Cholesterol domains in cationic lipid/DNA complexes improve transfection.
The interaction between the cationic lipid DOTAP and cholesterol is examined in high cholesterol formulations by differential scanning calorimetry (DSC). Preparation of liposomes above 66 mol% cholesterol results in formulations that exhibit a calorimetric transition for anhydrous cholesterol at 38-40 degrees C. The enthalpy of this transition progressively increases at higher cholesterol contents, and is not detected below 66 mol% cholesterol. Furthermore, the enthalpy changes indicate that the composition of the non-domain forming portion containing DOTAP saturated with cholesterol is relatively constant above 66 mol% cholesterol. Greater transfection efficiency in the presence of 50% serum is observed at the formulations with high cholesterol contents where anhydrous cholesterol domains are detected by DSC. Although formulations possessing higher cholesterol exhibited a greater resistance to serum-induced aggregation, maintenance of small particle size does not appear to be responsible for the enhanced transfection efficiency. Additional studies quantifying albumin binding suggest that cholesterol domains in the lipid/DNA complex do not bind protein, and this may enable these moieties to enhance transfection by facilitating membrane fusion.
Xu
Long
L
School of Pharmacy, University of Colorado Denver, 4200 E. Ninth Avenue, Denver, Colorado, USA. long.xu@uchsc.edu
Anchordoquy
Thomas J
TJ
D002152:Calorimetry, Differential Scanning; D002460:Cell Line; D002784:Cholesterol / Q000737:chemistry*; D004247:DNA / Q000737:chemistry*; D005229:Fatty Acids, Monounsaturated / Q000737:chemistry; D005456:Fluorescent Dyes / Q000737:chemistry; D006801:Humans; D008055:Lipids / Q000737:chemistry*; D008081:Liposomes / Q000737:chemistry; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D014162:Transfection / Q000379:methods*
D005229:Fatty Acids, Monounsaturated; D005456:Fluorescent Dyes; D008055:Lipids; D008081:Liposomes; D000644:Quaternary Ammonium Compounds; D004247:DNA; D002784:Cholesterol; C070046:1,2-dioleoyloxy-3-(trimethylammonium)propane