Bacillus velezensis-synthesized silver nanoparticles and its efficacy in controlling the Aedes aegypti

Dengue fever and dengue haemorrhagic fever are diseases that do not have any potential medications. The severity of these diseases is fatal and thus poses a severe threat to mankind. Aedes aegypti is the vector that carries and spreads the dengue virus. Therefore, controlling the development and population of mosquitoes is crucial. Many insecticides and other strategies of control have not become successful in their purpose. Therefore, establishing potential compounds that are environmentally safe and productive in inhibiting the growth of mosquitoes is still to be acquired. Bacillus velezensis (MW219533) was utilized in the synthesis of silver nanoparticles with silver nitrate as the metal ion source. The silver nanoparticles were characterized and confirmed using UV–visible spectrometry that indicated a peak at 421 nm. Further analytical measurements such as X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and energy dispersive X-ray analysis confirmed the presence of crystalline, cylindrical-shaped silver nanoparticles of size 56–59 nm. The LC₅₀ was found to be 581.39, 616.37, 760.93, 801.94 and 867.66 µg l⁻¹ when tested against the five developmental stages of Aedes aegypti, such as first instar, second instar, third instar, fourth instar stages of larvae and pupae, respectively. The predatory efficacy of Poecilia reticulata was calculated with exposure to silver nanoparticles. Our study aims on developing an environmentally safe and economical approach to reduce the development of mosquitoes in the environment. The work signifies the biological method towards controlling the larvae and pupae stages of A. aegypti as well as to mark its safety at the aquatic level of the life cycle that leaves no traces of pollution on the environment.