Investigation of thiolysis of NBD amines for the development of H₂S probes and evaluating the stability of NBD dyes

In order to evaluate the thiolysis of NBD (7-nitro-1,2,3-benzoxadiazole) amines for development of H₂S probes, herein we investigated the reactivity and selectivity of a series of NBD amines for the first time. The piperazinyl- and piperidyl-based NBD probes could react efficiently with micromolar H₂S in buffer (pH 7.4), while such NBD(S) (nitrobenzothiadiazole) derivatives showed much slow thiolysis even in the presence of millimolar H₂S. Low reactivity was also observed for thiolysis of these ethylamino-, ethanolamino- and anilino-based NBD probes. Therefore, almost all NBD amines used in bioimaging should be stable, in consideration of the presence of only micromolar endogenous H₂S in vivo. Moreover, the piperazinyl-NBD derivatives could be efficient in the development of fluorescent H₂S probes and for directly visualizing H₂S by paper-based detection.