Avaliação da toxicidade aguda de nanopartículas de óxido de cobalto utilizando o organismo teste Daphnia magna

Abstract

Nanoparticles (NPs) can be applied in several areas among them in the engineering of computers and catalysts. In this sense, the nanoparticle Cobalt (CoONP) is used in the catalysis, due to the semiconductive and electrocatalytic properties of NP. Therefore the present study evaluated the acute toxicity and the subacute effects of nanoparticles of Cobalt, using the microcrustacean Daphnia magna as a test organism. The NPs were synthesized in suppressions and later characterized to confirm their characteristics, the methods used in the characterization were the Transmission Electron Microscopy and the average diameter of 3 nm was obtained, the formation of agglomerates of nanoparticles was also observed, this effect of agglomeration was confirmed by the Dynamic Light Scattering Measurement which reported a hydrodynamic diameter of 30 nm and polydispersity indexes of more than 0.2 confirming a dispersion heterogeneity of the particles. The state of agglomeration of the NPs can be associated with a large surface area of 224.7 m2 / g, the physical properties of cobalt and also due to the electrostatic forces present in the diluting media used in the process of evaluation of the acute and sub-acute toxicity of nanoparticles. The zeta potential confirmed NP instability in the three different diluting media, the instability of the suspension contributes to the agglomeration effect of the nanostructures. Through the tests of acute toxicity developed, an EC50, 48h equal to 349 μg / L was obtained. In order to evaluate the sub-acute effects related to CoONP, a culture of D. magna was maintained on exposure to a concentration of 50 μg / L of NP, those made over time on the organisms were verified as early mortality of matrices and reduction in pups generation, in which the reproduction in the control was 60% higher than that verified in the batch exposed to CoONP. The EC50,48h was again evaluated at this time from the organisms maintained in toxic medium in order to compare with the EC50 obtained above, the value reached was 302 μg / L, it was then found that exposure over the time the CoONP induced a reduction of toxicity of 14%, making the substance more toxic, because the closer to zero the more toxic the substance.