Biosynthesis of silver nanoparticles using soil actinobacterium Streptomyces anthocyanicus and investigation of their larvicidal potentials against Culex quinquefasciatus Aedes aegypti, and Anopheles stephensi

Abstract

Mosquitoes represent a considerable risk to human health due to their role in transmitting various pathogens responsible for diseases like chikungunya, malaria, dengue, and Japanese encephalitis. There is an immediate necessity to explore innovative biological strategies to combat mosquito-borne illnesses. One promising avenue in current research is the development of bioinsecticides utilizing advanced nanotechnology. Therefore, this study aimed to synthesize silver nanoparticles from the actinobacterial strain Streptomyces anthocyanicus (OR186732), isolated from the Western Ghats in Tamil Nadu, India. The AgNPs were synthesized and then characterized using UV–visible spectroscopy, identifying a prominent absorption peak at 424 nm. The identification of different functional groups within the AgNPs was confirmed through FTIR. The produced AgNPs were shown to be crystalline by XRD analysis. The nanoparticles were characterized using FESEM, HRTEM, and EDX to analyze their morphology, size, and elemental composition. The stability was assessed through Zeta potential measurements, which were measured at −0.2 mV. The synthesized AgNPs showed strong larvicidal effects against Culex quinquefasciatus (LC₅₀ = 2.924 ppm), Aedes aegypti (LC₅₀ = 3.245 ppm), and Anopheles stephensi (LC₅₀ = 3.767 ppm). Furthermore, the AgNPs were observed to significantly increase the levels of antioxidant enzymes such as SOD and GPx at high concentrations. In contrast, levels of detoxifying enzymes such as AChE and GST levels were reduced. Histological analysis of mosquito larvae treated with AgNPs revealed significant damage to the midgut tissues. The research suggests that AgNPs synthesized by Actinobacteria could be an environmentally friendly option for biological mosquito control.