A versatile system for receptor-mediated gene delivery permits increased entry of DNA into target cells, enhanced delivery to the nucleus and elevated rates of transgene expression

We have developed a method for stabilisation of polyelectrolyte gene delive ry vectors by crosslinking their surfaces with biodegradable multivalent co polymers based on N-(2-hydroxypropyl)methacrylamide (HPMA). The resulting n ano-particulate vectors resist attack by serum proteins and can be modified for cell-specific delivery by incorporation of targeting ligands onto the polymer coating. Here we show that vascular endothelial growth factor(VEGF) , transferrin and basic fibroblast growth factor (bFGF) can each be linked to polyHPMA-coated poly(L-lysine)/DNA complexes. All ligand-targeted comple xes demonstrated increased uptake into receptor-positive cells (measured us ing plasmids containing P-32-dCTP), that could be antagonised with excess f ree ligand. Targeted complexes also showed increased transfection, resistan t to inhibition by serum, suggesting the possibility of effective applicati on in vivo. Analysis using fluorescence microscopy confirmed enhanced uptak e of ligand-targeted complexes (using Texas Red-labelled plasmid DNA), alth ough VEGF- and transferrin-targeted complexes were restricted to cytoplasmi c or perinuclear distributions. In contrast, bFGF-targeted complexes showed efficient delivery into the nucleus, with accumulation of more than 100000 plasmids per cell within distinct intranuclear compartments. This method p ermits versatile targeting of genes to selected cells and may also permit m anipulation of intracellular trafficking. If should find several important applications in gene delivery systems both in vitro and in vivo.