Use of Bio-fabricated Silver Nanocomposite Capped with Mud Crab Shell (Scylla serrata) Chitosan for Water Purifications and Sustainable Management of Mosquito Vectors at Stagnant Water System in the Semiarid Zone of Tamil Nadu, India

Abstract

Mosquitoes are the major vectors of many diseases such as the malaria, filariasis, dengue, and Japanese encephalitis. Mosquitoes propagate quite successfully in a variety of aquatic habitats such as drinking water system, manmade water bodies, and sewage contaminated aquatic system. Since, water is essential for all life, without it, life won’t progress and at the same time, the quality of the water also important. With the unique structural features present in chitosan bio-polymer helps to bind effectively with fine suspended particles, pollutants, bacteria, heavy metals etc. The biocompatible and biodegradable nature of chitosan makes it a potential candidate for mosquito breeding water purification purposes. In this regard, chitosan has been extracted from freshwater crab shells Scylla serrata and reduced for silver nanoparticle synthesis. It has been utilized as a potent tool in control of young instars of Aedes aegypti and its breeding water purification. Bio-synthesized chitosan-reduced silver nanoparticles were characterized by UV–Vis spectrum, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (E-DAX), and X-ray diffraction (XRD). In laboratory condition, the chitosan silver nanocomplex was found to possess toxicity against young instars (I, II, III, and IV) of Aedes aegypti at the concentrations of 2, 4, 6, 8, and 10 ppm followed by chitosan treatment alone. The surface stagnant water from dengue vector breeding site checked the water purification parameters, such as water temperature (WT), pH, salinity, dissolved oxygen (DO), total dissolved solids (TDS), and electrical conductivity (EC) by using “μP Based Water & Soil Analysis Kit” (Model 1160). Further, from the results it is clearly postulated that the biomolecules present in the chitosan not only showed biopesticidal activity against mosquito larvae and pupae but also nullified the contaminants in the water and made human usage.