Advances in stimuli-responsive injectable hydrogels for biomedical applications

Injectable hydrogels, as a class of highly hydrated soft materials, are of interest for biomedicine due to their precise implantation and minimally invasive local drug delivery at the implantation site. The combination of in situ gelation ability and versatile therapeutic agent/cell loading capabilities makes injectable hydrogels ideal materials for drug delivery, tissue engineering, wound dressing and tumor treatment. In particular, the stimuli-responsive injectable hydrogels that can respond to different stimuli in and out of the body (e.g., temperature, pH, redox conditions, light, magnetic fields, etc.) have significant advantages in biomedicine. Here, we summarize the design strategies, advantages, and recent developments of stimuli-responsive injectable hydrogels in different biomedical fields. Challenges and future perspectives of stimuli-responsive injectable hydrogels are also discussed and the future steps necessary to fulfill the potential of these promising materials are highlighted. The development of new multi-responsive injectable hydrogels with cascades or even synergistic effects will be of great significance in the field of precision medicine.