Emulsion formulations as a vector for gene delivery in vitro and in vivo

For successful gene therapy, it is necessary to develop vectors capable of efficiently introducing genetic materials into target cells. Various techniques for transgene delivery have been developed, among which cationic liposome-mediated delivery is widely accepted. DC-Chol/DOPE cationic liposomes, synthesized in our laboratory, have been successfully used as a vector in clinical trials for treating melanoma and cystic fibrosis. Formation of large aggregates at higher concentration and serum sensitivity are major drawbacks of the cationic liposome-mediated delivery system. To overcome these problems, we have developed cationic emulsion formulations. By the addition of non-ionic surfactant to the formulation, the formation of large aggregates was prevented and stable DNA/cationic emulsion complexes were obtained. These complexes transfected different cell lines with an equivalent or higher efficiency compared to the cationic liposomes, and possessed no serum sensitivity. We have also developed reconstituted chylomicrons as an in vivo gene transfer vector to the liver. The hydrophobic complex of DNA and TC-Chol was extracted by chloroform and emulsified with triglyceride, PC, lyse PC, Chol and Chol oleate. More than 60% of the complex was incorporated into the reconstituted chylomicrons. Portal vein injection of the DNA-incorporated reconstituted chylomicrons into mice produced a high amount of gene product in the liver. Emulsion formulations appeared to have more favorable physical and biological activities than traditional cationic liposomes as a gene delivery system in vivo.