Abstract
In this work we studied the ability of polystyrene (PS) nanoplastics (NPs) and microplastics (MPs) to transfer benzo(a)pyrene (BaP) to mussel hemocytes and to produce toxic effects in vitro. For this, intracellular fate and toxicity of PS NPs (0.05 μm) and MPs (0.5 and 4.5 μm) alone or with BaP and of BaP alone were assessed. Particles of 0.05 and 0.5 µm largely aggregated in the exposure medium whereas presence of BaP reduced particle aggregation. Cells internalized PS NPs and MPs alone or with BaP and these were found inside and outside lysosomes, depending on their size. PS particles alone or with BaP were cytotoxic to hemocytes only at the highest concentrations tested. The same was true for most sublethal endpoints except for increased phagocytic activity provoked by NPs and 0.5 μm MPs at lower concentrations. Plastic particles appeared to be the main drivers for reduced plasma membrane integrity and increased phagocytic and lysosomal activities whereas BaP appeared to contribute more to reduced cell viability and phagocytosis and increased ROS production and genotoxicity. Overall, PS NPs and MPs can act as carriers of BaP to mussel hemocytes, rising concerns about risks plastics associated to pollutants may pose to aquatic organisms.
Highlights
In this work we studied the ability of polystyrene (PS) nanoplastics (NPs) and microplastics (MPs) to transfer benzo(a)pyrene (BaP) to mussel hemocytes and to produce toxic effects in vitro
Dynamic Light Scattering (DLS) was used to assess hydrodynamic size and surface charge of NPs and MPs alone or in combination with BaP suspended in supplemented Basal Medium Eagle (BME) and distilled water (DW)
Aggregation was more pronounced in BME than in DW and differences were higher in 0.05 μm NP suspensions (DW: 184.3 nm; BME: 7700 nm) followed by suspensions of 0.5 μm MPs (DW: 742.6 nm; BME: 2328 nm) and 4.5 μm MPs (DW: 5009 nm; BME: 6777 nm) (Table 1)
Summary
In this work we studied the ability of polystyrene (PS) nanoplastics (NPs) and microplastics (MPs) to transfer benzo(a)pyrene (BaP) to mussel hemocytes and to produce toxic effects in vitro. Due to lack of standardized methodology for sampling, extraction and analysis of MPs in environmental samples, it is difficult to determine actual exposure concentrations and levels of MPs accumulated in biota, but recent studies showed that the size fraction below 150 μm in size is being overlooked in most published studies relying on FTIR for polymer identification[8] Due to their small size, MPs can be confounded as food particles by many marine organisms, such as zooplankton, fish, mammals and specially by filter-feeder organisms such as b ivalves[9,10,11,12]. At cellular and subcellular levels, in vitro studies in hemocytes have suggested that NPs and MPs are internalized into
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