4.5.2. Biofilm Cell Viability MTT Assay

The effect of Ci_SFE_opt and Ci_SFE_pur on P. aeruginosa IBRS P001 biofilm formation was determined by assessing the metabolic activity of live cells using an MTT assay [45]. Biofilms were allowed to develop for 24 h at 37 °C in the presence of Ci_SFE_opt and Ci_SFE_pur (0.25–1.0 MIC). The supernatants were then removed and the biofilms in the microtiter plates were washed with PBS before adding 200 μL MTT reagent (0.5 mg/mL) and incubating at 37 °C in the dark for 2 h. The resulting purple dye was dissolved in 200 μL DMSO and the absorbance was measured at 570 nm in a microtiter plate reader. The percentage inhibition of biofilm cell viability was calculated using the following equation: