Exploring the Gelation Mechanisms and Cytocompatibility of Gold (III)-Mediated Regenerated and Thiolated Silk Fibroin Hydrogels.

Siriporn Damrongsakkul,Helena Ferreira,Supansa Yodmuang,Rui L Reis,Nuno M Neves,Chavee Laomeephol

doi:10.3390/biom10030466

Exploring the Gelation Mechanisms and Cytocompatibility of Gold (III)-Mediated Regenerated and Thiolated Silk Fibroin Hydrogels.

Siriporn Damrongsakkul, Helena Ferreira + Show 4 more

Open Access

https://doi.org/10.3390/biom10030466

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Journal: Biomolecules	Publication Date: Mar 18, 2020
Citations: 9	License type: CC BY 4.0

Affiliation: Chulalongkorn University, University of Minho

Abstract

Accelerating the gelation of silk fibroin (SF) solution from several days or weeks to minutes or few hours is critical for several applications (e.g., cell encapsulation, bio-ink for 3D printing, and injectable controlled release). In this study, the rapid gelation of SF induced by a gold salt (Au3+) as well as the cytocompatibility of Au3+-mediated SF hydrogels are reported. The gelation behaviors and mechanisms of regenerated SF and thiolated SF (tSF) were compared. Hydrogels can be obtained immediately after mixing or within three days depending on the types of silk proteins used and amount of Au3+. Au3+-mediated SF and tSF hydrogels showed different color appearances. The color of Au-SF hydrogels was purple-red, whereas the Au-tSF hydrogels maintained their initial solution color, indicating different gelation mechanisms. The reduction of Au3+ by amino groups and further reduction to Au by tyrosine present in SF, resulting in a dityrosine bonding and Au nanoparticles (NPs) production, are proposed as underlying mechanisms of Au-SF gel formation. Thiol groups of the tSF reduced Au3+ to Au+ and formed a disulfide bond, before a formation of Au+-S bonds. Protons generated during the reactions between Au3+ and SF or tSF led to a decrease of the local pH, which affected the chain aggregation of the SF, and induced the conformational transition of SF protein to beta sheet. The cytocompatibility of the Au-SF and tSF hydrogels was demonstrated by culturing with a L929 cell line, indicating that the developed hydrogels can be promising 3D matrices for different biomedical applications.

Highlights

Silk fibroin (SF) is a protein-based biopolymer derived from Bombyx mori mulberry silkworms
The formation of 1 mM Au3+-3% SF hydrogels was accompanied with an obvious color change, which can be related to the Au nanoparticles (AuNPs) formation (Figure 2A)
Dityrosine bonding and the formation of AuNPs were proposed for Au3+-mediated SF hydrogels with the purple-red color

Summary

Introduction

Silk fibroin (SF) is a protein-based biopolymer derived from Bombyx mori mulberry silkworms. The glycine-alanine repetitive sequences, present in high amount in the heavy chain, are responsible for the formation of beta sheet structure, making SF a natural-derived material with good biodegradability and excellent mechanical properties [1]. The ordered beta sheet structures turn into amorphous random coil, and the dissolution of SF fiber is obtained. SF solution spontaneously turns into hydrogel within several days or weeks because of the gradual transition to the thermodynamically stable beta sheet structure [3]. This self-assembly characteristic of SF has intrigued many researchers, which have been employing various strategies to control and accelerate the gelation process. Crosslinking agents (e.g., glutaraldehyde, carbodiimides, or genipin), enzymes (e.g., tyrosinase or peroxidase), physical methods (e.g., vortexing or sonication), or chemical additives (e.g., alcohols [4], surfactants [5], or phospholipids [6]) have been applied to control the kinetics of SF gelation [7]

Results

Discussion

Conclusion