Nano Drug Delivery Systems and Liposomes

Progressive development of nanotechnology during the last decades and its increasing involvement in new fields represents its great importance in science and technology. One of its major parts is nanomedicine that is focused in this review. First general principles of medicinal nanotechnology, its history, application and classification are explained. Then Abraxane (a protein conjugated nano drug) design will be addressed. Liposomes as one of the best nano drug delivery systems with a platform for passive targeting are discussed next. Two examples of approved liposomal nanomedicines are described from the state-of-the-art design emphasizing physiologic barriers and formulation strategies to overcome these imposed limitations. Passive targeting to tumors is provided by "Enhanced Permeation and Retention" effect (EPR). Liposomes can be removed from circulation by the mononuclear phagocyte system (MPS) clearance in no time. This effect is also used to passively target liposomes in MPS to treat localized infections for example. Pegylation of liposomes which means attachment of polyethylene glycol chains to the surface of liposomes is one of the methods used to enhance liposome residence time in blood circulation in order to give the vesicles more chance to accumulate at the target site by EPR effect.
Liposomal medicines have shown significant decrease in toxicity in comparison with free drugs. Their accumulation in target tissue by passive targeting is the main reason for reduction in drug toxicity.
Liposomes are being used for treating different diseases such as infection, hepatitis, cardiovascular diseases and immune system disorders. However, the vast majority of investigational liposomes are anticancer drugs