A PTCA LabelingMethod for Direct LDI-MSI of PolystyreneNanospheres

Abstract Micro/nanoplastics are widely detected in environmental and biological systems. However, methods for their direct mass spectrometric detection in vivo remain underdeveloped, limiting the simultaneous analysis of their tissue distribution and associated metabolic responses. In this study, we developed a perylene-3,4,9,10-tetracarboxylic acid (PTCA)-labeling strategy for polystyrene (PS) nanospheres and established a direct laser desorption/ionization mass spectrometry imaging (LDI-MSI) approach for in vivo tracking. On the same tissue section, PS–PTCA was first imaged by LDI-MSI, followed by matrix application to obtain complementary metabolomic information. In an intravenous model, PS–PTCA showed lung-dominant distribution and time-dependent metabolic responses, with acute purine perturbation followed by shifts in amino acid and nitrogen metabolism. Under an inhalation-relevant exposure setting established by intratracheal instillation, PS–PTCA was confined to the lungs and persisted for weeks, accompanied by sustained metabolic alterations. This work provides a practical MSI framework for directly mapping in vivo PS biodistribution, together with associated metabolic responses.