Green synthesis, physio-chemical characterization and anti-candidal function of a biocompatible chitosan gold nanocomposite as a promising antifungal therapeutic agent

Abstract

A chitosan gold nanocomposite (CAuNC) was green synthesized using chitosan and gold(III) chloride trihydrate without using a reducing agent. The formation and crystalline nature of the gold nanoparticles (AuNPs) in CAuNC were confirmed by UV-visible spectrum and XRD analysis. The average particle size and zeta potential of CAuNC were 308 nm and +37.45 mV, respectively. The CAuNC contains 13.56% (w/w) of Au, and released 8.56 ppb Au ions into potato dextrose broth (PDB). The CAuNC was evaluated for its antifungal activities using Candida albicans as a model organism, and the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) were recorded as 50 and 75 μg mL⁻¹, respectively. Propidium iodide (PI) uptake and FE-SEM analysis results suggest that CAuNC enhances the permeability and structural changes of C. albicans cells in a concentration dependent manner. Exposure of CAuNC increased the mitochondrial membrane potential, and dysfunctions of mitochondria could induce the reactive oxygen species (ROS) level and increase the oxidative stress. Moreover, the expression of some C. albicans proteins has decreased after CAuNC treatment. The CAuNC was nontoxic to mammalian A549 and HEK293T cells up to 100 μg mL⁻¹ suggesting that it can be applied to in vivo tests. C. albicans infected zebrafish recovered after CAuNC therapy as a topical treatment, suggesting that CAuNC is a potential antifungal agent against candidiasis. This report illustrates the eco-friendly approach of synthesizing biologically active CAuNC as a potent antifungal agent against C. albicans.