CHARACTERIZATION OF VECTORS FOR GENE-THERAPY FORMED BY SELF-ASSEMBLY OF DNA WITH SYNTHETIC BLOCK-COPOLYMERS

Cationic polymers can self-assemble with DNA to form polyelectrolyte c omplexes capable of gene delivery, although biocompatibility of the co mplexes is generally limited. Here we have used A-B type cationic-hydr ophilic block co-polymers to introduce a protective surface hydrophili c shielding following oriented self-assembly with DNA. Block co-polyme rs of poly(ethylene glycol)-poly-L-lysine (pEG-pLL) and xypropyl)metha crylamide-poly(trimethylammonioethyl methacrylate chloride) (pHPMA-pTM AEM) both show spontaneous formation of complexes with DNA. Surface ch arge measured by zeta potential is decreased compared with equivalent polycation-DNA complexes in each case. Atomic force microscopy shows t hat pHPMA-pTMAEM/DNA complexes are discrete spheres similar to those f ormed between DNA and simple polycations, whereas pEG-pLL/DNA complexe s adopt an extended structure. Biological properties depend on the cha rge ratio of formation. At optimal charge ratio, pEG-pLL/DNA complexes show efficient transfection of 293 cells in vitro, while pHPMA-pTMAEM /DNA complexes are more inert, Both block co-polymer-DNA complexes sho w only limited cytotoxicity. Careful selection of block co-polymer str ucture can influence the physicochemical and biological properties of the complexes and should permit design of materials for specific appli cations, including targeted delivery of genes in vivo.