Hazard assessment of single and mixed exposures to nanoplastics and caffeine on in vivo and in vitro models of Xenopus laevis

• Autor(a) principal: Gomes, Fábio Miguel Ribeiro
• Data de Publicação: 2022
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/36281
• topic: Amphibians; Cell lines cytotoxicity; Embryos and tadpoles ecotoxicity; Human pharmaceutical; Teratogenic effects; Polyhydroxybutyrate nanoparticles

Pollution is one of the major impacting drivers on wildlife populations, especially on amphibian´s due to their high susceptibility to xenobiotics. Plastic contaminants have been a target of extensive risk assessment research, mainly because of their environmental persistence. Polyhydroxybutyrate (PHB) is a bio-based and biodegradable polymer, that although regarded as non-toxic in medical related experimentations, its ecological impact has yet to be fully evaluated, particularly regarding its nano-sized particles (NPs). In addition to its individual exposure threat, nanoparticles may serve as vectors for chemicals, promoting its incorporation by biota. Caffeine is the world's most widely consumed psychoactive drug and a relevant representative of pharmaceutically active pollutants in surface water bodies. Amphibians are both prey and predators of freshwater ecosystems, playing a key role in population dynamics. Nonetheless there is a lack of knowledge regarding amphibians’ sensitivity to emerging to contaminants. This work comprises two main goals: (i) assess the individual and combined effects of caffeine and bioplastics (PHB-NPs) to early life stages of Xenopus laevis; (ii) determine the adequacy of in vitro assays as non-animal alternatives for first tiers of amphibian aquatic stages risk assessment. To achieve this, the toxicity of caffeine and PHB-NPs was assessed individually and in mixture, in 96-h assays with embryos and tadpoles of X. laevis, and in 72-h assays with A6 e XTC-2 cell lines of X. laevis. The present study provides the first experimental evidence of cytotoxic impact initiated by novel bio-nanoplastics and caffeine exposure, either as a single contaminant or in combination, to amphibian in vitro models. Caffeine proved strong effects on survivorship, malformations, heartbeat, and body growth, on both early life stages, while PHB-NPs displayed no toxicity on X. laevis. PHB-NPs and caffeine co-exposure displayed no apparent interaction on in vivo models, while on in vitro assays both examples of antagonism and synergism were observed. Embryos were consistently more sensitive than tadpoles to caffeine, with LC₅₀ of 196 and 226 mg/L, respectively. Live models were more susceptible to caffeine than both A6 (587 mg/L) and XTC-2 (864 mg/L) cell lines, while for PHB-NPs the opposite was observed. Even though PHB is regarded as a biodegradable and biocompatible polymer, our results indicate that PHB-NPs displayed cytotoxic potential. Thus, it is pivotal to further explore the effects of PHB-NPs on in vivo models, in order to better understand its suitability as an environmental-friendly alternative.