Maximator® high pressure extruder

This continuous high pressure extruder (HPE) allows rapid and reproducible large-scale production of unilamellar liposomes by filter extrusion over polycarbonate membranes.

Introduction

Due to its ease, reproducibility and flexibility filter extrusion has become the method of choice for the production of well-defined liposomes over a broad size range. However, since currently available pneumatic extruders (e. g. Lipex™ EXTRUDERS (NOTHERN LIPIDS), LiposoFast™ extruder (Avestin)) have limited maximum extrusion pressures and thus product flows the extrusion method seemed to be confined to lower lipid concentrations and smaller batch sizes.
With the introduction of continuous high pressure extrusion the limitations of discontinuous pneumatic extrusion have been overcome (US Patent 6,241,967). Thus, the Maximator® high pressure extruder model HPE 12.0 - 100 allows continuous production of liposomes at extrusion pressures up to 12.0 MPa (120 bar or 1800 psi). This extruder which employs a 47 mm filter holder has been designed for the production of liposome batches between 100 ml and approximately 3 liters as required for initial formulation development and (pre-) clinical testing. Depending on the employed filter pore size, lipid composition and concentration product flows up to 1100 ml/min can be achieved. Under identical processing conditions continuous high pressure extrusion resulted in factor 3.5 (5.0 µm) or 8.2 (0.05 µm) higher product flows compared to discontinuous pneumatic extrusion which resulted in a much shorter processing time (Berger 2001). Various bilayer components, including saturated and unsaturated phospholipids, cholesterol and charged lipids can be extruded at lipid concentrations up to 400 mg/ml without congestion of membranes. This process can potentially be scaled-up to any desired level by using larger pumps and additional filter holders if needed.