POPC:Chol:POPG Liposomes Containing Dextran-FITC Dye
Fluorescent leakage assay is a method that is extensively used for measuring the disruption of the liposomal membrane due to various external triggers such as interaction of molecules (e.g. peptides, proteins, detergents and etc.) with the surface of the liposomes. Liposomal membrane can also be disrupted when external energy is given to the system such as exposure of liposomes to sonic sound, mechanical pressure or heat.
When liposomes are disrupted, their content will leak out of the liposomes. If you investigate the old literature, you will realize that in a large percentage of fluorescent leakage assay, the experiments involve encapsulating a self quenching concentration of fluorescent dyes such as calcein and carboxyfluorescein. The problem with calcein and carboxyfluorescein is that the liposomes have to be made very fresh and be used right away. These molecules have a tendency to leak out quickly in the absence of any trigger especially when unsaturated lipids are used. This will cause the assay to be less sensitive and the data not to be reproducible.
These days, a very large selection of fluorescent dyes are commercially available which can be encapsulated or incorporated into the lipid bilayers of the liposomes. Fluorescent dextran molecules are excellent candidates for leakage assay. Dextran molecules can be tagged with various self-quenching fluorophores such as FITC. Dextran molecules comes in different sizes and therefore they are very ideal candidates for studying the size of the pore that is formed on the liposome membrane. They can also be used for studies that involve the total collapse of liposomal structure as well. The approximate Stokes’ radii for FITC-dextrans are given in the table below.
|Molecular Weight (MW) of Dextran (Dalton)||Approximate Stokes’ Radius (Angstrom)|
For example, if you observe a leakage using 4,000 dextran-FITC and you do not detect any leakage using 10K dextran FITC then it simply shows that the radius of the pore is larger than 14 Å but smaller than 23 Å. If your experiment involves the total collapse of the structure of the liposomes, then any size dextran-FITC can be used. Unlike calcein, dextran-FITC does not leak out of the liposomes due to its size.
POPC:Chol:POPG Liposomes Containing Dextran-FITC Dye
|Lipid Composition||Concentration (mg/ml)||Concentration (mM)||Molar Ratio|
|1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (sodium salt)||0.51||0.66||1|
|Total||7.16 mg/ml||10 mM|
|Fluorescent Dye||Excitation/Emission (nm)||Molecular Structure|
|Buffer and Liposome Size||Specification|
|Buffer||Phosphate Buffered Saline*|
|Liposome Size||100 nm|
|* If you prefer different buffers, please specify in your order.|
- Liposomes are unilamellar and sized to 100 nm. If you need them to be made in another size, then you should mention that at the time of ordering. Unilamellar liposomes can be made in 50 nm and 200 nm sizes. Liposomes that are larger than 200 nm are multilamellar structure.
- Liposomes are made in PBS buffer at pH 7.4 but it can be made in any other buffer of your choice. You can specify your buffer at the time of ordering.
- Liposomes are made in degassed buffer that is purged with argon to avoid oxidation of the unsaturated phospholipids.
- Liposomes are made under sterile condition.
- Liposomes are unilamellar and therefore due to their small size they will not settle in the bottom of the vial.
- If you need to take multiple aliquots out of the vial, for use over a period of time, then it is advised to take extreme care in not contaminating the vial. It is recommended to handle the vial under a sterile hood to maintain the sterility of the product.
- Liposomes should never be frozen. Ice crystals that form during freezing will rupture the lipid membrane of the liposomes and change the size the liposomes particles.
- Liposomes should be kept in refrigerator at 4°C in order to avoid the hydrolysis of the liposomes.
- Liposomes should be kept at 4°C and NEVER be frozen.
Liposome containing dextran-FITC dye formulation is a yellow translucent liquid. Usually due to the small size of liposomes no settling will occur in the bottom of the vial. The liposomes are packaged in an amber vial.
- All liposome based formulations are shipped on blue ice at 4°C in insulated packages using overnight shipping or international express shipping.
- Liposomes should NEVER be frozen. Ice crystals that form in the lipid membrane can rupture the membrane, change the size of the liposomes and cause the encapsulated drug to leak out. Liposomes in liquid form should always be kept in the refrigerator.
- Clients who order from outside of the United States of America are responsible for their government import taxes and customs paperwork. Encapsula NanoSciences is NOT responsible for importation fees to countries outside of the United States of America.
- We strongly encourage the clients in Japan, Korea, Taiwan and China to order via a distributor. Tough customs clearance regulations in these countries will cause delay in custom clearance of these perishable formulations if ordered directly through us. Distributors can easily clear the packages from customs. To see the list of the distributors click here.
- Clients ordering from universities and research institutes in Australia should keep in mind that the liposome formulations are made from synthetic material and the formulations do not require a “permit to import quarantine material”. Liposomes are NOT biological products.
- If you would like your institute’s FedEx or DHL account to be charged for shipping, then please provide the account number at the time of ordering.
- Encapsula NanoSciences has no control over delays due to inclement weather or customs clearance delays. You will receive a FedEx or DHL tracking number once your order is confirmed. Contact FedEx or DHL in advance and make sure that the paperwork for customs is done on time. All subsequent shipping inquiries should be directed to Federal Express or DHL.
Storage and Shelf Life
Liposomes containing dextran-FITC dye should always be stored at in the dark at 4°C, except when brought to room temperature for brief periods prior to animal dosing. DO NOT FREEZE. ENS is not responsible for results generated by frozen product.
Liposomes containing dextran-FITC dye are made on daily basis. The batch that is shipped is manufactured on the same day. It is advised to use the products within 60 days of the manufacturing date.