(612a) Designing All-Organic MRI Contrast Particles Which Produce Contrast through Chemical Exchange Saturation Transfer

Paramagnetic and Super-Paramagnetic metal-based nanoparticles have been developed previously as MR contrast agents, and are in use for the imaging of drug delivery, gene therapy as well as to highlight processes such as plaque formation in blood vessels. We are now augmenting this library of agents with new liposome based MR particles consisting of lipids, cholesterol and either amino acids or carbohydrates and without metals. These particles can be selectively activated by frequency-specific RF irradiation, with the contrast produced due to chemical exchange saturation transfer (CEST) from exchangeable protons to water. In addition, these particles can be distinguished by the saturation frequency dependence of their sugar or amino acid content. We have injected these particles into the feet of mice, and imaged their trafficking to the popliteal lymph nodes. This trafficking was confirmed by incorporation of 111In-Cl into the liposomal lumen and obtaining SPECT-CT images.