Does triclosan adsorption on polystyrene nanoplastics modify the toxicity of single contaminants?

, Binelli Andrea, Parenti Camilla Carla, Magni Stefano, Della Torre Camilla.

Physical and chemical properties of nanoplastics make them potential carriers for some environmental contaminants, enhancing their biological effects. Nevertheless, the toxicity caused by pollutant adsorption on nanoplastics is still controversial, depending on the interactions between chemical and physical pollutants, the consequent change in bioavailability, the modification in the intake, transport and accumulation in the organisms and also on the characteristics of contaminants. Among the environmental pollutants, the triclosan is considered as a contaminant of emerging concern for aquatic ecosystems, and its adsorption capability on polymers has been already demonstrated. In this context, we evaluated the combined effects made by 0.5 µm nanobeads of polystyrene and triclosan adsorbed on their surface in comparison with those caused by the single contaminants. The systemic effects of 7-day exposure to nanoplastics, triclosan alone, and to the nanoplastics-triclosan complex have been analyzed employing zebrafish larvae and using a multi-tier approach. Firstly, confocal microscopy evidenced nanobeads ingestion and translocation in several tissues and organs to guarantee the goodness of the exposure results. Behavioral assays were then conducted to highlight larval swimming defects as a ‘real-time' readout of the potential effects on the whole organism, while a suite of several biomarkers and functional proteomics were applied to investigate the effects at both cellular and molecular levels. The whole dataset pointed out a clear modification in the toxicological effects of the nanoplastics-triclosan complex in comparison with the single contaminants, proved by opposite behaviours in the larval swimming activity and modulation of diverse protein classes, some of which just related to the behavioural modifications, as well as by different effects on several biochemical endpoints. This means that the interaction between chemical and physical pollutants leads to more complicated responses than additive, synergistic or antagonist models, resulting in a change in toxicity instead of its increase or decrease.

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