Antibacterial activity of standard and N-doped titanium dioxide-coated endotracheal tubes: an in vitro study

OBJECTIVE: The aim of this study was to assess the antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa of two nanoparticle endotracheal tube coatings with visible light-induced photocatalysis. METHODS: Two types of titanium dioxide nanoparticles were tested: standard anatase (TiO(2)) and N-doped TiO(2) (N-TiO(2)). Nanoparticles were placed on the internal surface of a segment of commercial endotracheal tubes, which were loaded on a cellulose acetate filter; control endotracheal tubes were left without a nanoparticle coating. A bacterial inoculum of 150 colony forming units was placed in the endotracheal tubes and then exposed to a fluorescent light source (3700 lux, 300-700 nm wavelength) for 5, 10, 20, 40, 60 and 80 minutes. Colony forming units were counted after 24 hours of incubation at 37°C. Bacterial inactivation was calculated as the percentage reduction of bacterial growth compared to endotracheal tubes not exposed to light. RESULTS: In the absence of light, no relevant antibacterial activity was shown against neither strain. For P. aeruginosa, both coatings had a higher bacterial inactivation than controls at any time point (p < 0.001), and no difference was observed between TiO(2) and N-TiO(2). For S. aureus, inactivation was higher than for controls starting at 5 minutes for N-TiO(2) (p = 0.018) and 10 minutes for TiO(2) (p = 0.014); inactivation with N-TiO(2) was higher than that with TiO(2) at 20 minutes (p < 0.001), 40 minutes (p < 0.001) and 60 minutes (p < 0.001). CONCLUSIONS: Nanosized commercial and N-doped TiO(2) inhibit bacterial growth under visible fluorescent light. N-TiO(2) has higher antibacterial activity against S. aureus compared to TiO(2).