Storage | Should always be stored in a freezer at at -40 °C or -80 °C. Upon adding water to proliposomes, liposomes are formed. |
Appearance | White lyophilized powder. Liposomes are formed upon adding water to the freeze dried proliposomes and the appearance of the formulation will be white translucent liquid. |
Description | Liposomes are extensively used to study the interaction of proteins, peptides and other molecules with the surface of a lipid membrane. One of the parameters that affects this interaction is the charge of the liposomal membrane. Liposomes are always made in aqueous environment and they are sized to the desired size in liquid state using various methods such as high pressure extrusion through nano sized pore track etch membranes. Liposome without water is meaningless. In rare occasions, liposomes are freeze dried and proliposomes are formed in the presence of a lyoprotectant such as trehalose. Using a lyoprotectant is necessary in order to maintain the size of the liposomes after rehydration. Natural PC-based Liposomes are composed of many liposomes made from phosphatidylcholine (PC) lipids that are made from natural lipids that are extracted from egg yolk and soy bean and also tissues and organs such as brain, heart and liver with and without cholesterol. Adding 30% cholesterol makes the liposomes serum stable and is necessary when the liposomes are used in the presence of serum. Liver PC also contains saturated and unsaturated lipids. Almost half of the lipids are saturated and the other half unsaturated. It is composed of 14% 16:0 lipid and 33% 18:0 lipid and 17% 18:1 lipid and 12% 18:2 lipid and 8% 20:3 lipid and 7% 20:4 lipid |
Lipid composition | Liver PC/Cholesterol (70/30 molar ratio) |
Liposome Size | 100 nm (after hydration) |
Buffer | Lyophilized Phosphate Buffered Saline, 7.4 (after hydration) |
Shelf-life | 6 months. |
Technical Notes | Liposomes are formed upon hydration of the lyophilized formulation. If the lyophilized liposomes are hydrated with solution containing a water soluble drug then a large percentage of the drug will stay outside of the liposomes and in non-encapsulated form. It is advised to use a micro dialysis cassette or a spin column using the right side beads (depending on the size of your drug) and separate the drug encapsulated liposomes from free drug and perform the drug assay in order to calculate the encapsulation efficiency. Lyophilized liposomes are mainly recommended to be used with drugs that have a short life in aqueous solution mainly due to hydrolysis. After adding the solution of the drug to lyophilized liposomes, the liposomes should be used immediately. Lyophilized Liposomes products should be used by scientists who understand liposome formulation and have the proper equipment in order to check the size, separate the non-encapsulated drug and do the proper assays. Trehalose is used as a lyoprotectant in all freeze dried liposome formulation. The size distribution after hydration of the freeze dried formulation will be around 100 nm. |
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