The non-viral vectors and targeting methods offer some specific advantages. These include better safety profiles (lower toxicity and non-infectious properties) and the capacity to transfer large genes and low production costs. The clinical usefulness of non-viral methods has been hindered by their relatively low gene delivery and transgene expression efficiencies. However, recent problems in clinical trials using viral vectors renewed interest in non-viral technologies, particularly that the properties of non-viral vectors make them appear closer to the traditional pharmaceutics.