Overview on Liposome as Drugs Carrier

The main objective of drug delivery systems is to deliver a drug effectively, specifically to the site of action and to achieve greater efficacy and minimise the toxic effects compared to conventional drugs. Amongst various carrier systems, liposomes have generated a great interest because of their versatility and have played a significant role in formulation of potent drugs to improve therapeutics. Enhanced safety and efficacy have been achieved for a wide range of drug classes, including antitumor agents, antivirals, antimicrobials, vaccines, gene therapeutics etc. Liposomes were first described by British hematologist Dr Alec D Bangham. These are vesicular concentric structures, range in size from a nanometer to several micrometers, containing a phospholipid bilayer and are biocompatible, biodegradable and nonimmunogenic.

There are three types of liposomes - MLV (multilamillar vesicles), SUV (Small Unilamellar Vesicles) and LUV (Large Unilamellar Vesicles). Phospholipids are amphipathic, i.e., part of their structure is hydrophilic and the other is hydrophobic. Liposome can carry both hydrophobic and hydrophilic molecules. They can be filled with drugs and used to deliver drugs. Another interesting property of liposomes is their natural ability to target cancer by their rapid entry into tumor sites. Anti-cancer drugs such as Doxorubicin (Doxil), Camptothecin etc. are currently being marketed in liposome delivery systems. Liposomes that contain low or high pH can be constructed such that dissolved aqueous drugs will be charged in solution. Another strategy for liposome drug delivery is to target endocytosis events and can also be decorated with opsonins and ligands. The use of liposomes for transformation of DNA into a host cell is known as lipofection. In addition to these applications, liposomes can deliver the dyes to textiles, pesticides to plants, enzymes and nutritional supplements to foods, and cosmetics to the skin. The use of liposomes in nano cosmetology also has many benefits, including improved penetration and diffusion of active ingredients, selective transport of ingredients, greater stability of active, reduction of unwanted side effects, and high biocompatibility. Despite of their potential value, the major obstacles are the physical stability and manufacture of the liposomal products and these problems still remain to be overcome. More liposome based drug formulations can be expected in the near future both for delivery of conventional drugs and for new biotechnology therapeutics such as recombinant proteins, antisense oligonucleotides and cloned genes.