Biosynthesis, Characterization, and Antifungal Activity of the Silver Nanoparticles Against Pathogenic Candida species

Alcoholic extract of tulsi leaves was used as a reducing and stabilizing agent for the synthesis of silver nanoparticles (AgNPs). The use of plant extract for the synthesis of nanoparticles is cost-effective, single step, and an ecofriendly process. The biosynthesized AgNPs were characterized using UV-Vis, transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) analysis. The AgNPs formed show surface plasmon resonance at 430 nm. They have a smooth surface with an average diameter of 2-7 nm. Their crystalline nature was confirmed by the XRD. The antifungal activity of the AgNPs was evaluated for opportunistic human fungal pathogens Candida albicans, Candida glabrata, and Candida tropicalis. The antifungal effect was determined by minimum inhibitory concentration (MIC), minimum fungicidal concentration (MFC), and disk diffusion assay. Further, to assess the pathogenicity, proteinase and phospholipase assays were performed. TEM analysis of treated Candida cells reveals that the AgNPs may be exerting antifungal activity by disrupting the cell membrane structure and integrity. Cytotoxicity of AgNPs was checked by performing hemolytic assay against human erythrocytes. At MIC values, AgNPs caused only 5.6 % lysis in RBCs which was very low in comparison to conventional antifungal agents. Hence, biosynthesized AgNPs using plant extracts have immense antifungal potential and can be used in the management of fungal infections. Further studies have to be done to understand their mode of action.