Diverse types of nanoparticles show photocatalytic properties, where the absorption of an specific wavelength is used for generating (accelerating) a chemical reaction, including destruction of microbial cells, generally due to reactive oxygen species (ROS) generation (Nica et al., 2017). In this sense, TiO2NPs, containing 1% Fe and N, structured as a thin layer on a polystyrene surface, have demonstrated inactivation of bacterial cells ( coli, Enterococcus faecalis, P. aeruginosa, S. aureus) after sun light exposure. When exposed to visible, and specially to UV light, these nanoparticles also showed antibiofilm activity in the case of E. coli, P. aeruginosa and S. aureus, which inhibition values in the order of 2–32 μg/mL (Nica et al., 2017). Similar TiO2 nanoparticles, although containing Ag instead of Fe and N, have been tested successfully on stainless steel surfaces (coupons) in order to prevent bacterial biofilm formation, a method of potential application in beverage industry pipelines (Priha et al., 2011). This coating strategy has been more effective in the case of Gram-negative bacteria (such as Pseudomonas fluorescens) than in the case of Gram-positive ones (such as Lactobacillus paracasei) (Priha et al., 2011).
ZnO nanoparticles generated with the help of Ulva lactucaaqueous extract have been also described as excellent photocatalysts, absorbing light at 325 nm wavelength. These are able to generate ROS in contact with bacterial cells, causing 80% reductions in biofilms formed by Bacillus pumilus, B. licheniformis, E. coli or Proteus vulgaris (Ishwarya et al., 2018).
Photocatalytic nanoparticles have demonstrated strong antibiofilm effects against important human pathogens as well. For example, 10-days-old monocytogenesbiofilms, generated after incubation at 16°C on stainless steel or glass surfaces, have shown reductions of 3 log CFU/cm2 after 180 min and 120 min irradiation with 395 nm wavelength, respectively (Chorianopoulos et al., 2011). This novel technique demonstrates the feasibility of biofilm removal using self-disinfecting modified surfaces in industrial environments, where stainless steel and glass surfaces are common.
Further reading on photocatalysts
Nica, I. C., Stan, M. S., Popa, M., Chifiriuc, M. C., Lazar, V., Pircalabioru, G. G., et al. (2017). Interaction of new-developed TiO2-based photocatalytic nanoparticles with pathogenic microorganisms and human dermal and pulmonary fibroblasts. Int. J. Mol. Sci. 18:249. doi: 10.3390/ijms18020249.
Priha, O., Laakso, J., Tapani, K., Levänen, E., Kolari, M., Mäntylä, T., et al. (2011). Effect of photocatalytic and hydrophobic coatings on brewery surface microorganisms. J. Food Prot. 74, 1891–1901. DOI: 10.4315/0362-028X.JFP-11-008.
Ishwarya, R., Vaseeharan, B., Kalyani, S., Banumathi, B., Govindarajan, M., Alharbi, N. S., et al. (2018). Facile green synthesis of zinc oxide nanoparticles using Ulva lactuca seaweed extract and evaluation of their photocatalytic, antibiofilm and insecticidal activity. J. Photochem. Photobiol. B 178, 249–258. DOI: 10.1016/j.jphotobiol.2017.11.006.
Chorianopoulos, N. G., Tsoukleris, D. S., Panagou, E. Z., Falaras, P., and Nychas, G. J. (2011). Use of titanium dioxide (TiO2) photocatalysts as alternative means for Listeria monocytogenes biofilm disinfection in food processing. Food Microbiol. 28, 164–170. DOI: 10.1016/j.fm.2010.07.025.
This page is still under development. Can you help us complete it? Please contact us.