γ–Glutamyltransferase (GGT) is a peptidase that maintains the intracellular glutathione levels and it is associated with several diseases like cancer, myocardial dysfunction etc. For reliable analysis and deep tissue imaging of biological samples, it is necessary to develop a ratiometric two-photon GGT probe. In this context, we have developed a benzocoumarin based two-photon ratiometric probe that can discriminate the cancer cells over normal cells. Also, this probe is featured with unperturbed signal toward pH, viscosity and polarity changes, offering an unbiased system for GGT analysis. However, the limitation of such probe is the lack of membrane-localizing ability. We attempted to develop another probe with membrane-localizing ability, maintaining two-photon and ratiometric imaging features. For that purpose, a long alkyl chain attached naphthalene hemicyanine based probe was developed. Using the probe we observed higher GGT activity in tumor tissue in comparison to normal tissue. In healthy mice, GGT activity was highest in the kidney, however, in the case of the tumor xenograft model GGT level was elevated in the colon, lung, and liver. The membrane-bound probe will find practical utility in investigating GGT associated biological processes in cells and tissues by two-photon ratiometric imaging.

Two-photon fluorescent probes for ratiometric imaging of γ–glutamyl transferase

ACS Spring 2022

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