We have developed a new class of two-photon absorbing dyes that are far-red emitting, water-soluble, and very bright inside cells as well as in tissue. The significant autofluorescence from yellow wavelength region in tissue imaging can be addressed by deep-red emitting dyes.
A fluorescent probe that enables ratiometric imaging of endogenous hypochlorous acid (HOCl) in cells and tissues by two-photon microscopy is developed based on a red-emitting acetyl-benzocoumarin (AcBC) dye. An oxathiolane group in the probe reacts with HOCl to generate the AcBC dye, which involves a ratiometric fluorescence change only toward HOCl along with high sensitivity.
γ-Glutamyl
transpeptidase (GGT), a cell surface-bound protease,
is associated with various diseases including cancer. The detection
of the enzyme activity is an important subject, leading to about 40
activatable fluorescent probes so far. All of them, however, lack
the membrane-localizing ability, raising a reliability issue in the
quantitative analysis. Disclosed is the first fluorescent probe that
senses the cell surface-bound enzyme, which, furthermore, is capable
of ratiometric as well as two-photon imaging with desirable features.
Ratiometric imaging of cancer cell lines reveals a 6.4–8.4-fold
higher GGT levels than those in normal cell lines. A comparison of
the enzyme activity in organ tissues of normal and tumor xenograft
mice reveals notably different levels of enzyme activity depending
on the kind of tissue. Normal tissues exhibited comparable levels
of enzyme activity, except the kidney that has significantly higher
GGT activity (2.7–4.0-fold) than the other organs. Compared
with the normal tissues, considerably higher enzyme activity was observed
in the tumor tissues of the thigh (4.0-fold), colon (2.5-fold), lung
(3.6-fold), and liver (2.1-fold), but essentially no enhanced activity
in the tumor tissues of the spleen, stomach, and pancreas and a comparable
level in both the tumor and normal kidney tissues were observed. The
probe offers practical means for studying GGT-associated biology in
cells and tissues by one- as well as two-photon ratiometric imaging.
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