Preparation And Application Of Wool Keratin Film Cross-linked By Enzyme

Keratin is a widely distributed structural fibrous protein. As an ideal source of biological materials, keratin is non-toxic, nonirritant, biocompatibility and biodegradable. Transglutaminase(TGase) is a kind of transfer enzyme that can catalyze acyl transfer reaction. It can catalyze the covalent crossing-links between proteins. With such a special catalytic characteristics, TGase can be widely applied in many fields. In this research, keratin was extracted from wool to make into regenerated film, the influence of TGase treatment on the properties of the film was studied and the reaction mechanism of TGase was preliminary analyzed. Finally, the modified film was used in biomedical field for cell culture and drug release.The results showed that new biopolymers with higher molecular weight were formed by TGase-catalyzed reaction of wool keratins. The most suitable conditions of the cross-link reaction are as follows: 30 U/g wool keratin of TGase, 40℃of temperature, pH 7.5 of film-forming solutions, 18 h of treatment time. A proper amount of plasticizer improved the flexibility of the film, and the addition of reducing agent (DTT) increased the polymerization degree of the wool keratin. Under optimum operating conditions, TGase treatment significantly increased the tensile strength and surface hydrophobicity values of keratin film by 15.7% and 14.2%, respectively, and simultaneously notably decreased the breaking elongation, water content, solubility and transparency values. Thermal analysis (DSC, TGA) results showed that the TGase-catalyzed slightly increased the melting temperature and thermal stability of wool keratin. Scanning electric microscopy (SEM) results implied that TGase modified film formed a more homogeneous and compact network structure. FTIR demonstrated the cross-linking of TGase increased the ratio of random coils in secondary structure. The prepared film could be used as a cell culture matrix. The results of drug release indicated that the speed of drug release could be affected by the thickness of the film and the content of drug. TGase modification enhanced the stability of the film and reduced the drug release rate.