A highly sensitive near-infrared ratiometric fluorescent probe for imaging of mitochondrial hydrazine in cells and in mice models

Hydrazine (N2H4) has been listed as a possible human carcinogen. It can cause severe damage to various organs through respiratory tract, skin and digestive tract. Although some fluorescent probes have been developed for imaging of N2H4, there is very few entry of application in vivo, probably limited by the short fluorescence emission wavelengths. Moreover, the sensitivity also needs to be improved to meet the requirement of detection in vivo. Hence, we design and synthesize a new NIR ratiometric fluorescent probe Cy-OAc based on cyanine derivatives for the sensitive detection of N2H4 in cells and in mice models. Cy-OAc consists of a large pi-conjugated system and a masking unit for both regulating the pi-system and tracing N2H4. Cy-OAc holds the emission profile centered at 825 nm under the excitation of 730 nm, and upon reaction with N2H4, it shifts the emission profile centered at 662 nm with an excitation at 540 nm, resulting in the NIR ratiometric emission response, as well as a distinct color change that can be distinguished by the naked eye. Cy-OAc has been successfully applied to imaging the N2H4 in apoptotic cells. The results reveal that N2H4 can lead to the apoptosis of HeLa cells via the damage of mitochondrial membrane potential. Taking advantage of the NIR emissions, Cy-OAc exhibits the deep tissue penetration of 700 mu m in kidney tissue. Our probe Cy-OAc is further utilized to visually detect N(2)H(4-)metabolism and estimate kidney damage in mice models. We envision that the probe Cy-OAc can be an attractive chemical tool for exploring N2H4 in bio-specimen.