Multifunctional Fluorescent Probe for Simultaneous Detection of ONOO–, Viscosity, and Polarity and Its Application in Ferroptosis and Cancer Models

Intracellular peroxynitrite anions (ONOO^-) and microenvironments (such as viscosity and polarity) play an important role in maintaining redox homeostasis, regulating diffusion, transportation, and signal transduction in living cells. The abnormality of these factors is often closely related to various physiological/pathological processes. However, owing to the lack of suitable probes, the simultaneous visualization of ONOO^-, viscosity, and polarity in ferroptosis and cancer models has not been achieved. To meet urgent needs, we presented a multifunctional near-infrared (NIR) fluorescent probe, named MQA-P, for simultaneously detecting ONOO^-, viscosity, and polarity within mitochondria. The probe exhibited a remarkable turn-on response to ONOO^- with the far-red emission of about 645 nm and was highly sensitive to viscosity/polarity in the NIR channel with λ_em > 704 nm. Facilitated by MQA-P, for the first time, we revealed that erastin-induced ferroptosis was accompanied by a significant upregulation of ONOO^- and an increase of viscosity (or decrease of polarity) at the same time. Moreover, the concurrent use of ONOO^-, viscosity, and polarity for the diagnosis of cancer has been successfully achieved not only at cell/tissue levels but also in tumor mice models. Compared with detecting only one factor, this simultaneous detection of multimarkers provides a more sensitive and reliable method/tool for tracking ferroptosis-related pathological processes and cancer diagnosis, holding great potential in preclinical research, medical diagnosis, and imaging-guided surgery.