Long-Wavelength Emitting Fluorescent Probe for Real-Time Peroxynitrite Imaging in Living Cells.

Peroxynitrite (ONOO), a highly reactive nitrogen species with potent oxidative capacity, plays dual roles in cellular signaling and disease pathogenesis. To address the limitations of existing ONOO probes-particularly poor aqueous solubility and inadequate emission wavelengths-we developed P, a novel water-soluble fluorescent probe based on a rigid molecular scaffolding. P selectively detects ONOO through azo-bond oxygenolysis, triggering rapid (< 10 s), sensitive (LOD = 0.38 µM), and long-wavelength fluorescence emission (λ = 612 nm). Crucially, P enables real-time visualization of both exogenous and endogenous ONOO in live cells, demonstrating its utility for interrogating ONOO dynamics in biological systems. These attributes position P as a robust tool for studying ONOO-associated pathophysiological processes.