With the development of biomedical techniques, a new generation of gene delivery systems were investigated,
characterized and developed. Many of them were also filed as patents. Such advanced gene delivery techniques have greatly
improved gene therapy from in vitro, in vivo to clinics. In this review, three most significant gene delivery systems (physical
transfection techniques, virus based delivery vectors and chemically engineered delivery systems) will be studied and their
advantages, limitations, patents and applications will be discussed.