Cellular uptake of polystyrene nanoplastics with surface Functionalization: An AIE-based quantitative approach

The increasing prevalence of nanoplastics (NPs) in the environment has raised significant concerns about their potential for bioaccumulation and toxicity. However, most toxicity studies currently focus on pristine polystyrene NPs (PSNPs), overlooking the impact of environmental weathering on their surface chemistry and interactions with biological systems. This study adopts an aggregation-induced emission (AIE)-based approach to quantify how surface functionalization affects cellular uptake, a critical step in assessing NPs toxicity. We synthesized carboxyl (-COOH) and amino (-NH 2 ) functionalized PSNPs through emulsion polymerization, incorporating an AIE fluorescent label to enable precise quantification and to distinguish the NPs from endogenous biomolecules. Using mouse macrophages (RAW264.7) as a model, we demonstrated that surface carboxylation significantly enhanced cellular uptake compared to the original NPs. This enhanced uptake effect is likely due to the increased interaction between the functionalized NPs and the cell surface receptors. Quantitative fluorescence analysis and flow cytometry revealed that PSNP-COOH exhibited the highest uptake and the most pronounced effects on cell toxicity. This AIE-based approach offers a more environmentally relevant model for evaluating NPs toxicity, understanding the importance of considering surface modifications when assessing the biological effects of NP exposure.