Surface modification of titanium implants by silk fibroin/Ag co-functionalized strontium titanate nanotubes for inhibition of bacterial-associated infection and enhancement of in vivo osseointegration

Abstract

Surface modification of surgical grade titanium implants to promote bone cell integration and prevent infection is an urgent problem in orthopedic surgery. The synergistic effect of silk fibroin (SF) and strontium (Sr) has the dual functions of promoting bone formation and inhibiting osteoclasts, and silver (Ag) has excellent antibacterial activity. Therefore, this research uses technologies such as anodizing, hydrothermal synthesis, and layered self-assembly to load SF-Ag into Sr-loaded titanium dioxide nanotubes (SFAgSTN), which makes the titanium surface produce “antibacterial-bone formation” effect. The results of water contact angle and protein adsorption show that SFAgSTN has proper hydrophilicity and protein adsorption capacity, which indicates its excellent biocompatibility. The antibacterial test shows that the functional coating has excellent antibacterial activity because it can inhibit the proliferation of E. coli and S. aureus at the same time. The cross-linking effect of silk fibroin can slow down the release rate of Ag+, avoid the sudden release of ions, extend its antibacterial cycle and reduce the cytotoxicity of Ag+. In vitro, the SFAgSTN coating can promote the adhesion, proliferation and differentiation of MC3T3-E1 osteoblasts, showing good cell compatibility. In vivo, SFAgSTN promotes early osseointegration between Ti substrate and bone tissue. SFAgSTN shows excellent antibacterial, osteogenic differentiation, and new bone formation activity, and can be used as a highly potential anti-infective bone repair implant.