SERS imaging and ICP-MS quantification of the biological uptake of nanoplastics using a dual-detectable model nanomaterial

Nanoplastics (NPs) pose significant concerns to human health due to their wide environmental presence and high potential for biological uptake, transport, and accumulation. Conventional analytical methods for studying NP-biota interactions suffer from low accuracy and precision due to limited reliability and quantitative capability. To address these challenges, a dual-detectable NP material was developed that allows for in-situ imaging by surface-enhanced Raman spectroscopy (SERS) and ex-situ quantification by inductively coupled plasma-mass spectrometry (ICP-MS). Here, a model NP that has a core-shell structure with Raman reporter-functionalized gold nanoparticles as the core and a layer of plastic as the shell was synthesized. The model polystyrene (PS) NPs demonstrated stability in structure, morphology, size, and surface charge over one year, with no indication of constituent leaching because of the covalent bonding of the Raman indicator to the Au core, ensuring stable signals and enabling reliable long-term monitoring in complex biological systems. The model NPs remained stable in suspension over 24 h without observable precipitation. A single model NP was successfully detected by SERS, indicating the single-particle detection capability of this approach. Further, garlic (Allium sativum) was used as a biological model to evaluate the potential of using the dual-mode detectable model NPs to study NP-biota interactions. Garlic roots exposed to PS NPs for 30 days at 2 × 10⁹ and 2 × 10 ¹⁰ particles/mL accumulated average particle counts of 1.9 × 10⁷ and 2.3 × 10⁸ particles per plant, respectively. At the highest tested concentration (2 ×10 ¹¹ particles/mL), uptake increased to 2.4 × 10⁹ particles per plant as quantified in root tissues. These results confirm a concentration-dependent uptake pattern. NP uptake by garlic roots further increased under longer exposure periods. ICP-MS quantification confirmed the presence of model NPs in roots rather than in the upper parts of the plant, as well as the concentration-dependent accumulation. This dual-mode detectable model NPs enable both semi-quantitative NP visualization via SERS imaging and accurate quantification analysis through ICP-MS, serving as a powerful tool for studying the biological uptake, transport, and accumulation of NPs. Their use can significantly improve our understanding of their fate and effects on biota in the future.