Abstract
The aim of this work was to evaluate the photokilling efficiency of synthesized titanium dioxide nanoparticles in suspension. Two strains of Escherichia coli, Lactobacillus casei rhamnosus and Staphylococcus aureus were used as probes to test the photokilling activities of the nanoparticles. The toxicity effects of TiO2 nanoparticles on the environment were determined by a standard test using gram-negative bioluminescent bacteria Vibrio fischeri. The antimicrobial activity of these nanoparticles (NPs) was then investigated versus NPs concentration, UV irradiation time and micro- organism strains. We evaluated the LC50 values of the nanoparticles suspension by counting the Colony-Forming Units. Results highlighted the differences in bacteria sensitivity facing photokilling treatment induced by the irradiation of anatase TiO2 nanoparticles suspension. At the concentration of 1 g·L-1 TiO2, tested bacteria were killed after 30 minutes of photo-treatment. Using different TiO2 concentrations, the Staphylococcus aureus gram-positive/catalase-positive bacteria were more resistant than gram-negative/catalase-positive ones or gram-positive/catalase-negative bacteria. An effect of UV irradiation was evaluated by the quantification of hydrogen peroxide generated by the photolysis of water molecules in presence of the nanoparticles with or without the most resistant bacterium (S. aureus). After 30 minutes with UV irradiation in these two conditions, the concentration of hydrogen peroxide was 35 μM in presence of 1.2 g·L-1 TiO2 suspension. This result suggested that the resistance mechanism of S. aureus was not due to an extracelullar H2O2 enzymatic degradation.
Highlights
Photokilling of pathogen species is a promising alternative compared to conventional disinfection process
The first step consists in the chelation of the titanium isopropoxide with an organic ligand, acetylacetone
This reaction is a substitution of alkoxy group of the titanium alcoxyd molecular species by beta diketone ligands
Summary
Photokilling of pathogen species is a promising alternative compared to conventional disinfection process. When chemical cleaning products are not effective or dangerous, a disinfection protocol based on the irradiation of photoactive species can be interesting. Contrary to other cleaning treatments, such as chlorination [1] [2] and ozonation [3]-[5], less toxic by-products are generated and the process can remain effective for a long time. Many studies have attributed to ROS production, the nanoparticles bactericidal effect generated under UV light [19] [20]. Recent reports have shown that TiO2 nanoparticles can induce the oxidative stress defense of the cell against endogenous ROS like H2O2, which can sequentially elicit lipids, proteins and DNA damage [21][23]. Catalase is a tetrameric heme-containing enzyme, and is one of the key antioxidant enzymes present in almost every aerobic organisms, catalyzing the breakdown of hydrogen peroxide to water and molecular oxygen to protect cells against the toxic effects of hydrogen peroxide [29]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
