Mri Molecular Imaging with Nanoparticles: A Technical Platform for Early Diagnosis of Cancer

Most contrast media used today are nonspecific. They give signals at e.g. sites of high vascularization or raised permeability. An exception is for example the use of octreotidelabeled radioisotopes in nuclear medicine, which enable molecular imaging by binding of the molecules to somatostatin receptors [1]. For MRI, Molecular Imaging is only achievable by use of nanoparticles. Perfluorocarbon nanoparticles are in development for targeting and MR T1 imaging of vascular walls e.g. fibrins, integrins [2]. Clinically, the only nanoparticles used in MR are the superparamagnetic USPIOs (UltraSmall Particles of Iron Oxide) for T2 modality. They are used for imaging of lymph nodes and tumors [3]. In molecular imaging a lesion or illness is identified by the detection of a single molecule specific for this illness. Molecular detection is achieved by attaching antibodies or other targeting molecules to a signal-generating vector carrying signal moieties. In this way, the specificity of the signal is raised and background signals reduced. MI for clinical application is not always easy to establish. Low sensitivity, e.g. MRI, or low penetration depth, e.g. optical imaging, have hindered successful clinical use. The problem of low sensitivity can be overcome by use of adequate vectors. We aim to develop nanoparticles for Molecular Imaging in MRI, carrying hundreds of signal molecules [4]. Large numbers of signaling groups are needed because of the low sensitivity of the imaging technique. On the other hand, the use of MRI implies great advantages such as its high spatial resolution and the lack of ionizing radiation. Our final aim is to synthesize nanoparticles suitable for targeted imaging and therapy. Methods