Modification And Construction Of Silk Sericin Recycled Material Via Laccase And TEMPO Catalysis

Silk sericin can be potentially used in the fields of tissue engineering,biomaterials and others,mainly owing to its excellent features of antioxidant ability and good cytocompatibility.However,poor mechanical property of sericin-based films restricts its applications in biomedical fields.In the present work,silk sericin was enzymatically incubated with laccase and 2,2',6,6'-tetramethylpiperidine-N-oxyl(TEMPO),followed by grafting of a RGD-containing polypeptides,aiming at improving the mechanical property and functionality of sericin-based films.The efficacies of laccase/TEMPO-mediated catalytic oxidation and cross-linking of silk sericin were examined.The mechanism of catalytic oxidation was investigated by determination of the changes in the contents of aldehyde,carboxyl,amine groups and fluorescence spectrum as well.The results of sericin cross-linking were examined by means of SDS-PAGE,size exclusion chromatography(SEC),and mechanical property testing.The changes of conformational structure,thermal property and antioxidant property for the silk sericin were evaluated,respectively,by means of ATR-FTIR,TG and ABTS,the obtained biocompatibility for the silk sericin material was also concerned.After grafting of the RGD polypeptides onto sericin with laccase and TEMPO,the grafting fields of RGD polypeptide onto sericin were measured.Furthermore,NIH/3T3 cells proliferation and adhesion effects were evaluated after grafting of RGD polypeptide onto silk sericin.The results indicated that laccase and TEMPO could catalyze the oxidation of serine and tyrosine residues in silk sericin and formed intermolecular cross-linking,resulting in the increase of molecular weight and the declines in contents of serine,tyrosine and amino groups.After incubating the 1%(w/v)sericin with 0.4 U/m L laccase and 1.28 mM TEMPO at 37?,the mechanical property and thermal behavior for the obtained air-dried membrane was superior to others.Meanwhile,small changes were detected in the secondary structure of the silk sericin after laccase/TEMPO treatment.Based on the above work,grafting of the RGD polypeptides onto the silk sericin were carried out by using laccase and TEMPO system.The results indicated that the amount of RGD polypeptides onto the surface of silk sericin based on laccase/TEMPO treatment was much high than that of the control.Meanwhile,the modified sericin membrane exhibited significant promotion effects on the proliferation and adhesion of NIH/3T3 cells,implying grafting of RGD polypeptides onto sericin can improve biocompatibility of silk sericin.