SPERMIDINE CONDENSED DNA AND CONE-SHAPED LIPIDS IMPROVE DELIVERY AND EXPRESSION OF EXOGENOUS DNA TRANSFER BY LIPOSOMES

A new liposome system containing spermidine-condensed DNA and negative cone-forming lipids designed to improve gene delivery and expression is described. The compacted nature of condensed DNA forms permitted a higher extent of encapsulation of DNA in liposomes. These vesicles con tained fusogenic cone-shaped lipids to increase fusion between liposom es and membranes to enhance the amount of DNA delivery into the cells. In addition, the insensitivity of condensed DNA forms to endonuclease s and restriction enzymes, as well as their higher activity in both re plication and transcription, improve foreign DNA expression. These imp rovements in condensed DNA encapsulation in liposomes, transfer into t he cells, and DNA expression increase the number of transfected cells and produce a higher level of gene expression in most transfected cell s. This is reflected in the 60-fold cell culture transfection increase compared with traditional liposome transfection systems. This liposom e system does not cause any apparent damage to the transfected cells; furthermore, the liposomes are small, 400-500 nm, and have negative su rface charges that can prolonge their circulation half-lives in vivo, permitting their use for in vivo gene therapy applications.