Preparation of peptide- and protein-based molecular assemblies and their utilizations as nanocarriers for tumor imaging

Three types of nanocarriers from our group for imaging probes are reviewed here. Novel nanocarriers of “peptosome” and “lactosome” were prepared from amphiphilic polymers uniquely having a helical segment as a hydrophobic block. Apoferritin was chemically modified on the surface, and used for nanocontainer of a novel Gd-chelator. Lactosome was intensively studied and labeled with indocyanine, 18F, and 131I for tumor imaging by NIRF, PET, and SPECT, respectively. Those labeled lactosomes are shown to be effective for tumor imaging on the basis of the EPR effect and the stealth property in vivo. The superiority of lactosome over other commercially available imaging agents is experimentally confirmed, which is explained by the dense and thick hydrophilic polymer brush formed on the surface and the helix bundles at the hydrophobic core. Our final goal is to develop the next-generation lactosome, which is the nanocarrier which is usable for a diagnostic agent and a therapeutic agent showing the same in vivo disposition even upon frequent administration.