Mosquito larvicidal activity of silver nanoparticles synthesized using Azolla pinnata against Culex quinquefasciatus Say (Diptera: Culicidae) J John Wilson, Shunmugiah Mahendran, T Sivakumar, P Ponmanickam, R Thangaraj South African Journal of Botany, 2023 Vector control is a significant component of interventions to control mosquito-borne diseases. In the present study, silver nanoparticles (Ag NPs) were synthesised using the seaweed Azolla pinnata to evaluate larvicidal activity against Culex quinquefasciatus. The biosynthesis of Ag NPs using Azolla pinnata extract was confirmed by the visible change in colour of the reaction mixture from light green to brown. UV–Vis spectra analysis showed that absorbence peaks at around 254 nm due to the surface Plasmon resonance of the silver nanoparticles. The analytical studies of SEM, EDX, FTIR, and XRD analysis results supported the confirmation of Ag NPs. Synthesized Ag NPs were assessed for the mortality rate of Culex quinquefasciatus. Based on LC50 and LC90 analysis, 4.287μl/ml of Ag NP is required to kill 50% of the larvae, whereas 10.795μl/ml is necessary to kill 90% of the larvae. Moreover, the synthesised Ag NPs exhibit high bioactivity on mosquito larvae and can thus be utilised as a biological control agent to control mosquito populations.
Biogenic Synthesis of Silver Nanoparticles Using Pantoea stewartii and Priestia aryabhattai and Their Antimicrobial, Larvicidal, Histopathological, and Biotoxicity Potential Jeyaraj John Wilson, Thangamariyappan Harimuralikrishnaa, Thangavel Sivakumar, Shunmugiah Mahendran, Ponnirul Ponmanickam, Ramasamy Thangaraj, Subramanian Sevarkodiyone, Naiyf S. Alharbi, Shine Kadaikunnan, Baskar Venkidasamy, Muthu Thiruvengadam, Rajakumar Govindasamy Bioengineering, 2023 In recent years, green nanotechnology has gained considerable importance for the synthesis of nanoparticles due to its economic viability and biosafety. In the current study, silver nanoparticles were synthesized using two bacterial isolates, H2 and H3, which were isolated from soil samples collected from the Western Ghats, Tamil Nadu, and identified at the species level as Pantoeastewartii (H2) and Priestiaaryabhattai (H3) by sequencing their 16s rRNA genes. Intracellularly synthesized silver nanoparticles were characterized by UV–visible spectroscopy, Fourier transform infrared spectroscopy, atomic force microscopy, and particle size analysis. AFM studies show that both of the bacterial synthesized Ag NPs were circular-shaped and disaggregated, with an average size distribution of 4 nm for Pantoeastewartii and 3.6 nm for Priestiaaryabhattai. Furthermore, their larvicidal activity, antimicrobial, histopathological, and biotoxicity effects were determined. The synthesized Ag NPs exhibited potent larvicidal activity against fourth instars of Ae.aegypti, An.stephensi, and Cx.quinquefasciatus exposed to a 50 µg/mL concentration for 24 h based on their LC50 and LC90 values. Histopathological studies of the affected mosquito larvae clearly show damage to the epithelial cells, food bolus, basement membrane, muscles, and midgut parts. The maximum antimicrobial activity of Priestiaaryabhattai-synthesized Ag NPs was observed for Streptomyces varsoviensis MTCC-1537, and that of Pantoea stewartii-synthesized Ag NPs was against Escherichia coli MTCC-43. The toxicity test on non-target organisms such as Artemia nauplii and zebrafish embryos indicates no visible abnormalities or mortality after their exposure for 48h. It is concluded that silver nanoparticles can easily be synthesized using Pantoea stewartii (H2) and Priestia aryabhattai (H3) as capping and reducing agents. Silver nanoparticles showed potent larvicidal activities and could potentially be used in integrated vector control programs because they are safe for other inhabitants of the same aquatic environment as mosquito larvae.
