Requirements for the nuclear entry of polyplexes and nanoparticles during mitosis

Background Nonviral gene delivery has a limited efficacy partly as a result of poor nuclear delivery, yet an understanding of the mechanisms of nuclear entry is limited. The present study aimed to test the common hypothesis that most nonviral vehicles enter the nucleus during cell division. Methods Polystyrene particles with diameters of 24200 nm and carboxylate or amine surface groups, were either used as is or, alternatively, were functionalized with carboxyl-, hydroxyl- or amine- terminated poly(ethylene glycol) (PEG) and subsequently microinjected into the cytoplasm of NIH/3T3 mouse fibroblast cells. The post-mitotic locations of the particles were analyzed and compared with the locations of cytoplasmically microinjected plasmid DNA (pDNA), pDNA polyplexes or nuclear localization signal (NLS)-functionalized pDNA polyplexes. Results We observed that all polystyrene particles as well as the NLS-free polyplexes were excluded from the nucleus post-mitosis. By contrast, free pDNA and pDNA polyplexes containing an NLS accumulated in the nucleus after division. Conclusions These data suggest that biochemically specific modes of association with chromatin-associated proteins or other nuclear components are necessary for the nuclear inclusion of polyplexes and nanoparticles during mitosis. Copyright (c) 2012 John Wiley & Sons, Ltd.