Most hydrogels used in biomedical applications are formed through condensation or radical polymerisation and display a static architecture with low fracture toughness. In contrast, natural hydrogels in tissue are highly dynamic, where internal and external forces will catalyse changes in chemistry, architecture, and mechanical properties. Here we demonstrate two mechanochemical modalities: disulfide rupture/biomolecule immobilisation, and a retro-Diels-Alder biomolecule release. This immobilisation and release approach in response to force is inspired by nature, which has developed analogous mechanisms to guide tissue morphogenesis during development. To imbue the toughness needed in mechanical applications, including durability under cyclic loading, the covalent mechanophore linked hydrogels is impregnated with a second ionically linked alginate network to facilitate toughness properties approximating natural hydrogels. First, I will show how compression of a disulfide linked poly(ethylene glycol) hydrogel in the presence of a Michael acceptor will lead to force-mediated immobilization of biomolecules to spatially direct cell adhesion. Next, I will demonstrate how an oxanorbornadiene cross linked hydrogel will release biomolecules through a force-mediated retro Diels-Alder reaction. Together, these immobilisation and release concepts that mimic natural processes in the extracellular matrix, provides a new approach to making force-responsive dynamic biomaterials for a broad spectrum of applications including implant adhesives and coatings, bandages, biosensors, and materials for tissue engineering.

Mechanochemistry in hydrogel biomaterials: Force-mediated molecule release and immobilization

ACS Fall 2021

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