Preparation and application of environmentally-responsive hydrogels in tissue engineering

Environmentally responsive hydrogels, also referred to as smart hydrogels, possess the remarkable capability to detect changes in specific signals and stimuli within the external environment. Based on their distinct response to external stimulation, these hydrogels can be categorized as temperature-sensitive hydrogels, pH-sensitive hydrogels, light-sensitive hydrogels, pressure-sensitive hydrogels, electric field-sensitive hydrogels, and more. Responsive hydrogels can be synthesized using various methods depending on the mechanism and conditions of monomer polymerization. These methods includeatomic transfer radical polymerisation (APRT method), cryo-polymerisation, ultrasonic radiation polymerisation preparation method, free radical polymerisation in aqueous solution, foam dispersion polymerization, reversible addition-breakage chain transfer polymerization (RAFT). These methodologies offer diverse approaches to fabricate responsive hydrogels with tailored properties. These responsivehydrogels demonstrate outstanding properties, （e.g., excellent biocompatibility, suitable mechanical properties, environmentally-responsive）thus offering promising prospects for their application in the field of tissue engineering. This paper systematically presents the characteristics, preparation methods, and tissue engineering applications of various types of responsive hydrogels. By providing a theoretical foundation and practical experiences, it aims to contribute to future research on responsive hydrogels in the field of biomedicine.