Mechanically Reinforced Gelatin Hydrogels by Introducing Slidable Supramolecular Cross-Linkers.

Dae Hoon Lee,Nobuhiko Yui,Ji-Hun Seo,Atsushi Tamura,Yoshinori Arisaka

doi:10.3390/polym11111787

Abstract

Tough mechanical properties are generally required for tissue substitutes used in regeneration of damaged tissue, as these substitutes must be able to withstand the external physical force caused by stretching. Gelatin, a biopolymer derived from collagen, is a biocompatible and cell adhesive material, and is thus widely utilized as a component of biomaterials. However, the application of gelatin hydrogels as a tissue substitute is limited owing to their insufficient mechanical properties. Chemical cross-linking is a promising method to improve the mechanical properties of hydrogels. We examined the potential of the chemical cross-linking of gelatin hydrogels with carboxy-group-modified polyrotaxanes (PRXs), a supramolecular polymer comprising a poly(ethylene glycol) chain threaded into the cavity of α-cyclodextrins (α-CDs), to improve mechanical properties such as stretchability and toughness. Cross-linking gelatin hydrogels with threading α-CDs in PRXs could allow for freely mobile cross-linking points to potentially improve the mechanical properties. Indeed, the stretchability and toughness of gelatin hydrogels cross-linked with PRXs were slightly higher than those of the hydrogels with the conventional chemical cross-linkers 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC)/N-hydroxysuccinimide (NHS). In addition, the hysteresis loss of gelatin hydrogels cross-linked with PRXs after repeated stretching and relaxation cycles in a hydrated state was remarkably improved in comparison with that of conventional cross-linked hydrogels. It is considered that the freely mobile cross-linking points of gelatin hydrogels cross-linked with PRXs attenuates the stress concentration. Accordingly, gelatin hydrogels cross-linked with PRXs would provide excellent mechanical properties as biocompatible tissue substitutes exposed to a continuous external physical force.

Highlights

Tissue substitutes are utilized to complement the functions of tissues that have been damaged by an innate disease or strong external forces [1]
Hydrogel-type scaffolds have limited applications for tissue regeneration owing to their insufficient mechanical properties [3], which is a critical requirement of a tissue substitute to endure the continuous external physical forces on the body
The introduction of CME groups onto CME-PRXs was characterized by 1 H nuclear magnetic resonance (NMR) and Fourier transform infrared (FT-IR) (Figure 2)

Summary

Introduction

Tissue substitutes are utilized to complement the functions of tissues that have been damaged by an innate disease or strong external forces [1]. Hydrogel-type scaffolds have limited applications for tissue regeneration owing to their insufficient mechanical properties [3], which is a critical requirement of a tissue substitute to endure the continuous external physical forces on the body. The mechanical properties of hydrogels used for tissue engineering are generally controlled by different factors such as the cross-link density [4,5] and molecular weight distribution [6]. To solve this problem, many researchers have studied strategies for enhancing the mechanical properties of hydrogels with physical or chemical methods [7,8,9,10,11].

Methods

Results

Conclusion