Preparation of a composite coating of bimodal TiO2 nanotubes with deposited Ag nanoparticles and its biological performance

Abstract

Titanium implants are vulnerable to bacterial infections due to its poor antibacterial capacity, making it essential to enhance the antimicrobial ability to ensure long-term clinical effectiveness. In this study, composite coatings of bimodal TiO₂ nanotubes, deposited with Ag nanoparticles, were prepared on TC4 substrates using a two-step anodization and hydrothermal method. The adhesion strength of the TiO₂ nanotube coatings was measured to be 1B prepared with the one-step anodization but 5B with the two-step anodization, indicating that the adhesion strength of the coating obtained through two-step anodization was improved significantly. Furthermore, the microstructure, surface hydrophilicity, corrosion resistance, and antimicrobial properties of the sample surface were tested. The results showed that nanotubes consist of irregular, circular tubes with an average wall thickness of 20 nm. AgNPs were deposited and uniformly dispersed on the surface of the TiO₂ nanotubes. As the Ag concentration increased, the nanotube wall thickness increased by 5–30 nm. The titanium dioxide nanotube coating obtained through anodizing was superhydrophilic, with a water contact angle of 10°. This angle slightly increased after Ag-deposited but the coating retained its overall hydrophilic properties. The Ag-deposited TiO₂ nanotube coatings exhibit excellent corrosion resistance in simulated oral fluids. Furthermore, the coatings demonstrated strong antibacterial efficacy, achieving maximum inhibition rates of 67.2 % against Escherichia coli and 85.6 % against Staphylococcus aureus.