Silver nanoparticles (AgNPs) have received great attention because of their unique characteristics and applications from basic to applied sciences. Recently, studies have also shown applications as larvicides against Aedes aegypti larvae [1], which generates great interest in public health due to the annual outbreaks Zica virus in Brazil, being associated with the recent cases of infants born with microcephaly. We synthesized AgNP, using polymethacrylic acid (PMAA) as a stabilizing and reducing agent catalyzed by ultraviolet radiation. The synthesis is clean, quick and low cost and average size of 10nm. Their use as nanolarvicide against Aedes aegypti in laboratory and field simulation will be reported. To check efficiency as larvicide the AgNPs were performed pilot bioassays, in which 20 fourth-instar larvae were placed in 100 ml of water with small concentrations of AgNPs (0.02 to 1.1 ppm). It was observed the mortality of the larvae from 6h and maximum expression of 24h exposure. The values LC50 and CL90 are 0.027, 0.044 ppm, respectively were recorded after 24 hours of exposure [2]. For the simulated field test, the initial efficacy, estimated by larval mortality in the first 96 hours after application of the product, was performed using 50 young instar-L1/recipient (20 liters). It was observed 100% mortality of the larvae in L1-instar in 96h of exposure of the nanoparticles. The persistence of mortality of the larvae in the L1-instar was observed up to the present moment by five months of exposure of the nanoparticles.
[1]N. Sap-Lam et al., “UV irradiation-induced silver nanoparticles as mosquito larvicides,” in Journal of Applied Sciences 10(23), pp. 3132–3136 (2010)
[2]Carvalho et al.; "Exploiting silver nanoparticles with PMAA against aedes aegypti larvae development: potential larvicidal activity" In Colloidal Nanoparticles for Biomedical Applications XIII, SPIE, San Francisco, pp. 23 (2018)
Aedes aegypti is one of the mosquito species with major epidemiological importance in Brazil, involved with the transmission of the arboviruses such as Dengue, Chikungunya and Zika. Since the mosquito is well adapted to the urban environments, where there are large amounts of breeding sites for larvae and pupae, its control has become increasingly difficult. Since 1996, the usual control is made by using chemical larvicides, but the continued use of some of these compounds has led to the selection of A. aegypti resistant populations. Therefore, the search for new insecticidal substances is necessary to guarantee the control of this specie. Our goal is to establish a new larvicide with high toxicity without the drawback of resistance. For this, we developed a low-cost green synthesized silver nanoparticles with a poly(methacrylic acid) outer layer, catalyzed with ultra violet light. We tested nanoparticles samples produced from different batches in laboratory bioassays against fourth-instar larvae. The results showed a desired toxic activity, presenting 10% to 100% of mortalities in concentrations ranging from 0.01 to 1.1 ppm, and from the bioassay we have obtained LC50 = 0.027 ppm and LC90 = 0.044 ppm, after 24 hours of exposure. Imaging the threated larvae by optical microscopy and optical coherence tomography helped to clarify the potential larvae death mechanism. These results associated with the simplicity and low cost of production of these silver nanoparticles, reveal their great potential for the development of products to control of A. aegypti larvae.
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