We report on the synthesis of various acridine (Acr)-spacer-nuclear localization signal (NLS) peptide conjugates and explore whether their use as NLS-labeling agent of plasmidic DNA could improve gene nuclear import and expression into cells when mediated by synthetic DNA complexes. As the conditions of successful use of the NLS properties to enhance gene transfer are not clear, and with the aim of detecting and defining the requirements of NLS- ...