Efeitos de toxicidade de nanopartículas metálicas para espécies de microalgas marinhas e dulcícolas: uma revisão

Abstract

Due to the development and expansion of the use of nanomaterials, there was a growing concern about the potential risks that exposure to these substances can generate to biological systems and human health. To assess these effects, toxicological tests are used where a test organism is exposed to different concentrations of the substance of interest. In this review, the organisms evaluated were microalgae species, as they are representative elements of the aquatic ecosystem, so that, being at the base of the food chain, they serve as food for other organisms. Thus, this work aimed to provide a general and comprehensive overview of the literature on the toxic effects of suspensions of metallic nanoparticles of cobalt, silver and copper on several species of microalgae, both in freshwater and saltwater environments, verifying how the characteristics of these substances can interfere with the observed effects. In the literature, the effects described are the most diverse, but the main one is the inhibition of growth. Among the most cited are also oxidative stress, damage to the structure of the plasma membrane and reduction in photosynthetic efficiency. A comparison between the studies was made taking into account the results presented, as well as the effects and particularities of each nanoparticle. With that, it was noticed that, although the great majority of studies highlight the importance of characterizing these substances, little is known about the relationship of these properties on the observed effects. As the results are very variable and the studies, for the most part, are more restricted, it was found that the answers obtained for a study are valid for that specific study and under those conditions, for that same species of microalgae, because any variations in the system, can significantly alter the severity of the effects, since the properties of these substances act together forming, thus, something quite complex. However, ir was noticed that some points are fundamental and determinant in the toxicity of these chemical substances, such as the size of the nanoparticle, the levels of agglomeration and the amount of ions released. Therefore, it was concluded that it is extremely necessary to understand the interaction of these nanoparticles with the organisms in an integrated manner, in situations closer to reality, in order to determine acceptable concentration limits to be deposited in water resources, reducing the pollution of the ecosystem, as well as seeking to avoid long-term problems.