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 characterized by UV–vis spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy and X-ray diffraction. LC₅₀of S. alba extract against Aedes aegypti ranged from 192.03 ppm (larva I) to 353.36 ppm (pupa). LC₅₀of 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 Chironomus kiiensis larvae. Mangrove-fabricated AgNP were evaluated for their antimicrobial potential against Bacillus subtilis, Klebsiella pneumoniae, and Salmonella typhi, using the agar disc diffusion and minimum inhibitory concentration protocol. Notably, S. alba-synthesized AgNP tested at doses ranging from 5 to 15 µg/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 µg/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.