Avaliação da influência da massa molar na atividade antifúnfica da quitosana frente a células planctônicas e biofilmes de diferentes espécies fúngicas

Abstract

Currently the number of cases of systemic and opportunistic mycoses has been frequently reported and the use of classical antifungals has been shown to have reduced action spectrum and toxic effects on human cells. The present study evaluated and characterized chitosan action with different molecular weights and deacetylation degrees against planktonic cells of yeast (n = 18), dimorphic (n = 6) and filamentous (n = 6) fungi, of the genera Candida spp., Sporothrix brasiliensise dermatophytes, respectively. The investigation followed the biofilms sensitivity of Candida spp. and Sporothirx brasiliensis in the adhesion and mature phases on biofilms against high, medium and low molecular weight chitosan. The adhesion and mature phases of biofilms formed were evaluated for biomass and metabolic activity. The average molecular weights of the high, medium and low molecular weight chitosan were determined by viscosimetry and the values obtained were 75kDa, 140kDa and 247kDa, respectively. The degrees of deacetylation of the high, medium and low molecular weight samples were determined by potentiometric titration and the values found were 79.03%, 84.18% and 81.8%, respectively. The effect of all chitosans were more effective against Candida parapsilosis, followed by Candida tropicalis and Candida albicans with MIC (minimum inhibitory concentration) values of 4-256 μg / mL, 16-512 μg / mL 256-512 μg / mL, respectively. The results indicated that high molecular weight chitosan (247 kDa) was more effective in inhibiting the growth of Candida species, whereas for Sporothrix brasiliensis the lower the molecular weight the greater the antifungal activity. It was not possible to determine the Minimum Inhibitory Concentration for the filamentous fungal strains in the range tested. The biofilm samples were able to reduce the metabolic activity and biomass of the mature biofilms of Candida spp. in 85,81% and 90%, and for Sporothrix brasiliensis in up to 81,88% and 79,56%, respectively. The data from confocal microscopy and scanning electron microscopy for low molecular weight chitosan showed a visual reduction in the number of viable cells and damage to the fungal cells of Candida tropicalis. The results indicate that the chitosan under study is a compound with potential properties for different antifungal applications (topical or medical devices).