A two-photon off-on fluorescence probe for imaging thiols in live cells and tissues.
A two-photon (TP) fluorescence imaging probe (Z1) was designed to detect biothiols through a photoinduced electron transfer pathway utilizing N-butyl-naphthalimide as the fluorophore and 2,4-dinitrobenzene-sulfonyl as the responsive group, which were linked together by piperazine. The synthesized Z1 displayed high selectivity to biothiols, significant fluorescence off-on properties, and a marked two-photon absorption cross section (δ = 110 GM). Moreover, Z1 showed good biocompatibility and insensitivity toward changes in the biologically relevant pH range (7.2-8.4), which enabled the utilization of Z1 to monitor biothiol levels not only in live cells but also in tissues at depths of 50-250 μm.