Dipeptidyl Peptidase IV Activated Near-Infrared Fluorescent Probe for Visually Evaluating Diabetes Models under Microplastic Exposure.

The health of patients with type 2 diabetes mellitus (T2DM) may be adversely affected by microplastics (MPs) that are present in the environment. However, most toxicity studies of MPs are conducted on healthy models, which may not accurately reflect the exposure risks for diabetic individuals. Dipeptidyl peptidase IV (DPP4/CD26) is a multifunctional transmembrane glycoprotein with a broad spectrum of biological functions, and its abnormal activity is intimately associated with the development of T2DM. Therefore, noninvasive detection techniques for DPP4 have wide-ranging applications in disease diagnosis and MPs toxicity research. Here, we developed an enzyme-activatable near-infrared fluorescent probe, Cy-DPP, to monitor DPP4 activity in cells and mice exposed to MPs. Using this probe, we detected changes in DPP4 levels in healthy model mice and T2DM mouse models after exposure to MPs, respectively. Our results revealed a differential upregulation of DPP4, with varying degrees of increase observed between T2DM cells and mouse models. This study not only offers a new approach for the early diagnosis of T2DM but also highlights the significant impact of MPs on the diabetic condition.