ABSTRACT
Further development of effective gene transfer vector systems is key to the promotion of human gene therapy [1]. Numerous viral and nonviral (synthetic) methods for gene transfer have been developed [2,3], and generally viral methods are more efficient than nonviral methods for delivery of genes to cells. However, viral vectors present safety issues because of cointroduction of essential genetic elements from the parent viruses, leaky expression of viral genes, immunogenicity, and alterations of host genomic structure. In general, nonviral vectors are less toxic and less immunogenic than viral vectors. However, most nonviral methods are less efficient for gene transfer, especially in vivo. Thus, both viral and nonviral vectors have limitations as well as advantages. Therefore, to develop an in vivo gene transfer vector with high efficiency and low toxicity, the limitations of one type of vector system should be compensated for by introducing the strengths of another.
