Advances in the Stimuli-Responsive Injectable Hydrogel for Controlled Release of Drugs

The stimuli-responsiveness of injectable hydrogel has been drastically developed for the controlled release of drugs and has achieved encouraging curative effects in a variety of diseases including wounds, cardiovascular diseases, and tumors. The gelation, swelling, and degradation of such hydrogels respond to endogenous biochemical factors (such as pH, reactive oxygen species, glutathione, enzymes, glucose) and/or to exogenous physical stimulations (like light, magnetism, electricity, and ultrasound), thereby accurately releasing loaded drugs in response to specifically pathological status and as desired for treatment plan, and thus improving therapeutic efficacy effectively. This paper gives a detailed introduction of recent progresses in responsive injectable hydrogels and focuses on the design strategy of various stimuli-sensitivities and their resultant alteration of gel dissociation and drug liberation behavior. Their application in disease treatment is also discussed.