Stimuli-responsive hydrogels for skin wound healing and regeneration

Skin wounds are not only an aesthetic concern but also pose great risks to quality of life and general health. As the most promising biomaterial, hydrogels are three-dimensional polymeric networks and have attracted intense research attention. Hydrogels have developed a diverse range of biomedical and biopharmaceutical applications, owing to their large water content, biocompatibility, tunable mechanical properties, and stimuli-responsiveness. Stimuli-responsive hydrogels are smart materials which exhibit gelation, structural, degradation, performance and function changes when treated with external stimulations. Using these hydrogels to prepare wound dressing is a rapidly growing research area and has exhibited encouraging healing outcomes in small animal models, especially for the treatment of chronic wounds, diabetic wounds, and persistent skin inflammations. The present work gives a detailed and critical analysis on the design strategies, gelation mechanisms, materials selection, stimuli-responsiveness, hydrogel degradation, drug release profiles, and treatment outcomes of wound dressings prepared by the hydrogels with sensitivity to temperature, pH, reactive oxygen species (ROS), glucose, enzymes, and lights. We summarize, analyze, and critically evaluate the most recent publications in this area to explain, compare, and assess why and how various synthetic and bio-polymers are utilized by materials scientists to develop the next generation of skin wound dressing and regeneration.