Clipos™ PDP Liposomes, Non PEGylated

Catalog:CDEIMS-1513

Unit Size:2 mL, 5 mL

Specifications

Description	The liposomes containing pyridyldithiopropionate (PDP) lipids are used to conjugate proteins, antibodies and other molecules containing the reactive moiety. PDP lipids are not as widely used as maleimide lipids, but they do have their own niche application. The PDP group contains disulfide, which can react with sulfhydryl or thiolated proteins/antibodies. Therefore, PDP-functionalized liposomes can be used in two ways: A) maleimide-modified antibody to a PDP-modified liposome; B) thiol-modified antibody to a PDP-modified liposome.
Lipid composition	L-a-PC/Cholesterol/1,2-Dioleoyl-sn-glycero-3-phosphoethanolamine-N-[3-(2-pyridyldithio)propionate] (69/30/1 molar ratio)
Liposome Size	100 nm
Lipid Mass Concentration	14.82 mg/mL
Lipid Molar Concentration	22.45 mM
Functional Group	PDP
Appearance	White translucent liquid made of nano size unilamellar liposomes. 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.
Buffer	Phosphate Buffered Saline, pH 7.4
Storage	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. If the suspension is frozen, the encapsulated drug can be released from the liposomes thus limiting its effectiveness. In addition, the size of the liposomes will also change upon freezing and thawing.
Shelf-life	4 months.
Technical Notes	After conjugation reactions, liposomes containing excess maleimide or thiol groups may exhibit undesirable qualities, such as aggregation, reactions in vitro and in vivo, and immunogenicity. These reactive moieties can be quenched with reagents containing iodo-, maleimide, or sulfhydryl groups, where appropriate. This is likely to be a particularly serious problem for thiolated liposomes. Therefore, it is recommended that the antibody to be thiolated in order to generate the appropriate reactive entities for the final conjugation reaction. In order to prevent oxidation of sulfhydryl on antibody and formation of disulfide bridge, the coupling reaction must be performed under an inert atmosphere such as argon or nitrogen. To set up a inert gas chamber we recommend using Aldrich®-Atmosbag with is a flexible, inflatable polyethylene chamber with built-in gloves which is a portable and inexpensive alternative to laboratory glove box. Maleimide group on lipid is highly sensitive of alkaline pH and it will hydrolyze rapidly at higher pH. Experimental investigations have been shown that in alkaline condition (pH > 7.5), maleimide and its derivatives are hydrolyzed to a non-reactive maleamic acid (see the figure below). This instability should be considered in any quantitative procedures, such as coupling with sulfhydryl groups. Therefore, it is very important to make sure that the pH of the reaction with stay between 6.5 and 7 during the entire process. If your goal is to conjugate a thiolated protein/antibody containing reactive sulfhydryl to liposomes to form an immunoliposome, it is recommended to use liposomes containing maleimide reactive lipids. The amount of the maleimide-activated protein/antibody bound per liposome in Method A depends on the number of free thiols on the liposome surface (formed in step 1) and the reaction efficiency increases with increasing PDP/mAb molar ratio in the incubation mixture. If you are using a ligand or peptide that is hydrophobic then it is recommended to solubilize it in DMSO or DMF and then add the buffer to it. It is recommended not to use more than 5% volume of DMSO or DMF in the solution. DMF and DMSO are both compatible with liposomes and they are also miscible in water. Other organic solvent such as ethanol and chloroform are not compatible with liposomes and will cause the liposomes to lyse. If you end up using DMSO or DMF then after the conjugation reaction is done, you need to remove DMSO and DMF from the liposomes. In order to do that, you need to use a dialysis cassette that is made from REGENERATED CELLULOSE MEMBRANE. NOTE: Not all membranes are compatible with DMF and DMSO. We recommend using a Slide-A-Lyzer™ MINI Dialysis Device with MWCO of 2K made from regenerated cellulose membrane manufactured by ThermoFisher. After DMSO or DMF is removed you can use Float-A-Lyzer® dialysis device for the final step of cleaning up the prep.