Recent progress in polymeric gene delivery systems.

Considerable progress in polymeric gene delivery systems has been made over the last several years. First generation polymers have been replaced by safer and more efficient carrier systems through molecular functionalization, improving polymer biocompatibility, biological stability, cell-specificity, and intracellular trafficking. Many new polymers have moved from in vitro characterization to preclinical validation in animal models of cancer, diabetes, and cardiovascular disorders. Although the transfection efficiency of most polymeric carriers is still significantly lower than that of viral vectors, their structural flexibility allows for continued improvement in polymer activity. Also, simple manufacturing and scale-up schemes and the low cost of manufacturing are likely to eventually compensate for the performance gap between viral and polymeric vectors and establish clinical recognition and commercialization of polymer-based gene therapy drugs.