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Article History :
Received: 18 August 2016
Revised: 17 February 2017
Accepted: 22 February 2017
ePublished: 13 April 2017
Keywords:
* Liposomes
* Hydrophobic drugs
* Phospholipid
* Drug delivery system
Abstract
Liposomes, due to their various forms, require further exploration. These structures can deliver both hydrophilic and hydrophobic drugs for cancer, antibacterial, antifungal, immunomodulation, diagnostics, ophtalmica, vaccines, enzymes and genetic elements. Preparation of liposomes results in different properties for these systems. In addition, based on preparation methods, liposomes types can be unilamellar, multilamellar and giant unilamellar; however, there are many factors and difficulties that affect the development of liposome drug delivery structure. In the present review, we discuss some problems that impact drug delivery by liposomes. In addition, we discuss a new generation of liposomes, which is utilized for decreasing the limitation of the conventional liposomes.
Introduction
In the late nineteenth century, German bacteriologist Paul Ehrlich, used the term "magic bullet," which means chemical carriers that have the property of selectivity in killing abnormal cells without any effect on the normal ones.1 In order to improve this specificity through drug delivery systems, there are a variety of different approaches, which are based on a number of physical and bio-chemical principles.2
Liposomes, as carrier systems, have been explored more than any than other system as a result of their various forms. Phospholipid bilayers membranes can generate sphere structure with internal hydrophilic compartment through introducing phospholipids in water solution; these structures are called liposomes. About four decades ago, Bangham and co-workers defined liposomes as vesicles with small size and spherical shapes that can be generated from phospholipids, cholesterols, non-toxic surfactants and even membrane protein. Investigations of this group resulted in regarding liposomes as delivery systems, which are characterized by carrying a variety of compounds in the core section.3,4 These structures can encapsulate and deliver both hydrophilic and hydrophobic substances afflictively.
Raw Materials in Liposome Preparation
Lipids are amphipatic molecules with water-friendly and water-hating parts (Figure 1). Liposomes are consisted of single or multiple lipid bilayers formed by hydrophilic and hydrophobic interactions with the aqueous phase. The hydrophobic parts (tails) of liposomes are repelled by water molecules resulting in liposome self-assembly.5 In addition, Phosphatidylcholine (PC) and Dipalmitoyl PC can be used for liposome generation,...