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

Abstract

<p>We report the application of a highly versatile and</p> <p>engineerable novel sensor platform to monitor biologically significant</p> <p>and toxic metal ions in live human Caco-2 enterocytes. The extended</p> <p>conjugation between the fluorescent porphyrin core and metal ions via</p> <p>aromatic phenylphosphonic acid tethers generates a unique turn off</p> <p>and turn on fluorescence and, in addition, shifts in absorption and</p> <p>emission spectra for zinc, cobalt, cadmium and mercury. The reported</p> <p>fluorescent probes p-H8TPPA and m-H8TPPA can monitor a wide</p> <p>range of metal ion concentrations via fluorescence titration and also</p> <p>via fluorescence decay curves. Cu and Zn-induced turn off</p> <p>fluorescence can be differentially reversed by the addition of common</p> <p>chelators. Both p-H8TPPA and m-H8TPPA readily pass the</p> <p>mammalian cellular membrane due to their amphipathic character as</p> <p>confirmed by confocal microscopic imaging of living enterocytes.</p>