Higher lung accumulation of intravenously injected organic nanotubes.

The size and shape of intravenously injected particles can affect their biodistribution and is of importance for the development of particulated drug carrier systems. In this study, organic nanotubes (ONTs) with a carboxyl group at the surface, a length of approximately 2 μm and outer diameter of 70-90 nm, were injected intravenously into tumor-bearing mice. To use ONTs as drug carriers, the biodistribution in selected organs of ONTs postinjection was examined using irinotecan, as an entrapped water-soluble marker inside ONTs, and gadolinium-chelated ONT, as an ONT marker, and compared with that of a 3 μm fluorescently labeled spherical microparticle which was similar size to the length of ONTs.