Gold-labelled nanoplastics models: Synthesis, detection, and quantification by SP-ICP-MS in Daphnia magna

The detection and quantification of nanoplastics (NPLs) in complex matrices remain a major analytical challenge. In this study, gold-labelled NPLs consisting of a gold nanoparticle core covered by a polystyrene (PS) shell were designed, enabling sensitive quantification by single-particle inductively coupled plasma mass spectrometry (SP-ICP-MS). Optimized conditions yielded NPLs containing one single gold nanoparticle per NPL and exhibiting surface functionalization. These NPLs fulfill key criteria for realistic NPLs models, combining: the use of an environmentally relevant polymer (PS), the exact control over their chemical composition, a density comparable to that of native PS particles despite gold-labelling, and a strong traceability. The strategy applied here demonstrates unprecedented sensitivity, with a limit of detection of 2.8 × 10⁵ NPL L⁻¹ (0.21 ng of NPLs), enabling detection of environmentally realistic concentrations. The method validation performed with NPLs-spiked Daphnia magna achieved recovery rates close to 100%. Exposure experiments revealed a dose-dependent increase in the body burden of NPLs, up to 8.5 × 10⁵ particles/daphnid (64 ng of NPLs) after 48 h. This study combines gold-labelling, precise chemical control, and environmental relevance to enable accurate NPLs quantification in organisms at low, realistic concentrations, paving the way for robust ecotoxicological assessments.