Polydispersity of liposome preparations as a likely source of peak width in capillary zone electrophoresis (original) (raw)
Related papers
Analytical Chemistry, 2000
The size-dependent electrophoretic migration and separation of liposomes was demonstrated and studied in capillary zone electrophoresis (CZE). The liposomes were extruded and nonextruded preparations consisting of phosphatidylcholine/phosphatidylglycerol/cholesterol in various ratios and ranging from 125 to 488 nm in mean diameter. When liposomes of identical surface charge density were subjected to CZE in Tris-HCl (pH 8) buffers of various ionic strengths (0.001-0.027), they migrated in order of their size. Size-dependent electrophoretic migration and separation of liposomes in CZE can be enhanced or brought about by decreasing the ionic strength of the buffer. It was shown that size-dependent migration is primarily a function of KR, where K -1 is the thickness of the electric double layer (which can be derived from the ionic strength, I, of the buffer) and R, the liposome radius. Liposome mobility depends on KR and surface charge density in a manner consistent with that expected from the Overbeek-Booth electrokinetic theory. Thus, the relaxation effect appears to be the physical mechanism underlying the size-dependent electrophoretic separation of liposomes.
Journal of Separation Science, 2002
Cholesterol-containing phosphatidylcholine liposomes: Characterization and use as dispersed phase in electrokinetic capillary chromatography Unilamellar liposomes were investigated by capillary electrophoresis, light scattering, and monolayer penetration techniques. Zwitterionic liposomes with and without cholesterol were compared and the effects of pH (7.40 and 8.25) and buffer (various sulfonic acid buffers, Tricine, and phosphate) on the electrophoretic mobilities and sizes of the liposomes were studied. Anionic liposomes containing phosphatidylserine with and without various amounts of cholesterol were used as dispersed phase in electrokinetic capillary chromatography in the separation of six steroidal hormones, with a focus on selectivity differences with increasing amounts of cholesterol in the liposomes. The results were confirmed by monolayer penetration measurements.
Liposomes in capillary electromigration techniques
ELECTROPHORESIS, 2009
The use of phospholipid vesicles (liposomes) in EKC and CEC, as well as the use of CE for studying liposomes and lipid-analyte aggregates, are briefly reviewed. The works are presented in the order of appearance. The review describes the most common liposome dispersions used for achieving separation of neutral and charged compounds in liposome EKC. The CEC part is divided into two parts, discriminating between liposomes immobilized on capillaries for hindering analytes from interacting with the fused-silica wall and liposomes immobilized on capillaries for achieving chromatographic phases for separation of compounds. Finally, the use of CE for studying liposomes and lipid-analyte aggregates as analytes is discussed in brief.
Liposomes as carriers in electrokinetic capillary chromatography
Electrophoresis, 2000
Liposomes are small membrane-enclosed vesicles composed of either natural or synthetic lipids. Their size can be adjusted on a wide scale and they can be made with well-defined compositions. While liposomes have been extensively used as model biomembranes they have also gained a considerable degree of attention as carriers for drugs as well as for genetic material. The physical properties of liposomes are critically dependent on their chemical composition. In this study liposomes were applied as pseudostationary phases in electrokinetic capillary chromatography. Various negatively charged liposomes, consisting of mixtures of zwitterionic and anionic lipids, were investigated. Major emphasis was put on clarifying the effects of the total lipid concentration, the lipid molar ratio, the lipid head group, and the buffer on the capillary electrophoretic separation of neutral analytes. In addition, the influence of the physical state of the membrane, i.e., gel vs. fluid, on the separation was investigated. Corticosteroids were applied as model analytes.
Biophysical Journal, 1992
The electrophoretic mobility of liposomes containing a negatively charged derivative of phosphatidylethanolamine with a large headgroup composed of the hydrophilic polymer polyethylene glycol (PEG-PE) was determined by Doppler electrophoretic light scattering. The results show that this method is improved by the use of measurements at multiple angles to eliminate artifacts and that very small mobilities can be measured. The electrophoretic mobility of liposomes with 5 to 10 mol % PEG-PE is -0.5 ,ums-1/Vcm-' regardless of PEG-PE content compared with --2 ,ms1'/Vcm-' for similar liposomes but containing 7.5% phosphatidylglycerol (PG) instead of PEG-PE. Measurements of surface potential by distribution of an anionic fluorescent probe show that the PEG-PE imparts a negative charge identical to that by PG, consistent with the expectation of similar locations of the ionized phosphate responsible for the charge. The reduced mobility imparted by the surface bound PEG is attributed to a mechanism similar to that described for colloidal steric stabilization: hydrodynamic drag moves the hydrodynamic plane of shear, or the hydrodynamic radius, away from the charge-bearing plane, that of the phosphate moities. An extended length of 50 A for the 2,000 molecular weight PEG is estimated from the reduction in electrophoretic mobility.
Liposome Capillary Electrophoresis of Peptides and Proteins
Chromatographia, 2004
Liposome capillary electrophoresis (LCE) using unilamellar liposomes composed of the zwitterionic phospholipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) as a suspended pseudo stationary phase has been investigated for its capability at separating peptides and proteins in bare fused-silica capillaries. The study has explored different strategies for allowing the liposome suspension to act as a disperse pseudo stationary phase with the ability of modulating selectivity, resolution and separation performance of peptides and proteins in bare-fused silica capillaries. Such strategies comprise the use of capillaries either partially or totally filled with the liposome suspension, whereas the electrolyte solution is liposome-free, or the incorporation of the liposomes into the buffer solution employed for rinsing the capillary and as the background electrolyte. Three synthetic peptides of similar amino acid sequence and four basic standard proteins have been employed as test analytes. Varying the volume of the liposome suspension introduced in the capillary promoted differentiated variations in the migration velocity of the three peptides reflecting their selective interactions with the liposomes. Efficient separation of basic proteins was obtained at pH 7.4 in a bare fused-silica capillary with the electrolyte solution containing 60 lM POPC.
Size separation and size determination of liposomes
Journal of Separation Science, 2011
We developed a method for separating liposomes by size and determining their average diameters. Liposomes with different average diameters were separated on a monolithic silica capillary column, and the size of the liposomes corresponding to each peak was determined online with a dynamic light scattering detector coupled to the capillary liquid chromatography system. The calculated diameters for the separated liposomes were similar to the diameter values measured in batch mode. We demonstrate that this combination of a monolithic capillary column and light scattering detection could be used for size separation of liposomes and could provide more details about average diameters than batch-mode analysis.
Analytical Chemistry, 2012
This supporting information section includes the description of the analytical equations used for the determination of electrophoretic mobility and particle size using normal electrical field-flow fractionation (ElFFF) and cyclical electrical field-flow fractionation (CyElFFF). This section also includes additional data related to reduced band broadening at higher applied voltage and electrophoretic mobility distribution plot for 5 VPP. Supporting Note 1. Description of the analytical equations used for the determination of electrophoretic mobility and particle size.
Effect of cholesterol concentration on size of liposome
IOSR Journal of Pharmacy and Biological Sciences, 2012
In this article information about effect of cholesterol concentration on vesicle size of liposome. The advantages and disadvantages of the methods have been described in terms of size distribution and encapsulation efficiency. The reduction of the size of the multilamellar vesicles (MLVs) to small unilamellar vesicles (SUVs) so as to increase their plasma lifetime and consequently increase the possibility of achieving greater tissue localisation.