Gene delivery using liposome technology

Development of more reliable liposomal formulations and preparation methods which can be used for gene therapy instead of commonly used viral vectors is expected. We have already developed the freeze-dried empty (non-drug-con taining) liposomes (FDEL) method for mass-production of liposomal products. After these freeze-dried empty liposomes are rehydrated with aqueous drug solutions, many kinds of drugs can be encapsulated highly efficiently, and particle size can be controlled well. This study evaluated the usefulness o f this FDEL method for preparation of liposomes containing DNA with a parti cular attention to the stability of DNA. When the liposomes were prepared b y the conventional lipid-film method on a relatively large scale with use o f a Potter-homogenizer (a teflon homogenizer), significant degradation and conformational change of DNA was observed during homogenization. Loss of DN A was also significant after extrusion for sizing and sterilization; residu al DNA in the final preparation was hardly detected. When the FDEL method w as used, on the other hand, no degradation, conformational change or loss o f DNA was observed, and particle size was easily controlled. Moreover, ther e was no significant difference in luciferase activity between the lipid-hi m method used on a small scale with use of a vortex mixer and the FDEL meth od after transfection of tumor cells (HRA, HEC-1A and Colo320DM) by the lip osomes containing DNA (PGV-C). These findings suggest that the FDEL method is very useful for preparation of liposomes containing DNA. (C) 1999 Elsevi er Science B.V. All rights reserved.