Liposomal Drug Delivery: A Versatile Platform for Challenging Clinical Applications

Abstract

-Liposomes are lipid based vesicular systems that offer novel platform for versatile drug delivery to target cell. Liposomes were first reported by Bangham and his co-workers in 1964 (1). Since then, liposomes have undergone extensive research with the prime aim to optimize encapsulation, stability, circulation time and target specific drug delivery. Manipulation of a liposome's lipid bilayer and surface decoration with selective ligands has transformed conventional liposomes into adaptable and multifunctional liposomes. Development of liposomes with target specificity provide the prospect of safe and effective therapy for challenging clinical applications. Bioresponsive liposomes offer the opportunity to release payload in response to tissue specific microenvironment. Incorporation of novel natural and synthetic materials has extended their application from stable formulations to controlled release targeted drug delivery systems. Integration and optimization of multiple features into one system revolutionized research in the field of cancer, gene therapy, immunotherapy and infectious diseases. After 50 years since the first publication, this review is aimed to highlight next generation of liposomes, their preparation methods and progress in clinical applications.

Liposomal systems as carriers for bioactive compounds

“…Once formed, the multilamellar liposomes can be transformed into unilamillar vesicles by different methods (Zawada 2004;Akbarzadeh et al 2013;Eloy et al 2014;Madni et al 2014). For example, MLVs may be sonicated or passed through a membrane with pores of nanometric dimensions (extrusion method) to form unilamellar vesicles that have properties very similar those of to natural membranes.…”

“…This process, as well as the method of freeze/thawing the lipid suspension, results in the formation of unilamellar vesicles which are larger than those formed by sonication; it also has a more accurate size control. The larger size is caused by the reduction of liposome lamellarity due to disruption of the bilayers, which then restructure to form new vesicles, thus increasing the number of vesicles and consequently encapsulation of the compound (Zawada 2004;Akbarzadeh et al 2013;Eloy et al 2014;Madni et al 2014).…”

“…In the reverse phase evaporation method, a solution of the lipid and an organic solvent is added to an aqueous buffer solution to form a water-in-oil emulsion that is subjected to evaporation under low pressure, resulting in the formation of the liposome system (Madni et al 2014). …”

“…However, their cell-like structure led to investigations on their efficacy as a tool to carry potent molecules into the human body. Nowadays they are used for the encapsulation of unstable compounds considered to be essential to human health, such as antioxidants, antimicrobials, bioactive elements, antigenic proteins, thereby preserving their functionality (Madni et al 2014;Schwendener 2014;Patil and Jadhav 2014). Liposomal vesicles have emerged as one of the novel carrier systems most studied by the scientific community over the past decades and have revolutionized research in many different fields, such as cosmetics, drugs, food, agriculture, with applications in chemotherapy treatments, gene therapy, vaccines, antimicrobial agents, among others (Madni et al 2014).…”

“…The main advantage of modern liposomes lies in their sustained action, enhanced bioavailability, high cellular uptake and targeted delivery of therapeutic agents. It is predictable that these delivery systems will be increasingly applied in the near future with success, leading to major improvements in the field of vaccine development (Madni et al 2014;Schwendener 2014).…”