Reduced graphene oxide-mediated electron-hole separation using titanium dioxide increases the photocatalytic antibacterial activity of bone scaffolds

Fast electron–hole recombination issues during titanium dioxide (TiO2) photocatalysis limit its application in preventing bacterial infection during bone defect repair. In this study, TiO2@reduced graphene oxide (rGO) composites were synthesized using a hydrothermal method in which rGO, which possesses very high electrical conductivity, promotes the separation of photoelectron–hole pairs of TiO2, thus improving the efficiency of photocatalytic production of reactive oxygen species (ROS). Subsequently, TiO2@rGO composites were introduced into poly-L-lactic acid (PLLA) to prepare bone scaffolds with photocatalytic antibacterial function via selective laser sintering. The results showed that TiO2 grew on the surface of rGO and formed a covalent bond connection (Ti–O–C) with rGO. A decreased electrochemical impedance of TiO2@rGO composites was observed, and the transient photocurrent intensity increased from 0.05 to 0.5 µA/cm2. Analysis of electron spin resonance found that the photocatalytic products of TiO2 were ·OH and ·O2−, two kinds of ROS capable of killing bacteria via disrupting the structure of the bacterial membrane in vitro. Antibacterial experiments showed that the PLLA/TiO2@rGO scaffolds had good antibacterial properties against Escherichia coli and Staphylococcus aureus. Finally, we report that these scaffolds exhibited both enhanced mechanical properties due to the addition of TiO2@rGO as a reinforcement material and good biocompatibility during cell proliferation.