Nano-Sized Drug Delivery Systems for Lymphatic Delivery

The lymphatic system plays important roles for immune responses, spreading cancer cells or viruses and disseminating infections. Thus, targeting drugs, such as anticancer, immunotherapeutic and lymphoid contrast agents, to both tumors and the lymphatics, has several advantages such as reduced systemic side effects and increased efficacy. For these reasons, much interest has been focused on the nature of the lymphatics and various studies on the lymphatic delivery of drugs have been carried out. Because the lymphatics consist of a single layer endothelium and have higher permeability compared with that of blood capillaries, studies using nano-sized carriers have been performed. Polymeric nanoparticles, liposomes, and lipid-based vehicles have been adopted as lymphatic delivery carriers. This review will focus on the clinical use of such nano-sized carriers that have been developed for imaging and drug delivery to the lymphatic system. Lymphatic delivery of drugs, such as anticancer, immunotherapeutic and lymphoid contrast agents, using nano-sized carriers has much more improved ability compared with that of conventional dosage forms, but it has not shown the specific lymphatic targeting ability yet. Finally, the challenges for the future are suggested in terms of the mechanisms governing the lymphatic delivery of nano-sized carriers.