FHZ is a fluorescent probe (IUPAC: 2-(7-hydroxy-3H-phenoxazin-3-one-10-yl)benzoic acid), widely utilized in biological imaging due to its high sensitivity and selectivity in detecting specific molecular targets within cellular environments, exhibiting optimal excitation and emission spectra for various fluorescence microscopy applications.

Upon being incorporated with the probe FHZ and sequentially treated with HClO and the H2O2/EDTA-Fe2+ system, HeLa cells exhibit intense fluorescence in both cyan and green channels. FHZ is capable of emitting two distinct fluorescent signals upon exposure to ?OH and HClO, enabling the simultaneous differentiation of these species through a dual-channel detection approach leveraging two excitation wavelengths. The probe demonstrates remarkable specificity for ?OH and HClO detection, utilizing excitations at 410 nm and 490 nm, respectively. Moreover, FHZ efficiently penetrates cellular mitochondria, allowing for distinct and visual differentiation of endogenous ?OH and HClO via dual fluorescent signals[1].

Probe FHZ quickly enters the bloodstream through the zebrafish intestine, distributing uniformly across all zebrafish tissues. It maintains its stability in the blood, organs, and tissues in the absence of ROS, ensuring its integrity in biological environments. Notably, it selectively interacts with ·OH and HClO species[1], demonstrating its specificity and reactive capabilities under precise conditions.