Photothermal Antibacterial Effect of Gold Nanostars Coating on Titanium Implant and Its Osteogenic Performance.

Introduction: Titanium implants are widely used in dentistry due to their mechanical strength and biocompatibility, yet their biological inertness and lack of antimicrobial properties contribute to high failure rates from poor osseointegration and infections like peri-implantitis. To address these limitations, this study developed a gold nanostar (GNS)-coated titanium implant (Ti-GNS) and systematically evaluated its osteogenic and photothermal antibacterial functions. The research aimed to enhance osseointegration through surface modification while leveraging GNS's photothermal effect for on-demand antibacterial activity, offering a dual-functional strategy to improve implant performance.

Methods: GNSs were synthesized and anchored onto titanium surfaces through surface modification via silanization. Material characterization included morphological, elemental, and photothermal analyses. In vitro experiments assessed osteogenic differentiation of bone marrow stem cells (ALP activity, mineralization, gene/protein expression) and antibacterial efficacy against Staphylococcus aureus and Escherichia coli under NIR. In vivo performance was evaluated by implanting Ti, Ti-Si (silanized), and Ti-GNS in rat femurs, followed by micro-CT and histological analysis.

Results: Silanization and GNS deposition optimized titanium surfaces by significantly enhancing wettability and nanoscale roughness, while photothermal activation under NIR irradiation demonstrated temperature-dependent responsiveness. Furthermore, in vivo evaluations confirmed Ti-GNS biocompatibility and revealed enhanced osteogenic potential through promoted cell adhesion, proliferation, as well as osteoinductive marker expression. Notably, the Ti-GNS group exhibited superior osseointegration alongside stable antimicrobial efficacy post-NIR exposure.

Conclusion: GNS-coated titanium implants synergistically enhance osteogenesis and provide NIR-responsive antibacterial activity. The modified surface improved cell interactions and bone formation while achieving near-complete bacterial elimination under light activation. This dual-functional strategy addresses key challenges in implantology, though long-term stability and clinical translation require further investigation. The study establishes a foundation for photothermal antimicrobial implants with significant potential in dental applications.