PEG-based micelles as carriers of contrast agents for different imaging modalities.

The review deals with the fast growing field of diagnostic micelles. The need and requirements for microparticulate contrast agents are discussed. Brief analysis of the micellization process and micelle properties shows that micelles made of amphiphilic co-polymers seem to be the most attractive for practical application. These micelles can be prepared from the variety of co-polymers including hydrophilic polymers grafted on one terminus with lipid residues. Polymeric micelles are considered loaded or modified with various contrast reporter moieties for gamma-scintigraphy, magnetic resonance imaging (MRI), and computed tomography (CT). Their in vitro and in vivo properties are discussed and the results of the initial animal experiments are presented. Mixed micelles were prepared from diacyllipid-polyethylene glycol (PEG) conjugates and polymeric amphiphilic chelates, containing entrapped metals, such as 111-In or Gd, and used for the experimental gamma- and MR imaging of various components of lymphatic system in rabbits. The method is also described to prepare polymeric iodine-containing PEG-based micelles which may act as a long-circulating blood pool imaging agent for CT. Experimental CT-imaging performed in mice and rabbits demonstrated high potential of a micellar contrast agent.