In Situ Electrochemical Fabrication of Photoreactive Ag–Cu Bimetallic Nanocomposite Coating and Its Antibacterial-Osteogenic Synergy

In response to the issues of infection and poor bone integration in orthopedic implants, this study successfully developed a multifunctional composite coating composed of poly(pyrrole) (PPy), hydroxyapatite (HA), and silver-copper (Ag-Cu) bimetallic nanoparticles (NPs) on titanium (Ti) substrates using an electrochemical in situ deposition technique. Upon near-infrared light (NIR, 808 nm) stimulation, this coating exhibits synergistic antibacterial and osteogenic effects through photothermal (PTT) and photodynamic (PDT) processes. Characterization results indicate that the Ag-Cu NPs are uniformly distributed within the coating (Ag: 1.7 wt %, Cu: 2.0 wt %), and the concentrations of Ag⁺ and Cu²⁺ released (2.9526 mg·L^-1 and 0.1932 mg·L^-1, respectively) are significantly lower than the cytotoxic threshold (10 mg·L^-1). PTT tests reveal that the coating achieves a PTT conversion efficiency of 33.8%, with the temperature rising to 49.9 °C within 10 min under 1.0 W·cm^-2 irradiation, generating high levels of singlet oxygen (¹O₂). This leads to a 100% bactericidal rate against <i>Escherichia coli</i> and <i>Staphylococcus aureus</i>. In vitro biocompatibility assays show that the gradient release of HA and the synergistic effect of Ag⁺/Cu²⁺ significantly enhance the proliferation of bone marrow mesenchymal stem cells (BMSCs), with optical density reaching 1.49 after 7 days of culture. Additionally, osteogenic differentiation is promoted, as evidenced by a 2.9-fold increase in alkaline phosphatase (ALP) activity and a 2.1-fold increase in calcium nodule formation. Western blot analysis further confirmed that the coating induces the high expression of Runx2 via activation of the Wnt/β-catenin signaling pathway, thereby driving osteogenesis. This study presents a strategy for the development of smart implants with both efficient antibacterial and bone integration capabilities.