[Drug delivery systems using nano-sized drug carriers].

Nanotechnology has attracted great attention all over the world in recent several years and has led to the establishment of the novel technical field of "nanomedicine" through collaboration with advanced medical technology. Particularly, site-specific drug targeting using particle drug carrier systems has made substantial progress and been actively developed. This review explains the essential factors (size and chemical character) of drug carriers to allow long circulation in the bloodstream avoiding the reticuloendothelial system, and shows the present status and future perspective of several types of nano-carrier systems (water-soluble polymer, liposome and polymeric micelle). We also introduce the novel concept of multi-targeting system (combination of two or more targeting methodologies) for ideal drug therapies.