Al. Bailey et Sm. Sullivan, Efficient encapsulation of DNA plasmids in small neutral liposomes inducedby ethanol and calcium, BBA-BIOMEMB, 1468(1-2), 2000, pp. 239-252
Efficient encapsulation of DNA plasmids inside small, neutral liposomes com
posed of 1,2-dioleoyl-sn-phosphatidylcholine (DOPC), DOPC/DOPE (1,2-dioleoy
l-sn-phosphatidylethanolamine) (1:1) and DOPC/DOPE/cholesterol (1:1:1) was
achieved by the addition of ethanol and calcium chloride to an aqueous mixt
ure of small unilamellar vesicles (SUVs) and plasmid. Following dialysis ag
ainst low-salt buffer, the neutral lipid complexes (NLCs) had average effec
tive diameters less than 200 nm and encapsulated up to 80% of the DNA. Opti
mum Ca2+ and ethanol concentrations for each lipid mixture were determined
by statistically designed experiments and mathematical modeling of trapping
efficiency. NLCs are unilamellar, have neutral surface potentials, and ret
ain entrapped DNA at pH 4.0 and in serum at 37 degrees C. The circulation a
nd clearance properties of the complexes following intravenous administrati
on in mice are similar to empty neutral liposomes, and the toxicity of NLCs
are expected to be significantly reduced compared to other non-viral gene-
delivery systems. The NLC encapsulation method, if it can be combined with
effective targeting and endosome-release technologies to achieve efficient
and tissue-specific transfection, may represent an important alternative to
current systemic gene therapy approaches. (C) 2000 Elsevier Science B.V. A
ll rights reserved.