Interfacial Activation of Microgroove-Supported TiO2 Nanotube Arrays for Stable Ag Nanoparticle Retention on Ti–6Al–4V Alloy Surfaces

Abstract Titanium alloys are widely used as load-bearing biomedical materials; however, their bioinert oxide surfaces and susceptibility to bacterial colonization remain important challenges for surface functionalization. More critically, the weak interfacial retention of antibacterial nanoparticles on TiO2-based nanostructures often limits long-term antibacterial durability. In this work, femtosecond laser texturing followed by anodization was used to construct hierarchical microgroove-TiO2 nanotube arrays on Ti–6Al–4V (TC4) surfaces. Silver nanoparticles (AgNPs) were subsequently deposited in situ through a reactive ion etching (RIE)-assisted hydrothermal strategy, yielding binder-free Ag-functionalized micro/nanostructured titanium surfaces. The effects of hydrothermal temperature on AgNP nucleation, particle-size distribution, surface coverage, and wettability were systematically investigated. To evaluate AgNP anchoring stability, accelerated disturbance tests involving sandpaper abrasion, water-flow impact, and ultrasonic agitation were performed. Compared with the hydrothermally treated surface without RIE pretreatment, the RIE-pretreated surface showed higher residual Ag content after mechanical and hydrodynamic challenges, indicating enhanced AgNP retention. The optimized RIE-pretreated Ag-loaded surface (EAFSL@Ag) exhibited sustained Ag+ release, with a cumulative concentration of 0.52 ppm after 21 days in phosphate-buffered saline. Against Escherichia coli and Staphylococcus aureus, EAFSL@Ag achieved antibacterial efficiencies exceeding 99% within 24 h. These results suggest that RIE-assisted interfacial activation of TiO2 nanotubes promotes Ag+ adsorption, heterogeneous AgNP nucleation, and nanoparticle retention, providing a scalable surface-engineering strategy for durable antibacterial titanium surfaces.