Abstract
(1) Background: Infections by Candida species represent a serious threat to the health of immunocompromised individuals. Evidence has indicated that nerolidol has significant antifungal properties. Nonetheless, its use is restricted due to a low water solubility and high photosensitivity. The incorporation into liposomes may represent an efficient alternative to improve the physicochemical and biopharmaceutical properties of this compound. The present study aimed to characterize the antifungal properties of liposomal nerolidol, alone or in combination with fluconazole. Of note, this is the first study reporting the antifungal activity of liposomal nerolidol and its potentiating effect in association with fluconazole. (2) Methods: The Inhibitory Concentration 50%-IC50 and minimum fungicide concentrations (MFC) of the substances against Candida albicans (CA), Candida tropicalis (CT), and Candida krusei (CK) were established by subculture in a solid medium. To evaluate the antifungal-enhancing effect, the MFC of fluconazole was determined in the presence or absence of subinhibitory concentrations of nerolidol (free or liposomal). The analysis of fungal dimorphism was performed through optical microscopy and the characterization of liposomes was carried out considering the vesicular size, polydispersion index, and zeta medium potential, in addition to a scanning electron microscopy analysis. (3) Results: The physicochemical characterization revealed that liposomes were obtained as homogenous populations of spherical vesicles. The data obtained in the present study indicate that nerolidol acts as an antifungal agent against Candida albicans and Candida tropicalis, in addition to potentiating (only in the liposomal form) the effect of fluconazole. However, the compound had little inhibitory effect on fungal dimorphism. (4) Conclusions: The incorporation of nerolidol into liposomes improved its antifungal-modulating properties.
Highlights
Infections by Candida species represent a serious threat to the health of immunocompromised individuals, including transplant patients, cancer patients, and those undergoing immunosuppressive drug therapy [1,2]
The growth curves of different Candida strains in the presence of nerolidol demonstrated that this compound presented a weak antifungal activity against all strains of Candida evaluated by this study, in contrast to the pharmacological control fluconazole (Figure 1)
While nerolidol demonstrated the strongest activity against Candida albicans, the incorporation of this compound into liposomes was found to present an enhanced antifungal activity only against Candida tropicalis, indicating a selective improvement of its antifungal action with regard to the type of strain
Summary
Infections by Candida species represent a serious threat to the health of immunocompromised individuals, including transplant patients, cancer patients, and those undergoing immunosuppressive drug therapy [1,2]. These microorganisms are the most frequent causative agents of invasive fungal infections, being commonly isolated from intensive care unit (ICU) patients [3]. The prolonged use (above 4 weeks) of these drugs has been associated with high treatment costs, the development of resistance, and significant toxicity [8], justifying the search for novel therapeutic agents to treat invasive fungal infections in immunocompromised patients. Since dimorphism has a significant impact on the pathogenesis of Candida species, the investigation of compounds capable of inhibiting this phenomenon may represent a promising strategy for the development of new antifungal drugs [9,10,11]
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