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.

Function of the Maximator® high pressure extruder:

The Maximator® (Fig. 1) consists of a thermostatable glass supply vessel (1) directly connected to a pneumatic high pressure piston pump (2). The latter is driven by either oxygen or nitrogen at pressures below 0.5 MPa (5 bar or 75 psi). The propellant gas does not come into contact with the liposome suspension. The resulting operating (extrusion) pressure - which can be adjusted via the reduction valve in the control device for the propellant gas (3) - can be as high as 12 MPa (120 bar or 1800 psi) with the current equipment. The outlet side of the pump is connected to a filter holder (5) via a 3-way vent (4).

Maximator® model HPE 12.0 - 100

Fig. 1: Maximator® model HPE 12.0 - 100, continuous high pressure extruder.
Extrusion with this apparatus is performed by introduction of MLVs into the supply vessel. The high pressure piston pump will pressurize the liposome suspension in the pump head and finally force it through the membranes in the filter holder. Typically sequential extrusion through two double stacked (sandwiched) membranes of decreasing pore size (e. g. 1.0, 0.2 and 0.05 µm) is performed. Normally, polycarbonate membranes (e. g. Nucleopore™) with pore sizes between 5 and 0.03 µm are used. In Fig. 2 the impact of the employed filter pore size on the size of the resulting liposomes is shown. The extruded vesicles can either be directly recirculated into the supply vessel to achieve automatic continuous extrusion or first be collected in a separate vessel to determine an exact number of filter passages. More details on the continuous high pressure extrusion process can be found in the papers provided in the reference list (e. g. Schneider 1994 + 1995, Berger 2001).

Mean diameter of continuously extruded liposomes as a function of filter pore size (Schneider 1994)

Fig. 2: Mean diameter of continuously extruded liposomes as a function of filter pore size (Schneider 1994)
Lipid composition: SPC/CH/SPG (6:3:1), 50 mg/g lipid, 100 ml batch (n=1)