Encapsulation of silver nano crystals using Salvinia molesta against the Anopheles stephensi and oxidative stress enzyme activity of larvivorous fish

Abstract

Anopheles mosquitoes, which are the main carriers of the disease throughout India, Asia, and the Middle East, are the ones that cause malaria. The role of water predators in mosquito aquatic stage regulation is still recognized. With the use of synthetic insecticides, the environment became contaminated and insects developed high resistance to chemical pesticides. Based on our outline, we anticipated an innovative technique of bioencapsulated silver nanoparticles (AgNPs) using Salvinia molesta, which would perform as a reducing and stabilizing agent. Bioencapsulated-AgNPs existed and were classified using a variety of physiochemical techniques. In bioassays, the LC50 values of S. molesta aqueous extract against Anopheles stephensi range from 240.247 (1st instar larvae) - 428.851 ppm (pupae), LC50 of S. molesta-encapsulated AgNPs ranges from 20.010 (1st instar larvae) to 35.676 ppm (pupae). An experiment with S. molesta extract and encapsulated AgNPs was conducted in the open environment, and the larval reduction of mosquitoes was 100% after 72 h. In the ovicidal activity of An. stephensi, hatched eggs were reduced by 100% when treated with 40 ppm of encapsulated AgNPs and 500 ppm of S. molesta extract and encapsulated AgNPs, which significantly reduced the life span of malarial mosquito adults. Furthermore, we investigated the predatory ability of the larvivorous fish Aplocheilus blockii against third and fourth instar larvae of An. stephensi in laboratory conditions using ultra-low doses of bioencapsulated-AgNPs. Regarding non-target impact, in a conventional laboratory environment, the predation efficacy of the larvivorous fish A. blockii, was 58.58% and 54.78% against the 3rd and 4th instar larvae of An. stephensi, respectively. In bioencapsulated AgNPs-contaminated circumstances, fish predation was amplified to 78.18% and 75.54%, respectively. A. blockii was exposed to sublethal concentrations of AgNPs, namely 5, 10, and 15 g/ml, in enzymatic assays to assess changes in GST and AChE activity after 16 days. This study advances our understanding of the contagiousness of water-floating fern-conveyed insecticides and bioencapsulated AgNPs against therapeutically important insects, allowing us to recommend the proven materials as effective candidates to evolve the most recent and cost-effective pest management tools, and the long-term use of this larvivorous fish during wetlands and associated An. stephensi larval ecologies in various parts of the country is proposed.