Multifunctional PHPMA-Derived Polymer for Ratiometric pH Sensing, Fluorescence Imaging, and Magnetic Resonance Imaging

In this paper, we report synthesis and characterization of a novel multimodality (MRI/fluorescence) probe for pH sensing and imaging. A multifunctional polymer was derived from poly(N-(2-hydroxypropyl)methacrylamide) (PHPMA) and integrated with a naphthalimide-based-ratiometric fluorescence probe and a gadolinium–1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid complex (Gd–DOTA complex). The polymer was characterized using UV–vis absorption spectrophotometry, fluorescence spectrofluorophotometry, magnetic resonance imaging (MRI), and confocal microscopy for optical and MRI-based pH sensing and cellular imaging. In vitro labeling of macrophage J774 and esophageal CP-A cell lines shows the polymer’s ability to be internalized in the cells. The transverse relaxation time (T2) of the polymer was observed to be pH-dependent, whereas the spin-lattice relaxation time (T1) was not. The pH probe in the polymer shows a strong fluorescence-based ratiometric pH response with emission window changes, exhibitin...