Pharmacokinetic considerations in the development of labeled liposomes and micelles for diagnostic imaging

The current status of application of liposomes and micelles as carriers for diagnostic imaging agents in experimental and clinical medicine is considered. Liposomes and micelles loaded with appropriate contrast agents have been shown to be suitable for all imaging modalities, including gamma-, magnetic resonance (MR), and computed tomography (CT). The methods are briefly described to prepare liposomes loaded with various contrast agents, as well as some basic data on their in vitro and in vivo properties and biodistribution. Certain pharmacokinetic considerations associated with the use of plain and long-circulating liposomes and micelles as pharmaceutical carriers are discussed. The application of contrast-loaded liposomes in different modalities for the experimental and clinical imaging of various organs, tissues, and pathological conditions is briefly reviewed. New trends in the preparation and use of contrast-loaded liposomes and micelles are also considered, such as the application of amphiphilic polychelating polymers and polymers for steric protection of microparticulate pharmaceutical carriers.