Dual ¹⁹F/¹H MR Gene Reporter Molecules for <i>in Vivo</i> Detection of β-Galactosidase

Increased emphasis on personalized medicine and novel therapies requires the development of noninvasive strategies for assessing biochemistry <i>in vivo</i>. The detection of enzyme activity and gene expression <i>in vivo</i> is potentially important for the characterization of diseases and gene therapy. Magnetic resonance imaging (MRI) is a particularly promising tool, since it is noninvasive and has no associated radioactivity, yet penetrates deep tissue. We now demonstrate a novel class of dual ¹H/¹⁹F nuclear magnetic resonance (NMR) <i>lacZ</i> gene reporter molecule to specifically reveal enzyme activity in human tumor xenografts growing in mice. We report the design, synthesis, and characterization of six novel molecules and evaluation of the most effective reporter in mice <i>in vivo</i>. Substrates show a single ¹⁹F NMR signal and exposure to β-galactosidase induces a large ¹⁹F NMR chemical shift response. In the presence of ferric ions, the liberated aglycone generates intense proton MRI T₂ contrast. The dual modality approach allows both the detection of substrate and the imaging of product enhancing the confidence in enzyme detection

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(<i>N</i>-(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 (<i>T</i>₂) of the polymer was observed to be pH-dependent, whereas the spin-lattice relaxation time (<i>T</i>₁) was not. The pH probe in the polymer shows a strong fluorescence-based ratiometric pH response with emission window changes, exhibiting blue emission under acidic conditions and green emission under basic conditions, respectively. This study provides new materials with multimodalities for pH sensing and imaging