Dual MRI-SPECT agent for pH-mapping

Alterations in extracellular tissue pH accompany many disease processes, such as cancer, inflammation and infection. In tumours, extracellular pH is often lower than in normal tissue and it can be correlated with prognosis. 1 Therefore, the capability to image tissue pH in the clinic would offer a generic method for detecting disease and response to treatment. There are currently no such methods that could be used in the clinic, even if advances have been made for the in vivo measurement of tumor pH.2 Despite the good pH responsiveness of several reported Gd(III) containing systems, their practical use has been hampered by the need of knowing their local concentration in order to unambigously assign the observed variations to changes in relaxivity and not to changes in the local concentration of the paramagnetic agent. Herein we report our results aimed at developing a dual MRI/SPECT pH-responsive agent where the SPECT-active moiety acts as a reporter of the concentration of the MRI responsive one thus allowing the transformation of the observed 1H-relaxation rates into relaxivities to recover the information relative to the pH determination.JRC.I.4-Nanobioscience