Chitosan nanoparticles loaded with ribavirin, carboplatin, and thyme oil downregulate SNQ2, ERG11, CDR1, and MDR1 in Candida strains.

This study examined the effects of chitosan nanoparticles (CS-NPs) loaded with ribavirin (CS-R-NPs), carboplatin (CS-C-NPs), and Thymus vulgaris essential oil (CS-TV-NPs) on gene expression in Candida glabrata and Candida tropicalis. C. glabrata and C. tropicalis strains were obtained from Tarbiat Modares University. CS-NPs were synthesized via the ionic gelation method and characterized through dynamic light scattering, electrophoretic light scattering and transmission electron microscopy. Cytotoxicity was assessed via the MTT assay in fibroblasts. The minimum inhibitory concentrations (MICs) of the nanoparticle-encapsulated formulations were determined via the microdilution method per the CLSI-M27-A3/S4 guidelines. The gene expression of SNQ2 and ERG11 in C. glabrata and that of CDR1 and MDR1 in C. tropicalis was quantified via qRT‒PCR. CS-R-NPs, CS-C-NPs and CS-TV-NPs demonstrated high encapsulation efficiencies (81-91%), hydrodynamic diameters of approximately 286-298 nm, and positive zeta potentials (+ 33 to + 34 mV), with a spherical morphology and minimal aggregation. In vitro drug release extended over 64 h, with CS-TV-NPs achieving the highest cumulative release (60%). Cytotoxicity assays indicated that the CS-TV-NPs presented the highest IC50 (20.31 µg/ml). Compared with free drugs, encapsulated formulations significantly lowered the MIC values against C. glabrata and C. tropicalis, enhancing antifungal efficacy. qRT‒PCR confirmed notable downregulation of SNQ2 and ERG11 in C. glabrata and of CDR1 and MDR1 in C. tropicalis, with the most pronounced effects observed in the CS-NP-treated groups. CS-NPs significantly enhanced antifungal efficacy by reducing MIC values and downregulating resistance genes, highlighting their potential as effective drug delivery systems against Candida infections.