Mangrove Helps: Sonneratia alba-Synthesized Silver Nanoparticles Magnify Guppy Fish Predation Against Aedes aegypti Young Instars and Down-Regulate the Expression of Envelope (E) Gene in Dengue Virus (Serotype DEN-2)

The control of dengue vectors with effective tools is crucial. Here, we fabricated silver nanoparticles (AgNP) using a cheap method relying to a mangrove extract (Sonneratia alba) as a reducing and stabilizing agent. AgNP were charac- terized by UV–vis spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy and X-ray diffraction. LC50 of S. alba extract against Aedes aegypti ranged from 192.03 ppm (larva I) to 353.36 ppm (pupa). LC50 of AgNP ranged from 3.15 (I) to 13.61 ppm (pupa). Sub-lethal doses of AgNP magnified predation rates of guppy fishes, Poecilia reticulata, against Ae. aegypti and Chi- ronomus kiiensis larvae. Mangrove-fabricated AgNP were evaluated for their antimicrobial potential against Bacillus subtilis, Klebsiella pneumoniae, and Sal- monella typhi, using the agar disc diffusion and minimum inhibitory concentration protocol. Notably, S. alba-synthesized AgNP tested at doses ranging from 5 to 15 lg/mL down-regulated the expression of the envelope (E) gene and protein in dengue virus (serotype DEN-2), while only little cytotoxicity rates (i.e.\15%) were detected on Vero cells when AgNP were tested at 10 lg/mL. Overall, this study pointed out the potential of S. alba-synthesized AgNP to develop eco-friendly nanoformulations effective against dengue virus and its mosquito vectors.