Why should I use a vector for gene transfer?

Naked nucleic acids have no innate method of passing through the cell or nuclear membranes, and are vulnerable to degradation by environmental or cytosolic enzymes such as nucleases. Physical transfection methods such as electroporation or sonoporation aid nucleic acid passage into the cell by using electric charge and ultrasound waves, respectively, to create pores in the membrane,¹ while chemical methods can employ cationic lipids (lipofection) or polymers to shield nucleic acids and encourage cellular uptake.¹

However, to best ensure nucleic acid uptake by the cell and incorporation into the target genome, the target nucleic acid sequence is attached to a vector. Vectors are DNA molecules containing a foreign DNA insert which are used to transport and deliver said payload to the target cell’s genome for incorporation. Commonly used vectors include bacterial plasmids, lipids, nanoparticles, and viruses.^1,2

References:
1. M.S. Al-Dosari and X. Gao, “Nonviral Gene Delivery: Principle, Limitations, and Recent Progress,” AAPS J 11(4): 671, 2009.
2. I.M. Verma and N.B. Somia, “Gene therapy -- promises, problems and prospects,” Nature 389(6648): 239-242, 1997.