Fusarium oxysporum Silver Nanoparticles; their Characterization and Larvicidal Activity against Aedes Mosquitoes

Fusarium oxysporum is an entomopathogenic fungus, and it has anti-biological activity against larvae of mosquitoes. Aedes mosquitoes are responsible for transmitting different diseases in humans. The use of chemical insecticides against mosquitoes is not eco-friendly option and results in the development of insecticidal resistance in mosquitoes. We investigated a biological control activity against these mosquitoes. In the present study, we cultured a local isolate of F. oxysporum from soil samples collected from Lahore, Pakistan and were initially identified based on its morphology and then confirmed through PCR. A product of 339 bp was amplified from the ITS (Internal Transcribed Spacer) gene of the fungus and sequenced afterwards. The sequence was in clad with Fusarium, which was isolated from a mosquito's body in the phylogenetic analysis. Local F. oxysporum was cultured and silver NPs (nanoparticles) were prepared. UV-Vis analysis depicted a broad peak at 420 nm wavelength and a narrow height at 310 nm. X-ray diffraction patterns of NPs indicated the existence of sharp diffraction peaks at 2θ angles of 32.19°, 45.55° and 64.27° that can be indexed to the (101), (200) and (220) facets of silver, which agree with the values reported for fcc lattice of silver NPs in International Center for Diffraction Data (ICDD). The SEM (scanning electron microscope) micrograph showed well-defined spherical NPs, which were smooth, isotropic, poly-dispersed, and ranging from 10 nm to 200 nm. The Zeta potential (ZP) measurements and poly-disparity index of 0.16 by DLS revealed a low variability of particle size and exhibited good physiochemical stability of biosynthesized AgNPs. In the Fourier-transform infrared spectroscopy (FTIR) spectrum of biosynthesized AgNPs, strong bands were analyzed at 3280 cm-1 and 1635 cm-1. F. oxysporum NPs enhanced the anti-biological activity by killing Aedes larvae 7 h earlier than F. oxysporum without NPs. Biological control using entomopathogenic fungi can be the best alternative of the chemical method to control the mosquito population. © 2021 Friends Science Publishers