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

Abstract

Increased emphasis on personalized medicine and novel therapies require the development of non-invasive strategies for assessing biochemistry in vivo. The detection of enzyme activity and gene expression in vivo is potentially important for the characterization of diseases and gene therapy. Magnetic resonance imaging (MRI) is a particularly promising tool since it is non-invasive, and has no associated radioactivity, yet penetrates deep tissue. We now demonstrate a novel class of dual 1H/19F nuclear magnetic resonance (NMR) lacZ 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 in vivo. 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 imaging of product enhancing the confidence in enzyme detection.

Novel Molecular Platform Integrated Iron Chelation Therapy for 1H-MRI Detection of β-Galactosidase Activity

“…The anomeric β-D-configuration of 10−13 in the 4 C 1 chair conformation was confirmed by the 1 H NMR chemical shifts at δ H-1′ = ∼4.95 ppm of the anomeric protons, and the coupling constants of J 1′,2′ = 8 Hz and J 2′,3′ = 10 Hz.The anomeric carbon resonances appeared at δ C-1′ ∼101.40 ppm are in accordance with the β-D-configuration 27. …”

A fluorogenic probe for β-galactosidase activity imaging in living cells

“…However, the fluorescent signal was confined to mitochondria. Although in vivo imaging of β-Gal activity has been the focus of many biological studies, 4, 35, 36 the disappearance of NIR fluorescence in cells diminishes the potential of using AcGQCy7 in animal studies.…”

Divalent metal transporter, DMT1: A novel MRI reporter protein

“…In some cases, these methods are designed to reveal the presence of a traditional reporter protein, such as β-galactosidase (β-gal) (40,42), which has the advantage that many experimental systems and β-gal expressing reporter mice are already available. While sophisticated contrast-probes have been demonstrated for these purposes, including ligands that utilize Gd and/or 19 F for MRI detection, the probes are generally macromolecular agents that have much more complicated issues of delivery to the cells/tissues of interest than the ionic Mn 2+ required for the DMT1 reporter.…”