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. 2019 Nov 1;11(11):1787.
doi: 10.3390/polym11111787.

Mechanically Reinforced Gelatin Hydrogels by Introducing Slidable Supramolecular Cross-Linkers

Dae Hoon Lee  1 , Atsushi Tamura  2 , Yoshinori Arisaka  3 , Ji-Hun Seo  4 , Nobuhiko Yui  5
Affiliations

Mechanically Reinforced Gelatin Hydrogels by Introducing Slidable Supramolecular Cross-Linkers

Dae Hoon Lee et al. Polymers (Basel). .

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.

Keywords: chemical cross-linking; gelatin; hysteresis loss; polyrotaxane; stretchability.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
(a) Chemical structure of carboxymethyl ether group-modified polyrotaxanes (CME-PRXs); (b) Schematic illustration of gelatin hydrogels cross-linked with PRX under a stretch-and-relax environment.
Figure 2
Figure 2
(a) 1H NMR spectra of CME-PRX-24%, CME-PRX-37%, and α-CD in D2O; (b) FT-IR spectra of unmodified PRX, CME-PRX-24%, and CME-PRX-37%; (c) SEC charts of α-CD, CME-PRX-37%, and CME-PRX-24% in 100 mM NaNO3.
Figure 3
Figure 3
(a) Gross images of gelatin hydrogels cross-linked by EDC/NHS, CME-PRX-24%, and CME-PRX-37%; (b) Swelling ratio of gelatin hydrogels cross-linked by EDC/NHS, CME-PRX-37%, and CME-PRX-24%.
Figure 4
Figure 4
(a) Stress–strain curves of gelatin hydrogels cross-linked by CME-PRXs; (b) Elongation; (c) tensile strength; (d) toughness of gelatin hydrogels cross-linked by CME-PRXs (* p < 0.05 and ** p < 0.01; n = 3).
Figure 5
Figure 5
Cyclic tensile test for gelatin hydrogels cross-linked by (a) EDC/NHS; (b) CME-PRX-37%; (c) CME-PRX-24%; (d) Hysteresis loss of gelatin hydrogels in each cycle (n = 3).
See this image and copyright information in PMC

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