Antibacterial Surface Coating for Bone Scaffolds Based on the Dark Catalytic Effect of Titanium Dioxide.

Biomaterials which promote tissue integration and resist microbial colonisation are required in bone tissue engineering to prevent biomaterial-associated infections. Surface modification of established materials for bone tissue engineering, such as TiO2, have emerged as promising anti-infective strategies. Interestingly, the antibacterial activity of TiO2 in the form of particles can be enhanced by combining it with H2O2, even in the absence of irradiation. However, it remains unknown whether TiO2 surfaces elicit a similar effect. In this study, the antibacterial effect of porous TiO2 scaffolds generated by the catalytic decomposition of H2O2 in the absence of light (dark catalysis) was investigated. Porous ceramic foams were fabricated and sol-gel coated for high catalytic activity. Degradation of methylene blue in the presence of 3% H2O2 increased by 80% for the sol-gel-coated surfaces. The degradation kinetics indicate that intermediate free radicals that form at the liquid-TiO2 interface are responsible for the oxidative behavior of the surface. TiO2 surfaces were further pretreated with 30% H2O2 for prolonged oxidative behavior. The biological response toward such surfaces was assessed in vitro. S. epidermidis biofilms formed on modified surfaces showed reduced viability compared to nonmodified surfaces. Further, the same surface modification showed no cytotoxic effects on MC3T3 preosteoblasts. However, the results from the conducted genotoxicity assay were inconclusive, and further studies are needed to exclude ROS-mediated DNA damage. To conclude, this study provides evidence that a simple surface modification based on the dark catalytic effect of TiO2 can be used to create antibacterial surface properties for ceramic bone scaffolds.