Eco-friendly biosynthesis of silver nanoparticles using marine-derived Fusarium exquisite: optimization, characterization, and evaluation of antimicrobial, antioxidant, and cytotoxic activities

Fungi serve as efficient biocatalysts for the eco-friendly synthesis of metal nanoparticles, yielding stable and bioactive nanomaterials. In this study, silver nanoparticles were synthesized (AgNPs) using the marine-derived fungus Fusarium equiseti and characterized them with various analytical methods. UV-Vis spectroscopy detected a surface plasmon resonance peak at 420 nm, confirming AgNP formation, while X-ray diffraction (XRD) verified their crystalline structure. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed spherical nanoparticles averaging 50 nm. FTIR analysis confirmed that fungal metabolites cap and stabilize the AgNPs. We optimized extracellular biosynthesis at 30°C, pH 8, and 2 mM AgNO₃ over 72 h. The marine-adapted F. equiseti was selected for its robust metabolic capacity and enzyme secretion, enhancing nanoparticle stability and bioactivity. Biological assessments showed that these AgNPs outperformed AgNO₃ in antimicrobial activity, with minimum inhibitory concentrations (MICs) of 6.5 µg/mL against Staphylococcus aureus and 7.5 µg/mL against Escherichia coli, plus antifungal effects on Candida albicans and Fusarium solani. They also displayed strong antioxidant activity (IC₅₀ = 56.98 µg/mL) and cytotoxicity against MCF-7 breast cancer cells (IC₅₀ = 24.38 µg/mL). These enhanced effects likely stem from fungal metabolites acting as natural capping agents, minimizing aggregation and boosting bioavailability and biological interactions. Molecular docking studies reinforced these results, revealing strong binding of AgNPs to microbial cell wall proteins, the human apoptotic regulator Bcl-2 (an anticancer target), and the antioxidant enzyme peroxiredoxin-5 (PRDX5). This green synthesis method provides a sustainable, non-toxic alternative to conventional chemical approaches, avoiding hazardous reagents while delivering stable, multifunctional AgNPs. Future in vivo validation and biocompatibility studies are planned to explore the clinical and pharmaceutical potential of F. equiseti-derived AgNPs.