Self-Immolative Hydrogels with Orthogonal Pathways for Depolymerization by pH Change, Light, and Mechanical Force

Abstract

Hydrogels are high water content networks used across many applications. Stimuli-responsive hydrogels exhibit changes in properties or break down in response to stimuli, leading to new functions and applications, with self-immolative polymer hydrogels enabling amplified responses to stimuli through end-to-end depolymerization. Described here are new self-immolative polyglyoxylamide hydrogels prepared by free radical cross-linking of pendent methacrylates. The effects of pendent methacrylate density, polymer concentration, and the addition of a bisacrylamide cross-linker on hydrogel gel content, equilibrium water content, modulus, structure, and degradation were investigated. The incorporation of 20% pendent methacrylates led to homogeneous hydrogels with compressive moduli ranging from 15 to 53 kPa. The hydrogel prepared from a 10% (w/v) polymer formulation had an interconnected porous structure facilitating depolymerization in response to mild acid, light, and mechanical force, while the incorporation of an additional cross-linker inhibited degradation. This hydrogel was also well tolerated in vitro in cytotoxicity studies, providing a promising platform for applications.