Double-network hydrogels for biomaterials: Structure-property relationships and drug delivery

Double-network (DN) hydrogels are high-efficiency energy dissipation materials composed of two contrast interpenetrating polymer networks, and have powerful entanglement with unique soft-wet and interpenetrating networks, can be easily designed as biomaterials to correspond to stimulus-responsive drug delivery systems. The multifunctional DN hydrogels have been extensively studied and used in biomedical and sensor domains. Herein, we reviewed DN hydrogels for biomaterials including stretching and toughening mechanisms related to network topology in the past decade. Furthermore, stimuli-responsive DN hydrogels under the condition of physiological signals (temperature, pH, redox, glucose) were summarized in the domain of drug delivery. An overall view of the preparation methods and design strategies of DN hydrogels were also provided and discussed. These advanced researches related to DN hydrogels provide an outlook on the future development direction of precise drug delivery.