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Messenger RNA encoding luciferase (mLUC) was complexed to the cationic lipids Lipofectamine or DOTAP/DOPE, and to the cationic polymer linear poly(ethyleneimine) (linPEI). The complexes were incubated with HeLa cells and luciferase expression was assessed. The type of non-viral carrier used determined the extent and duration of protein expression. Maximal duration of mRNA expression was about 9 days for Lipofectamine complexes, i.e. not very much shorter than with pDNA polyplexes. Interestingly, luciferase activity was already detected 30 min after adding the mRNA complexes to the cells, independent on the type of carrier. We also assessed the proportion of cells that become transfected by means of transfection with an mRNA encoding GFP. For both cationic lipids transfection with mRNA yielded a substantially larger fraction of transfected cells (more than 80%) than transfection with pDNA (40%). In addition we tested the carriers for their ability to mediate delivery of mRNA encoding CXCR4 into mesenchymal stem cells. The fraction of CXCR4-positive cells obtained with the mRNA–cationic lipid complexes was around 80%, as compared to 40% for the linPEI polyplexes. Our results demonstrate that the advantage of the use of mRNA over that of pDNA may under certain conditions outweigh the disadvantage of the somewhat shorter expression period.