Given the well-defined loss of a specific type of neurons (dopaminergic neurons) in a well defined region of the brain (S. nigra), the concept of cell replacement therapy in PD has emerged already in the early 1980s.Replacing diseased cells with healthy cells, called cell therapy, is similar to the process of organ transplantation only the treatment consists of transplanting cells instead of organs. Some conditions or injuries can be treated through transplantation of entire healthy organs, but there is an acute shortage of donors. Stem cells can serve as an alternate and renewable source for specialized cells.These unique characteristics make stem cells very promising for supplying cells to treat debilitating diseases like Alzheimer's disease, cancer, Parkinson's disease, type-1 diabetes, spinal cord injury, stroke, burns, heart disease, osteoarthritis and rheumatoid arthritis. Today, donated organs and tissues are often used to replace those that are diseased or destroyed. Unfortunately, the number of people needing transplants far exceeds the number of organs available.

Liposomes as well as formulations based on drug-lipid complexes have been extensively investigated for the delivery of a wide range of pharmaceutical compounds. Commercial licensing of liposomal dispersions for parenteral and topical use in humans has been fairly recent and has occurred as a result of interdisciplinary scientific advances in surface chemistry, membrane biophysics, and molecular pharmacology. These developments were supported by pioneering contributions from scientists in the fields of molecular pharmaceutics, drug delivery, and chemical engineering. Thus, since their original simplistic use as vesicular models for studying membrane properties and transport, liposomal systems have evolved into complex yet elegant assemblies for drug delivery. Liposomes are now being developed with specific therapeutic roles for tissue and cellular targeting and have been skillfully manipulated to achieve desired clinical outcomes by altering in vivo drug biodistribution and disposition. Liposomes are microscopic vesicles composed of one or more lipid bilayers arranged in concentric fashion enclosing an equal number of aqueous compartments.