A novel one-pot approach towards dynamically cross-linked hydrogels

Abstract

Herein, we report the synthesis of sliding-ring (SR) hydrogel networks in a one-pot click-mediated approach using α,ω-dialkyne poly(ethylene glycol) (PEG) and azido-functionalised cyclodextrin, which acts as both sliding cross-link and end-capping agent. This novel approach resulted in polymeric networks that possess a combination of both SR and covalent (CV) cross-link points. The extent of inclusion complexation and the ratio of SR to CV cross-links in the hydrogels was found to be dependent on both the concentration of the precursors and the curing temperature. Based upon model studies where rotaxanes were synthesised from the same precursors, it was observed that an increase in the precursor concentration led to an increase in click efficiency and inclusion ratio, which in turn affects the overall hydrogel rigidity and elasticity. Hydrogels synthesised at higher curing temperatures led to more homogeneous networks that were significantly tougher as a result of the overall increase in cross-linking density and the extent of CV cross-links. We therefore present a facile one-pot method for the synthesis of SR networks with tunable physicochemical properties. Additionally, the resultant hydrogel networks are potentially capable of supporting post-modification with various (bio)molecules or therapeutics utilizing the remaining azide groups on the cyclodextrin cross-links. Preliminary cytotoxicity studies revealed that the hydrogels did not impede cell growth and demonstrate negligible toxicity. Thus, these networks may have potential for soft-tissue engineering or biomedical applications, including sustained release and drug-delivery systems.