Potential larvicidal activity of silver nanohybrids synthesized using leaf extracts of Cleistanthus collinus (Roxb.) Benth. ex Hook.f. and Strychnos nux-vomica L. nux-vomica against dengue, Chikungunya and Zika vectors

Abstract This study focused on green engineering of stable metallic silver nanohybrids (AgNPs) using Cleistanthus collinus (Cc) and Strychnos nux-vomica (Sn) plant leaf extracts via microwave irradiation and its bioinsecticidal activity against the mosquito vectors and antimicrobial efficacy against clinically isolated human pathogens. Engineered silver nanohybrids (CcAgNPs and SnAgNPs) were characterized by UV-vis spectroscopy, Fourier Transform Infra-red spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD), Field Emission Scanning Electron Microscopy (FESEM) and Energy-dispersive X-ray spectroscopy (EDX) analysis. FTIR results showed the role of alcohols, amines, alkanes, and amides in the bioreduction, capping and stabilization of synthesized silver nanoparticles. The XRD analysis confirmed the crystalline structure of the synthesized silver nanohybrids. FESEM results displayed the shape as well as size of the engineered CcAgNPs and SnAgNPs. Interestingly, the synthesized CcAgNPs was found to be triangular and pentagonal shape with 66.27–75.09 nm size and the synthesized SnAgNPs showed irregular, spherical and round shape with 54.45–60.84 nm size. The existence of silver ion signals on engineered nanohybrids at 2.8 to 4 KeV was established by EDX analysis. Further, both C. collinus and S. nux-vomica leaf extracts and engineered CcAgNPs and SnAgNPs showed highest larvicidal activity against Anopheles stephensi and Aedes aegypti fourth instar larvae. The maximum mortality rate (100%) for CcAgNPs was observed at 20 mg/l and 25 mg/l for A. aegypti and A. stephensi vectors respectively, while highest percent of mortality for SnAgNPs was noticed in both A. aegypti and A. stephensi at 25 mg/l. The LC 50 dose for CcAgNPs towards A. stephensi and A. aegypti mosquito vectors noticed were 11.05 and 11.38 mg/l, respectively, whereas the LC 50 data for SnAgNPs obtained was 8.82 and 7.75 mg/l for A. stephensi and A. aegypti , respectively. The larvicidal activity was positively correlated with the engineered AgNPs exposure. Both CcAgNPs and SnAgNPs found to be effective antimicrobial agent against six human microbial pathogens and these nanohybrids may be considered as effective antibacterial nanodrug. The results strongly suggest that C. collinus and S. nux-vomica plant extracts derived silver nanohybrids can be applied as a natural biolarvicidal compound to vector-control strategy as non-toxic and eco-friendly approach to prohibit Zika, Chikungunya and dengue fever in the future.