Control strategy of displacement processes to sense biothiols via fluorescent changes

Two different bis-pyrene derivatives BP-1 and BP-2 were synthesized, which showed efficient fluorescent quenching by Cu²⁺. The addition of biothiols, such as GSH, Cys, and Hcy, restored their fluorescent emissions. Differences in the affinities of BP-1 and BP-2 for Cu²⁺ were successfully applied to the different detection limits and the linear detection range of biothiols. An NH moiety and a sulfur atom in the linker were the only differences between BP-1 and BP-2. Since BP-1 bound Cu²⁺ more tightly than BP-2, BP-1-Cu²⁺ required more GSH, Cys, and Hcy equivalents to restore the fluorescent emission. In contrast, only two equivalents of biothiols restored the original emission of BP-2-Cu²⁺. As a proof-of-concept, we demonstrated that molecular recognition chemistry and host-gest chemistry, more specifically the modulation of metal ion recognition, can be successfully applied to biothiol detection, especially over different concentration ranges. BP-1 showed a fluorescent quenching effect in living cells upon the addition of Cu²⁺ and BP-1-Cu²⁺ was also successfully applied to imaging biothiols in living cells.