pH interferes in photoinhibitory activity of curcumin nanoencapsulated with pluronic® P123 against Staphylococcus aureus.

Microbial contamination control is a public health concern and challenge for the food industry. Antimicrobial technologies employing natural agents may be useful in the food industry for these purposes. This work aimed to investigate the effect of photodynamic inactivation using curcumin in Pluronic® P123 nanoparticles (Cur/P123) at different pH and blue LED light against Staphylococcus aureus. Bacterial photoinactivation was conducted using different photosensitizer concentrations and exposure times at pH 5.0, 7.2 and 9.0. A mixture design was applied to evaluate the effects of exposure time (dark and light incubation) on the photoinhibitory effect. S. aureus was completely inactivated at pH 5.0 by combining low concentrations of Cur/P123 (7.80-30.25 μmol/L) and light doses (6.50-37.74 J/cm). According to the mathematical model, dark incubation had low significance in bacterial inactivation at pH 5.0 and 9.0. No effect in bacterial inactivation was observed at pH 7.2. Cur/P123 with blue LED was effective in inactivating S. aureus. The antimicrobial effect of photodynamic inactivation was also pH-dependent.