Size-controlled fabrication of silver nanoparticles using the Hedyotis puberula leaf extract: toxicity on mosquito vectors and impact on biological control agents

Abstract

Mosquitoes vector important diseases, including malaria, dengue and Zika virus. The effective control and eradication of the mosquitoes can restrict the spread and severity of these diseases. Here the efficacy of silver nanoparticles (AgNPs) synthesized using the extract of Hedyotis puberula leaves on eggs, larvae and adults of Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus. AgNPs were subjected to different biophysical analyses, including UV-Vis spectrophotometry, FTIR, XRD, AFM, SEM, TEM, EDX and DLS analysis. AgNPs were effective against the larvae of A. stephensi (LC₅₀ 16.58 μg ml⁻¹), A. aegypti (LC₅₀ 18.05 μg ml⁻¹) and C. quinquefasciatus (LC₅₀ 19.52 μg ml⁻¹). AgNPs exerted complete egg mortality at 80 μg ml⁻¹ against A. stephensi and at 100 and 120 μg ml⁻¹ against A. aegypti and C. quinquefasciatus, respectively. LC₅₀ of AgNPs on adults of A. stephensi, A. aegypti and C. quinquefasciatus were 33.11, 36.34 and 39.56 μg ml⁻¹, respectively. Both the H. puberula leaf extract and AgNPs were tested against three mosquito biocontrol agents, Anisops bouvieri, Diplonychus indicus and Gambusia affinis. LC₅₀ ranged from 1048 to 33 552 μg ml⁻¹. Overall, the H. puberula aqueous leaf extract can be employed to fabricate eco-friendly AgNPs with mean size of 6–16 nm, highly effective on A. stephensi, A. aegypti and C. quinquefasciatus.