Figure 3. Effect of TiO₂ NPs on biofilm formation by Listeria monocytogenes strains.

Wells of polystyrene microtiter plates were conditioned with TSB-YE medium or with TiO₂ NPs at 0.08, 0.8, 8, and 80 µg/ml. Biofilm cells were indirectly quantified by crystal violet staining and absorbance measurements at 590 nm. Values are expressed as mean ± SD. All experiments were carried out in sextuple and repeated in two independent set of experiments. Asterisks denote statistically significant increase of the Listeria population compared to control bacterial cells (*p<0.05; **p<0.01; ***p<0.001).