Characterization, liposomes

List of Parameters and Common Techniques for Characterizing Liposomes... 

Biltonen, R. L., and Lichtenberg, D. (1993), The use of differential scanning calorimetry as a tool to characterize liposome preparations, Chem. Phys. Lipids, 64,129-142. 

Phospholipid molecules form bilayer films or membranes about 5 nm in thickness as illustrated in Fig. XV-10. Vesicles or liposomes are closed bilayer shells in the 100-1000-nm size range formed on sonication of bilayer forming amphiphiles. Vesicles find use as controlled release and delivery vehicles in cosmetic lotions, agrochemicals, and, potentially, drugs. The advances in cryoelec-tron microscopy (see Section VIII-2A) in recent years have aided their characterization [70-72]. Additional light and x-ray scattering measurements reveal bilayer thickness and phase transitions [70, 71]. Differential thermal analysis... 

A large variety of drug delivery systems are described in the literature, such as liposomes (Torchilin, 2006), micro and nanoparticles (Kumar, 2000), polymeric micelles (Torchilin, 2006), nanocrystals (Muller et al., 2011), among others. Microparticles are usually classified as microcapsules or microspheres (Figure 8). Microspheres are matrix spherical microparticles where the drug may be located on the surface or dissolved into the matrix. Microcapsules are characterized as spherical particles more than Ipm containing a core substance (aqueous or lipid), normally lipid, and are used to deliver poor soluble molecules... 

In vivo reproducible results can only be achieved if the liposome-drug or -antigen combinations are thoroughly characterized upon preparation in terms of their physical and chemical properties and, besides, if the stability during storage is ensured. In this chapter both the pharmaceutical (preparation, characterization, and stability) aspects and the therapeutic potentials and limitations of drug and antigen delivery with liposomes will be discussed. 

Crommelin, D. J. A., and Storm, G. (1987). Pharmaceutical aspects of liposomes Preparation, characterization, and stability, in Controlled Drug Delivery (B. W. Muller, ed.), Wissenschaftliche Verlagsgescellschaft mbH, Stuttgart, pp. 80-91,... 

Guiot, P., Baudhuin, P., and Gotfredsen, C. (1980). Morphological characterization of liposome suspensions by stereological analysis of freeze fracture replicas from spray frozen samples, J. Microsc., 120, 159-174. 

H. E., and Crommelin, D. J. A., Characterization of liposomes (1987). The influence of extrusion of multilamellar vesicles through polycarbonate membranes on particle size, particle size distribution and number of bilayers, Int. J. Pharm.. 35, 263-274. 

Lichtenberg, D., and Barenholz, Y. (1988). Liposomes Preparation, characterization and preservation, in Methods of Biological Analysis. Vol. 33 (D Glick, ed.), John Wiley and Sons, New York, pp. 337-461. 

Szoka, F., and Papahadjopoulos, D. (1981). Liposomes Preparation and characterization, in Liposomes From Physical Structure to Therapeutic Applications (C. G. Knight, ed.), Elsevier, Amsterdam, pp. 51-82. 

Frostell-Karlsson, A., Widegren, H., Green, C. E., Hamalainen, M. D., Westerlund, L., Karlsson, R., Fenner, K., Van De Waterbeemd, H. Biosensor analysis of the interaction between drug compounds and liposomes of different properties a two-dimensional characterization tool for estimation of membrane absorption. /. Pharm. Sci. 2005, 94, 25-37. 

S Vemuri, CT Rhodes. Preparation and characterization of liposomes as therapeutic delivery systems a review. Pharm Acta Helv 70(2) 95—111, 1995. 

Using liposomes made from phospholipids as models of membrane barriers, Chakrabarti and Deamer [417] characterized the permeabilities of several amino acids and simple ions. Phosphate, sodium and potassium ions displayed effective permeabilities 0.1-1.0 x 10 12 cm/s. Hydrophilic amino acids permeated membranes with coefficients 5.1-5.7 x 10 12 cm/s. More lipophilic amino acids indicated values of 250 -10 x 10-12 cm/s. The investigators proposed that the extremely low permeability rates observed for the polar molecules must be controlled by bilayer fluctuations and transient defects, rather than normal partitioning behavior and Born energy barriers. More recently, similar magnitude values of permeabilities were measured for a series of enkephalin peptides [418]. 

Jiang W, Lionberger R, Yu LX (2011) In vitro and in vivo characterizations of PEGylated liposomal doxorubicin. Bioanalysis 3 333-344... 

Characterizing the resultant complex for the amount of protein per liposome is somewhat more difficult than in other protein conjugation applications. The protein-liposome composition is highly dependent on the size of each liposomal particle, the amount of protein charged to the reaction, and the mole quantity of reactive lipid present in the bilayer construction. An approach to solving this problem is presented by Hutchinson et al. (1989). In analyzing at least 17 different protein-liposome preparations, the ratio of proteindipid content (pg protein/pg lipid) in most of the complexes ranged from a low of about 4 to as much as 675. In some instances, however, up to 6,000 molecules of a particular protein could be incorporated into each liposome. 

The liposome vesicles may be characterized for size by chromatography on a column of Sepharose 4B. 

Hutchinson, F.J., Francis, S.E., Lyle, I.G., and Jones, M.N. (1989) The characterization of liposomes with covalently attached proteins. Biochim. Biophys. Acta 978,17-24. 

Mayhew, E., Lazo, R., Vail, W.J., King, J., and Green, A.M. (1984) Characterization of liposomes prepared using a microemulsifier. Biochim. Biophys. Acta 775, 169-174. 

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