An AIE-active NIR Ratiometric probe based on “ICT + ESIPT” mechanism for mitochondrial MAO imaging: Distinguishing cells and visualizing DILI

A novel AIE-1 probe integrates “ICT + ESIPT+AIE” tri-modal for ratiometric NIR fluorescence imaging of MAO activity. • AIE-1 exhibits wide linear range (0–140 μg/mL), high sensitivity (LOD 0.23 μg/mL), and excellent selectivity. • AIE-1 semi-quantitatively distinguishes MAO activity in normal/cancer cells and evaluates cellular inhibitor efficacy. • Successful real-time visualization of upregulated MAO activity is achieved in a DILI model. Given the crucial role of monoamine oxidase (MAO) in maintaining amine homeostasis and liver pathology, real-time in situ monitoring of its activity is crucial for elucidating the mechanism of drug-induced liver injury (DILI). This study designed and synthesized a ratio type fluorescent probe AIE-1 based on the “ICT + ESIPT” mechanism, which integrates aggregation induced luminescence (AIE), near-infrared (NIR) emission, and mitochondrial targeting. The probe AIE-1 utilizes MAO catalyzed oxidative deamination reaction to trigger intramolecular charge transfer and excited state proton transfer processes, producing significant ratiometric fluorescence signals at 518 nm and 712 nm. The sensing mechanism was thoroughly validated by 1 H NMR titration, DFT calculations of HOMO-LUMO energy gaps, and solvent-polarity-dependent experiments, collectively confirming the occurrence of both ICT and ESIPT processes. Spectral experiments show that its detection of MAO has a wide linear range (0–140 μg/mL), high sensitivity (0.23 μg/mL), strong selectivity, and anti-interference ability. Cell imaging experiments have confirmed that AIE-1 can successfully semi quantitatively distinguish the differences in MAOs activity between normal liver cells and liver cancer cells, and evaluate the effectiveness of inhibitors. In the drug-induced liver injury model, AIE-1 successfully achieved real-time visualization monitoring of upregulation of MAO activity in vivo with sensitivity and specificity. This probe provides a novel and efficient tool for studying the role of MAO in pathological processes such as DILI.