The term transfection is commonly used to describe the process of adding DNA into cells with a view to mediating protein expression of the transgene of interest. Although DNA transfection is the most commonly adopted technique, the term can also be applied to RNA transfection, where the purpose may also be to mediate protein expression or to achieve knockdown of the transcription of a specific gene, either by RNAi, ribozyme or antisense methodologies.
Gene therapy is a strategy in which nucleic acid is administered for therapeutic purposes for both inherited and acquired diseases. A number of viral and nonviral vectors have been developed to circumvent the barriers for gene delivery, but the safety concerns of viral vectors have not been solved yet. On the other hand, non viral vectors are still inefficient compared to viral vectors but they offer safety as the main advantage and moreover they can be easily formulated as medicines.