Research Article Fast investigations from biological matrices using CE – Test of a blood–brain barrier model In order to adopt a general workflow for complex biological matrices with respect to a new blood–brain barrier (BBB) model, a micellar electrokinetic chromatography method has been developed. The cells forming the BBB have been cultivated in a special cell growth medium in which six drugs (acetaminophen, caffeine, carbamazepine, cimeti- dine, indometacin and propranolol) have been dissolved and tested for their penetration properties. The results showed good to very good accordance to the reference values. Samples were directly injected onto the capillary without any pretreatment (fused silica capillary, id: 50 mm, L: 48 cm, l: 40 cm). After method development, separations were carried out using a 60 mM borate buffer containing 200 mM of SDS at 30 kV, leading to an analysis time of less than 10 min. Between two runs the capillary was rinsed with a mixture of equal parts of running buffer and isopropanol (70% v/v), which proved to be very effective to remove matrix compounds. An appropriate choice of the detection wavelength (220 or 254 nm) could avoid major interferences between analytes and matrix. The typical RSD% for migration times was approximately 2%, for peak areas, it ranged from 2 to 6%, which was very well acceptable for the generic method used in this study and the low concentrations investigated. The LODs ranged from 10 to 30 ng/mL. Keywords: Blood–brain barrier / Direct injection / MEKC DOI 10.1002/elps.201100282 1 Introduction The blood–brain barrier separates blood and cerebrospinal fluid in the central nervous system (CNS). Endothelial cells in CNS form tight junctions restricting the passage of solutes [1] and shield the brain from most pathogens and toxic substances. Models of the blood–brain barrier (BBB) are of high importance for permeability tests in the course of drug development, especially for those drugs that are intended to act in the CNS [2]. Promising drug candidates can be explored and, in a second step, preclinical trials can be prepared using the cell models [3, 4]. Vice versa, permeability tests of well-described compounds allow the analyses of BBB characteristics [5, 6]. Other important applications of BBB models are investigations on the pathways of microorganisms, which cause severe diseases of the CNS after invasion, namely, bacterial meningitis [7], neurosyphilis [8] and Human African Trypanosomiasis (sleeping sickness) [9]. A reliable BBB model has been developed in order to gain further information on the pathogen of the latter, Trypanosoma brucei, and its means of invasion into the CNS (C. Untucht and M. Steinert, manu- script in preparation). Such a model for investigations on infections should provide realistic drug permeations proper- ties as well. Tests of promising anti-infectious drugs can then be performed on the same in vitro model. BBB model systems vary from completely isolated brain capillaries [10] and three-dimensional model systems [11, 12] to transwell- based models with one or more cell types (astrocytes, pericytes and endothelial cells) [13, 14]. The aim of this study was to develop an analytical method for the quantitation of drugs in cell culture media. This method was intended to be applied for the character- isation of the BBB model (C. Untucht and M. Steinert, manuscript in preparation) regarding its drug penetration properties for a set of six pharmaceutical compounds with known permeation properties, namely, acetaminophen, caffeine, carbamazepine, cimetidine, indometacin and propranolol. For analysis, a micellar electrokinetic chroma- tography (MEKC) method has been favoured. MEKC offers high-resolution separation of a wide range of chemical and biological compounds. The separation Sascha Ku ¨ hne 1 Christopher Untucht 2 Michael Steinert 2 Hermann Wa ¨ tzig 1 1 Technische Universita ¨t Braunschweig, Institut fu ¨r Pharmazeutische Chemie, Braunschweig, Germany 2 Technische Universita ¨t Braunschweig, Institut fu ¨r Mikrobiologie, Braunschweig, Germany Received February 10, 2011 Revised July 14, 2011 Accepted July 25, 2011 Abbreviation: BBB, blood–brain barrier Correspondence: Professor Hermann Wa ¨ tzig, Technische Universita ¨ t Braunschweig, Institut fu ¨ r Pharmazeutische Chemie, BeethovenstraXe 55, 38106 Braunschweig, Germany E-mail: h.waetzig@tu-braunschweig.de Fax: 149-531-391-2799 & 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.electrophoresis-journal.com Electrophoresis 2012, 33, 395–401 395