IN-VITRO MYOTOXICITY OF SELECTED CATIONIC MACROMOLECULES USED IN NONVIRAL GENE DELIVERY

Purpose. Cationic lipid/DNA complexes have been proposed as a method o f in vivo gene delivery via intravenous or intramuscular injection. A concern with using these polycationic molecules is whether they are as sociated with tissue toxicity at the injection site. Therefore, the ob jective of these studies was to investigate the myotoxic potential of selected non-viral gene delivery macromolecules (e.g., cationic lipids and polymers) with and without plasmid DNA (pDNA) in vitro. Methods. Myotoxicity was assessed by the cumulative release of creatine kinase (CK) over 90 minutes from the isolated rodent extensor digitorum longu s muscle into a carbogenated balanced salt solution (BBS, pH 7.4, 37 d egrees C) following a 15 mu L injection of the test formulation. Pheny toin (Dilantin(R)) and normal saline served as positive and negative c ontrols, respectively. Results. The myotoxicity of plasmid DNA (pDNA, similar to 5000bp, 1 mg/ml) was not statistically different from norma l saline. However, the myotoxicity of Dilantin(R) was 16-times higher than either normal saline or pDNA (p < 0.05). Cationic liposomes were found to be less myotoxic than polylysine and PAMAM dendrimers. Polyly sine's myotoxicity was found to be dependent upon concentration and mo lecular weight. The myotoxicity of formulations of cationic liposomes( s), lower molecular weight polylysine (25,000) and higher concentratio n of PAMAM dendrimers with pDNA were found to be statistically less si gnificant than those formulations without pDNA. Conclusions. The catio nic liposomes were less myotoxic compared to the dendrimers and polyly sine. Myotoxicity was dependent upon the type of cationic lipid macrom olecule, concentration, molecular weight and the presence of pDNA. A p ossible explanation for this reduced tissue damage in cationic lipids complexed with pDNA is that the formation of complex reduces the overa ll positive charge of the injectable system resulting in less damage.