Abstract
Near-infrared (NIR) fluorescent molecules are of great importance for the visualisation of biological processes. Among the most promising dye scaffolds for this purpose are P Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> O-substituted phospha-xanthene (POX) dyes, which show NIR emission with high photostability. Their practical utility for in vitro and in vivo imaging has recently been demonstrated. Although classical modification methods have been used to produce POX-based fluorescent probes, it is still a challenge to introduce additional functional groups to control the localisation of the probe in cells. Herein, we report on the development of POXs that bear a 4-ethynylphenyl group on the phosphorus atom. These dyes can subsequently be functionalised with azide-tagged biomolecules via a late-stage Cu-catalysed azide/alkyne cycloaddition (CuAAC) reaction, thus achieving target-selective labelling. To demonstrate the practical utility of the functionalised POXs, we designed a sophisticated NIR probe that exhibits a bell-shaped off–on–off pH-response and is able to assess the degree of endosomal maturation.
Highlights
IntroductionPhospha-xanthene dyes have been used as NIR-labelling reagents in both in vitro and in vivo optical imaging.[22,27,29] following molecular design strategies that have been established for classical xanthene dyes, several phospha-xanthene-based NIR uorescent probes for the detection of H2O2,30 Cu+,31 Ca2+,32,33 pH changes,[34] and membrane potentials[35] have been reported
The visualisation of speci c cellular events at an organelle level can provide valuable information that aids in the understanding of complicated biological systems
To demonstrate the practical utility of the functionalised POXs, we designed a sophisticated NIR probe that exhibits a bell-shaped off–on–off pHresponse and is able to assess the degree of endosomal maturation
Summary
Phospha-xanthene dyes have been used as NIR-labelling reagents in both in vitro and in vivo optical imaging.[22,27,29] following molecular design strategies that have been established for classical xanthene dyes, several phospha-xanthene-based NIR uorescent probes for the detection of H2O2,30 Cu+,31 Ca2+,32,33 pH changes,[34] and membrane potentials[35] have been reported In this context, we have successfully developed a series of >P(]O) Ph-substituted dyes, POXs (Fig. 1a), including phospha uoresceins (POFs),[20] phospha-rhodols (PORLs),[21] and phospha-rhodamines (PORs).[22,23] These POXs exhibit high brightness with absorption and emission maxima (labs/lem) at 7902 | Chem. As a showcase of the practical utility of this probe, we have successfully visualised the luminal pH heterogeneity during endosome maturation in living cells
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