Biogenic Synthesis and Characterization of Silver Nanoparticles: Evaluation of Their Larvicidal, Antibacterial, and Cytotoxic Activities.

To explore the larvicidal activity of the silver nanoparticles (AgNPs) synthesized using the ethanolic Catharanthus roseus flower extract (CRE) against the larvae of Aedes aegypti ( A. aegypti ), AgNPs were synthesized by an eco-friendly method and characterized by Ultraviolet-Visible (UV-Vis) spectroscopy, Fourier Transform Infrared spectroscopy (FTIR), X-Ray Diffraction (XRD), Particle Size Analysis, Transmission Electron Microscopy (TEM), and Energy-Dispersive X-Ray spectrometry (EDX) analysis. The resultant AgNPs showed a spherically well-defined, highly stable, and monodispersed shape with an average particle size ranging from 15 to 25 nm. The absorbance of the AgNPs was measured by using a UV-Vis spectrophotometer at a wavelength of 416 nm. The presence and binding of the phenolic functional group with the AgNPs were confirmed using FTIR analysis. Particle size analysis revealed an average particle diameter of 90 nm with 80 % distribution. XRD analysis revealed the highly crystalline nature of the CRE-AgNPs. The LC 50 and LC 90 values of CRE-AgNPs and the extract were calculated. The mortality percentage of the extract and synthesized CRE-AgNPs was observed after 24 h. The maximum larvicidal activity with 100 % mortality of A. aegypti was observed in AgNPs synthesized using ethanolic CRE. The LC 50 and LC 90 values are 8.963 and 20.515 ppm for CRE-AgNPs against A. aegypti larvae, respectively. The CRE-AgNPs revealed superior antibacterial activity against human pathogenic bacteria; the zone of inhibition (ZOI) was measured for all of the pathogens, and the results revealed that different concentrations of CRE-AgNPs showed a remarkable ZOI of about (a) 10-14 mm for Salmonella typhimurium , (b) 6-11 mm for Bacillus subtilis , (c) 11-14 mm for Enterococcus faecalis , and (d) 9-10 mm for Shigella boydii . The maximum ZOI was observed in E. faecalis . Impeccably, the cytotoxicity of CRE-AgNPs at 250 μg/mL is 82% against the HaCaT cell lines. The synthesized CRE-AgNPs showed maximum effectiveness of paradoxical activity on mosquito larvae.