Dating photochrom

Development of powerful fluorescence imaging probes and techniques sets the basis for the spatiotemporal tracking of cells at different physiological and pathological stages.

While current imaging approaches rely on passive probe–analyte interactions, here we develop photochromic fluorescent glycoprobes capable of remote light-controlled intracellular target recognition.

Considering their nucleophilic nature, Michael addition of sulfite to the hemicyanine moiety of MR-Gal may break the π-conjugation, thereby changing the optical properties of the probe.

The fluorophore (naphthalimide) was coupled with D-galactose to target a specific transmembrane glycoprotein receptor, by a click reaction.

The control compound (SP-PEG) was synthesized in a similar way. After irradiation with UV light (365 nm), a gradually enhanced absorbance peak of SP-Gal at 535 nm was observed, characteristic of the formation of the MR-Gal isomer (Fig. The peak remained unchanged after 7 min of irradiation, suggesting that the probe reached a photostationary state.

Conjugation between a fluorophore and spiropyran produces the photochromic probe, which is subsequently equipped with a glycoligand “antenna” to actively localize a target cell expressing a selective receptor.

We demonstrate that the amphiphilic glycoprobes that form micelles in water can selectively enter the target cell to operate photochromic cycling as controlled by alternate UV/Vis irradiations.

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