Liposomes and Vesicular Drug Delivery Systems: Fundamentals, Advances and Clinical Applications

Abstract

Liposomes are versatile vesicular system for drug delivery that consists of phospholipid bilayers having an aqueous interior and are used extensively for improving the therapeutic effectiveness and safety of pharmaceutical agents. Liposomes are capable of encapsulating a variety of hydrophilic, hydrophobic and amphiphilic drugs, which are highly advantageous over conventional dosage forms, as a result of their unique structural properties. The benefits are targeted drug delivery, controlled release of the drug, sustained release of the drug, decreased drug toxicity and protection of the drugs from degradation and quick clearance. Liposomes have been the subject of much interest and several products have been approved for clinical applications by regulatory authorities. The major components of liposomes are phospholipids, cholesterol and surface modifiers like polyethylene glycol that provide membrane stability, permeability control, and longer circulation time. Liposomes can be prepared using different methods such as thin-film hydration, solvent injection, and double-emulsification from which different sizes, lamellarity and drug-loading efficiencies can be obtained. In addition, liposomes can be fashioned to be sensitive to external triggering factors like pH, temperature and pressure and improve their capacity in targeted and site-specific drug delivery systems. Key parameters like particle size, surface charge, encapsulation efficiency, phase behaviour and drug release rate are essential for the quality and performance of liposomal formulations. Because of these characteristics liposomes have been widely used in cancer therapy, vaccine delivery, antifungal therapy and other therapeutic fields. In summary, liposomes are a promising and sophisticated nanocarrier system with a promising application in the current drug delivery and pharmaceutical development.