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

Abstract

Bombyx mori 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) (NH 2 )–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. Electronic supplementary material The online version of this article (10.1186/s13065-019-0583-x) contains supplementary material, which is available to authorized users.

Fabrication and Characterization of Silk Fibroin/Curcumin Sustained-Release Film

“…It was reported that SF without antibacterial agent does not exhibit antibacterial activity [42,43]. In this work, Gram-positive bacteria S. aureus and Gram-negative bacteria E. coli , which are common bacteria found in wound infections [44], were used to test the antimicrobial effectiveness of the SF/GA/Gly/Cur composite film.…”

Silk Film Stiffness Modulates Corneal Epithelial Cell Mechanosignaling

“…While studies have been published using AFM to measure the stiffness of silk films, to our knowledge, only dry films have been evaluated with stiffness values reported in the gigapascal (GPa) range. [ 23–29 ] These values are at least two orders of magnitude greater than the stiffness of most physiologic tissues which typically measure in the kilopascals (kPa). The mechanical properties of silk films are known to change dramatically from a glass‐like, brittle state when dry to soft and highly flexible when fully hydrated.…”

“…[ 33 ] Water is known to plasticize the fibroin polymer which results in greater mobility, flexibility, and extensibility of silk fibroin films. [ 50 ] AFM studies performed on dry films report gigapascal Young's moduli, [ 23–29 ] similar to that of tissue culture plastic. In stark contrast, fully hydrated films from our study measured within kilopascals which is not only much more similar to the stiffness of physiological tissue, it is lower by two orders of magnitude.…”

“…In contrast, surface material properties define the biophysical cues at the cell‐material interface and are thus primarily responsible for how cells respond to a material. [ 17,19–22 ] While studies have used atomic force microscopy (AFM) to characterize the surface properties of silk films on a scale relevant to cellular mechanical forces, [ 23–29 ] only dried films have been evaluated. The mechanical properties of dried silk films differ substantially from fully hydrated films [ 27 ] in an aqueous environment like that of the cornea, and therefore, are unrepresentative of the biophysical cues present to cells.…”

Chemical modification of Bombyx mori silk fibers with vinyl groups for thiol-ene click chemistry

“…Each rinsing cycle was carried out in 1 l of ultrapure water in a lab beaker, using a stir bar to circulate the volume within the beaker. After the wash, the excess water was squeezed out of the silk, and the degummed silk was then spread out on a clean piece of print paper, allowing the silk to dry in a fume hood overnight [10].…”