Engineering the surfaces of orthopedic implants with osteogenesis and antioxidants to enhance bone formation in vitro and in vivo

Limited osteointegration of orthopedic implants with surrounding tissues has been the leading issue until the failure of orthopedic implants in the long term, which could be induced by multiple factors, including infection, limited abilities for bone formation and remodeling, and an overstressed reactive oxygen species (ROS) environment around implants. To address this challenge, a multifunctional coating composed of tannic acid (TA), nanohydroxyapatite (nHA) and gelatin (Gel) was fabricated by a layer-by-layer (LBL) technique, into which TA, nHA, and Gel were integrated, and their respective functions were utilized to synergistically promote osteogenesis. The fabrication process of (TA@nHA/Gel)n coatings and related bio-multifunctionalities were thoroughly investigated by various techniques. We found that the (TA@nHA/Gel)n coatings showed strong antioxidant activity and accelerated cellular attachment in the early stage and proliferation in the long term, largely enhancing osteogenesis in vitro and promoting bone formation in vivo. We believe our findings will guide the design of orthopedic implants in the future, and the strategy developed here could pave the way for multifunctional orthopedic implant coating and protein-related coatings with various potential applications, including biosensors, catalysis, tissue engineering, and life science.