6-Fluoropyridoxal Polymer Conjugates:  Novel ¹⁹F pH Indicators for Magnetic Resonance Spectroscopy

Abstract

Fluorinated macromolecular probes (6-fluoropyridoxal-polymer conjugates) have been synthesized and characterized as potential pH indicators for magnetic resonance spectroscopy and imaging applications. The 19F pH sensor 2-fluoro-5-hydroxy-3-(hydroxymethyl)-6-methyl-4-pyridinecarboxal-+ ++dehyde (6-fluoropyridoxal; 2) has been conjugated to carrier molecules (polyamino dextran, polylysine, and albumin) by reductive alkylation for enhanced vascular retention and tissue targeting. The pH indicator polymer conjugates were purified by exhaustive dialysis and isolated in good yields (66-84%). The 6-fluoropyridoxal-polymer conjugates exhibit excellent 19F pH sensitivity and pKa suitable for in vivo studies. The potential application of these polymeric indicators has been demonstrated in whole blood. These novel macromolecular pH probes offer a new approach for studying tissue physiology.