Classification and basic properties of contrast agents for magnetic resonance imaging

Functional L-lysine dendritic macromolecules as liver-imaging probes

Liver-imaging probes are prepared through the conjugation of Gd chelates and galactosyl moieties to peptide dendrimers. The dendritic probes possessing highly controlled structures and a single molecular weight have a two-fold increase in T(1) relaxivity to 9.1 x 10(3) (Gd M)(-1) s(-1) compared to Gd-DTPA. No obvious cytotoxicity of this multifunctional dendritic agent is discovered in vitro. The dendrimer bearing galactosyl moieties leads to a much-higher hepatocyte-cell uptake in vitro and provides good signal-intensity enhancement (35%) of mouse liver in vivo especially at 60 min after intravenous injection. In comparison, non-targeting Gd dendrimers provide only an 11% enhancement of imaging contrast at the same time point. Overall, the dendrimers bearing galactosyl moieties may be used as liver-imaging probes.

Molecular probes for the in vivo imaging of cancer

Advancements in medical imaging have brought about unprecedented changes in the in vivo assessment of cancer. Positron emission tomography, single photon emission computed tomography, optical imaging, and magnetic resonance imaging are the primary tools being developed for oncologic imaging. These techniques may still be in their infancy, as recently developed chemical molecular probes for each modality have improved in vivo characterization of physiologic and molecular characteristics. Herein, we discuss advances in these imaging techniques, and focus on the major design strategies with which molecular probes are being developed.