The potential eco-toxicity of fourteen different
nanosized titanium dioxide (TiO
2) particles was studied
using Gram-positive
Bacillus subtilis
and Gram-negative
Escherichia coli
(ATCC K12) as test organisms. These
photosensitive nanoparticles (NPs) were found to be
harmful to the organisms studied at different degrees; the
antibacterial activity increased with primary particle size,
reached the maximum level in the range of 16–20 nm, and
then decreased as the primary particle size increased. The
presence of light played a significant role on the eco-toxicity
of the nano-TiO
2 particles under most conditions
studied, presumably due to the generation of reactive
oxygen species (ROS). However, bacterial growth was
inhibited also under dark condition, indicating that mechanisms
other than photocatalytic ROS were responsible for
the toxic effect. Results highlight the need for caution
during the use and disposal of manufactured NPs as to
prevent unintended environmental impacts, as well as the
importance of further research on the mechanisms and
factors that control the toxicity of NPs toward aquatic
organisms.
