Tracking the dynamic change of mitochondrial viscosity in ferroptosis via a NIR fluorescent probe

Abstract

Ferroptosis is a regulated cell-death pathway that is tightly linked to mitochondrial impairment. Consequently, tracking variations in intramitochondrial viscosity is important for the early identification of ferroptosis-related disorders. Here, we develop a mitochondria-localized near-infrared fluorescent probe ( Mito-VF ), enabling in situ reporting of viscosity changes throughout ferroptosis. Mito-VF is constructed on a donor–π–acceptor (D-π-A) architecture, incorporating a thiophene–aminothiazole electron donor and a quinolinium acceptor. Owing to a twisted intramolecular charge transfer (TICT) process, the NIR emission responds of probe Mito-VF sensitively to the viscosity of the local environment. Furthermore, the probe exhibits a distinct Stokes shift and effective mitochondrial targeting, enabling high-contrast fluorescence imaging in cells. Using live-cell microscopy, we captured a progressive elevation of mitochondrial viscosity in an erastin-triggered ferroptosis model. As ferroptosis progressed, the fluorescence signals increased in a time- and concentration-dependent trend. Importantly, administration of ferrostatin-1 reversed the viscosity-associated signal, indicating that ferroptosis can be mitigated alongside the recovery of mitochondrial viscosity. Copyright © 2026. Published by Elsevier B.V.