A general strategy to the intracellular sensing of glycosidases using AIE-based glycoclusters
Résumé
Glycosidases, which are the enzymes responsible for the removal of residual monosaccharides from
glycoconjugates, are involved in many different biological and pathological events. The ability to detect
sensitively the activity and spatiotemporal distribution of glycosidases in cells will provide useful tools for
disease diagnosis. However, the currently developed fluorogenic probes for glycosidases are generally
based on the glycosylation of the phenol group of a donor–acceptor type fluorogen. This molecular
scaffold has potential drawbacks in terms of substrate scope, sensitivity because of aggregation-caused
quenching (ACQ), and the inability for long-term cell tracking. Here, we developed glycoclusters
characterized by aggregation-induced emission (AIE) properties as a general platform for the sensing of
a variety of glycosidases. To overcome the low chemical reactivity associated with phenol glycosylation,
here we developed an AIE-based scaffold, which is composed of tetraphenylethylene conjugated with
dicyanomethylene-4H-pyran (TPE–DCM) with a red fluorescence emission. Subsequently, a pair of
dendritic linkages was introduced to both sides of the fluorophore, to which six copies of
monosaccharides (D-glucose, D-galactose or L-fucose) were introduced through azide–alkyne click
chemistry. The resulting AIE-active glycoclusters were shown to be capable of (1) fluorogenic sensing of
a diverse range of glycosidases including b-D-galactosidase, b-D-glucosidase and a-L-fucosidase through
the AIE mechanism, (2) fluorescence imaging of the endogenous glycosidase activities in healthy and
cancer cells, and during cell senescence, and (3) glycosidase-activated, long-term imaging of cells. The
present study provides a general strategy to the functional, in situ imaging of glycosidase activities
through the multivalent display of sugar epitopes of interest onto properly designed AIE-active fluorogens.
Domaines
Chimie
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