(165i) Toxicity of Magnetic Nanocomposites Using Zebrafish As a Biological Model

The use of nanomaterials has significantly increased in different fields, such as medical applications, environmental industry, and manufacture. Magnetite, normally used as a core material in nanoparticles has magnetic properties that makes it attractive for various applications. Surface-functionalized magnetite nanoparticles has been proposed as a mechanism in the treatment of wastewater due to their high reactiveness, high ratio of surface area per weight and their magnetic properties that allow easy recovery and reuse. The functionalization of magnetic nanoparticles is achieved by treating the surface of nanoparticles through physical or chemical means. Every surface functionalization generates a new compound, that may have different properties of interaction. Since many of them are intended to be used in aqueous solutions, it is necessary to implement toxicity and environmental tests on aquatic ecosystems and animal models, and identify the potential effects of their use in natural environments. For this, we selected the zebrafish animal model for toxicity evaluation assessment as recommended by the Organization for Economic Co-operation and Development (OCDE). Zebrafish have characteristics that allow it to comply with the fundamental principle of animal research known as the 3Rs (i.e. replacement, reduction, and refinement). Some positive attributes in the use of zebrafish as an animal model include its rapid organogenesis (6 days about), low maintenance cost, good transparency of the embryos, the possibility to examine the development of internal structures, and a similarity of about 70% with the human genome. In this study, we determined the effect on the morphology, survival rate, and reproductivity using zebrafishs, as a biological model, by their exposition to different magnetic nanocomposites with and without surface functionalization.

Toxicity was determined by means of hatching index, survival, malformation, and bioaccumulation of the nanocomposites in embryo of 8 hours post-fertilization and larvae of 4 days pos-fertilization. Additionally, behavior tests were performed to prove changes due to the presence of nanocomposites in the water. Magnetite nanoparticles were synthesized by the chemical co-precipitation method and different surface functionalizations were applied to obtained five different nanocomposites. (3-Aminopropyl) triethoxysilane (APTES), L-Cysteine (Cys) and 3-(triethoxysilyl) propylsuccinic anhydride (CAS) were used as functionalization molecules, thus, the five different nanocomposites corresponded magnetite nanoparticles (MNP), MNP+APTES, MNP+CAS, MNP+Cys, MNP+APTES+Cys, Egg Water was used as negative control and 3,4-Dichloroaniline as positive control. All these nanocomposites were design for the treatment of wastewater; however, in this work, the purpose was to evaluate the possible effects of toxicity on the animal model rather than their wastewater treatment effectiveness. All nanocomposites were evaluated at concentrations of 1, 10, 100 and 1,000 µg / ml, that included the protocol range of OECD (2013). Three replications were performed for each treatment with a (n) of 10 individual per nanocomposite and were exposed for 96 hours with treatments changes every 24 hours. Results showed that, at the concentration of 1,000 µg / ml the nanocomposites accumulated in the chorion delayed the hatching of the embryos by approximately 24 hours when compared to the other concentrations. At lower concentrations, although having accumulation of the nanocomposites on the chorion, hatching rate did not present a significant change compared the negative control. Both larvae and embryo tests showed a trend relating the increase of nanocomposite concentration with the decrease of the survival rate (up to 11 ± 1%) the increment in the number of malformations (up to 6 ± 1%) and the appearance of anxious behaviors (i.e. some groups showed a high sensitivity to light stimulation, while others did not react). Reproduction of the treated animals was also evaluated, and the results showed that none of the tested nanocomposites affected their reproduction. Therefore, it can be concluded that the tested nanocomposites could be a viable alternative in wastewater remediation. In general, the toxicity of these magnetic nanocomposites is low (between 3% and 12%), and considering that their final concentration, obtained after wastewater treatment and magnetic recovery, can be even lower than those tested, our results suggested their viable use in this type of applications. However, more detailed studies are recommended to determine internal bioaccumulation of nanocomposites in the animal model.

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