Terapia fotodinâmica com fenotiazínicos associados ao dodecil sulfato de sódio em biofilmes de candida albicans nas diferentes fases de crescimento

Abstract

The ability to organize into biofilms is essential for host infection and virulence of C. albicans. The organization in biofilms confers greater resistance to antifungals, so that therapies to combat biofilms are essential in the control of infections in the health area. Antimicrobial photodynamic therapy (aPDT) is based on the use of a photosensitizer (PS) activated by light with adequate parameters, leading to the death of target cells. Methylene blue (AM) is a SF that has been extensively studied in aPDT, but there are compounds with a similar structure, all belonging to the phenothiazine class, whose effects are not yet known, including Azure A (AA), Azure B (AB) and methylene dimethyl blue (DMAM). It is known that these FSs present aggregation that can be minimized in some media/solvents, in order to potentiate the effects of aPDT. Thus, the objective of this work is to evaluate the effect of aPDT with phenothiazine compounds on the effectiveness of aPDT in biofilms, in their different stages of formation. After cultivation, a suspension of C. albicans was prepared, followed by plating (5.0×107 cells/mL). One set of experiments was carried out with the treatment of suspensions and evaluation of their ability to form biofilms, while other sets were carried out on already established biofilms. For the formation of biofilms, the prepared suspension was incubated in the presence of Sabouraud broth medium. The samples were exposed to FS solutions (in water or in the presence of 0.25% sodium dodecyl sulfate (SDS)) and kept for 5 minutes in the dark. Irradiation was performed and after the treatments, the solutions were removed, the biofilms were washed with PBS to perform the colony forming unit count assay (CFU/mL). LED parameters were 660nm, 37.3mW/cm2 for 27 minutes, 60.4J/cm2. In the evaluation of the effect of aPDT before the biofilm formation phase (before adherence), it was verified that aPDT with all the PS studied prevents the formation of the biofilm. aPDT with any of the FS used was unable to reduce the amount of CFU/mL both in mature biofilms (24h) and in biofilms in the dispersion phase (48h). When applying two irradiations to biofilms in dispersion, it was verified that aPDT with AM, AA and DMAM were able to inactivate the amount of CFU/mL, which was not observed in mature biofilms. In view of this, we conclude that the different stages of biofilm growth respond to aPDT differently, with the greatest inhibitory effect being in the adhesion stage. Mature and dispersing biofilms are less susceptible to aPDT, however, the use of two sequential sessions is adequate to inactivate the C. albicans biofilm.