Ratiometric Visualization of NO/HS Cross-Talk in Living Cells and Tissues Using a Nitroxyl-Responsive Two-Photon Fluorescence Probe.

It is of scientific significance to explore the intricate relationship between two crucial gasotransmitters nitric oxide (NO) and hydrogen sulfide (HS) because they exert similar and interdependent biological actions within the living organisms. Nevertheless, visualization of the NO/HS crosstalk using effective molecular imaging tools remains challenging. To address this issue, and given that nitroxyl (HNO) has been implicated as the interdependent production of NO and HS via a network of cascading chemical reactions, we herein design a ratiometric two-photon fluorescent probe for HNO, termed TP-Rho-HNO, which consists of benzo[h]chromene-rhodol scaffold as two-photon energy transfer cassette with phosphine moiety as specific HNO recognition unit. The newly proposed probe has been successfully applied in ratiometric two-photon bioimaging of endogenous HNO derived from NO and HS interaction in the human umbilical vein cells (HUVECs) and as well as in rat brain tissues. Intriguingly, the imaging results consistently demonstrate that the mutually dependent upgeneration of HS and NO are present in living biosystems, indicating that this molecular probe would provide a powerful approach to elucidate the chemical foundation for the anfractuous cross-talk between the NO and HS signaling pathways in biology.