A bisphosphonate for (19)F-magnetic resonance imaging

(19)F-magnetic resonance imaging (MRI) is a promising technique that may allow us to measure the concentration of exogenous fluorinated imaging probes quantitatively in vivo. Here, we describe the synthesis and characterisation of a novel geminal bisphosphonate ((19)F-BP) that contains chemically-equivalent fluorine atoms that show a single and narrow (19)F resonance and a bisphosphonate group that may be used for labelling inorganic materials based in calcium phosphates and metal oxides. The potential of (19)F-BP to provide contrast was analysed in vitro and in vivo using (19)F-MRI. In vitro studies demonstrated the potential of (19)F-BP as an MRI contrast agent in the millimolar concentration range with signal-to-noise ratios (SNR) comparable to previously reported fluorinated probes. The preliminary in vivo MRI study reported here allowed us to visualise the biodistribution of (19)F-BP, showing uptake in the liver and in the bladder/urinary system areas. However, bone uptake was not observed. In addition, (19)F-BP showed undesirable toxicity effects in mice that prevent further studies with this compound at the required concentrations for MRI contrast. This study highlights the importance of developing (19)F MRI probes with the highest signal intensity achievable.