics of Sodium Polyacrylate/Nano-Sized Carbon Hydrogel for Biomedical Patch.

PubMed

Park, Jong-Kyu; Seo, Sun-Kyo; Cho, Seungkwan; Kim, Han-Sung; Lee, Chi-Hwan

2018-03-01

Conductive hydrogels were prepared for biomedical patch in order to improve the electrical conductivity. Sodium polyacrylate and nano-sized carbon were mixed and fabricated by aqueous solution gelation process in various contents of nano-sized carbon with 0.1, 0.5, 1.0 and 2.0 wt%. Sodium polyacrylate/nano-sized carbon conductive hydrogels were investigated by molecular structure, surface morphology and electrical conductivity. The conductivity of the hydrogel/nano-sized carbon conductive hydrogel proved to be 10% higher than conductive hydrogel without nano-sized carbon. However, it was founded that conductive hydrogels with nano-sized carbon content from 0.5 up to 2.0 wt% were remarkably decreased. This may be due to the non-uniform distribution of nano-sized carbon, resulting from agglomerates of nano-sized carbon. The developed hydrogel is intended for use in the medical and cosmetic fields that is applicable to supply micro-current from device to human body.

Viscoelastic and fractal characteristics of a supramolecular hydrogel hybridized with clay nanoparticles.

PubMed

Song, Fei; Zhang, Li-Ming; Shi, Jun-Feng; Li, Nan-Nan

2010-12-01

The supramolecular hydrogels derived from low-molecular-mass gelators represent a unique class of soft matters and have important potential applications in biomedical fields, separation technology and cosmetic science. However, they suffer usually from weak mechanical and viscoelastic properties. In this work, we carry out the in situ hybridization of clay nanoparticles (Laponite RD) into the supramolecular hydrogel formed from a low-molecular-mass hydrogelator, 2,6-di[N-(carboxyethyl carbonyl)amino]pyridine (DAP), and investigate the viscoelastic and structural characteristics of resultant hybrid hydrogel. It was found that a small concentration of Laponite RD could lead to a significant increase in the storage modulus, loss modulus or complex viscosity. Compared with neat DAP hydrogel, the hybrid hydrogel has a greater hydrogel strength and a lower relaxation exponent. In particular, the enhancement of the clay nanoparticles to the viscoelastic properties of the DAP hydrogel is more effective in the case of higher DAP concentration. By relating its macroscopic elastic properties to a scaling fractal model, such a hybrid hydrogel was confirmed to be in the strong-link regime and to have a more complex network structure with a higher fractal dimension when compared with neat DAP hydrogel. Copyright © 2010 Elsevier B.V. All rights reserved.

Hydrogel formulation determines cell fate of fetal and adult neural progenitor cells

PubMed Central

Wagner, Jennifer L.; Shandas, Robin; Bjugstad, Kimberly B.

2014-01-01

Hydrogels provide a unique tool for neural tissue engineering. These materials can be customized for certain functions, i.e. to provide cell/drug delivery or act as a physical scaffold. Unfortunately, hydrogel complexities can negatively impact their biocompatibility, resulting in unintended consequences. These adverse effects may be combated with a better understanding of hydrogel chemical, physical, and mechanical properties, and how these properties affect encapsulated neural cells. We defined the polymerization and degradation rates and compressive moduli of 25 hydrogels formulated from different concentrations of hyaluronic acid (HA) and poly(ethylene glycol) (PEG). Changes in compressive modulus were driven primarily by the HA concentration. The in vitro biocompatibility of fetal-derived (fNPC) and adult-derived (aNPC) neural progenitor cells was dependent on hydrogel formulation. Acute survival of fNPC benefited from hydrogel encapsulation. NPC differentiation was divergent: fNPC differentiated into mostly glial cells, compared with neuronal differentiation of aNPC. Differentiation was influenced in part by the hydrogel mechanical properties. This study indicates that there can be a wide range of HA and PEG hydrogels compatible with NPC. Additionally, this is the first study comparing hydrogel encapsulation of NPC derived from different aged sources, with data suggesting that fNPC and aNPC respond dissimilarly within the same hydrogel formulation. PMID:24141109

Three-Dimensional Bioprinting of Oppositely Charged Hydrogels with Super Strong Interface Bonding.

PubMed

Li, Huijun; Tan, Yu Jun; Liu, Sijun; Li, Lin

2018-04-04

A novel strategy to improve the adhesion between printed layers of three-dimensional (3D) printed constructs is developed by exploiting the interaction between two oppositely charged hydrogels. Three anionic hydrogels [alginate, xanthan, and κ-carrageenan (Kca)] and three cationic hydrogels [chitosan, gelatin, and gelatin methacrylate (GelMA)] are chosen to find the optimal combination of two oppositely charged hydrogels for the best 3D printability with strong interface bonding. Rheological properties and printability of the hydrogels, as well as structural integrity of printed constructs in cell culture medium, are studied as functions of polymer concentration and the combination of hydrogels. Kca2 (2 wt % Kca hydrogel) and GelMA10 (10 wt % GelMA hydrogel) are found to be the best combination of oppositely charged hydrogels for 3D printing. The interfacial bonding between a Kca layer and a GelMA layer is proven to be significantly higher than that of the bilayered Kca or bilayered GelMA because of the formation of polyelectrolyte complexes between the oppositely charged hydrogels. A good cell viability of >96% is obtained for the 3D-bioprinted Kca-GelMA construct. This novel strategy has a great potential for 3D bioprinting of layered constructs with a strong interface bonding.

High frequency poroelastic waves in hydrogels.

PubMed

Chiarelli, Piero; Lanatà, Antonio; Carbone, Marina; Domenici, Claudio

2010-03-01

In this work a continuum model for high frequency poroelastic longitudinal waves in hydrogels is presented. A viscoelastic force describing the interaction between the polymer network and the bounded water present in such materials is introduced. The model is tested by means of ultrasound wave speed and attenuation measurements in polyvinylalcohol hydrogel samples. The theory and experiments show that ultrasound attenuation decreases linearly with the increase in the water volume fraction beta of the hydrogel. The introduction of the viscoelastic force between the bounded water and the polymer network leads to a bi-phasic theory, showing an ultrasonic fast wave attenuation that can vary as a function of the frequency with a non-integer exponent in agreement with the experimental data in literature. When beta tends to 1 (100% of interstitial water) due to the presence of bounded water in the hydrogel, the ultrasound phase velocity acquires higher value than that of pure water. The ultrasound speed gap at beta=1 is confirmed by the experimental results, showing that it increases in less cross-linked gel samples which own a higher concentration of bounded water.

Fitting the post-keratoplasty cornea with hydrogel lenses.

PubMed

Katsoulos, Costas; Nick, Vasileiou; Lefteris, Karageorgiadis; Theodore, Mousafeiropoulos

2009-02-01

We report two cases who have undergone penetrating keratoplasty (three eyes total), and who were fitted with hydrogel lenses. In the first case, a 28-year-old male presented with an interest in contact lens fitting. He had undergone corneal transplantation in both eyes, about 5 years ago. After topographies and trial fitting were performed, it was decided to be fitted with reverse geometry hydrogel lenses, due to the globular geometry of the cornea, the resultant instability of RGPs, and personal preference. In the second case, a 26-year-old female who had also penetrating keratoplasty was fitted with a hydrogel toric lens of high cylinder in the right eye. The final hydrogel lenses for the first subject incorporated a custom tricurve design, in which the second curve was steeper than the base curve and the third curve flatter than the second but still steeper than the first. Visual acuity was 6/7.5 RE and a mediocre 6/15 LE (OU 6/7.5). The second subject achieved 6/4.5 acuity RE with the high cylinder hydrogel toric lens. In corneas exhibiting extreme protrusion, such as keratoglobus and some cases after penetrating keratoplasty, curvatures are so extreme and the cornea so globular leading to specific fitting options: sclerals, small diameter RGPs and reverse geometry hydrogel lenses, in order to improve lens and optical stability. In selected cases such as the above, large diameter inverse geometry RGP may be fitted only if the eyelid shape and tension permits so. The first case demonstrates that the option of hydrogel lenses is viable when the patient has no interest in RGPs and in certain cases can improve vision to satisfactory levels. In other cases, graft toricity might be so high that the practitioner will need to employ hydrogel torics with large amounts of cylinder in order to correct vision. In such cases, the patient should be closely monitored in order to avoid complications from hypoxia.