Cholesterol domains in cationic lipid/DNA complexes improve transfection

Area of Science:

• Lipid-based drug delivery systems
• Biophysical characterization of lipid formulations
• Gene delivery and transfection technologies

Background:

• Cationic lipid DOTAP is a key component in gene delivery formulations.
• Cholesterol's role in liposome stability and function is well-established.
• Serum presence significantly impacts the efficacy of lipid-based gene delivery systems.

Purpose of the Study:

• To investigate the interaction between DOTAP and cholesterol in high cholesterol formulations.
• To correlate the presence of cholesterol domains with transfection efficiency in serum.
• To elucidate the mechanism behind enhanced transfection in high cholesterol formulations.

Main Methods:

• Differential scanning calorimetry (DSC) to analyze lipid-cholesterol interactions.
• Liposome preparation and characterization at varying cholesterol concentrations.
• Transfection efficiency assays in the presence of serum.
• Albumin binding studies to assess protein interaction.

Main Results:

• Formulations with >66 mol% cholesterol exhibit calorimetric transitions for anhydrous cholesterol domains.
• Enthalpy of cholesterol transition increases with cholesterol content, indicating domain formation.
• High cholesterol formulations show greater transfection efficiency and serum resistance.
• Cholesterol domains in lipid/DNA complexes do not bind albumin, suggesting a mechanism for enhanced transfection.

Conclusions:

• Anhydrous cholesterol domains form in DOTAP formulations above 66 mol% cholesterol.
• These cholesterol domains enhance gene transfection efficiency in serum-containing environments.
• The enhanced transfection is likely due to cholesterol domains preventing protein binding and facilitating membrane fusion.