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

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 via

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-H8TPPA and m-H8TPPA 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-H8TPPA and m-H8TPPA readily pass the

mammalian cellular membrane due to their amphipathic character as

confirmed by confocal microscopic imaging of living enterocytes.