Characterization and Antifungal Efficacy of Biogenic Silver Nanoparticles and Silver–Chitosan Nanocomposites

The present study aimed for a comparative study of green protocol for the biogenic synthesis of silver nanoparticles (AgNPs) and silver-chitosan nanocomposites (Ag-CS-NCs), characterization, and comparative evaluation of antifungal and anti-aflatoxin B1 activity potentials of both nanoparticles (NPs). The cell-free culture filtrate (CFF) of Aspergillus terreus (KC462061) was utilized to biogenic synthesis AgNPs and Ag-CS-NCs. The physicochemical characterization was done by ultraviolet-visible spectroscopy (UV-Vis), transmission electron microscopy (TEM), high- resolution scanning electron microscopy (HR-SEM), Energy Dispersive Spectroscopy (EDS), Fourier transform-infrared spectroscopy (FTIR). The UV-Vis spectroscopy of the prepared AgNPs and Ag-CS-NCs showed variation in the appearance of specific significant peaks, 425 nm for AgNPs and 275, 425 nm for Ag-CS-NCs. The microscopic analysis was done by TEM and the results revealed that both NPs were spherical in shape, with average size ranged from 10 to 60 nm. The HR-SEM micrographs revealed a rough surface with uneven surface topology of the AgNPs, while Ag-CS-NCs were thin, straight and smooth pipe. FTIR spectroscopy indicated that the functional groups (proteins and secondary metabolites) present in the CFF might be responsible for the bioreduction of Ag⁺ (ions) to produce stabilized protein-capped AgNPs. This study presents the antifungal activity and anti-aflatoxin B1 of AgNPs and Ag-CS-NCs against an aflatoxigenic isolates of A. flavus. Our in vitro results showed notable antifungal activity and potency in thwarting aflatoxin B1 (AB1) production. In addition, SEM imaging was applied to observe the changes in fungal hyphal morphological features after the interactions with AgNPs and Ag-CS-NCs.