AIE-labeled fluorescent polystyrene nanoplastics for quantitative analysis in macrophages uptake

Nanoplastics have attracted significant attention due to their harmful effects on the environment and organisms. However, accurately detecting and quantifying nanoplastics that are ingested by organisms poses a challenge. Conventional organic fluorescent-labeled nanoplastics have reduced labeling efficiency due to aggregation-caused quenching (ACQ), leading to artifacts caused by leakage of fluorescent molecules. To address these limitations, this study utilized AIE fluorescence for internally labeling polystyrene nanoparticles. AIE-active molecules do not emit fluorescence in dilute solutions, thus preventing accuracy issues associated with fluorescence leakage. Three model plastics (TPE@PS) of varying particle sizes were synthesized via the swelling method. The preparation parameters were optimized, followed by stability tests conducted on TPE@PS. Fluorescence microscopy imaging revealed significant uptake of TPE@PS by RAW246.7 cells. A successful standard curve of fluorescence intensity-concentration was established successfully and utilized to accurately quantify the amount of TPE@PS that was ingested by RAW246.7 cells. The results indicate a consistent increase with increasing concentration in TPE@PS uptake across all particle sizes during the fixed exposure duration of 48 h. Furthermore, RAW264.7 cells exhibited a higher propensity to uptake smaller TPE@PS particles. Flow cytometry was also employed to validated the suitability of TPE@PS as a model nanoplastic for tracing purposes.