Can the sonication of polystyrene nanoparticles alter the acute toxicity and swimming behavior results for Daphnia magna?

The seemingly ubiquitous presence of plastic debris led to a greater focus on micro- and nanoplastics research derived from the degradation process of macroplastics. The ingestion and consequent accumulation of plastics on the biota are the main concerns. Researchers strive to make assay conditions as close as possible to those of the environment. In this regard, sonication can be applied to de-agglomerate the plastic particles, but this may alter significantly their toxicity. The aim of this study was to understand the effects of the sonication process on the acute toxicity and swimming behavior of polystyrene nanoparticles using Daphnia magna as the test organism. The results show a 2-fold reduction in the acute toxicity after the sonication process; the EC50 of the PSNP-NS was 1.28 ± 0.17 mmol while for PSNP-S the EC50 was 2.77 ± 0.32 mmol, possibly through the formation of an eco-corona on the nanoplastic surface, formed from the ions dispersed in the medium or proteins secreted by the test organisms. The mean swimming distance was reduced when compared to the control group for both the PSNP-S and PSNP-NS. This is the first research stating the toxicological differences between sonicated and non-sonicated polystyrene nanoparticle samples using Daphnia magna as test organism.