Figure 5

Toxicity and phototoxicity evaluation of TiO ₂ nanoparticles against E. coli . (a) E. coli CFUs after exposure to 200 μg/mL of chemical () and biological () TiO₂ nanoparticles (control ). (b) E. coli CFUs after treatment with 200 μg/mL of chemical () and biological () TiO₂ nanoparticles exposed to UV light (control exposed to UV , control unexposed to UV ). The arrow in a indicates the time in which cells were treated with TiO₂ nanoparticles.