Intelligent hydrogels and their biomedical applications

Intelligent biomaterials can modify their properties in response to physical, chemical, and biological stimuli. These smart characteristics drive the innovation of biomaterials in therapy and diagnostics for detecting diseases and providing treatment at early stages. Mainly, hydrogels have gained significant interest in developing smart materials due to their excellent biocompatibility and ability to interact with body fluids that host condition-specific stimuli. Temperature, pressure, pH, light, ROS, cell metabolites, and other physicochemical factors specific to specific disease conditions were studied as major stimuli for designing intelligent biomaterials. The stimuli-responsive characteristic mainly depends on the sensitivity of the biomaterial to the stimuli factor and the tunable macromolecular structure of the materials. The method of biomaterial fabrication is critical in determining the physical and chemical properties of the biomaterial. Surface functionalisation, material blending, and crosslinking are commonly used to synthesise intelligent hydrogels to change the macromolecular structure. The impact and mechanism of these fabrication methods on the macromolecular structure and stimuli responsiveness of intelligent materials remain unidentified. This review focuses on strategies for transforming conventional hydrogels into intelligent hydrogels, their concerning mechanisms of stimuli-responsiveness and their biomedical applications.