Calcium enhances the transfection potency of plasmid DNA-cationic liposomecomplexes

It is shown that calcium increases the in vitro transfection potency of pla smid DNA-cationic liposome complexes from 3- to 20-fold. The effect is Ca2 specific as other cations, such as Mg2+ and Nai, do not give rise to enhan ced transfection and the effect can be inhibited by the presence of EGTA. I t is shown that Ca2+ increases cellular uptake of the DNA-lipid complexes, indicating that increased transfection potency arises from increased intrac ellular delivery of both cationic lipid and plasmid DNA in the presence of Ca2+. In particular, it is shown that the levels of intact intracellular pl asmid DNA are significantly enhanced when Ca2+ is present. The generality o f the Ca2+ effect for enhancing complex-mediated transfection is demonstrat ed for a number of different cell lines and different cationic lipid formul ations. It is concluded that addition of Ca2+ represents a simple and usefu l protocol for enhancing in vitro transfection properties of plasmid DNA-ca tionic lipid complexes. (C) 2000 Published by Elsevier Science B.V. All rig hts reserved.