Investigation of vesicle electrokinetic chromatography as an in vitro assay for the estimation of intestinal permeability of pharmaceutical drug candidates

Abstract

As the pharmaceutical industry continues the daunting search for novel drug candidates, there remains a need for rapid screening methods not only for biological activity, but for physiochemical properties as well. It is invaluable that adequate model systems for absorption and/or bioavailability be developed early in the drug evaluation process to avoid the loss of promising compounds late in development. The focus of this paper is the use of vesicle EKC (VEKC) as a high-throughput, easy, cost-effective, and predictive model for the passive transcellular diffusion of drug candidates in the intestinal epithelium. Vesicles are large aggregates of molecules containing a spherical bilayer structure encapsulating an internal cavity of solvent. It is this bilayer structure that makes vesicles attractive as model membranes. In this study, vesicles were synthesized from both phospholipids and surfactant aggregates, and then employed as pseudostationary phases in EKC (VEKC). The interaction of drug molecules with vesicles in EKC was then used as the basis for an in vitro assay to evaluate passive diffusion. The VEKC technique showed a statistical correlation between the retention of drug candidates using surfactant and phospholipid vesicles and passive diffusion data (log Pow and colon adenocarcinoma). VEKC analysis offers high-throughput capabilities due to the short run times, low sample, and solvent volumes necessary, as well as instrument automation. However, due to the complexity of drug absorption in the intestine, difficulty arises when a single in vitro model is used to predict in vivo absorption characteristics. Therefore, the retention of drug candidates using VEKC in conjunction with other permeability prediction methods can provide a primary screen for a large number of drug candidates early in the drug discovery process with minimal resources.

Compositional effects on electrophoretic and chromatographic figures of merit in electrokinetic chromatography with cetyltrimethylammonium bromide/sodium octyl sulfate vesicles as the pseudostationary phase. Part 1: Effect of the phase ratio

“…Figures of merit of that have been evaluated include the magnitude of EOF and the electrophoretic mobility of the vesicle, efficiency (plate count), retention, selectivity (methylene, shape, enantioselectivity, and/or chemical (LSER), and the elution range (migration window). Besides unilamellar surfactant vesicles comprised of CTAB/SOS [56,60,72,73], we have examined vesicles consisting of DTAB/ SDS [45], dodecoxycarbonylvaline (DDCV)/SDS [71], octyltrimethylammonium bromide (OTAB)/SDS [74], and cetyltrimethylammonium chloride (CTAC)/SOS [73].…”

“…Our research in vesicle EKC (VEKC) has focused, for the most part, on the fundamental electrokinetic and chromatographic properties of catanionic unilamellar vesicles [45,56,60,[71][72][73][74] that in our experience are more easily prepared and more stable than similar aqueous buffered solutions of liposomes [56]. Figures of merit of that have been evaluated include the magnitude of EOF and the electrophoretic mobility of the vesicle, efficiency (plate count), retention, selectivity (methylene, shape, enantioselectivity, and/or chemical (LSER), and the elution range (migration window).…”

“…The bilayer structure of vesicles resembles that of cell membranes, and although many components of the latter such as peripheral and integral membrane proteins, ionchannels, etc., are typically not included by design in vesicle PSPs for a variety of reasons (increased cost, complexity, lack of commercial availability), both surfactant-and phospholipid-based vesicles have nevertheless proven to be useful for modeling a number of biological and nonbiological processes [50][51][52][53] including the prediction/estimation of drug absorption [54], blood-brain barrier penetration [55], intestinal permeability [56], drug interactions with lipid bilayers [53,57,58], protein-liposome interactions [59], octanolwater partitioning [45,60,61], etc.…”

Drug–liposome distribution phenomena studied by capillary electrophoresis‐frontal analysis

“…Also, CE has been used to assess liposomal drug delivery systems in a few cases [18][19][20][21][22]. Liposomes have, however, primarily been introduced into capillaries in studies directed at estimating drug lipophilicity in relation to membrane permeability properties [2][3][4][5][23][24][25][26][27][28]. These studies have been conducted using the liposomes as a pseudostationary phase, i.e., by EKC [2-5, 23-26, 28] or by CEC [27].…”

“…This is due to the structural resemblance of liposomes and cell membranes and their use as drug delivery vehicles. Like biological membranes liposomes consist of a lipid double layer, liposomes may therefore be used as models for the study of drugmembrane adsorption, distribution, and permeation [1][2][3][4][5]. Liposomal drug delivery technology has over the years advanced and marketed drug products using liposomes as the delivery vehicle are available [6][7][8].…”