Calcium enhances the transfection potency of plasmid DNA-cationic liposome complexes

It is shown that calcium increases the in vitro transfection potency of plasmid 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 enhanced transfection and the effect can be inhibited by the presence of EGTA. It is shown that Ca2+ increases cellular uptake of the DNA-lipid complexes, indicating that increased transfection potency arises from increased intracellular delivery of both cationic lipid and plasmid DNA in the presence of Ca2+. In particular, it is shown that the levels of intact intracellular plasmid DNA are significantly enhanced when Ca2+ is present. The generality of the Ca2+ effect for enhancing complex-mediated transfection is demonstrated for a number of different cell lines and different cationic lipid formulations. It is concluded that addition of Ca2+ represents a simple and useful protocol for enhancing in vitro transfection properties of plasmid DNA-cationic lipid complexes. (C) 2000 Published by Elsevier Science B.V. All rights reserved.