L Advanced Drug Delivery Reviews 30 (1998) 97–113 Polylysine-based transfection systems utilizing receptor-mediated delivery * Wolfgang Zauner , Manfred Ogris, Ernst Wagner Institute of Biochemistry, Vienna University Biocenter, Dr. Bohrgasse 9 /3, A-1030 Vienna, Austria Received 1 July 1997; accepted 30 July 1997 Abstract Receptor-mediated gene transfer is a promising gene delivery technique. It employs a DNA-binding polycation, such as polylysine, to compact plasmid DNA to a size that can be taken up by cells ( , 100–200 nm). To allow internalization by receptor-mediated endocytosis, cell binding ligands, such as asialoglycoproteins or galactose for hepatocytes, anti-CD3 and anti-CD5 for T-cells, and transferrin, have been covalently attached to polylysine. Intracellular barriers for successful gene transfer include release of DNA complexes from endosomes or lysosomes, nuclear import of DNA complexes, and disassembly of the DNA–polylysine particles. Release of particles from internal vesicles has been achieved by the addition of lysosomotropic agents or glycerol to the transfection medium, or by the incorporation of endosomolytic compounds, such as viruses or membrane active peptides. This technique has already been used to transfect certain organs in vivo, including liver and lung.  1998 Elsevier Science B.V. Keywords: Polylysine; Receptor-mediated gene transfer; DNA condensation; Endosomal release; In vitro; In vivo; Nuclear trafficking Contents 1. Introduction ............................................................................................................................................................................ 98 2. Chemistry ............................................................................................................................................................................... 99 3. DNA condensation .................................................................................................................................................................. 100 4. Cellular aspects of gene transfer ............................................................................................................................................... 101 4.1. Biological effects of polylysine ......................................................................................................................................... 101 4.2. Uptake of DNA particles .................................................................................................................................................. 103 4.2.1. Ligand–polylysine–DNA complexes ....................................................................................................................... 103 4.2.2. Polylysine–DNA complexes in combination with lipids ............................................................................................ 104 4.3. Endosomal release ........................................................................................................................................................... 105 4.3.1. Addition of lysosomotropic agents .......................................................................................................................... 105 4.3.2. Addition of glycerol ............................................................................................................................................... 105 4.3.3. Incorporation of viruses .......................................................................................................................................... 105 4.3.4. Membrane-disruptive peptides ................................................................................................................................ 106 4.4. Nuclear trafficking of DNA (complexes) ............................................................................................................................ 106 4.5. Complex disassembly ....................................................................................................................................................... 106 5. In vivo gene transfer ................................................................................................................................................................ 107 6. Conclusions and prospects ....................................................................................................................................................... 108 Acknowledgements ...................................................................................................................................................................... 108 References .................................................................................................................................................................................. 108 * Corresponding author. 0169-409X / 98 / $19.00  1998 Elsevier Science B.V. All rights reserved. PII S0169-409X(97)00110-5