The pivotal role of bioenergetics in characterizing the hazards of polystyrene and polyethylene nanoparticles to bivalve health and development.

Coastal marine biodiversity is expected to suffer from rising production of plastic waste. When reaching the micro and nanoscale, plastic particles can disrupt animal bioenergetic systems, threatening their physiological adaptations to coastal habitats. Here, we examined the metabolic toxicity of various nanoplastics in cells (hemocytes) and embryos of oysters Crassostrea gigas, including 50 nm cationic and anionic polystyrene nanoparticles (named CatPS_50 and AnPS_50), 50 nm cationic and anionic polyethylene nanoparticles (named CatPE_50 and AnPE_50), and 100 nm cationic and anionic polyethylene nanoparticles (named CatPE_100 and AnPE_100). The polystyrene nanoparticles were obtained from a commercial source and contained surfactants and bactericides, while the polyethylene particles were synthesized from polyethylene material by emulsion polymerization without the use of charged surfactant or bactericides. In vitro cellular toxicity screening based on overall metabolic activity reveals three main findings: (i) Polystyrene nanoparticles exhibited greater toxicity based on EC50 estimates - the origin of which has not been established linked to several confounding factors (polymer/surfactant/bactericide), (ii) 50 nm particles were more toxic compared to 100 nm, and (iii) cationic nanoparticles were the most toxic. Increased temperature worsened the toxicity of most nanoparticles, and cationic nanoparticles at sublethal concentrations reduced cellular ATP levels. Among the nanoparticles tested, CatPS-50 was the most toxic, increasing oxidative stress and blocking metabolic adaptation to temperature stress. Our findings suggest that different types of nanoplastics can affect cellular bioenergetics to varying degrees, which may partially explain the differences in their toxicity profiles. Furthermore, studies with oyster embryos are ongoing and will be detailed during the presentation. Our first results show that polystyrene nanoparticles presented the highest toxicity (EC50=5 to 300 mg/L, depending on temperature), restricting metabolic responses to temperature and significantly inhibiting early larval growth. To clarify toxicity, further analyse of interaction with biological membranes and possible intracellular localizationis of great interest. Also see: https://micro2024.sciencesconf.org/559573/document