Dual-functional black phosphorus/hydroxyapatite/quaternary chitosan composite coating for antibacterial activity and enhanced osseointegration on titanium implants

Titanium and titanium alloys have excellent mechanical properties, corrosion resistance and biocompatibility, making them an ideal biomedical implant material with favorable results in clinical applications. However, despite the wide range of applications, they still face some challenges in clinical practice, where poor postoperative osseointegration with surrounding bone tissue and potential bacterial infection problems may lead to implant failure. Black phosphorus nanosheets is a novel two-dimensional nanomaterial that possesses photothermal antibacterial potential similar to that of graphene, and the products of oxidative degradation of black phosphorus play a role in biomineralization to achieve bone-enhancing effects. Therefore, the researchers prepared black phosphorus/hydroxyapatite/quaternary chitosan (BP/HA/QCS) composite coatings on titanium substrates by cathodic electrophoretic deposition to realize the dual functions of antibacterial activity and promotion of osteointegration. The composite coating exhibited good photothermal effect under near-infrared (NIR) irradiation and inhibited E. coli and S. aureus by 94.72 % and 98.94 %, respectively, which could help to solve the potential postoperative infections. The BP/HA/QCS coating had an average surface roughness of 31 nm and a water contact angle of about 11.6 degrees, which was characterized by good hydrophilicity and provided an ideal condition for cellular attachment and growth. In addition, the composite coating has good biocompatibility, which can effectively promote cell proliferation, migration and osteogenic differentiation, providing a good foundation for osseointegration. The results showed that the BP/HA/QCS composite coating exhibited excellent performance in promoting antibacterial activity, osteoblast proliferation and differentiation, and has a broad application prospect in titanium implants.