Liposome constructs

Figure 22.5 The three fatty acid components commonly used in liposome construction.

Figure 22.15 Glycolipid components included in liposome construction may be used to couple antibody molecules by using conjugates of lectins with the proper specificity for binding the sugar groups.

However, since many of the traditional biotinylation reagents, such as NHS-LC-biotin contain hydrophobic spacers, their use with amphipathic liposomal constructions may not be entirely appropriate. A better choice may be to use a hydrophilic PEG-based biotin compound that creates a water-soluble biotin modification on the outer aqueous surface of the liposome bilayer. Biotinylation reagents of this type are discussed in Chapter 18, Section 3. 

Prepare a biotinylated liposome construct by first dissolving in chloroform, the lipids DMPC cholesterol dicetylphosphate (Sigma) at mole ratios of 5 4 1, and adding to this solution 0.1 mol percent B-PE. Larger mole ratios of B-PE to total lipid may result in nonspecific aggregation of liposomes in the presence of avidin. Maintain all lipids under an inert atmosphere to prevent oxidation. 

Prepare liposomes containing PE by any desired method. For instance, the common recipe mentioned in Section 1 (this chapter) that involves mixing PC cholesterol PG PE in a molar ratio of 8 10 1 1 may be used. Thoroughly emulsify the liposome construction to obtain a good population of SUVs. The final liposome suspension should be in 20mM sodium phosphate, 0.15M NaCl, pH 7.2. Adjust the concentration to about 5 mg lipid/ml buffer. 

Figure 3 Design of a diepitope liposomal construct. Small unilamellar liposomes (PC/PG/Chol 55/25/50 molar ratio diameter 100nm) containing 10mol% of bromo-acetyl l,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine and 10mol% of the thiol-reactive lipopeptide adjuvant anchor Pam3CysAlaGly-Mal were reacted, at 25°C successively at pH 6.5, with the T-helper epitope QYI, derivatized with a C-linker at its N-terminus, followed at pH 9.0 by the B-epitope TPE derivatized with a CG linker at its N-terminus. Abbreviations PC, phosphatidylcholine PE, phosphatidylethanolamine SUV, small unilamellar vesicles. Source From Refs. 11, 20, 21.

Frisch B, Roth A, Schuber F. Synthetic peptide-based highly immunogenic liposomal constructs. Meth Enzymol 2003 373 51. 

Boeckler C, et al. Design of highly immunogenic liposomal constructs combining structurally independent B cell and T helper cell peptide epitopes. Eur J Immunol 1999 29 2297. 

Prepare a 5 mg/ml liposome construction in 20 mM sodium phosphate, 0.15 M NaCl, pH 7.4, containing, on a molar ratio basis, a mixture of PC cholesterol PG other glycolipids of 8 10 1 2. The other glycolipids that can be incorporated include phosphatidyl inositol, lactosylceramide, galactose cerebroside, or various gangliosides. Other liposome compositions may be used, for example, recipes without cholesterol, as long as a periodate-oxidizable component... 

Figure 23 (A) Whitesides s sphingosine-inspired glycolipid 38. (B) Bednarski s cross-linkable liposomal constructs 39 and...

FIGURE 20.8 Calibration of the pH measurement. R, the ratio of tetramethylrhodamine and fluorescein fluorescence, versus the pH for liposomes constructed with internal pH values ranging from 3 to 7. The average ratio and standard deviation is shown with a marker and bars at 7 pH values. The calibration curve represents a quadratic model and was determined by multiple regression analysis. (Reprinted from Chen, Y. and Arriaga, E. A., Anal. Chem., 78, 821, 2006. Copyright 2006. With permission from American Chemical Society.)... 

Major Applications Sensors, - photoconductors, copying materials, rubber, 3- 5 body fluid testing, determination of calcium, magnesium, tin, method for measuring urea nitrogen, liposomal construct for diagnostic use, cardiovascular disease, antibacterial agent Safety/Toxicity In vitro toxicity ... 

Polymerized liposomes are being actively investigated for their use in controlled release applications such as drug delivery and biosensors.(24) At present, in order to obtain liposomes which have the release characteristics required for a specific need, the amphiphiles used to construct the liposome as well as the precise mixture of amphiphiles required must be designed and synthesized from start each time. This is a time consuming and expensive process. One of our main objectives in this research is to design a series of liposomes constructed from diacetylenic and short chain spacer lipids with predictable leak rates which could be utilized in controlled release applications. In order to accomplish this goal, it was necessary to characterize both the effect of spacer lipid on microstructure formation properties and to determine the methods that could be used to... 

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