A highly selective NIR ratiometric fluorescent probe for in situ detection of metabolized hydrazine in living cells

Hydrazine (N2H4) is a great concern to human health and its detection in living cells is of growing importance. In this report, we employed a hydrogen bonding-anchored sensing strategy to develop a near-infrared (NIR) fluorescent probe CDM-1, which is capable of detecting N2H4 with ratiometric and colorimetric responses. The introduction of a chloro-substitution to the dicyanoisophorone scaffold improved the stability of the probe through Cl...C--O n & RARR;& pi; * interactions. Meanwhile, this substitution also provided a lower pKa value of the phenol CDM, allowing the generation of ratiometric changes after CDM-1 reacted with N2H4 under physiological conditions (pH = 7.4). Notably, we took advantage of utilizing both the hydrogen-bonding interaction and the 6-exo addition to target two anchors on N2H4 through "N" and "H" atoms, which enabled high selectivity and reactivity with a low limit of detection value at 0.3 ppb. CDM-1 has been successfully loaded onto paper strips to detect N2H4 vapor. Furthermore, the probe demonstrated its potential biological value in monitoring both the exogenous and endogenous N2H4, particularly as a metabolite of the anti-tuberculosis drug, Isoniazid (INH), in living cells.