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Sample records for based crosslinked deoxyribonucleic

  1. Adansonian Analysis and Deoxyribonucleic Acid Base Composition of Serratia marcescens

    PubMed Central

    Colwell, R. R.; Mandel, M.

    1965-01-01

    Colwell, R. R. (Georgetown University, Washington, D.C.), and M. Mandel. Adansonian analysis and deoxyribonucleic acid base composition of Serratia marcescens. J. Bacteriol. 89:454–461. 1965.—A total of 33 strains of Serratia marcescens were subjected to Adansonian analysis for which more than 200 coded features for each of the organisms were included. In addition, the base composition [expressed as moles per cent guanine + cytosine (G + C)] of the deoxyribonucleic acid (DNA) prepared from each of the strains was determined. Except for four strains which were intermediate between Serratia and the Hafnia and Aerobacter group C of Edwards and Ewing, the S. marcescens species group proved to be extremely homogeneous, and the different strains showed high affinities for each other (mean similarity, ¯S = 77%). The G + C ratio of the DNA from the Serratia strains ranged from 56.2 to 58.4% G + C. Many species names have been listed for the genus, but only a single clustering of the strains was obtained at the species level, for which the species name S. marcescens was retained. S. kiliensis, S. indica, S. plymuthica, and S. marinorubra could not be distinguished from S. marcescens; it was concluded, therefore, that there is only a single species in the genus. The variety designation kiliensis does not appear to be valid, since no subspecies clustering of strains with negative Voges-Proskauer reactions could be detected. The characteristics of the species are listed, and a description of S. marcescens is presented. PMID:14255714

  2. Latest advances in biomaterials: from deoxyribonucleic acid to nucleobases

    NASA Astrophysics Data System (ADS)

    Ouchen, Fahima; Gomez, Eliot; Joyce, Donna; Williams, Adrienne; Kim, Steve; Heckman, Emily; Johnson, Lewis; Yaney, Perry; Venkat, Narayanan; Steckl, Andrew; Kajzar, François; Rau, Ileana; Pawlicka, Agnieszka; Prasad, Paras; Grote, James

    2014-03-01

    This paper is a review of the recent research in bio-based materials for photonics and electronics applications. Materials that we have been working with include: deoxyribonucleic acid (DNA)-based biopolymers and nucleobases. We will highlight work on increasing the ionic conductivity of DNA-based membranes, enhancing the direct (DC) current and photoconductivity of DNA-based biopolymers, crosslinking of DNA-based biopolymers and promising applications for DNA nucleobases. Key

  3. A novel chaotic based image encryption using a hybrid model of deoxyribonucleic acid and cellular automata

    NASA Astrophysics Data System (ADS)

    Enayatifar, Rasul; Sadaei, Hossein Javedani; Abdullah, Abdul Hanan; Lee, Malrey; Isnin, Ismail Fauzi

    2015-08-01

    Currently, there are many studies have conducted on developing security of the digital image in order to protect such data while they are sending on the internet. This work aims to propose a new approach based on a hybrid model of the Tinkerbell chaotic map, deoxyribonucleic acid (DNA) and cellular automata (CA). DNA rules, DNA sequence XOR operator and CA rules are used simultaneously to encrypt the plain-image pixels. To determine rule number in DNA sequence and also CA, a 2-dimension Tinkerbell chaotic map is employed. Experimental results and computer simulations, both confirm that the proposed scheme not only demonstrates outstanding encryption, but also resists various typical attacks.

  4. ADANSONIAN ANALYSIS AND DEOXYRIBONUCLEIC ACID BASE COMPOSITION OF SOME GRAM-NEGATIVE BACTERIA

    PubMed Central

    Colwell, R. R.; Mandel, M.

    1964-01-01

    Colwell, R. R. (Georgetown University, Washington, D.C.), and M. Mandel. Adansonian analysis and deoxyribonucleic acid base composition of some gram-negative bacteria. J. Bacteriol. 87:1412–1422. 1964.—The deoxyribonucleic acid (DNA) base compositions and S values for a minimum of 134 coded properties were determined for representative cultures of the genera Pseudomonas, Xanthomonas, Aeromonas, Vibrio, Aerobacter, Escherichia, Alcaligenes, and Flavobacterium. Those cultures having a high degree of similarity by the criterion of numerical taxonomy were found to have similar DNA base compositions. The relative affinities of clusters of cultures suggest taxonomic relations. Eleven species of Xanthomonas might be a single species, and V. metschnikovii was shown to be more closely related to enteric bacteria than to other vibrios which, in turn, were found to be like pseudomonads. Aeromonas was found to be intermediate in similarity to enterics and pseudomonads and divisible into at least two, but possibly three, species. F. aquatile was unlike any of the other organisms studied, and its DNA also differed greatly in composition from other representatives of the genus. PMID:14188722

  5. Deoxyribonucleic acid-based hybrid thin films for potential application as high energy density capacitors

    NASA Astrophysics Data System (ADS)

    Joyce, Donna M.; Venkat, Narayanan; Ouchen, Fahima; Singh, Kristi M.; Smith, Steven R.; Grabowski, Christopher A.; Terry Murray, P.; Grote, James G.

    2014-03-01

    Deoxyribonucleic acid (DNA) based hybrid films incorporating sol-gel-derived ceramics have shown strong promise as insulating dielectrics for high voltage capacitor applications. Our studies of DNA-CTMA (cetyltrimethylammonium) complex/sol-gel ceramic hybrid thin film devices have demonstrated reproducibility and stability in temperature- and frequency-dependent dielectric properties with dielectric constant k ˜ 5.0 (1 kHz), as well as reliability in DC voltage breakdown measurements, attaining values consistently in the range of 300-350 V/μm. The electrical/dielectric characteristics of DNA-CTMA films with sol-gel-derived ceramics were examined to determine the critical energy storage parameters such as voltage breakdown and dielectric constant.

  6. Reexamination of the Association Between Melting Point, Buoyant Density, and Chemical Base Composition of Deoxyribonucleic Acid

    PubMed Central

    De Ley, J.

    1970-01-01

    The equations currently used for the calculation of the chemical base composition of deoxyribonucleic acid (DNA), expressed as moles per cent guanine plus cytosine (% GC), from either buoyant density (ρ) or midpoint of thermal denaturation (Tm) were recalculated by using only sets of data on DNA determined with the same strains. All available information from the literature was screened and supplemented by unpublished data. The results were calculated by regression and correlation analysis and treated statistically. From the data on 96 strains of bacteria, it was calculated that% GC = 2.44 (Tm – 69.4). Tm appears to be unaffected by the substitution of cytosine by hydroxymethylcytosine. This equation is also valid for nonbacterial DNA. From the data on 84 strains of bacteria, the relation% GC = 1038.47 (–1.6616) was calculated. The constants in this equation are slightly modified when data on nonbacterial DNA are included. Both correlations differ only slightly from those currently used, but now they lean on a statistically sound basis. As a control, the relation between ρ and Tm was calculated from data of 197 strains; it agrees excellently with the above two equations. PMID:5438045

  7. High mobility organic field-effect transistor based on water-soluble deoxyribonucleic acid via spray coating

    SciTech Connect

    Shi, Wei; Han, Shijiao; Huang, Wei; Yu, Junsheng

    2015-01-26

    High mobility organic field-effect transistors (OFETs) by inserting water-soluble deoxyribonucleic acid (DNA) buffer layer between electrodes and pentacene film through spray coating process were fabricated. Compared with the OFETs incorporated with DNA in the conventional organic solvents of ethanol and methanol: water mixture, the water-soluble DNA based OFET exhibited an over four folds enhancement of field-effect mobility from 0.035 to 0.153 cm{sup 2}/Vs. By characterizing the surface morphology and the crystalline structure of pentacene active layer through atomic force microscope and X-ray diffraction, it was found that the adoption of water solvent in DNA solution, which played a key role in enhancing the field-effect mobility, was ascribed to both the elimination of the irreversible organic solvent-induced bulk-like phase transition of pentacene film and the diminution of a majority of charge trapping at interfaces in OFETs.

  8. Plasmid-Controlled Variation in the Content of Methylated Bases in Bacteriophage Lambda Deoxyribonucleic Acid

    PubMed Central

    Hattman, Stanley

    1972-01-01

    The N6-methyladenine (MeAde) and 5-methylcytosine (MeC) contents in deoxyribonucleic acid (DNA) of bacteriophage lambda has been analyzed as a function of host specificity. The following facts have emerged: (i) lambda grown on strains harboring the P1 prophage contain ca. 70 more MeAde residues/DNA molecule than lambda grown either in the P1-sensitive parent, or in a P1 immune-defective lysogen which does not confer P1 modification; (ii) lambda grown on strains harboring the N-3 drug-resistance factor contain ca. 60 more MeC residues/DNA molecule than lambda grown on the parental strain lacking the factor; (iii) lambda grown in Escherichia coli B strains is devoid of MeC, whereas lambda grown in a B (N-3) host contains a high level of MeC; (iv) the MeAde content in lambda DNA is not affected by the N-3 factor. These results suggest that P1 controls an adenine-specific DNA methylase, and that the N-3 plasmid controls a cytosine-specific DNA methylase. The N-3 factor has been observed previously to direct cytosine-specific methylation of phage P22 DNA and E. coli B DNA in vivo; in vitro studies presented here demonstrate this activity. PMID:4561202

  9. To Cross-Link or Not to Cross-Link? Cross-Linking Associated Foreign Body Response of Collagen-Based Devices

    PubMed Central

    Delgado, Luis M.; Bayon, Yves; Pandit, Abhay

    2015-01-01

    Collagen-based devices, in various physical conformations, are extensively used for tissue engineering and regenerative medicine applications. Given that the natural cross-linking pathway of collagen does not occur in vitro, chemical, physical, and biological cross-linking methods have been assessed over the years to control mechanical stability, degradation rate, and immunogenicity of the device upon implantation. Although in vitro data demonstrate that mechanical properties and degradation rate can be accurately controlled as a function of the cross-linking method utilized, preclinical and clinical data indicate that cross-linking methods employed may have adverse effects on host response, especially when potent cross-linking methods are employed. Experimental data suggest that more suitable cross-linking methods should be developed to achieve a balance between stability and functional remodeling. PMID:25517923

  10. Cross-linked polyelectrolyte for direct methanol fuel cells applications based on a novel sulfonated cross-linker

    NASA Astrophysics Data System (ADS)

    Li, Mingyu; Zhang, Gang; Xu, Shuai; Zhao, Chengji; Han, Miaomiao; Zhang, Liyuan; Jiang, Hao; Liu, Zhongguo; Na, Hui

    2014-06-01

    A novel type of cross-linked proton exchange membrane of lower methanol permeation and high proton conductivity is prepared, based on a newly synthesized sulfonated cross-linker: carboxyl terminated benzimidazole trimer bearing sulfonic acid groups (s-BI). Compared to membranes cross-linked with non-sulfonated cross-linker (BI), SPEEK/s-BI-n membranes show higher IEC values and proton conductivities. Meanwhile, oxidative stability and mechanical property of SPEEK/s-BI-n membranes are obviously improved. Among SPEEK/s-BI-n membranes, SPEEK/s-BI-2 exhibits high proton conductivity, low swelling ratio (0.122 S cm-1 and 15.2% at 60 °C, respectively) and low methanol permeability coefficient. These results imply that the cross-linked membranes prepared with the newly sulfonated cross-linker are promising for the direct methanol fuel cells (DMFCs) application.

  11. Leishmania donovani complex (Kinetoplastida, Trypanosomatidae): comparison of deoxyribonucleic acid based techniques for typing of isolates from Ethiopia.

    PubMed

    Gadisa, E; Kuru, T; Genet, A; Engers, H; Aseffa, A; Gedamu, L

    2010-10-01

    In Ethiopia, visceral leishmaniasis (VL) is an increasing public health concern. Recently, a new outbreak of VL claimed the lives of hundreds of Ethiopians. Mapping its distribution and the identification of the causative Leishmania species is important for proper use of resources and for control planning. The choice of appropriate typing technique is the key for determining the infecting species. Here we compared three deoxyribonucleic acid (DNA) based markers. We used, for the first time, cpbE and cpbF (cpbE/F) PCR-RFLP and demonstrated that it clearly differentiates Leishmania donovani from Leishmania infantum. The cpbE/F PCR-RFLP gave identical banding pattern for all L. donovani strains irrespective of their geographic origin. With the K26 (primers) PCR-RFLP, the L. donovani strains gave a banding pattern different from L. infantum and showed variation with geographic origin. The Ethiopian isolates typed as L. donovani by the PCR-RFLP of the cpbE/F (gene) and K26 (primers) showed two types of patterns with the T2/B4 (primers) PCR-RFLP; one group with L. infantum-like and the other L. donovani-like pattern. Phylogenetic analysis using cpbE/F sequences showed variation with geographic origin of strains and the African strains of L. donovani are more distantly related to L. infantum. Moreover, the Ethiopian isolates were seen to be closely related to the Sudanese, Kenyan and Indian strains. Thus, we recommend the use of more than one marker to study the population genetics of L. donovani complex. PMID:20438727

  12. Reversible phospholipid nanogels for deoxyribonucleic acid fragment size determinations up to 1500 base pairs and integrated sample stacking.

    PubMed

    Durney, Brandon C; Bachert, Beth A; Sloane, Hillary S; Lukomski, Slawomir; Landers, James P; Holland, Lisa A

    2015-06-23

    Phospholipid additives are a cost-effective medium to separate deoxyribonucleic acid (DNA) fragments and possess a thermally-responsive viscosity. This provides a mechanism to easily create and replace a highly viscous nanogel in a narrow bore capillary with only a 10°C change in temperature. Preparations composed of dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC) self-assemble, forming structures such as nanodisks and wormlike micelles. Factors that influence the morphology of a particular DMPC-DHPC preparation include the concentration of lipid in solution, the temperature, and the ratio of DMPC and DHPC. It has previously been established that an aqueous solution containing 10% phospholipid with a ratio of [DMPC]/[DHPC]=2.5 separates DNA fragments with nearly single base resolution for DNA fragments up to 500 base pairs in length, but beyond this size the resolution decreases dramatically. A new DMPC-DHPC medium is developed to effectively separate and size DNA fragments up to 1500 base pairs by decreasing the total lipid concentration to 2.5%. A 2.5% phospholipid nanogel generates a resolution of 1% of the DNA fragment size up to 1500 base pairs. This increase in the upper size limit is accomplished using commercially available phospholipids at an even lower material cost than is achieved with the 10% preparation. The separation additive is used to evaluate size markers ranging between 200 and 1500 base pairs in order to distinguish invasive strains of Streptococcus pyogenes and Aspergillus species by harnessing differences in gene sequences of collagen-like proteins in these organisms. For the first time, a reversible stacking gel is integrated in a capillary sieving separation by utilizing the thermally-responsive viscosity of these self-assembled phospholipid preparations. A discontinuous matrix is created that is composed of a cartridge of highly viscous phospholipid assimilated into a separation matrix

  13. Electrophoresis-Enhanced Detection of Deoxyribonucleic Acids on a Membrane-Based Lateral Flow Strip Using Avian Influenza H5 Genetic Sequence as the Model

    PubMed Central

    Wu, Jui-Chuang; Chen, Chih-Hung; Fu, Ja-Wei; Yang, Huan-Ching

    2014-01-01

    This study reports a simple strategy to detect a deoxyribonucleic acid (DNA) on a membrane-based lateral flow (MBLF) strip without tedious gel preparation, gel electrophoresis, and EtBr-staining processes. The method also enhances the detection signal of the genetic sample. A direct electric field was applied over two ends of the MBLF strips to induce an electrophoresis of DNAs through the strips. The signal enhancement was demonstrated by the detection of the H5 subtype of avian influenza virus (H5 AIV). This approach showed an excellent selectivity of H5 AIV from other two control species, Arabidopsis thaliana and human PSMA5. It also showed an effective signal repeatability and sensitivity over a series of analyte concentrations. Its detection limit could be enhanced, from 40 ng to 0.1 ng by applying 12 V. The nano-gold particles for the color development were labeled on the capture antibody, and UV-VIS and TEM were used to check if the labeling was successful. This detection strategy could be further developed to apply on the detection of drug-allergic genes at clinics or detection of infectious substances at incident sites by a simple manipulation with an aid of a mini-PCR machine and auxiliary kits. PMID:24603637

  14. Deoxyribonucleic acid in Nitrobacter carboxysomes.

    PubMed Central

    Westphal, K; Bock, E; Cannon, G; Shively, J M

    1979-01-01

    Carboxysomes were isolated from Nitrobacter winogradskyi and Nitrobacter agilis. The icosahedral particles contained double-stranded deoxyribonucleic acid (DNA). In the presence of ethidium bromide and cesium chloride, the particle-bound DNA had a buoyant density of rho 25 = 1.701 g/cm3. Electron microscopy revealed the DNA to be a 14-micron circular molecule. Images PMID:227833

  15. TEMPO-oxidized nanocellulose participating as crosslinking aid for alginate-based sponges.

    PubMed

    Lin, Ning; Bruzzese, Cécile; Dufresne, Alain

    2012-09-26

    Crosslinked polysaccharide sponges have been prepared by freeze-drying of amorphous alginate-oxidized nanocellulose in the presence of a Ca(2+) ionic crosslinking agent. The new carboxyl groups on the surface of nanocellulose induced by the chemical oxidization provided the possibility of participating in the construction of an alginate-based sponge's structure and played a fundamental role in the structural and mechanical stability of ensuing sponges. Furthermore, enhanced mechanical strength induced by oxidized cellulose nanocrystals and the formation of a semi-interpenetrating polymer network from oxidized microfibrillated cellulose were reported. Together with the facile and ionic crosslinking process, the ultrahigh porosity, promising water absorption and retention, as well as the improved compression strength of the crosslinked sponges should significantly extend the use of this soft material in diverse practical applications. PMID:22950801

  16. Effects of crosslinking agent on lithographic performance of negative-tone resists based on poly(p-hydroxystyrene)

    NASA Astrophysics Data System (ADS)

    Lin, Qinghuang; Katnani, Ahmad D.; Willson, C. Grant

    1997-07-01

    The effects of crosslinking agent on the lithographic performance of negative-tone resists based on poly(p- hydroxystyrene) (PHOST) have been investigated. Two crosslinking agents were used in the model resist systems: tetramethoxymethyl glycouril and 2,6-bis(acetoxymethyl) p- cresol. The resist containing tetramethoxymethyl glycouril shows better lithographic performance than the one with 2,6- bis(acetoxymethyl) p-cresol including better resolution, higher sensitivity, larger dissolution contrast, and less resist loss in the exposed regions during development. To reveal the origin of the difference in the lithographic performance, 13C NMR, FT-IR and differential scanning calorimetry (DSC) were employed to elucidate the crosslinking mechanisms, thermally induced crosslinking, the resulting network structure, and the crosslinking kinetics of the PHOST reaction with the two crosslinking agents. 13C NMR studies of model compound reactions suggest that the crosslinking of PHOST by tetramethoxymethyl glycouril proceeds via O- alkylation of the phenolic ring in the polymer, whereas the crosslinking of PHOST by 2,6-bis(acetoxymethyl) p-cresol proceeds via C-alkylation at the ortho carbon position of the phenolic ring. FT-IR studies indicate that there exists significant thermally induced crosslinking in the resist using 2,6-bis(acetoxymethyl) p-cresol as the crosslinking agent, while there is no detectable thermal crosslinking in the resist with tetramethoxymethyl glycouril as the crosslinking agent. The FT-IR results also show that the extent of crosslinking depends heavily on the crosslinking agent loading and the processing conditions. The effects of crosslinking chemistry on the crosslinked network structure and the lithographic performance of the two resists are discussed.

  17. Novel negative resists using thermally stable crosslinkers based on phenolic compounds

    NASA Astrophysics Data System (ADS)

    Kajita, Toru; Kobayashi, Eiichi; Ota, Toshiyuki; Miura, Takao

    1993-09-01

    This is a preliminary report on a family of crosslinkers based on phenolic compounds for negative-working photoresists which are suitable for KrF excimer laser exposure using poly(hydroxystyrene) (PHS) as a base resin. The crosslinkers are benzylic derivatives having etherificated or esterificated phenolic hydroxyl group. Several effects upon the resist performances of chemically amplified (CA) resist systems comprising onium salt, PHS, and the crosslinkers are mainly discussed: i.e., sort of substituent, sort of mother molecular structure, sort of crosslinkable group, baking conditions, PHS's molecular weight, additives, and so on. The CA resist gives quarter-micron line and space pairs without swelling using a KrF excimer laser exposure. Moreover, in this report another effective method for inhibiting the swelling is proposed. Finally, a unique negative resist, which is not a CA resist, is also presented. It gives negative-tone images by thermal crosslinking reaction following photo- induced dissociation of the protective group of crosslinker.

  18. Effect of base-pair stability of nearest-neighbor nucleotides on the fidelity of deoxyribonucleic acid synthesis.

    PubMed

    Patten, J E; So, A G; Downey, K M

    1984-04-10

    The influence of the stability of base pairs formed by nearest-neighbor nucleotides on misincorporation frequency has been studied with the large fragment of DNA polymerase I, the alternating DNA copolymers, poly(dI-dC) and poly-(dG-dC), as template-primers, and dGTP, dITP, and dCTP as substrates. We have utilized the difference in thermodynamic stability between the doubly H-bonded I X C base pair and triply H-bonded G X C base pair to examine the effects of base-pair stability of both the "preceding" and the "following" nucleotides on the frequency of insertion of a mismatched nucleotide, as well as on its stable incorporation into polynucleotide. The present studies demonstrate that the stability of the base pairs formed by nearest-neighbor nucleotides affects the frequency of incorporation of noncomplementary nucleotides. Misincorporation frequency is increased when the nearest-neighbor nucleotides form more stable base pairs with the corresponding nucleotides in the template and is decreased when they form less stable base pairs. The stability of the base pair formed by a nucleotide either preceding (5' to) or following (3' to) a misincorporated nucleotide influences misincorporation frequency, but by different mechanisms. The stability of base pairs formed by preceding nucleotides affects the rate of insertion of mismatched nucleotide but does not protect the mismatched nucleotide from removal by the 3' to 5' exonuclease activity. In contrast, the stability of a base pair formed by a following nucleotide determines whether a misincorporated nucleotide is extended or excised by affecting the ability of the enzyme to edit errors of incorporation. PMID:6722115

  19. Immunomodulation with Self-Crosslinked Polyelectrolyte Multilayer-Based Coatings.

    PubMed

    Knopf-Marques, Helena; Singh, Sonali; Htwe, Su Su; Wolfova, Lucie; Buffa, Radovan; Bacharouche, Jalal; Francius, Grégory; Voegel, Jean-Claude; Schaaf, Pierre; Ghaemmaghami, Amir M; Vrana, Nihal Engin; Lavalle, Philippe

    2016-06-13

    This study aims to design an optimal polyelectrolyte multilayer film of poly-l-lysine (PLL) and hyaluronic acid (HA) as an anti-inflammatory cytokine release system in order to decrease the implant failure due to any immune reactions. The chemical modification of the HA with aldehyde moieties allows self-cross-linking of the film and an improvement in the mechanical properties of the film. The cross-linking of the film and the release of immunomodulatory cytokine (IL-4) stimulate the differentiation of primary human monocytes seeded on the films into pro-healing macrophages phenotype. This induces the production of anti-inflammatory cytokines (IL1-RA and CCL18) and the decrease of pro-inflammatory cytokines secreted (IL-12, TNF-α, and IL-1β). Moreover, we demonstrate that cross-linking PLL/HA film using HA-aldehyde is already effective by itself to limit inflammatory processes. Finally, this functionalized self-cross-linked PLL/HA-aldehyde films constitutes an innovative and efficient candidate for immunomodulation of any kind of implants of various architecture and properties. PMID:27183396

  20. Optimisation of UV irradiation as a binding site conserving method for crosslinking collagen-based scaffolds.

    PubMed

    Davidenko, Natalia; Bax, Daniel V; Schuster, Carlos F; Farndale, Richard W; Hamaia, Samir W; Best, Serena M; Cameron, Ruth E

    2016-01-01

    Short wavelength (λ = 254 nm) UV irradiation was evaluated over a range of intensities (0.06 to 0.96 J/cm(2)) as a means of cross-linking collagen- and gelatin-based scaffolds, to tailor their material characteristics whilst retaining biological functionality. Zero-link carbodiimide treatments are commonly applied to collagen-based materials, forming cross-links from carboxylate anions (for example the acidic E of GFOGER) that are an essential part of integrin binding sites on collagen. Cross-linking these amino acids therefore disrupts the bioactivity of collagen. In contrast, UV irradiation forms bonds from less important aromatic tyrosine and phenylalanine residues. We therefore hypothesised that UV cross-linking would not compromise collagen cell reactivity. Here, highly porous (~99 %) isotropic, collagen-based scaffolds were produced via ice-templating. A series of scaffolds (pore diameters ranging from 130-260 μm) with ascending stability in water was made from gelatin, two different sources of collagen I, or blends of these materials. Glucose, known to aid UV crosslinking of collagen, was added to some lower-stability formulations. These scaffolds were exposed to different doses of UV irradiation, and the scaffold morphology, dissolution stability in water, resistance to compression and cell reactivity was assessed. Stabilisation in aqueous media varied with both the nature of the collagen-based material employed and the UV intensity. Scaffolds made from the most stable materials showed the greatest stability after irradiation, although the levels of cross-linking in all cases were relatively low. Scaffolds made from pure collagen from the two different sources showed different optimum levels of irradiation, suggesting altered balance between stabilisation from cross-linking and destabilisation from denaturation. The introduction of glucose into the scaffold enhanced the efficacy of UV cross-linking. Finally, as hypothesized, cell attachment, spreading and

  1. Antifouling coatings based on covalently cross-linked agarose film via thermal azide-alkyne cycloaddition.

    PubMed

    Xu, Li Qun; Pranantyo, Dicky; Neoh, Koon-Gee; Kang, En-Tang; Teo, Serena Lay-Ming; Fu, Guo Dong

    2016-05-01

    Coatings based on thin films of agarose-poly(ethylene glycol) (Agr-PEG) cross-linked systems are developed as environmentally-friendly and fouling-resistant marine coatings. The Agr-PEG cross-linked systems were prepared via thermal azide-alkyne cycloaddition (AAC) using azido-functionalized Agr (AgrAz) and activated alkynyl-containing poly(2-propiolamidoethyl methacrylate-co-poly(ethylene glycol)methyl ether methacrylate) P(PEMA-co-PEGMEMA) random copolymers as the precursors. The Agr-PEG cross-linked systems were further deposited onto a SS surface, pre-functionalized with an alkynyl-containing biomimetic anchor, dopamine propiolamide, to form a thin film after thermal treatment. The thin film-coated SS surfaces can effectively reduce the adhesion of marine algae and the settlement of barnacle cyprids. Upon covalent cross-linking, the covalently cross-linked Agr-PEG films coated SS surfaces exhibit good stability in flowing artificial seawater, and enhanced resistance to the settlement of barnacle cyprids, in comparison to that of the surfaces coated with physically cross-linked AgrAz films. PMID:26836479

  2. Crosslinking of micropatterned collagen-based nerve guides to modulate the expected half-life.

    PubMed

    Salvatore, L; Madaghiele, M; Parisi, C; Gatti, F; Sannino, A

    2014-12-01

    The microstructural, mechanical, compositional, and degradative properties of a nerve conduit are known to strongly affect the regenerative process of the injured peripheral nerve. Starting from the fabrication of micropatterned collagen-based nerve guides, according to a spin-casting process reported in the literature, this study further investigates the possibility to modulate the degradation rate of the scaffolds over a wide time frame, in an attempt to match different rates of nerve regeneration that might be encountered in vivo. To this aim, three different crosslinking methods, that is, dehydrothermal (DHT), carbodiimide-based (EDAC), and glutaraldehyde-based (GTA) crosslinking, were selected. The elastically effective degree of crosslinking, attained by each method and evaluated according to the classical rubber elasticity theory, was found to significantly tune the in vitro half-life (t1/2 ) of the matrices, with an exponential dependence of the latter on the crosslink density. The high crosslinking efficacy of EDAC and GTA treatments, respectively threefold and fourfold when compared to the one attained by DHT, led to a sharp increase of the corresponding in vitro half-lives (ca., 10, 172, and 690 h, for DHT, EDAC, and GTA treated matrices, respectively). As shown by cell viability assays, the cytocompatibility of both DHT and EDAC treatments, as opposed to the toxicity of GTA, suggests that such methods are suitable to crosslink collagen-based scaffolds conceived for clinical use. In particular, nerve guides with expected high residence times in vivo might be produced by finely controlling the biocompatible reaction(s) adopted for crosslinking. PMID:24532089

  3. ROMP-based thermosetting polymers from modified castor oil with various cross-linking agents

    NASA Astrophysics Data System (ADS)

    Ding, Rui

    Polymers derived from bio-renewable resources are finding an increase in global demand. In addition, polymers with distinctive functionalities are required in certain advanced fields, such as aerospace and civil engineering. In an attempt to meet both these needs, the goal of this work aims to develop a range of bio-based thermosetting matrix polymers for potential applications in multifunctional composites. Ring-opening metathesis polymerization (ROMP), which recently has been explored as a powerful method in polymer chemistry, was employed as a unique pathway to polymerize agricultural oil-based reactants. Specifically, a novel norbornyl-functionalized castor oil alcohol (NCA) was investigated to polymerize different cross-linking agents using ROMP. The effects of incorporating dicyclopentadiene (DCPD) and a norbornene-based crosslinker (CL) were systematically evaluated with respect to curing behavior and thermal mechanical properties of the polymers. Isothermal differential scanning calorimetry (DSC) was used to investigate the conversion during cure. Dynamic DSC scans at multiple heating rates revealed conversion-dependent activation energy by Ozawa-Flynn-Wall analysis. The glass transition temperature, storage modulus, and loss modulus for NCA/DCPD and NCA/CL copolymers with different cross-linking agent loading were compared using dynamic mechanical analysis. Cross-link density was examined to explain the very different dynamic mechanical behavior. Mechanical stress-strain curves were developed through tensile test, and thermal stability of the cross-linked polymers was evaluated by thermogravimetric analysis to further investigate the structure-property relationships in these systems.

  4. Heat shock protein 70 enhanced deoxyribonucleic acid base excision repair in human leukemic cells after ionizing radiation.

    PubMed

    Bases, Robert

    2006-01-01

    Base excision repair (BER) of DNA damage in irradiated THP1 human leukemic cells was stimulated by pretreating the cells with exogenous recombinant Hsp70. The treatment of THP1 cells with recombinant Hsp70 in cell culture promoted repair by reducing the frequency of apurinic, apyrimidinic (AP) sites in DNA before and after 1.3 Gy of radiation. However, by 30 minutes after 2.6 Gy, accelerated repair of abasic sites supervened, which may contribute to the loss of the very-low-dose cell hypersensitivity seen in clonogenic studies of other laboratories. After irradiation with 2.6 Gy, the crucial initial glycosylase step was markedly incomplete when cells had been transfected 24 hours before with a small interfering RNA (siRNA) designed to inhibit synthesis of Hsp70. In confirmation, lysates from irradiated siRNA-treated cells after 2.6 Gy were deficient in uracil glycosylase activity (UDG). Transfection with a scrambled RNA of the same size did not interfere with the glycosylase step, ie, the prompt conversion of damaged pyrimidine sites to abasic sites as well as the subsequent repair of those sites. BER measured by reduction of DNA AP sites before and after low-dose radiation was also deficient in THP1 cells that had been transfected with the siRNA designed to inhibit synthesis of Hsp70. These results implicate BER and the participation of Hsp70 in the repair of DNA in human leukemic cells with the doses of ionizing radiation used in clinical regimens. PMID:17009597

  5. Control of crosslinking for tailoring collagen-based scaffolds stability and mechanics

    PubMed Central

    Davidenko, N.; Schuster, C.F.; Bax, D.V.; Raynal, N.; Farndale, R.W.; Best, S.M.; Cameron, R.E.

    2015-01-01

    We provide evidence to show that the standard reactant concentrations used in tissue engineering to cross-link collagen-based scaffolds are up to 100 times higher than required for mechanical integrity in service, and stability against degradation in an aqueous environment. We demonstrate this with a detailed and systematic study by comparing scaffolds made from (a) collagen from two different suppliers, (b) gelatin (a partially denatured collagen) and (c) 50% collagen–50% gelatin mixtures. The materials were processed, using lyophilisation, to produce homogeneous, highly porous scaffolds with isotropic architectures and pore diameters ranging from 130 to 260 μm. Scaffolds were cross-linked using a carbodiimide treatment, to establish the effect of the variations in crosslinking conditions (down to very low concentrations) on the morphology, swelling, degradation and mechanical properties of the scaffolds. Carbodiimide concentration of 11.5 mg/ml was defined as the standard (100%) and was progressively diluted down to 0.1%. It was found that 10-fold reduction in the carbodiimide content led to the significant increase (almost 4-fold) in the amount of free amine groups (primarily on collagen lysine residues) without compromising mechanics and stability in water of all resultant scaffolds. The importance of this finding is that, by reducing cross-linking, the corresponding cell-reactive carboxylate anions (collagen glutamate or aspartate residues) that are essential for integrin-mediated binding remain intact. Indeed, a 10-fold reduction in carbodiimide crosslinking resulted in near native-like cell attachment to collagen scaffolds. We have demonstrated that controlling the degree of cross-linking, and hence retaining native scaffold chemistry, offers a major step forward in the biological performance of collagen- and gelatin-based tissue engineering scaffolds. Statement of Significance This work developed collagen and gelatine-based scaffolds with structural

  6. Anti-crease finishing of cotton fabrics based on crosslinking of cellulose with acryloyl malic acid.

    PubMed

    Qi, Huan; Huang, Yangen; Ji, Bolin; Sun, Gang; Qing, Feng-Ling; Hu, Chunyan; Yan, Kelu

    2016-01-01

    Maleic acid (MA) has been explored to replace formaldehyde-based dimethylol dihydroxy ethylene urea (DMDHEU) for cotton anti-crease finishing. However, the resilience of treated fabrics was not satisfactorily improved. In this study, acryloyl malic acid (AMA) was synthesized and applied on fabrics as a novel crosslinking agent. The results showed that both crease recovery angle and whiteness index of treated samples were higher than those of MA in the presence/absence of catalyst sodium hypophosphite (SHP). Chemical structure of AMA was confirmed by NMR and MS spectra. The possible crosslinking mechanism between AMA and cellulose was investigated by means of (13)C NMR, MS, FTIR and phosphorus content analyses. It was found that AMA could form ester bonds with cellulose by formation of anhydride intermediate. Meanwhile, additional reaction of double bonds on AMA with another molecule or PH of SHP residual has also contributed to the crosslinking. A reaction equation was proposed based on the analyses. PMID:26453855

  7. Ionic liquids-based crosslinked copolymer sorbents for headspace solid-phase microextraction of polar alcohols.

    PubMed

    Feng, Juanjuan; Sun, Min; Wang, Xusheng; Liu, Xia; Jiang, Shengxiang

    2012-07-01

    Halogen-based polymeric ionic liquid (PIL) fibers, which have proved efficient for solid-phase microextraction (SPME) of polar compounds, were with very limited fiber lifetimes. In this work, a novel crosslinked PIL sorbent with satisfactory stability and durability was prepared in situ via crosslinking polymerization processes on microstructured-silver coated stainless steel wire. 1,1'-(1,6-Hexanediyl)bis(1-vinylimidazolium) bibromide ionic liquid was synthesized and used as the crosslinking agent, with 1-vinyl-3-octylimidazolium bromide as monomer. Extraction properties of the fiber for polar alcohols in polar aqueous matrix were examined using headspace SPME (HS-SPME) coupled to gas chromatography-flame ionization detection (GC-FID). Under the optimized extraction and desorption conditions, the established method exhibited high extraction capacity. Wide linear ranges were obtained with correlation coefficients (R) ranging from 0.9947 to 0.9999. Limits of detection were in the range of 0.5-20 μg L⁻¹. Compared with the non-crosslinked PIL fiber, the proposed crosslinked PIL fiber was with higher thermal stability and durability and longer lifetime. Four different liquor beverages were analyzed as real samples and good results were obtained. PMID:22673810

  8. Effect of crosslinking in chitosan/aloe vera-based membranes for biomedical applications.

    PubMed

    Silva, S S; Caridade, S G; Mano, J F; Reis, R L

    2013-10-15

    The positive interaction between polysaccharides with active phytochemicals found in medicinal plants may represent a strategy to create active wound dressing materials useful for skin repair. In the present work, blended membranes composed of chitosan (Cht) and aloe vera gel were prepared through the solvent casting, and were crosslinked with genipin to improve their properties. Topography, swelling, wettability, mechanical properties and in vitro cellular response of the membranes were investigated. With the incorporation of aloe vera gel into chitosan solution, the developed chitosan/aloe-based membranes displayed increased roughness and wettability; while the genipin crosslinking promoted the formation of stiffer membranes in comparison to those of the non-modified membranes. Moreover, in vitro cell culture studies evidenced that the L929 cells have high cell viability, confirmed by MTS test and calcein-AM staining. The findings suggested that both blend compositions and crosslinking affected the physico-chemical properties and cellular behavior of the developed membranes. PMID:23987385

  9. Electron beam irradiation crosslinked hydrogels based on tyramine conjugated gum tragacanth.

    PubMed

    Tavakol, Moslem; Dehshiri, Saeedeh; Vasheghani-Farahani, Ebrahim

    2016-11-01

    In the present study, electron beam irradiation was applied to prepare a chemically crosslinked hydrogel based on tyramine conjugated gum tragacanth. Then, the gel content, swelling behavior and cytotoxicity of the hydrogels were evaluated. The gel content of the hydrogels was in the range of 75-85%. Equilibrium swelling degree of the hydrogels decreased from 51 to 14 with increasing polymer concentration and irradiation dose. Moisture retention capability of the hydrogels after 5h incubation at 37°C was in the range of 45-52 that is comparable with of commercial hydrogels. The cytotoxicity analysis showed the good biocompatibility of hydrogels. These results indicated that electron beam irradiation is a promising method to prepare chemically crosslinked tyramine conjugated gum tragacanth hydrogels for biomedical applications. Also, the versatility of electron beam irradiation for crosslinking of a variety of polymers possessing tyramine groups was demonstrated. PMID:27516298

  10. Carbon Nanofiber Incorporated Silica Based Aerogels with Di-Isocyanate Cross-Linking

    NASA Technical Reports Server (NTRS)

    Vivod, Stephanie L.; Meador, Mary Ann B.; Capadona, Lynn A.; Sullivan, Roy M.; Ghosn, Louis J.; Clark, Nicholas; McCorkle, Linda

    2008-01-01

    Lightweight materials with excellent thermal insulating properties are highly sought after for a variety of aerospace and aeronautic applications. (1) Silica based aerogels with their high surface area and low relative densities are ideal for applications in extreme environments such as insulators for the Mars Rover battery. (2) However, the fragile nature of aerogel monoliths prevents their widespread use in more down to earth applications. We have shown that the fragile aerogel network can be cross-linked with a di-isocyanate via amine decorated surfaces to form a conformal coating. (3) This coating reinforces the neck regions between secondary silica particles and significantly strengthens the aerogels with only a small effect on density or porosity. Scheme 1 depicts the cross-linking reaction with the di-isocyanate and exhibits the stages that result in polymer cross-linked aerogel monoliths.

  11. Fabrication of starch-based microparticles by an emulsification-crosslinking method

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Starch-based microparticles (MPs) fabricated by a water-in-water (w/w) emulsification-crosslinking method could be used as a controlled-release delivery vehicle for food bioactives. Due to the processing route without the use of toxic organic solvents, it is expected that these microparticles can be...

  12. Biodegradable Photo-Crosslinked Thin Polymer Networks Based on Vegetable Oil Hydroxyfatty Acids

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Novel crosslinked thin polymer networks based on vegetable oil hydroxyfatty acids (HFAs) were prepared by UV photopolymerization and their mechanical properties were evaluated. Two raw materials, castor oil and 7,10-dihydroxy-8(E)-octadecenoic acid (DOD) were used as sources of mono- and di-HFAs, r...

  13. Self-crosslinking for dimensionally stable and solvent-resistant quaternary phosphonium based hydroxide exchange membranes

    SciTech Connect

    Gu, S; Cai, R; Yan, YS

    2011-01-01

    A simple self-crosslinking strategy, without the needs of a separate crosslinker or a catalyst, is reported here. The crosslinking drastically lowers the water swelling ratio (e.g., 5-10 folds reduction) and provides excellent solvent-resistance. The self-crosslinked membrane (DCL: 5.3%) shows the highest IEC-normalized hydroxide conductivity among all crosslinked HEMs reported.

  14. Is dialdehyde starch a valuable cross-linking agent for collagen/elastin based materials?

    PubMed

    Skopinska-Wisniewska, J; Wegrzynowska-Drzymalska, K; Bajek, A; Maj, M; Sionkowska, A

    2016-04-01

    Collagen and elastin are the main structural proteins in mammal bodies. They provide mechanical support, strength, and elasticity to various organs and tissues, e.g. skin, tendons, arteries, and bones. They are readily available, biodegradable, biocompatible and they stimulate cell growth. The physicochemical properties of collagen and elastin-based materials can be modified by cross-linking. Glutaraldehyde is one of the most efficient cross-linking agents. However, the unreacted molecules can be released from the material and cause cytotoxic reactions. Thus, the aim of our work was to investigate the influence of a safer, macromolecular cross-linking agent-dialdehyde starch (DAS). The properties of hydrogels based on collagen/elastin mixtures (95/5, 90/10) containing 5 and 10 % of DAS and neutralized via dialysis against deionized water were tested. The homogenous, transparent, stiff hydrogels were obtained. The DAS addition causes the formation of intermolecular cross-linking bonds but does not affect the secondary structure of the proteins. As a result, the thermal stability, mechanical strength, and, surprisingly, swelling ability increased. At the same time, the surface properties test and in vitro study show that the materials are attractive for 3T3 cells. Moreover, the materials containing 10 % of DAS are more resistant to enzymatic degradation. PMID:26886815

  15. Studies of magnetic alginate-based electrospun matrices crosslinked with different methods for potential hyperthermia treatment.

    PubMed

    Chen, Yen-Hsuan; Cheng, Chi-Hui; Chang, Wan-Ju; Lin, Yi-Ching; Lin, Feng-Huei; Lin, Jui-Che

    2016-05-01

    The magnetic electrospun mats were lately established as an innovative biomaterial for hyperthermic cancer treatment. Unlike those surface-modified magnetic nanoparticles that may not firmly adhere onto the tumor for long-term duration, the magnetic mats with nanofibrous structure can promote cell adhesion and kill the tumor directly within an alternating magnetic field. However, most magnetic electrospun mats were fabricated using non-biodegradable polymers and organic solvents, causing the problems of removal after therapy and the suspected biotoxicity associated with residual solvent. Alginate (SA) was utilized in this investigation as the main material for electrospinning because of being biodegradable and water-soluble. The alginate-based electrospun mats were then treated by an ionic or a covalent crosslinking method, and then followed by chelation with Fe(2+)/Fe(3+) for chemical coprecipitation of Fe3O4 magnetic nanoparticles. Significant less cytotoxicity was noted on both liquid extracts from the ionic-crosslinked (Fe3O4-SA/PEO) and covalent-crosslinked (Fe3O4-SA/PVA) magnetic electrospun mats as well as the surface of Fe3O4-SA/PVA. In vitro hyperthermia assay indicated that the covalent-crosslinked magnetic alginate-based mats reduced tumor cell viability greater than Fe3O4 nanoparticles. Such magnetic electrospun mats are of potential for hyperthermia treatment by endoscopic/surgical delivery as well as serving as a supplementary debridement treatment after surgical tumor removal. PMID:26952432

  16. Base excision repair enzymes protect abasic sites in duplex DNA from interstrand cross-links.

    PubMed

    Admiraal, Suzanne J; O'Brien, Patrick J

    2015-03-10

    Hydrolysis of the N-glycosyl bond between a nucleobase and deoxyribose leaves an abasic site within duplex DNA. The abasic site can react with exocyclic amines of nucleobases on the complementary strand to form interstrand DNA-DNA cross-links (ICLs). We find that several enzymes from the base excision repair (BER) pathway protect an abasic site on one strand of a DNA duplex from cross-linking with an amine on the opposing strand. Human alkyladenine DNA glycosylase (AAG) and Escherichia coli 3-methyladenine DNA glycosylase II (AlkA) accomplish this by binding tightly to the abasic site and sequestering it. AAG protects an abasic site opposite T, the product of its canonical glycosylase reaction, by a factor of ∼10-fold, as estimated from its inhibition of the reaction of an exogenous amine with the damaged DNA. Human apurinic/apyrimidinic site endonuclease 1 and E. coli endonuclease III both decrease the amount of ICL at equilibrium by generating a single-strand DNA nick at the abasic position as it is liberated from the cross-link. The reversibility of the reaction between amines and abasic sites allows BER enzymes to counter the potentially disruptive effects of this type of cross-link on DNA transactions. PMID:25679877

  17. Effect of cross-linking on sorption properties of a denture-base material.

    PubMed

    Jagger, R G; Huggett, R

    1990-10-01

    Cross-linking of the polymer of the interstitial matrix of a heat-cured resin denture base is said to provide craze resistance for the denture base. The mechanism of crazing can be related to both water sorption and solvent attack. The present study shows that the addition of ethylene glycol dimethacrylate in concentrations of 0-100% of monomer volume has little effect on water sorption properties but is an efficient method of providing solvent resistance. PMID:2086306

  18. Hyaluronic acid-based hydrogels crosslinked by copper-catalyzed azide-alkyne cycloaddition with tailorable mechanical properties.

    PubMed

    Piluso, Susanna; Hiebl, Bernhard; Gorb, Stanislav N; Kovalev, Alexander; Lendlein, Andreas; Neffe, Axel T

    2011-02-01

    Biopolymers of the extracellular matrix are attractive starting materials for providing degradable and biocompatible biomaterials. In this study, hyaluronic acid-based hydrogels with tunable mechanical properties were prepared by the use of copper- catalyzed azide-alkyne cycloaddition (known as "click chemistry"). Alkyne-functionalized hyaluronic acid was crosslinked with linkers having two terminal azide functionalities, varying crosslinker density as well as the lengths and rigidity of the linker molecules. By variation of the crosslinker density and crosslinker type, hydrogels with elastic moduli in the range of 0.5-4 kPa were prepared. The washed materials contained a maximum of 6.8 mg copper per kg dry weight and the eluate of the gel crosslinked with diazidostilbene did not show toxic effects on L929 cells. The hyaluronic acid-based hydrogels have potential as biomaterials for cell culture or soft tissue regeneration applications. PMID:21374560

  19. Enzymatic Cross-Linking of Resilin-Based Proteins for Vascular Tissue Engineering Applications.

    PubMed

    Kim, Yeji; Gill, Emily E; Liu, Julie C

    2016-08-01

    Protein-based biomaterials have received significant attention for tissue engineering applications. For example, resilin-based protein gels have been produced with different cross-linking chemistries for applications in cartilage, cardiovascular, and vocal fold engineering. In this study, we investigate an alternative cross-linking chemistry to form resilin-based protein hydrogels and demonstrate the versatility of the gels for investigating cell response to matrix stiffness. Specifically, transglutaminase was used to cross-link proteins and resulted in gel surfaces more suitable for long-term cell attachment compared to those formed by a Mannich-type condensation reaction. Since matrix stiffness is an important determinant in modulating cell response, we first tuned matrix stiffness by varying total protein concentration. Next, we observed that matrix stiffness modulated cell spreading and endothelial differentiation of human mesenchymal stem cells. In particular, our results show that cells differentiated on our matrices, which have a stiffness similar to subendothelial layers, had statistically equivalent endothelial function compared to cells differentiated on hard glass surfaces. Thus, our protein-based matrix system is a promising tool to provide substrates favorable for long-term cell attachment and better mimics the native subendothelial environment compared to conventional hard culture substrates. PMID:27400383

  20. Thermal diffusivity of hexagonal boron nitride composites based on cross-linked liquid crystalline polyimides.

    PubMed

    Shoji, Yu; Higashihara, Tomoya; Tokita, Masatoshi; Morikawa, Junko; Watanabe, Junji; Ueda, Mitsuru

    2013-04-24

    Hexagonal boron nitride (h-BN) composites with the oriented cross-linked liquid crystalline (LC) polyimide have been developed as high thermally conductive materials. Well-dispersed h-BN composite films were obtained, as observed by scanning electron microscopy. The morphology of the composite films was further investigated in detail by the wide-angle X-ray diffraction. The obtained composite films based on the cross-linked LC polyimide showed that the polymer chains vertically aligned in the direction parallel to the films, while those based on the amorphous polyimide showed an isotropic nature. Moreover, the alignment of the cross-linked LC polyimides was maintained, even after increasing the volume fraction of h-BN. This alignment plays an important role in the effective phonon conduction between h-BN and the matrices. Indeed, the thermal diffusivity in the thickness direction of the composite films based on the LC polyimide measured by a temperature wave analysis method was increased to 0.679 mm(2) s(-1) at a 30 vol % h-BN loading, which was higher than that based on the amorphous polyimide. PMID:23506319

  1. Radiation-crosslinking of shape memory polymers based on poly(vinyl alcohol) in the presence of carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Basfar, A. A.; Lotfy, S.

    2015-01-01

    Shape memory polymers based on poly(vinyl alcohol) (SM-PVA) in the presence of 2-carboxyethyl acrylate oligomers (CEA) and multi-wall carbon nanotubes (MWCNTs) crosslinked by ionizing radiation were investigated. Chemical-crosslinking of PVA by glutaraldehyde in the presence of CEA and MWCNTs was also studied. The swelling and gel fraction of the radiation-crosslinked SM-PVA and chemically crosslinked systems were evaluated. Analysis of the swelling and gel fraction revealed a significant reduction in swelling and an increase in the gel fraction of the material that was chemically crosslinked with glutaraldehyde. The radiation-crosslinked SM-PVA demonstrated 100% gelation at an irradiation dose of 50 kGy. In addition, radiation-crosslinked SM-PVA exhibited good temperature responsive shape-memory behavior. A scanning electron microscopy (SEM) analysis was performed. The thermal properties of radiation-crosslinked SM-PVA were investigated by a thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). The ability of the material to return or store energy (E‧), to its ability to lose energy (E″), and the ratio of these effects (Tanδ), which is called damping were examined via DMA. The temperature of Tanδ in the radiation-crosslinked SM-PVA decreased significantly by 6 and 13 °C as a result of the addition of MWCNTs. In addition, the temperature of Tanδ for SM-PVA increased as the irradiation dose increased. These radiation-crosslinked SM-PVA materials show promising shape-memory behavior based on the range of temperatures at which Tanδ appears.

  2. Photo-crosslinkable hydrogel-based 3D microfluidic culture device.

    PubMed

    Lee, Youlee; Lee, Jong Min; Bae, Pan-Kee; Chung, Il Yup; Chung, Bong Hyun; Chung, Bong Geun

    2015-04-01

    We developed the photo-crosslinkable hydrogel-based 3D microfluidic device to culture neural stem cells (NSCs) and tumors. The photo-crosslinkable gelatin methacrylate (GelMA) polymer was used as a physical barrier in the microfluidic device and collagen type I gel was employed to culture NSCs in a 3D manner. We demonstrated that the pore size was inversely proportional to concentrations of GelMA hydrogels, showing the pore sizes of 5 and 25 w/v% GelMA hydrogels were 34 and 4 μm, respectively. It also revealed that the morphology of pores in 5 w/v% GelMA hydrogels was elliptical shape, whereas we observed circular-shaped pores in 25 w/v% GelMA hydrogels. To culture NSCs and tumors in the 3D microfluidic device, we investigated the molecular diffusion properties across GelMA hydrogels, indicating that 25 w/v% GelMA hydrogels inhibited the molecular diffusion for 6 days in the 3D microfluidic device. In contrast, the chemicals were diffused in 5 w/v% GelMA hydrogels. Finally, we cultured NSCs and tumors in the hydrogel-based 3D microfluidic device, showing that 53-75% NSCs differentiated into neurons, while tumors were cultured in the collagen gels. Therefore, this photo-crosslinkable hydrogel-based 3D microfluidic culture device could be a potentially powerful tool for regenerative tissue engineering applications. PMID:25641332

  3. Crosslinked hydrogels based on biological macromolecules with potential use in skin tissue engineering.

    PubMed

    Vulpe, Raluca; Popa, Marcel; Picton, Luc; Balan, Vera; Dulong, Virginie; Butnaru, Maria; Verestiuc, Liliana

    2016-03-01

    Zero-length crosslinked hydrogels have been synthesized by covalent linking of three natural polymers (collagen, hyaluronic acid and sericin), in the presence of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-hydroxysuccinimide. The hydrogels have been investigated by FT-IR spectroscopy, microcalorimetry, in vitro swelling, enzymatic degradation, and in vitro cell viability studies. The obtained crosslinked hydrogels showed a macroporous structure, high swelling degree and in vitro enzymatic resistance compared to uncrosslinked collagen. The in vitro cell viability studies performed on normal human dermal fibroblasts assessed the sericin proliferation properties indicating a potential use of the hydrogels based on collagen, hyaluronic acid and sericin in skin tissue engineering. PMID:26704998

  4. Structural Analysis and Mechanical Characterization of Hyaluronic Acid-Based Doubly Cross-Linked Networks.

    PubMed

    Jha, Amit K; Hule, Rohan A; Jiao, Tong; Teller, Sean S; Clifton, Rodney J; Duncan, Randall L; Pochan, Darrin J; Jia, Xinqiao

    2009-01-01

    We have created a new class of hyaluronic acid (HA)-based hydrogel materials with HA hydrogel particles (HGPs) embedded in and covalently cross-linked to a secondary network. HA HGPs with an average diameter of ∼900 nm and narrow particle size distribution were synthesized using a refined reverse micelle polymerization technique. The average mesh size of the HGPs was estimated to be approximately 5.5 to 7.0 nm by a protein uptake experiment. Sodium periodate oxidation not only introduced aldehyde groups to the particles but also reduced the average particle size. The aldehyde groups generated were used as reactive handles for subsequent cross-linking with an HA derivative containing hydrazide groups. The resulting macroscopic gels contain two distinct hierarchical networks (doubly cross-linked networks, DXNs): one within individual particles and another among different particles. Bulk gels (BGs) formed by direct mixing of HA derivatives with mutually reactive groups were included for comparison. The hydrogel microstructures were collectively characterized by microscopy and neutron scattering techniques. Their viscoelasticity was quantified at low frequencies (0.1-10 Hz) using a controlled stress rheometer and at high frequencies (up to 200 Hz) with a home-built torsional wave apparatus. Both BGs and DXNs are stable elastic gels that become stiffer at higher frequencies. The HA-based DXN offers unique structural hierarchy and mechanical properties that are suitable for soft tissue regeneration. PMID:20046226

  5. Structural Analysis and Mechanical Characterization of Hyaluronic Acid-Based Doubly Cross-Linked Networks

    PubMed Central

    Jha, Amit K.; Hule, Rohan A.; Jiao, Tong; Teller, Sean S.; Clifton, Rodney J.; Duncan, Randall L.; Pochan, Darrin J.; Jia, Xinqiao

    2009-01-01

    We have created a new class of hyaluronic acid (HA)-based hydrogel materials with HA hydrogel particles (HGPs) embedded in and covalently cross-linked to a secondary network. HA HGPs with an average diameter of ∼900 nm and narrow particle size distribution were synthesized using a refined reverse micelle polymerization technique. The average mesh size of the HGPs was estimated to be approximately 5.5 to 7.0 nm by a protein uptake experiment. Sodium periodate oxidation not only introduced aldehyde groups to the particles but also reduced the average particle size. The aldehyde groups generated were used as reactive handles for subsequent cross-linking with an HA derivative containing hydrazide groups. The resulting macroscopic gels contain two distinct hierarchical networks (doubly cross-linked networks, DXNs): one within individual particles and another among different particles. Bulk gels (BGs) formed by direct mixing of HA derivatives with mutually reactive groups were included for comparison. The hydrogel microstructures were collectively characterized by microscopy and neutron scattering techniques. Their viscoelasticity was quantified at low frequencies (0.1−10 Hz) using a controlled stress rheometer and at high frequencies (up to 200 Hz) with a home-built torsional wave apparatus. Both BGs and DXNs are stable elastic gels that become stiffer at higher frequencies. The HA-based DXN offers unique structural hierarchy and mechanical properties that are suitable for soft tissue regeneration. PMID:20046226

  6. Sequential design of a novel PVA-based crosslinked ethylenic homopolymer for extended drug delivery.

    PubMed

    Pillay, Viness; Sibanda, Wilbert; Danckwerts, Michael P

    2005-09-14

    A Box-Behnken Design was employed to study the influence of boric acid, sodium sulfate, ammonia and n-propanol in the formulation of crosslinked ethylenic homopolymeric (CEH) gelispheres from native polyvinyl alcohol (PVA). The dependent variables studied included the size of the spherical gelispheres, drug encapsulation efficiency, in vitro dissolution after 30 min and textural parameters, namely fracture force and matrix rupture energy. Based on these responses, an optimized CEH gelisphere matrix was formulated and thereafter incorporated as a powder into a candidate crosslinked zinc-pectinate multiple-unit device to assess its effect on modifying drug release. In the case of the CEH-loaded zinc-pectinate gelispheres, it was determined via constrained optimization that a maximum drug encapsulation efficiency of 28.63% could be obtained under the conditions of 0% (w/v) CEH, 13 h of crosslinking and drying temperature of 60 degrees C. On the other hand, initial drug release could be significantly retarded when 0.10% (w/v) of CEH was included in the formulation and crosslinked for 24 h at 40 degrees C. In this regard, CEH induced a 4 h lag phase. Furthermore, zero-order drug release was produced and could be maintained over several weeks. Kinetic analysis of drug release further supported that CEH inhibits polymer relaxation (k2Based on these results, the CEH-zinc-pectinate drug delivery system appears to be a suitable carrier that may be employed for long-term administration for, e.g. via subcutaneous implantation. PMID:16023807

  7. Rheological study of in-situ crosslinkable hydrogels based on hyaluronanic acid, collagen and sericin.

    PubMed

    Vulpe, Raluca; Le Cerf, Didier; Dulong, Virginie; Popa, Marcel; Peptu, Catalina; Verestiuc, Liliana; Picton, Luc

    2016-12-01

    The elaboration of chemically crosslinked hydrogels based on collagen (C), hyaluronanic acid (HA) and sericin (S) with different polymer ratios was investigated by in-situ rheology. This reaction was performed via amide or ester bond reaction activated by carbodiimide, in pure water. Prior to molecule crosslinking, the rheological behaviour of the biopolymers (alone or in mixture) was characterized in a semi-dilute concentration regime. Both flow and dynamic measurements showed that uncrosslinked collagen alone appears to be rather elastic with yield stress properties, whereas uncrosslinked HA alone appears to be rather shear thinning and viscoelastic in agreement with entangled polymer behaviour. Sericin exhibited Newtonian low viscosity behaviour according to its very low molar mass. Before crosslinking, HA exhibited viscoelastic behaviour at concentrations above the critical entangled concentration (C*) in the mixtures, thus HA shows promise as a matrix for future crosslinked networks, whereas sericin did not significantly modify the rheology. During the reaction, followed by rheology, the kinetics were slower for pure HA systems compared with the mixtures (i.e., with added collagen and/or to a lesser extent sericin). At the same time, the final network of hydrogels (i.e., the elastic modulus) was more structured in the mixture based systems. This result is explained by ester bonds (the only possibility for pure HA systems), which are less favourable and reactive than amide bonds (possible with sericin and collagen). The presence of collagen in the HA matrix reinforced the hydrogel network. SEM studies confirmed the structure of the hydrogels, and in vitro degradability was globally consistent with the effect of the selected enzyme according to the hydrogel composition. All the elaborated hydrogels were non-cytotoxic in vitro. PMID:27612727

  8. Acid–base bifunctional shell cross-linked micelle nanoreactor for one-pot tandem reaction

    SciTech Connect

    Lee, Li -Chen; Lu, Jie; Weck, Marcus; Jones, Christopher W.

    2015-12-29

    Shell cross-linked micelles (SCMs) containing acid sites in the shell and base sites in the core are prepared from amphiphilic poly(2-oxazoline) triblock copolymers. The materials are utilized as two-chamber nanoreactors for a prototypical acid-base bifunctional tandem deacetalization-nitroaldol reaction. Furthermore, the acid and base sites are localized in different regions of the micelle, allowing the two steps in the reaction sequence to largely proceed in separate compartments, akin to the compartmentalization that occurs in biological systems.

  9. Mechanical properties and failure analysis of visible light crosslinked alginate-based tissue sealants.

    PubMed

    Charron, Patrick N; Fenn, Spencer L; Poniz, Alex; Oldinski, Rachael A

    2016-06-01

    Moderate to weak mechanical properties limit the use of naturally-derived tissue sealants for dynamic medical applications, e.g., sealing a lung leak. To overcome these limitations, we developed visible-light crosslinked alginate-based hydrogels, as either non-adhesive methacrylated alginate (Alg-MA) hydrogel controls, or oxidized Alg-MA (Alg-MA-Ox) tissue adhesive tissue sealants, which form covalent bonds with extracellular matrix (ECM) proteins. Our study investigated the potential for visible-light crosslinked Alg-MA-Ox hydrogels to serve as effective surgical tissue sealants for dynamic in vivo systems. The Alg-MA-Ox hydrogels were designed to be an injectable system, curable in situ. Burst pressure experiments were conducted on a custom-fabricated burst pressure device using constant air flow; burst pressure properties and adhesion characteristics correlated with the degrees of methacrylation and oxidation. In summary, visible light crosslinked Alg-MA-Ox hydrogel tissue sealants form effective seals over critically-sized defects, and maintain pressures up to 50mm Hg. PMID:26897093

  10. Diffusion Coefficients of Water and Leachables in Methacrylate-based Crosslinked Polymers using Absorption Experiments

    PubMed Central

    Parthasarathy, Ranganathan; Misra, Anil; Park, Jonggu; Ye, Qiang; Spencer, Paulette

    2012-01-01

    The diffusion of water into dentin adhesive polymers and leaching of unpolymerized monomer from the adhesive are linked to their mechanical softening and hydrolytic degradation. Therefore, diffusion coefficient data are critical for the mechanical design of these polymeric adhesives. In this study, diffusion coefficients of water and leachables were obtained for sixteen methacrylate-based crosslinked polymers using absorption experiments. The experimental mass change data was interpreted using numerical solution of the two-dimensional diffusion equations. The calculated diffusion coefficients varied from 1.05 × 10−8 cm2/sec (co-monomer TMTMA) to 3.15 × 10−8 cm2/sec (co-monomer T4EGDMA). Correlation of the diffusion coefficients with crosslink density and hydrophilicity showed an inverse trend (R2 = 0.41). The correlation of diffusion coefficient with crosslink density and hydrophilicity are closer for molecules differing by simple repeat units (R2 = 0.95). These differences in the trends reveal mechanisms of interaction of the diffusing water with the polymer structure. PMID:22430592

  11. Rheological characterization of cataplasm bases composed of cross-linked partially neutralized polyacrylate hydrogel.

    PubMed

    Wang, Jian; Zhang, Hongqin; An, Dianyun; Yu, Jian; Li, Wei; Shen, Teng; Wang, Jianxin

    2014-10-01

    Viscoelasticity is a useful parameter for characterizing the intrinsic properties of the cross-linked polyacrylate hydrogel used in cataplasm bases. The aim of this study was to investigate the effects of various formulation parameters on the rheological characteristics of polyacrylate hydrogel. The hydrogel layers were formed using a partially neutralized polyacrylate (Viscomate(™)), which contained acrylic acid and sodium acrylate in different copolymerization ratios, as the cross-linked gel framework. Dihydroxyaluminum aminoacetate (DAAA), which produces aluminum ions, was used as the cross-linking agent. Rheological analyses were performed using a "stress amplitude sweep" and a "frequency sweep". The results showed that greater amounts of acrylic acid in the structure of Viscomate as well as higher concentrations of DAAA and Viscomate led to an increase in the elastic modulus (G'). However, greater amounts of acrylic acid in the structure of Viscomate and higher concentrations of DAAA had an opposite on the viscous modulus (G″); this might be owing to higher steric hindrance. The results of this study can serve as guidelines for the optimization of formulations for cataplasms. PMID:24865937

  12. Organic field-effect transistors based on a crosslinkable polymer blend as the semiconducting layer

    NASA Astrophysics Data System (ADS)

    Yan, He; Yoon, Myung-Han; Facchetti, Antonio; Marks, Tobin J.

    2005-10-01

    For fabrication of top-gate polymer-based organic field-effect transistors (OFETs), it is essential that the semiconducting layer remain intact during spin coating of the overlying dielectric layer. This requirement severely limits the applicable solvent and materials combinations. We show here that a crosslinkable polymer blend consisting of a p-type semiconducting polymer {e.g., TFB; poly[9,9-dioctyl-fluorene-co-N-(4-butylphenyl)-diphenylamine]} and an electroactive crosslinkable silyl reagent {e.g., TPDSi2; 4,4'-bis[(p-trichloro-silylpropylphenyl)phenylamino]biphenyl} is effective as the semiconducting layer in a top-gate bottom-contact OFET device. The TFB +TPDSi2 semiconducting blend is prepared by spin-coating in ambient. The crosslinking process occurs during spin-coating in air and is completed by curing at 90 °C, which renders the resulting film insoluble in common organic solvents and allows subsequent deposition of dielectric layers from a wide range of organic solvents. We also show that the presence of TPDSi2 in the semiconductor layer significantly reduces typical TFB-source-drain threshold voltages in bottom-contact devices, likely due to favorable interfacial TPDSi2-gold electrode interactions.

  13. Identification of Cross-Linked Peptides after Click-Based Enrichment Using Sequential Collision-Induced Dissociation and Electron Transfer Dissociation Tandem Mass Spectrometry

    SciTech Connect

    Chowdhury, Saiful M.; Du, Xiuxia; Tolic, Nikola; Wu, Si; Moore, Ronald J.; Mayer, M. Uljana; Smith, Richard D.; Adkins, Joshua N.

    2009-07-01

    Chemical cross-linking combined with mass spectrometric analysis is emerging as a powerful technique for protein-protein interaction and protein structure elucidation studies.1 Cross-linkers covalently link two interacting proteins, often with chemistries specific to certain amino acid side chains. After enzymatic digestion of the proteins, the resulting cross-linked peptides can be subjected to analysis by LC-MS(/MS) to identify cross-linked species.2,3 For studying protein interactions using chemical cross-linking towards global discovery-based applications, the critical needs are the development of cross-linkers that are highly specific, amenable to LC-MS/MS, and resulting spectra are interpretable by bioinformatics tools to automatically assign cross-linked peptides with high confidence.4-10 As recently mentioned by Aebersold and co-workers, due to the low relative abundances of cross-linking products compared to their unmodified counterparts, enrichment of cross-linked species is also highly desirable to improve the likelihood of unambiguous identification of cross-linked peptides.6 Most of the currently available enrichable cross-linkers are bulky and are not amenable to studying protein-protein interactions in vivo. To discover protein-protein interactions with high confidence, there is a need for chemical cross-linkers that can effectively label protein complexes, utilize mass spectrometry based bottom-up proteomics analysis pipelines and also contains enrichment functionality.

  14. Fine-tuning in mineral cross-linking of biopolymer nanoparticle for incorporation and release of cargo.

    PubMed

    Fukui, Yuuka; Kabayama, Narumi; Fujimoto, Keiji

    2015-12-01

    We developed a mineral cross-linking strategy to prepare a biopolymer-based nanoparticle using calcium phosphate (CaP) as a cross-linker. Nanoparticles were first formed by mixing deoxyribonucleic acid (DNA) with cationic surfactants, and were cross-linked by CaP precipitation. After removal of the surfactants, we carried out the alternative dialysis of nanoparticles against CaCl2 aqueous solution and phosphate buffered solution for further mineral cross-linking. XRD and FT-IR studies revealed that the resultant nanoparticles were produced by mineral cross-linkages of hydroxyapatite (HAp) and the crystal amount and properties such as morphology and crystallinity could be well-controlled by the reaction conditions. Chemical dyes could be incorporated into nanoparticles via their affinities with crystal faces of HAp and DNA. Their release was tunable by crystal amount and properties of mineral cross-linkages. Also, the release could be triggered by mineral dissolution in response to pH. Such a mineral cross-linking will open up a potential way to provide a nanoparticle with versatile functions such as cleavable cross-linking, binding affinity for cargos, and pH-responsive release. PMID:26387068

  15. Chitosan-based membranes with different ionic crosslinking density for pharmaceutical and industrial applications.

    PubMed

    Gierszewska, Magdalena; Ostrowska-Czubenko, Jadwiga

    2016-11-20

    Chitosan membranes (Ch), ionically crosslinked with pentasodium tripolyphosphate (TPP), were prepared using chitosan of medium and high molecular weight of similar degree of deacetylation and different crosslinking conditions. An effect of synthesis conditions (pH of crosslinking TPP solution equal to 5.5 and 9.0) on molecular and supermolecular structure and on crosslinking density of Ch/TPP membranes was confirmed using Fourier transform infrared spectroscopy (FTIR), wide-angle X-ray diffraction (WAXD) method and energy dispersive X-ray (EDX) spectrometry. Atomic-force microscopy (AFM) and contact angle measurements indicated some differences in membrane roughness and hydrophilicity. The state of water in non-crosslinked and ionically crosslinked Ch membranes containing different amount of water was investigated by low temperature differential scanning calorimetry (DSC) measurements. DSC analysis confirmed presence of freezing and non-freezing water in non-crosslinked and ionically crosslinked membranes. The amount of non-freezing water generally decreased after Ch crosslinking and was affected by crosslinking conditions and crosslinking density. Molecular weight of Ch had only slight influence on all characterized properties of ionically crosslinked membranes. PMID:27561522

  16. Photo-Crosslinking Induced Geometric Restriction Controls the Self-Assembly of Diphenylalanine Based Peptides

    NASA Astrophysics Data System (ADS)

    Tie, Zuo-Xiu; Qin, Meng; Zou, Da-Wei; Cao, Yi; Wang, Wei

    2011-02-01

    The diphenylalanine (FF) motif has been widely used in the design of peptides that are capable of forming various ordered structures, such as nanotubes, nanospheres and hydrogels. In these assemblies, FF based peptides adopt an antiparallel structure and are stabilized by π — π stacking among the phenyl groups. Here we show that assembly of FF-based peptides can be controlled by their geometric restrictions. Using tripeptide FFY (L-Phe-L-Phe-L-Tyr) as an example, we demonstrate that photo-crosslinking of C-terminal tyrosine can impose a geometric restriction to the formation of an antiparallel structure, leading to a structural change of the assemblies from nanosphere to amorphous. This finding is confirmed using far-UV circular dichroism, Fourier transform infrared spectroscopy and atomic force microscopy. Based on such a mechanism, we are able to control the gel-sol transition of Fmoc-FFY using the geometric restriction induced by photo-crosslinking of C-terminal tyrosine groups. We believe that geometric restriction should be considered as an important factor in the design of peptide-based materials. It can also be implemented as a useful strategy for the construction of environment-responsive “smart" materials.

  17. Graphene oxide-based benzimidazole-crosslinked networks for high-performance supercapacitors.

    PubMed

    Cui, Yi; Cheng, Qian-Yi; Wu, Haiping; Wei, Zhixiang; Han, Bao-Hang

    2013-09-21

    The synthesis of graphene oxide (GO)-based benzimidazole-crosslinked network (GOBIN) materials is presented. These materials are prepared by the covalent crosslinking of GO sheets using a condensation reaction between the carboxylic acid moieties on the GO surface and the o-aminophenyl end groups of 3,3'-diaminobenzidine (or 1,2,4,5-benzenetetraamine tetrahydrochloride). An efficient one-pot catalyst- and template-free synthesis was performed. The obtained porous GO-based materials possess a Brunauer-Emmett-Teller specific surface area ranging from 260 to 920 m(2) g(-1). Electrochemical testing indicates that the GOBIN materials display a specific capacitance up to 370 F g(-1) at a current density of 0.1 A g(-1) and about 90% of the original capacitance is retained after 5000 cycles at a current density of 3 A g(-1). Therefore, GOBIN materials can be employed as promising electrode materials for high-performance supercapacitors with outstanding cycling stability. Furthermore, owing to their significantly high specific surface area, these materials also show hydrogen uptake (up to 1.24 wt%, at 77 K and 1.0 bar) and carbon dioxide capture (up to 14.2 wt%, at 273 K and 1.0 bar) properties. As a result, these GO-based porous materials improve both the supercapacitor performance and gas sorption property, which demonstrate an excellent performance in the practical application of energy storage. PMID:23793833

  18. Crosslinked, polymerized, and PEG-conjugated hemoglobin-based oxygen carriers: clinical safety and efficacy of recent and current products.

    PubMed

    Jahr, Jonathan S; Akha, Arezou Sadighi; Holtby, Randall J

    2012-09-01

    Blood substitutes, especially hemoglobin based oxygen carriers (HBOC) have been widely studied and reviewed over the past 30 years. The development of HBOCs was highlighted by crosslinking to minimize adverse effects. However, even early attempts at single crosslinking using alpha-alpha crosslinks or diaspirin crosslinking failed clinical trials due to renal morbidity and increased mortality. In fact, preclinical trials may have predicted failure of this first generation product, DCLHb (diaspirin-crosslinked Hb) (HemAssist ®, Baxter). In the 1980's, three small biopharmaceutical companies developed "second generation" HBOCs, the first being Hemosol with their raffinose crosslinked HBOC, hemoglobin- raffimer. The other two development programs modified the HBOC using glutaraldehyde polymerization, in an attempt to further alleviate the toxicities of the "first" generation HBOCs. This paper will review the definitive clinical trials of the two polymerized HBOCs, Biopure's hemoglobin glutamer-250 (bovine) and Northfield's polymerized human Hb, pegylated HBOC and Sangart's peg-conjugated HBOC, with an introductory brief review of Hemosol's hemoglobinraffimer. The paper will then introduce the newest polymerized hemoglobin, zero-linked hemoglobin polymer, which has not yet undergone clinical trials but has undergone some preclinical work that will be discussed in a section on this product. As a new generation HBOC, zero-linked hemoglobin polymer may begin to address the issues presented by the first two generations of HBOCs, and may hold promise as a universally applicable HBOC. PMID:21745179

  19. A novel crosslinking strategy for preparing poly(vinyl alcohol)-based proton-conducting membranes with high sulfonation

    NASA Astrophysics Data System (ADS)

    Tsai, Chun-En; Lin, Chi-Wen; Hwang, Bing-Joe

    This study synthesizes poly(vinyl alcohol) (PVA)-based polymer electrolyte membranes by a two-step crosslinking process involving esterization and acetal ring formation reactions. This work also uses sulfosuccinic acid (SSA) as the first crosslinking agent to form an inter-crosslinked structure and a promoting sulfonating agent. Glutaraldehyde (GA) as the second crosslinking agent, reacts with the spare OH group of PVA and forms, not only a dense structure at the outer membrane surface, but also a hydrophobic protective layer. Compared with membranes prepared by a traditional one-step crosslinking process, membranes prepared by the two-step crosslinking process exhibit excellent dissolution resistance in water. The membranes become water-insoluble even at a molar ratio of SO 3H/PVA-OH as high as 0.45. Moreover, the synthesized membranes also exhibit high proton conductivities and high methanol permeability resistance. The current study measures highest proton conductivity of 5.3 × 10 -2 S cm -1 at room temperature from one of the synthesized membranes, higher than that of the Nafion ® membrane. Methanol permeability of the synthesized membranes measures about 1 × 10 -7 cm 2 S -1, about one order of magnitude lower than that of the Nafion ® membrane.

  20. Silica-Based, Hyper-Crosslinked Acid Stable Stationary Phases for High Performance Liquid Chromatography

    PubMed Central

    Zhang, Yu; Luo, Hao; Carr, Peter W.

    2011-01-01

    A new family of Hyper-Crosslinked (HC) phases has been recently introduced for use under very aggressive acid conditions including those encountered in ultra-fast, high temperature Two-Dimensional Liquid Chromatography (2DLC). This type of stationary phase showed significantly enhanced acid and thermal stability compared to the most acid stable, commercial RPLC phases. In addition, the use of “orthogonal” chemistry to make surface-confined polymer networks ensures good reproducibility and high efficiency. One of the most interesting features of the HC phases is the ability to derivatize the surface aromatic groups with various functional groups. This led to the development of a family of hyper-crosslinked phases possessing a wide variety of chromatographic selectivities by attaching hydrophobic (e.g. –C8), ionizable (e.g. -COOH, -SO3H), aromatic (e.g. –toluene) or polar (e.g. -OH) species to the aromatic polymer network. HC reversed phases with various degrees of hydrophobicity and mixed-mode HC phases with added strong and weak cation exchange sites have been synthesized, characterized and applied. These silica-based acid-stable HC phases, with their attractive chromatographic properties, should be very useful in the separations of bases or biological analytes in acidic media, especially at elevated temperatures. This work reviews the prior research on HC phases and introduces a novel HC phase made by alternative chemistry. PMID:21906745

  1. Photopolymerizable Nanogels as Macromolecular Precursors to Covalently Crosslinked Water-Based Networks

    PubMed Central

    Dailing, Eric A.; Setterberg, Whitney K.; Shah, Parag K.; Stansbury, Jeffrey W.

    2015-01-01

    We present a strategy for directly and efficiently polymerizing aqueous dispersions of reactive nanogels into covalently crosslinked polymer networks with properties that are determined by the initial chemical and physical nanogel structure. This technique can extend the range of achievable properties and architectures for networks formed in solution, particularly in water where monomer selection for direct polymerization and the final network properties are quite limited. Nanogels were initially obtained from a solution polymerization of a hydrophilic monomethacrylate and either a hydrophilic PEG-based dimethacrylate or a more hydrophobic urethane dimethacrylate, which produced globular particles with diameters of 10–15 nm with remarkably low polydispersity in some cases. Networks derived from a single type of nanogel or a blend of nanogels with different chemistries when dispersed in water gelled within minutes when exposed to low intensity UV light. Modifying the nanogel structure changes both covalent and non-covalent secondary interactions in the crosslinked networks and reveals critical design criteria for the development of networks from highly internally branched, nanoscale prepolymer precursors. PMID:26075300

  2. Composite nanoparticles based on hyaluronic acid chemically cross-linked with alpha,beta-polyaspartylhydrazide.

    PubMed

    Pitarresi, G; Craparo, E F; Palumbo, F S; Carlisi, B; Giammona, G

    2007-06-01

    In this paper, new composite nanoparticles based on hyaluronic acid (HA) chemically cross-linked with alpha,beta-polyaspartylhydrazide (PAHy) were prepared by the use of a reversed-phase microemulsion technique. HA-PAHy nanoparticles were characterized by FT-IR spectroscopy, confirming the occurrence of the chemical cross-linking, dimensional analysis, and transmission electron micrography, showing a sub-micrometer size and spherical shape. Zeta potential measurements demonstrated the presence of HA on the nanoparticle surface. A remarkable affinity of the obtained nanoparticles toward aqueous media that simulate some biological fluids was found. Stability studies showed the absence of chemical degradation in various media, while in the presence of hyaluronidase, a partial degradation occurred. Cell compatibility was evaluated by performing in vitro assays on human chronic myelogenous leukaemia cells (K-562) chosen as a model cell line and a haemolytic test. HA-PAHy nanoparticles were also able to entrap 5-fluorouracil, chosen as a model drug, and release it in a simulated physiological fluid and in human plasma with a mechanism essentially controlled by a Fickian diffusion. PMID:17521164

  3. Photopolymerizable nanogels as macromolecular precursors to covalently crosslinked water-based networks.

    PubMed

    Dailing, Eric A; Setterberg, Whitney K; Shah, Parag K; Stansbury, Jeffrey W

    2015-07-28

    We present a strategy for directly and efficiently polymerizing aqueous dispersions of reactive nanogels into covalently crosslinked polymer networks with properties that are determined by the initial chemical and physical nanogel structure. This technique can extend the range of achievable properties and architectures for networks formed in solution, particularly in water where monomer selection for direct polymerization and the final network properties are quite limited. Nanogels were initially obtained from a solution polymerization of a hydrophilic monomethacrylate and either a hydrophilic PEG-based dimethacrylate or a more hydrophobic urethane dimethacrylate, which produced globular particles with diameters of 10-15 nm with remarkably low polydispersity in some cases. Networks derived from a single type of nanogel or a blend of nanogels with different chemistries when dispersed in water gelled within minutes when exposed to low intensity UV light. Modifying the nanogel structure changes both covalent and non-covalent secondary interactions in the crosslinked networks and reveals critical design criteria for the development of networks from highly internally branched, nanoscale prepolymer precursors. PMID:26075300

  4. Stimuli sensitive super-macroporous cryogels based on photo-crosslinked 2-hydroxyethylcellulose and chitosan.

    PubMed

    Stoyneva, Veselina; Momekova, Denitsa; Kostova, Bistra; Petrov, Petar

    2014-01-01

    Original pH sensitive cryogels, based on two biodegradable natural polymers chitosan (CS) and 2-hydroxyethylcellulose (HEC), were obtained via cryogenic treatment of semi-dilute aqueous solutions and UV induced crosslinking in frozen state. H₂O₂ and N,N'-methylenebisacrylamide (BisAAm) were used as photoinitiator and crosslinking agent, respectively. BisAAm facilitated the formation of polymer co-network and increased both the gel fraction yield and mechanical strength of cryogels. The influence of chitosan content on the physico-mechanical properties of HEC-CS cryogels was investigated. In general, the increase of CS fraction in the polymer co-network increased the degree of swelling and enhanced significantly the storage modulus of materials. All HEC-CS cryogels obtained were opalescent sponge-like materials, which quickly release/uptake water due to their open porous structure. The incorporation of CS provided pH dependent swelling and good bioadhesive properties of cryogels. HEC-CS cryogels were further exploited as drug delivery systems of the highly water soluble drug metronidazole belonging to BCS Class l. PMID:24274575

  5. Transglutaminase crosslinked pectin- and chitosan-based edible films: a review.

    PubMed

    Porta, Raffaele; Mariniello, Loredana; Di Pierro, Prospero; Sorrentino, Angela; Giosafatto, Concetta Valeria L

    2011-03-01

    The production of biodegradable and edible films with desired mechanical characteristics and gas barrier properties represents one of the most advanced challenges in the field of food wrapping and coating. New edible films can serve not only to provide food with physical protection but also to reduce loss of their moisture, to restrict absorption of oxygen, to lessen migration of lipids, to improve their mechanical handling features, and as materials, to apply in direct contact with internal food to realize a multilayer food packaging. Polymers derived from natural products, like carbohydrates and proteins, offer the greatest opportunities as component of edible films since their biodegradability and environmental compatibility are assured and they can also supplement the nutritional value of specific foods. However, excessive water solubility and poor water vapor barrier properties, and often poor mechanical resistance, have their application limited until the present time. Numerous studies have been carried out to improve their properties by preparing composite and multi-component films or by physically and chemically crosslinking their natural components. In the present review we summarize the main results obtained by crosslinking with the enzyme transglutaminase different proteins contained in multi-component pectin- and chitosan-based edible films, having the aim to create environmentally-friendly "bioplastics" with mechanical and permeability properties similar to the ones exhibited by plastics of petrochemical origin. PMID:21390943

  6. Paper based colorimetric biosensing platform utilizing cross-linked siloxane as probe.

    PubMed

    Zhou, Miao; Yang, Minghui; Zhou, Feimeng

    2014-05-15

    Paper based colorimetric biosensing platform utilizing cross-linked siloxane 3-aminopropyltriethoxysilane (APTMS) as probe was developed for the detection of a broad range of targets including H2O2, glucose and protein biomarker. APTMS was extensively used for the modification of filter papers to develop paper based analytical devices. We discovered when APTMS was cross-linked with glutaraldehyde (GA), the resulting complex (APTMS-GA) displays brick-red color, and a visual color change was observed when the complex reacted with H2O2. By integrating the APTMS-GA complex with filter paper, the modified paper enables quantitative detection of H2O2 through the monitoring of the color intensity change of the paper via software Image J. Then, with the immobilization of glucose oxidase (GOx) onto the modified paper, glucose can be detected through the detection of enzymatically generated H2O2. For protein biomarker prostate specific antigen (PSA) assay, we immobilized capture, not captured anti-PSA antibody (Ab1) onto the paper surface and using GOx modified gold nanorod (GNR) as detection anti-PSA antibody (Ab2) label. The detection of PSA was also achieved via the liberated H2O2 when the GOx label reacted with glucose. The results demonstrated the possibility of this paper based sensor for the detection of different analytes with wide linear range. The low cost and simplicity of this paper based sensor could be developed for "point-of-care" analysis and find wide application in different areas. PMID:24361420

  7. The application of a crosslinked pectin-based wafer matrix for gradual buccal drug delivery.

    PubMed

    Shaikh, Rubina P; Pillay, Viness; Choonara, Yahya E; Du Toit, Lisa C; Ndesendo, Valence M K; Kumar, Pradeep; Khan, Riaz A

    2012-05-01

    The purpose of this study was to develop crosslinked wafer matrices and establish the influence of the crosslinker type and processing sequence on achieving gradual buccal drug delivery. Three sets of drug-loaded crosslinked pectin wafers were produced employing the model water-soluble antihistamine, diphenhydramine and were compared with noncrosslinked wafers. The formulations were crosslinked with CaCl(2), BaCl(2), or ZnSO(4) pre- or postlyophilization (sets 1 and 2) as well as pre- and postlyophilization (set 3), respectively. The surface morphology, porositometry, molecular vibrational transitions, textural attributes, thermal and in vitro drug release were characterized and supported by in silico molecular mechanics simulations. Results revealed that crosslinked wafers produced smaller pore sizes (107.63 Å) compared with noncrosslinked matrices (180.53 Å) due to molecular crosslinks formed between pectin chains. Drug release performance was dependent on the wafer crosslinking production sequence. Noncrosslinked wafers displayed burst-release with 82% drug released at t(30min) compared with first-order kinetic profiles obtained for prelyophilized crosslinked matrices (50% released at t(30min) followed by steady release). Wafers crosslinked postlyophilization displayed superior control of drug release (40% at t(30min)). Molecular mechanics simulations corroborated with the experimental data and established that Ba(++), having the largest atomic radii (1.35 Å) formed a number of ionic bridges producing wafers of higher porosity (0.048 cm(2)/g) and had more influence on drug release. PMID:22323418

  8. Gel-based chemical cross-linking analysis of 20S proteasome subunit-subunit interactions in breast cancer.

    PubMed

    Song, Hai; Xiong, Hua; Che, Jing; Xi, Qing-Song; Huang, Liu; Xiong, Hui-Hua; Zhang, Peng

    2016-08-01

    The ubiquitin-proteasome system plays a pivotal role in breast tumorigenesis by controlling transcription factors, thus promoting cell cycle growth, and degradation of tumor suppressor proteins. However, breast cancer patients have failed to benefit from proteasome inhibitor treatment partially due to proteasome heterogeneity, which is poorly understood in malignant breast neoplasm. Chemical crosslinking is an increasingly important tool for mapping protein three-dimensional structures and proteinprotein interactions. In the present study, two cross-linkers, bis (sulfosuccinimidyl) suberate (BS(3)) and its water-insoluble analog disuccinimidyl suberate (DSS), were used to map the subunit-subunit interactions in 20S proteasome core particle (CP) from MDA-MB-231 cells. Different types of gel electrophoresis technologies were used. In combination with chemical cross-linking and mass spectrometry, we applied these gel electrophoresis technologies to the study of the noncovalent interactions among 20S proteasome subunits. Firstly, the CP subunit isoforms were profiled. Subsequently, using native/SDSPAGE, it was observed that 0.5 mmol/L BS(3) was a relatively optimal cross-linking concentration for CP subunit-subunit interaction study. 2-DE analysis of the cross-linked CP revealed that α1 might preinteract with α2, and α3 might pre-interact with α4. Moreover, there were different subtypes of α1α2 and α3α4 due to proteasome heterogeneity. There was no significant difference in cross-linking pattern for CP subunits between BS(3) and DSS. Taken together, the gel-based characterization in combination with chemical cross-linking could serve as a tool for the study of subunit interactions within a multi-subunit protein complex. The heterogeneity of 20S proteasome subunit observed in breast cancer cells may provide some key information for proteasome inhibition strategy. PMID:27465334

  9. N-Alkylated dinitrones from isosorbide as cross-linkers for unsaturated bio-based polyesters.

    PubMed

    Goerz, Oliver; Ritter, Helmut

    2014-01-01

    Isosorbide was esterified with acryloyl chloride and crotonic acid yielding isosorbide diacrylate (9a) and isosorbide dicrotonate (9b), which were reacted with benzaldehyde oxime in the presence of zinc(II) iodide and boron triflouride etherate as catalysts to obtain N-alkylated dinitrones 10a/b. Poly(isosorbide itaconite -co- succinate) 13 as a bio-based unsaturated polyester was cross-linked by a 1,3-dipolar cycloaddition with the received dinitrones 10a/b. The 1,3-dipolar cycloaddition led to a strong change of the mechanical properties which were investigated by rheological measurements. Nitrones derived from methyl acrylate (3a) and methyl crotonate (3b) were used as model systems and reacted with dimethyl itaconate to further characterize the 1,3-dipolaric cycloaddition. PMID:24991239

  10. N-Alkylated dinitrones from isosorbide as cross-linkers for unsaturated bio-based polyesters

    PubMed Central

    Goerz, Oliver

    2014-01-01

    Summary Isosorbide was esterified with acryloyl chloride and crotonic acid yielding isosorbide diacrylate (9a) and isosorbide dicrotonate (9b), which were reacted with benzaldehyde oxime in the presence of zinc(II) iodide and boron triflouride etherate as catalysts to obtain N-alkylated dinitrones 10a/b. Poly(isosorbide itaconite -co- succinate) 13 as a bio-based unsaturated polyester was cross-linked by a 1,3-dipolar cycloaddition with the received dinitrones 10a/b. The 1,3-dipolar cycloaddition led to a strong change of the mechanical properties which were investigated by rheological measurements. Nitrones derived from methyl acrylate (3a) and methyl crotonate (3b) were used as model systems and reacted with dimethyl itaconate to further characterize the 1,3-dipolaric cycloaddition. PMID:24991239

  11. Gold nanoprobe-based non-crosslinking hybridization for molecular diagnostics.

    PubMed

    Larguinho, Miguel; Canto, Rafaela; Cordeiro, Milton; Pedrosa, Pedro; Fortuna, Andreia; Vinhas, Raquel; Baptista, Pedro V

    2015-01-01

    Non-crosslinking (NCL) approaches using DNA-modified gold nanoparticles for molecular detection constitute powerful tools with potential implications in clinical diagnostics and tailored medicine. From detection of pathogenic agents to identification of specific point mutations associated with health conditions, these methods have shown remarkable versatility and simplicity. Herein, the NCL hybridization assay is broken down to the fundamentals behind its assembly and detection principle. Gold nanoparticle synthesis and derivatization is addressed, emphasizing optimal size homogeneity and conditions for maximum surface coverage, with direct implications in downstream detection. The detection principle is discussed and the advantages and drawbacks of different NCL approaches are discussed. Finally, NCL-based applications for molecular detection of clinically relevant loci and potential integration into more complex biosensing platforms, projecting miniaturization and portability are addressed. PMID:26292557

  12. A self-healable and highly stretchable supercapacitor based on a dual crosslinked polyelectrolyte

    NASA Astrophysics Data System (ADS)

    Huang, Yan; Zhong, Ming; Huang, Yang; Zhu, Minshen; Pei, Zengxia; Wang, Zifeng; Xue, Qi; Xie, Xuming; Zhi, Chunyi

    2015-12-01

    Superior self-healability and stretchability are critical elements for the practical wide-scale adoption of personalized electronics such as portable and wearable energy storage devices. However, the low healing efficiency of self-healable supercapacitors and the small strain of stretchable supercapacitors are fundamentally limited by conventional polyvinyl alcohol-based acidic electrolytes, which are intrinsically neither self-healable nor highly stretchable. Here we report an electrolyte comprising polyacrylic acid dual crosslinked by hydrogen bonding and vinyl hybrid silica nanoparticles, which displays all superior functions and provides a solution to the intrinsic self-healability and high stretchability problems of a supercapacitor. Supercapacitors with this electrolyte are non-autonomic self-healable, retaining the capacitance completely even after 20 cycles of breaking/healing. These supercapacitors are stretched up to 600% strain with enhanced performance using a designed facile electrode fabrication procedure.

  13. A self-healable and highly stretchable supercapacitor based on a dual crosslinked polyelectrolyte.

    PubMed

    Huang, Yan; Zhong, Ming; Huang, Yang; Zhu, Minshen; Pei, Zengxia; Wang, Zifeng; Xue, Qi; Xie, Xuming; Zhi, Chunyi

    2015-01-01

    Superior self-healability and stretchability are critical elements for the practical wide-scale adoption of personalized electronics such as portable and wearable energy storage devices. However, the low healing efficiency of self-healable supercapacitors and the small strain of stretchable supercapacitors are fundamentally limited by conventional polyvinyl alcohol-based acidic electrolytes, which are intrinsically neither self-healable nor highly stretchable. Here we report an electrolyte comprising polyacrylic acid dual crosslinked by hydrogen bonding and vinyl hybrid silica nanoparticles, which displays all superior functions and provides a solution to the intrinsic self-healability and high stretchability problems of a supercapacitor. Supercapacitors with this electrolyte are non-autonomic self-healable, retaining the capacitance completely even after 20 cycles of breaking/healing. These supercapacitors are stretched up to 600% strain with enhanced performance using a designed facile electrode fabrication procedure. PMID:26691661

  14. Urethane-based stabilizers for radiation-crosslinked polyethylene. [Electron beams

    SciTech Connect

    Shkolnik, S.; Rajbenbach, L.A.

    1982-11-01

    Unsaturated urethane-based stabilizers for use in radiation-crosslinked polyethylene were synthesized. Aromatic amine moieties were attached to allylic and acrylic monomers by means of aromatic or aliphatic diisocyanates. The synthesized stabilizers were incorporated in high-density polyethylene films which were subjected to electron beam irradiation. The oxidative stability of the films prior to and after extraction was determined by DTA in the temperature range 185-210/sup 0/C and compared with samples treated with commercial amine-bearing antioxidants. Tensile strength and gel content were also determined. Best results were obtained with a stabilizer prepared from equimolecular amounts of allyl alcohol, tolylene-2,4-diisocyanate and N-phenyl-1,4-phenylenediamine. Estimated lifetimes at 70/sup 0/C of stabilized irradiated polyethylene samples were calculated.

  15. A highly reversible room-temperature lithium metal battery based on crosslinked hairy nanoparticles

    NASA Astrophysics Data System (ADS)

    Choudhury, Snehashis; Mangal, Rahul; Agrawal, Akanksha; Archer, Lynden A.

    2015-12-01

    Rough electrodeposition, uncontrolled parasitic side-reactions with electrolytes and dendrite-induced short-circuits have hindered development of advanced energy storage technologies based on metallic lithium, sodium and aluminium electrodes. Solid polymer electrolytes and nanoparticle-polymer composites have shown promise as candidates to suppress lithium dendrite growth, but the challenge of simultaneously maintaining high mechanical strength and high ionic conductivity at room temperature has so far been unmet in these materials. Here we report a facile and scalable method of fabricating tough, freestanding membranes that combine the best attributes of solid polymers, nanocomposites and gel-polymer electrolytes. Hairy nanoparticles are employed as multifunctional nodes for polymer crosslinking, which produces mechanically robust membranes that are exceptionally effective in inhibiting dendrite growth in a lithium metal battery. The membranes are also reported to enable stable cycling of lithium batteries paired with conventional intercalating cathodes. Our findings appear to provide an important step towards room-temperature dendrite-free batteries.

  16. A self-healable and highly stretchable supercapacitor based on a dual crosslinked polyelectrolyte

    PubMed Central

    Huang, Yan; Zhong, Ming; Huang, Yang; Zhu, Minshen; Pei, Zengxia; Wang, Zifeng; Xue, Qi; Xie, Xuming; Zhi, Chunyi

    2015-01-01

    Superior self-healability and stretchability are critical elements for the practical wide-scale adoption of personalized electronics such as portable and wearable energy storage devices. However, the low healing efficiency of self-healable supercapacitors and the small strain of stretchable supercapacitors are fundamentally limited by conventional polyvinyl alcohol-based acidic electrolytes, which are intrinsically neither self-healable nor highly stretchable. Here we report an electrolyte comprising polyacrylic acid dual crosslinked by hydrogen bonding and vinyl hybrid silica nanoparticles, which displays all superior functions and provides a solution to the intrinsic self-healability and high stretchability problems of a supercapacitor. Supercapacitors with this electrolyte are non-autonomic self-healable, retaining the capacitance completely even after 20 cycles of breaking/healing. These supercapacitors are stretched up to 600% strain with enhanced performance using a designed facile electrode fabrication procedure. PMID:26691661

  17. Crosslinked Polyamide

    DOEpatents

    Huang, Zhi H.; McDonald, William F.; Wright, Stacy C.; Taylor, Andrew C.

    2002-06-04

    A crosslinked polyamide material and a process for preparing the crosslinked polyamide material are disclosed. The crosslinked polyamide material comprises a crosslinked chemical combination of (1) a polyamide of the formula: ##STR1## wherein n is between about 50 and 10,000, wherein each R is between 1 and 50 carbon atoms alone and is optionally substituted with heteroatoms, oxygen, nitrogen, sulfur, or phosphorus and combinations thereof, wherein multiple of the R are in vertically aligned spaced relationship along a backbone forming the polyamide, and wherein two or more of the R contain an amino group; and (2) a crosslinking agent containing at least two functional groups capable of reacting with the amino groups of the polyamide. In one embodiment of the invention, the crosslinking agent is an aliphatic or aromatic isocyanate compound having 2 or more --N.dbd.C.dbd.O groups. In another embodiment of the invention, the crosslinking agent is an aliphatic aldehyde or aromatic aldehyde compound having 2 or more --CHO groups. In still another embodiment of the invention, the crosslinking agent is selected from a phosphine having the general formula (A).sub.2 P(B) and mixtures thereof, wherein A is hydroxyalkyl, and B is hydroxyalkyl, alkyl, or aryl. In yet another embodiment of the invention, the crosslinking agent is selected from the group consisting of epoxy resins having more than one epoxide group per molecule.

  18. In situ-forming click-crosslinked gelatin based hydrogels for 3D culture of thymic epithelial cells.

    PubMed

    Truong, Vinh X; Hun, Michael L; Li, Fanyi; Chidgey, Ann P; Forsythe, John S

    2016-07-21

    Hydrogels prepared from naturally derived gelatin can provide a suitable environment for cell attachment and growth, making them favourable materials in tissue engineering. However, physically crosslinked gelatin hydrogels are not stable under physiological conditions while chemical crosslinking of gelatin by radical polymerization may be harmful to cells. In this study, we attached the norbornene functional group to gelatin, which was subsequently crosslinked with a polyethylene glycol (PEG) linker via the nitrile oxide-norbornene click reaction. The rapid crosslinking process allows the hydrogel to be formed within minutes of mixing the polymer solutions under physiological conditions, allowing the gels to be used as injectable materials. The hydrogels properties including mechanical strength, swelling and degradation, can be tuned by changing either the ratio of the reacting groups or the total concentration of the polymer precursors. Murine embryonic fibroblastic cells cultured in soft gels (2 wt% of gelatin and 1 wt% of PEG linker) demonstrated high cell viability as well as similar phenotypic profiles (PDGFRα and MTS15) to Matrigel cultures over 5 days. Thymic epithelial cell and fibroblast co-cultures produced epithelial colonies in these gels following 7 days incubation. These studies demonstrate that gelatin based hydrogels, prepared using "click" crosslinking, provide a robust cell culture platform with retained benefits of the gelatin material, and are therefore suitable for use in various tissue engineering applications. PMID:27217071

  19. Design and preparation of novel polyarylene ether materials based on Diels-Alder reaction as the crosslinker for electrooptical modulators

    NASA Astrophysics Data System (ADS)

    Gao, Wu; Hou, Wenjun; Zhen, Zhen; Liu, Xinhou; Liu, Jialei; Fedorchuk, A. A.; Czaja, P.

    2016-07-01

    Novel crosslinkable organic linear electro-optical (EO) material based on polyarylene ether as the main chain host polymer was designed and prepared. The host polymer with rigid aromatic has demonstrated a good compatibility with the guest chromophore. Long side chain with anthracene ensured the crosslinkable reaction and appropriate glass transition temperature of the host polymer (55 °C). The EO r33 tensor coefficient for this novel EO material has been magnitude of 66 pm/V at 1310 nm and the excellent long term stability at 85 °C. These parameters permit to consider their application in fabrication of organic electro optical devices. The semi-empirical and DFT quantum chemical simulations were performed for 4 principal chromophores to clarify a role of cross-linker in the enhancement of the ground state dipole moments and effective hyperpolarizabilities.

  20. Swelling of radiation crosslinked acrylamide-based microgels and their potential applications

    NASA Astrophysics Data System (ADS)

    Abd El-Rehim, H. A.

    2005-10-01

    Crosslinked polyacrylamide PAAm and acrylamide-Na-acrylate P(AAm-Na-AAc) microgels were prepared by electron beam irradiation. It was found that the dose required for crosslinking depends on the polymer moisture content, so that the dose to obtain PAAm of maximum gel fraction was over 40 and 20 kGy for dry and moist PAAm, respectively. The structural changes in irradiated PAAm were investigated using FTIR and SEM. The swelling property of such microgels in distilled water and real urine solution was determined and crosslinked polymers reached their equilibrium swelling state in a few minutes. As the gel content and crosslinking density decrease, the swelling of the microgels increases. The ability of the microgels to absorb and retain large amount of solutions suggested their possible uses in horticulture and in hygienic products such as disposable diapers.

  1. Positive tone cross-linked resists based on photoacid inhibition of cross linking

    NASA Astrophysics Data System (ADS)

    Lawson, Richard A.; Chun, Jun Sung; Neisser, Mark; Tolbert, Laren M.; Henderson, Clifford L.

    2014-03-01

    A resist imaging design that utilizes photoacid inhibition of cationic polymerization and cross-linking during a postexposure bake step has been studied. The key to the design approach is the use of two different polymerization catalysts/initiators: (1) a photoacid produced from a photoacid generator (PAG) upon exposure of the resist that can result in polymerization and cross-linking of the resist matrix and (2) a thermal cross-linking catalyst (TCC) designed to thermally catalyze epoxide-phenol cross-linking. The TCC can be chosen from a variety of compounds such as triphenylphosphine (TPP) or imidazole. When only one of these catalysts (e.g TPP or photoacid) is present in an epoxide and phenol containing resist matrix, it will individually catalyze cross-linking. When they are present together, they effectively quench one another and little to no cross-linking occurs. This approach can be used to switch the tone of a resist from negative (photoacid catalyzed) to positive (TCC catalyzed and photoacid inhibited). The effect of the ratio of TCC:PAG was examined and the optimal ratio for positive tone behavior was determined. Resist contrast can be modified by optimization of epoxide:phenol ratio in the formulation. Dual tone behavior with positive tone at low dose and negative tone at higher doses can be observed in certain formulation conditions. Initial EUV patterning shows poor results, but the source of the poor imaging is not yet understood.

  2. Physical Cross-Linking Starch-Based Zwitterionic Hydrogel Exhibiting Excellent Biocompatibility, Protein Resistance, and Biodegradability.

    PubMed

    Ye, Lei; Zhang, Yabin; Wang, Qiangsong; Zhou, Xin; Yang, Boguang; Ji, Feng; Dong, Dianyu; Gao, Lina; Cui, Yuanlu; Yao, Fanglian

    2016-06-22

    In this work, a novel starch-based zwitterionic copolymer, starch-graft-poly(sulfobetaine methacrylate) (ST-g-PSBMA), was synthesized via Atom Transfer Radical Polymerization. Starch, which formed the main chain, can be degraded completely in vivo, and the pendent segments of PSBMA endowed the copolymer with excellent protein resistance properties. This ST-g-PSBMA copolymer could self-assemble into a physical hydrogel in normal saline, and studies of the formation mechanism indicated that the generation of the physical hydrogel was driven by electrostatic interactions between PSBMA segments. The obtained hydrogels were subjected to detailed analysis by scanning electron microscopy, swelling ratio, protein resistance, and rheology tests. Toxicity and hemolysis analysis demonstrated that the ST-g-PSBMA hydrogels possess excellent biocompatibility and hemocompatibility. Moreover, the cytokine secretion assays (IL-6, TNF-α, and NO) confirmed that ST-g-PSBMA hydrogels had low potential to trigger the activation of macrophages and were suitable for in vivo biomedical applications. On the basis of these in vitro results, the ST-g-PSBMA hydrogels were implanted in SD rats. The tissue responses to hydrogel implantation and the hydrogel degradation in vivo were determined by histological analysis (Hematoxylin and eosin, Van Gieson, and Masson's Trichrome stains). The results presented in this study demonstrate that the physical cross-linking, starch-based zwitterionic hydrogels possess excellent protein resistance, low macrophage-activation properties, and good biocompatibility, and they are a promising candidate for an in vivo biomedical application platform. PMID:27249052

  3. Investigation of Biological Adhesives and Polyurea Crosslinked Silica-Based Aerogels

    NASA Astrophysics Data System (ADS)

    Lyons, Laura; Cauble, Meagan; Cole, Judith; Sabri, Firouzeh

    2009-11-01

    One of the key steps towards developing new technology for nerve repair is to look at the interaction mechanism and strength of biological components with the material under investigation. The existing technology for peripheral nerve repair relies on suturing techniques for attaching and immobilization of the implant. It is also limited to connecting two nerve components only, through a cylindrical-shaped unit which we will refer to as 1-D. The focus of our work is to develop an aerogel-based printed circuit board (PCB) system for precise guidance of multiple (n-D) neuronal components, simultaneously. Here we report on the adhesion strength of sciatic nerve segments removed from cadaver Sprague Dawley rats and the surface of treated and untreated polyurea cross-linked silica-based aerogels. The adhesion strength of the nerve to the aerogel surface was studied under varying environmental conditions as well as surface coating types. The coatings tested were basement membrane extract (BME), Cell Tak, and the combination. Since the mechanism of adhesion to cells and other surfaces is different and non-competing for BME and Cell Tak it is expected that a stronger adhesion should be accomplished by combining these two adhesives. The effect of temperature, nerve elasticity, and ionic concentration on the strength of adhesion was investigated also and will be reported.

  4. Cyclodextrin/dextran based hydrogels prepared by cross-linking with sodium trimetaphosphate.

    PubMed

    Wintgens, Véronique; Lorthioir, Cédric; Dubot, Pierre; Sébille, Bernard; Amiel, Catherine

    2015-11-01

    Novel βCD-based hydrogels have been synthesized using sodium trimetaphosphate (STMP) as non-toxic reagent. Straightforward mixing of βCD with dextran and STMP in basic aqueous media led to hydrogels incorporating dextran chains, phosphate groups and βCD units. The hydrogels have been characterized by swelling measurements, XPS and (31)P NMR. The swelling ratio was correlated to the content in phosphated groups, which give a polyelectrolyte character to these hydrogels. The significant rise of the swelling ratio with the βCD content increase has been attributed to a decrease of the number of phosphate-based crosslinks, the βCD units playing the role of dangling ends in the tridimensional network. Their loading capacity and their release properties have been investigated for methylene blue and benzophenone in order to demonstrate their potentiality for drug delivery. Through different interaction mechanisms, electrostatic and inclusion complex interactions, these compounds are loaded with different efficiencies. The release involves deswelling, diffusion mechanisms and partition equilibrium. PMID:26256327

  5. Stable Bioactive Enzyme-Containing Multilayer Films Based on Covalent Cross-Linking from Mussel-Inspired Adhesives.

    PubMed

    Longo, Johan; Garnier, Tony; Mateescu, Mihaela; Ponzio, Florian; Schaaf, Pierre; Jierry, Loïc; Ball, Vincent

    2015-11-17

    The use of immobilized enzymes is mandatory for the easy separation of the enzyme, the unreacted substrates, and the obtained products to allow repeated enzymatic assays without cumbersome purification steps. The immobilization procedure is however critical to obtain a high fraction of active enzyme. In this article, we present an enzyme immobilization strategy based on a catechol functionalized alginate. We demonstrate that alkaline phosphatase (ALP) remains active in multilayered films made with alginate modified with catechol moieties (AlgCat) for long duration, that is, up to 7 weeks, provided the multilayered architecture is cross-linked with sodium periodate. This cross-linking reaction allows to create covalent bonds between the amino groups of ALP and the quinone group carried by the modified alginate. In the absence of cross-linking, the enzymatic activity is rapidly lost and this reduction is mainly due to enzyme desorption. We also show that NaIO4 cross-linked (AlgCat-Alp)n films can be freeze-dried and reused at least 3 weeks later without lost in enzymatic activity. PMID:26509712

  6. Fabrication and characterization of cross-linkable hydrogel particles based on hyaluronic acid: potential application in vocal fold regeneration.

    PubMed

    Sahiner, Nurettin; Jha, Amit K; Nguyen, David; Jia, Xinqiao

    2008-01-01

    There is a critical need to engineer hyaluronic acid (HA)-based hydrogels with prolonged in vivo residence time, temporal release of therapeutics and matching viscoelasticity for use in vocal fold tissue engineering. We have previously demonstrated the synthesis and characterization of HA-based soft hydrogel particles (HGP) and particle cross-linked networks as injectable materials to treat vocal fold scarring. In this paper, we report a more versatile technique for preparing cross-linkable HA HGP with reduced sizes. HA HGP were synthesized via chemical cross-linking with divinyl sulfone using a sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/isooctane reverse micelle system in the presence of 1-heptanol. These HGP were rendered cross-linkable by introducing aldehyde groups via sodium periodate oxidation (oxHGP). The presence of aldehyde groups was confirmed by multi-photon confocal microscope upon fluorescence staining using cascade blue hydrazide. The aldehyde groups were used as reactive handles for covalent cross-linking with HA that has been previously modified with adipic acid dihydrazide (HADH). The resulting doubly cross-linked networks (DXN) are highly pliable and do not break until approx. 200-300% strain. The measured elastic modulus of the DXN is around 500 Pa, while the dynamic viscosity decreases linearly with frequency in log- log scale. The mechanical characteristics of DXN are similar to that of vocal fold lamina propria. In vitro cell-proliferation assays showed that the cross-linkable HA HGP did not adversely affect the proliferation of the cultured fibroblasts as assessed by MTT assay. A low-molecular-weight model drug, rhodamine 6G (R6G), was loaded into oxHGP, and its release was monitored using UV-Vis spectroscopy. R6G-loaded oxHGP maintained their ability to form DXN when mixed with the HAADH solution. Approximately 84% of entrapped R6G was liberated from oxHGP at a rate of 0.24%/min in the first 6 h. When encapsulated in the DXN, R6G was

  7. Zygosity determination of multiple pregnancy by deoxyribonucleic acid fingerprints.

    PubMed

    Azuma, C; Kamiura, S; Nobunaga, T; Negoro, T; Saji, F; Tanizawa, O

    1989-03-01

    We used a new method of deoxyribonucleic acid analysis to determine zygosity in multiple pregnancies. This method uses a minisatellite core probe, requires only a small amount of deoxyribonucleic acid, and detects the restriction fragment length polymorphisms that are a result of allelic differences in the number of tandem repeats that contain the core sequence. Southern blot hybridization showed an individual-specific deoxyribonucleic acid fingerprint and each polymorphic band in the sibling could be identified within one (but not both) of the parents. Identical deoxyribonucleic acid fingerprints among the siblings of multiple pregnancy indicate they must be monozygotic. This method is sufficiently reliable and rapid so the determination of zygosity in multiple pregnancy can be made the same day the fetal deoxyribonucleic acid is made available. PMID:2564742

  8. Evaluation of thermal- and photo-crosslinked biodegradable poly(propylene fumarate)-based networks.

    PubMed

    Timmer, Mark D; Ambrose, Catherine G; Mikos, Antonios G

    2003-09-15

    Biodegradable networks of poly(propylene fumarate) (PPF) and the crosslinking reagent poly(propylene fumarate)-diacrylate (PPF-DA) were prepared with thermal- and photo-initiator systems. Thermal-crosslinking was performed with benzoyl peroxide (BP), which is accelerated by N,N-dimethyl-p-toluidine (DMT) and enables injection and in situ polymerization. Photo-crosslinking was accomplished with bis(2,4,6-trimethylbenzoyl) phenylphosphine oxide (BAPO), which is activated by long-wavelength UV light and facilitates material processing with rapid manufacturing techniques, such as stereolithography. Networks were evaluated to assess the effects of the initiators and the PPF/PPF-DA double bond ratio on the mechanical properties. Regardless of the initiator system, the compressive properties of the PPF/PPF-DA networks increased as the double bond ratio decreased from 2 to 0.5. BAPO/UV-initiated networks were significantly stronger than those formed with BP/DMT. The compressive modulus of the photo- and thermal-crosslinked PPF/PPF-DA networks ranged from 310 +/- 25 to 1270 +/- 286 MPa and 75 +/- 8 to 332 +/- 89 MPa, respectively. The corresponding fracture strengths varied from 58 +/- 7 to 129 +/- 17 MPa and 31 +/- 13 to 105 +/- 12 MPa. The mechanical properties were not affected by the initiator concentration. Characterization of the network structures indicated that BAPO was a more efficient initiator for the crosslinking of PPF/PPF-DA, achieving a higher double bond conversion and crosslinking density than its BP counterpart. Estimated average molecular weights between crosslinks (Mc) confirmed the effects of the initiators and PPF/PPF-DA double bond ratio on the mechanical properties. This work demonstrates the capability to control the properties of PPF/PPF-DA networks as well as their versatility to be used as an injectable material or a prefabricated implant. PMID:12926033

  9. A highly reversible room-temperature lithium metal battery based on crosslinked hairy nanoparticles

    PubMed Central

    Choudhury, Snehashis; Mangal, Rahul; Agrawal, Akanksha; Archer, Lynden A.

    2015-01-01

    Rough electrodeposition, uncontrolled parasitic side-reactions with electrolytes and dendrite-induced short-circuits have hindered development of advanced energy storage technologies based on metallic lithium, sodium and aluminium electrodes. Solid polymer electrolytes and nanoparticle-polymer composites have shown promise as candidates to suppress lithium dendrite growth, but the challenge of simultaneously maintaining high mechanical strength and high ionic conductivity at room temperature has so far been unmet in these materials. Here we report a facile and scalable method of fabricating tough, freestanding membranes that combine the best attributes of solid polymers, nanocomposites and gel-polymer electrolytes. Hairy nanoparticles are employed as multifunctional nodes for polymer crosslinking, which produces mechanically robust membranes that are exceptionally effective in inhibiting dendrite growth in a lithium metal battery. The membranes are also reported to enable stable cycling of lithium batteries paired with conventional intercalating cathodes. Our findings appear to provide an important step towards room-temperature dendrite-free batteries. PMID:26634644

  10. A Highly Elastic and Rapidly Crosslinkable Elastin-Like Polypeptide-Based Hydrogel for Biomedical Applications

    PubMed Central

    Zhang, Yi-Nan; Avery, Reginald K.; Vallmajo-Martin, Queralt; Assmann, Alexander; Vegh, Andrea; Memic, Adnan; Olsen, Bradley D.

    2015-01-01

    Elastin-like polypeptides (ELPs) are promising for biomedical applications due to their unique thermoresponsive and elastic properties. ELP-based hydrogels have been produced through chemical and enzymatic crosslinking or photocrosslinking of modified ELPs. Herein, a photocrosslinked ELP gel using only canonical amino acids is presented. The inclusion of thiols from a pair of cysteine residues in the ELP sequence allows disulfide bond formation upon exposure to UV light, leading to the formation of a highly elastic hydrogel. The physical properties of the resulting hydrogel such as mechanical properties and swelling behavior can be easily tuned by controlling ELP concentrations. The biocompatibility of the engineered ELP hydrogels is shown in vitro as well as corroborated in vivo with subcutaneous implantation of hydrogels in rats. ELP constructs demonstrate long-term structural stability in vivo, and early and progressive host integration with no immune response, suggesting their potential for supporting wound repair. Ultimately, functionalized ELPs demonstrate the ability to function as an in vivo hemostatic material over bleeding wounds. PMID:26523134

  11. A highly reversible room-temperature lithium metal battery based on crosslinked hairy nanoparticles.

    PubMed

    Choudhury, Snehashis; Mangal, Rahul; Agrawal, Akanksha; Archer, Lynden A

    2015-01-01

    Rough electrodeposition, uncontrolled parasitic side-reactions with electrolytes and dendrite-induced short-circuits have hindered development of advanced energy storage technologies based on metallic lithium, sodium and aluminium electrodes. Solid polymer electrolytes and nanoparticle-polymer composites have shown promise as candidates to suppress lithium dendrite growth, but the challenge of simultaneously maintaining high mechanical strength and high ionic conductivity at room temperature has so far been unmet in these materials. Here we report a facile and scalable method of fabricating tough, freestanding membranes that combine the best attributes of solid polymers, nanocomposites and gel-polymer electrolytes. Hairy nanoparticles are employed as multifunctional nodes for polymer crosslinking, which produces mechanically robust membranes that are exceptionally effective in inhibiting dendrite growth in a lithium metal battery. The membranes are also reported to enable stable cycling of lithium batteries paired with conventional intercalating cathodes. Our findings appear to provide an important step towards room-temperature dendrite-free batteries. PMID:26634644

  12. Mathematical modeling of cross-linking monomer elution from resin-based dental composites.

    PubMed

    Manojlovic, Dragica; Radisic, Marina; Lausevic, Mila; Zivkovic, Slavoljub; Miletic, Vesna

    2013-01-01

    Elution of potentially toxic substances, including monomers, from resin-based dental composites may affect the biocompatibility of these materials in clinical conditions. In addition to the amounts of eluted monomers, mathematical modeling of elution kinetics reveals composite restorations as potential chronic sources of leachable monomers. The aim of this work was to experimentally quantify elution of main cross-linking monomers from four commercial composites and offer a mathematical model of elution kinetics. Composite samples (n = 7 per group) of Filtek Supreme XT (3M ESPE), Tetric EvoCeram (Ivoclar Vivadent), Admira (Voco), and Filtek Z250 (3M ESPE) were prepared in 2-mm thick Teflon moulds and cured with halogen or light-emitting diode light. Monomer elution in ethanol and water was analyzed using high-performance liquid chromatography up to 28 days postimmersion. The mathematical model was expressed as a sum of two exponential regression functions representing the first-order kinetics law. Elution kinetics in all cases followed the same mathematical model though differences in rate constants as well as the extent of monomer elution were material-, LCU-, medium-dependent. The proposed mechanisms of elution indicate fast elution from surface and subsurface layers and up to 100 times slower monomer extraction from the bulk polymer. PMID:22997145

  13. Characterization of mouse cellular deoxyribonucleic acid homologous to Abelson murine leukemia virus-specific sequences.

    PubMed Central

    Dale, B; Ozanne, B

    1981-01-01

    The genome of Abelson murine leukemia virus (A-MuLV) consists of sequences derived from both BALB/c mouse deoxyribonucleic acid and the genome of Moloney murine leukemia virus. Using deoxyribonucleic acid linear intermediates as a source of retroviral deoxyribonucleic acid, we isolated a recombinant plasmid which contained 1.9 kilobases of the 3.5-kilobase mouse-derived sequences found in A-MuLV (A-MuLV-specific sequences). We used this clone, designated pSA-17, as a probe restriction enzyme and Southern blot analyses to examine the arrangement of homologous sequences in BALB/c deoxyribonucleic acid (endogenous Abelson sequences). The endogenous Abelson sequences within the mouse genome were interrupted by noncoding regions, suggesting that a rearrangement of the cell sequences was required to produce the sequence found in the virus. Endogenous Abelson sequences were arranged similarly in mice that were susceptible to A-MuLV tumors and in mice that were resistant to A-MuLV tumors. An examination of three BALB/c plasmacytomas and a BALB/c early B-cell tumor likewise revealed no alteration in the arrangement of the endogenous Abelson sequences. Homology to pSA-17 was also observed in deoxyribonucleic acids prepared from rat, hamster, chicken, and human cells. An isolate of A-MuLV which encoded a 160,000-dalton transforming protein (P160) contained 700 more base pairs of mouse sequences than the standard A-MuLV isolate, which encoded a 120,000-dalton transforming protein (P120). Images PMID:9279386

  14. Data of thermal degradation and dynamic mechanical properties of starch-glycerol based films with citric acid as crosslinking agent.

    PubMed

    González Seligra, Paula; Medina Jaramillo, Carolina; Famá, Lucía; Goyanes, Silvia

    2016-06-01

    Interest in biodegradable edible films as packaging or coating has increased because their beneficial effects on foods. In particular, food products are highly dependents on thermal stability, integrity and transition process temperatures of the packaging. The present work describes a complete data of the thermal degradation and dynamic mechanical properties of starch-glycerol based films with citric acid (CA) as crosslinking agent described in the article titled: "Biodegradable and non-retrogradable eco-films based on starch-glycerol with citric acid as crosslinking agent" González Seligra et al. (2016) [1]. Data describes thermogravimetric and dynamical mechanical experiences and provides the figures of weight loss and loss tangent of the films as a function of the temperature. PMID:27158645

  15. Data of thermal degradation and dynamic mechanical properties of starch–glycerol based films with citric acid as crosslinking agent

    PubMed Central

    González Seligra, Paula; Medina Jaramillo, Carolina; Famá, Lucía; Goyanes, Silvia

    2016-01-01

    Interest in biodegradable edible films as packaging or coating has increased because their beneficial effects on foods. In particular, food products are highly dependents on thermal stability, integrity and transition process temperatures of the packaging. The present work describes a complete data of the thermal degradation and dynamic mechanical properties of starch–glycerol based films with citric acid (CA) as crosslinking agent described in the article titled: “Biodegradable and non-retrogradable eco-films based on starch–glycerol with citric acid as crosslinking agent” González Seligra et al. (2016) [1]. Data describes thermogravimetric and dynamical mechanical experiences and provides the figures of weight loss and loss tangent of the films as a function of the temperature. PMID:27158645

  16. Antioxidant films based on cross-linked methyl cellulose and native Chilean berry for food packaging applications.

    PubMed

    López de Dicastillo, Carol; Rodríguez, Francisco; Guarda, Abel; Galotto, Maria José

    2016-01-20

    Development of antioxidant and antimicrobial active food packaging materials based on biodegradable polymer and natural plant extracts has numerous advantages as reduction of synthetic additives into the food, reduction of plastic waste, and food protection against microorganisms and oxidation reactions. In this way, active films based on methylcellulose (MC) and maqui (Aristotelia chilensis) berry fruit extract, as a source of antioxidants agents, were studied. On the other hand, due to the high water affinity of MC, this polymer was firstly cross-linked with glutaraldehyde (GA) at different concentrations. The results showed that the addition of GA decreased water solubility, swelling, water vapor permeability of MC films, and the release of antioxidant substances from the active materials increased with the concentration of GA. Natural extract and active cross-linked films were characterized in order to obtain the optimal formulation with the highest antioxidant activity and the best physical properties for latter active food packaging application. PMID:26572446

  17. Electrochemical deoxyribonucleic acid biosensor based on electrodeposited graphene and nickel oxide nanoparticle modified electrode for the detection of salmonella enteritidis gene sequence.

    PubMed

    Sun, Wei; Wang, Xiuli; Lu, Yongxi; Gong, Shixing; Qi, Xiaowei; Lei, Bingxin; Sun, Zhenfan; Li, Guangjiu

    2015-04-01

    In this paper a new electrochemical DNA biosensor was prepared by using graphene (GR) and nickel oxide (NiO) nanocomposite modified carbon ionic liquid electrode (CILE) as the substrate electrode. GR and NiO nanoparticles were electrodeposited on the CILE surface step-by-step to get the nanocomposite. Due to the strong affinity of NiO with phosphate groups of ssDNA, oligonucleotide probe with a terminal 5'-phosphate group could be attached on the surface of NiO/GR/CILE, which could further hybridize with the target ssDNA sequence. Methylene blue (MB) was used as the electrochemical indicator for monitoring the hybridization reaction. Under the optimal conditions the reduction peak current of MB was proportional to the concentration of salmonella enteritidis gene sequence in the range from 1.0×10(-13) to 1.0×10(-6)molL(-1) with a detection limit as 3.12×10(-14)molL(-1). This electrochemical DNA sensor exhibited good discrimination ability to one-base and three-base mismatched ssDNA sequences, and the polymerase chain reaction amplification product of salmonella enteritidis gene sequences were further detected with satisfactory results. PMID:25686924

  18. A novel crosslinking method for improved tear resistance and biocompatibility of tissue based biomaterials.

    PubMed

    Tam, Hobey; Zhang, Will; Feaver, Kristen R; Parchment, Nathaniel; Sacks, Michael S; Vyavahare, Naren

    2015-10-01

    Over 300,000 heart valve replacements are performed annually to replace stenotic and regurgitant heart valves. Bioprosthetic heart valves (BHVs), derived from glutaraldehyde crosslinked (GLUT) porcine aortic valve leaflets or bovine pericardium are often used. However, valve failure can occur within 12-15 years due to calcification and/or progressive degeneration. In this study, we have developed a novel fabrication method that utilizes carbodiimide, neomycin trisulfate, and pentagalloyl glucose crosslinking chemistry (TRI) to better stabilize the extracellular matrix of porcine aortic valve leaflets. We demonstrate that TRI treated leaflets show similar biomechanics to GLUT crosslinked leaflets. TRI treated leaflets had better resistance to enzymatic degradation in vitro and demonstrated better tearing toughness after challenged with enzymatic degradation. When implanted subcutaneously in rats for up to 90 days, GLUT control leaflets calcified heavily while TRI treated leaflets resisted calcification, retained more ECM components, and showed better biocompatibility. PMID:26196535

  19. Electrochemical deoxyribonucleic acid biosensor based on the self-assembly film with nanogold decorated on ionic liquid modified carbon paste electrode.

    PubMed

    Gao, Hongwei; Qi, Xiaowei; Chen, Ying; Sun, Wei

    2011-10-17

    An electrochemical DNA biosensor was fabricated by self-assembling probe single-stranded DNA (ssDNA) with a nanogold decorated on ionic liquid modified carbon paste electrode (IL-CPE). IL-CPE was fabricated using 1-butylpyridinium hexafluorophosphate as the binder and the gold nanoparticles were electrodeposited on the surface of IL-CPE (Au/IL-CPE). Then mercaptoacetic acid was self-assembled on the Au/IL-CPE to obtain a layer of modified film, and the ssDNA probe was further covalently-linked with mercaptoacetic acid by the formation of carboxylate ester with the help of N-(3-dimethylamino-propyl)-N'-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide. The hybridization reaction with the target ssDNA was monitored with methylene blue (MB) as the electrochemical indicator. Under the optimal conditions, differential pulse voltammetric responses of MB was proportional to the specific ssDNA arachis sequences in the concentration range from 1.0×10(-11) to 1.0×10(-6) mol L(-1) with the detection limit as 1.5×10(-12) mol L(-1) (3σ). This electrochemical DNA sensor exhibited good stability and selectivity with the discrimination ability of the one-base and three-base mismatched ssDNA sequences. The polymerase chain reaction product of arachis Arabinose operon D gene was successfully detected by the proposed method, which indicated that the electrochemical DNA sensor designed in this paper could be further used for the detection of specific ssDNA sequence. PMID:21907030

  20. Semiconductor sensor embedded microfluidic chip for protein biomarker detection using a bead-based immunoassay combined with deoxyribonucleic acid strand labeling.

    PubMed

    Lin, Yen-Heng; Peng, Po-Yu

    2015-04-15

    Two major issues need to be addressed in applying semiconductor biosensors to detecting proteins in immunoassays. First, the length of the antibody on the sensor surface surpasses the Debye lengths (approximately 1 nm, in normal ionic strength solution), preventing certain specifically bound proteins from being tightly attached to the sensor surface. Therefore, these proteins do not contribute to the sensor's surface potential change. Second, these proteins carry a small charge and can be easily affected by the pH of the surrounding solution. This study proposes a magnetic bead-based immunoassay using a secondary antibody to label negatively charged DNA fragments for signal amplification. An externally imposed magnetic force attaches the analyte tightly to the sensor surface, thereby effectively solving the problem of the analyte protein's distance to the sensor surface surpassing the Debye lengths. In addition, a normal ion intensity buffer can be used without dilution for the proposed method. Experiments revealed that the sensitivity can be improved by using a longer DNA fragment for labeling and smaller magnetic beads as solid support for the antibody. By using a 90 base pair DNA label, the signal was 15 times greater than that without labeling. In addition, by using a 120 nm magnetic bead, a minimum detection limit of 12.5 ng mL(-1) apolipoprotein A1 can be measured. Furthermore, this study integrates a semiconductor sensor with a microfluidic chip. With the help of microvalves and micromixers in the chip, the length of the mixing step for each immunoassay has been reduced from 1h to 20 min, and the sample volume has been reduced from 80 μL to 10 μL. In practice, a protein biomarker in a urinary bladder cancer patient's urine was successfully measured using this technique. This study provides a convenient and effective method to measure protein using a semiconductor sensor. PMID:25818137

  1. A novel supramolecular polymer gel constructed by crosslinking pillar[5]arene-based supramolecular polymers through metal-ligand interactions.

    PubMed

    Wang, Pi; Xing, Hao; Xia, Danyu; Ji, Xiaofan

    2015-12-21

    A novel heteroditopic A-B monomer was synthesized and used to construct linear supramolecular polymers utilizing pillar[5]arene-based host-guest interactions. Specifically, upon addition of Cu(2+) ions, the supramolecular polymer chains are crosslinked through metal-ligand interactions, resulting in the formation of a supramolecular polymer gel. Interestingly, this self-organized supramolecular polymer can be used as a novel fluorescent sensor for detecting Cu(2+) ions. PMID:26466511

  2. Spectroscopic evaluation of polyurea crosslinked aerogels, as a substitute for RTV-based chromatic calibration targets for spacecraft

    NASA Astrophysics Data System (ADS)

    Sabri, F.; Leventis, N.; Hoskins, J.; Schuerger, A. C.; Sinden-Redding, M.; Britt, D.; Duran, R. A.

    2011-02-01

    Room temperature vulcanizing (RTV)-based components have been used on Mars Pathfinder, the Mars rovers, Spirit and Opportunity, as well as the Phoenix Lander as a support matrix for pigmented panoramic camera calibration targets. RTV 655 has demonstrated superiority to other polymers due to its unique range of material properties namely mechanical stability between -115 and 204 °C and UV radiation tolerance. As a result, it has been the number one choice for many space-related missions. However, due to the high mass density and the natural tendency for electrostatic charging RTV materials have caused complications by attracting and retaining dust particles (Sabri et al., 2008). In the current project we have investigated the relevant properties of polymer-reinforced (crosslinked) silica aerogels with the objective of substituting RTV-based calibration targets with an aerogel based design. The lightweight, mechanical strength, ability to accept color pigments, and extremely low dust capture makes polyurea crosslinked aerogels a strong candidate as a chromatic standard for extraterrestrial missions. For this purpose, the reflection spectra, gravimetric analysis, and low temperature response of metal oxide pigmented, polyurea crosslinked silica aerogels have been investigated and reported here.

  3. Study of the effect of mixing approach on cross-linking efficiency of hyaluronic acid-based hydrogel cross-linked with 1,4-butanediol diglycidyl ether.

    PubMed

    Al-Sibani, Mohammed; Al-Harrasi, Ahmed; Neubert, Reinhard H H

    2016-08-25

    Regardless of various strategies reported for cross-linking hyaluronic acid (HA) with 1,4-butanediol diglycidyl ether (BDDE), seeking new strategies that enhance cross-linking efficiency with a low level of cross-linker is essential. In this work, we studied the influence of mixing approach on two cross-linked BDDE-HA hydrogels prepared by two different mixing approaches; the large-batch mixing approach in which the hydrogel quantities were all mixed as a single lump in one container (hydrogel 1), and the small-batches mixing approach in which the hydrogel quantities were divided into smaller batches, mixed separately at various HA/BDDE ratios then combined in one reaction mixture (hydrogel 2). The result showed that the cross-linking reaction was mixing process-dependent. Degradation tests proved that, in relation to hydrogel 1, hydrogel 2 was more stable, and exhibited a higher resistance towards hyaluronidase activity. The swelling ratio of hydrogel 1 was significantly higher than that of hydrogel 2 in distilled water; however, in phosphate buffer saline, both hydrogels showed no significant difference. SEM images demonstrated that hydrogel 2 composite showed a denser network structure and smaller pore-size than hydrogel 1. In comparison to native HA, the occurrence of chemical modification in the cross-linked hydrogels was confirmed by FTIR and NMR distinctive peaks. These peaks also provided evidence that hydrogel 2 exhibited a higher degree of modification than hydrogel 1. In conclusion, the small-batches mixing approach proved to be more effective than large-batch mixing in promoting HA-HA entanglement and increasing the probability of BDDE molecules for binding with HA chains. PMID:27312477

  4. Homology between the deoxyribonucleic acid of fertility factor P and Vibrio cholerae chromosomal deoxyribonucleic acid.

    PubMed Central

    Wohhieter, J A; Datta, A; Brenner, D J; Baron, L S

    1975-01-01

    The deoxyribonucleic acid (DNA) of the Vibrio cholerae fertility factor P was isolated by the dye-buoyant density method and hybridized to V. cholerae chromosomal DNA. The DNA of this fertility plasmid had between 35 to 40% homology with the V. cholerae chromosomal DNA. Little or no homology was detected between the P factor DNA and DNA of the Escherichia coli sex factor F. PMID:1092651

  5. Biodegradable chitosan-based ambroxol hydrochloride microspheres: effect of cross-linking agents.

    PubMed

    Gangurde, Hh; Chavan, Nv; Mundada, As; Derle, Dv; Tamizharasi, S

    2011-01-01

    The objective of this study was to investigate the influence of type of cross-linking method used on the properties of ambroxol hydrochloride microspheres such as encapsulation efficiency, particle size, and drug release. Microspheres were prepared by solvent evaporation technique using chitosan as a matrix-forming agent and cross-linked using formaldehyde and heat treatment. Morphological and physicochemical properties of microspheres were then investigated by scanning electron microscopy (SEM), X-ray diffractometry (XRD), differential scanning calorimetry (DSC), and Fourier-transform infrared spectroscopy (FTIR) spectroscopy. The cross-linking of chitosan takes place at the free amino group because of formation of imine bond as evidenced by FTIR. The DSC, XRD, and FTIR analysis showed that chitosan microspheres cross linked by heating were superior in properties and performance as compared to the microspheres cross-linked using formaldehyde. SEM results revealed that heat-treated microspheres were spherical, discrete having smooth, and porous structure. The particle size and encapsulation efficiencies of the prepared chitosan microspheres ranged between 10.83-24.11 μm and 39.73μ80.56%, respectively. The drug release was extended up to 12 h, and the kinetics of the drug release was obeying Higuchi kinetic proving diffusion-controlled drug release. PMID:21607049

  6. Biodegradable Chitosan-Based Ambroxol Hydrochloride Microspheres: Effect of Cross-Linking Agents

    PubMed Central

    Gangurde, HH; Chavan, NV; Mundada, AS; Derle, DV; Tamizharasi, S

    2011-01-01

    The objective of this study was to investigate the influence of type of cross-linking method used on the properties of ambroxol hydrochloride microspheres such as encapsulation efficiency, particle size, and drug release. Microspheres were prepared by solvent evaporation technique using chitosan as a matrix-forming agent and cross-linked using formaldehyde and heat treatment. Morphological and physicochemical properties of microspheres were then investigated by scanning electron microscopy (SEM), X-ray diffractometry (XRD), differential scanning calorimetry (DSC), and Fourier-transform infrared spectroscopy (FTIR) spectroscopy. The cross-linking of chitosan takes place at the free amino group because of formation of imine bond as evidenced by FTIR. The DSC, XRD, and FTIR analysis showed that chitosan microspheres cross linked by heating were superior in properties and performance as compared to the microspheres cross-linked using formaldehyde. SEM results revealed that heat-treated microspheres were spherical, discrete having smooth, and porous structure. The particle size and encapsulation efficiencies of the prepared chitosan microspheres ranged between 10.83–24.11 μm and 39.73μ80.56%, respectively. The drug release was extended up to 12 h, and the kinetics of the drug release was obeying Higuchi kinetic proving diffusion-controlled drug release. PMID:21607049

  7. Plasticization and crosslinking effects of acetone-formaldehyde and tannin resins on wheat protein-based natural polymers.

    PubMed

    Zhang, Xiaoqing; Do, My Dieu

    2009-07-01

    Efficient plasticization and sufficient crosslinking were achieved by using an acetone-formaldehyde (AF) resin as an additive in the thermal processing of wheat protein-based natural polymers. The mobile AF resin and its strong intermolecular interactions with a wheat protein matrix produced sufficient flexibility for the plastics, while the covalent bonds formed between AF and the protein chains also caused the water-soluble resin to be retained in the materials under wet conditions. The mechanical properties of the materials were also enhanced as an additional benefit due to the formation of crosslinked networks through the polymer matrix. Tensile strength was further enhanced when using AF in conjunction with tannin resin (AFTR) in the systems as rigid aromatic structures were formed in the crosslinking segments. Different components in wheat proteins (WPs) or wheat gluten (WG) (e.g., proteins, residual starch and lipids) displayed different capabilities in interaction and reaction with the AFTR additives, and thus resulted in different performances when the ratio of these components varied in the materials. The application of the AFTR additives provides a feasible methodology to thermally process wheat protein-based natural polymers with improved mechanical performance and water-resistant properties. PMID:19447383

  8. Divinyl sulfone cross-linked cyclodextrin-based polymeric materials: synthesis and applications as sorbents and encapsulating agents.

    PubMed

    Morales-Sanfrutos, Julia; Lopez-Jaramillo, Francisco Javier; Elremaily, Mahmoud A A; Hernández-Mateo, Fernando; Santoyo-Gonzalez, Francisco

    2015-01-01

    The aim of this study was to evaluate the crosslinking abilities of divinyl sulfone (DVS) for the preparation of novel water-insoluble cyclodextrin-based polymers (CDPs) capable of forming inclusion complexes with different guest molecules. Reaction of DVS with native α-cyclodextrin (α-CD), β-cyclodextrin (β-CD) and/or starch generates a variety of homo- and hetero-CDPs with different degrees of crosslinking as a function of the reactants' stoichiometric ratio. The novel materials were characterized by powder X-ray diffraction, electron microscopy and for their sorption of phenol and 4-nitrophenol. They were further evaluated as sorbents with phenolic pollutants (bisphenol A and β-naphthol) and bioactive compounds (the hormone progesterone and curcumin). Data obtained from the inclusion experiments show that the degree of cross-linking has a minor influence on the yield of inclusion complex formation and highlight the important role of the CDs, supporting a sorption process based on the formation of inclusion complexes. In general, the inclusion processes are better described by a Freundlich isotherm although an important number of them can also be fitted to the Langmuir isotherm with R2 ≥ 0.9, suggesting a sorption onto a monolayer of homogeneous sites. PMID:25706758

  9. Self-Healing and Thermo-Responsive Dual-Crosslinked Alginate Hydrogels based on Supramolecular Inclusion Complexes

    PubMed Central

    Miao, Tianxin; Fenn, Spencer L.; Charron, Patrick N.; Oldinski, Rachael A.

    2015-01-01

    β-cyclodextrin (β-CD), with a lipophilic inner cavity and hydrophilic outer surface, interacts with a large variety of non-polar guest molecules to form non-covalent inclusion complexes. Conjugation of β-CD onto biomacromolecules can form physically-crosslinked hydrogel networks upon mixing with a guest molecule. Herein describes the development and characterization of self-healing, thermo-responsive hydrogels, based on host-guest inclusion complexes between alginate-graft-β-CD and Pluronic® F108 (poly(ethylene glycol)-b-poly(propylene glycol)-b-poly(ethylene glycol)). The mechanics, flow characteristics, and thermal response were contingent on the polymer concentrations, and the host-guest molar ratio. Transient and reversible physical crosslinking between host and guest polymers governed self-assembly, allowing flow under shear stress, and facilitating complete recovery of the material properties within a few seconds of unloading. The mechanical properties of the dual-crosslinked, multi-stimuli responsive hydrogels were tuned as high as 30 kPa at body temperature, and are advantageous for biomedical applications such as drug delivery and cell transplantation. PMID:26509214

  10. Comparison of the Morphology and Deoxyribonucleic Acid Composition of 27 Strains of Nitrifying Bacteria1

    PubMed Central

    Watson, Stanley W.; Mandel, Manley

    1971-01-01

    The gross morphology, fine structure, and per cent guanine plus cytosine (GC) composition of deoxyribonucleic acid of 27 strains of nitrifying bacteria were compared. Based on morphological differences, the ammonia-oxidizing bacteria were separated into four genera. Nitrosomonas species and Nitrosocystis species formed one homogenous group, and Nitrosolobus species and Nitrosospira species formed a second homogenous group in respect to their deoxyribonucleic acid GC compositions. Similarly, the nitrite-oxidizing bacteria were separated into three genera based on their morphology. The members of two of these nitrite-oxidizing genera, Nitrobacter and Nitrococcus, had similar GC compositions, but Nitrospina gracilis had a significantly lower GC composition than the members of the other two genera. Images PMID:4939767

  11. Silicone boronates reversibly crosslink using Lewis acid-Lewis base amine complexes.

    PubMed

    Dodge, Laura; Chen, Yunqing; Brook, Michael A

    2014-07-21

    Silicone elastomers are normally thermosets, which are not readily recycled or repurposed. The few examples of thermoplastic silicone elastomers depend on reversible covalent and non-covalent molecular interactions. It is demonstrated that amine-boronate complex formation provides a simple and flexible route to reversible crosslinked silicones. A variety of network structures were prepared by use of terminal and pendantly functionalised silicone boronates and amines. The crosslink density was quantified using a combination of Shore-hardness measurements, swelling, and rheological analyses. Stress induced by compressive force could be relieved through dynamic B-N bond reformation at 60 °C. Materials could be fully disassembled through introduction of n-butylamine and successfully reformed upon removal of the monofunctional amine by evaporation. PMID:24986574

  12. Integrated Workflow for Structural Proteomics Studies Based on Cross-Linking/Mass Spectrometry with an MS/MS Cleavable Cross-Linker.

    PubMed

    Arlt, Christian; Götze, Michael; Ihling, Christian H; Hage, Christoph; Schäfer, Mathias; Sinz, Andrea

    2016-08-16

    Cross-linking combined with mass spectrometry (MS) has evolved as an alternative strategy in structural biology for characterizing three-dimensional structures of protein assemblies and for mapping protein-protein interactions. Here, we describe an integrated workflow for an automated identification of cross-linked products that is based on the use of a tandem mass spectrometry (MS/MS) cleavable cross-linker (containing a 1,3-bis-(4-oxo-butyl)-urea group, BuUrBu) generating characteristic doublet patterns upon fragmentation. We evaluate different fragmentation methods available on an Orbitrap Fusion mass spectrometer for three proteins and an E. coli cell lysate. An updated version of the dedicated software tool MeroX was employed for a fully automated identification of cross-links. The strength of our cleavable cross-linker is that characteristic patterns of the cross-linker as well as backbone fragments of the connected peptides are already observed at the MS/MS level, eliminating the need for conducting MS(3) or sequential CID (collision-induced dissociation)- and ETD (electron transfer dissociation)-MS/MS experiments. This makes our strategy applicable to a broad range of mass spectrometers with MS/MS capabilities. For purified proteins and protein complexes, our workflow using CID-MS/MS acquisition performs with high confidence, scoring cross-links at 0.5% false discovery rate (FDR). The cross-links provide structural insights into the intrinsically disordered tetrameric tumor suppressor protein p53. As a time-consuming manual inspection of cross-linking data is not required, our workflow will pave the way for making the cross-linking/MS approach a routine technique for structural proteomics studies. PMID:27428000

  13. Fragmentation behavior of a thiourea-based reagent for protein structure analysis by collision-induced dissociative chemical cross-linking.

    PubMed

    Müller, Mathias Q; Dreiocker, Frank; Ihling, Christian H; Schäfer, Mathias; Sinz, Andrea

    2010-08-01

    The fragmentation behavior of a novel thiourea-based cross-linker molecule specifically designed for collision-induced dissociation (CID) MS/MS experiments is described. The development of this cross-linker is part of our ongoing efforts to synthesize novel reagents, which create either characteristic fragment ions or indicative constant neutral losses (CNLs) during tandem mass spectrometry allowing a selective and sensitive analysis of cross-linked products. The new derivatizing reagent for chemical cross-linking solely contains a thiourea moiety that is flanked by two amine-reactive N-hydroxy succinimide (NHS) ester moieties for reaction with lysines or free N-termini in proteins. The new reagent offers simple synthetic access and easy structural variation of either length or functionalities at both ends. The thiourea moiety exhibits specifically tailored CID fragmentation capabilities--a characteristic CNL of 85 u--ensuring a reliable detection of derivatized peptides by both electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) tandem mass spectrometry and as such possesses a versatile applicability for chemical cross-linking studies. A detailed examination of the CID behavior of the presented thiourea-based reagent reveals that slight structural variations of the reagent will be necessary to ensure its comprehensive and efficient application for chemical cross-linking of proteins. PMID:20607845

  14. Fabrication and properties of magnetorheological elastomers based on CR/ENR self-crosslinking blends

    NASA Astrophysics Data System (ADS)

    Wang, Yonghong; Zhang, Xinru; Oh, Jaeeung; Chung, Kyungho

    2015-09-01

    Magnetorheological elastomers (MREs) are intelligent materials, which are widely used as dampers to eliminate vibration. In this study, a new kind of MREs was designed using carbonyl iron particles (CIPs), carbon black (CB) and self-crosslinking blends, which were fabricated by reacting polychloroprene rubber with epoxidized natural rubber (CR/ENR blends). The interaction mechanism among CIPs, CB and a matrix in the fabrication process was discussed in detail. The morphology of isotropic MREs (i-MREs) and anisotropic MREs (a-MREs) was observed by scanning electron microscopy (SEM). The effect of CIP volume content on the mechanical properties of MREs was investigated. The effect of CIP volume content on the shear storage modulus, MR effect and loss factor was studied using a modified dynamic mechanical analyzer (DMA). The results revealed that the chain-like distribution of CIPs became more pronounced with increasing CIP content in a-MREs, whereas CIPs distributed uniformly in i-MREs. CIPs and CB bonded well with the rubber matrix as a result of their surface attraction effect to CR and ENR molecular chains. Therefore, MREs had excellent mechanical properties. The promoting effect of CB and CIPs on the self-crosslinking reaction was verified by crosslink density assessment. The shear storage modulus of MREs increased with the increase of CIP content, and the MR effect of i-MREs remarkably increased, while a-MREs decreased due to the obvious increase in initial storage modulus with increasing CIP content. The loss factor of MREs decreased obviously with the increase of CIP content.

  15. PEG-Based Hydrogels with Collagen Mimetic Peptide-Mediated and Tunable Physical Crosslinks

    PubMed Central

    Stahl, Patrick J.; Romano, Nicole H.; Wirtz, Denis; Yu, S. Michael

    2010-01-01

    Mechanical properties of tissue scaffolds have major effects on the morphology and differentiation of cells. In contrast to two-dimensional substrates, local biochemical and mechanical properties of three-dimensional hydrogels are difficult to control due to the geometrical confinement. We designed synthetic 3D hydrogels featuring complexes of four-arm poly(ethylene glycol) (PEG) and collagen mimetic peptides (CMPs) that form hydrogels via physical crosslinks mediated by thermally reversible triple helical assembly of CMPs. Here we present the fabrication of various PEG-CMP 3D hydrogels and their local mechanical properties determined by particle tracking microrheology. Results show that CMP mediated physical crosslinks can be disrupted by altering the temperature of the gel or by adding free CMPs that compete for triple helix formation. This allowed modulation of both bulk and local stiffness as well as the creation of stiffness gradients within the PEG-CMP hydrogel, which demonstrates its potential as a novel scaffold for encoding physico-chemical signals for tissue formation. PMID:20715762

  16. Stable biocompatible cross-linked fluorescent polymeric nanoparticles based on AIE dye and itaconic anhydride.

    PubMed

    Li, Haiyin; Zhang, Xiqi; Zhang, Xiaoyong; Yang, Bin; Wei, Yen

    2014-09-01

    Self-assembly of polymeric materials to form nanoparticles is a particularly promising strategy for various biomedical applications, however, these self-assembling systems often encounter the critical micelle concentration (CMC) issue, as the nanoparticles is usually unstable at low concentration. Therefore, stable cross-linked fluorescent polymeric nanoparticles (FPNs) were covalently constructed from an aggregation induced emission (AIE) dye, itaconic anhydride, poly(ethylene glycol) monomethyl ether methacylate and polyethylenimine. These obtained PhE-ITA-20%(80%) FPNs were fully characterized by a series of techniques including (1)H NMR spectra, UV-vis absorption spectra, fluorescence spectra, FT-IR spectra, transmission electron microscopy, gel permeation chromatography, and dynamic light scattering. Such FPNs emitted intense fluorescence due to the introduction of aggregation induced emission dye. More importantly, the FPNs were found extremely stable in physiological solution even below the CMC owing to their cross-linked architectures. Biocompatibility evaluation and cell uptake behavior of the FPNs were further investigated to explore their potential biomedical applications, the demonstrated excellent biocompatibility made them promising for cell imaging. PMID:24973146

  17. A simple and high-resolution stereolithography-based 3D bioprinting system using visible light crosslinkable bioinks.

    PubMed

    Wang, Zongjie; Abdulla, Raafa; Parker, Benjamin; Samanipour, Roya; Ghosh, Sanjoy; Kim, Keekyoung

    2015-01-01

    Bioprinting is a rapidly developing technique for biofabrication. Because of its high resolution and the ability to print living cells, bioprinting has been widely used in artificial tissue and organ generation as well as microscale living cell deposition. In this paper, we present a low-cost stereolithography-based bioprinting system that uses visible light crosslinkable bioinks. This low-cost stereolithography system was built around a commercial projector with a simple water filter to prevent harmful infrared radiation from the projector. The visible light crosslinking was achieved by using a mixture of polyethylene glycol diacrylate (PEGDA) and gelatin methacrylate (GelMA) hydrogel with eosin Y based photoinitiator. Three different concentrations of hydrogel mixtures (10% PEG, 5% PEG + 5% GelMA, and 2.5% PEG + 7.5% GelMA, all w/v) were studied with the presented systems. The mechanical properties and microstructure of the developed bioink were measured and discussed in detail. Several cell-free hydrogel patterns were generated to demonstrate the resolution of the solution. Experimental results with NIH 3T3 fibroblast cells show that this system can produce a highly vertical 3D structure with 50 μm resolution and 85% cell viability for at least five days. The developed system provides a low-cost visible light stereolithography solution and has the potential to be widely used in tissue engineering and bioengineering for microscale cell patterning. PMID:26696527

  18. Non-Enzymatic Glucose Sensor Based on 3D Graphene Oxide Hydrogel Crosslinked by Various Diamines.

    PubMed

    Hoa, Le Thuy; Hur, Seung Hyun

    2015-11-01

    The non-enzymatic glucose sensor was fabricated by well-controlled and chemically crosslinked graphene oxide hydrogels (GOHs). By using various diamines such as ethylenediamine (EDA), p-phenylene diamine (pPDA) and o-phenylene diamine (oPDA) that have different amine to amine distance, we can control the structures of GOHs such as surface area and pore volume. The pPDA-GOH fabricated by pPDA exhibited the largest surface area and pore volume due to its longest amine to amine distance, which resulted in highest sensitivity in glucose and other monosaccharide sensing such as fructose (C6H12O6), galactose (C6H12O6) and sucrose (C12H22O11). It also showed fast and wide range glucose sensing ability in the amperometric test, and an excellent selectivity toward other interference species such as an Ascorbic acid. PMID:26726578

  19. Novel semi-IPN based on crosslinked carboxymethyl starch and clay for the in vitro release of theophylline.

    PubMed

    Anirudhan, T S; Parvathy, J

    2014-06-01

    A novel semi-interpenetrating polymer network (IPN) based on crosslinked carboxymethyl starch (CL-CMS) and montmorillonite (MMT) was prepared, where carboxymethylation occurs as a result of the reaction between native starch and monochloroacetic acid in isopropanol/water medium at 60°C. The carboxymethyl starch is further crosslinked and made into a semi-IPN with MMT for the release of theophylline. The drug carrier was characterized using FTIR, XRD and surface analysis using SEM. Studies including physio-chemical analysis, swelling behavior, encapsulation efficiency, effect of MMT content, effect of ionic strength and in vitro drug release were carried out. Theophylline encapsulation of up to 74% was achieved and drug release was monitored in SGF (pH 1.2) and SIF (pH 7.4). Results show that the matrix releases drug at a much faster rate in the basic medium than in the acidic medium, thereby holding the promise of developing the semi-IPN system as a potential candidate for the release of theophylline. PMID:24685463

  20. Thermoresponsive, in situ crosslinkable hydrogels based on N-isopropylacrylamide: Fabrication, characterization and mesenchymal stem cell encapsulation

    PubMed Central

    Klouda, Leda; Perkins, Kevin R.; Watson, Brendan M.; Hacker, Michael C.; Bryant, Stephanie J.; Raphael, Robert M.; Kasper, F. Kurtis; Mikos, Antonios G.

    2011-01-01

    Hydrogels that solidify in response to a dual, physical and chemical, mechanism upon temperature increase were fabricated and characterized. The hydrogels were based on N-isopropylacrylamide, which renders them thermoresponsive, and contained covalently crosslinkable moieties in the macromers. The effects of the macromer end group, namely acrylate or methacrylate, and the fabrication conditions were investigated on the degradative and swelling properties of the hydrogels. The hydrogels exhibited higher swelling below their lower critical solution temperature (LCST). When immersed in cell culture media at physiological temperature, which was above their LCST, hydrogels showed constant swelling and no degradation over eight weeks, with methacrylated hydrogels having higher swelling than their acrylated analogs. In addition, hydrogels immersed in cell culture media under the same conditions showed lower swelling as compared to phosphate buffered saline. The interplay between chemical crosslinking and thermally induced phase separation affected the swelling characteristics of hydrogels in different media. Mesenchymal stem cells encapsulated in the hydrogels in vitro were viable over three weeks and markers of osteogenic differentiation were detected when the cells were cultured with osteogenic supplements. Hydrogel mineralization in the absence of cells was observed in cell culture medium with the addition of fetal bovine serum and β-glycerol phosphate. The results suggest that these hydrogels may be suitable as carriers for cell delivery in tissue engineering. PMID:21187170

  1. The interplay of ion crosslinking, free ion content, and polymer mobility in PEO-based single-ion conductors

    NASA Astrophysics Data System (ADS)

    Lin, Kan-Ju; Maranas, Janna

    2010-03-01

    We use molecular dynamics simulation to study ion clustering and dynamics in ion containing polymers. This PEO based single-ion conducting ionomer serves as a model system for understanding cation transport in solid state polymer electrolytes (SPEs). Although small-angle x-ray scattering does not show an ionomer peak, we observer various cation-anion complexes in the simulation, suggesting ionomer backbones are crosslinked through ion complexes. These crosslinks reduce the adjacent PEO mobility resulting in a symmetric mobility gradient along the PEO chain. We vary the cation-anion interaction in the simulation to observe the interplay of cation-anion association, polymer mobility and cation motion. Cation-anion association controls the number of free ions, which is important in ionic conductivity when these materials are used as SPEs. Polymer mobility controls how fast the free ions are able to move through the SPE. High conductivity requires both a high free ion content and fast polymer motion. To understand the connection between the two, we ``tune'' the force field in order to manipulate the free ion content and observe the influence on PEO dynamics.

  2. Fluorometric Determination of Deoxyribonucleic Acid in Bacteria with Ethidium Bromide

    PubMed Central

    Donkersloot, J. A.; Robrish, S. A.; Krichevsky, M. I.

    1972-01-01

    A simple, sensitive, and rapid method is presented for the determination of deoxyribonucleic acid (DNA) in both gram-positive and gram-negative bacteria. It is based upon the fluorometric determination of DNA with ethidium bromide after alkaline digestion of the bacteria to hydrolyze the interfering ribonucleic acid. The assay takes less than 2 hr. Its sensitivity is at least 0.2 μg of DNA in a final solution of 4 ml and it uses commonly available filter or double monochromator fluorometers. Judicious choice of light source and filters allows an additional 10-fold increase in sensitivity with a filter fluorometer. Turbidity caused by bacteria or insoluble polysaccharides does not interfere with the fluorescence measurements. There was no significant difference between the results obtained with this method and those obtained with the indole and diphenylamine methods when these assays were applied to Escherichia coli and sucrose- or glucose-grown Streptococcus mutans. The method was also tested by determining the specific growth rate of E. coli. This new procedure should be especially useful for the determination of bacterial DNA in dilute suspensions and for the estimation of bacterial growth or DNA replication where more conventional methods are not applicable or sensitive enough. PMID:4561101

  3. Short deoxyribonucleic acid repair patch length in Escherichia coli is determined by the processive mechanism of deoxyribonucleic acid polymerase I.

    PubMed Central

    Matson, S W; Bambara, R A

    1981-01-01

    The lengths of ultraviolet irradiation-induced repair resynthesis patches were measured in repair-competent extracts of Escherichia coli. Extracts containing wild-type deoxyribonucleic acid (DNA) polymerase I introduced a patch 15 to 20 nucleotides in length during repair of ColE1 plasmid DNA; extracts containing the polA5 mutant form of DNA polymerase I introduced a patch only about 5 nucleotides in length in a similar reaction. The repair patch length in the presence of either DNA polymerase corresponded to the processivity of that polymerase (the average number of nucleotides added per enzyme-DNA binding event) as determined with purified enzymes and DNA treated with a nonspecific endonuclease. The base composition of the repair patch inserted by the wild-type DNA polymerase was similar to that of the bacterial genome, whereas the patch inserted by the mutant enzyme was skewed toward greater pyrimidine incorporation. This skewing is expected, considering the predominance of pyrimidine incorporation occurring at the ultraviolet lesion and the short patch made by the mutant enzyme. Since the defect in the polA5 DNA polymerase which causes premature dissociation from DNA is reflected exactly in the repair patch length, the processive mechanism of the polymerase must be a central determinant of patch length. PMID:7012116

  4. High internal quantum efficiency in fullerene solar cells based on crosslinked polymer donor networks

    PubMed Central

    Liu, Bo; Png, Rui-Qi; Zhao, Li-Hong; Chua, Lay-Lay; Friend, Richard H.; Ho, Peter K.H.

    2012-01-01

    The power conversion efficiency of organic photovoltaic cells depends crucially on the morphology of their donor–acceptor heterostructure. Although tremendous progress has been made to develop new materials that better cover the solar spectrum, this heterostructure is still formed by a primitive spontaneous demixing that is rather sensitive to processing and hence difficult to realize consistently over large areas. Here we report that the desired interpenetrating heterostructure with built-in phase contiguity can be fabricated by acceptor doping into a lightly crosslinked polymer donor network. The resultant nanotemplated network is highly reproducible and resilient to phase coarsening. For the regioregular poly(3-hexylthiophene):phenyl-C61-butyrate methyl ester donor–acceptor model system, we obtained 20% improvement in power conversion efficiency over conventional demixed biblend devices. We reached very high internal quantum efficiencies of up to 0.9 electron per photon at zero bias, over an unprecedentedly wide composition space. Detailed analysis of the power conversion, power absorbed and internal quantum efficiency landscapes reveals the separate contributions of optical interference and donor–acceptor morphology effects. PMID:23271655

  5. Antimicrobial Properties of Microparticles Based on Carmellose Cross-Linked by Cu2+ Ions

    PubMed Central

    Kejdušová, Martina; Vysloužil, Jakub; Kubová, Kateřina; Celer, Vladimír; Krásna, Magdaléna; Pechová, Alena; Vyskočilová, Věra; Košťál, Vratislav

    2015-01-01

    Carmellose (CMC) is frequently used due to its high biocompatibility, biodegradability, and low immunogenicity for development of site-specific or controlled release drug delivery systems. In this experimental work, CMC dispersions in two different concentrations (1% and 2%) cross-linked by copper (II) ions (0.5, 1, 1.5, or 2.0 M CuCl2) were used to prepare microspheres with antimicrobial activity against Escherichia coli and Candida albicans, both frequently occurring pathogens which cause vaginal infections. The microparticles were prepared by an ionotropic gelation technique which offers the unique possibility to entrap divalent copper ions in a CMC structure and thus ensure their antibacterial activity. Prepared CMC microspheres exhibited sufficient sphericity. Both equivalent diameter and copper content were influenced by CMC concentration, and the molarity of copper (II) solution affected only the copper content results. Selected samples exhibited stable but pH-responsive behaviour in environments which corresponded with natural (pH 4.5) and inflamed (pH 6.0) vaginal conditions. All the tested samples exhibited proven substantial antimicrobial activity against both Gram-negative bacteria Escherichia coli and yeast Candida albicans. Unexpectedly, a crucial parameter for microsphere antimicrobial activity was not found in the copper content but in the swelling capacity of the microparticles and in the degree of CMC surface shrinking. PMID:26090444

  6. Smart nanocomposite hydrogels based on azo crosslinked graphene oxide for oral colon-specific drug delivery

    NASA Astrophysics Data System (ADS)

    Hou, Lin; Shi, Yuyang; Jiang, Guixiang; Liu, Wei; Han, Huili; Feng, Qianhua; Ren, Junxiao; Yuan, Yujie; Wang, Yongchao; Shi, Jinjin; Zhang, Zhenzhong

    2016-08-01

    A safe and efficient nanocomposite hydrogel for colon cancer drug delivery was synthesized using pH-sensitive and biocompatible graphene oxide (GO) containing azoaromatic crosslinks as well as poly (vinyl alcohol) (PVA) (GO–N=N–GO/PVA composite hydrogels). Curcumin (CUR), an anti-cancer drug, was encapsulated successfully into the hydrogel through a freezing and thawing process. Fourier transform infrared spectroscopy, scanning electron microscopy and Raman spectroscopy were performed to confirm the formation and morphological properties of the nanocomposite hydrogel. The hydrogels exhibited good swelling properties in a pH-sensitive manner. Drug release studies under conditions mimicking stomach to colon transit have shown that the drug was protected from being released completely into the physiological environment of the stomach and small intestine. In vivo imaging analysis, pharmacokinetics and a distribution of the gastrointestinal tract experiment were systematically studied and evaluated as colon-specific drug delivery systems. All the results demonstrated that GO–N=N–GO/PVA composite hydrogels could protect CUR well while passing through the stomach and small intestine to the proximal colon, and enhance the colon-targeting ability and residence time in the colon site. Therefore, CUR loaded GO–N=N–GO/PVA composite hydrogels might potentially provide a theoretical basis for the treatment of colon cancer with high efficiency and low toxicity.

  7. Polymer electrolyte based on crosslinked poly(glycidyl methacrylate) and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide

    NASA Astrophysics Data System (ADS)

    Fei, Beatrice Wong Chui; Hanifah, Sharina Abu; Ahmad, Azizan; Hassan, Nur Hasyareeda

    2015-09-01

    Polymer electrolytes based on crosslinked poly(glycidyl methacrylate) as polymer host and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BmimTFSI) as incorporated salt were prepared by in-situ photopolymerization technique. The complexes with different mass ratio of glycidyl methacrylate (GMA) monomer to BmimTFSI were investigated. The ionic conductivity of the polymer electrolyte was increased and reach the highest value of 7.50 × 10-4 S cm-1 at the ratio of 3:7 (GMA: BmimTFSI). The interaction between the polymer host and ionic liquid was proved by Attenuated Total Reflectance-Fourier Transformation Infra-Red Spectroscopy (ATR-FTIR). Meanwhile, the X-ray diffraction analysis shows the amorphousity of the polymer electrolyte film increase with the ionic liquid ratio.

  8. Polymer electrolyte based on crosslinked poly(glycidyl methacrylate) and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide

    SciTech Connect

    Fei, Beatrice Wong Chui; Hanifah, Sharina Abu; Ahmad, Azizan; Hassan, Nur Hasyareeda

    2015-09-25

    Polymer electrolytes based on crosslinked poly(glycidyl methacrylate) as polymer host and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BmimTFSI) as incorporated salt were prepared by in-situ photopolymerization technique. The complexes with different mass ratio of glycidyl methacrylate (GMA) monomer to BmimTFSI were investigated. The ionic conductivity of the polymer electrolyte was increased and reach the highest value of 7.50 × 10{sup −4} S cm{sup −1} at the ratio of 3:7 (GMA: BmimTFSI). The interaction between the polymer host and ionic liquid was proved by Attenuated Total Reflectance-Fourier Transformation Infra-Red Spectroscopy (ATR-FTIR). Meanwhile, the X-ray diffraction analysis shows the amorphousity of the polymer electrolyte film increase with the ionic liquid ratio.

  9. Surface Charges and Shell Crosslinks Each Play Significant Roles in Mediating Degradation, Biofouling, Cytotoxicity and Immunotoxicity for Polyphosphoester-based Nanoparticles

    NASA Astrophysics Data System (ADS)

    Elsabahy, Mahmoud; Zhang, Shiyi; Zhang, Fuwu; Deng, Zhou J.; Lim, Young H.; Wang, Hai; Parsamian, Perouza; Hammond, Paula T.; Wooley, Karen L.

    2013-11-01

    The construction of nanostructures from biodegradable precursors and shell/core crosslinking have been pursued as strategies to solve the problems of toxicity and limited stability, respectively. Polyphosphoester (PPE)-based micelles and crosslinked nanoparticles with non-ionic, anionic, cationic, and zwitterionic surface characteristics for potential packaging and delivery of therapeutic and diagnostic agents, were constructed using a quick and efficient synthetic strategy, and importantly, demonstrated remarkable differences in terms of cytotoxicity, immunotoxicity, and biofouling properties, as a function of their surface characteristics and also with dependence on crosslinking throughout the shell layers. For instance, crosslinking of zwitterionic micelles significantly reduced the immunotoxicity, as evidenced from the absence of secretions of any of the 23 measured cytokines from RAW 264.7 mouse macrophages treated with the nanoparticles. The micelles and their crosslinked analogs demonstrated lower cytotoxicity than several commercially-available vehicles, and their degradation products were not cytotoxic to cells at the range of the tested concentrations. PPE-nanoparticles are expected to have broad implications in clinical nanomedicine as alternative vehicles to those involved in several of the currently available medications.

  10. Surface Charges and Shell Crosslinks Each Play Significant Roles in Mediating Degradation, Biofouling, Cytotoxicity and Immunotoxicity for Polyphosphoester-based Nanoparticles

    PubMed Central

    Elsabahy, Mahmoud; Zhang, Shiyi; Zhang, Fuwu; Deng, Zhou J.; Lim, Young H.; Wang, Hai; Parsamian, Perouza; Hammond, Paula T.; Wooley, Karen L.

    2013-01-01

    The construction of nanostructures from biodegradable precursors and shell/core crosslinking have been pursued as strategies to solve the problems of toxicity and limited stability, respectively. Polyphosphoester (PPE)-based micelles and crosslinked nanoparticles with non-ionic, anionic, cationic, and zwitterionic surface characteristics for potential packaging and delivery of therapeutic and diagnostic agents, were constructed using a quick and efficient synthetic strategy, and importantly, demonstrated remarkable differences in terms of cytotoxicity, immunotoxicity, and biofouling properties, as a function of their surface characteristics and also with dependence on crosslinking throughout the shell layers. For instance, crosslinking of zwitterionic micelles significantly reduced the immunotoxicity, as evidenced from the absence of secretions of any of the 23 measured cytokines from RAW 264.7 mouse macrophages treated with the nanoparticles. The micelles and their crosslinked analogs demonstrated lower cytotoxicity than several commercially-available vehicles, and their degradation products were not cytotoxic to cells at the range of the tested concentrations. PPE-nanoparticles are expected to have broad implications in clinical nanomedicine as alternative vehicles to those involved in several of the currently available medications. PMID:24264796

  11. Recycling and processing of several typical crosslinked polymer scraps with enhanced mechanical properties based on solid-state mechanochemical milling

    NASA Astrophysics Data System (ADS)

    Lu, Canhui; Zhang, Xinxing; Zhang, Wei

    2015-05-01

    The partially devulcanization or de-crosslinking of ground tire rubber (GTR), post-vulcanized fluororubber scraps and crosslinked polyethylene from cable scraps through high-shear mechanochemical milling (HSMM) was conducted by a modified solid-state mechanochemical reactor. The results indicated that the HSMM treated crosslinked polymer scraps can be reprocessed as virgin rubbers or thermoplastics to produce materials with high performance. The foamed composites of low density polyethylene/GTR and the blend of post-vulcanized flurorubber (FKM) with polyacrylate rubber (ACM) with better processability and mechanical properties were obtained. The morphology observation showed that the dispersion and compatibility between de-crosslinked polymer scraps and matrix were enhanced. The results demonstrated that HSMM is a feasible alternative technology for recycling post-vulcanized or crosslinked polymer scraps.

  12. Recycling and processing of several typical crosslinked polymer scraps with enhanced mechanical properties based on solid-state mechanochemical milling

    SciTech Connect

    Lu, Canhui; Zhang, Xinxing; Zhang, Wei

    2015-05-22

    The partially devulcanization or de-crosslinking of ground tire rubber (GTR), post-vulcanized fluororubber scraps and crosslinked polyethylene from cable scraps through high-shear mechanochemical milling (HSMM) was conducted by a modified solid-state mechanochemical reactor. The results indicated that the HSMM treated crosslinked polymer scraps can be reprocessed as virgin rubbers or thermoplastics to produce materials with high performance. The foamed composites of low density polyethylene/GTR and the blend of post-vulcanized flurorubber (FKM) with polyacrylate rubber (ACM) with better processability and mechanical properties were obtained. The morphology observation showed that the dispersion and compatibility between de-crosslinked polymer scraps and matrix were enhanced. The results demonstrated that HSMM is a feasible alternative technology for recycling post-vulcanized or crosslinked polymer scraps.

  13. Constitutive Modeling of Crosslinked Nanotube Materials

    NASA Technical Reports Server (NTRS)

    Odegard, G. M.; Frankland, S. J. V.; Herzog, M. N.; Gates, T. S.; Fay, C. C.

    2004-01-01

    A non-linear, continuum-based constitutive model is developed for carbon nanotube materials in which bundles of aligned carbon nanotubes have varying amounts of crosslinks between the nanotubes. The model accounts for the non-linear elastic constitutive behavior of the material in terms of strain, and is developed using a thermodynamic energy approach. The model is used to examine the effect of the crosslinking on the overall mechanical properties of variations of the crosslinked carbon nanotube material with varying degrees of crosslinking. It is shown that the presence of the crosslinks has significant effects on the mechanical properties of the carbon nanotube materials. An increase in the transverse shear properties is observed when the nanotubes are crosslinked. However, this increase is accompanied by a decrease in axial mechanical properties of the nanotube material upon crosslinking.

  14. Nondestructive fluorescence-based quantification of threose-induced collagen cross-linking in bovine articular cartilage

    NASA Astrophysics Data System (ADS)

    Kinnunen, Jussi; Kokkonen, Harri T.; Kovanen, Vuokko; Hauta-Kasari, Markku; Vahimaa, Pasi; Lammi, Mikko J.; Töyräs, Juha; Jurvelin, Jukka S.

    2012-09-01

    Extensive collagen cross-linking affects the mechanical competence of articular cartilage: it can make the cartilage stiffer and more brittle. The concentrations of the best known cross-links, pyridinoline and pentosidine, can be accurately determined by destructive high-performance liquid chromatography (HPLC). We explore a nondestructive evaluation of cross-linking by using the intrinsic fluorescence of the intact cartilage. Articular cartilage samples from bovine knee joints were incubated in threose solution for 40 and 100 h to increase the collagen cross-linking. Control samples without threose were also prepared. Excitation-emission matrices at wavelengths of 220 to 950 nm were acquired from the samples, and the pentosidine and pyridinoline cross-links and the collagen concentrations were determined using HPLC. After the threose treatment, pentosidine and lysyl pyridinole (LP) concentrations increased. The intrinsic fluorescence, excited below 350 nm, decreased and was related to pentosidine [r=-0.90, 240/325 nm (excitation/emission)] or LP (r=-0.85, 235/285 nm) concentrations. Due to overlapping, the changes in emission could not be linked specifically to the recorded cross-links. However, the fluorescence signal enabled a nondestructive optical estimate of changes in the pentosidine and LP cross-linking of intact articular cartilage.

  15. Influence of surfactant on dynamics of photoinduced motions in a dye-doped deoxyribonucleic acid

    NASA Astrophysics Data System (ADS)

    Mysliwiec, Jaroslaw; Parafiniuk, Kacper; Miniewicz, Andrzej; Rau, Ileana; Kajzar, Francois; Niziol, Jacek; Hebda, Edyta; Pielichowski, Jan; Sahraoui, Bouchta

    2012-10-01

    Pure deoxyribonucleic acid (DNA) is known to be soluble in water only and exhibits poor temperature stability. In contrary, it is well known that the complex of DNA - with cetyltrimethyl ammonium (CTMA) is soluble in alcohols and can be processed into very good optical quality thin films by solution casting and spin deposition. Despite the success of DNA-CTMA, there is still need for new cationic surfactants which would extend the range of available solvents for DNA complex. We test and present experimental results of influence of new surfactants based on benzalkonium chloride (BA), and didecyldimethylammonium chloride (DDCA) for applications in all optical switching.

  16. Cross-linking characterization of polymers based on their optical dispersion utilizing a white-light interferometer

    NASA Astrophysics Data System (ADS)

    Taudt, Ch.; Baselt, T.; Oreski, G.; Hirschl, Ch.; Koch, E.; Hartmann, P.

    2015-05-01

    This work analyses samples of the widely used encapsulant of photovoltaics modules, ethylene vinyl acetate (EVA). The samples were cross-linked using a lamination technique for different curing times (0 - 20 minutes). The cross-linking characterization is done by determinating the material dispersion with the aid of a combined temporal- and spectral domain white-light interferometer. With the proposed technique it was possible to discriminate the differences in crosslinking for the given curing times. One important feature of this approach is the possibility to perform space resolved measurements of the crosslinking state with μm-resolution. Furthermore the paper discusses the mathematical analysis and processing of measurement data and shows a prototype solution for the fast and automated data acquisition for industrial application.

  17. Global Membrane Protein Interactome Analysis using In vivo Crosslinking and Mass Spectrometry-based Protein Correlation Profiling*

    PubMed Central

    Larance, Mark; Kirkwood, Kathryn J.; Tinti, Michele; Brenes Murillo, Alejandro; Ferguson, Michael A. J.; Lamond, Angus I.

    2016-01-01

    We present a methodology using in vivo crosslinking combined with HPLC-MS for the global analysis of endogenous protein complexes by protein correlation profiling. Formaldehyde crosslinked protein complexes were extracted with high yield using denaturing buffers that maintained complex solubility during chromatographic separation. We show this efficiently detects both integral membrane and membrane-associated protein complexes,in addition to soluble complexes, allowing identification and analysis of complexes not accessible in native extracts. We compare the protein complexes detected by HPLC-MS protein correlation profiling in both native and formaldehyde crosslinked U2OS cell extracts. These proteome-wide data sets of both in vivo crosslinked and native protein complexes from U2OS cells are freely available via a searchable online database (www.peptracker.com/epd). Raw data are also available via ProteomeXchange (identifier PXD003754). PMID:27114452

  18. Global Membrane Protein Interactome Analysis using In vivo Crosslinking and Mass Spectrometry-based Protein Correlation Profiling.

    PubMed

    Larance, Mark; Kirkwood, Kathryn J; Tinti, Michele; Brenes Murillo, Alejandro; Ferguson, Michael A J; Lamond, Angus I

    2016-07-01

    We present a methodology using in vivo crosslinking combined with HPLC-MS for the global analysis of endogenous protein complexes by protein correlation profiling. Formaldehyde crosslinked protein complexes were extracted with high yield using denaturing buffers that maintained complex solubility during chromatographic separation. We show this efficiently detects both integral membrane and membrane-associated protein complexes,in addition to soluble complexes, allowing identification and analysis of complexes not accessible in native extracts. We compare the protein complexes detected by HPLC-MS protein correlation profiling in both native and formaldehyde crosslinked U2OS cell extracts. These proteome-wide data sets of both in vivo crosslinked and native protein complexes from U2OS cells are freely available via a searchable online database (www.peptracker.com/epd). Raw data are also available via ProteomeXchange (identifier PXD003754). PMID:27114452

  19. Designer Reagents for Mass Spectrometry-Based Proteomics: Clickable Cross-Linkers for Elucidation of Protein Structures and Interactions

    PubMed Central

    Sohn, Chang Ho; Agnew, Heather D.; Lee, J. Eugene; Sweredoski, Michael J.; Graham, Robert L.J.; Smith, Geoffrey T.; Hess, Sonja; Czerwieniec, Gregg; Loo, Joseph A.; Heath, James R.; Deshaies, Raymond J.; Beauchamp, J. L.

    2012-01-01

    We present novel homobifunctional amine-reactive clickable cross-linkers (CXLs) for investigation of three-dimensional protein structures and protein-protein interactions (PPIs). CXLs afford consolidated advantages not previously available in a simple cross-linker, including (1) their small size and cationic nature at physiological pH, resulting in good water solubility and cell permeability, (2) an alkyne group for bio-orthogonal conjugation to affinity tags via the click reaction for enrichment of cross-linked peptides, (3) a nucleophilic displacement reaction involving the 1,2,3-triazole ring formed in the click reaction, yielding a lock-mass reporter ion for only clicked peptides, and (4) higher charge states of cross-linked peptides in the gas-phase for augmented electron transfer dissociation (ETD) yields. Ubiquitin, a lysine-abundant protein, is used as a model system to demonstrate structural studies using CXLs. To validate the sensitivity of our approach, biotin-azide labeling and subsequent enrichment of cross-linked peptides are performed for cross-linked ubiquitin digests mixed with yeast cell lysates. Cross-linked peptides are detected and identified by collision induced dissociation (CID) and ETD with linear quadrupole ion trap (LTQ)-Fourier transform ion cyclotron resonance (FTICR) and LTQ-Orbitrap mass spectrometers. The application of CXLs to more complex systems (e.g., in vivo cross-linking) is illustrated by Western blot detection of Cul1 complexes including known binders, Cand1 and Skp2, in HEK 293 cells, confirming good water solubility and cell-permeability. PMID:22339618

  20. Development of porous alginate-based scaffolds covalently cross-linked through a peroxidase-catalyzed reaction.

    PubMed

    Sakai, Shinji; Kawakami, Koei

    2011-01-01

    Porous scaffolds are important in tissue engineering. We developed porous scaffolds from the hydrogels of an alginate derivative bearing phenolic hydroxyl groups. The hydrogels were prepared using horseradish peroxidase (HRP) to catalyze the cross-linking between the phenolic hydroxyl groups. A porous structure with a pore size of approx. 200 μm was developed through simultaneous water-extraction and ionic cross-linking by calcium ions by soaking frozen hydrogels in the mixture of ethanol and CaCl2 solution at -20°C. Due to the existence of the covalent cross-links developed through the enzymatic reaction, the porous form had a higher stability from a loss of cross-linked calcium ions than that obtained from non-modified sodium alginate (Na-Alg). The porous specimen developed from the hydrogel obtained with 10 U/ml HRP and 10 mM H2O2 showed about 1.5-times greater repulsion forces than those detected for the porous specimen obtained from Na-Alg toward compressions. No harmful effects of the enzymatically cross-linked specimens were detected on the growth and morphology of the entrapped cells: cells in the enzymatically cross-linked specimens showed almost the same growth profile and morphology with those in the porous specimen obtained from Na-Alg. PMID:21144141

  1. Crosslinked Redox-Responsive Micelles Based on Lipoic Acid-Derived Amphiphiles for Enhanced siRNA Delivery.

    PubMed

    Tschiche, Ariane; Thota, Bala N S; Neumann, Falko; Schäfer, Andreas; Ma, Nan; Haag, Rainer

    2016-06-01

    Successful application of gene silencing approaches critically depends on systems that are able to safely and efficiently deliver genetic material such as small interfering RNA (siRNA). Due to their beneficial well-defined dendritic nanostructure, self-assembling dendrimers are emerging as promising nanovectors for siRNA delivery. However, these kinds of vectors are plagued with stability issues, especially when considered for in vivo applications. Therefore, in the present study, disulfide-based temporarily fixed micelles are developed that can degrade upon reductive conditions, and thus lead to efficient cargo release. In detail, lipoic acid-derived crosslinked micelles are synthesized based on small polymerizable dendritic amphiphiles. Particularly, one candidate out of this series is able to efficiently release siRNA due to its redox-responsive biodegradable profile when exposed to simulated intracellular environments. As a result, the reduction-triggered disassembly leads to potent gene silencing. In contrast, noncrosslinkable, structurally related constructs fails under the tested assay conditions, thereby confirming the applied rational design approach and demonstrating its large potential for future in vivo applications. PMID:26847397

  2. Construction of Covalent Organic Nanotubes by Light-Induced Cross-Linking of Diacetylene-Based Helical Polymers.

    PubMed

    Maeda, Kaho; Hong, Liu; Nishihara, Taishi; Nakanishi, Yusuke; Miyauchi, Yuhei; Kitaura, Ryo; Ousaka, Naoki; Yashima, Eiji; Ito, Hideto; Itami, Kenichiro

    2016-08-31

    Organic nanotubes (ONTs) are tubular nanostructures composed of small molecules or macromolecules that have found various applications including ion sensor/channels, gas absorption, and photovoltaics. While most ONTs are constructed by self-assembly processes based on weak noncovalent interactions, this unique property gives rise to the inherent instability of their tubular structures. Herein, we report a simple "helix-to-tube" strategy to construct robust, covalent ONTs from easily accessible poly(m-phenylene diethynylene)s (poly-PDEs) possessing chiral amide side chains that can adopt a helical conformation through hydrogen-bonding interactions. The helically folded poly-PDEs subsequently undergo light-induced cross-linking at longitudinally aligned 1,3-butadiyne moieties across the whole helix to form covalent tubes (ONTs) both in solution and solid phases. The structures of poly-PDEs and covalent ONTs were characterized by spectroscopic analyses, diffraction analysis, and microscopic analyses. We envisage that this simple yet powerful "helix-to-tube" strategy will generate a range of ONT-based materials by introducing functional moieties into a monomer. PMID:27486790

  3. Resist surface crosslinking using amine-based reactive rinses to mitagate pattern collapse in thin film lithography

    NASA Astrophysics Data System (ADS)

    Yeh, Wei-Ming; Lawson, Richard A.; Tolbert, Laren M.; Henderson, Clifford L.

    2012-03-01

    As the semiconductor industry continues to push to smaller critical dimensions, pattern collapse during lithographic processing caused by unbalanced capillary forces during the final rinse and drying process has become an important problem that can limit the practical resolution of a resist material to feature sizes larger than its intrinsic resolution limit. One of the primary modes of pattern collapse is via elastoplastic pattern deformation which is strongly related to the mechanical properties of the resist. One approach to mitigating such collapse problems is to enhance the mechanical properties of the resist features. Since such modification of resist physical properties for pattern collapse purposes is difficult to achieve through modified formulation of the resist itself (i.e. due to the complex set of requirements that a resist must satisfy and the complex set of physical and chemical phenomena that underlie the imaging processing itself), we have pursued an alternative strategy for improving the resist mechanical properties after features are developed in the film but before they are rinsed and dried. The family of techniques being developed in this work function through the use of aqueous compatible reactive rinse solutions that can be applied to developed resist features while they are wet during normal rinse processing on a track system. By applying these techniques during the rinse process, the resist features can be strengthened before they are subjected to significant capillary forces during the final drying step. In this work, the use of diamine compounds to reactively crosslink the surface of resists containing carboxylic acid groups through formation of amide bonds using carbodiimide chemistry has been explored. One advantage of this approach is that it is an aqueous process that should be easily compatible with high volume, track-based lithographic processes. Contact angle studies and x-ray photoelectron spectroscopy (XPS) were used to

  4. Enzyme mechanism-based, oxidative DNA-protein cross-links formed with DNA polymerase β in vivo.

    PubMed

    Quiñones, Jason L; Thapar, Upasna; Yu, Kefei; Fang, Qingming; Sobol, Robert William; Demple, Bruce

    2015-07-14

    Free radical attack on the C1' position of DNA deoxyribose generates the oxidized abasic (AP) site 2-deoxyribonolactone (dL). Upon encountering dL, AP lyase enzymes such as DNA polymerase β (Polβ) form dead-end, covalent intermediates in vitro during attempted DNA repair. However, the conditions that lead to the in vivo formation of such DNA-protein cross-links (DPC), and their impact on cellular functions, have remained unknown. We adapted an immuno-slot blot approach to detect oxidative Polβ-DPC in vivo. Treatment of mammalian cells with genotoxic oxidants that generate dL in DNA led to the formation of Polβ-DPC in vivo. In a dose-dependent fashion, Polβ-DPC were detected in MDA-MB-231 human cells treated with the antitumor drug tirapazamine (TPZ; much more Polβ-DPC under 1% O2 than under 21% O2) and even more robustly with the "chemical nuclease" 1,10-copper-ortho-phenanthroline, Cu(OP)2. Mouse embryonic fibroblasts challenged with TPZ or Cu(OP)2 also incurred Polβ-DPC. Nonoxidative agents did not generate Polβ-DPC. The cross-linking in vivo was clearly a result of the base excision DNA repair pathway: oxidative Polβ-DPC depended on the Ape1 AP endonuclease, which generates the Polβ lyase substrate, and they required the essential lysine-72 in the Polβ lyase active site. Oxidative Polβ-DPC had an unexpectedly short half-life (∼ 30 min) in both human and mouse cells, and their removal was dependent on the proteasome. Proteasome inhibition under Cu(OP)2 treatment was significantly more cytotoxic to cells expressing wild-type Polβ than to cells with the lyase-defective form. That observation underscores the genotoxic potential of oxidative Polβ-DPC and the biological pressure to repair them. PMID:26124145

  5. Enzyme mechanism-based, oxidative DNA–protein cross-links formed with DNA polymerase β in vivo

    PubMed Central

    Quiñones, Jason L.; Thapar, Upasna; Yu, Kefei; Fang, Qingming; Sobol, Robert William; Demple, Bruce

    2015-01-01

    Free radical attack on the C1′ position of DNA deoxyribose generates the oxidized abasic (AP) site 2-deoxyribonolactone (dL). Upon encountering dL, AP lyase enzymes such as DNA polymerase β (Polβ) form dead-end, covalent intermediates in vitro during attempted DNA repair. However, the conditions that lead to the in vivo formation of such DNA–protein cross-links (DPC), and their impact on cellular functions, have remained unknown. We adapted an immuno-slot blot approach to detect oxidative Polβ-DPC in vivo. Treatment of mammalian cells with genotoxic oxidants that generate dL in DNA led to the formation of Polβ-DPC in vivo. In a dose-dependent fashion, Polβ-DPC were detected in MDA-MB-231 human cells treated with the antitumor drug tirapazamine (TPZ; much more Polβ-DPC under 1% O2 than under 21% O2) and even more robustly with the “chemical nuclease” 1,10-copper-ortho-phenanthroline, Cu(OP)2. Mouse embryonic fibroblasts challenged with TPZ or Cu(OP)2 also incurred Polβ-DPC. Nonoxidative agents did not generate Polβ-DPC. The cross-linking in vivo was clearly a result of the base excision DNA repair pathway: oxidative Polβ-DPC depended on the Ape1 AP endonuclease, which generates the Polβ lyase substrate, and they required the essential lysine-72 in the Polβ lyase active site. Oxidative Polβ-DPC had an unexpectedly short half-life (∼30 min) in both human and mouse cells, and their removal was dependent on the proteasome. Proteasome inhibition under Cu(OP)2 treatment was significantly more cytotoxic to cells expressing wild-type Polβ than to cells with the lyase-defective form. That observation underscores the genotoxic potential of oxidative Polβ-DPC and the biological pressure to repair them. PMID:26124145

  6. Biodegradable and non-retrogradable eco-films based on starch-glycerol with citric acid as crosslinking agent.

    PubMed

    Seligra, Paula González; Medina Jaramillo, Carolina; Famá, Lucía; Goyanes, Silvia

    2016-03-15

    Biodegradable and non-retrogradable starch-glycerol based films were obtained using citric acid (CA) as crosslinking agent at 75°C. This material allowed decreasing water vapor permeability (WVP) more than 35%, remained amorphous for at least 45 days as a result of the network formed by the CA that avoided starch retrogradation and maintained the degradability in compost, occurring only six days after the films without citric acid. A simulation of the gelatinization process of starch-glycerol with and without CA, using a differential thermal analysis device, showed that the system with CA completed the gelatinization 5°C before than the other and, CA first reacted with glycerol and then starch-glycerol-CA reaction occurred. The temperature at which the gelatinization process was carried out was critical to obtain the best results. An increase of gelatinization process temperature at 85°C in system with CA, led to a worsening on WVP and its integrity after a swelling process with dimethylsulphoxide (DMSO), compared to the films processed at 75°C. PMID:26794739

  7. HPMC-based gastroretentive dual working matrices coated with Ca(+2) ion crosslinked alginate-fenugreek gum gel membrane.

    PubMed

    Bera, Hriday; Gaini, Chakravarthy; Kumar, Sanoj; Sarkar, Srimanta; Boddupalli, Shashank; Ippagunta, Sohitha Reddy

    2016-10-01

    Novel alginate-fenugreek gum (FG) gel membrane coated hydroxypropylmethylcellulose (HPMC) based matrix tablets were developed for intragastric quetiapine fumarate (QF) delivery by combining floating and swelling mechanisms. The effects of polymer blend ratios [HPMC K4M:HPMC E15] and citric acid contents on time taken for 50% drug release (t50%, min) and drug release at 8h (Q8h, %) were studied to optimize the core tablets by 3(2) factorial design. The optimized tablets (F-O) exhibited t50% of 247.67±3.51min and Q8h of 71.11±0.32% with minimum errors in prediction. The optimized tablets were coated with Ca(+2) ions crosslinked alginate-FG gel membrane by diffusion-controlled interfacial complexation technique. The biopolymeric-coated optimized matrices exhibited superior buoyancy, preferred swelling characteristics and slower drug release rate. The drug release profiles of the QF-loaded uncoated and coated optimized matrices were best fitted in Korsmeyer-Peppas model with anomalous diffusion driven mechanism. The uncoated and coated tablets containing QF were also characterized for drug-excipients compatibility, thermal behaviour and surface morphology by FTIR, DSC and SEM analyses, respectively. Thus, the newly developed alginate-FG gel membrane coated HPMC matrices are appropriate for intragastric delivery of QF over a prolonged period of time with greater therapeutic benefits. PMID:27287111

  8. Enzymatically-crosslinked injectable hydrogels based on biomimetic dextran-hyaluronic acid conjugates for cartilage tissue engineering.

    PubMed

    Jin, R; Teixeira, L S Moreira; Dijkstra, P J; van Blitterswijk, C A; Karperien, M; Feijen, J

    2010-04-01

    Polysaccharide hybrids consisting of hyaluronic acid (HA) grafted with a dextran-tyramine conjugate (Dex-TA) were synthesized and investigated as injectable biomimetic hydrogels for cartilage tissue engineering. The design of these hybrids (denoted as HA-g-Dex-TA) is based on the molecular structure of proteoglycans present in the extracellular matrix of native cartilage. Hydrogels of HA-g-Dex-TA were rapidly formed within 2 min via enzymatic crosslinking of the tyramine residues in the presence of horseradish peroxidase and hydrogen peroxide. The gelation time, equilibrium swelling and storage modulus could be adjusted by varying the degree of substitution of tyramine residues and polymer concentration. Bovine chondrocytes incorporated in the HA-g-Dex-TA hydrogels remained viable, as shown by the Live-dead assay. Moreover, enhanced chondrocyte proliferation and matrix production were observed in the HA-g-Dex-TA hydrogels compared to Dex-TA hydrogels. These results suggest that HA-g-Dex-TA hydrogels have a high potential as injectable scaffolds for cartilage tissue engineering. PMID:20116847

  9. Efficacy of a crosslinked hyaluronic acid-based hydrogel as a tear film supplement: a masked controlled study.

    PubMed

    Williams, David L; Mann, Brenda K

    2014-01-01

    Keratoconjunctivitis sicca (KCS), or dry eye, is a significant medical problem in both humans and dogs. Treating KCS often requires the daily application of more than one type of eye drop in order to both stimulate tear prodcution and provide a tear supplement to increase hydration and lubrication. A previous study demonstrated the potential for a crosslinked hyaluronic acid-based hydrogel (xCMHA-S) to reduce the clinical signs associated with KCS in dogs while using a reduced dosing regimen of only twice-daily administration. The present study extended those results by comparing the use of the xCMHA-S to a standard HA-containing tear supplement in a masked, randomized clinical study in dogs with a clinical diagnosis of KCS. The xCMHA-S was found to significantly improve ocular surface health (conjunctival hyperaemia, ocular irritation, and ocular discharge) to a greater degree than the alternative tear supplement (P = 0.0003). Further, owners reported the xCMHA-S treatment as being more highly effective than the alternative tear supplement (P = 0.0024). These results further demonstrate the efficacy of the xCMHA-S in reducing the clinical signs associated with KCS, thereby improving patient health and owner happiness. PMID:24914681

  10. Photo-responsive shell cross-linked micelles based on carboxymethyl chitosan and their application in controlled release of pesticide.

    PubMed

    Ye, Zhao; Guo, Jingjing; Wu, Dewei; Tan, Mingyuan; Xiong, Xiong; Yin, Yihua; He, Guanghua

    2015-11-01

    An amphiphilic carboxymethyl chitosan conjugate with photolabile 2-nitrobenzyl side groups (NBS-CMCS) was synthesized, which could self-assemble into polymeric micelles in aqueous condition following by adding dropwise dialdehyde to form a cross-linking structure. TEM and (1)H NMR confirmed that the cross-linked micelles had a core-shell configuration with an average diameter of 140 ± 5.5 nm. DLS and TEM observations showed that the cross-linked micelles were stable in aqueous solution at pH 7.0 without light irradiation, while they could transfer into nanocapsules upon exposure to 365 nm UV light. Diuron, a photosynthetic inhibitor, was encapsulated in the cross-linked micelles reaching encapsulation efficiency as much as 91.9%. No release of the encapsulated diuron was detected without light, whereas a release rate as high as 96.8% over 8h at pH 7.0 buffer was observed under solar stimulated irradiation, indicating that the cross-linked micelles may be used as a photo-controlled sustained release carrier for the delivery of photosynthetic inhibitor. PMID:26256378

  11. Synthesis of cellulose-based superabsorbent hydrogels by high-energy irradiation in the presence of crosslinking agent

    NASA Astrophysics Data System (ADS)

    Fekete, Tamás; Borsa, Judit; Takács, Erzsébet; Wojnárovits, László

    2016-01-01

    Superabsorbent hydrogels were prepared from aqueous solutions of four cellulose derivatives (carboxymethylcellulose Na-salt - CMC, methylcellulose - MC, hydroxyethylcellulose - HEC and hydroxypropylcellulose - HPC) by gamma irradiation initiated crosslinking. CMC was used for the majority of the measurements. N,N'-methylene-bis-acrylamide (MBA) crosslinking agent was used to modify the gel properties. The crosslink density increased with the MBA concentration, leading to an improved gel fraction and lower water uptake. The crosslinking efficiency was the highest up to 1 w/wpolymer% MBA concentration. Very high MBA content (10 w/wpolymer%) led to a heterogeneous gel structure. Gelation also occurred under milder conditions in the presence of MBA: good gel properties were achieved at significantly lower doses and solute concentrations as compared to crosslinker-free solutions. The time required to reach maximum water uptake increased with the degree of swelling in equilibrium. Swelling properties of CMC gels with lower water uptake showed lower sensitivity to the ionic strength of the solvent.

  12. Formation of N-N cross-links in DNA by reaction of radiation-produced DNA base pair diradicals: a DFT study.

    PubMed

    Pottiboyina, Venkata; Kumar, Anil; Sevilla, Michael D

    2011-12-22

    This study employs DFT (density functional theory) to investigate the formation of hydrazine-like (N-N) cross-linked structures between DNA base pair diradicals that are likely to result from the interaction of high linear energy transfer (LET) radiation, such as ion-beam radiation, with DNA. In our calculations, we generated the guanine (G), cytosine (C), adenine (A), and thymine (T) radicals by removing one hydrogen atom from an N-H bond involved in the normal base pairing. The radical species formed are those that naturally result from one-electron oxidation of the bases followed by deprotonation. N-N cross-links between G and C or A and T diradicals were studied using the BHandHLYP, B3LYP, M06, and M06-2X density functionals and 6-31G* basis set. From a comparison to several test cases performed with the G3B3 method, which gives thermodynamically reliable values, we found that calculations employing the BHandHLYP/6-31G* method predict the best estimates of bonding energies for hydrazine-like structures. Our study shows that the N-N cross-link formed between guanine radical and a neutral cytosine is endothermic in nature but can form metastable structures. However, the reactions between two DNA base radicals (diradical) to form several N-N cross-linked structures are found to be highly exothermic in nature. The N-N cross-links formed between various G-C, G-G, and C-C diradicals have binding energies in the range of ca. -54 to -68, -41 to -47, and -67 to -75 kcal/mol, respectively, whereas A-T, A-A, and T-T have binding energies of -80, -60, and -98 kcal/mol, respectively. In all purine-pyrimidine N-N cross-linked structures, the highest occupied molecular orbital (HOMO) is found to be localized on the purine moiety and the lowest unoccupied molecular orbital (LUMO) is on the pyrimidine moiety. PMID:22050209

  13. Biocompatibility of choline salts as crosslinking agents for collagen based biomaterials.

    PubMed

    Vijayaraghavan, R; Thompson, B C; MacFarlane, D R; Kumar, Ramadhar; Surianarayanan, M; Aishwarya, S; Sehgal, P K

    2010-01-14

    A series of novel choline based salts, some of which can be described as ionic liquids, are prepared and evaluated for their biocompatibility; when combined with collagenous biomaterials they exhibit good cell viability and adhesion properties as required for biomedical implant applications. PMID:20024356

  14. Furan oxidation based cross-linking: a new approach for the study and targeting of nucleic acid and protein interactions.

    PubMed

    Carrette, L L G; Gyssels, E; De Laet, N; Madder, A

    2016-01-28

    Furan mediated nucleic acid cross-linking, initially developed for DNA interstrand duplex cross-linking, has matured into a versatile tool for the study of protein and nucleic acid interactions, ready to face its applications. The methodology was initially developed for easy and clean chemical generation of DNA interstrand cross-linked duplexes, but has been further expanded for use with other probes, targets and triggers, now allowing mild biologically significant cross-linking with potential therapeutic benefit. It was shown that the methodology could be repurposed for RNA interstrand cross-linking, which is very relevant in today's antisense approaches or miRNA target identification endeavors. This further illustrates the furan oxidation method's generality and mildness, especially when using red light for oxidation. A complementary antigene approach has been explored through duplex targeting with furan modified triplex forming oligonucleotides (TFOs) and DNA binding proteins. Also targeting of peptides and proteins by furan-modified DNA and peptides has been explored. Thorough methodology examination exploring variable reaction conditions in combination with a series of different furan-modified building blocks and application of different activation signals resulted in a detailed understanding of the mechanisms involved and factors influencing the yield and selectivity of the reaction. In order to draw the bigger picture of the scope and limitations of furan-oxidation cross-linking, we here provide a unique side by side comparison and discussion of our published data, supplemented with unpublished results, providing a clear performance report of the currently established furan toolbox and its application potential in various biomacromolecular complexes. PMID:26679922

  15. Controlling the Adhesion and Differentiation of Mesenchymal Stem Cells Using Hyaluronic Acid-based, Doubly Crosslinked Networks

    PubMed Central

    Jha, Amit K.; Xu, Xian; Duncan, Randall L.; Jia, Xinqiao

    2011-01-01

    We have created hyaluronic acid (HA)-based, cell-adhesive hydrogels that direct the initial attachment and the subsequent differentiation of human mesenchymal stem cells (MSCs) into pre-osteoblasts without osteogenic supplements. HA-based hydrogel particles (HGPs) with an average diameter of 5-6 μm containing an estimated 2.2 wt% gelatin (gHGPs) were synthesized by covalent immobilization of gelatin to HA HGPs prepared via an inverse emulsion polymerization technique. Separately, a photocrosslinkable HA macromer (HAGMA) was synthesized by chemical modification of HA with glycidyl methacrylate (GMA). Doubly crosslinked networks (DXNs) were engineered by embedding gHGPs in a secondary network established by HAGMA at a particle concentration of 2.5 wt%. The resultant composite gels, designated as HA-gHGP, have an average compressive modulus of 21 kPa, and are non-toxic to the cultured MSCs. MSCs readily attached to these gels, exhibiting an early stage of stress fibers assembly 3 h post seeding. By day 7, stellated-shaped cells with extended filopodia were found on HA-gHGP gels. Moreover, cells had migrated deep into the matrix, forming a three dimensional, branched and interconnected cell community. Conversely, MSCs on the control gels lacking gelatin moieties formed isolated spheroids with rounded cell morphology. After 28 days of culture on HA-gHGP, Type I collagen production and mineral deposition were detected in the absence of osteogenic supplements, suggesting induction of osteogenic differentiation. In contrast, cells on the control gels expressed markers for adipogenesis. Overall, the HA-gHGP composite matrix has great promise for directing the osteogenic differentiation of MSCs by providing an adaptable environment through the spatial presentation of cell adhesive modules. PMID:21216457

  16. Optical laser cross-link in space-based systems used for satellite communications

    NASA Astrophysics Data System (ADS)

    Panahi, Allen; Kazemi, Alex A.

    2010-04-01

    Building high speed communications network using optical links in space has proven to be an extremely complicated task and many such schemes were tried without success in the past. However in the last few years, there has been impressive progress made to bring the concept to fruition in civilian and government non-classified projects. Space-based optical communications using satellites in low earth orbit (LEO) and Geo-synchronous orbits (GEO) hold great promise for the proposed Internet in the Sky network of the future. Laser Communications offer a viable alternative to established RF communications for inter-satellite links and other applications where high performance links are a necessity. This paper will focus on the requirements of the space-based lasers and optics used for beam forming, as well as receiver antenna gain and detectors used in free space communications. High data rate, small antenna size, narrow beam divergence, and a narrow field of view are characteristics of laser communications that offer a number of potential advantages for system design. Also discussed are the critical parameters in the transmitter, channel, receiver, and link budget that are employed in successful inter-satellite communications system.

  17. Application of Markov chain to the pattern of mitochondrial deoxyribonucleic acid mutations

    NASA Astrophysics Data System (ADS)

    Vantika, Sandy; Pasaribu, Udjianna S.

    2014-03-01

    This research explains how Markov chain used to model the pattern of deoxyribonucleic acid mutations in mitochondrial (mitochondrial DNA). First, sign test was used to see a pattern of nucleotide bases that will appear at one position after the position of mutated nucleotide base. Results obtained from the sign test showed that for most cases, there exist a pattern of mutation except in the mutation cases of adenine to cytosine, adenine to thymine, and cytosine to guanine. Markov chain analysis results on data of mutations that occur in mitochondrial DNA indicate that one and two positions after the position of mutated nucleotide bases tend to be occupied by particular nucleotide bases. From this analysis, it can be said that the adenine, cytosine, guanine and thymine will mutate if the nucelotide base at one and/or two positions after them is cytosine.

  18. Cs-based optical frequency measurement using cross-linked optical and microwave oscillators

    NASA Astrophysics Data System (ADS)

    Tamm, Chr.; Huntemann, N.; Lipphardt, B.; Gerginov, V.; Nemitz, N.; Kazda, M.; Weyers, S.; Peik, E.

    2014-02-01

    We describe a measurement of the frequency of the 2S1/2(F=0)-2D3/2(F'=2) transition of 171Yb+ at the wavelength 436 nm (frequency 688 THz), using a single Yb+ ion confined in a Paul trap and two cesium fountains as references. In one of the fountains, the frequency of the microwave oscillator that interrogates the cesium atoms is stabilized by the laser that excites the Yb+ reference transition with a linewidth in the hertz range. The stability is transferred to the microwave oscillator with the use of a fiber laser-based optical frequency comb generator that also provides the frequency conversion for the absolute frequency measurement. The frequency comb generator is configured as a transfer oscillator so that fluctuations of the pulse repetition rate and of the carrier offset frequency do not degrade the stability of the frequency conversion. The phase noise level of the generated ultrastable microwave signal is comparable to that of a cryogenic sapphire oscillator. For fountain operation with optical molasses loaded from a laser-cooled atomic beam source, we obtain a stability corresponding to a fractional Allan deviation of 4.1 × 10-14 (τ /s)-1/2. With the molasses loaded from thermal vapor and an averaging time of 65 h, we measure the frequency of the Yb+ transition with a relative statistical uncertainty of 2.8 × 10-16 and a systematic uncertainty of 5.9 × 10-16. The frequency was also simultaneously measured with the second fountain that uses a quartz-based interrogation oscillator. The unperturbed frequency of the Yb+ transition is realized with an uncertainty of 1.1 × 10-16 that mainly results from the uncertainty of the blackbody shift at the operating temperature near 300 K. The transition frequency of 688 358 979 309 307.82(36) Hz, measured with the two fountains, is in good agreement with previous results.

  19. Structure of Replicating Simian Virus 40 Deoxyribonucleic Acid Molecules 1

    PubMed Central

    Sebring, E. D.; Kelly, T. J.; Thoren, M. M.; Salzman, N. P.

    1971-01-01

    Properties of replicating simian virus 40 (SV40) deoxyribonucleic acid (DNA) have been examined by sedimentation analysis and by direct observation during a lytic cycle of infection of African green monkey kidney cells. Two types of replicating DNA molecules were observed in the electron microscope. One was an open structure containing two branch points, three branches, and no free ends whose length measurements were consistent with those expected for replicating SV40 DNA molecules. A second species had the same features as the open structure, but in addition it contained a superhelix in the unreplicated portion of the molecule. Eighty to ninety per cent of the replicative intermediates (RI) were in this latter configuration, and length measurements of these molecules also were consistent with replicating SV40 DNA. Replicating DNA molecules with this configuration have not been described previously. RI, when examined in ethidium bromide-cesium chloride (EB-CsCl) isopycnic gradients, banded in a heterogeneous manner. A fraction of the RI banded at the same density as circular SV40 DNA containing one or more single-strand nicks (component II). The remaining radioactive RI banded at densities higher than that of component II, and material was present at all densities between that of supercoiled double-stranded DNA (component I) and component II. When RI that banded at different densities in EB-CsCl were examined in alkaline gradients, cosedimentation of parental DNA and newly replicated DNA did not occur. All newly replicated DNA sedimented more slowly than did intact single-stranded SV40 DNA, a finding that is inconsistent with the rolling circle model of DNA replication. An inverse correlation exists between the extent of replication of the SV40 DNA and the banding density in EB-CsCl. Under alkaline conditions, the parental DNA strands that were contained in the RI sedimented as covalently closed structures. The sedimentation rates in alkali of the covalently closed

  20. Engineered Microtissues Formed by Schiff Base Crosslinking Restore the Chondrogenic Potential of Aged Mesenchymal Stem Cells.

    PubMed

    Millan, Christopher; Cavalli, Emma; Groth, Thomas; Maniura-Weber, Katharina; Zenobi-Wong, Marcy

    2015-06-24

    A universal method for reproducibly directing stem cell differentiation remains a major challenge for clinical applications involving cell-based therapies. The standard approach for chondrogenic induction by micromass pellet culture is highly susceptible to interdonor variability. A novel method for the fabrication of condensation-like engineered microtissues (EMTs) that utilizes hydrophilic polysaccharides to induce cell aggregation is reported here. Chondrogenesis of mesenchymal stem cells (MSCs) in EMTs is significantly enhanced compared to micromass pellets made by centrifugation measured by type II collagen gene expression, dimethylmethylene blue assay, and histology. MSCs from aged donors that fail to differentiate in pellet culture are successfully induced to synthesize cartilage-specific matrix in EMTs under identical media conditions. Furthermore, the EMT polysaccharides support the loading and release of the chondroinduction factor transforming growth factor β3 (TGF-β3). TGF-β-loaded EMTs (EMT(+TGF) ) facilitate cartilaginous tissue formation during culture in media not supplemented with the growth factor. The clinical potential of this approach is demonstrated in an explant defect model where EMT(+TGF) from aged MSCs synthesize de novo tissue containing sulfated glycosaminoglycans and type II collagen in situ. PMID:25866187

  1. Space-based laser cross-link systems used in satellite communications

    NASA Astrophysics Data System (ADS)

    Panahi, Allen; Kazemi, Alex A.

    2009-05-01

    Space-based optical communications using satellites in low earth orbit (LEO) and Geo-synchronous orbits (GEO) hold great promise for the proposed Internet in the Sky network of the future. Building high speed communications network using optical links in space has proven to be an extremely complicated task and many such schemes were tried without success in the past. However in the last few years, there has been impressive progress made to bring the concept to fruition in civilian and government-non classified projects. Laser Communications offer a viable alternative to established RF communications for inter-satellite links and other applications where high performance links are a necessity. High data rate, small antenna size, narrow beam divergence, and a narrow field of view are characteristics of laser communications that offer a number of potential advantages for system design. This paper will focus on the requirements of the spacebased lasers and optics used for beam forming, as well as receiver antenna gain and detectors used in free space communications. Also discussed are the critical parameters in the transmitter, channel, receiver, and link budget that are employed in successful inter-satellite communications system.

  2. Bioreducible cross-linked polymers based on G1 peptide dendrimer as potential gene delivery vectors.

    PubMed

    Li, Chun-Yan; Wang, Hai-Jiao; Cao, Jing-Ming; Zhang, Ji; Yu, Xiao-Qi

    2014-11-24

    A series of cationic polymers based on low generation (G1) peptide dendrimer were synthesized with disulfide-containing linkages. The DNA binding abilities of the target polymers were studied by gel electrophoresis and fluorescence quenching assay. The bioreducible property of the disulfide-containing polymers P2 and P3 was also investigated in the presence of dithiothreitol (DTT). Results from dynamic light scattering (DLS) and transmission electron microscopy (TEM) assays reveal that these materials may condense DNA into nanoparticles with proper sizes and zeta-potentials. In vitro cell experiments show that compared to branched 25 KDa PEI, P2 and P3 may exhibit much higher gene transfection efficiency and lower cytotoxicity in both HEK293 and U-2OS cells. Additionally, polymer prepared from Michael addition gives better gene transfection ability, while polymer prepared from ring-opening reaction has better serum tolerance. Results indicate that these polymers might be promising non-viral gene vectors for their easy preparation, very low cytotoxicity, and good transfection efficiency. PMID:25282264

  3. Biocompatible hydrogels based on hyaluronic acid cross-linked with a polyaspartamide derivative as delivery systems for epithelial limbal cells.

    PubMed

    Fiorica, Calogero; Senior, Richard A; Pitarresi, Giovanna; Palumbo, Fabio Salvatore; Giammona, Gaetano; Deshpande, Pallavi; MacNeil, Sheila

    2011-07-29

    The aim of this work was to evaluate the potential use of hydrogels based on hyaluronic acid (HA) chemically cross-linked with α,β-poly(N-2-hydroxyethyl) (2-aminoethylcarbamate)-D,L-aspartamide (PHEA-EDA) as substitutes for the amniotic membrane able to release limbal cells for corneal regeneration. Hydrogels, shaped as films, with three different molar ratios (X) between PHEA-EDA and HA (X = 0.5, 1.0 and 1.5) have been investigated. First, it has been evaluated their swelling ability, hydrolytic resistance in simulated physiological fluid and cell compatibility by using human dermal fibroblasts chosen as a model cell line. Then adhesion studies in comparison with collagen gel, have been performed by using immortalized cells, such as human corneal epithelial cells (HCEC) or primary cells, such as rabbit limbal epithelial cells (RLEC) and/or rabbit limbal fibroblasts (RLF). HA/PHEA-EDA hydrogels allow a moderate/poor adhesion of all investigated cells thus suggesting their potential ability to act as cell delivery systems. Finally, commercial contact lenses have been coated, in their inner surface, with each HA/PHEA-EDA film and it has been found that in these conditions, a greater cell adhesion occurs, particularly when RLEC are in co-culture with RLF. However, this adhesion is only transitory, in fact after three days, viable cells are released in the culture medium thus suggesting a potential application of HA/PHEA-EDA hydrogels, for delivering limbal cells in the treatment of corneal damage. PMID:21596121

  4. Influence of natural and synthetic crosslinking reagents on the structural and mechanical properties of chitosan-based hybrid hydrogels.

    PubMed

    Garnica-Palafox, I M; Sánchez-Arévalo, F M

    2016-10-20

    The objective of this work was to correlate the physical and chemical properties of chitosan/poly(vinyl alcohol)/genipin (CS/PVA/GEN) and chitosan/poly(vinyl alcohol)/glutaraldehyde (CS/PVA/GA) hydrogels with their structural and mechanical responses. In addition, their molecular structures were determined and confirmed using FTIR spectroscopy. The results indicated that the hybrid hydrogels crosslinked with genipin showed similar crystallinity, thermal properties, elongation ratio and structural parameters as those crosslinked with glutaraldehyde. However, it was found that the elastic moduli of the two hybrid hydrogels were slightly different: 2.82±0.33MPa and 2.08±0.11MPa for GA and GEN, respectively. Although the hybrid hydrogels crosslinked with GEN presented a lower elastic modulus, the main advantage is that GEN is five to ten thousand times less cytotoxic than GA. This means that the structural and mechanical properties of hybrid hydrogels crosslinked with GEN can easily be tuned and could have potential applications in the tissue engineering, regenerative medicine, food, agriculture and environmental industries. PMID:27474657

  5. Fabrication of poly(propylene fumarate)-based orthopaedic implants by photo-crosslinking through transparent silicone molds.

    PubMed

    Timmer, Mark D; Carter, Cory; Ambrose, Catherine G; Mikos, Antonios G

    2003-11-01

    This work presents a new molding process for photo-crosslinked, degradable polymeric networks of poly(propylene fumarate) (PPF) and the crosslinking agent poly(propylene fumarate)-diacrylate (PPF-DA). Transparent room temperature vulcanizing silicone molds were fabricated for parts ranging from simple test coupons to orthopaedic implants. The PPF/PPF-DA resin blend was injected into the cavity and photo-crosslinked as light was transmitted through the mold wall. The volumetric shrinkage, mechanical properties, and the effects of gamma sterilization were reported for molded PPF/PPF-DA networks prepared with varying compositions of the two polymer components. The shrinkage decreased while the mechanical properties displayed a general increasing trend when more of the crosslinking agent was incorporated into the network. Gamma irradiation resulted in an improvement of the mechanical properties. In addition, PPF/PPF-DA replicates of a 70:30 poly(L/DL-lactide) biodegradable fixation plate and a bone allograft interbody fusion spacer were produced to evaluate the performance of PPF/PPF-DA as an orthopaedic implant and allow for a comparison to be made with materials that have been established for clinical use. PMID:12951014

  6. Dynamic Cross-Linking of Polymeric Binders Based on Host-Guest Interactions for Silicon Anodes in Lithium Ion Batteries.

    PubMed

    Kwon, Tae-woo; Jeong, You Kyeong; Deniz, Erhan; AlQaradawi, Siham Y; Choi, Jang Wook; Coskun, Ali

    2015-11-24

    We report supramolecular cross-linking of polymer binders via dynamic host-guest interactions between hyperbranched β-cyclodextrin polymer and a dendritic gallic acid cross-linker incorporating six adamantane units for high-capacity silicon anodes. Calorimetric analysis in the solution phase indicates that the given host-guest complexation is a highly spontaneous and enthalpically driven process. These findings are further verified by carrying out gelation experiments in both aqueous and organic media. The dynamic cross-linking process enables intimate silicon-binder interaction, structural stability of electrode film, and controlled electrode-electrolyte interface, yielding enhanced cycling performance. Control experiments using both α, γ-CDp with different cavity sizes and a guest molecule incorporating a single adamantane unit verified that the enhanced cycle life originates from the host-guest interaction between β-cyclodextrin and adamantane. The impact of the dynamic cross-linking is maximized at an optimal stoichiometry between the two components. Importantly, the present investigation proves that the molecular-level tuning of the host-guest interactions can be translated directly to the cycling performance of silicon anodes. PMID:26422642

  7. A new injectable biphasic hydrogel based on partially hydrolyzed polyacrylamide and nano hydroxyapatite, crosslinked with chromium acetate, as scaffold for cartilage regeneration

    NASA Astrophysics Data System (ADS)

    Koushki, N.; Tavassoli, H.; Katbab, A. A.; Katbab, P.; Bonakdar, S.

    2015-05-01

    Polymer scaffolds are applied in the field of tissue engineering as three dimensional structures to organize cells and present stimuli to direct generation of a desired damaged tissue. In situ gelling scaffolds have attracted great attentions, as they are structurally similar to the extra cellular matrix (ECM). In the present work, attempts have been made to design and fabricate a new injectable and crosslinkable biphasic hydrogel based on partially hydrolyzed polyacrylamide (HPAM), chromium acetate as crosslink agent and nanocrystalline hydroxyapatite (nHAp) as reinforcing and bioactive agent for repair and regeneration of damaged cartilage. The distinct characteristic of HPAM is the presence of carboxylate anion groups on its backbone which allows to engineer the structure of the hydrogel for the desired bioactivity with appropriate cells differentiation towards both soft and hard (bone) tissues. The synthesized hydrogel exhibited bifunctional behavior which was derived by its biphasic structure in which one phase was loaded with nano hydroxyapatite to provide integration capability by subchondral bones and fix the hydrogel at cartilage defect without a need for suturing. The other phase differentiates the rabbit adipogenic mesenchymal stem cells (MSCs) towards soft tissue. Rheomechanical spectrometry (RMS) was employed to study the kinetic of the gelation including induction time and rate, as well as to measure the ultimate elastic modulus of the optimum crosslinked hydrogel. Surface tension measurement was also performed to tailor the surface characteristics of the gels. In vitro culturing of the cells inside the crosslinked hydrogel revealed high viability and high differentiation of the encapsulated rabbit stem cells, providing that the chromium acetate level was kept below 0.2 wt%. Based on the obtained results, the designed and fabricated biphasic hydrogel exhibited high potential as carrier for the stem cells for cartilage tissue engineering application

  8. The deoxyribonucleic acid of Micrococcus radiodurans

    PubMed Central

    Schein, Arnold H.

    1966-01-01

    The DNA of Micrococcus radiodurans was prepared by three methods. Although the recovery of DNA varied considerably, the percentage molar base ratios of the DNA from the three preparations were essentially the same: guanine, 33±2; adenine, 18±1; cytosine, 33±2; thymine, 17±1. Base compositions calculated from Tm values and from density in caesium chloride gradients also yielded guanine+cytosine contents of 66 and 68% of total bases respectively. No unusual bases were observed. The S20,w values were characteristic of high-molecular-weight DNA. Electron microscopy showed the purified DNA in long strands; occasionally these were coiled. Images(a)(b)(c)(d)(e)Fig. 1. PMID:16742439

  9. Enhanced cytoplasmic delivery of siRNA using a stabilized polyion complex based on PEGylated nanogels with a cross-linked polyamine structure.

    PubMed

    Tamura, Atsushi; Oishi, Motoi; Nagasaki, Yukio

    2009-07-13

    A novel siRNA delivery system using a polyion complex (PIC) based on PEGylated polyamine nanogels composed of a chemically cross-linked poly[2-(N,N-diethylaminoethyl)methacrylate] (PDEAMA) core and surrounded by PEG tethered chains is described. The nanogel formed PIC spontaneously through electrostatic interaction upon mixing with siRNA. The nanogel/siRNA complex was characterized by a gel retardation assay, size and ζ-potential measurements, and gene silencing activity using a cultured cell line. The nanogel/siRNA complexes showed higher polyanion exchange tolerability compared with the noncross-linked PEG-b-PDEAMA/siRNA complexes, indicating that the three-dimensionally cross-linked structure of the nanogel enhanced the stability of the PIC. Furthermore, the nanogel/siRNA complex was observed to undergo a remarkable enhancement of the gene silencing activity against the firefly luciferase gene expressed in HuH-7 cells at low N/P ratios (N/P = 2), whereas the noncross-linked PEG-b-PDEAMA/siRNA complexes showed negligible gene silencing activity. Moreover, confocal fluorescence microscopy revealed an efficient endosomal escape capability for the transportation of siRNAs into the cytoplasm, presumably due to the buffering effect of the PDEAMA core. Therefore, the PIC of siRNA with cross-linked polyamine nanogel is a potentially effective siRNA carrier for the development of in vivo therapeutic applications of siRNA. PMID:19505137

  10. Mechanical and structural response of a hybrid hydrogel based on chitosan and poly(vinyl alcohol) cross-linked with epichlorohydrin for potential use in tissue engineering.

    PubMed

    Garnica-Palafox, I M; Sánchez-Arévalo, F M; Velasquillo, C; García-Carvajal, Z Y; García-López, J; Ortega-Sánchez, C; Ibarra, C; Luna-Bárcenas, G; Solís-Arrieta, L

    2014-01-01

    The development and characterization of a hybrid hydrogel based on chitosan (CS) and poly(vinyl alcohol) (PVA) chemically cross-linked with epichlorohydrin (ECH) is presented. The mechanical response of these hydrogels was evaluated by uniaxial tensile tests; in addition, their structural properties such as average molecular weight between cross-link points (Mcrl), mesh size (DN), and volume fraction (v(s)) were determined. This was done using the equivalent polymer network theory in combination with the obtained results from tensile and swelling tests. The films showed Young's modulus values of 11 ± 2 MPa and 9 ± 1 MPa for none irradiated and ultraviolet (UV) irradiated hydrogels, respectively. The cell viability was assessed using Calcein AM and Ethidium homodimer-1 assay and environmental scanning electron microscopy. The 1-(4,5-dimethylthiazol-2-yl)-3,5-diphenylformazan thiazolyl blue formazan (MTT Formazan assay) results did not show cytotoxic effects; this was in good agreement with nuclear magnetic resonance and fourier transform infrared spectroscopies; their results did not show traces of ECH. This indicated that after the crosslinking process, there was no free ECH; furthermore, any possibility of ECH release in the construct during cell culture was discarded. The CS-PVA-ECH hybrid hydrogel allowed cell growth and extracellular matrix formation and showed adequate mechanical, structural, and biological properties for potential use in tissue engineering applications. PMID:24007370

  11. Novel Crosslinked Graft Copolymer of Methacrylic Acid and Collagen as a Protein-Based Superabsorbent Hydrogel with Salt and Ph-Responsiveness Properties

    NASA Astrophysics Data System (ADS)

    Sadeghi, Mohammad; Hamzeh, Alireza

    2008-08-01

    In this paper, a novel protein-based superabsorbent hydrogel was synthesized through crosslinking graft copolymerization of methacrylic acid (MAA) onto collagen, using ammonium persulfate (APS) as a free radical initiator in the presence of methylenebisacrylamide (MBA) as a crosslinker. The hydrogel structure was confirmed using FTIR spectroscopy. We were systematically optimized the certain variables of the graft copolymerization (i.e. the monomer, the initiator, and the crosslinker concentration) to achieve a hydrogel with maximum swelling capacity. Under the optimized conditions concluded, maximum capacity of swelling in distilled water was found to be 415 g/g. The swelling kinetics of the synthesized hydrogels with various particle sizes was preliminarily investigated. Absorbency in aqueous chloride salt solutions indicated that the swelling capacity decreased with an increase in the ionic strength of the swelling medium. The swelling of superabsorbing hydrogels was also measured in solutions with pH ranged from 1 to 13. The synthesized hydrogel exhibited a pH-responsiveness character so that a swelling-collapsing pulsatile behavior was recorded at pHs 2 and 7. This behavior makes the synthesized hydrogels as an excellent candidate for controlled delivery of bioactive agents.

  12. Comparison of 1-Ethyl-3-(3-Dimethylaminopropyl) Carbodiimide Based Strategies to Crosslink Antibodies on Amine-Functionalized Platforms for Immunodiagnostic Applications.

    PubMed

    Vashist, Sandeep Kumar

    2012-01-01

    1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) alone, and in combination with N-hydroxysuccinimide (NHS) or sulfoNHS were employed for crosslinking anti-human fetuin A (HFA) antibodies on 3-aminopropyltriethoxysilane (APTES)-functionalized surface plasmon resonance (SPR) gold chip and 96-well microtiter plate. The SPR immunoassay and sandwich enzyme linked immunosorbent immunoassay (ELISA) for HFA clearly demonstrated that EDC crosslinks anti-HFA antibodies to APTES-functionalized bioanalytical platforms more efficiently than EDC/NHS and EDC/sulfoNHS at a normal pH of 7.4. Similar results were obtained by sandwich ELISAs for human Lipocalin-2 and human albumin, and direct ELISA for horseradish peroxidase. The more efficient crosslinking of antibodies by EDC to the APTES-functionalized platforms increased the cost-effectiveness and analytical performance of our immunoassays. This study will be of wide interest to researchers developing immunoassays on APTES-functionalized platforms that are being widely used in biomedical diagnostics, biosensors, lab-on-a-chip and point-of-care-devices. It stresses a critical need of an intensive investigation into the mechanisms of EDC-based amine-carboxyl coupling under various experimental conditions. PMID:26859395

  13. The development of non-toxic ionic-crosslinked chitosan-based microspheres as carriers for the controlled release of silk sericin.

    PubMed

    Aramwit, Pornanong; Ekasit, Sanong; Yamdech, Rungnapha

    2015-10-01

    Silk sericin is recently shown to possess various biological activities for biomedical applications. While various sericin carriers were developed for drug delivery system, very few researches considered sericin as a bioactive molecule itself. In this study, sericin incorporated in the chitosan-based microspheres was introduced as a bioactive molecule and bioactive carrier at the same time. The chitosan/sericin (CH/SS) microspheres at different composition (80/20, 70/30, 60/40, and 50/50) were successfully fabricated using anhydroustri-polyphosphate (TPP) as a polyanionic crosslinker. The microspheres with an average size of 1-4 μm and narrow size distribution were obtained. From FT-IR spectra, the presence of both chitosan and sericin in the microspheres confirmed the occurrence of ionic interaction that crosslink them within the microspheres. We also found that the CH/SS microspheres prepared at 50/50 could encapsulate sericin at the highest percentage (37.28%) and release sericin in the most sustained behavior, possibly due to the strong ionic interaction of the positively charged chitosan and the negatively charged sericin. On the other hand, the composition of CH/SS had no effect on the degradation rate of microspheres. All microspheres continuously degraded and remained around 20% after 14 days of enzymatic degradation. This explained that the ionic crosslinkings between chitosan and sericin could be demolished by the enzyme and hydrolysis. Furthermore, we have verified that all CH/SS microspheres at any concentrations showed non-toxicity to L929 mouse fibroblast cells. Therefore, we suggested that the non-toxic ionic-crosslinked CH/SS microspheres could be incorporated in wound dressing material to achieve the sustained release of sericin for accelerated wound healing. PMID:26233725

  14. Synthesis and characterization of polyvinyl alcohol copolymer/phosphomolybdic acid-based crosslinked composite polymer electrolyte membranes

    NASA Astrophysics Data System (ADS)

    Anis, Arfat; Banthia, A. K.; Bandyopadhyay, S.

    Polymer electrolyte membrane fuel cells (PEMFCs) are very promising as future energy source due to their high-energy conversion efficiency and will help to solve the environmental concerns of energy production. Polymer electrolyte membrane (PEM) is recognised as the key element for an efficient PEMFC. Chemically crosslinked composite membranes consisting of a poly(vinyl alcohol-co-vinyl acetate-co-itaconic acid) (PVACO) and phosphomolybdic acid (PMA) have been prepared by solution casting and evaluated as proton conducting polymer electrolytes. The proton conductivity of the membranes is investigated as a function of PMA composition, crosslinking density and temperature. The membranes have also been characterized by FTIR spectroscopy, TGA, AFM and TEM. The proton conductivity of the composite membranes is of the order of 10 -3 S cm -1 and shows better resistance to methanol permeability than Nafion 117 under similar measurement conditions.

  15. Preparation, characterization and protein sorption of photo-crosslinked cell membrane-mimicking chitosan-based hydrogels.

    PubMed

    Zhao, Yunfei; Ma, Liubo; Zeng, Rong; Tu, Mei; Zhao, Jianhao

    2016-10-20

    Photocrosslinkable biomimetic chitosan derivative, glycidyl methacrylate-phosphorylcholine-chitosan (PCCs-GMA) was synthesized through the combination of Atherton-Todd reaction for coupling phosphorylcholine and ring opening reaction of epoxides for attaching GMA, and confirmed by (1)H and (31)P NMR and Fourier transform infrared (FTIR) spectroscopy. The photo-crosslinking reaction of PCCs-GMA with different degree of substitution (DS) of GMA allowed the formation of biomimetic hydrogels with tunable mechanical and swelling properties. Cold crystallization behaviors ascribed to their restrained freezing bound water were investigated using differential scanning calorimetry (DSC). The rheological and swelling behaviors, hemolysis as well as protein sorption of PCCs-GMA hydrogels were investigated in terms of the DS of GMA, using fibrinogen, bovine serum albumin and lysozyme as model proteins. Low irreversible protein sorption and non hemolytic results indicated that photo-crosslinked PCCs-GMA hydrogels may offer a promising candidate material with resistance to protein fouling in biomedical applications. PMID:27474563

  16. Induction of cellular deoxyribonucleic acid synthesis in butyrate-treated cells by simian virus 40 deoxyribonucleic acid

    SciTech Connect

    Kawasaki, S.; Diamond, L.; Baserga, R.

    1981-11-01

    Sodium butyrate (3mM) inhibited the entry into the S phase of quiescent 3T3 cells stimulated by serum, but had no effect on the accumulation of cellular ribonucleic acid. Simian virus 40 infection or manual microinjection of cloned fragments from the simian virus 40 A gene caused quiescent 3T3 cells to enter the S phase even in the presence of butyrate. NGI cells, a line of 3T3 cells transformed by simian virus 40, grew vigorously in 3 mM butyrate. Homokaryons were formed between G/sub 1/ and S-phase 3T3 cells. Butyrate inhibited the induction of deoxyribonucleic acid synthesis that usually occurs in G/sub 1/ nuclei when G/sub 1/ cells are fused with S-phase cells. However, when G/sub 1/ 3T3 cells were fused with exponentially growing NGI cells, the 3T3 nuclei were induced to enter deoxyribonucleic acid synthesis. In tsAF8 cells, a ribonucleic acid polymerase II mutant that stops in the G/sub 1/ phase of the cell cycle, no temporal sequence was demonstrated between the butyrate block and the temperature-sensitive block. These results confirm previous reports that certain virally coded proteins can induce cell deoxyribonucleic acid synthesis in the absence of cellular functions that are required by serum-stimulated cells. The author's interpretation of these data is that butyrate inhibited cell growth by inhibiting the expression of genes required for the G/sub o/ ..-->.. G/sub 1/ ..-->.. S transition and that the product of the simian virus 40 A gene overrode this inhibition by providing all of the necessary functions for the entry into the S phase.

  17. A novel positively charged membrane based on polyamide thin-film composite made by cross-linking for nanofiltration.

    PubMed

    Akbari, Ahmad; Fakharshakeri, Zahra; Mojallali Rostami, Sayed Majid

    2016-01-01

    In this paper, a novel positively charged membrane was prepared through interfacial polymerization technique between polyethyleneimine in aqueous phase and trimesoyl chloride in organic phase. Next, cross-linking of polyamide (PA) layer using ρ-xylylene dichloride (XDC) and glutaraldehyde (GA) was studied. The influences of cross-linking concentrations on the separation and permeation performance of membrane were also investigated. Membranes were characterized in terms of their chemical structure, the cross-sectional and surface morphologies, contact angles, molecular weight cut-off (MWCO) and effect of pH feed solution. The salt rejection sequence of CaCl2 >NaCl > Na2SO4 showed a positive charge at the membrane surface after cross-linking reaction. The MWCO of primary PA membrane decreased from 1,135 to 775 and 885 Da for XDC and GA, respectively. XDC membrane shows highest CaCl2 divalent cationic rejection (95.5%) and lowest water flux (21.1 L/m(2).h). This study illustrates a promising method for fabrication of positively charged membrane in cation separation. PMID:26901720

  18. Preparation of robust biocatalyst based on cross-linked enzyme aggregates entrapped in three-dimensionally ordered macroporous silica.

    PubMed

    Jiang, Yanjun; Shi, Lianlian; Huang, Yan; Gao, Jing; Zhang, Xu; Zhou, Liya

    2014-02-26

    With the aim to provide a highly stable and active biocatalyst, cross-linked enzyme aggregates (CLEAs) of lipase Candida sp. 99-125 were prepared in three-dimensionally ordered macroporous silica materials (CLEAs-LP@3DOM-SiO2). Lipase Candida sp. 99-125 was first precipitated in the pores of 3DOM SiO2 (named EAs-LP@3DOM-SiO2), and further cross-linked by glutaraldehyde to form CLEAs-LP@3DOM-SiO2. Saturated ammonium sulfate was used as a precipitant and glutaraldehyde with a concentration of 0.25% (w/w) was employed as a cross-linker. Compared with EAs-LP@3DOM-SiO2 and native lipase, CLEAs-LP@3DOM-SiO2 exhibited excellent thermal and mechanical stability, and could maintain more than 85% of initial activity after 16 days of shaking in organic and aqueous phase. When CLEAs-LP@3DOM-SiO2 was applied in esterification and transesterification reactions, improved activity and reusability were achieved. This method can be used for the immobilization of other enzymes of interest. PMID:24484443

  19. PEG-detachable and acid-labile cross-linked micelles based on orthoester linked graft copolymer for paclitaxel release

    NASA Astrophysics Data System (ADS)

    Yuan, Zhefan; Huang, Jingyi; Liu, Jing; Cheng, Sixue; Zhuo, Renxi; Li, Feng

    2011-08-01

    Polyethylene glycol detachable graft copolymer, mPEG-g-p(NAS-co-BMA), was synthesized by grafting 2-(ω-methoxy)PEGyl-1,3-dioxan-5-ylamine onto poly(N-(acryloyloxy)succinimide-co-butyl methacrylate). Pseudo in situ cross-linking of the mPEG-g-p(NAS-co-BMA) was performed in dimethylformamide phosphate buffer (v/v = 1/1) by an acid-labile diamine cross-linker bearing two symmetrical cyclic orthoesters. The cross-linked (CL) micelles with different contents of mPEG segments represented different morphologies. The CL micelles containing approximately one mPEG segment exhibited 'echini' morphology whereas the CL micelle with approximately three mPEG segments formed nanowires. The hydrolysis rate of the CL micelles is highly pH-dependent and much more rapid at mild acid than physiological conditions. Hydrolyzates of the CL micelles formed vesicles because new amphiphilic copolymers were formed. Paclitaxel (PTX) was successfully loaded into the CL micelles and a controlled and pH-dependent release behavior was observed. No obvious cytotoxicity was found for the CL micelles at concentration as high as 800 mg l - 1.

  20. Polyamines in the Synthesis of Bacteriophage Deoxyribonucleic Acid. I. Lack of Dependence of Polyamine Synthesis on Bacteriophage Deoxyribonucleic Acid Synthesis

    PubMed Central

    Dion, Arnold S.; Cohen, Seymour S.

    1972-01-01

    To determine whether polyamine synthesis is dependent on deoxyribonucleic acid (DNA) synthesis, polyamine levels were estimated after infection of bacterial cells with ultraviolet-irradiated T4 or T4 am N 122, a DNA-negative mutant. Although phage DNA accumulation was restricted to various degrees in comparison to cells infected with T4D, nearly commensurate levels of putrescine and spermidine synthesis were observed after infection, regardless of the rate of phage DNA synthesis. We conclude from these data that polyamine synthesis after infection is independent of phage DNA synthesis. PMID:4552549

  1. Incorporation of Deoxyribonucleic Acid Precursors by T4 Deoxyribonucleic Acid-Protein Complexes Retained on Glass Fiber Filters

    PubMed Central

    Miller, Robert C.; Kozinski, Andrzej W.

    1970-01-01

    Bacteriophage T4 deoxyribonucleic acid (DNA)-protein complexes were retained preferentially on glass fiber filters. DNA polymerase activity in the complex was detected through the incorporation of 3H-labeled DNA precursors. The primer-product DNA hybridized with both phage and Escherichia coli DNA. Density labeling experiments showed that about 30% of incorporated 3H-deoxyadenosine triphosphate was found in DNA which hybridized with phage DNA; this DNA was found to be covalently attached to the primer DNA. PMID:5497903

  2. Nucleotide `maps' of digests of deoxyribonucleic acid

    PubMed Central

    Murray, K.

    1970-01-01

    Various digests of 32P-labelled DNA were examined by two-dimensional ionophoresis on cellulose acetate and DEAE-cellulose paper. The products from digestion with pancreatic deoxyribonuclease and Neurospora crassa endonuclease were qualitatively closely similar, but very complex, and were used to investigate the mapping behaviour of nucleotides in various ionophoretic systems. Ionophoresis on DEAE-cellulose paper in triethylamine carbonate, pH 9.7, followed by ionophoresis in the second dimension at pH1.9 gave high resolution of nucleotides in very complex mixtures and permitted the fractionation of larger quantities than is possible on cellulose acetate. High resolution of nucleotides in compact spots was obtained with two-dimensional ionophoresis on cellulose acetate and AE-cellulose paper, a system that is a useful supplement to those based on DEAE-cellulose paper. ImagesPLATE 7PLATE 1PLATE 2PLATE 3PLATE 4PLATE 5PLATE 6 PMID:5476726

  3. Development of a glucose oxidase-based biocatalyst adopting both physical entrapment and crosslinking, and its use in biofuel cells

    NASA Astrophysics Data System (ADS)

    Chung, Yongjin; Ahn, Yeonjoo; Christwardana, Marcelinus; Kim, Hansung; Kwon, Yongchai

    2016-04-01

    New enzymatic catalysts prepared using physical entrapment and chemical bonding were used as anodic catalysts to enhance the performance of enzymatic biofuel cells (EBCs). For estimating the physical entrapment effect, the best glucose oxidase (GOx) concentration immobilized on polyethyleneimine (PEI) and carbon nanotube (CNT) (GOx/PEI/CNT) was determined, while for inspecting the chemical bonding effect, terephthalaldehyde (TPA) and glutaraldehyde (GA) crosslinkers were employed. According to the enzyme activity and XPS measurements, when the GOx concentration is 4 mg mL-1, they are most effectively immobilized (via the physical entrapment effect) and TPA-crosslinked GOx/PEI/CNT(TPA/[GOx/PEI/CNT]) forms π conjugated bonds via chemical bonding, inducing the promotion of electron transfer by delocalization of electrons. Due to the optimized GOx concentration and π conjugated bonds, TPA/[GOx/PEI/CNT], including 4 mg mL-1 GOx displays a high electron transfer rate, followed by excellent catalytic activity and EBC performance.New enzymatic catalysts prepared using physical entrapment and chemical bonding were used as anodic catalysts to enhance the performance of enzymatic biofuel cells (EBCs). For estimating the physical entrapment effect, the best glucose oxidase (GOx) concentration immobilized on polyethyleneimine (PEI) and carbon nanotube (CNT) (GOx/PEI/CNT) was determined, while for inspecting the chemical bonding effect, terephthalaldehyde (TPA) and glutaraldehyde (GA) crosslinkers were employed. According to the enzyme activity and XPS measurements, when the GOx concentration is 4 mg mL-1, they are most effectively immobilized (via the physical entrapment effect) and TPA-crosslinked GOx/PEI/CNT(TPA/[GOx/PEI/CNT]) forms π conjugated bonds via chemical bonding, inducing the promotion of electron transfer by delocalization of electrons. Due to the optimized GOx concentration and π conjugated bonds, TPA/[GOx/PEI/CNT], including 4 mg mL-1 GOx displays a high

  4. MS-based cross-linking analysis reveals the location of the PsbQ protein in cyanobacterial photosystem II

    PubMed Central

    Liu, Haijun; Zhang, Hao; Weisz, Daniel A.; Vidavsky, Ilan; Gross, Michael L.; Pakrasi, Himadri B.

    2014-01-01

    PsbQ is a luminal extrinsic protein component that regulates the water splitting activity of photosystem II (PSII) in plants, algae, and cyanobacteria. However, PsbQ is not observed in the currently available crystal structures of PSII from thermophilic cyanobacteria. The structural location of PsbQ within the PSII complex has therefore remained unknown. Here, we report chemical cross-linking followed by immunodetection and liquid chromatography/tandem MS analysis of a dimeric PSII complex isolated from the model cyanobacterium, Synechocystis sp. PCC 6803, to determine the binding site of PsbQ within PSII. Our results demonstrate that PsbQ is closely associated with the PsbO and CP47 proteins, as revealed by cross-links detected between 120K of PsbQ and 180K and 59K of PsbO, and between 102K of PsbQ and 440D of CP47. We further show that genetic deletion of the psbO gene results in the complete absence of PsbQ in PSII complexes as well as the loss of the dimeric form of PSII. Overall, our data provide a molecular-level description of the enigmatic binding site of PsbQ in PSII in a cyanobacterium. These results also help us understand the sequential incorporation of the PsbQ protein during the PSII assembly process, as well as its stabilizing effect on the oxygen evolution activity of PSII. PMID:24550459

  5. Selective formation of organo, organo-aqueous, and hydro gel-like materials from partially hydrolysed poly(vinyl acetate)s based on different boron-containing crosslinkers.

    PubMed

    Angelova, L V; Leskes, M; Berrie, B H; Weiss, R G

    2015-07-01

    Viscoelastic, gel-like, polymeric dispersions (HVPDs) can be prepared by crosslinking polyols with borax or boric acid in water under alkaline conditions. Rheologically similar HVPDs have been prepared in organic liquids containing no water or hydroxylic groups through crosslinking partially or fully hydrolysed poly(vinyl acetate)s with trimethyl borate, boric acid, or borax. The organo-HVPDs are water-sensitive and rheoreversible on exposure to water. They were characterised rheologically and by solution and solid-state (11)B NMR spectroscopy. Spectroscopic analyses show the presence of mono- and di-diol crosslinks, as well as non-crosslinked boron species in HVPDs prepared with trimethyl borate or boric acid. The number of crosslinks in organo-HVPDs prepared with borax increased over the course of several days. Results from solution and solid-state (11)B NMR spectroscopy are comparable; no solid-like component was detectable. We demonstrate that hydro, organo, or organo-aqueous HVPDs can be obtained from partially hydrolysed poly(vinyl acetate)s by 'tuning' the structure of the boron-based crosslinker. PMID:26027551

  6. Desmosine-Inspired Cross-Linkers for Hyaluronan Hydrogels

    NASA Astrophysics Data System (ADS)

    Hagel, Valentin; Mateescu, Markus; Southan, Alexander; Wegner, Seraphine V.; Nuss, Isabell; Haraszti, Tamás; Kleinhans, Claudia; Schuh, Christian; Spatz, Joachim P.; Kluger, Petra J.; Bach, Monika; Tussetschläger, Stefan; Tovar, Günter E. M.; Laschat, Sabine; Boehm, Heike

    2013-06-01

    We designed bioinspired cross-linkers based on desmosine, the cross-linker in natural elastin, to prepare hydrogels with thiolated hyaluronic acid. These short, rigid cross-linkers are based on pyridinium salts (as in desmosine) and can connect two polymer backbones. Generally, the obtained semi-synthetic hydrogels are form-stable, can withstand repeated stress, have a large linear-elastic range, and show strain stiffening behavior typical for biopolymer networks. In addition, it is possible to introduce a positive charge to the core of the cross-linker without affecting the gelation efficiency, or consequently the network connectivity. However, the mechanical properties strongly depend on the charge of the cross-linker. The properties of the presented hydrogels can thus be tuned in a range important for engineering of soft tissues by controlling the cross-linking density and the charge of the cross-linker.

  7. Intermediates in the Synthesis of Type 2 Adenovirus Deoxyribonucleic Acid

    PubMed Central

    Horwitz, Marshall S.

    1971-01-01

    Intermediates in the synthesis of adenovirus type 2 deoxyribonucleic acid (DNA) were studied in HeLa cells. Pieces of DNA smaller than the viral genome were demonstrated after labeling with 3H-thymidine for 10 to 240 sec. Intermediates as small as the Okazaki fragments (8 to 10S) do not predominate at any of the above times. No detectable addition of nucleotides to parental genome could be shown, nor was there any breakdown of recently synthesized viral DNA. The DNA intermediates were of viral origin for they hybridized to viral DNA and were made at a stage of the cell cycle (G2) when host DNA is not synthesized. PMID:5132696

  8. Studies on Resistance Transfer Factor Deoxyribonucleic Acid in Escherichia coli

    PubMed Central

    Silver, Richard P.; Falkow, Stanley

    1970-01-01

    A variant of the derepressed R factor, R1, which does not contain any of the drug resistance markers, and represents, in large part, the resistance transfer factor (RTF) was studied in Escherichia coli. RTF deoxyribonucleic acid (DNA) was specifically labeled in a female cell after conjugation. Physical characterization of the molecule showed that RTF possessed an average molecular weight of 50 × 106 daltons and a buoyant density of 1.709 g/cm3. By comparison to R1, we calculate that the region of DNA carrying the drug resistance genes is therefore about 20% of the R1 molecule and has a buoyant density of approximately 1.716 g/cm3. These results support the hypothesis that the single species of R-factor DNA observed in E. coli represents a composite of the 1.709 and 1.716 g/cm3 replicons seen in Proteus. PMID:4919749

  9. Electrical conduction in macroscopically oriented deoxyribonucleic and hyaluronic acid samples

    NASA Astrophysics Data System (ADS)

    Kutnjak, Zdravko; Lahajnar, Gojmir; Filipič, Cene; Podgornik, Rudolf; Nordenskiöld, Lars; Korolev, Nikolay; Rupprecht, Allan

    2005-04-01

    Measurements of the quasistatic and frequency dependent electrical conductivity below 1 MHz were carried out on wet-spun, macroscopically oriented, calf thymus deoxyribonucleic (DNA) and umbilical cord hyaluronic acid (HA) bulk samples. The frequency dependence of the electrical conductivity in the frequency range of approximately 10-3-106Hz of both materials is surprisingly rather similar. Temperature dependence of the quasistatic electrical conductivity above the low temperature saturation plateau can be well described by the activated Arrhenius law with the activation energy of ≈0.8eV for both DNA and HA. We discuss the meaning of these findings for the possible conduction mechanism in these particular charged polyelectrolytes.

  10. Specific Initiation Site for Simian Virus 40 Deoxyribonucleic Acid Replication

    PubMed Central

    Thoren, Marilyn M.; Sebring, Edwin D.; Salzman, Norman P.

    1972-01-01

    Replicating simian virus 40 (SV40) deoxyribonucleic acid (DNA) molecules have been isolated under conditions in which the newly synthesized DNA is uniformly labeled with 3H-thymidine. These newly synthesized strands are released from the replicative intermediate molecules by alkaline treatment, and it has been possible to isolate single-stranded SV40 DNA which varies in size from 157,000 daltons (from molecules that are 10% replicated) to 1,360,000 daltons (85% replicated). The rates of duplex formation of newly synthesized DNA have been used to relate their genetic complexity to the extent of DNA replication. As DNA replication proceeds, the time required to effect 50% renaturation of the newly synthesized DNA increases at a proportional rate. The data establish that DNA replication is not initiated at random, but rather that there is a single specific initiation site for DNA replication. PMID:4342054

  11. Origin and Direction of Simian Virus 40 Deoxyribonucleic Acid Replication

    PubMed Central

    Fareed, George C.; Garon, Claude F.; Salzman, Norman P.

    1972-01-01

    Double-branched, circular, replicating deoxyribonucleic acid (DNA) molecules of simian virus 40 (SV40) have been cleaved by the R1 restriction endonuclease from Escherichia coli. This enzyme introduces one double-strand break in SV40 DNA, at a specific site. The site of cleavage in the replicating molecules was used in this study to position the origin and the two branch points. Radioactively labeled molecules fractionated according to their extent of replication were evaluated after cleavage by sedimentation analysis and electron microscopy. The results demonstrate that the R1 cleavage site is 33% of the genome length from the origin of replication and that both branch points are growing points. These data indicate that SV40 DNA replication is bidirectional and confirm other reports which have shown a unique origin of replication. Images PMID:4342055

  12. Role of deoxyribonucleic acid technology in forensic dentistry

    PubMed Central

    Datta, Pankaj; Datta, Sonia Sood

    2012-01-01

    In the last few years, Deoxyribonucleic Acid (DNA) analysis methods have been applied to forensic cases. Forensic dental record comparison has been used for human identification in cases where destruction of bodily tissues or prolonged exposure to the environment has made other means of identification impractical, that is, after fire exposure or mass disaster. Teeth play an important role in identification and criminology, due to their unique characteristics and relatively high degree of physical and chemical resistance. The use of a DNA profile test in forensic dentistry offers a new perspective in human identification. The DNA is responsible for storing all the genetic material and is unique to each individual. The currently available DNA tests have high reliability and are accepted as legal proofs in courts. This article gives an overview of the evolution of DNA technology in the last few years, highlighting its importance in cases of forensic investigation. PMID:23087582

  13. Simian Virus 40 Deoxyribonucleic Acid Synthesis: Analysis by Gel Electrophoresis

    PubMed Central

    Tegtmeyer, Peter; Macasaet, Francisco

    1972-01-01

    An agarose-gel electrophoresis technique has been developed to study simian virus 40 deoxyribonucleic acid (DNA) synthesis. Superhelical DNA I, relaxed DNA II, and replicative intermediate (RI) molecules were clearly resolved from one another for analytical purposes. Moreover, the RI molecules could be identified as early or late forms on the basis of their electrophoretic migration in relation to that of DNA II. The technique has been utilized to study the kinetics of simian virus 40 DNA synthesis in pulse and in pulse-chase experiments. The average time required to complete the replication of prelabeled RI molecules and to convert them into DNA I was approximately 10 min under the experimental conditions employed. PMID:4343542

  14. Synthesis, Characterization, and Cross-Linking Strategy of a Quercetin-Based Epoxidized Monomer as a Naturally-Derived Replacement for BPA in Epoxy Resins.

    PubMed

    Kristufek, Samantha L; Yang, Guozhen; Link, Lauren A; Rohde, Brian J; Robertson, Megan L; Wooley, Karen L

    2016-08-23

    The natural polyphenolic compound quercetin was functionalized and cross-linked to afford a robust epoxy network. Quercetin was selectively methylated and functionalized with glycidyl ether moieties using a microwave-assisted reaction on a gram scale to afford the desired monomer (Q). This quercetin-derived monomer was treated with nadic methyl anhydride (NMA) to obtain a cross-linked network (Q-NMA). The thermal and mechanical properties of this naturally derived network were compared to those of a conventional diglycidyl ether bisphenol A-derived counterpart (DGEBA-NMA). Q-NMA had similar thermal properties [i.e., glass transition (Tg ) and decomposition (Td ) temperatures] and comparable mechanical properties (i.e., Young's Modulus, storage modulus) to that of DGEBA-NMA. However, it had a lower tensile strength and higher flexural modulus at elevated temperatures. The application of naturally derived, sustainable compounds for the replacement of commercially available petrochemical-based epoxies is of great interest to reduce the environmental impact of these materials. Q-NMA is an attractive candidate for the replacement of bisphenol A-based epoxies in various specialty engineering applications. PMID:27415143

  15. Solvent- and phase-controlled photochirogenesis. Enantiodifferentiating photoisomerization of (Z)-cyclooctene sensitized by cyclic nigerosylnigerose-based nanosponges crosslinked by pyromellitate.

    PubMed

    Wei, Xueqin; Liang, Wenting; Wu, Wanhua; Yang, Cheng; Trotta, Francesco; Caldera, Fabrizio; Mele, Andrea; Nishimoto, Tomoyuki; Inoue, Yoshihisa

    2015-03-14

    Cyclic nigerosylnigerose (CNN), a saucer-shaped cyclic tetrasaccharide with a shallow concave surface, was reacted with pyromellitic dianhydride in 1:2 and 1:4 ratios to give two CNN-based polymers of different degrees of crosslinking, both of which swelled upon soaking in water, acting as a ‘nanosponge’ (NS). These NSs evolved several phases from isotropic solution to flowing and rigid gels via suspension by gradually increasing the concentration in water. The CNN-NSs thus prepared effectively mediated the enantiodifferentiating photoisomerization of (Z)-cyclooctene (1Z) to chiral (E)-isomer (1E). The enantiomeric excess (ee) of 1E obtained was a critical function of the solvent composition and the phase evolved at different CNN-NS concentrations in water. In isotropic solution, the enantioselectivity was generally low (−4% to +6% ee) but the chiral sense of 1E was inverted by increasing the methanol content. Interestingly, the product's ee was controlled more dramatically by the phase evolved, as was the case with the cyclodextrin-based nanosponge (CD-NS) reported previously. Thus, the ee of 1E was low in solution and suspension, but suddenly leaped at the phase border of flowing gel and rigid gel to give the highest ee of 22–24%, which are much higher than those obtained with CD-NSs (6–12% ee), revealing the positive roles of the chiral void space formed upon gelation of the crosslinked saccharide polymer. PMID:25582492

  16. Assistant deoxyribonucleic acid recycling with Zn(2+) and molecular beacon for electrochemical detection of deoxyribonucleic acid via target-triggered assembly of mutated DNAzyme.

    PubMed

    Qian, Yong; Wang, Chunyan; Gao, Fenglei

    2014-10-01

    A novel enzyme-free amplification strategy was designed for sensitive electrochemical detection of deoxyribonucleic acid (DNA) based on Zn(2+) assistant DNA recycling via target-triggered assembly of mutated DNAzyme. A gold electrode was used to immobilize molecular beacon (MB) as the recognition probe and perform the amplification procedure. In the presence of target DNA, the hairpin probe 1 was opened, and the DNAzyme was liberated from the caged structure. The activated DNAzyme first hybridized and then cleaved the MB in the presence of cofactor Zn(2+). After cleavage, the MB was cleaved into two pieces and the ferrocene (Fc) labeled piece dissociated from the gold electrode, thus obviously decreasing the Fc signal and forming a free DNAzyme strand. Finally, each target-induced activated DNAzyme underwent many cycles to trigger the cleavage of many MB substrates. Therefore, the peak current of Fc dramatically decreased to approximately zero. The strategy showed a detection limit at 35 fM levels, which was about 2 orders of magnitude lower than that of the conventional hybridization without Zn(2+)-based amplification. The Zn(2+) assistant DNA recycling offers a versatile platform for DNA detection in a cost-effective manner, and has a promising application in clinical diagnosis. PMID:25201265

  17. Corneal cross-linking.

    PubMed

    Randleman, J Bradley; Khandelwal, Sumitra S; Hafezi, Farhad

    2015-01-01

    Since its inception in the late 1990s, corneal cross-linking has grown from an interesting concept to a primary treatment for corneal ectatic disease worldwide. Using a combination of ultraviolet-A light and a chromophore (vitamin B2, riboflavin), the cornea can be stiffened, usually with a single application, and progressive thinning diseases such as keratoconus arrested. Despite being in clinical use for many years, some of the underlying processes, such as the role of oxygen and the optimal treatment times, are still being worked out. More than a treatment technique, corneal cross-links represent a physiological principle of connective tissue, which may explain the enormous versatility of the method. We highlight the history of corneal cross-linking, the scientific underpinnings of current techniques, evolving clinical treatment parameters, and the use of cross-linking in combination with refractive surgery and for the treatment of infectious keratitis. PMID:25980780

  18. [Crosslinking in Keratoconus].

    PubMed

    Lang, S J; Reinhard, T

    2016-06-01

    Keratoconus leads to progressive thinning and protrusion of the cornea. Young patients exhibit the highest risk for progression. Corneal crosslinking was introduced in 1998 and is intended to prevent progression of keratoconus. Only a few prospective controlled trials have been published. Six randomised controlled trials have been published. All these trials confirmed the efficacy of crosslinking through keratometric data. In two trials, progression was reported in some patients of the treatment group. This indicates that not all patients benefit from corneal crosslinking. The risks of the procedure include corneal scarring, haze, endothelial cell damage and infections of the cornea. In order to avoid these risks, patients without progression should not be treated with crosslinking. PMID:27315291

  19. Aliphatic polycarbonates based on carbon dioxide, furfuryl glycidyl ether, and glycidyl methyl ether: reversible functionalization and cross-linking.

    PubMed

    Hilf, Jeannette; Scharfenberg, Markus; Poon, Jeffrey; Moers, Christian; Frey, Holger

    2015-01-01

    Well-defined poly((furfuryl glycidyl ether)-co-(glycidyl methyl ether) carbonate) (P((FGE-co-GME)C)) copolymers with varying furfuryl glycidyl ether (FGE) content in the range of 26% to 100% are prepared directly from CO2 and the respective epoxides in a solvent-free synthesis. All materials are characterized by size-exclusion chromatography (SEC), (1)H NMR spectroscopy, and differential scanning calorimetry (DSC). The furfuryl-functional samples exhibit monomodal molecular weight distributions with Mw/Mn in the range of 1.16 to 1.43 and molecular weights (Mn) between 2300 and 4300 g mol(-1). Thermal properties reflect the amorphous structure of the polymers. Both post-functionalization and cross-linking are performed via Diels-Alder chemistry using maleimide derivatives, leading to reversible network formation. This transformation is shown to be thermally reversible at 110 °C. PMID:25407342

  20. Endonuclease from Micrococcus luteus which has activity toward ultraviolet-irradiated deoxyribonucleic acid: its action on transforming deoxyribonucleic acid.

    PubMed

    Setlow, R B; Setlow, J K; Carrier, W L

    1970-04-01

    An endonuclease purified from Micrococcus luteus makes single-strand breaks in ultraviolet (UV)-irradiated, native deoxyribonucleic acid (DNA). The purified endonuclease is able to reactivate UV-inactivated transforming DNA of Haemophilus influenzae, especially when the DNA is assayed on a UV-sensitive mutant of H. influenzae. After extensive endonuclease action, there is a loss of transforming DNA when assayed on both UV-sensitive and -resistant cells. The endonuclease does not affect unirradiated DNA. The results indicate that the endonuclease function is involved in the repair of biological damage resulting from UV irradiation and that the UV-sensitive mutant is deficient in this step. We interpret the data as indicating that the various steps in the repair of DNA must be well coordinated if repair is to be effective. PMID:4314478

  1. Disposable MMP-9 sensor based on the degradation of peptide cross-linked hydrogel films using electrochemical impedance spectroscopy.

    PubMed

    Biela, Anna; Watkinson, Michael; Meier, Ute C; Baker, David; Giovannoni, Gavin; Becer, C Remzi; Krause, Steffi

    2015-06-15

    Matrix metalloproteinase-9 (MMP-9) plays an important role in both physiological and pathological processes. This enzyme is a peripheral biomarker of neuroinflammation in multiple sclerosis (MS), a chronic autoimmune disease of the central nervous system. Presently, expensive magnetic resonance imaging (MRI) studies are used to monitor subclinical disease activity in MS. An alternative to costly MRI scans could be the detection of MMP-9, using a low-cost, disposable sensor system for MMP-9 suitable for home-monitoring of inflammation. This would allow an early prediction of the failure of anti-inflammatory therapies and more timely clinical intervention to limit neuronal damage and prevent disability. Herein we present the development of a disposable sensor for fast and straightforward detection of MMP-9. Biosensors were produced by coating electrodes with oxidized dextran and subsequent cross-linking with peptides containing specific cleavage sites for MMP-9. Exposure of the films to the enzyme resulted in the degradation of the films, which was monitored using impedance measurements. Sensor response was rapid, a significant impedance change was usually observed within 5 min after the addition of MMP-9. Sensors showed a negligible response to matrix metalloproteinase-2 (MMP-2), a protease which may interfere with MMP-9 detection. The peptide sequence with the highest sensitivity and selectivity Leu-Gly-Arg-Met-Gly-Leu-Pro-Gly-Lys was selected to construct calibration curves. MMP-9 was successfully detected in a clinically relevant range from 50 to 400 ng/ml. Two different processes of hydrogel degradation were observed on electrode surfaces with different roughness, and both appeared suitable to monitor MMP-9 activity. The sensor materials are generic and can be easily adopted to respond to other proteases by selecting peptide cross-linkers with suitable cleavage sites. PMID:25660510

  2. A TIPS-TPDO-tetraCN-Based n-Type Organic Field-Effect Transistor with a Cross-linked PMMA Polymer Gate Dielectric.

    PubMed

    Jung, Sungyeop; Albariqi, Mohammed; Gruntz, Guillaume; Al-Hathal, Thamer; Peinado, Alba; Garcia-Caurel, Enric; Nicolas, Yohann; Toupance, Thierry; Bonnassieux, Yvan; Horowitz, Gilles

    2016-06-15

    Recent improvement in the performance of the n-type organic semiconductors as well as thin gate dielectrics based on cross-linked polymers offers new opportunities to develop high-performance low-voltage n-type OFETs suitable for organic complementary circuits. Using TIPS-tetracyanotriphenodioxazine (TIPS-TPDO-tetraCN) and cross-linked poly(methyl methacrylate) (c-PMMA), respectively as n-type organic semiconductor and gate dielectric, linear regime field-effect mobility (1.8 ± 0.2) × 10(-2) cm(2) V(-1)s(-1), small spatial standard deviation of threshold voltage (∼0.1 V), and operating voltage less than 3 V are attainable with the same device structure and contact materials used commonly for p-type OFETs. Through comparative static and dynamic characterizations of c-PMMA and PMMA gate dielectrics, it is shown that both smaller thickness and larger relative permittivity of c-PMMA contributes to reduced operating voltage. Furthermore, negligible hysteresis brings evidence to small trap states in the semiconductor near gate dielectric of the n-type OFETs with c-PMMA. The use of TIPS-TPDO-tetraCN and c-PMMA is fully compatible with polyethylene terephthalate substrate, giving promise to various flexible applications. PMID:27188403

  3. Design of cross-linked semicrystalline poly(ε-caprolactone)-based networks with one-way and two-way shape-memory properties through Diels-Alder reactions.

    PubMed

    Raquez, Jean-Marie; Vanderstappen, Sophie; Meyer, Franck; Verge, Pierre; Alexandre, Michael; Thomassin, Jean-Michel; Jérôme, Christine; Dubois, Philippe

    2011-08-29

    Cross-linked poly(ε-caprolactone) (PCL)-based polyesterurethane (PUR) systems have been synthesized through Diels-Alder reactions by reactive extrusion. The Diels-Alder and retro-Diels-Alder reactions proved to be useful for enhancing the molecular motion of PCL-based systems, and therefore their crystallization ability, in the design of cross-linked semicrystalline polymers with one-way and two-way shape-memory properties. Successive reactions between α,ω-diol PCL (PCL(2) ), furfuryl alcohol, and methylene diphenyl 4,4'-diisocyanate straightforwardly afforded the α,ω-furfuryl PCL-based PUR systems, and subsequent Diels-Alder reactions with N,N-phenylenedimaleimide afforded the thermoreversible cycloadducts. The cross-linking density could be modulated by partially replacing PCL-diol with PCL-tetraol. Interestingly, the resulting PUR systems proved to be semicrystalline cross-linked polymers, the melting temperature of which (close to 45 °C) represented the switching temperature for their shape-memory properties. Qualitative and quantitative measurements demonstrated that these PUR systems exhibited one-way and two-way shape-memory properties depending on their cross-linking density. PMID:21744399

  4. Crosslinked poly(vinylbenzyl chloride) with a macromolecular crosslinker for anion exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Lu, Wangting; Shao, Zhi-Gang; Zhang, Geng; Zhao, Yun; Yi, Baolian

    2014-02-01

    A new material based on crosslinked poly(vinylbenzyl chloride) (PVBC) with a macromolecular crosslinker is synthesized and employed as the membrane for anion exchange membrane fuel cells (AEMFCs). PVBC is used as the hydroxide conducting polymers, while poly(vinyl acetal) (PVAc) containing dimethylamino groups plays the role as macromolecular crosslinker and the supporting matrix simultaneously. Fourier transform infrared (FT-IR) absorption spectra and X-ray photoelectron (XPS) spectra prove successful crosslinking between PVBC and PVAc. The crosslinked membrane shows hydroxide conductivity larger than 0.01 S cm-1 at room temperature, and the swelling by water at elevated temperature is suppressed. The H2/O2 AEMFC using the crosslinked membrane shows a peak power density (Pmax) of 124.7 mW cm-2 at 40 °C, and the decrease of the open circuit voltage (OCV) of the fuel cell is negligible under continuous OCV conditions for 120 h. All the results indicate that the crosslinking with a macromolecular crosslinker may be a promising strategy to fabricate anion exchange membrane for the application in the AEMFCs.

  5. Synergistic therapeutic effects of Schiff's base cross-linked injectable hydrogels for local co-delivery of metformin and 5-fluorouracil in a mouse colon carcinoma model.

    PubMed

    Wu, Xilong; He, Chaoliang; Wu, Yundi; Chen, Xuesi

    2016-01-01

    In situ formed hydrogels based on Schiff base reaction were formulated for the co-delivery of metformin (ME) and 5-fluorouracil (5FU). The reactive aldehyde-functionalized four-arm polyethylene glycol (PFA) was synthesized by end-capping of 4-arm PEG with 4-formylbenzoic acid (FA) and used as a cross-linking agent. The injectable hydrogels are designed through the quick gelation induced by the formation of covalent bonds via Schiff-base reaction of PFA with 4-arm poly (ethylene glycol)-b-poly (L-lysine) (PPLL). This formulation eliminated the need for metal catalysts and complicated processes in the preparation of in situ-forming hydrogels. In vitro degradation and drug release studies demonstrated that both ME and 5FU were released through PFA/PPLL hydrogels in a controlled and pH-dependent manner. When incubated with mouse colon adenocarcinoma cells (C26), the ME/5FU-incorporated PFA/PPLL hydrogels had synergistic inhibitory effects on the cell cycle progression and cell proliferation in colon cancer cells. After a single subcutaneous injection of the hydrogel containing ME/5FU beside the tumors of BALB/c mice inoculated with C26 cells, the dual-drug-loaded hydrogels displayed superior therapeutic activity resulted from a combination of p53-mediated G1 arrest and apoptosis in C26 cells. Hence, the Schiff's base cross-linked hydrogels containing ME and 5FU may have potential therapeutic applications in the treatments of colon cancer. PMID:26497429

  6. In vitro and in vivo evaluation of novel cross-linked saccharide based polymers as bile acid sequestrants.

    PubMed

    Lopez-Jaramillo, Francisco Javier; Giron-Gonzalez, Maria Dolores; Salto-Gonzalez, Rafael; Hernandez-Mateo, Fernando; Santoyo-Gonzalez, Francisco

    2015-01-01

    Bile acid sequestrants (BAS) represent a therapeutic approach for the management of hypercholesterolemia that relies on the cationic polymeric nature of BAS to selectively bind negatively charged bile acids. We hypothesized that the cross-linking of β-cyclodextrin (β-CD) and saccharides such as starch or dextrin with divinyl sulfone (DVS) yields homo- and hetero-polymeric materials with the ability to trap sterols. Our hypothesis was put to test by synthesizing a library of 22 polymers that were screened to evaluate their capability to sequester both cholesterol (CHOL) and cholic and deoxycholic acids (CA and DCA). Three polymers synthesized in high yield were identified as promising. Two were neutral hetero-polymers of β-CD and starch or dextrin and the third was a weakly cationic homo-polymer of starch, highlighting the importance of the cavity effect. They were tested in hypercholesterolemic male Wistar rats and their ability to regulate hypercholesterolemia was similar to that for the reference BAS cholestyramine, but with two additional advantages: (i) they normalized the TG level and (ii) they did not increase the creatinine level. Neither hepatotoxicity nor kidney injury was detected, further supporting them as therapeutical candidates to manage hypercholesterolemia. PMID:25719741

  7. Crosslink Mapping at Amino Acid-Base Resolution Reveals the Path of Scrunched DNA in Initial Transcribing Complexes.

    PubMed

    Winkelman, Jared T; Winkelman, Bradford T; Boyce, Julian; Maloney, Michael F; Chen, Albert Y; Ross, Wilma; Gourse, Richard L

    2015-09-01

    RNA polymerase binds tightly to DNA to recognize promoters with high specificity but then releases these contacts during the initial stage of transcription. We report a site-specific crosslinking approach to map the DNA path in bacterial transcription intermediates at amino acid and nucleotide resolution. After validating the approach by showing that the DNA path in open complexes (RPO) is the same as in high-resolution X-ray structures, we define the path following substrate addition in "scrunched" complexes (RPITC). The DNA bulges that form within the transcription bubble in RPITC are positioned differently on the two strands. Our data suggest that the non-template strand bulge is extruded into solvent in complexes containing a 5-mer RNA, whereas the template strand bulge remains within the template strand tunnel, exerting stress on interactions between the β flap, β' clamp, and σ3.2. We propose that this stress contributes to σ3.2 displacement from the RNA exit channel, facilitating promoter escape. PMID:26257284

  8. Preparation and characterization of highly cross-linked polyimide aerogels based on polyimide containing trimethoxysilane side groups.

    PubMed

    Pei, Xueliang; Zhai, Wentao; Zheng, Wenge

    2014-11-11

    In this study, highly cross-linked and completely imidized polyimide aerogels were prepared from polyimide containing trimethoxysilane side groups, which was obtained as the condensation product of polyimide containing acid chloride side groups and 3-aminopropyltrimethoxysilane. After adding water and acid catalyst, the trimethoxysilane side groups hydrolyzed and condensed one another, and a continuous increase in the complex viscosities of the polyimide solutions with time was observed. The formed polyimide gels were dried by freeze-drying from tert-butyl alcohol to obtain polyimide aerogels, which consisted of a three-dimensional network of polyimide fibers tangled together. By varying the solution concentration of the polyimide containing trimethoxysilane side groups, polyimide aerogels with different densities (ranging from 0.19 to 0.42 g/cm(3)) were obtained. The resulting polyimide aerogels had small pore diameter (ranging from 20.7 to 58.3 nm), high surface area (ranging from 310 to 344 m(2)/g), high 5% weight loss temperature in air (at about 440 °C), and an excellent mechanical property. In addition, the glass transition temperature (349 °C) of the polyimide aerogels was much higher than that (210 °C) of the corresponding linear polyimide. So, even after being heated at 300 °C for 30 min, the porous structure of the polyimide aerogels was not completely destroyed. PMID:25340747

  9. Cross-linked informofers.

    PubMed Central

    Prosvirnin, V V; Ruzidic, S; Samarina, O P

    1979-01-01

    The proteins of 30S RNP particles containing pre-mRNA (hnRNA) were cross-linked with bifunctional reagents (dimethyl-suberimidate and dimethyl-3,3'-dithiobispropionimidate). Further treatment with 1 or 2 M NaCl dissociates all RNA from protein. However, a significant part of protein particles--informofers being cross-linked survived high salt treatment. Their sedimentation coefficients were close to those of original particles. No RNA could be detected in the informofers even after labeling the cells with a precursor for a long period of time. Sodium dodecylsulfate or urea dissociated cross-linked informofers into oligomeric polypeptides. They could be dissociated by beta-mercaptoethanol treatment if a reversible cross-linked reagent had been used. The resulting polypeptides were represented by informatin. RNP particles (30S RNP or poly-particles) were reconstituted upon mixing of cross-linked informofers with pre-mRNA and removal of 2 M NaCl. PMID:503864

  10. Generation of Pretilt Angle for Nematic Liquid Crystal Using the Photodimerization Method on Various New Photo-Crosslinkable Polyimide Based Polymers

    NASA Astrophysics Data System (ADS)

    Hwang, Jeoung-Yeon; Seo, Dae-Shik; Son, Jong-Ho; Suh, Dong Hack

    2001-07-01

    We synthesized the various new photo-crosslinkable polyimide based polymers and generation of pretilt angle for a nematic liquid crystal (NLC) using a photodimerization method on the photopolymers was studied. A good thermal stability of the photopolymers was measured by thermogravimatric analysis (TGA) measurement until 450°C. The NLC pretilt angle generated was about 2.5°-3.0° by polarized UV exposure on the photopolymers containing a biphenyl (BP), decyl (De), and cholesteryl(chol), chalcone(Chal) group, respectively. However, low pretilt angle of the NLC was measured by polarized UV exposure on the photopolymers containing the fluorine and chalcone group. The NLC pretilt angle generated is attributed to the biphenyl and alkyl moieties, and the photo-dimerized chalcone group of the photopolymer.

  11. A Biosensor Based on Immobilization of Horseradish Peroxidase in Chitosan Matrix Cross-linked with Glyoxal for Amperometric Determination of Hydrogen Peroxide

    PubMed Central

    Wang, Huai-Sheng; Pan, Qian-Xiu; Wang, Gui-Xiang

    2005-01-01

    An amperometric biosensor for hydrogen peroxide (H2O2) was developed via an easy and effective enzyme immobilization method with the “sandwich” configuration: ferrocene-chitosan: HRP: chitosan-glyoxal using a glassy carbon electrode as the basic electrode. In order to prevent the loss of immobilized HRP under optimized conditions, the biosensor surface was cross-linked with glyoxal. Ferrocene was selected and immobilized on the glassy carbon electrode surface as a mediator. The fabrication procedure was systematically optimized to improve the biosensor performance. The biosensor had a fast response of less than 10 s to H2O2, with a linear range of 3.5×10-5 to 1.1×10-3 M, and a detection limit of 8.0×10-6 M based on S/N = 3.

  12. A Cross-Linking Succinonitrile-Based Composite Polymer Electrolyte with Uniformly Dispersed Vinyl-Functionalized SiO2 Particles for Li-Ion Batteries.

    PubMed

    Liu, Kai; Ding, Fei; Liu, Jiaquan; Zhang, Qingqing; Liu, Xingjiang; Zhang, Jinli; Xu, Qiang

    2016-09-14

    A cross-linking succinonitrile (SN)-based composite polymer electrolyte (referred to as "CLPC-CPE"), in which vinyl-functionalized SiO2 particles connect with trimethylolpropane propoxylate triacrylate (TPPTA) monomers by covalent bonds, was prepared by an ultraviolet irradiation (UV-curing) process successfully. Vinyl-functionalized SiO2 particles may react with TPPTA monomers to form a cross-linking network within the SN-based composite polymer electrolyte under ultraviolet irradiation. Vinyl-functionalized SiO2 particles as the fillers of polymer electrolyte may improve both the thermal stability of CLPC-CPE and interfacial compatibility between CLPC-CPE and electrodes effectively. There is no weight loss for CLPC-CPE until above 230 °C. The ionic conductivity of CLPC-CPE may reach 7.02 × 10(-4) S cm(-1) at 25 °C. CLPC-CPE has no significant oxidation current until up to 4.6 V (vs Li/Li(+)). The cell of LiFePO4/CLPC-CPE/Li has presented superior cycle performance and rate capability. The cell of LiFePO4/CLPC-CPE/Li may deliver a high discharge capacity of 154.4 mAh g(-1) at a rate of 0.1 C after 100 charge-discharge cycles, which is similar than that of the control cell of LiFePO4/liquid electrolyte/Li. Furthermore, the cell of LiFePO4/CLPC-CPE/Li can display a high discharge capacity of 112.7 mAh g(-1) at a rate of 2 C, which is higher than that of the cells assembled with other plastic crystal polymer electrolyte reported before obviously. PMID:27561892

  13. Absence of Strand Breaks in Deoxyribonucleic Acid Treated with Metronidazole

    PubMed Central

    LaRusso, Nicholas F.; Tomasz, Maria; Kaplan, David; Müller, Miklós

    1978-01-01

    The deoxyribonucleic acid (DNA)-degrading potential of metronidazole was evaluated in vitro by three techniques: determination of melting curve, measurement of viscosity, and centrifugation in neutral or alkaline sucrose gradients. Studies were performed on calf thymus DNA and on 3H-labeled or unlabeled pneumococcal and T7 phage DNA after treatment with metronidazole alone or metronidazole reduced by sodium dithionite in the presence of DNA. This latter process is known to elicit covalent binding of metronidazole to DNA. Reduced or unreduced metronidazole had no effect on the melting properties, viscosity, or sedimentation velocity of the nucleic acids studied. Sodium dithionite alone, however, caused a 25% decrease in the intrinsic viscosity of pneumococcal DNA, and decreased the sedimentation velocity of pneumococcal and T7 phage DNA in both neutral and alkaline sucrose gradients. These data suggest that degradation of DNA is not important in the interaction of metronidazole with nucleic acids, an interaction assumed relevant to the cytotoxic, radiosensitizing, and mutagenic activities of this compound. PMID:626487

  14. Dynamic hydroxymethylation of deoxyribonucleic acid marks differentiation-associated enhancers

    PubMed Central

    Sérandour, Aurélien A.; Avner, Stéphane; Oger, Frédérik; Bizot, Maud; Percevault, Frédéric; Lucchetti-Miganeh, Céline; Palierne, Gaëlle; Gheeraert, Céline; Barloy-Hubler, Frédérique; Péron, Christine Le; Madigou, Thierry; Durand, Emmanuelle; Froguel, Philippe; Staels, Bart; Lefebvre, Philippe; Métivier, Raphaël; Eeckhoute, Jérôme; Salbert, Gilles

    2012-01-01

    Enhancers are developmentally controlled transcriptional regulatory regions whose activities are modulated through histone modifications or histone variant deposition. In this study, we show by genome-wide mapping that the newly discovered deoxyribonucleic acid (DNA) modification 5-hydroxymethylcytosine (5hmC) is dynamically associated with transcription factor binding to distal regulatory sites during neural differentiation of mouse P19 cells and during adipocyte differentiation of mouse 3T3-L1 cells. Functional annotation reveals that regions gaining 5hmC are associated with genes expressed either in neural tissues when P19 cells undergo neural differentiation or in adipose tissue when 3T3-L1 cells undergo adipocyte differentiation. Furthermore, distal regions gaining 5hmC together with H3K4me2 and H3K27ac in P19 cells behave as differentiation-dependent transcriptional enhancers. Identified regions are enriched in motifs for transcription factors regulating specific cell fates such as Meis1 in P19 cells and PPARγ in 3T3-L1 cells. Accordingly, a fraction of hydroxymethylated Meis1 sites were associated with a dynamic engagement of the 5-methylcytosine hydroxylase Tet1. In addition, kinetic studies of cytosine hydroxymethylation of selected enhancers indicated that DNA hydroxymethylation is an early event of enhancer activation. Hence, acquisition of 5hmC in cell-specific distal regulatory regions may represent a major event of enhancer progression toward an active state and participate in selective activation of tissue-specific genes. PMID:22730288

  15. Deoxyribonucleic acid methylation and chromatin organization in Tetrahymena thermophila.

    PubMed Central

    Pratt, K; Hattman, S

    1981-01-01

    Deoxyribonucleic acid (DNA) of the transcriptionally active macronucleus of Tetrahymena thermophila is methylated at the N6 position of adenine to produce methyladenine (MeAde); approximately 1 in every 125 adenine residues (0.8 mol%) is methylated. Transcriptionally inert micronuclear DNA is not methylated (< or = 0.01 mol% MeAde; M. A. Gorovsky, S. Hattman, and G. L. Pleger, J. Cell Biol. 56:697-701, 1973). There is no detectable cytosine methylation in macronuclei in Tetrahymena DNA (< or = 0.01 mol% 5-methylcytosine). MeAde-containing DNA sequences in macronuclei are preferentially digested by both staphylococcal nuclease and pancreatic deoxyribonuclease I. In contrast, there is no preferential release of MeAde during digestion of purified DNA. These results indicate that MeAde residues are predominantly located in "linker DNA" and perhaps have a function in transcription. Pulse-chase studies showed that labeled MeAde remains preferentially in linker DNA during subsequent rounds of DNA replication; i.e., there is little, if any, movement of nucleosomes during chromatin replication. This implies that nucleosomes may be phased with respect to DNA sequence. PMID:9279374

  16. Crosslinked, porous, polyacrylate beads

    NASA Technical Reports Server (NTRS)

    Rembaum, Alan (Inventor); Yen, Shiao-Ping Siao (Inventor); Dreyer, William J. (Inventor)

    1976-01-01

    Uniformly-shaped, porous, round beads are prepared by the co-polymerization of an acrylic monomer and a cross-linking agent in the presence of 0.05 to 5% by weight of an aqueous soluble polymer such as polyethylene oxide. Cross-linking proceeds at high temperature above about 50.degree.C or at a lower temperature with irradiation. Beads of even shape and even size distribution of less than 2 micron diameter are formed. The beads will find use as adsorbents in chromatography and as markers for studies of cell surface receptors.

  17. Crosslinked, porous, polyacrylate beads

    NASA Technical Reports Server (NTRS)

    Rembaum, Alan (Inventor); Yen, Shiao-Ping S. (Inventor); Dreyer, William J. (Inventor)

    1977-01-01

    Uniformly-shaped, porous, round beads are prepared by the co-polymerization of an acrylic monomer and a cross-linking agent in the presence of 0.05 to 5% by weight of an aqueous soluble polymer such as polyethylene oxide. Cross-linking proceeds at high temperature above about 50.degree. C or at a lower temperature with irradiation. Beads of even shape and even size distribution of less than 2 micron diameter are formed. The beads will find use as adsorbents in chromatography and as markers for studies of cell surface receptors.

  18. Increasing the Depth of Mass-Spectrometry-Based Structural Analysis of Protein Complexes through the Use of Multiple Cross-Linkers.

    PubMed

    Ding, Yue-He; Fan, Sheng-Bo; Li, Shuang; Feng, Bo-Ya; Gao, Ning; Ye, Keqiong; He, Si-Min; Dong, Meng-Qiu

    2016-04-19

    Chemical cross-linking of proteins coupled with mass spectrometry (CXMS) is a powerful tool to study protein folding and to map the interfaces between interacting proteins. The most commonly used cross-linkers in CXMS are BS(3) and DSS, which have similar structures and generate the same linkages between pairs of lysine residues in spatial proximity. However, there are cases where no cross-linkable lysine pairs are present at certain regions of a protein or at the interface of two interacting proteins. In order to find the cross-linkers that can best complement the performance of BS(3) and DSS, we tested seven additional cross-linkers that either have different spacer arm structures or that target different amino acids (BS(2)G, EGS, AMAS, GMBS, Sulfo-GMBS, EDC, and TFCS). Using BSA, aldolase, the yeast H/ACA protein complex, and E. coli 70S ribosomes, we showed that, in terms of providing structural information not obtained through the use of BS(3) and DSS, EGS and Sulfo-GMBS worked better than the other cross-linkers that we tested. EGS generated a large number of cross-links not seen with the other amine-specific cross-linkers, possibly due to its hydrophilic spacer arm. We demonstrate that incorporating the cross-links contributed by the EGS and amine-sulfhydryl cross-linkers greatly increased the accuracy of Rosetta in docking the structure of the yeast H/ACA protein complex. Given the improved depth of useful information it can provide, we suggest that the multilinker CXMS approach should be used routinely when the amount of a sample permits. PMID:27010980

  19. pH-responsive deoxyribonucleic acid capture/release by polydopamine functionalized magnetic nanoparticles.

    PubMed

    Wang, Yu; Ma, Xiangdong; Ding, Chun; Jia, Li

    2015-03-01

    Polydopamine functionalized magnetic nanoparticles (PDA@Fe3O4) were prepared and characterized by transmission electron microscopy, scanning electron microscopy, zeta potential and vibrating sample magnetometry. They were found to enable highly efficient capture of genomic deoxyribonucleic acid (DNA). The adsorption capacity of PDA@Fe3O4 for genomic DNA can reach 161 mg g(-1). The extraction protocol used aqueous solutions for DNA binding to and releasing from the surface of the magnetic particles based on the pH inducing the charge switch of amino and phenolic hydroxyl groups on PDA@Fe3O4. The extracted DNA with high quality (A260/A280=1.80) can be directly used as templates for polymerase chain reaction (PCR) followed by capillary electrophoresis (CE) analysis. None of the toxic chemical reagents and PCR inhibitors was used throughout the whole procedure. PDA@Fe3O4 based magnetic solid phase extraction (MSPE) method was superior to those using commercial kit and traditional phenol-chloroform extraction methods in yield of DNA. The developed PDA@Fe3O4 based MSPE-PCR-CE method was applied for simultaneous and fast detection of Listeria monocytogenes and Escherichia coli O157:H7 in milk. PMID:25682426

  20. Shell-crosslinked knedel-like nanoparticles induce lower immunotoxicity than their non-crosslinked analogs

    PubMed Central

    Elsabahy, Mahmoud; Samarajeewa, Sandani; Raymond, Jeffery E.; Clark, Corrie; Wooley, Karen L.

    2013-01-01

    The development of stable nanoparticles that can withstand the changing conditions experienced in a biological setting and also be of low toxicity and immunogenicity is of particular importance to address the problems associated with currently utilized nanotechnology-based therapeutics and diagnostics. The use of crosslinked nanoparticles continues to receive special impetus, due to their robust structure and high kinetic stability, and they have recently been shown to induce lower cytotoxicity than their non-crosslinked micellar counterparts. In the current study, poly(acrylamidoethylamine)-block-poly(DL-lactide) (PAEA90-b-PDLLA40) copolymers were synthesized, self-assembled in water to yield nanoscopic polymeric micelles, and the effects of decorating the micellar surface with poly(ethylene glycol) (i.e. PEGylation) and crosslinking the PAEA layer to varying extents on the physicochemical characteristics, cytotoxicity and immunotoxicity of the nanoparticles were studied. Herein, we report for the first time that crosslinking can efficiently reduce the immunotoxicity of polymeric nanomaterials. In addition, increasing the degree of crosslinking further reduced the accessibility of biomolecules to the core of the nanoparticles and decreased their cytotoxicity and immunotoxicity. It is also highlighted that crosslinking can be more efficient than PEGylation in reducing the immunotoxicity of nanomaterials. Shell-crosslinking of block copolymer micelles, therefore, is expected to advance their clinical development beyond the earlier known effects, and to broaden the implications in the field of nanomedicine. PMID:24187610

  1. Target-driven self-assembly of stacking deoxyribonucleic acids for highly sensitive assay of proteins.

    PubMed

    Cao, Ya; Chen, Weiwei; Han, Peng; Wang, Zhuxin; Li, Genxi

    2015-08-26

    In this paper, we report a new signal amplification strategy for highly sensitive and enzyme-free method to assay proteins based on the target-driven self-assembly of stacking deoxyribonucleic acids (DNA) on an electrode surface. In the sensing procedure, binding of target protein with the aptamer probe is used as a starting point for a scheduled cycle of DNA hairpin assembly, which consists of hybridization, displacement and target regeneration. Following numbers of the assembly repeats, a great deal of DNA duplexes can accordingly be formed on the electrode surface, and then switch on a succeeding propagation of self-assembled DNA concatemers that provide further signal enhancement. In this way, each target binding event can bring out two cascaded DNA self-assembly processes, namely, stacking DNA self-assembly, and therefore can be converted into remarkably intensified electrochemical signals by associating with silver nanoparticle-based readout. Consequently, highly sensitive detection of target proteins can be achieved. Using interferon-gamma as a model, the assay method displays a linear range from 1 to 500 pM with a detection limit of 0.57 pM, which is comparable or even superior to other reported amplified assays. Moreover, the proposed method eliminates the involvement of any enzymes, thereby enhancing the feasibility in clinical diagnosis. PMID:26347164

  2. Preparation of Thermo-Responsive Poly(ionic liquid)s-Based Nanogels via One-Step Cross-Linking Copolymerization.

    PubMed

    Zhang, Jing; Liu, Jingjiang; Zuo, Yong; Wang, Rongmin; Xiong, Yubing

    2015-01-01

    In this study, thermo-responsive polymeric nanogels were facilely prepared via one-step cross-linking copolymerization of ethylene glycol dimethacrylate/divinylbenzene and ionic liquid (IL)-based monomers, 1,n-dialkyl-3,3'-bis-1-vinyl imidazolium bromides ([CnVIm]Br; n = 6, 8, 12) in selective solvents. The results revealed that stable and blue opalescent biimidazolium (BIm)-based nanogel solutions could be obtained without any precipitation when the copolymerizations were conducted in methanol. Most importantly, these novel nanogels were thermo-response, and could reversibly transform to precipitation in methanol with temperature changes. Turbidity analysis and dynamic light scatting (DLS) measurement illustrated that PIL-based nanogel solutions presented the phase transform with upper critical solution temperature (UCST) in the range of 5-25 °C. The nanogels were characterized using Fourier transform infrared (FTIR), thermogravimetric analyses (TGA), and scanning electron microscopy (SEM). In addition, BIm-based nanogels could also be used as highly active catalysts in the cycloaddition reaction of CO₂ and epoxides. As a result, our attributes build a robust platform suitable for the preparation of polymeric nanomaterials, as well as CO₂ conversion. PMID:26393567

  3. Imidate-Based Cross-Linkers for Structural Proteomics: Increased Charge of Protein and Peptide Ions and CID and ECD Fragmentation Studies

    NASA Astrophysics Data System (ADS)

    Koolen, Hector H. F.; Gomes, Alexandre F.; Schwab, Nicolas V.; Eberlin, Marcos N.; Gozzo, Fabio C.

    2014-07-01

    Chemical cross-linking is an attractive low-resolution technique for structural studies of protein complexes. Distance constraints obtained from cross-linked peptides identified by mass spectrometry (MS) are used to construct and validate protein models. Amidinating cross-linkers such as diethyl suberthioimidate (DEST) have been used successfully in chemical cross-linking experiments. In this work, the application of a commercial diimidate cross-linking reagent, dimethyl suberimidate (DMS), was evaluated with model peptides and proteins. The peptides were designed with acetylated N-termini followed by random sequences containing two Lys residues separated by an Arg residue. After cross-linking reactions, intra- and intermolecular cross-linked species were submitted to CID and ECD dissociations to study their fragmentation features in the gas phase. Fragmentation of intramolecular peptides by collision induced dissociation (CID) demonstrates a unique two-step fragmentation pathway involving formation of a ketimine as intermediate. Electron capture and electron transfer dissociation (ECD and ETD) experiments demonstrated that the cyclic moiety is not dissociated. Intermolecular species demonstrated previously described fragmentation behavior in both CID and ECD experiments. The charge state distributions (CSD) obtained after reaction with DMS were compared with those obtained with disuccinimidyl suberate (DSS). CSDs for peptides and proteins were increased after their reaction with DMS, owing to the higher basicity of DMS modified species. These features were also observed in LC-MS experiments with bovine carbonic anhydrase II (BCA) after cross-linking with DMS and tryptic proteolysis. Cross-linked peptides derived from this protein were identified at high confidence and those species were in agreement with the crystal structure of BCA.

  4. Microbes encapsulated within crosslinkable polymers

    SciTech Connect

    Chidambaram, Devicharan; Liu, Ying; Rafailovich, Miriam H

    2013-02-05

    The invention relates to porous films comprising crosslinked electrospun hydrogel fibers. Viable microbes are encapsulated within the crosslinked electrospun hydrogel fibers. The crosslinked electrospun hydrogel fibers are water insoluble and permeable. The invention also relates to methods of making and using such porous films.

  5. Hybridization triggered cross-linking of deoxyoligonucleotides.

    PubMed Central

    Webb, T R; Matteucci, M D

    1986-01-01

    This paper reports details of the synthesis of oligodeoxynucleotides containing the modified base 5-methyl-N4,N4-ethanocytosine (Ce). The 9-fluorenylmethoxycarbonyl group is used as a protecting group for the exocyclic amines of dA and dC. This group can be removed rapidly under very mild conditions. Oligomers containing the Ce base form a cross-link when hybridized to their complementary deoxyoligonucleotides. Some of the scope and limitations of these cross-link forming oligonucleotides are reported. Images PMID:3774542

  6. Study on the interaction of morphine chloride with deoxyribonucleic acid by fluorescence method

    NASA Astrophysics Data System (ADS)

    Li, J. F.; Dong, C.

    2009-01-01

    The mode and mechanism of the interaction of morphine chloride, an important alkaloid compound to calf thymus deoxyribonucleic acid (ct DNA) was investigated from absorption and fluorescence titration techniques. Hypochromic effect was founded in the absorption spectra of morphine when concentration of DNA increased. The decreased fluorescence study revealed non-cooperative binding of the morphine to DNA with an affinity of 3.94 × 10 3 M -1, and the stoichiometry of binding was characterized to be about one morphine molecule per nucleotide. Stern-Volmer plots at different temperatures proved that the quenching mechanism was static. Ferrocyanide quenching study showed that the magnitude of KSV of the bound morphine was lower than that of the free one. In addition, it was found that ionic strength could affect the binding of morphine and DNA. Fluorescence polarization and denatured DNA studies also applied strong evidences that morphine molecule was partially intercalated between every alternate base pairs of ct DNA. As observed from above experiments, intercalation was well supported as the binding mode of morphine and ct DNA.

  7. Simulation and analysis of an evolutionary model of deoxyribonucleic acid (DNA). Master's thesis

    SciTech Connect

    McNally, R.E.

    1983-09-01

    A Monte Carlo simulation model was developed in order to evaluate model predictions with expectations of the evolutionary hypothesis of nearly neutral point mutations. The beta chain of hemoglobin was chosen as the strand of deoxyribonucleic acid (DNA) to be analyzed due to the extensive characterization of point mutations along the 146 amino acids of the protein chain. The nucleotide sequences of human, rabbit and a hypothetical ancestral hemoglobin were used as a starting point in the simulation. Three models of point mutations were tested. Equiprobable mutation from one nucleotide to any of the remaining three nucleotides composing DNA was one model. The second model incorporated observed first order probability of transition from each nucleotide to the remaining three nucleotides composing DNA using observed probabilities from three independent assessments. The third model was an Ising type model employing a probability of nucleotide change based on the nucleotide composition of the nearest neighbors. Use of these models resulted in evidence to suggest that five methods of simulating the mutations in an evolutionary system produced results that primarily differed in the way in which nulceotide changes resulted in a pattern of amino acid changes.

  8. Fabrication of nickel and gold nanowires by controlled electrodeposition on deoxyribonucleic acid molecules

    NASA Astrophysics Data System (ADS)

    Gu, Qun; Jin, Helena; Dai, Kun

    2009-01-01

    Magnetic and electrical nanowires are two important materials in the development of futuristic nanoelectronics, data storage media and nanosensors. Ni and Au nanowires with a diameter of a few tens of nanometres have been fabricated using deoxyribonucleic acid (DNA) molecules as a template through nanoparticle-controlled electroless deposition (ELD). Nanowire precursors, 1-3 nm Pt(0)-DNA and 1.4 nm Au(0)-DNA, were assembled using two different methods. Chemical reduction was used to deposit Pt(0) particles on DNA which catalyzed Ni nanowire growth. Positively charged Au nanoparticles were directly assembled on phosphate groups of DNA which were stretched and anchored between micrometre-spaced electrodes. Electrical measurement has shown that Au nanowires, catalyzed by Au(0)-DNA in a subsequent ELD, are highly conductive and show linear I-V characteristics. The major factors for the resistivity of nanowires were discussed in detail. This work involves important aspects in the field of DNA-based self-assembly, such as DNA and surface interaction, DNA nanoparticle assembly and electrical property of fabricated nanowires.

  9. Physical location of the ilvO determinant in Escherichia coli K-12 deoxyribonucleic acid.

    PubMed Central

    Subrahmanyam, C S; McCorkle, G M; Umbarger, H E

    1980-01-01

    A plasmid carrying the 4,6-kilobase (kb) HindIII-derived fragment from an ilvO mutant derivative of lambda h80dilv imparted a valine-resistant phenotype on strains it carried. This fragment carries a small amount of the promoter-proximal end of ilvE, the ilvO determinant, and apparently the entire ilvG gene, which specifies the valine-insensitive acetohydroxy acid synthase. Comparable deoxyribonucleic acid (DNA) from the original lambda h80dilv did not carry the valine resistance marker. The valine-resistant phenotype was always correlated with the formation of the resistant enzymes. The ilvO determinant was shown to be carried within an approximately 600-based-pair region lying between the SalI and KpnI sites on the HindIII fragment and perhaps within the ilvG gene itself. Ribonucleic acid that hybridizes with the DNA corresponding to the ilvG gene is formed in wild-type K-12 cells. This fact, coupled with the fact that ilvG is transcribed from the same DNA strand as the ilvE, D, and A genes, led to the idea that transcription is normally initiated upstream from ilvG in both wild-type and ilvO strains. In wild-type strains either the formation or the translation of the transcript would be terminated with the ilvG gene, thus preventing expression of that gene. PMID:6155372

  10. Particle acceleration for delivery deoxyribonucleic acid vaccine into skin in vivo

    NASA Astrophysics Data System (ADS)

    Xinglong, Yu; Xiwen, Zhang; Yuan, Wang; Junshi, Xie; Pengfei, Hao

    2001-08-01

    Skin represents an important immunogenic inductive site, 3%-4% epidermis cells are special antigen-presenting cells. Deoxyribonucleic acid (DNA) vaccine can elicit vigorous immune responses in epidermis cells. The means of delivering DNA vaccine into epidermis cells becomes an important step in DNA vaccine applications. This article presents a new type of gene gun based on the principle of two-stage injector acceleration. DNA coated particles are attached on an screen-type carrier located at the negative pressure inlet, the particles will be sucked into the accelerating channel by negative pressure and be accelerated at a great speed. FLUENT, a computation fluid dynamic application software is used to simulate the flow condition of the injector. Distribution of Mach number, total pressure on exit cross section, and negative pressure on negative pressure inlet are analyzed, by which the process of acceleration of particles is determined. We also measured these parameters in this study. The data show that the particle velocity can be up to 500 m/s and the particles distribute evenly over a circle of Φ 20 mm. The numerical simulation results coincide with experimental data well. Therefore, the results of numerical simulation can be served as guidance for an optimal design of the gene gun and for practical operations. When gene coated particles are distributed evenly, they can penetrate into or even through epidermis cells where the gene can be expressed and subsequently elicits host immune responses. This device may be evaluated in human objects in future.

  11. The effect of cross-linking on the molecular dynamics of the segmental and β Johari-Goldstein processes in polyvinylpyrrolidone-based copolymers.

    PubMed

    Redondo-Foj, Belén; Sanchis, María Jesús; Ortiz-Serna, Pilar; Carsí, Marta; García, José Miguel; García, Félix Clemente

    2015-09-28

    The effect of the cross-link density on the molecular dynamics of copolymers composed of vinylpyrrolidone (VP) and butyl acrylate (BA) was studied using differential scanning calorimetry (DSC) and dielectric relaxation spectroscopy (DRS). A single glass transition was detected by DSC measurements. The dielectric spectra exhibit conductive processes and three dipolar relaxations labeled as α, β and γ in the decreasing order of temperatures. The cross-linker content affects both α and β processes, but the fastest γ process is relatively unaffected. An increase of cross-linking produces a typical effect on the α process dynamics: (i) the glass transition temperature is increased, (ii) the dispersion is broadened, (iii) its strength is decreased and (iv) the relaxation times are increased. However, the β process, which possesses typical features of a pure Johari-Goldstein relaxation, unexpectedly loses the intermolecular character for the highest cross-linker content. PMID:26255757

  12. Structure of γ-tubulin small complex based on a cryo-EM map, chemical cross-links, and a remotely related structure.

    PubMed

    Greenberg, Charles H; Kollman, Justin; Zelter, Alex; Johnson, Richard; MacCoss, Michael J; Davis, Trisha N; Agard, David A; Sali, Andrej

    2016-06-01

    Modeling protein complex structures based on distantly related homologues can be challenging due to poor sequence and structure conservation. Therefore, utilizing even low-resolution experimental data can significantly increase model precision and accuracy. Here, we present models of the two key functional states of the yeast γ-tubulin small complex (γTuSC): one for the low-activity "open" state and another for the higher-activity "closed" state. Both models were computed based on remotely related template structures and cryo-EM density maps at 6.9Å and 8.0Å resolution, respectively. For each state, extensive sampling of alignments and conformations was guided by the fit to the corresponding cryo-EM density map. The resulting good-scoring models formed a tightly clustered ensemble of conformations in most regions. We found significant structural differences between the two states, primarily in the γ-tubulin subunit regions where the microtubule binds. We also report a set of chemical cross-links that were found to be consistent with equilibrium between the open and closed states. The protocols developed here have been incorporated into our open-source Integrative Modeling Platform (IMP) software package (http://integrativemodeling.org), and can therefore be applied to many other systems. PMID:26968363

  13. Hydroxyl functionalized thermosensitive microgels with quadratic crosslinking density distribution.

    PubMed

    Elmas, Begum; Tuncel, Murvet; Senel, Serap; Patir, S; Tuncel, Ali

    2007-09-01

    N-isopropylacrylamide (NIPA) based uniform thermosensitive microgels were synthesized by dispersion polymerization by using relatively hydrophilic crosslinking agents with hydroxyl functionality. Glycerol dimethacrylate (GDMA), pentaerythritol triacrylate (PETA) and pentaerythritol propoxylate triacrylate (PEPTA) were used as crosslinking agents with different hydrophilicities. A protocol was first proposed to determine the crosslinking density distribution in the thermosensitive microgel particles by confocal laser scanning microscopy (CLSM). The microgels were fluorescently labeled by using hydroxyl group of the crosslinking agent. The CLSM observations performed with the microgels synthesized by three different crosslinking agents showed that the crosslinking density exhibited a quadratic decrease with the increasing radial distance in the spherical microgel particles. This structure led to the formation of more loose gel structure on the particle surface with respect to the center. Then the use of hydrophilic crosslinking agents in the dispersion polymerization of NIPA made possible the synthesis of thermosensitive microgels carrying long, flexible and chemically derivatizable (i.e., hydroxyl functionalized) fringes on the surface by a single-stage dispersion polymerization. The microgels with all crosslinking agents exhibited volume phase transition with the increasing temperature. The microgel obtained by the most hydrophilic crosslinking agent, GDMA exhibited higher hydrodynamic diameters in the fully swollen form at low temperatures than those obtained by PETA and PEPTA. Higher hydrodynamic size decrease from fully swollen form to the fully shrunken form was also observed with the same microgel. PMID:17532327

  14. Cross-linking Chemistry of Squid Beak*

    PubMed Central

    Miserez, Ali; Rubin, Daniel; Waite, J. Herbert

    2010-01-01

    In stark contrast to most aggressive predators, Dosidicus gigas (jumbo squids) do not use minerals in their powerful mouthparts known as beaks. Their beaks instead consist of a highly sclerotized chitinous composite with incremental hydration from the tip to the base. We previously reported l-3,4-dihydroxyphenylalanine (dopa)-histidine (dopa-His) as an important covalent cross-link providing mechanical strengthening to the beak material. Here, we present a more complete characterization of the sclerotization chemistry and describe additional cross-links from D. gigas beak. All cross-links presented in this report share common building blocks, a family of di-, tri-, and tetra-histidine-catecholic adducts, that were separated by affinity chromatography and high performance liquid chromatography (HPLC) and identified by tandem mass spectroscopy and proton nuclear magnetic resonance (1H NMR). The data provide additional insights into the unusually high cross-link density found in mature beaks. Furthermore, we propose both a low molecular weight catechol, and peptidyl-dopa, to be sclerotization agents of squid beak. This appears to represent a new strategy for forming hard tissue in animals. The interplay between covalent cross-linking and dehydration on the graded properties of the beaks is discussed. PMID:20870720

  15. Cross-linking chemistry of squid beak.

    PubMed

    Miserez, Ali; Rubin, Daniel; Waite, J Herbert

    2010-12-01

    In stark contrast to most aggressive predators, Dosidicus gigas (jumbo squids) do not use minerals in their powerful mouthparts known as beaks. Their beaks instead consist of a highly sclerotized chitinous composite with incremental hydration from the tip to the base. We previously reported l-3,4-dihydroxyphenylalanine (dopa)-histidine (dopa-His) as an important covalent cross-link providing mechanical strengthening to the beak material. Here, we present a more complete characterization of the sclerotization chemistry and describe additional cross-links from D. gigas beak. All cross-links presented in this report share common building blocks, a family of di-, tri-, and tetra-histidine-catecholic adducts, that were separated by affinity chromatography and high performance liquid chromatography (HPLC) and identified by tandem mass spectroscopy and proton nuclear magnetic resonance ((1)H NMR). The data provide additional insights into the unusually high cross-link density found in mature beaks. Furthermore, we propose both a low molecular weight catechol, and peptidyl-dopa, to be sclerotization agents of squid beak. This appears to represent a new strategy for forming hard tissue in animals. The interplay between covalent cross-linking and dehydration on the graded properties of the beaks is discussed. PMID:20870720

  16. Adsorption of Hg2+, Cu2+ and Zn2+ ions from aqueous solution using formaldehyde cross-linked modified chitosan-thioglyceraldehyde Schiff's base.

    PubMed

    Monier, M

    2012-04-01

    A chitosan-thioglyceraldehyde Schiff's base cross-linked magnetic resin (CSTG) was prepared and characterized using various instrumental methods. Then, the prepared resin was used for comparative studies on the removal of toxic metal ions like: Hg(2+), Cu(2+) and Zn(2+) from aqueous solutions. The effects of the initial pH value of the solution, contact time, the initial metal ion concentration and temperature on the adsorption capacity of the composite were investigated. The kinetics data were analyzed by pseudo-first order and pseudo-second order equations. The adsorption kinetics was well described by the pseudo-second order equation, and the adsorption isotherms were better fitted by the Langmuir equation. The maximum theoretical adsorption capacities of the CSTG resin for Hg(2+), Cu(2+) and Zn(2+) were found to be 98±2, 76±1 and 52±1 mg g(-1), respectively. The negative values of Gibbs free energy of adsorption (ΔG(ads°) indicated the spontaneity of the adsorption of all metal ions on the novel resin. PMID:22155403

  17. Adsorption of Cu(II), Cd(II) and Ni(II) ions by cross-linked magnetic chitosan-2-aminopyridine glyoxal Schiff's base.

    PubMed

    Monier, M; Ayad, D M; Abdel-Latif, D A

    2012-06-01

    The adsorption of Cu(II), Cd(II) and Ni(II) ions from aqueous solution by cross-linked magnetic chitosan-2-aminopyridine glyoxal Schiff's base resin (CSAP) was studied in a batch adsorption system. Cu(II), Cd(II) and Ni(II) removal is pH dependent and the optimum adsorption was observed at pH 5.0. The adsorption was fast with estimated initial rate of 2.7, 2.4 and 1.4 mg/(g min) for Cu(2+), Cd(2+) and Ni(2+) respectively. The adsorption data could be well interpreted by the Langmuir, Freundlich and Temkin model. The maximum adsorption capacities obtained from the Langmuir model were 124±1, 84±2 and 67±2 mg g(-1) for Cu(2+), Cd(2+) and Ni(2+) respectively. The adsorption process could be described by pseudo-second-order kinetic model. Thermodynamic parameters revealed the feasibility, spontaneity and exothermic nature of adsorption. The sorbents were successfully regenerated using EDTA and HCl solutions. PMID:22386793

  18. Structure-based site-directed photo-crosslinking analyses of multimeric cell-adhesive interactions of voltage-gated sodium channel β subunits

    PubMed Central

    Shimizu, Hideaki; Miyazaki, Haruko; Ohsawa, Noboru; Shoji, Shisako; Ishizuka-Katsura, Yoshiko; Tosaki, Asako; Oyama, Fumitaka; Terada, Takaho; Sakamoto, Kensaku; Shirouzu, Mikako; Sekine, Shun-ichi; Nukina, Nobuyuki; Yokoyama, Shigeyuki

    2016-01-01

    The β1, β2, and β4 subunits of voltage-gated sodium channels reportedly function as cell adhesion molecules. The present crystallographic analysis of the β4 extracellular domain revealed an antiparallel arrangement of the β4 molecules in the crystal lattice. The interface between the two antiparallel β4 molecules is asymmetric, and results in a multimeric assembly. Structure-based mutagenesis and site-directed photo-crosslinking analyses of the β4-mediated cell-cell adhesion revealed that the interface between the antiparallel β4 molecules corresponds to that in the trans homophilic interaction for the multimeric assembly of β4 in cell-cell adhesion. This trans interaction mode is also employed in the β1-mediated cell-cell adhesion. Moreover, the β1 gene mutations associated with generalized epilepsy with febrile seizures plus (GEFS+) impaired the β1-mediated cell-cell adhesion, which should underlie the GEFS+ pathogenesis. Thus, the structural basis for the β-subunit-mediated cell-cell adhesion has been established. PMID:27216889

  19. Size-Shifting Micelle Nanoclusters Based on a Cross-Linked and pH-Sensitive Framework for Enhanced Tumor Targeting and Deep Penetration Features.

    PubMed

    Liang, Huihui; Ren, Xiaoqing; Qian, Jianghui; Zhang, Xiulei; Meng, Lin; Wang, Xiaofei; Li, Lei; Fang, Xiaoling; Sha, Xianyi

    2016-04-27

    The antitumor effect of chemotherapeutics loaded micelles mainly depends on two aspects: the accumulation in the tumor region and the penetration into the tumor interior. These two processes have different demands on particle size. The optimal particle size for enhanced permeability and retention (EPR) is commonly believed to be around 100 nm, while much smaller size is desired for deeper penetration into the tumor interior. To address these two different requirements, we constructed size-shifting micelle nanoclusters (MNC) based on a cross-linked framework interspersed with micelles. The particle size of the micelles was 14.6 ± 0.8 nm and increased to 104.2 ± 8.1 nm after the MNC were formed, leading to an effective utilization of the EPR effect. MNC were shifted to independent micelles in lysosomes, so that a more favorable particle size for penetration could be realized. The results of antitumor growth in vivo demonstrated that size-shifting MNC were more beneficial for tumor therapy than micelles. PMID:27046063

  20. Influence of surfactant on dynamics of photoinduced motions and light emission of a dye-doped deoxyribonucleic acid

    NASA Astrophysics Data System (ADS)

    Sznitko, Lech; Parafiniuk, Kacper; Miniewicz, Andrzej; Rau, Ileana; Kajzar, Francois; Niziol, Jacek; Hebda, Edyta; Pielichowski, Jan; Sahraoui, Bouchta; Mysliwiec, Jaroslaw

    2013-10-01

    Pure deoxyribonucleic acid (DNA) is known to be soluble in water only and exhibits poor temperature stability. In contrary, it is well known that the complex of DNA - with cetyltrimethyl ammonium (CTMA) is insoluble in water but soluble in alcohols and can be processed into very good optical quality thin films by solution casting or spin deposition. Despite the success of DNA-CTMA, there is still need for new cationic surfactants which would extend the range of available solvents for DNA complex. We test and present experimental results of influence of new surfactants replacing CTMA in the DNA complex and based on benzalkonium chloride (BA) and didecyldimethylammonium chloride (DDCA) on their optical properties. Particularly, we were interested in all optical switching and light generation in amplified spontaneous emission process in these materials.

  1. Conjugation of glucosamine with Gd3+-based nanoporous silica using a heterobifunctional ANB-NOS crosslinker for imaging of cancer cells

    PubMed Central

    Mehravi, Bita; Ahmadi, Mohsen; Amanlou, Massoud; Mostaar, Ahmad; Ardestani, Mehdi Shafiee; Ghalandarlaki, Negar

    2013-01-01

    Background The aim of this study was to synthesize Gd3+-based silica nanoparticles that conjugate easily with glucosamine and to investigate their use as a nanoprobe for detection of human fibrosarcoma cells. Methods Based on the structure of the 2-fluoro-2-deoxy-D-glucose molecule (18FDG), a new compound consisting of D-glucose (1.1 nm) was conjugated with a Gd3+-based mesoporous silica nanoparticle using an N-5-azido-2-nitrobenzoyloxy succinimide (ANB-NOS) crosslinker The contrast agent obtained was characterized using a variety of methods, including Fourier transform infrared spectroscopy, nitrogen physisorption, thermogravimetric analysis, scanning and transmission electron microscopy, and inductively coupled plasma atomic emission spectrometry (ICP-AES). In vitro studies included cell toxicity, apoptosis, tumor necrosis factor-alpha, and hexokinase assays, and in vivo tests consisted of evaluation of blood glucose levels using the contrast compound and tumor imaging. The cellular uptake study was validated using ICP-AES. Magnetic resonance relaxivity of the contrast agent was determined using a 1.5 Tesla scanner. Results ANB-NOS was found to be the preferred linker for attaching glucosamine onto the surface of the mesoporous silica nanospheres. The r1 relaxivity for the nanoparticles was 17.70 mM−1s−1 per Gd3+ ion, which is 4.4 times larger than that for Magnevist® (r1 approximately 4 mM−1s−1 per Gd3+ ion). The compound showed suitable cellular uptake (75.6% ± 2.01%) without any appreciable cytotoxicity. Conclusion Our results suggest that covalently attaching glucosamine molecules to mesoporous silica nanoparticles enables effective targeted delivery of a contrast agent. PMID:24101868

  2. Crosslinking biopolymers for biomedical applications.

    PubMed

    Reddy, Narendra; Reddy, Roopa; Jiang, Qiuran

    2015-06-01

    Biomaterials made from proteins, polysaccharides, and synthetic biopolymers are preferred but lack the mechanical properties and stability in aqueous environments necessary for medical applications. Crosslinking improves the properties of the biomaterials, but most crosslinkers either cause undesirable changes to the functionality of the biopolymers or result in cytotoxicity. Glutaraldehyde, the most widely used crosslinking agent, is difficult to handle and contradictory views have been presented on the cytotoxicity of glutaraldehyde-crosslinked materials. Recently, poly(carboxylic acids) that can crosslink in both dry and wet conditions have been shown to provide the desired improvements in tensile properties, increase in stability under aqueous conditions, and also promote cell attachment and proliferation. Green chemicals and newer crosslinking approaches are necessary to obtain biopolymeric materials with properties desired for medical applications. PMID:25887334

  3. Disruption of Adenovirus Type 7 by Lithium Iodide Resulting in the Release of Viral Deoxyribonucleic Acid

    PubMed Central

    Neurath, A. Robert; Stasny, John T.; Rubin, Benjamin A.

    1970-01-01

    Adenovirus type 7 exposed to solutions of LiI was progressively converted into slower sedimenting deoxyribonucleic acid (DNA)-containing particles, and, ultimately, under proper conditions, DNA free or almost free from protein was released from the virus. The degree of viral degradation was dependent on the time of treatment, on the temperature, and on the concentration of the reagent. PMID:4988267

  4. Large Scale Chemical Cross-linking Mass Spectrometry Perspectives

    PubMed Central

    Zybailov, Boris L.; Glazko, Galina V.; Jaiswal, Mihir; Raney, Kevin D.

    2014-01-01

    The spectacular heterogeneity of a complex protein mixture from biological samples becomes even more difficult to tackle when one’s attention is shifted towards different protein complex topologies, transient interactions, or localization of PPIs. Meticulous protein-by-protein affinity pull-downs and yeast-two-hybrid screens are the two approaches currently used to decipher proteome-wide interaction networks. Another method is to employ chemical cross-linking, which gives not only identities of interactors, but could also provide information on the sites of interactions and interaction interfaces. Despite significant advances in mass spectrometry instrumentation over the last decade, mapping Protein-Protein Interactions (PPIs) using chemical cross-linking remains time consuming and requires substantial expertise, even in the simplest of systems. While robust methodologies and software exist for the analysis of binary PPIs and also for the single protein structure refinement using cross-linking-derived constraints, undertaking a proteome-wide cross-linking study is highly complex. Difficulties include i) identifying cross-linkers of the right length and selectivity that could capture interactions of interest; ii) enrichment of the cross-linked species; iii) identification and validation of the cross-linked peptides and cross-linked sites. In this review we examine existing literature aimed at the large-scale protein cross-linking and discuss possible paths for improvement. We also discuss short-length cross-linkers of broad specificity such as formaldehyde and diazirine-based photo-cross-linkers. These cross-linkers could potentially capture many types of interactions, without strict requirement for a particular amino-acid to be present at a given protein-protein interface. How these shortlength, broad specificity cross-linkers be applied to proteome-wide studies? We will suggest specific advances in methodology, instrumentation and software that are needed to

  5. Development of a Crosslink Channel Simulator

    NASA Technical Reports Server (NTRS)

    Hunt, Chris; Smith, Carl; Burns, Rich

    2004-01-01

    Distributed Spacecraft missions are an integral part of current and future plans for NASA and other space agencies. Many of these multi-vehicle missions involve utilizing the array of spacecraft as a single, instrument requiring communication via crosslinks to achieve mission goals. NASA s Goddard Space Flight Center (GSFC) is developing the Formation Flying Test Bed (FFTB) to provide a hardware-in-the-loop simulation environment to support mission concept development and system trades with a primary focus on Guidance, Navigation, and Control (GN&C) challenges associated with spacecraft flying. The goal of the FFTB is to reduce mission risk by assisting in mission planning and analysis, provide a technology development platform that allows algorithms to be developed for mission functions such as precision formation navigation and control and time synchronization. The FFTB will provide a medium in which the various crosslink transponders being used in multi-vehicle missions can be integrated for development and test; an integral part of the FFTB is the Crosslink Channel Simulator (CCS). The CCS is placed into the communications channel between the crosslinks under test, and is used to simulate on-mission effects to the communications channel such as vehicle maneuvers, relative vehicle motion, or antenna misalignment. The CCS is based on the Starlight software programmable platform developed at General Dynamics Decision Systems and provides the CCS with the ability to be modified on the fly to adapt to new crosslink formats or mission parameters. This paper briefly describes the Formation Flying Test Bed and its potential uses. It then provides details on the current and future development of the Crosslink Channel Simulator and its capabilities.

  6. Folic acid-targeted disulfide-based cross-linking micelle for enhanced drug encapsulation stability and site-specific drug delivery against tumors

    PubMed Central

    Zhang, Yumin; Zhou, Junhui; Yang, Cuihong; Wang, Weiwei; Chu, Liping; Huang, Fan; Liu, Qiang; Deng, Liandong; Kong, Deling; Liu, Jianfeng; Liu, Jinjian

    2016-01-01

    Although the shortcomings of small molecular antitumor drugs were efficiently improved by being entrapped into nanosized vehicles, premature drug release and insufficient tumor targeting demand innovative approaches that boost the stability and tumor responsiveness of drug-loaded nanocarriers. Here, we show the use of the core cross-linking method to generate a micelle with enhanced drug encapsulation ability and sensitivity of drug release in tumor. This kind of micelle could increase curcumin (Cur) delivery to HeLa cells in vitro and improve tumor accumulation in vivo. We designed and synthesized the core cross-linked micelle (CCM) with polyethylene glycol and folic acid-polyethylene glycol as the hydrophilic units, pyridyldisulfide as the cross-linkable and hydrophobic unit, and disulfide bond as the cross-linker. CCM showed spherical shape with a diameter of 91.2 nm by the characterization of dynamic light scattering and transmission electron microscope. Attributed to the core cross-linking, drug-loaded CCM displayed higher Nile Red or Cur-encapsulated stability and better sensitivity to glutathione than noncross-linked micelle (NCM). Cellular uptake and in vitro antitumor studies proved the enhanced endocytosis and better cytotoxicity of CCM-Cur against HeLa cells, which had a high level of glutathione. Meanwhile, the folate receptor-mediated drug delivery (FA-CCM-Cur) further enhanced the endocytosis and cytotoxicity. Ex vivo imaging studies showed that CCM-Cur and FA-CCM-Cur possessed higher tumor accumulation until 24 hours after injection. Concretely, FA-CCM-Cur exhibited the highest tumor accumulation with 1.7-fold of noncross-linked micelle Cur and 2.8-fold of free Cur. By combining cross-linking of the core with active tumor targeting of FA, we demonstrated a new and effective way to design nanocarriers for enhanced drug encapsulation, smart tumor responsiveness, and elevated tumor accumulation. PMID:27051287

  7. Folic acid-targeted disulfide-based cross-linking micelle for enhanced drug encapsulation stability and site-specific drug delivery against tumors.

    PubMed

    Zhang, Yumin; Zhou, Junhui; Yang, Cuihong; Wang, Weiwei; Chu, Liping; Huang, Fan; Liu, Qiang; Deng, Liandong; Kong, Deling; Liu, Jianfeng; Liu, Jinjian

    2016-01-01

    Although the shortcomings of small molecular antitumor drugs were efficiently improved by being entrapped into nanosized vehicles, premature drug release and insufficient tumor targeting demand innovative approaches that boost the stability and tumor responsiveness of drug-loaded nanocarriers. Here, we show the use of the core cross-linking method to generate a micelle with enhanced drug encapsulation ability and sensitivity of drug release in tumor. This kind of micelle could increase curcumin (Cur) delivery to HeLa cells in vitro and improve tumor accumulation in vivo. We designed and synthesized the core cross-linked micelle (CCM) with polyethylene glycol and folic acid-polyethylene glycol as the hydrophilic units, pyridyldisulfide as the cross-linkable and hydrophobic unit, and disulfide bond as the cross-linker. CCM showed spherical shape with a diameter of 91.2 nm by the characterization of dynamic light scattering and transmission electron microscope. Attributed to the core cross-linking, drug-loaded CCM displayed higher Nile Red or Cur-encapsulated stability and better sensitivity to glutathione than noncross-linked micelle (NCM). Cellular uptake and in vitro antitumor studies proved the enhanced endocytosis and better cytotoxicity of CCM-Cur against HeLa cells, which had a high level of glutathione. Meanwhile, the folate receptor-mediated drug delivery (FA-CCM-Cur) further enhanced the endocytosis and cytotoxicity. Ex vivo imaging studies showed that CCM-Cur and FA-CCM-Cur possessed higher tumor accumulation until 24 hours after injection. Concretely, FA-CCM-Cur exhibited the highest tumor accumulation with 1.7-fold of noncross-linked micelle Cur and 2.8-fold of free Cur. By combining cross-linking of the core with active tumor targeting of FA, we demonstrated a new and effective way to design nanocarriers for enhanced drug encapsulation, smart tumor responsiveness, and elevated tumor accumulation. PMID:27051287

  8. Multiphoton photochemical crosslinking-based fabrication of protein micropatterns with controllable mechanical properties for single cell traction force measurements

    NASA Astrophysics Data System (ADS)

    Tong, Ming Hui; Huang, Nan; Zhang, Wei; Zhou, Zhuo Long; Ngan, Alfonso Hing Wan; Du, Yanan; Chan, Barbara Pui

    2016-01-01

    Engineering 3D microstructures with predetermined properties is critical for stem cell niche studies. We have developed a multiphoton femtosecond laser-based 3D printing platform, which generates complex protein microstructures in minutes. Here, we used the platform to test a series of fabrication and reagent parameters in precisely controlling the mechanical properties of protein micropillars. Atomic force microscopy was utilized to measure the reduced elastic modulus of the micropillars, and transmission electron microscopy was used to visualize the porosity of the structures. The reduced elastic modulus of the micropillars associated positively and linearly with the scanning power. On the other hand, the porosity and pore size of the micropillars associated inversely and linearly with the scanning power and reagent concentrations. While keeping the elastic modulus constant, the stiffness of the micropillars was controlled by varying their height. Subsequently, the single cell traction forces of rabbit chondrocytes, human dermal fibroblasts, human mesenchymal stem cells, and bovine nucleus pulposus cells (bNPCs) were successfully measured by culturing the cells on micropillar arrays of different stiffness. Our results showed that the traction forces of all groups showed positive relationship with stiffness, and that the chondrocytes and bNPCs generated the highest and lowest traction forces, respectively.

  9. Multiphoton photochemical crosslinking-based fabrication of protein micropatterns with controllable mechanical properties for single cell traction force measurements.

    PubMed

    Tong, Ming Hui; Huang, Nan; Zhang, Wei; Zhou, Zhuo Long; Ngan, Alfonso Hing Wan; Du, Yanan; Chan, Barbara Pui

    2016-01-01

    Engineering 3D microstructures with predetermined properties is critical for stem cell niche studies. We have developed a multiphoton femtosecond laser-based 3D printing platform, which generates complex protein microstructures in minutes. Here, we used the platform to test a series of fabrication and reagent parameters in precisely controlling the mechanical properties of protein micropillars. Atomic force microscopy was utilized to measure the reduced elastic modulus of the micropillars, and transmission electron microscopy was used to visualize the porosity of the structures. The reduced elastic modulus of the micropillars associated positively and linearly with the scanning power. On the other hand, the porosity and pore size of the micropillars associated inversely and linearly with the scanning power and reagent concentrations. While keeping the elastic modulus constant, the stiffness of the micropillars was controlled by varying their height. Subsequently, the single cell traction forces of rabbit chondrocytes, human dermal fibroblasts, human mesenchymal stem cells, and bovine nucleus pulposus cells (bNPCs) were successfully measured by culturing the cells on micropillar arrays of different stiffness. Our results showed that the traction forces of all groups showed positive relationship with stiffness, and that the chondrocytes and bNPCs generated the highest and lowest traction forces, respectively. PMID:26817674

  10. Multiphoton photochemical crosslinking-based fabrication of protein micropatterns with controllable mechanical properties for single cell traction force measurements

    PubMed Central

    Tong, Ming Hui; Huang, Nan; Zhang, Wei; Zhou, Zhuo Long; Ngan, Alfonso Hing Wan; Du, Yanan; Chan, Barbara Pui

    2016-01-01

    Engineering 3D microstructures with predetermined properties is critical for stem cell niche studies. We have developed a multiphoton femtosecond laser-based 3D printing platform, which generates complex protein microstructures in minutes. Here, we used the platform to test a series of fabrication and reagent parameters in precisely controlling the mechanical properties of protein micropillars. Atomic force microscopy was utilized to measure the reduced elastic modulus of the micropillars, and transmission electron microscopy was used to visualize the porosity of the structures. The reduced elastic modulus of the micropillars associated positively and linearly with the scanning power. On the other hand, the porosity and pore size of the micropillars associated inversely and linearly with the scanning power and reagent concentrations. While keeping the elastic modulus constant, the stiffness of the micropillars was controlled by varying their height. Subsequently, the single cell traction forces of rabbit chondrocytes, human dermal fibroblasts, human mesenchymal stem cells, and bovine nucleus pulposus cells (bNPCs) were successfully measured by culturing the cells on micropillar arrays of different stiffness. Our results showed that the traction forces of all groups showed positive relationship with stiffness, and that the chondrocytes and bNPCs generated the highest and lowest traction forces, respectively. PMID:26817674