Liposomes for drug delivery: review of vesicular composition, factors affecting drug release and drug loading in liposomes

Liposomes are considered among the most versatile and advanced nanoparticle delivery systems used to target drugs to specific cells and tissues. Structurally, liposomes are sphere-like vesicles of phospholipid molecules that are surrounded by equal number of aqueous compartments. The spherical shell encapsulates an aqueous interior which contains substances such as peptides and proteins, hormones, enzymes, antibiotics, antifungal and anticancer agents. This structural property of liposomes makes it an important nano-carrier for drug delivery. Extrusion is one of the most frequently used technique for preparing monodisperse uni-lamellar liposomes as the technique is used to control vesicle size. The process involves passage of lipid suspension through polycarbonate membrane with a fixed pore size to produce vesicles with a diameter near the pore size of the membrane used in preparing them. An advantage of this technique is that there is no need to remove the organic solvent or detergent from the final preparation. This review focuses on composition of liposome formulation with special emphasis on factors affecting drug release and drug-loading.Liposomes are among the most effective and multifunctional nanocarriers. However, they possess certain prevalent limitations such as lack of targeting strategies, production challenges and slow overall transition of approved therapies into clinic. Improving drug loading and release capabilities of liposomal drug formulations with efficient delivery optimisation can be the most effective path in designing this class of nanoparticle drugs. Considering the numerous applications of liposomes, the drug delivery research community must utilise these nanocarriers to their maximum potential in an attempt to introduce novel medications against life threatening diseases.