Quantitative Tracking of Nanoplastic Uptake and Distribution in Zebrafish by Single-Particle Inductively Coupled Plasma Mass Spectrometry

Tracking the uptake, distribution, and accumulation of nanoplastics (NPs) in biological organisms is important to understand their fate and effects but remains a major challenge. Herein, a novel framework was proposed for quantitatively tracking of NP fate in zebrafish at single-particle level by employing polystyrene NPs (PS NPs) doped with the europium chelate as the spiking material and using the single-particle inductively coupled plasma-mass spectrometry (sp-ICP-MS) technique. To ensure the sp-ICP-MS analysis, a critical pretreatment method was developed based on tetramethylammonium hydroxide (TMAH) digestion, allowing for the extraction of NPs from zebrafish tissues with a recovery rate ranging from 89.4% to 104.2% under optimal conditions. Benefiting from this method, it is found that though it mainly accumulated in the intestine (81.3-93.3%), NPs can further continuously penetrate into internal organs (3.3-13.6%) with a maximal concentration of 1.14 × 10⁵ particles/mg and a maximal bioconcentration factor (BCF) of 5.5. More importantly, NPs were detected in the brain with a concentration of 2.14 × 10⁴ particles/mg at day 7, demonstrating that it is able to cross the blood-brain barrier. On the contrary, NPs have been found to hardly penetrate into eggs due to the barrier function of the chorion. Furthermore, a similar evidence and conclusion were obtained by confocal laser scanning microscopy (CLSM) characterization. We hope that this work can provide a new paradigm for investigating the fate of trace NPs in organisms even in different environmental scenarios.