Antibacterial effects of zinc oxide nanorod surfaces

Antibacterial coating approaches are being investigated to modify implants to reduce bacterial adhesion and viability in order to reduce implant-associated infection. Nanostructured materials possess unique surface properties, and nanotopographic surfaces have been reported to modulate bacterial adhesion. Zinc oxide (ZnO) films presenting well-controlled nanorod surface structures have recently been developed. To assess the efficacy of ZnO nanorod surfaces as an anti-bacterial coating, we evaluated bacterial adhesion and viability, compared to sputtered ZnO substrates (a relatively flat control) and glass substrates (as a reference). Common implant-associated pathogens, Pseudomonas aeruginosa and Staphylococcus epidermidis were investigated. The number of adherent P. aeruginosa on ZnO nanorod surfaces was found to be reduced compared to glass and sputtered ZnO, while the adherent number of S. epidermidis on the ZnO nanorods was equivalent to glass. Regarding bacteria viability, the ZnO nanorod and sputtered ZnO surfaces demonstrated a modest, but significant bactericidal effect on adherent P. aeruginosa, killing 2.5-fold and 1.7-fold more over the number of dead P. aeruginosa on glass, respectively. A greater bactericidal effect of ZnO substrates on S. epidermidis was found, with sputtered ZnO and ZnO nanorod substrates killing -20-fold and 30-fold more over the number of dead S. epidermidis on glass, respectively. These data support the further investigation and optimization of ZnO nanorod coatings with potential for bacterial adhesion resistance and bactericidal properties.