Near-infrared laser-mediated drug release and antibacterial activity of gold nanorod–sputtered titania nanotubes

The infection control of implants is one of the hot issues in the field of medicine and dentistry. In this study, we prepared gold nanorod–sputtered titania nanotubes on titanium surface, which is the main component of implant material, and aimed to estimate the remote-controlled tetracycline release and resulting antibacterial effects of gold nanorod–sputtered titania nanotubes using near-infrared laser irradiation. Gold nanorods prepared by ion plasma sputtering (aspect ratio = 1:3) showed optical properties like those of chemically synthesized gold nanorods, exhibiting photothermal effects in the near-infrared region, as demonstrated using field-emission scanning electron microscopy, transmission electron microscopy, and diffuse ultraviolet–visible–near-infrared spectrophotometry. In addition, a 2 wt% tetracycline/polycaprolactone mixture was found to be the most suitable experimental group to demonstrate the biological compatibilities and antibacterial activities. The results of antibacterial agar diffusion tests and near-infrared-mediated tetracycline release tests in vivo confirmed that remote-controlled tetracycline elution using near-infrared laser irradiation was highly effective. Therefore, gold nanorod–sputtered titania nanotubes would be expected to enable the continued use of the photothermal therapy of gold nanorods and extend the limited use of titania showing photocatalytic activity only within the ultraviolet-to-near-infrared region.