Avaliação da toxicidade da suspensão de nanopartículas de prata estabilizadas com pva utilizando como organismo teste o microcrustáceo daphnia magna

Abstract

Over the years there was an increase in the use of nanoparticles (NP) in several products, mainly for antiseptic purposes. In this sense, the silver nanoparticle (AgNP) is widely used because of the high antimicrobial potential. Thus, at the same time that the AgNP is used it is also constantly released into the environment, and the interactions can cause serious damage. Therefore, the present study aimed to evaluate the acute and chronic toxicity of AgNP suspensions maintained under natural temperature and luminosity conditions and also controlled in the laboratory, using the microcrustacean Daphnia magna as test organism. The AgNP were synthesized and characterized by a classical method of chemical synthesis. Subsequently, acute and chronic toxicity tests for three different exposure conditions, sequentially: AgNP suspension maintained at a temperature close to 4ºC; suspension under controlled conditions of 20°C for 21 days and stirring suspension kept under natural temperature and luminosity conditions for 21 days. From the characterization it was found that the suspension of NP was not in an aggregated state, but due to its low stability the aggregation would be possible. Due to the performance of the acute tests in the three exposure conditions, it was possible to observe a certain variation for the values of EC50,48h and the highest toxicity obtained was 0.14μg·L-1 for the AgNP suspension maintained at the next temperature at 4°C. Meanwhile, acute tests considering other exposure conditions resulted in EC50,48h values variables ranging from 0,14μg·L-1 to 0,52μg·L-1 over the 21 days and the lowest toxicity occurred from exposure of the organisms to the suspension maintained under natural conditions. Regarding the chronic tests considering the suspension of AgNP maintained at a temperature close to 4°C and the suspension kept under stirring at a temperature close to 20°C, it was verified that the significant chronic effects occurred mainly for the parameters: reproduction, posture and growth and the resulting effect concentrations are in the range of 0.035μg·L-1 to 0.065μg·L-1. In contrast, for the sitirring suspension under natural conditions, significant chronic effects were observed only for the growth parameter, and the effect concentration was 0.055μg·L-1. Thus, based on the study, it was concluded that the exposure of the suspension to the natural conditions provided the minimization of the toxic effects of the AgNP considering the exposure time of 21 days.