External stimuli-driven catalytic hydrogels for biomedical applications

Hydrogels, bearing three-dimensional networks formed through chemical or physical crosslinking of hydrophilic macromolecules, benefit from their biocompatibility, tunable properties, and high loading capacities, and thus hold great promise for biomedical applications. Recent advancements have increasingly focused on the integration of non-invasive external stimuli-such as light, heat, electricity, magnetism, and ultrasound-into hydrogel design. These external stimuli-driven catalytic hydrogels can dynamically respond to these stimuli, allowing for high spatial and temporal precision in their application. This capability enables in situ activation, controlled degradation, and catalytic reactions, making them ideal for next-generation clinical interventions. This review discusses the design strategies for external stimuli-driven catalytic hydrogels, concentrating on essential mechanisms of catalytic processes aimed at optimizing therapeutic efficacy. The discussion highlights the importance of precise control over the chemical and physical properties of hydrogels in response to specific stimuli, elucidating the regulatory mechanisms that dictate hydrogel behavior and deepening the understanding of their applications with enhanced spatial and temporal resolution.