BACKGROUND: The green synthesis of zinc oxide nanoparticles (ZnO NPs) using biological systems offers an eco-friendly alternative to conventional chemical methods. Fungal endophytes, which produce diverse bioactive metabolites, represent promising resources for nanomaterial synthesis. This study investigates the use of an endophytic Aspergillus niger strain isolated from the medicinal plant Celastrus paniculatus for the mycogenic synthesis of ZnO NPs and evaluates their multifunctional bioactivity. METHODS: ZnO NPs were synthesized via a sol-gel method using an aqueous extract of A. niger. Comprehensive characterization was performed using XRD, FTIR, SEM, TEM, UV-Vis, and PL spectroscopy. Biological activities were assessed through DPPH antioxidant assay, antimicrobial testing (disc diffusion and MIC against bacterial pathogens), antifungal assay against Fusarium oxysporum, and plant growth promotion studies on Oryza sativa L. Basmati seedlings in a hydroponic system. RESULTS: Characterization confirmed the formation of pure, hexagonal wurtzite ZnO NPs with an average crystallite size of 27.3 ± 3.1 nm and a band gap of 3.26 eV. FTIR indicated the presence of fungal-derived biomolecules on the NP surface. The NPs exhibited antioxidant activity (IC₅₀ = 42.7 ± 1.8 µg/mL), antibacterial effects (with MIC values of 0.41-3.33 µg/mL against tested strains), and antifungal activity (47.7 ± 1.0% inhibition of F. oxysporum at 200 µg/mL). In hydroponic studies, treatment with 2 µM ZnO NPs was associated with modest increases in rice seedling fresh weight (p = 0.023) and photosynthetic efficiency (Fv/Fm, p = 0.017) compared to controls. CONCLUSION: This work demonstrates the synthesis of ZnO NPs using an endophytic A. niger isolate from C. paniculatus. The synthesized NPs exhibit multiple bioactivities in vitro, suggesting potential for further investigation in agricultural and antimicrobial contexts. However, substantial additional research including cytotoxicity assessment, environmental fate studies, and field trials will be necessary before practical applications can be considered.
Dwivedi et al. (Sun,) studied this question.