Antimicrobial photodynamic therapy in dentistry using an oil-in-water microemulsion with curcumin as a mouthwash

Antimicrobial photodynamic therapy (PDT) has emerged as an alternative therapeutic strategy to conventional procedures using antibiotics. A mouthwash based on a microemulsion with curcumin for disinfecting the oral cavity in combination with PDT was developed.

A pseudo-ternary phase diagram was constructed to select the microemulsion, and a physicochemical characterization of the selected formulation was performed. Curcumin was quantified using spectrophotometry. The stability of the formulation with curcumin was evaluated after storage for 60 days at 40 °C, and the in vitro effectiveness of the formulation associated with PDT was evaluated using a light-emitting diode at 430 nm (blue) with two irradiation times (10 and 30 min) on biofilms of Candida albicans, methicillin-resistant Staphylococcus aureus (MRSA), and Escherichia coli.

The formulation registered a pH of 6.24, apparent viscosity of 1.64 cP, Newtonian rheological behavior, droplet size of 14 ± 1 nm, polydispersity index of 0.151, and zeta potential of -7.7 mV. The preparation remained stable after storage for 60 days. There was a significant CFU. mL^-1 reduction in all tested microorganisms after treatment combining PDT and curcumin microemulsion (30 or 60 μg.mL^-1), and the largest reductions were 5.6175 log10 CFU. mL^-1 in E. coli (10' and 30', both with 30 μg.mL^-1); 5.181 log10 CFU. mL^-1 in MRSA (30' and 30 μg.mL^-1); and 3.497 log10 CFU. mL^-1 in C. albicans (30' and 60 μg.mL^-1).

The formulation containing curcumin in combination with antimicrobial PDT showed promising results in vitro, and this potential formulation awaits further evaluation in clinical trials.