Surface Modification of Bombyx mori Silk Fibroin Film via Thiol-ene Click Chemistry

Xiaoning Zhang,Xiaolin Zhang,Jianwei Liang,Zhenyu Chen,Carrie Donley,Guotao Cheng

doi:10.3390/pr8050498

Abstract

The purpose of this work is to develop a strategy for the surface modification of Bombyx mori silk fibroin (SF) film, via a thiol-ene click reaction, in order to expand its potential applicability. To achieve this goal, terminal thiol groups, from reduced glutathione, were introduced onto the surface of the SF film via a carbodiimide coupling reaction. These immobilized thiol groups act as robust crosslinkers and allow us to rapidly functionalize the surface with alkene group-containing molecules via ultraviolet (UV) light-initiated thiol-ene click chemistry. The X-ray photoelectron spectroscopy results specifically determined that alkene group-containing molecules and UV illumination are required for the thiol-ene click modification to take place on thiolated SF films. Fourier-transform infrared spectroscopy characterization of SF films indicated that the β-sheet conformation of SF was hampered throughout the modification process. Furthermore, it was found that the processes for thiol-ene click chemistry that took place on the SF film surface did not affect the thermal stability of SF films significantly, indicating the developed strategy preserved the intrinsic properties of the SF film. Taking into account that many alkene-containing molecules are suitable for thiol-ene click chemistry, we see immense potential for the incorporation of SF films into various applications, using this methodology.

Highlights

As an ancient material, the degummed silk fibroin (SF) fibers can be dissolved in aqueousCaCl2 -ethanol-H2 O solution (1:2:8 in molar ratio)
X-ray photoelectron spectroscopy (XPS) measurements were used to investigate the chemistry at the surface of the samples throughout the modification processes
Once GSH-SF films were exposed to neat BUD and illuminated under 365 nm ultraviolet light-emitting diode (UV-LED) for 10 min, a bromine peak could be identified by XPS (Figure 2a) as a consequence of the thiol-ene click reaction between the GSH-SF

Summary

Introduction

The degummed silk fibroin (SF) fibers can be dissolved in aqueous. CaCl2 -ethanol-H2 O solution (1:2:8 in molar ratio). The regenerated silk fibroin solutions can be processed into different forms such as gels, sponges and films [1,2]. Among those, regenerated silk fibroin film shows particular promising features due to its optical transparency, biocompatibility, mechanical robustness and flexible nature [3]. It is known that the application of silk fibroin films can be expanded with the proper surface modification [5,6]. As one of the methods for material modification, click chemistry is appealing because it is efficient yet stereospecific, high-yielding with minimal byproducts, and environmentally-friendly

Objectives

Methods

Results