What pressures and temperatures are typically required for extrusion?
A The extruder system is attached to a nitrogen gas line (see step 7 of Extruder assembly above). The pressure is increased using the regulator until the lipid is extruded. The pressure required will vary for different lipid preparations. A 50 mg/ml preparation of egg phosphatidylcholine and cholesterol (55:45, mol:mol) is typically extruded through two stacked 100 nm pore size membranes at 150-250 psi, regardless of the Extruder system used. Factors that may influence the pressure required include the source and purity of the lipids, the volume to surface area ratio, and the source, pore size, and lot number of the polycarbonate membranes. The temperature required for extrusion will reflect the gel to liquid crystalline phase transition temperature of the lipids comprising the preparation. For lipids with phase transition temperatures below room temperature, thermal regulation is not necessary. If synthetic lipids are being used, the Thermobarrel Extruder system is required. The therm
