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Issue 3, 2008
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Soluble precipitable porphyrins for use in targeted molecular brachytherapy

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In a new therapy that aims to concentrate and immobilize therapeutic radionuclides in nanoscale assemblies within solid tumors, a soluble precipitable reagent (SPR) is administered as the radionuclide carrier and is converted to non-diffusible precipitate by an enzyme located in tumor tissues. To meet the objective of such an SPR, we have prepared and examined a class of porphyrin–alkyldiphosphates that are soluble in aqueous solution and that are rendered insoluble upon removal of the two phosphate groups. The porphyrins examined herein are of the trans-AB architecture wherein the substituents are a bis(dihydroxyphosphoryloxy)alkyl group and a phenyl (or p-bromophenyl) group. Provisions for later incorporation of radionuclides have been established by preparation of the analogous copper chelate or the meso-iodo free-base porphyrin. Altogether, four porphyrins bearing a bis(dihydroxyphosphoryloxy)alkyl group were examined and found to exhibit satisfactory solubility in water (>1 mM). Dephosphorylation reactions have been carried out in vitro using the enzyme shrimp alkaline phosphatase. In each case, enzyme-induced precipitation was observed. The soluble-to-insoluble conversion has been examined by visual inspection, absorption spectroscopy, electrospray ionization mass spectrometry, and nephelometry using non-radiolabeled porphyrins.

Graphical abstract: Soluble precipitable porphyrins for use in targeted molecular brachytherapy

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The article was received on 13 Sep 2007, accepted on 23 Oct 2007 and first published on 02 Nov 2007

Article type: Paper
DOI: 10.1039/B714127K
Citation: New J. Chem., 2008,32, 436-451
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    Soluble precipitable porphyrins for use in targeted molecular brachytherapy

    Z. Yao, K. E. Borbas and J. S. Lindsey, New J. Chem., 2008, 32, 436
    DOI: 10.1039/B714127K

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