MRI in campo biomedico e farmaceutico: nanoparticelle SPIO e ottimizzazione del contrasto

Recently, great efforts have been made in order to develop new probes designed for Magnetic Resonance Imaging (MRI) and for cellular labeling. Superparamagnetic iron oxide (SPIO) nanoparticles have been widely used as MRI negative contrast agents. Their major drawback is the difficulty in discriminating between SPIO induced signal loss and other sources of hypointense signal such as tissue interfaces, air or motion artifacts.The objectives of present work were to prepare SPIO particles suitable for cell labelling and to develop new MRI techniques to obtain positive contrast from SPIO and other T2agents like paramagnetic liposomes. SPIO particles were synthesized by co-precipitation method and coated with citric acid, aminopropyltriethoxysilane (APTES) or polyamidoamine (PAMAM) dendrimers to reduce toxicity and to improve biocompatibility. Labeling experiments were performed by incubating stem cells and macrophages with different SPIO concentrations. Paramagnetic Dysprosium-HPDO3A complex encapsulating liposomes were prepared by the film rehydration method.Cells were efficiently labeled with SPIO particles without loss of cell viability or proliferation. Positive contrast from SPIO was investigated and optimized using a modified IRON sequence. The positive contrast effect was detected for SPIO labeled cells and interestingly, it has been found that the potential of this approach may extend to paramagnetic agents accumulated in vesicles such as liposomes.