Silver Nanoparticles Produced by Alternaria tenuissima: Antimicrobial and Anticancer Activity
TL;DR
It is demonstrated that At-AgNPs possess measurable in vitro antimicrobial activity and preferential cytotoxicity toward cancer cells, supporting further investigation of this biologically synthesized nanomaterial in antimicrobial and anticancer research.
Abstract
This study aimed to biosynthesize silver nanoparticles using the cell-free filtrate of the endophytic fungus Alternaria tenuissima and to evaluate their physicochemical properties, antimicrobial activity, and preferential in vitro cytotoxicity against cancer cell lines. The resulting A. tenuissima–mediated silver nanoparticles (At-AgNPs) were characterized using ultraviolet–visible spectroscopy, zeta-potential analysis, X-ray diffraction, transmission electron microscopy, and Fourier-transform infrared spectroscopy. Antimicrobial activity was assessed using agar well diffusion, minimum inhibitory concentration, minimum bactericidal concentration, and minimum fungicidal concentration assays. Cytotoxicity was evaluated using the MTT cell viability assay in MCF-7 breast cancer cells, HepG2 hepatocellular carcinoma cells, A549 lung carcinoma cells, and WI-38 normal fibroblasts. At-AgNP formation was confirmed by a surface plasmon resonance peak at 412 nm. Zeta-potential analysis showed negatively charged bimodal distributions at −32.7 and −25.7 mV, while X-ray diffraction confirmed a face-centered cubic crystalline structure. Transmission electron microscopy revealed predominantly spherical to quasi-spherical nanoparticles ranging from approximately 2 to 16 nm, with the highest frequency observed at 8–10 nm. At-AgNPs inhibited all tested bacterial strains and Candida albicans, with minimum inhibitory concentration values ranging from 7.80 to 31.25 µg/mL, but showed no measurable activity against Aspergillus niger. In the cytotoxicity assay, At-AgNPs reduced cancer cell viability in a concentration-dependent manner, with half-maximal inhibitory concentration values of 121.44 µg/mL for MCF-7, 112.63 µg/mL for HepG2, and 110.16 µg/mL for A549 cells, compared with 226.32 µg/mL for WI-38 normal fibroblasts. These findings demonstrate that At-AgNPs possess measurable in vitro antimicrobial activity and preferential cytotoxicity toward cancer cells, supporting further investigation of this biologically synthesized nanomaterial in antimicrobial and anticancer research.