Mitochondria-immobilized fluorescent probe to reveal the crucial roles of peroxynitrite during the cellular resistance to hydrazine.

The resistance response of cells to xenobiotics is an important topic in the field of life sciences. Reactive oxygen species are expected to play a crucial role in resisting reductive toxicants. However, the function of ONOO-, a highly reactive oxygen species (ROS), in cellular defense against hydrazine invasion remains unclear, primarily owing to the deficiency of appropriate molecular tools. To address this issue, in this work, we developed a fluorescent probe capable of distinguishing ONOO- and hydrazine in ratiometric manner. This probe exhibited deep-red fluorescence. Upon reaction with hydrazine, it forms an electronic structure with a strong donor-weak acceptor configuration, resulting in blue fluorescence due to a weak intramolecular charge transfer (ICT) effect. Conversely, when the probe reacted with ONOO-, it generated an electronic structure with a strong donor-strong acceptor configuration, leading to green fluorescence as a result of the strong ICT effect. Generally, ONOO- is produced within mitochondria and exhibits a short lifespan in cells. Therefore, we designed the probe to be mitochondria-targeted and immobilized, thereby enhancing its detection efficiency for intracellular ONOO-. Using this probe, we demonstrated at both cellular and in vivo levels that cells generate substantial amounts of ONOO- to counteract hydrazine invasion.