Liposomes are important vehicles for delivering drugs, and other biologically active compounds, with selectivity and a reduction of side effects compared with conventional methods of drug delivery. In this article Biopharma Process Systems talks about the advantages of liposomes and comments on how how High Pressure Homogenisation can help your projects.
The advantage of liposomes lies in the lipid bilayer itself as this mimics the biomembrane of cells and organelles such as the small vesicles they resemble. A liposome vesicle is a natural shape for phospholipids to obtain, with the hydrophobic tails of the two layers interacting, producing an aqueous centre to the liposomes and a hydrophilic surface. This then permits fusion of the liposome vesicle with the cell’s plasma membrane and thus release of the drug straight into the cell’s interior.
Any method that allows for greater reliability, repeatability and controllability of liposome production is potentially therefore a great boon, which is where High Pressure Homogenisation (HPH) enters the picture. HPH is a method for reducing lamellarity and the size of liposome vesicles increasing physical stability, preventing aggregation and sedimentation and the subsequent loss of liposomes from the bloodstream.
Homogenisation at high pressure reduces the number of vesicle aggregations and decreases the number of multi-lamellar liposomes to produce a uni-lamellar mix. After a single processing cycle there is a significant drop in vesicle size with approximately only one concentric lamellae/vesicle. Regular process cycling will then ensure that the distribution is tight. The resulting filterable preparation can also be passed through microbe-retentive filters.
HPH also provides an opportunity for the liposome loading required for drug and pharmaceutical delivery – encapsulating the active, hydrophilic, substances within the vesicle’s aqueous core. Amphiphilic and lipophilic compounds can also be encapsulated into liposomal vesicles using HPH.
The compound is dissolved in an organic solvent with lipids and hydrated upon solvent removal pre-homogenisation. Abraxane, a lipid drug based drug, made by Abraxis Bioscience Inc. has been modified using HPR as has Gemcitabine, marketed as Gemzar by Eli Lilly. Liposomes and HPR are really delivering on all counts.