TITLE:
Environmental Toxicity and Antimicrobial Efficiency of Titanium Dioxide Nanoparticles in Suspension
AUTHORS:
Muriel Bonnet, Christophe Massard, Philippe Veisseire, Olivier Camares, Komla Oscar Awitor
KEYWORDS:
Photokilling Activity, Titanium Nanoparticles, E. coli, L. c. rhamnosus, S. aureus, Hydrogen Peroxide
JOURNAL NAME:
Journal of Biomaterials and Nanobiotechnology,
Vol.6 No.3,
July
17,
2015
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.