Volume liposomes

Deamer, D., and Bangham, A. D. (1976). Large volume liposomes by an ether vaporization method, Biochim. Biophys. Acta. 443, 629-634. 

FIGURE 3 Effect of the amount of cholesterol on the particle size. Phosphatidylcholine/cholesterol liposomes were prepared by the octyl glucoside dilution technique. The begin concentration of the mixed micelles was 150 mM octyl glucoside and 10 mM phosphatidylcholine in 10 mM tris(hydroxymethyl)aminomethane and 0.9% NaCl, pH 7.4. Dilution was performed with an automatic titration unit at a dilution rate (= dilution factor, relative to the initial volume, per unit of time) of 0.026 sec"l ( a and ) or 0.69 sec l ( and o). Mean diameters after dilution and ) and after filtration ( L and q) are repi sented. (Adapted from Jiskoot et al, 1986a.)... 

Size exclusion chromatography has been used to analyse the size distribution of liposomes. For example, SUV can be separated from MLV, which elute in the void volume, by using a Sepharose 4B gel. 

An alternative approach to avoid drug leakage from the liposomes on storage is to minimize the volume of the external water phase by... 

In view of the fact that large volumes have been administered to man without causing serious side effects (Zonneveld and Crommelin, 1988), it may be concluded that although liposomes can damage in vitro-cultured human cell lines (Nuzzo et al., 1985 Mayhew et al., 1987b), adverse effects observed in vivo are expected to be minimal. One should realize that liposomes reduce the toxicity of the encapsulated drug. Thus, the toxicity of liposomes may be of minor importance compared to the advantages of administration of certain chemotherapeutics encapsulated in liposomes. 

Here, APsuv is the absorption potential measured from the distribution in small unilamellar vesicles (SUV) at pH 6.8, the solubility was measured at pH 6.8 in simulated intestinal fluid, V is the volume of intestinal fluid, and dose is a mean single oral dose. Liposome partitioning is only partly correlated with octanol/water distribution. 

It is well known that liposomes are good candidates for controlled reactions. As lipid-based colloids, they have been used to mimic biomineralization processes [99,100], while as restricted volumes, they have been used as microreactors to synthesize... 

Wasan, E.K., Fairchild, A., and Bally, M.B., Cationic liposome-plasmid DNA complexes used for gene transfer retain a significant trapped volume, Journal of Pharmaceutical Science, 1998, 87, 9-14. 

Mix the protein solution with the liposome suspension in equal volume amounts. 

Gregoriadis, G. (1984) Liposome technology. Volume III Targeted drug delivery and biological interaction. CRC Press, Boca Raton, Florida. 

Kim, S., and Martin, G.M. (1981) Preparation of cell-size unilamellar liposomes with high captured volume and defined size distribution. Biochim. Biophys. Acta 646, 1-9. 

The encapsulation results in a chance collection of molecules that then form an autocatalytic cycle and a primitive metabolism but intrinsically only an isolated system of chemical reactions. There is no requirement for the reactions to reach equilibrium because they are no longer under standard conditions and the extent of reaction, f, will be composition limited (Section 8.2). Suddenly, a protocell looks promising but the encapsulation process poses lots of questions. How many molecules are required to form an organism How big does the micelle or liposome have to be How are molecules transported from outside to inside Can the system replicate Consider a simple spherical protocell of diameter 100 nm with an enclosed volume of a mere 125 fL. There is room within the cell for something like 5 billion molecules, assuming that they all have a density similar to that of water. This is a surprisingly small number and is a reasonable first guess for the number of molecules within a bacterium. 

Jizomoto and Hirano [3.41 ] tried to increase the amount of drug inclusions in liposomes by inserting Ca2+ ions in dipalmitoylphosphatidylcholine (DPPC) liposomes. The included volume (mL) per g of liposomes is called Vcap, and this can be increased as a function of the Ca2+ concentration up to ten fold of the minimum Vcap The increase in Vcap is attributed to the electrostatic repulsion between the Ca ions, which reduces the number of lamella and increases the diameter of the liposomes to a certain extent, but increases substantially. A calculated simulation of this thesis is in reasonable agreement with the measurements... 

Principal differences between bulk media water and membrane water partition coefficients are listed in Table 2. These differences are essentially based on the several orders of magnitude difference in surface-to-volume ratio. In the liposomal system, charges built up due to sorption of charged species can be electrically neutralised by counter-ions from the electrolyte (diffuse double... 

Most of the results presented in this section, including Eqs. (4.15)—(4.17), are not valid when the equilibrium state of the fluid exhibits global orientational order, for example, a global director. However, they do apply to an isotropic suspension of locally anisotropic objects, such as vesicles or liposomes, which may exhibit a local director, provided that long-range orientational correlations do not extend over a significant fraction of the volume sampled in the experiment. 

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