Liposomes for encapsulating drugs and complexing DNA

Abstract

Surface-active substances, amphiphiles, show the ability of self-organization in solvents, forming self-assemblies with a large variety of morphologically different structures. One of these structures is liposomes, formed by phospholipid molecules. In this structure the hydrophobic chains of the lipids form a bilayer and the polar head groups of the lipids are oriented towards the outer and inner (core) regions. Liposomes can be prepared by thin film method. In order to control their size and lamellarity, traditional methods, extrusion and sonication, are used. Surface charge of the system can be adjusted by changing the amount of different types of phospholipids used. Liposomes are similar to cell membranes thus, they are very promising systems for drug delivery and gene delivery. These systems can easily fuse with the cell membranes, releasing their encapsulated materials into the cell, mimicking drug-delivery systems as well as acting as a vector carrying the genetic material in gene delivery. In this study, unilamellar vesicles have been prepared using synthetic phospholipids, zwitterionic DMPC and anionic DMPG mixtures. To increase the stability, cholesterol has been added to the phospholipid mixtures during the preparation of the liposomes. For the initial encapsulation studies, hydrophobic Vitamin-E and hydrophilic Cytochrome-C have been chosen. The same liposome system has also been used in encapsulating the Green Fluorescent Protein (GFP) encoding DNA fragments and transferring them to the target cells obtaining high transfection efficiency with low toxicity in the presence or absence of cationic mediator, divalent cation Ca2+. The slightly anionic liposomes have been compared with the non-liposomal cationic transfecting agent with respect to transfection efficiency and toxicity in the vertebrate’s retina cells, MIO-1 Müller cells.