Molecular design of DDS was discussed focusing on the polymer utilization. The polymeric materials used for DDS were classified into biodegradable and non-biodegradable. Further, the biodegradable polymers were divided into naturally occurring and synthetic. Current topics on delivery systems of protein drugs, oral drug delivery, and slow release of anticancer drugs using biodegradable microspheres were briefly described. In addition, the fundamentals of active and passive targeting were summarized. Importance of studies on pharmacokinetics of injected polymers was stressed and recent results in this field were presented.
