Optimization and synthesis of silver nanoparticles using Isaria fumosorosea against human vector mosquitoes

Abstract

The efficacy of silver generated larvicide with the help of entomopathogenic fungi, Isaria fumosorosea (Ifr) against major vector mosquitoes Culex quinquefasciatus and Aedes aegypti. The Ifr-silver nanoparticles (AgNPs) were characterized structurally and functionally using UV-visible spectrophotometer followed by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy and Fourier transform infrared (FTIR) spectra. The optimum pH (alkaline), temperature (30 °C) and agitation (150 rpm) for AgNP synthesis and its stability were confirmed through colour change. Ae. aegypti larvae (I-IV instars) were found highly susceptible to synthesized AgNPs than the larvae of Cx. quinquefasciatus. However, the mortality rate was indirectly proportional to the larval instar and the concentration. The lethal concentration that kills 50% of the exposed larvae (LC50) and lethal concentration that kills 90% of the exposed larvae (LC90) values of the tested concentration are 0.240, 0 0.075.337, 0.430, 0.652 and 1.219, 2.210, 2.453, 2.916; 0.065, 0.075, 0.098, 0.137 and 0.558, 0.709, 0.949, 1.278 ppm with respect to 0.03 to 1.00 ppm of Ifr-AgNPs against first, second, third and fourth instars of Cx. quinquefasciatus and Ae. aegypti, respectively. This is the first report for synthesis of AgNPs using Ifr against human vector mosquitoes. Hence, Ifr-AgNPs would be significantly used as a potent mosquito larvicide.

Isaria fumosorosea‐based zero‐valent iron nanoparticles affect the growth and survival of sweet potato whitefly, Bemisia tabaci (Gennadius)

“…Furthermore, the appearance of a characteristic band around 470 µm during the UV‐spectroscopic characterization of filtrate also confirmed the formation of nanoparticles. Our results can be correlated to the findings of Banu and Balasubramanian, Mukherjee et al and Amersan et al , who have all reported similar synthesis of metal‐entomopathogenic fungi nanoparticles. The change in colour of filtrate during the biosynthesis of nanoparticles can be attributed to the following: (i) the excitation of surface plasmon vibration of nanopraticles and (ii) bio‐reduction of metals related to the metabolic utilization of nitrate through reduction of nitrate and ammonia .…”

“…For SEM, fungal nanoparticles were processed by using the methods of Banu and Balasubramanian and Amersan et al The nanoparticles produced were washed three times with 0.1 M potassium phosphate buffer (pH = 7.2). The material was then fixed with 2.5% glutaraldehyde in PBS buffer for 3 h at 4 °C then rinsed twice with PBS for 10 min each time followed by rinsing with ddH 2 O.…”

“…Similarly, in the current study the presence of ZVI was confirmed by characteristic peaks at 44.72, 65.070, 82.339 and 82.65 corresponding to 200, 220 and 311 (Bragg's reflection) in XRD analysis. The FTIR spectra of nanoparticles showed that different biomolecules such as proteins can be responsible for the synthesis of ZVI‐ I. fumosorosea nanoparticles …”

“…In our study, the smaller/younger immature stages experienced higher mortality compared to the larger/older instars. The findings in this investigation indicate that susceptibility of the insect stages to the ZVI‐ I. fumosorosea nanoparticles is in the order of second instar > third instar > pupa, which is consistent with previous research on the pathogenicity of metal‐entomopathogenic fungi nanoparticles against different insect species . The parametric indices of median lethal concentration (LC 50 ) and median lethal time (LT 50 ) are commonly used to observe the effectiveness of any pest control agent.…”

“…In recent years entomopathogenic fungi have been used as reducing agents for metal nanoparticle synthesis because of their environmental benign and renewable energy production . Silver nanoparticles using different species of entomopathogenic fungi ( Metarhizium anisopliae , Beauveria bassiana and I. fumosorosea ) have recently been used as biopesticides against different mosquito species …”