Endoplasmic reticulum (ER)-targeted ratiometric fluorescent probe for visualization of ER-phagy induced by ONOO and NIR imaging in mice with drug-induced liver injury.

Drug-induced liver injury (DILI) remains a persistent and unavoidable challenge in biomedicine, significantly impacting preclinical drug development and early clinical trials. The liver, as the primary site for endogenous antioxidant production, is particularly sensitive to acute damage mediated by reactive oxygen species (ROS) and reactive nitrogen species (RNS). The ratiometric and near-infrared (NIR) detection of peroxynitrite (ONOO), as potential biomarker for DILI, is crucial for enhancing the imaging effectiveness of liver damage. Thus, an ONOO activated endoplasmic reticulum (ER)-targeted fluorescent probe, named DSA, was easily designed and synthesized using dicyanoisophorone, syringaldehyde and arylboronate, which featured dicyanoisophorone as the fluorophore and an arylboronate group as the ONOO recognition group. The probe DSA was converted into a long-wavelength DSA-ONOO fluorophore in the presence of ONOO with large Stokes shift (172 nm), high selectivity, and low detection limit (98 nM). The ratiometric response to ONOO provided a more accurate intracellular analysis through a built-in internal reference calibration, successfully enabling sensitive detection of ONOO in living cells. Additionally, leveraging the optical characteristics of NIR fluorescence imaging, DSA not only detected the ER-phagy process induced by starvation and ONOO but also accurately monitored minor fluctuations in ONOO levels during acetaminophen (APAP)-induced hepatotoxicity in mice, aiding in the diagnosis of DILI and the development of therapeutic drugs.