Induced pluripotent stem (iPS) cells were originally generated from mouse 
fibroblasts by enforced expression of Yamanaka factors (Oct3/4, Sox2, Klf4, and 
c-Myc). The technique was quickly reproduced with human fibroblasts or 
mesenchymal stem cells. Although having been showed therapeutic potential in 
animal models of sickle cell anemia and Parkinson's disease, iPS cells generated 
by viral methods do not suit all the clinical applications. Various non-viral 
methods have appeared in recent years for application of iPS cells in cell 
transplantation therapy. These methods mainly include DNA vector-based 
approaches, transfection of mRNA, and transduction of reprogramming proteins. 
This review summarized these non-viral methods and compare the advantages, 
disadvantages, efficiency, and safety of these methods.