Thiolation and characterization of regenerated Bombyx mori silk fibroin films with reduced glutathione

Xiaoning Zhang,Jianwei Liang,Hong Bao,Shui Xu,Sha Yang,Carrie Donley

doi:10.1186/s13065-019-0583-x

Abstract

Bombyxmori silk fibroin-based materials have good biocompatibility and biodegradability. In order to maximize their utility while maintain appropriate features, silk fibroin (SF) films were modified with reduced glutathione (GSH) (NH2)–ECG–(COOH), using the carbodiimide chemistry method, for the introduction of thiol groups onto surfaces. The effects of this modification on SF films’ chemical and physical properties, and cytotoxicity were assessed. The chemical and elemental composition analysis results suggested that reduced glutathione (GSH) was covalently coupled onto the surface of silk fibroin films. Atomic force microscopy (AFM) results indicated the surface roughness of silk fibroin film was increased after the modification by GSH. The GSH-modified silk fibroin films also showed the smaller contact angle due to the hydrophilic peptides coupled on the film surface. Through MTT assay, it was shown that the chemically modified SF film was not cytotoxic to HEK293 cells, and it had no adverse influence on the growth of HEK293 cells. Our approach provides a new option to engineer SF-based material surface with thiol groups in order to allow for secondary reactions and holds great promise for applications of SF-based materials in the biomedical field.

Highlights

Natural biopolymers could be used in various biomedical applications [1, 2]
It can be observed from FTIR spectra that amide I, amide II, and amide III of both water annealed and GSH grafted silk fibroin (SF) film were at 1645 cm−1, 1522 cm−1, and 1235 cm−1, respectively
The absorption band at 3276 cm−1 represents for N–H stretching vibration of amide [24], and the intensity of this band after carbodiimide coupling is apparently increased indicating the increased density of the amide bond (Fig. 2c), which is from the reaction between primary amine of reduced glutathione (GSH) and activated carboxylic groups in silk fibroin, or vice versa

Summary

Introduction

Natural biopolymers could be used in various biomedical applications [1, 2]. As one of natural biopolymers, silk secreted by silkworm Bombyx mori consists of silk fibroin (SF) and sericin. The two paralleled silk fibroin fibers are held together with a layer of sericin on their surface. Among SF and sericin [3], SF have good biocompatibility, and have shown its potential to be used as substitute materials for bone, cartilage and ligaments [4,5,6]. The degradation products of SF are non-toxic, but are helpful for nutrition and repair of tissues such as skin and periodontal tissues [7]. Other advantages of SF materials include the ability to withstand sterilization conditions without losing their integrity, easy to prepare, and stable

Methods

Results

Conclusion