Liposome-Encapsulated Antimicrobial Peptides: Potential Infectious Diseases Therapy

Liposomes: Drug Delivery Platform

The use of liposomes as a drug delivery platform is an area of extensive research and to a certain extent successful too. Some of the most widely used liposome-based antimicrobial agents includes AmBisome® (Gilead Sciences, Inc, San Dimas, CA), Amphotec® (Ben Venue Laboratories, Inc, Bedford, OH) and Abelcet® (Sigma-Tau PharmaSource, Inc, Indianapolis, IN). Liposomal formulations exhibit enhanced activity against pathogens since the incorporated antimicrobial agent becomes less prone to the inactivation by bacterial enzymes. The other theory to support enhanced activity is the reduced electrostatic repulsion of liposomal antibiotics (Nacucchio, 1985). Clinically it has been noted that due to the release of drug upon target attainment, the antimicrobial related toxicity in-vivo is much lower (Uhumwangho et al., 2005).

With the on-going research on liposomes, there are certain challenges that have been identified with the designing of liposomes. One of them is related to the premature drug release from liposome before reaching the target. The other challenge is that higher liposomal volume is needed when the encapsulation efficiency is low to achieve clinical dosages (Mirzaee et al., 2009). Development of resistance like in any other antimicrobial agent is another issue that can reduce the efficacy of liposomal formulations. Resistance can develop due to enzymatic inactivation by bacterial enzymes, alterations on molecular target preventing the drug to enter the cell and rapid extrusion of drug (Nikaido, 1994, Immordino et al., 2006). Various types of liposomes were also found to interact with the blood coagulation system in-vivo. They interact with blood cells, especially platelets, leading to thrombocytopenia (Constantinescu, 2003 and Reinish, 1988).