Materials Science Forum Vol. 815

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Abstract: Various methods were developed to prepare hydrogels including photo-cross-linking, chemical cross-linking, enzymatic cross-linking, pH or temperature-induced gelation, ionic interaction, and hydrophobic interactions. Whereas silk fibroin gelation time was difficult to control by physical methods, the cross-linkers used in chemical technique were likely to reduce the cell biocompatibility. Sodium N-Lauroyl Sarcosinate (SNS), an amino acid-based surfactant, came into accelerate silk fibroin to form silk hydrogel. To monitor the gelation process and determine the gelation time, turbidity changes during gelation were measured by Synergy HT. Cylindrical gels have been measured with universal material experiment machine and KES for mechanical properties. Fibroblast (L929) cells were seeded on the surface of hydrogels to investigate the cell compatibility. The results show that the SNS/SF gelation time ranges from 20 min to 120 min, which is affected by environment temperature, the final concentrations of SF and SNS. Compared with pure silk fibroin hydrogels, the compression strength of SNS/SF gel is much stronger. SNS/SF gel has excellent compression-recovery performance in KES test as well. A logarithmic stable cell growth appears on the surface of SNS/SF hydrogels, which indicates that SNS/SF hydrogels have excellent cell compatibility. Therefore, the SNS/SF hydrogels have great potential in tissue repair for surgery.
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Abstract: Mesenchymal stem cells (MSCs) are a powerful cellular alternative for regenerative medicine and tissue engineering applications due to their multipotency. It is becoming increasingly clear that elasticity of extracellular matrix (ECM) has a profound effect on cell phenotype including adhesion, proliferation and differentiation. Integrins are considered to be important mechanoreceptors in mechanotransduction. While numerous studies have focused on α2, β1 and β3 integrin involvement in substrate stiffness-driven commitment of bone marrow MSCs, comparatively little is known about the change of α5β1 integrin expression in human umbilical cord-derived mesenchymal stem cells (hUCMSCs) on substrates of variable stiffness. We plated hUCMSCs on fibronectin coated polyacrylamide hydrogels with elasticity corresponding to Young’s modulus ranging from 3 to 65 kPa. Our results showed that hUCMSCs displayed different morphologies on substrates of varying stiffness. Cells led to branched morphology similar to that of nerve cells when cultured on soft matrices, while cells became more spread and presented polygonal shapes on stiff substrates. Furthermore, hUCMSCs expressed α5 integrin both on soft substrates and stiff substrates, and the expression levels on the two substrates were similar. The total β1 integrin (including both active and inactive) was higher in hUCMSCs grown on the stiff substrate than that of grown on soft substrates, whereas the activated β1 integrin level on stiff substrates was distinctly lower than that of grown on soft substrates. In conclusion, α5β1 integrin expression in hUCMSCs is dependent on matrix elasticity. The results from this study will provide insight into the role of α5β1 integrin in matrix elasticity-regulated morphologies changes of stem cells and have implication for understanding the mechanism of physical induced lineage specification.
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Abstract: Corneal transplantation is the only effective way to repair the damaged corneal tissue and solve the problem of insufficient donor cornea and immune rejection. Biocompatibility and stable transparent are necessary conditions of corneal stromal cells carrier. In this paper, the acetamide/silk (AC/SF) composite membranes are studied to be applied in corneal repair material. AC/SF membranes with different blending proportions had stable transparency, good cell compatibility. X-ray diffraction was used to investigate the structure of the composite films. The acetamide inhibited the formation of large crystalline particles, changed the crystal structure of silk fibroin and made the random coil structure convert to Silk I or Silk II. Therefore, acetamide was not only crosslinking agent but also crystallization inhibitor. The corneal stromal cells were seeded on sterilized composite membranes. After 5 h, the adhesion rate of stromal cells was more than 90%, cell could proliferate regularly on the composite membrane. There was no obvious difference in contrast to control plate. These results demonstrated that the composite membrane could promote corneal stromal cell proliferation.
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Abstract: In this article, the layered deposition method is adopted to prepare the collagen/hydroxyapatite (COL/HA) composite coating. The morphology and elements of the COL/HA composite coating are observed using a scanning electron microscope (SEM) with an energy dispersive spectrometer (EDS), the optical density (O.D.) values are obtained by MTT assay to assess the cellular viabilityof composite coating. The experimental results showed that the addition of collagen not only improve the bonding strength of composite coating and porous titanium substrate, but also combine the osteoconduction of inorganic coating HA and the osteoinduction of organic coating COL, effectively enhance the cellular adhesion, proliferation and differentiation. The cellular viability cultured in COL/HA composite coating is much higher than the pure HA modified coating.
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Abstract: Water-soluble carbon dots (CDs) with high yield were synthesized by a facile, one-step incomplete pyrolytic route under nitrogen atmosphere or air using ammonium citrate as carbon source. Photoluminescence (PL) spectrum, Fourier transform infrared (FTIR) absorption and high-resolution transmission electron microscopy (HRTEM) were used to determine the characteristics of the CDs. Though CDs could be prepared from 150 oC to 400 oC, the highest yield of CDs (17.5%) was achieved at the heating temperature of 150 oC in air, so did the relative quantum yield. The as-prepared CDs showed excellent biocompatibility and had been tentatively used in cell imaging.
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Abstract: Nickel titanium is a near-equiatomic intermetallic that possesses distinctive and desirable thermomechanical properties. Micro-arc oxidation (MAO) treatment of NiTi can effectively prevent the release of Ni ions from NiTi. In this paper, NiTi is treated with MAO method in Na2SiO3 electrolyte. MAO process of NiTi in Na2SiO3 electrolyte contains two stages: “growth period”, “jumped period”. During the process of MAO, Ni in NiTi is oxidized to Ni ion, and the Ni ions are dissociated in electrolyte. Ti was left in NiTi, which generate much Ti content appearing on the surface of the sample, and contribute to prerequisites for the reaction. After the applied voltage reaches a certain value, Na2SiO3 electrolyte participate in the reaction and form insulating amorphous silicon oxide layer. With the increase of thickness of insulating layer on NiTi, the anodic voltage increase. When applied voltage excess certain threshold, discharge spark appear on the surface of NiTi.
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Abstract: Dental implant made of pure titanium (Ti) has become one important option to restore the function of lost tooth. However, because of insufficient hardness, it is always scratched during oral hygieneprocedures. To improve its surface hardness,titanium nitride (TiN) coating was prepared. Soft tissue - implant interface is important for blocking bacteria invasion, therefore surface modification is necessary to improve biocompatibility of TiN for fibroblasts.In the present study, TiN coating was modified by hydrothermal treatment incalcium acetate (CaAc) solution and effect of hydrothermal treatment temperature was studied. After treatment,calcium (Ca) wassuccessfully combined into TiN surface and the surface morphology, roughness and hardness were not changed below 140 °C. It is expected that, surface modification with Ca by hydrothermal treatment could made TiN a promising dental implant coating.
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Abstract: Silk sericin composed of 18 amino acids has been widely used in the fields of cosmetic additives, food, medicine and functional biomaterials because of good hydrophilicity and biocompatibility, making it great possibility in providing abundant nutrients for microbial growth. Sericin (40~200 KDa) was used as culture medium for incubation of E. coli at 37°C to study the effect of sericin concentration on the growth of bacterial Escherichi coli (E. coli). The growth curves of E. coli, surface/inside morphology and protein of E. coli were investigated by UV/vis spectrophotometer (UV/vis), scanning electron microscopy (SEM), transmission electronic microscopy (TEM) and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The cytotoxicity of sercin was also confirmed by MTT assay. The value of OD600 increases with increasing sericin concentration from 0 to 40 g/L. Compared with the control, OD600 of 40 g/L sericin medium increases from 0.013 to 1.269 after incubated 12h. E. coli cell still remains rod shape regardless of concentration of sericin. The content of cellular soluble proteins significantly increases in sericin-treated bacteria, which in turn influenced the cell structure composition and catalyzing activity of enzyme, and finally stimulated the proliferation of E. coli. Results indicate that sericin can independently provide carbon and nitrogen for bacterial growth. Besides, it can promote bacterial protein expression without affecting cell morphology.
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Abstract: N-shaped ZnO nanorods were first chirality synthesized by glacial acetic acid assisted annealing process. X-ray powder diffraction results show that these nanorods are of ZnO wurtzite-structure. These nanorods grow from a thin platelet base and are parallel to each other to form n-shaped ZnO nanorods. The width of thin platelet bases range from 50 to 130 nm. The diameters of the nanorods rang from 25 to 60nm, and their lengths are 0.2—0.6um. Gas sensors fabricated from these n-shaped ZnO nanorods show a very high sensitivity to ethanol gas and the sensitivity is up to about 35 against 1000 ppm ethanol gas at the operating temperature of 300°C.
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Abstract: An optical active Acrylate end-functionalized poly (lactic acid) (DPLA) was synthesized via melt polycondensation, with lactic acid, polyalcohol and acrylic acid as raw materials. The prepolymer products in each process were characterized by FT-IR, 1H-NMR. The curing PLA coating (CPLA) was prepared using optical active DPLA, reactive diluent and photoinitiator. Gel fraction, thermal stability and degradation properties of the UV curing PLA coating properties were evaluated. The results show that branched structure of hydroxyl-terminated poly (lactic acid) (OHPLA) is beneficial to increase acrylic end capping rate (Da), Da ois as high as 88%. The structure of prepolymer and the performance of the coating are adjusted by changing content of polyalcohol. After crosslinking modification, degradation rate of CPLA is reduced and CPLA has better thermal stability than the pure PLA.
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