| Biomedical materials have the special functions to diagnose, treat, replace and restore the organism. The functional materials can also interact with the living organs. In the tissue repair process, the mechanical properties of the biological material, security, and performance degradation in vivo is one of the most important performance indicators of the biomedical material and material prerequisites for medical applications. Silk protein is a kind of biogenic protein polymer with good biocompatibility, mechanical strength and avirulent side-effect, meeting the medical requirement of degradability of implanted biomaterials.Blend films was prepared from silk fibroin (SF) and polyethylene glycol (PEG) using a solution casting method and the structural change of blend films were investigated by Fourier transform infrared spectroscopy (FTIR), X-raydiffraction (XRD)and differential scanning calorimetry (DSC). The results were utilized to reveal the influence of PEG addition on the mechanical and dissolution properties of the blend films and the release kinetics of Rhodamine B, a model compound loaded in the SF/PEG matrix, with the purpose to regulate the drug releasing property of SF biomaterial by blending with PEG. The results indicated that PEG was compatible with SF and existed in noncrystalline region of SF, acting as a plasticizer. PEG was found to induce conformational transition of SF from random coil to β-sheet, resulting in great changes in mechanical and dissolution properties, as well as drug release feature of the blend films. With increasing PEG content, the tensile strength and elongation of blend films first increased and then decreased, reaching a maximum around CPEg=10%and20%, respectively. On the contrast, the dissolution of blend films first decreased and then increased, reaching a minimum around CPEG=10%. Compared with the pure SF film, additions of PEG greatly reduce the release of Rhodamine B. It was suggested that Rhodamine B released from SF/PEG blend films via a non-typical Fickian diffusion mechanism, of which the release constant k decreased and diffusion parameter n increased with increasing PEG content, maybe due to the different releasing feature of the silk Ⅱ crystalline and noncrystalline region of SF. Blend film treated with90%methanol-water, which release index n value with the increase of the added polyethylene glycol to reduce (n values ranging between0.4-0.5).In this process, Fickian film release mechanism plays a dominant role.With increasing enzyme concentration, the degradation rate of silk fibroin/polyethylene glycol blend films. With increasing enzyme concentration, the degradation rate of silk fibroin/polyethylene glycol blend films exhibit logarithmic cumulative degradation curve, first sharply, then gently. The degradation rate is also increased with the amount of polyethylene glycol added. The drug diffusion index n of Silk fibroin/polyethylene glycol blend films is in the vicinity of0.43, indicating the Rhodamine B release from the the mixed film attributable to Fickian diffusion, but is different from the Fickian spread system of typical flat, cylindrical and spherical. Protease XIV also can accelerate degradation of silk fibroin/polyethylene glycol blend films with processed90%methanol, but the degradation rate is only about20%. In an enzyme solution, the process of degradation with matrix swelling and silk fibroin molecules decomposing, the drug release exponent n values is ranging between0.5and0.89belonged "irregular transit" mechanism. Although the post-processing in methanol-water solvent blend membranes showed lower enzymatic degradation of nature, but the mechanical properties, drug release less than just adding polyethylene glycol blend membranes, which provides for further application of silk fibroin materialnecessary basis. |
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