Effects and applications of nanomaterials in environmental remediation

• Autor(a) principal: Rocha, Alexandre Miguel Mendes Portugal da
• Data de Publicação: 2021
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/30859
• topic: Nanotechnology; SiO2 Nanoparticles; Environmental remediation; Behavior; Embryonic development

Although many restrictions and limits have been established by several competent entities, contamination and pollution of aquatic compartments by transition metals and organic pollutants remains a major problem that is far from being resolved. The truth is that, in addition to preventing contamination, there must be a treatment of already contaminated sites, and the environmental remediation of these contaminants has been proposed as a complementary measure to the restrictions already in force. As interest and progress in the field of nanotechnology deepens, new nanomaterials are launched as an integral part of commercial products or innovative industrial methods. Silica nanoparticles (SiO2 NPs) and magnetic nanoparticles (MNP) are examples of nanomaterials that have been used in numerous applications over the years, ranging from biomedical to environmental applications such as in the adsorption of organic pollutants and metal ions in aqueous media. This way, SiO2 NPs and MNPs emerge as potential highly effective and specific solutions for target contaminants, being still low cost, reusable and, with due treatment, biocompatible. Although the potential for adsorbents based on MNP and SiO2 NPs has already been reported, there is a risk and concern of secondary pollution in the various compartments, endangering aquatic species that inhabit them. Thus, it is extremely important to evaluate the effects of this type of nanomaterials on aquatic organisms and to assess the potential risks to aquatic ecosystems. This study aimed to evaluate toxicity according to the size (80 and 150 nm) and concentration (0, 0.1, 1, 10, 100, 1000 µg.L-1 ) of SiO2 NPs in Danio rerio embryos with a focus in embryonic development and behavioural parameters. The SiO2 NPs were prepared using the Stöber method, and characterized by scanning electron microscopy (SEM) and dynamic light scattering (DLS). The embryotoxicity test was performed with D.rerio embryos in covered 24-well plates at 26 ± 1.0 ° C for 96 h and with a light phase between 16 - 8 h. At 24, 48, 72 and 96 hpf, parameters such as survival rate, time to hatch and morphological changes were measured using a stereomicroscope. Locomotor activity was measured by placing the plates individually in the ZebraBox using the monitoring setting during periods of 3 min of light / 3 min of dark, and the assessment of sublethal behavioural effects was performed by monitoring the movement of each larvae during alternating periods of light, used as a stimulus (LED lighting) and dark (infrared lighting) and recording distances and movement time for each 60 s integration during both dark and light periods. The results indicate that there are some tendencies for SiO2 NPs with 80 nm to affect embryonic development at a concentration of 10 µg.L-1 , the effects including early hatching and loss of balance. The same concentration of nanoparticles with 80 nm also caused effects in behavioural terms, decreasing locomotor activity in the dark, increasing erratic movements and increasing swimming in the outer areas of the wells, constituting an anxiety profile in fish, similar to those found after exposure to anxiogenic compounds.