Arylphosphonate-Tethered Porphyrins: Fluorescence Silencing Speaks a Metal Language in Living Enterocytes*

Metal-Free Aminophosphonation: Eco-Friendly Synthesis and Photophysical Properties of Fluorescent 3-(Aminoimidazo[1,2-a]Pyridin-2-yl)Phosphonates

We report a novel, metal-free procedure for the direct aminophosphonation of imidazo[1,2-a]pyridines in green solvents under open air conditions. This method is characterized by its mild and sustainable conditions, ease of operation, scalability, and excellent functional group compatibility. The synthesized compounds exhibit promising photophysical properties, including significant Stokes shifts and quantum yields, making them potential candidates for innovative fluorescent probes.

A 2,7-dichlorofluorescein derivative to monitor microcalcifications

Herein, we report the crystal structure of 2,7-dichlorofluorescein methyl ester (DCF-ME) and its fluorescence response to hydroxyapatite binding. The reported fluorophore is very selective for staining the bone matrix and provides turn-on fluorescence upon hydroxyapatite binding. The reported fluorophore can readily pass the cell membrane of the C2C12 cell line, and it is non-toxic for the cell line. The reported fluorophore DCF-ME may find applications in monitoring bone remodeling and microcalcification as an early diagnosis tool for breast cancer and age-related macular degeneration.

Arylphosphonate-Tethered Porphyrins: Fluorescence Silencing Speaks a Metal Language in Living Enterocytes*

We report the application of a highly versatile and engineerable novel sensor platform to monitor biologically significant and toxic metal ions in live human Caco-2 enterocytes. The extended conjugation between the fluorescent porphyrin core and metal ions through aromatic phenylphosphonic acid tethers generates a unique turn off and turn on fluorescence and, in addition, shifts in absorption and emission spectra for zinc, cobalt, cadmium and mercury. The reported fluorescent probes p-H8 TPPA and m-H8 TPPA can monitor a wide range of metal ion concentrations via fluorescence titration and also via fluorescence decay curves. Cu- and Zn-induced turn off fluorescence can be differentially reversed by the addition of common chelators. Both p-H8 TPPA and m-H8 TPPA readily pass the mammalian cellular membrane due to their amphipathic character as confirmed by confocal microscopic imaging of living enterocytes.