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

Abstract

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