Preparation and performance of antibacterial and bioactive silver nanoparticle/nano-hydroxyapatite gradient composite gel coatings on Ti implants.

Developing bioactive and antibacterial composites to address clinical challenges such as bacterial infection and mechanical loosening for titanium-based implants remains a significant challenge at present. In this research, sodium alginate (SA) gel coatings incorporated with varying concentrations of silver nanoparticles (AgNPs) and nano-hydroxyapatite (nHA) were developed on titanium surfaces via an in-situ gelation strategy. The physical properties of the SA-nHA-Ag gel layers were closely related to the nHA content. Electrochemical evaluation revealed that the composite coating enhanced the corrosion resistance of titanium, specifically, the optimal Ti@SA-nHA1.0 coating significantly reduced the corrosion current density to 0.008 ± 0.002 μA/cm2 and increased the potential to -0.036 ± 0.004 V, compared to pure Ti (0.402 ± 0.003 μA/cm2 and -0.329 ± 0.006 V). Furthermore, the in vitro mineralization assays indicated that the SA-nHA coating possessed the ability to induce hydroxyapatite precipitation. Notably, the Ti@SA-nHA1.0-Ag10 composite exhibited the most balanced performance, with an antibacterial rate of 82.27% against Escherichia coli and 81.88% against Staphylococcus aureus. It also displayed excellent hemocompatibility with a hemolysis ratio of 2.80%, remaining well below the 5% safety threshold. Endothelial cell migration assays showed a 24-hour wound healing rate of approximately 61% for the composite, notably exceeding the 38% of the pure Ti substrate. Combined with in vitro cell culture, the composite demonstrated no cytotoxicity, maintaining day-5 cell proliferation optical density (OD) values consistently higher than those of the pure Ti control.