Antibacterial and Bone Repair Performance of Polypyrrole/HA/Cu/Dex Nanocoatings on Titanium

The surface functional modification of titanium (Ti)-based bone implants is critical for enhancing their clinical application value. However, traditional Cu/Dex nanocoatings face challenges due to the electrostatic aggregation of cations and anions during the preparation process, leading to poor coating uniformity and insufficient crystal phase stability, which severely restrict their antibacterial and osteogenic properties. To address this technical bottleneck, this study proposes an electrochemical codeposition strategy using polypyrrole (PPy) as a spherical template. By innovatively designing an anion-doped system (PO43–, OH–, and Dex–) for the PPy backbone, the electrostatic adsorption behavior of Ca2+ and Cu2+ was precisely controlled. Under near-infrared light irradiation, the Cu nanoparticles loaded on the coating can efficiently convert into thermal energy and generate reactive oxygen species. The synergistic effect of both processes enables highly efficient antibacterial activity. For the first time, synchronous and controllable codeposition of Dex, Cu, and hydroxyapatite (HA) was achieved. The experimental results show that the composite coating (PPy/HA/Cu/Dex) demonstrates unique nanostructural advantages: (1) the size confinement effect of the PPy template results in a crystal phase-stable and uniformly distributed nanocoating; (2) the light-responsive and synergistic ion-release mechanism allows the coating to achieve a 100% kill rate for Escherichia coli and Staphylococcus aureus within 10 min of visible light irradiation; and (3) the synergistic effect of multiple components significantly enhances osteoblast activity, with scanning electron microscope characterization showing typical spreading morphology of cells on the coating surface, as well as increased matrix mineralization and alkaline phosphatase activity. Through material system design and deposition process innovation, this work successfully constructs a multifunctional nanocoating with rapid antibacterial and sustained osteogenic activity, providing a strategy for addressing the key challenges in the surface functionalization of medical Ti implants.