Drug Delivery Through Liposomes
Liposomes are the most common and well-investigated nanocarriers for the targeted drug delivery. Liposomes have led to the advancement of therapies in the area of cancer research because they improve in vivo cellular and tissue uptake, and enhancing biodistribution of compounds to target sites (Koning & Storm, 2003; Ding, Dziubla, Shuvaev, Muro & Muzykantov, 2006; Hua & Wu, 2013). Liposomes are vesicles of phospholipid that have one or more concentric lipid bilayers enclosing aqueous spaces. A diverse range of drugs can be encapsulated by these vesicles because they are able to entrap both lipophilic and hydrophilic compounds. By employing organic solvents or solvent exchange methods, liposome can be formed in an aqueous solution saturated with soluble drug and drug can then be loaded inside the liposomes. They can be used for oral (Rogers & Anderson 1998), pulmonary, transdermal and ocular delivery of drugs. Hydrophilic molecules are insoluble in lipid and can be placed in the aqueous compartment, and hydrophobic molecules are soluble in lipid and can be incorporated into the bilayer membrane. The hydrophobic molecules get entangled into the aqueous centre of the liposome this will lead to the convenient diffusion of the DNA, proteins and imaging agents through the lipid bilayers of the liposomes (Monteiro, Martins, Reis, & Neves, 2014). In conventional liposomes there is a lipid bilayer that comprises of cationic, anionic, or neutral (phospho) lipids and cholesterol, which consist of an aqueous compartment. With the help of Liposomal based drug delivery the therapeutic index of encapsulated drugs has been successfully improved (Koning, & Storm, 2003). The liposomes can easily permeate into the nuclear membrane of the tumour cell (Zhao, Dai, Lu, Chen, Lin & Shen, 2013).