Size-dependent dynamics and tissue-specific distribution of nano-plastics in Danio rerio: Accumulation and depuration

Nano-plastics (NPs), defined as particles smaller than 1 µm, have emerged as a significant environmental contaminant due to their potential ecological impacts. This study explores the size-dependent dynamics and tissue-specific distribution of polystyrene nano-plastics (PS-NPs) in Danio rerio exposed to PS-NPs at an environmentally relevant concentration of 1 μg/mL for 28 days, followed by a 17-day depuration period. PS-NPs of 20, 100, 200, and 500 nm were assessed in the intestine, liver, gills, muscle, and brain using transmission electron microscopy (TEM) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). Smaller PS-NPs (20 nm) showed the highest accumulation in the intestine, followed by the liver, and gills, due to their greater surface area and cellular penetration. In contrast, larger PS-NPs (500 nm) exhibited lower accumulation and clearance rates, especially in the brain, suggesting restricted passage through biological barriers. The intestine consistently had the highest concentrations in both accumulation and depuration, while the brain maintained the lowest across all nanoparticle sizes. During depuration, smaller particles cleared more quickly, whereas larger particles persisted. This study highlights the tissue-specific distribution and retention patterns of PS-NPs in D. rerio, providing insights into nanoparticle behavior in aquatic organisms and the need for long-term size-specific environmental risk assessments.