Hydrogel coatings for titanium implants: From smart stimuli-responsive strategies to multimodal bone regeneration

Titanium implants are widely used in orthopedic surgery due to their excellent biocompatibility and mechanical properties. However, their long-term clinical success is often limited by complications such as postoperative infection, chronic inflammation, and inadequate osseointegration. In recent years, hydrogels have been extensively explored for tissue regeneration because of their biological activity and functional versatility. One emerging application is the surface modification of titanium implants, in which hydrogel coatings can be engineered to improve implant adaptability and osseointegration under complex pathological conditions. This review summarizes the classification, fabrication methods, stimuli-responsive features, and emerging bone-regenerative applications of hydrogel coatings on titanium implants. We also discuss the prospects and challenges of functionalized hydrogel coatings for titanium implants in clinical translation. By examining the latest advances in this rapidly evolving research area, the review aims to catalyze innovation in implant-based bone repair and therapeutic applications.