Synthesis of PEG 400-Stabilized Silver Nanoparticles Using Nigella sativa Seed Extract: Characterization and Antifungal Activity

Abstract The increasing incidence of antifungal resistance, along with growing environmental concerns regarding the extensive use of chemical fungicides, underscores the urgent need for sustainable and eco-friendly alternatives. In this context, the present study explores a green synthesis approach for the development of silver nanoparticles (AgNPs) using the aqueous extract of Nigella sativa (commonly known as black seed) as a reducing and capping agent, in combination with polyethylene glycol 400 (PEG 400) as a stabilizer. The synthesized AgNPs were characterized using ultraviolet-visible (UV-Vis) spectroscopy and scanning electron microscopy (SEM), confirming the formation of spherical, crystalline nanoparticles with sizes ranging between 29 and 35 nm. A distinct surface plasmon resonance (SPR) peak was observed at 430 nm, indicating the successful synthesis of AgNPs. PEG 400 played a crucial role in enhancing the colloidal stability of the nanoparticles, while phytochemicals present in the N. sativa extract facilitated the bioreduction and stabilization process. The antifungal efficacy of the AgNPs was assessed through the broth microdilution method against several plant-pathogenic fungi, including Trichoderma parareesei, Colletotrichum spp., and Chaetomium globosum. The minimum inhibitory concentrations (MICs) demonstrated strong antifungal activity, highlighting the potential of these biogenic AgNPs as effective agents against phytopathogens. The eco-friendly synthesis method employed in this study not only minimizes the use of hazardous chemicals but also contributes to the development of sustainable nanomaterials for agricultural and biomedical applications. Overall, the findings suggest that Nigella sativa-mediated AgNPs, stabilized with PEG 400, offer a promising alternative to conventional fungicides, aligning with the goals of green chemistry and integrated pest management.