Tuning Macromolecular Structures of Synthetic Vectors for Gene Therapy H. Cheradame, * M. Sassatelli, C. Pomel, A. Sanh, J. Gau-Racine, L. Bacri, L. Auvray, P. Gue´gan Summary: The synthesis of triblocks poly(2-methyl-2-oxazoline-b-tetrahydrofurane- b-2-methyl-2-oxazoline) has been developed. It was shown that the technique of polymerization of the second block from the living species created on the two chain ends of poly(THF) is successful but makes the control of the size of the poly(THF) block difficult due a fast depolymerization upon the introduction of the second monomer. A purification technique was used to get rid of the possible homo- poly(2-methyl-2-oxazoline) formed. Various analytical techniques were used to characterize the behavior of the triblock and more particularly in the presence of DNA. Electrophoresis on agarose gels and neutron scattering, demonstrated that the neutral triblock does not appreciably interact with DNA. It was also shown that the triblock for which approximately half (47%) of the methyloxazoline units were transformed into ethylenimine units by hydrolysis gives only loose interactions with DNA. This result is assigned to the fact that charge density plays a major role in the interactions of positive polyelectrolytes with the negatively charged DNA. The triblock was shown being able to interact with bilayer lipid membranes mimicking cell membranes. The efficiency of the hydrolysed triblock was much higher, while the size of holes created in the membranes is not large enough to give passage to DNA. Keywords: amphiphilic triblock copolymer; bilayer lipidic membranes; DNA-copolymer mixtures; gene therapy Introduction Research in the field of macromolecular design is of primary importance in the domain of synthetic vectors for gene therapy. [1] Heavy consequences are expected as well from the therapeutic point of view as from the pharmaceutical industry economy point of view. This therapy has a long way to go due to cytoxicity problems highlighted during clinical trials. Moreover DNA delivery into the cells relies on many constraints such as condensation, complexation, endocytosis through the bilayer lipid membrane, nuclear targeting and expression in the nucleus of an eukaryotic cell. The modification of the genetic information in cells by the intro- duction of DNA requires its protection by vectors against DNAses. Usually, DNA delivery systems can be classified in two types: viral vector-mediated systems and non-viral mediated systems (mainly synthetic ones). Although viral systems are by far the most effective for gene delivery, their safety, packaging and production problems make them less attractive than synthetic vectors. Thus, synthetic materials have become most desirable tools for gene delivery in both basic research units and clinical settings. In this context more particularly polymer based synthetic vectors, offer advantages such as relative simplicity of production, safety and versatility. However, up to now their low efficiency comparatively to virus based sys- tems prevented their introduction in thera- peutic treatments. Fundamental research Macromol. Symp. 2008, 261, 167–181 DOI: 10.1002/masy.200850122 167 Mate ´ riaux Polyme ` res aux Interfaces Laboratory, UMR CNRS 7581, University of Evry, 91025 Evry, France E-mail: herve.cheradame@univ-evry.fr Copyright ß 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim