ROS-responsive hydrogel coating modified titanium promotes vascularization and osteointegration of bone defects by orchestrating immunomodulation.

Ideal titanium implants are required to participate in bone repair actively to improve in situ osteointegration. However, the traditional surface functionalization methods of titanium implants are difficult to both achieve the active regulation and long-term stability of bioactive components. Here, a novel functionalized titanium which loaded with thymosin β4 (Tβ4) and covered by a hydrogel coating was designed and evaluated. A strong adhesion between the coating and the titanium substrate was realized by the synergistic action of borate ester bonds and surface topological structure. The hydrogel coating also achieved an in vivo adhesion between implant and tissue through hydrogen bonds and borate bonds. In addition, based on the ROS response property of borate bonds, the implant can release Tβ4 in response to the immune reaction of bone healing by regulating the polarization of macrophages, thereby reducing the fibrosis formation around the implant interface and promoting vascularization and osteointegration of bone defects.