Antimicrobial and antibiofilm efficacy of self-cleaning surfaces functionalized by TiO photocatalytic nanoparticles against Staphylococcus aureus and Pseudomonas putida.

A photocatalytic sol of TiO nanoparticles has been used for creating self-cleaning antimicrobial flat and porous glass surfaces. The substrates were irradiated to study their photocatalytic properties and behavior in the presence of biofilm-forming bacteria. Smooth glass surfaces and glass microfiber filters were covered with 1.98×10±1.5×10gcm and 8.55×10±3.0×10gcm densities, respectively. Self-cleaning properties were analyzed using the methylene blue 365nm UV-A photodegradation test. TiO-coated filters achieved rapid and complete photodegradation of methylene blue because of the better TiO dispersion with respect to the glass slides. The effect of functionalized surfaces on the growth and viability of bacteria was studied using the strains Staphylococcus aureus and Pseudomonas putida. After irradiation (2h, 11.2Wm, 290-400nm), the initially hydrophobic surface turned hydrophilic. The antibacterial effect led to extensive membrane damage and significant production of intracellular reactive oxygen species in all TiO-loaded irradiated specimens. The reduction of cell viability was over 99.9% (>3-log) for TiO on glass surfaces. However, the polymeric extracellular matrix formed before the irradiation treatment was not removed. This study highlights the importance of bacterial colonization during dark periods and the difficulty of removing the structure of biofilms.