Liposome Extruders

Liposome extruders are mainly used for the liposome formulation and achieving uniform size distributions. It is an ideal instrument to generate nanoscale liposome formulations, and to prepare exosomes and artificial cell membranes. By utilizing the tracked-etched filter membranes, the liposome extruders are capable of capturing large particles, precipitation and achieving sterile filtration.^[1][2]

Application[edit]

Research and Development for the liposomal drug delivery system, vaccine, gene delivery, and cosmetics.

Working Principles[edit]

A liposome is a spherical-shaped vesicle composed of phospholipid bilayers.^[3] Phospholipid bilayers are critical components of cell membranes, with hydrophilic and hydrophobic properties. In an aqueous solution, the hydrophobic ends tend to bind to each other, and spontaneously form small spherical liposomes. The liposome extruder is designed for the preparation of liposomes. It is easy to use, and has high precision particle size control ability with narrow distributions and satisfactory repeatability.^[4] So far it has been widely used in the preparations of complex injectable products, such as paclitaxel liposomes, adriamycin liposomes, amphotericin B liposomes, doxorubicin liposomes, cytarabine liposomes, and irinotecan liposomes.

Figure 1 Gene delivery liposome with phospholipid bilayers

Liposome extrusion technology is employing the structural and performance characteristics of liposomal phospholipid bilayers.^[5] When the operational temperature is slightly above the phase transition temperature of phospholipids, the large vesicles of liposomes will pass through polycarbonate membranes with specific pore sizes by a certain external extrusion force. The large particle size liposome or multiple compartments liposomes are rapidly repolymerized into smaller-size liposomes after being ruptured by the shear of membrane pores.^[6] Since the pore size of polycarbonate membrane is fixed (e.g., 50nm, 100nm, 200nm, 400nm, 1um, etc.), and the polycarbonate extrusion membrane features vertical and uniform nano pore distributions on the membrane surface, when the large vesicles pass through the membrane with a specific nano pore size several times, the sample is extruded to the uniform size decided by the pore.^[7]

Common Types of Liposome Extruders[edit]

Liposome extruders can be classified into three categories: hand driven liposome extruders, jacketed liposome extruders, and online liposome extruders. Each category is based on its different power sources.

Hand Driven Liposome Extruders[edit]

The hand driven liposome extruders are capable of processing the sample volume from 0.25mL to 2.5mL, which is suitable for mini sample volume applications during the experimental phase. It is operated by simply pushing the plunger manually. There are two types of hand driven extruders: extruders under ambient temperature, and extruders with jacketed option. The hand driven liposome extruders with cooling jacket are designed for those extrusion conditions to control the sample temperature.

Figure 2 Hand Driven Liposome Extruders

Jacketed Liposome Extruders[edit]

The jacketed liposome extruders have a wide range of processing capacities, from sample volume 2mL to 3L depending on the models. It is suitable for lab scale and pilot scale applications. It is driven by compressed nitrogen cylinder. Most of the jacketed liposome extruders are designed with jacketed barrel to achieve the temperature control of the sample.^[8]

Figure 3: Jacketed Liposome Extruders

Online Liposome Extruders[edit]

Online liposome extruders are available for the processing capacity from 2mL to 20L depending on the different models. These extruders are more suitable for pilot scale applications. It is powered by a high-pressure pump unit or other production equipment.

Figure 4: Online Liposome Extruders

Multiple Liposome Extruders System[edit]

The multiple liposome extruders system is able to process the volume from 1L to 200L. It features both the temperature and pressure sensors in the product line, and a control panel to control the production for liposomes.

Figure 5: Multiple Liposome Extruders systems with liposome extruding control panel

References[edit]