Abstract
Fungal pathologies caused by the genus Candida have increased in recent years due to the involvement of immunosuppressed people and the advance of resistance mechanisms acquired by these microorganisms. Liposomes are nanovesicles with lipid bilayers in which they store compounds. α-Bisabolol is a sesquiterpene with proven biological activities, and in this work it was tested alone in liposomes and in association with Fluconazole in vitro to evaluate the antifungal potential, Fluconazole optimization, and virulence inhibitory effect in vitro. Antifungal assays were performed against standard strains of Candida albicans, Candida tropicalis, and Candida krusei by microdilution to identify the IC50 values and to obtain the cell viability. The Minimum Fungicidal Concentration (MFC) was performed by subculturing on the solid medium, and at their subinhibitory concentration (Matrix Concentration (MC): 16,384 µg/mL) (MC/16), the compounds, both isolated and liposomal, were associated with fluconazole in order to verify the inhibitory effect of this junction. Tests to ascertain changes in morphology were performed in microculture chambers according to MC concentrations. Liposomes were characterized from the vesicle size, polydispersity index, average Zeta potential, and scanning electron microscopy. The IC50 value of the liposomal bisabolol associated with fluconazole (FCZ) was 2.5 µg/mL against all strains tested, revealing a potentiating effect. Liposomal bisabolol was able to potentiate the effect of fluconazole against the CA and CT strains by reducing its concentration and completely inhibiting fungal growth. α-Bisabolol in liposomal form inhibited the morphological transition in all strains tested at a concentration of MC/8. The liposomes were homogeneous, with vesicles with diameters of 203.8 nm for the liposomal bisabolol and a surface charge potential of −34.2 mV, conferring stability to the nanosystem. Through scanning microscopy, the spherical shapes of the vesicles were observed.
Highlights
The high rate of opportunistic fungal infections is of particular concern to patients with some type of immunosuppression
This study aims to demonstrate the in vitro antifungal activity of Bisabolol isolated in liposomal form and associated with fluconazole against strains of C. albicans, C. tropicalis, and C. krusei, and in addition to verify their action on one of the fungal virulence factors, dimorphism
The Minimum Fungicidal Concentration (MFC) value of free bisabolol, liposomal bisabolol, liposome control, and fluconazole corresponded to a concentration ≥ 16,384 μg/mL
Summary
The high rate of opportunistic fungal infections is of particular concern to patients with some type of immunosuppression. The main risk factor for Candida colonization is immunosuppression, the use of broadspectrum antibiotic therapy and steroids, mechanical ventilation (MV), neutropenia, diabetes, and others [2]. Some yeast species possess a virulence mechanism known as dimorphism; C. albicans, for example, is polymorphic, with two distinct morphological characteristic forms: yeast and filamentous. This ability has been associated with tissue infiltration and biofilm formation critically promoting disease [8,9,10]
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