Size-dependent cellular fate of polystyrene particles in human fibroblasts: a label-free Raman imaging study

Micro- and nanoplastics persist in the environment and may affect human health, yet their cellular interactions remain poorly understood. Here, we demonstrate label-free Raman imaging to investigate size-dependent interactions of polystyrene particles (0.1 μm, 1.1 μm, and 3.0 μm) with human fibroblast MSU-1.1 cells. Spatially resolved Raman mapping tracked intracellular localization at 10.00 μg/ml, while WST-1 assays assessed viability across 3.13-150.00 μg/ml. Raman imaging revealed distinct size-dependent cellular distribution patterns. Nanoplastics (0.1 μm) were efficiently internalized, showing diffuse cytoplasmic Raman signal distribution. Intermediate microparticles (1.1 μm) showed partial internalization with clustered signals, indicating vesicular uptake. Larger microspheres (3.0 μm) remained primarily extracellular, forming surface agglomerates. Despite extensive cellular uptake, no statistically significant cytotoxic effects were observed for any particle size, consistent with increased resistance of this immortalized cell line to pristine microplastic exposure. This study establishes Raman imaging as a powerful tool for direct, chemically specific detection and spatial mapping of plastic-cell interactions. The findings demonstrate that cellular localization patterns do not necessarily predict cytotoxic outcomes, emphasizing the importance of considering both particle distribution and cell-type specific responses in microplastic research.