High yield incorporation of plasmid DNA within liposomes: effect on DNA integrity and transfection efficiency.

Effective use of liposomes in gene therapy requires high yield incorporation of nucleic acids within vesicles which protect their content from nuclease attack and facilitate transfection: To that end, pGL2 plasmid DNA (3.99 x 10(6) Daltons) expressing the luciferase reporter gene was incorporated quantitatively (40-92% of the DNA used) by a mild procedure into neutral and negatively or positively charged multilamellar liposomes which offered considerable protection from deoxyribonuclease attack. Smaller vesicles (210-383 nm diameter) produced from such liposomes, retained much of the original content of DNA which was still significantly inaccessible to the enzyme. Liposomal plasmid DNA was found to retain its structural integrity and to transfect cells in vitro in relation to the size and surface charge of the vesicles. Such DNA-incorporating liposome constructs could prove effective for plasmid DNA expression in vivo.