Paramagnetic micelles and liposomes

In the context of the development of new contrast agents for medical diagnostic imaging, the nanoparticulate carriers have indeed drawn special attention. These systems allow for an efficient site-specific delivery of targeted contrast agents and, due to their size, provide some relaxivity enhancement with respect to the isolated paramagnetic molecules. 

Several types of particulate compounds have been studied so far. Among these are solid nanoparticles containing gadolinium complexes 98) or macro-molecular systems such as polylysine 99). 

The earliest and most widely studied particulate carriers for paramagnetic substances are the liposomes, either entrapping hydrophilic contrast agents within the internal aqueous phase, or incorporating lipophilic complexes in their phospholipidic bilayer membrane 100,101). 

More recently, micelles have also been proposed as contrast agents. They are colloidal particles with a hydrophobic core and a hydrophilic shell, formed by amphiphilic compounds 102). 

Two types of micellar systems have been described, the first one includes Gd complexes capable of self-organization resulting in a supramolecular assembly 103), while the other class of micelles, also named mixed micelles is made of several components a lipophilic gadolinium chelate, one or several phospholipid(s) and a non-ionic surfactant containing a polyoxyethylene chain 104,105). 

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Proton Relaxivity of Various Paramagnetic Micelles and Liposomes... 

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