NANOfeatures: focus on NANOparticles characteristics: modelling exposure and toxicity

• Autor(a) principal: Mendes, Luís André Lima da Gama
• Data de Publicação: 2018
• Idioma: eng
• Título da fonte: Repositórios Científicos de Acesso Aberto de Portugal (RCAAP)
• Texto Completo: http://hdl.handle.net/10773/25922
• topic: Nanomateriais; Tempo de exposição; Cobre; Prata; Solo; Revestimento; Interação entre espécies; Diferentes níveis organizacionais; Iões; Efeitos transgeracionais; Reprodução; Tamanho; Stress oxidativo; Predação; Abundância; Acumulação

Nanomaterials (NMs) have taken an important role in everyday life, due to several applications in different areas (biomedical, engineering, entertainment…). While useful to man, the hazardous potential of the many NMs produced has not been fully assessed. Most of the anthropogenic waste end up in the soil by a variety of routes, becoming available to the species that make up the soil ecosystems. The potential toxicity of these NMs to soil invertebrate ecosystems represents a knowledge gap in the design and use of safer NMs that must be challenged. In the present thesis, the standard model organism Folsomia candida was exposed to different metal-based NMs, either pristine or modified, and its salt counterparts in increasing complex media, from standardized testing to soil multispecies systems (SMS), and increasingly exposure period, reflecting real-life scenarios. A multi-endpoint approach on several organizational levels (cellular, organism, population up to a full ecosystem level) was used, assessing the contributions of four main concepts for the development of NM toxicity: time, transformation in exposure media, modification of the NMs and species interactions. Due to exposure to AgNM and AgNO3 in a 10 days and a standardized (28 days) timeframe, antioxidant defences were activated and metallothionein production increased, with a later response to nano than to non-nano form, while no significant differences in reproduction were observed after NM exposure. In a multigenerational continuous exposure (6 generations - 186 days) to AgNO3, an effect on reproductive output was shown, even after transfer to clean soil. With the increasing number of generations, transgenerational effects were observed, with a decrease in the size of the organisms, inferring an adaption in adverse conditions to avoid extinction. In the SMS testing, it was observed that CuO NMs toxic effects on species abundance increased on a long-term exposure (84 days) while copper salt form (CuCl2) resulted in a more immediate impact. The modification of CuO NMs with different coatings resulted in different response degrees between species and the ecosystem dynamics on the long term, correlated with the acquired zeta potential. Overall, the negative charged NMs were more toxic than positive charged NMs, while non-charged NMs produced effects on a shorter timeframe. It was shown that species interactions and the NM exposure have a synergistic effect on the ecosystem composition and dynamics. While virtually all of the copper was attached to the soil matrix, F. candida internal copper concentration varied both in maximum concentration and with time, according the NM coating. Concluding, metal-based NMs toxicity increases with time and while cellular changes are shown in short exposures, their impact on higher organizational levels are only shown on longer exposure times. An increase in the standardized testing timeframe is suggested to accommodate NM toxicity assessment.