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Structure–Function Relationships of New Lipids Designed for DNA Transfection
Author(s) -
Dittrich Matthias,
Heinze Martin,
Wölk Christian,
Funari Sergio S.,
Dobner Bodo,
Möhwald Helmuth,
Brezesinski Gerald
Publication year - 2011
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201100065
Subject(s) - chemistry , differential scanning calorimetry , transfection , cationic liposome , liposome , dna , cationic polymerization , crystallography , lamellar structure , gene delivery , stereochemistry , organic chemistry , biochemistry , gene , physics , thermodynamics
Cationic liposome/DNA complexes can be used as nonviral vectors for direct delivery of DNA‐based biopharmaceuticals to damaged cells and tissues. To obtain more effective and safer liposome‐based gene transfection systems, two cationic lipids with identical head groups but different chain structures are investigated with respect to their in vitro gene‐transfer activity, their cell‐damaging characteristics, and their physicochemical properties. The gene‐transfer activities of the two lipids are very different. Differential scanning calorimetry and synchrotron small‐ and wide‐angle X‐ray scattering give valuable structural insight. A subgel‐like structure with high packing density and high phase‐transition temperature from gel to liquid‐crystalline state are found for lipid 7 ( N ′‐2‐[(2,6‐diamino‐1‐oxohexyl)amino]ethyl‐2, N ‐bis(hexadecyl)propanediamide) containing two saturated chains. Additionally, an ordered head‐group lattice based on formation of a hydrogen‐bond network is present. In contrast, lipid 8 ( N ′‐2‐[(2,6‐diamino‐1‐oxohexyl)amino]ethyl‐2‐hexadecyl‐ N ‐[(9Z)‐octadec‐9‐enyl]propanediamide) with one unsaturated and one saturated chain shows a lower phase‐transition temperature and a reduced packing density. These properties enhance incorporation of the helper lipid cholesterol needed for gene transfection. Both lipids, either pure or in mixtures with cholesterol, form lamellar phases, which are preserved after addition of DNA. However, the system separates into phases containing DNA and phases without DNA. On increasing the temperature, DNA is released and only a lipid phase without intercalated DNA strands is observed. The conversion temperatures are very different in the two systems studied. The important parameter seems to be the charge density of the lipid membranes, which is a result of different solubility of cholesterol in the two lipid membranes. Therefore, different binding affinities of the DNA to the lipid mixtures are achieved.