Size-Dependent Electrophoretic Migration and Separation of Liposomes by Capillary Zone Electrophoresis in Electrolyte Solutions of Various Ionic Strengths

Abstract

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 kappaR, where kappa(-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 kappaR 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.

Evaluation of individual particle capillary electrophoresis experiments via quantile analysis

“…Although flow cytometry was historically used first to detect individual organelles [9,10], CE has the additional analytical advantage of being able to separate organelles based on their electrophoretic mobilities [11][12][13][14]. In general, the electrophoretic mobility of a particle stems from its size [12,14,19] and surface characteristics [13,19], which makes CE useful for comparing the size or surface characteristics of individually detected biological species, such as proteins [15], mitochondria [8,16], nuclei [17], and acidic organelles [18]. The size and surface characteristics of these particles may be highly heterogeneous, making it extremely important to analyze samples with a sufficient number of individual species so that an accurate statistical description is observed.…”

Electrophoretic mobility and molecular distribution studies of poly(amidoamine) dendrimers of defined charges

“…Among the techniques used for the separation of colloids and biologic macromolecules, CE has been established as a reliable and widely useful analytical technique with high resolution, high efficiency, and high automation capability [4,5]. A broad range of colloids including polystyrene lattices [6][7][8], silica sols [9], semiconductor clusters [10], virus and bacterial particles [11,12], and liposomes [13,14] have been separated by CE. The size distribution of various colloid particles, their surface charge density, and relaxation effect under electric field can be effectively evaluated using CE.…”

Capillary electrophoresis of liposomes functionalized for protein binding

“…For this reason, they can be analyzed by CE, and they proved useful as anionic pseudostationary phases in EKC ( ; for recent reviews see [23,24]. It was found that, besides the pH, the kind of the electrolytes [6,25] and its ionic strength [5,18], and the preparation procedure of the vesicles influences the electrophoretic properties of the particles [23,26]. If their electrophoretic mobility is affected upon attachment of ligands, this change can be used to assess, or even quantify, the interaction in a form of ACE.…”

“…The number of lipid molecules in the bilayer (with a mass of 5610 216 g per vesicle, see above) is about 3610 5 (taking 1000 Da as an approximate molecular weight of the lipid). Taking into account that the DOGS-NTA contributes 5% to the total lipid in the bilayer, it can be estimated that each vesicle contains roughly 15 000 DOGS-NTA molecules and consequently the same number of Niions.…”