Mycosynthesized silver nanoparticles using individual and combined entomopathogenic fungal systems: characterization, larvicidal, and antimicrobial activities.

Mosquito-borne diseases remain major public health challenges worldwide, while the extensive use of synthetic insecticides has contributed to environmental problems and insecticide resistance in mosquito populations. The present study involves an eco-friendly approach to controlling mosquito larvae and assessing antimicrobial activity using three different biosynthesized silver nanoparticles (AgNPs) derived from Trichoderma asperellum (Ta AgNPs), Metarhizium anisopliae (Ma AgNPs), and their combination (Ta Ma AgNPs). The synthesized nanoparticles were characterized using UV-Visible spectroscopy, ATR-FTIR, Cryo FE-SEM, Cryo-TEM, DLS, and zeta potential analysis. TEM results revealed spherical nanoparticles with average sizes of 9.17 nm (Ta AgNPs), 11.25 nm (Ma AgNPs), and 12.54 nm (Ta Ma AgNPs). Zeta potential values ranged from - 23 to - 26.9 mV. Larvicidal bioassays were tested against the larvae of Aedes aegypti using each synthesized AgNPs at concentrations of 25, 50, 100, and 150 µg/mL. The results demonstrated high larvicidal efficacy for all synthesized AgNPs treatments. The lethal concentration (LC 50) achieved by Ta AgNPs, Ma AgNPs, and Ta Ma AgNPs at 24 h was 58.61, 63.39, and 52.32 µg/mL, respectively, and at 48 h was 43.60, 51.46, and 39.50 µg/mL, respectively. Larval mortality following treatment with Ta AgNPs, Ma AgNPs, and Ta Ma AgNPs was higher than that observed with fungal extracts alone (82.50%, 80.44%, and 87.69%, respectively). Furthermore, the three AgNPs were tested for antimicrobial activity using the zone of inhibition method against both Gram-positive and Gram-negative bacteria, including Escherichia coli, Bacillus megaterium, Pseudomonas aeruginosa, and Staphylococcus aureus. Compared with chloramphenicol treatment, all three AgNPs showed inhibitory effects against P. aeruginosa and B. megaterium, particularly at the highest concentration of 150 μg/mL. Overall, this study highlights the potential of the three synthesized AgNPs, especially the combined Ta Ma AgNPs, as an alternative strategy for mosquito-borne disease control and antimicrobial applications.