Preparation of a multifunctional fibroin-based biomaterial via laccase-assisted grafting of chitooligosaccharide.

Chitooligosaccharide (COS) has the characteristic of antioxidant and antibacterial effects. To improve the properties of silk fibroin (SF), COS was enzymatically grafted onto SF membranes using a laccase from Trametes versicolor. d-Glucosamine hydrochloride (GAH) and p-hydroxyphenylacetamide (PHAD), as the model compound of COS and tyrosine residues in SF were utilized to disclose the grafting mechanism, respectively. The data from UPLC-TQD and GPC analysis implied that laccase might catalyze the oxidation of PHAD and led to the formation of self-polymerized products. FTIR and H NMR results verified the occurrence of the laccase-assisted reactions between COS and PHAD. For the fibroin samples with different treatments, incubation with laccase alone led to remarkable increase in the molecular weight of SF, mainly owing to the efficient self-crosslinks of the fibroin chains. For the COS-grafted SF membrane, there was no obvious change in the thermal behavior, while the antioxidant and antibacterial properties were evidently improved when compared to that of the untreated. Meanwhile, biocompatibility of the COS grafted SF membrane was acceptable according to the cell viability of NIH/3T3 cells. The present work provides a novel method for preparation of the multifunctional fibroin-based biomaterials.