Avaliação da eficácia de um enxaguante bucal à base de azul de metileno na inativação de Candida albicans por terapia fotodinâmica

Abstract

Candidiasis is an opportunistic infection caused by Candida albicans. Considering the antifungal agents treatments disadvantages, the Photodynamic Therapy (PDT) based on the concomitant use of a photosensitizer and a light agent, in the oxygen presence, showed to be an interesting alternative. Methylene blue (MB) has been widely used in antimicrobial PDT (aPDT), but due to the lack of protocol standardization, it is not always possible to verify greater efficiency than traditional treatments. The MB can have its activity modulated once its mechanism of action is defined by its aggregation state. In this sense, the identification of the relationships between aggregation, mechanism of action and effectiveness against microorganisms, as well as the establishment of means and formulations that may favor the most effective mechanism, are essential. This study evaluated the aPDT efficacy with a mouthwash formulation with MB in biofilms of in vitro C albicans, with the objective of relating the aggregation state, photochemical mechanism and its effectiveness. In the planktonic culture study, Candida albicans was used to define which parameters would be adopted in the same species biofilm treatment incubation time in the dark, irradiation time and MB concentration. The highest irradiation time (30 minutes) and the lowest MB concentrations (0.001 and 0.002%) were the most efficient parameters. In a second stage, the biofilm was treated in six experimental groups: Physiological solution, no MB mouthwash, MB 0.002 and 0.005% in saline, MB 0.002% and 0.005% in mouthwash. The experimental group MB 0.005% in mouthwash presented lower viability after treatment which makes us to infer that MB in monomers shows greater effectiveness in aPDT and the photochemical mechanism via singlet oxygen is more effective. This research indicates that the formulations development for MB aggregation control, may result in more efficient clinical protocols.