A dextran-based probe for the targeted magnetic resonance imaging of tumours expressing prostate-specific membrane antigen.

Safe imaging agents able to render the expression and distribution of cancer receptors, enzymes or other biomarkers would facilitate clinical screening of the disease. Here, we show that diamagnetic dextran particles coordinated to a urea-based targeting ligand for prostate-specific membrane antigen (PSMA) enable targeted magnetic resonance imaging (MRI) of the PSMA receptor. In a xenograft model of prostate cancer, micromolar concentrations of the dextran -ligand probe provided sufficient signal to specifically detect PSMA-expressing tumours via chemical exchange saturation transfer MRI. The dextran-based probe could be detected via the contrast originating from dextran hydroxyl protons, thereby avoiding the need of chemical substitution for radioactive or metallic labelling. Because dextrans are currently used clinically, dextran-based contrast agents may help extend receptor-targeted imaging to clinical MRI.