Toxicidade de nanopartículas de prata em modelos aquáticos e a interferência do meio na agregação da nanopartícula

Abstract

Silver nanoparticles (AgNP) are of high industrial interest, standing out for their antiseptic and antifungal properties and versatility in drug delivery. However, the expansion of their employability is directly linked to the increase in the disposal of these nanoparticles in the environment. Worldwide, regulations such as REACH and the EPA exist, although not specifically targeted, which cover the use, production, and disposal of nanoparticles. In Brazil, Bill 880/2019 (Legal Framework for Nanotechnology) stands out. Regardless of regulation, risk assessment of a nanomaterial to be used on a large scale is a basic requirement to ensure the safety of use. Aiming to standardize toxicity and experimental parameters, the OECD establishes standards, guidelines, and study models for testing materials. Among the model organisms for studies in aquatic environments and food chains are the microalgae Chlamydomonas reinhardtii, the microcrustacean Artemia salina, and Danio rerio embryos. These organisms were chosen for testing exposure to AgNP concentrations (12.5, 25, and 50 ppm) and testing the trophic level passage of nanoparticles through their synthesis, characterization of AgNP, and analysis of damage caused to the models using microscopy. The AgNP used was synthesized in collaboration and analyzed in UV-Vis, with two syntheses and one standard, and ten (10) times more concentrated; the exposure experiments in the three models were carried out by diluting the synthesized AgNP in the respective model media with analyses every 24 hours. The trophic level experiment consisted of exposing C. reinhardtii previously contaminated with AgNP concentrations to A. salina (nauplii I and II), and at the end of the experiments, the samples were collected and fixed for optical, scanning electron, and confocal microscopy. The results obtained showed that in the A. salinas medium, colloids tend to form, visible in the digestive tract of the specimen without causing morphological changes or mortality. In the homemade TAP medium, AgNP does not show the same tendency to aggregate, in addition to decreasing the replication speed of C. reinhardtii, which form colonies surrounded by a transparent secretion. D. rerio embryos showed 100% mortality, and the trophic level experiment showed no toxicity caused by the ingestion of C. reinhardtii contaminated by A. Salina. It is concluded that the exposure medium directly influences the toxicity of AgNP, which proved to be toxic when kept in its non-aggregated state.