Avaliação dosimétrica da terapia fotodinâmica antimicrobiana em candida albicans com azul de metileno veiculado em água e associado ao dodecilsulfato de sódio

Abstract

C. albicans is responsible for nearly 78% of fungal infections in hospitals. Antifungals are the standard treatment used in these complications, however, prolonged use is necessary, which may lead to the selection of resistant strains, in addition to side effects, such as liver toxicity. Photodynamic Therapy (PDT) is a therapeutic option that has the advantage of not promoting resistance, as it is based on the use of a photosensitizer as a microbial agent that acts by activation with light in the presence of oxygen, acting through the action of reactive species. of oxygen (ROS). Methylene Blue (MA) is widely investigated as an antimicrobial agent for PDT, but not always effective. Depending on the selected conditions/protocols, AM can aggregate, affecting its photochemical/photobiological action, and, making the treatment unfeasible. Our research group showed that the control of AM aggregation through association with sodium dodecyl sulfate (SDS) potentiates the action of PDT. However, in addition, dosimetry also plays an important role in the results. Thus, the objective of this study was to compare PDT dosimetry in C. albicans using AM transmitted in SDS. Tests were carried out to quantify the Colony Forming Units (CFU/mL) using MA in different media, and different dosimetric parameters, namely: Control (water), SDS (0.25%), AM (20 mg/mL) and AM/SDS; Irradiances of 3.7; 11.2; 18.6 and 26.1 mW/cm2 varying the irradiation times to reach Radiant Exposures of (4.4; 17.8; 26.7 and 44 J/cm²). The results showed that the antimicrobial effect of the PDT of the AM associated with the SDS is always more effective than that of the AM conveyed in water. Furthermore, for the same I, there is only an increase in the antimicrobial effect due to the increase in RE in the highest I (26.1 mW/cm2). When comparing the effect of different I on the same ER parameter, it was possible to observe that, although in the smallest ER, it was not modified between the antimicrobial effect and the I, in all other ER evaluations that existed. It is concluded that regardless of the dosimetry used, PDT with AM/SDS has a greater antimicrobial action than AM in water. The use of RE above 18J/cm² and I above 26Mw/CM² is suggested, since in these cases, the increase in dosimetry is correlated with a greater antimicrobial effect.