Date Published: March 10, 2011
Publisher: SAGE-Hindawi Access to Research
Author(s): Abdul-Majeed Azad, Ryan Hershey, Asem Aboelzahab, Vijay Goel.
In order to impede infection and achieve accelerated wound healing in the postorthopaedic surgery patients, a simple and benign procedure for creating nanotubular or nanofibrillar structure of photoactive TiO2 on the surface of Ti plates and wires is described. The nanoscale TiO2 films on titanium were grown by hydrothermal processing in one case and by anodization in the presence of dilute mineral acids under mild and benign conditions in the other. Confocal microscopy results demonstrated at least 50% reduction in the population of E. coli colonies (concentration 2.15 × 107 cells/mL) on TiO2-coated implants upon an IR exposure of up to 30 s; it required ∼20 min of exposure to UV beam for the same effect. These findings suggest the probability of eliminating wound infection during and after orthopedic surgical procedures by brief illumination of photoactive titania films on the implants with an IR beam.
Disease-carrying pathogens in the body not only destroy healthy tissue but can eventually multiply and spread throughout the blood stream causing infection. Infections can be reduced and healing accelerated by using a nanotechnological approach with photoactive antimicrobial materials.
Titanium—the basic material in implants—was used in two configurations: plates and wires. While plates are ideal for fixed geometry applications, it is anticipated that flexible wires would be a good way to induce healing in those orthopedic injuries where plates are difficult to be inserted. Wires can be folded, twisted, and configured to reach and stay in places where plates cannot. Another point of relevance that justifies using wires is the fact that the hip implants are coated with bead or wire geometry to provide surface for bone in-growth, thus, making antibacterial coatings on intricate yet flexible geometries such as wires valuable. With the same rationale, work is in progress using Ti mesh, and the results of this investigation would be reported elsewhere.
The titania films grown by various techniques described in the previous section on Ti coupons, wires, and on implants were characterized by multiple techniques, such as XRD, SEM, elemental mapping, and energy-dispersive spectroscopy (EDS). It should be pointed out that the identification of titania films grown on Ti substrates by hydrothermal processing and anodization, by XRD proved to be challenging; since the oxide coating in each of these cases was very thin and the X-rays penetrated past the TiO2 surface, thereby showing the diffraction pattern of titanium lying beneath. Hence, the XRD patterns are not shown. Collecting XRD patterns on wire samples was also challenging.
Nanostructured titania coatings were created by mild and benign techniques of hydrothermal processing and anodization on titanium substrates. The films were characterized thoroughly for their structural integrity and microstructural features. Their efficacy for the inhibition of bacterial colonization of E. coli was evaluated by irradiating with a handheld IR laser and UV beams for durations between 12 s and 30 min. The confocal microscopic results demonstrated that IR exposure for short duration was quite effective in bactericidal activities.