Near-infrared light-responsive Cu2O@CuFeS2-hydroxyapatite-chitosan based antibacterial coating on titanium bioimplant

Bacterial infection over the titanium (Ti) bioimplants has been challenging, and it warrants re-surgery, which subsequently affects human health. In the present work, Cu2O, CuFeS2, and Cu2O@CuFeS2 composite was synthesized and used as a photothermal agent and fabricated their coatings over Ti surface using chitosan (CS)-hydroxyapatite (HA) matrix for the improvement of antibacterial activity under near-infrared (NIR, λ = 808 nm) irradiation and evaluated corrosion properties. The composite, CuFeS2 micro-flower (CuFeS2 MF) incorporated with Cu2O nanoparticles in the porous structure, showed a wide optical absorption window in the NIR region, resulting in the photothermal conversion efficiency of ~39 % under NIR light irradiation. Electrochemical studies indicated a variation in corrosion behavior for the coated and uncoated Ti, and its passive region remains similar in phosphate buffer saline (PBS) solution. Further, the prepared coatings displayed an excellent coating adhesion property over Ti. With the external stimuli of NIR light irradiation, the Cu2O@CuFeS2 composite exhibited a high antibacterial efficacy against S. aureus (~98.5 %) and E. coli (~96 %). The combination of the photothermal effect (CuFeS2) and bactericidal effect of Cu2O via cell membrane damage and ROS generation was found to be the cell death mechanism. The cytotoxicity assay of Cu2O@CuFeS2 composite in the presence of L929 cells ascertained their cell viability by >80 % at the optimized conditions, indicating a negligible toxicity level. Notably, the produced coating of CS-HA-Cu2O@CuFeS2 showed better antibacterial efficacy against S. aureus (~88.4 %) and E. coli (~84 %) under NIR light irradiation compared to without light. The CS-HA matrix also contributed to a marginal antibacterial activity due to the interactions of the charged amine group of CS with the charged group of the bacterial cell membrane.