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Biomedical application of silk requires the removal of sericin that is the gumming material of native silk fibers. This is because sericin can elicit an adverse immune response after implantation in the human body. However, the removal of sericin causes the silk fiber to fray and weakens its structural property, making it very difficult to knit or braid them into a scaffold for ligament tissue engineering applications. The aim of this study was to replace sericin with gelatin using NDGA as a cross-linking agent to biomimic the natural structure of native silk fibers. The physical properties and biocompatibility of the modified and native silk fibers were compared by in vitro and in vivo models. The mechanical and swelling properties of sericin-free silk fibers were greatly increased after modification with gelatin. Both modified and native silk fibers were shown to be nontoxic by in vitro cytotoxicity tests. The in vivo study demonstrated that the modified silk fibers, after 4 weeks' subcutaneous implantation in rats, caused little or no inflammatory reaction as compared with native silk fibers. The superior mechanical properties and lower inflammatory potential of modified silk fibers make them a promising candidate for ligament tissue engineering applications.

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Blend homogeneous films of chitosan and water-soluble methoxy poly(ethylene glycol)-b-poly(e-caprolactone) (MPEG-b-PCL) diblock copolymer with different blend ratios were prepared by aqueous solution blending method. The water-soluble MPEG-b-PCL was synthesized using MPEG with molecular weight of 5000 g/mol and stannous octoate as the initiating system. The molecular weight of MPEG-b-PCL obtained from 1 H-NMR was 5800 g/mol. FTIR spectra of the blend films showed that there were intermolecular bonds between chitosan and MPEG-b-PCL. Thermal properties of the blend films strongly depended on the blend ratios. Scanning electron micrographs indicated that the blend films were homogeneous films. However, roughness of the blend films increased whereas transparency and moisture uptake decreased upon increasing the MPEG-b-PCL blend ratios.