Generation of Surface Nanotubes on Titanium Kirschner Wire for the Enhanced Release of Antibacterial Drug

Titanium and its alloys are widely used in medical applications for their excellent properties such as biocompatibility, low toxicity, high chemical stability, good fatigue strength, and resistance to corrosion. Unfortunately, those properties do not always prevent the human organism to attack and isolate Ti implants causing explantation and, therefore high costs and inconvenience for the patient. That is why a surface modification is often performed to improve the integration with the tissues without affecting the bulk properties of the material. Lately, researchers focused their attention on the functionalization of the surface at the nanoscale, which has proven to offer a wide range of applications in many different fields. The goal of this study was to obtain titanium dioxide nanotubes (TNTs) on the surface of titanium implants by anodization. Furthermore, their properties were exploited to load vancomycin in a solution for a drug release test in a potential antibacterial application of the implant in vivo. The anodization was performed in an ethylene glycol-based solution (98 vol%) containing 0.3 wt% ammonium fluoride (NH4F) and 2 vol% deionized water. The reaction took place for 60 min at a constant voltage of 50 V with a sweep rate of 1 V/s. The resulting nanotubes were approximately 80 nm in diameter and hypothetically 2 μm long. The length was solely estimated since we could not obtain cross-sectional images. Compared to a smooth implant, the surface area of the anodized wire increased by 50 times. Raman spectroscopy did not appear to be a feasible alternative for quantitative analysis of antibiotics in solution. Hence, we opted for ultraviolet-visible (UV-Vis) spectroscopy. The vancomycin solution was loaded in the implant and a release test was performed. The anodized wires showed to release nearly 80% more antibiotic after 2 hours compared to smooth titanium.