Biocompatible MoS₂/PDA-RGD coating on titanium implant with antibacterial property via intrinsic ROS-independent oxidative stress and NIR irradiation

To inhibit bacterial infection in situ and improve osseointegration are essentially important for long-term survival of an orthopedic implant, in particular for infection-associating revision surgery. Herein, we fabricate a functional molybdenum disulfide (MoS₂)/polydopamine (PDA)-arginine-glycine-aspartic acid (RGD) coating on titanium (Ti) implant to address above concerns simultaneously. The coating not only improved the osteogenesis of mesenchymal stem cells (MSCs), but also endowed Ti substrates with effective antibacterial ability when exposing to near-infrared (NIR) irradiation. It accelerated glutathione (GSH) oxidation via photothermal energy and induced intrinsic ROS-independent oxidative stress damage deriving from MoS₂ nanosheets. The results displayed that RGD-decorated MoS₂ nanosheets significantly increased the cellular osteogenic behaviors of MSCs via up-regulating osteogenesis-related genes (ALP, Runx2, Col I and OCN) in vitro. Moreover, the functionalized Ti substrates demonstrated great antibacterial efficiency of over 92.6% inhibition for S. aureus and E. coli under NIR-irradiation. Hyperthermia induced by photothermal effect accelerated the GSH consumption and ROS-independent oxidative stress destroyed the integrity of bacteria membranes, which synergistically led to protein leakage and ATP decrease. Furthermore, co-culture experiment showed that S. aureus contamination was efficiently cleaned from MoS₂/PDA-RGD surface after NIR photothermal treatment, while MSCs adhered and proliferated on the MoS₂/PDA-RGD surface. In an S. aureus infection model in vivo, MoS₂/PDA-RGD modified Ti rods killed bacteria with an efficiency of 94.6% under NIR irradiation, without causing damage to normal tissue. More importantly, the MoS₂/PDA-RGD modified Ti implants accelerated new bone formation in comparison with TNT implants in vivo.