The effects of charge separation in quaternary ammonium, DABCO-containing polymers on in vitro toxicity and gene delivery

Polycation materials have recently emerged as promising systems for the delivery of genetic material. In this study, several DABCO (1,4-diazabicyclo[2.2.2]octane) polymers are investigated for their ability to bind and deliver plasmid DNA (pDNA) into mammalian cells. The DABCO polymers are synthesized by copolymerization of DABCO with 1,3-dibromopropane (D3), 1,4-dibromobutane (D4), 1,6-dibromohexane (D6), 1,8-dibromooctane (D8), and 1,10-dibromodecane (D10) to form a series of quaternary ammonium polymers with increasing charge separation. Gel retardation experiments reveal that each polymer (D3-D10) binds pDNA above a charge ratio of 1.0 (polymer +/ pDNA -). The polycations are examined for in vitro transfection efficiency and toxicity in BHK-21 cells. Results of the transfection experiments indicate that the D6 polymer had the highest transfection efficiency. Although all of the polymers are shown to have some toxicity, the D8 and D10 polymers are more toxic to BHK-21 cells; approximately 30% of the cells survive at a charge ratio of 5 +/- as compared to the D3, D4, and D6 polymers where survival rates are about 80%.