Lipid-Based Nanoparticles in Cardiovascular Molecular Imaging

The Gd(III) complexes currently used as MRI contrast agents are hydrophilic agents that distribute in the vascular and extracellular compartments. The visualization of atherosclerotic plaques requires systems endowed with lipophilic characteristics. Several Gd(III) complexes bearing lipophilic substituents have been reported. Among them Gd(III) complexes containing one or two aliphatic chains appear particularly useful for the intended application. These amphiphilic Gd(III) complexes have been incorporated into various types of supramolecular adducts that ensure enough sensibility for their detection in MR images of atherosclerotic plaques. Much attention has been devoted to the use of HDL and LDL Gd-loaded particles. The presence of long aliphatic chain(s) promotes the spontaneous aggregation of these complexes to form micelles that may associate as such to the surface of HDL particles. It has been shown that the transfer of single amphiphilic complexes into the lipidic core of the particles is possible by disassembling the micelles through the formation of "host-guest" adducts with β-cyclodextrin. Gd-loaded liposomes have also been successfully tested in plaque detection as well as perfluoronanoparticles loaded with CEST agents.