Capillary Electrophoresis with Laser-induced Fluorescence Detection for Application in Intracellular Investigation of Anthracyclines and Multidrug Resistance Proteins.

Capillary electrophoresis (CE) coupled with laser-induced fluorescence (LIF) is a powerful method for the trace analysis of cellular components. This review presents a summary of topics for the direct analysis of anthracyclines and multidrug resistance proteins in cancerous cells. A micellar electrokinetic chromatography (MEKC) method that does not use organic solvents, and hence prevents the precipitation of proteins in cellular samples, was shown to be a reliable method for the determination of several anthracyclines including the epimeric doxorubicin and epirubicin. A fast CE-based immunoassay for investigating transporter multidrug resistance associated protein (MRP1) was also developed for routine or explorative analysis of the levels of transporter proteins in cancerous cells. A combination of the developed MEKC-LIF method and the CE immunoassay (CEIA) method has permitted the analysis of anthracyclines and MRP1 in a cell line to show the relationship between the levels of MRP1 and amount of anthracyclines in cancerous cells.

Rapid determination of multidrug resistance-associated protein in cancer cells by capillary electrophoresis immunoassay.

The adenosine triphosphate (ATP) binding-cassette (ABC) transporters are a superfamily of cellular proteins that have been partly implicated as a cause of multidrug resistance (MDR) in cancer cells. The ABC superfamily consists of P-glycoprotein, multidrug resistance-associated proteins (MRP) and breast cancer-related proteins, of which MRP is of particular interest because of its ability to efflux a broader range of substrates. Since MRP1 is the most prominent member of the MRP family, a simple technique is needed for its quantification. We developed a simple, fast (total analysis time of 3h) capillary electrophoresis immunoassay (CEIA) for the quantification of MRP1 in cancer cells. MRP1 antibody was labeled with fluorescein isothiocyanate. The labeled antibody was incubated with the cell lysate for a fixed interval (1h), after which the cell lysate mixture was directly injected into the capillary to separate the complex of MRP1 and its antibody from free antibody. The noncompetitive CEIA method had a limit of detection of 0.2 nM and a good linear range (1.7-14.9×10(4) cells), and was fairly reproducible (RSD<10%). The results showed that two cell lines, A549 and RDES, expressed MRP1 in the absence of doxorubicin (DOX), with A549 registering a higher expression. Compared to DOX-free cancer cells, there was an acceleration of MRP1 expression during the 12h-exposure to DOX, after which the level of expression remained nearly constant as the intracellular accumulation of DOX decreased. The results obtained in this work indicate that the developed CEIA method is useful for relative quantification of MRPs in cancer cells.

Micellar electrokinetic chromatographic analysis for in vitro accumulation of anthracyclines enhanced by inhibitors of cell membrane transporter-proteins in cancer cells.

Cell membrane transporter-proteins have been partly implicated in lowering the accumulation of drugs in cancer cells, leading to multidrug resistance (MDR). Two cancer cell lines, A549 and RDES, were continuously exposed to subclinical concentration (250 nM) of anthracyclines and micellar electrokinetic chromatography was used to investigate their in vitro accumulation after treatment with inhibitors of membrane transporter-proteins. The four anthracylines [doxorubicin (DOX), epirubicin (EPI), daunorubicin (DNR), and idarubicin (IDA)] were separated within a short analysis time of less than 15 min in borate buffer (80 mM, pH 9.22) containing sodium taurodeoxycholate (35 mM), 2-hydroxypropyl-γ-cyclodextrin (3.5% wt/v), and sodium dodecylsulfate (20 mM). Laser-induced fluorescence was used for detection of the anthracyclines. Three inhibitors, verapamil, cyclosporine A and probenecid, were examined by adding each inhibitor independently or two inhibitors simultaneously to the culture medium. It was found that independent use of each inhibitor leads to more efficient accumulation than combined use of verapamil and probenecid. In addition, the results show that effect of inhibitors on the accumulation of anthracyclines depended on type of cell: in RDES, inhibitors enhanced accumulation of all four anthracyclines, while in A549, inhibitors showed different accumulation behavior for each anthracycline. Generally higher accumulation of anthracyclines was observed in RDES cells than A549, as evidenced by dead cells (7-16%) after 24 h of continuous exposure to subclinical concentration.

Measurement of intracellular accumulation of anthracyclines in cancerous cells by direct injection of cell lysate in MEKC/LIF detection.

Anthracyclines are chemotherapeutic drugs that are broadly used in the treatment of various types of solid cancers and leukemia. Herein, we report on a novel analytical method for intracellular accumulation of anthracyclines using MEKC/LIF detection. An aqueous separation system permitted the injection of cell lysates directly into the capillary. The MEKC migrating solution was made up of borate buffer at pH 9.22 containing sodium taurodeoxycholate, (2-hydroxypropyl)-gamma-CD, and SDS. The anthracyclines, Doxorubicin (DOX) and epirubicin (EPI) were detected by LIF using a Nd:YAG laser (532 nm) or an argon ion laser (488 nm) for excitation. Two cell lines, human humerus tumor cells (RDES) and human lung tumor cells (A549), were treated with a mixture of the two anthracyclines for fixed periods of time, and then intracellular concentrations were determined by injecting cell lysates directly. Recovery values of 96.0-100.8% were obtained for DOX and EPI. Reproducibility quantified by RSD was less than 3.9% intraday and 6.7% interday at concentrations ranging between 50 and 500 nM. The uptake of EPI was found to be slightly less than that of DOX for A549, but higher levels of EPI were observed in RDES. Intracellular accumulation of anthracyclines was greater in RDES than in A549, but both types of cells excreted anthracyclines after 12 h. These results indicate that MEKC with an aqueous medium is useful for investigating intracellular uptake and accumulation of drugs, since cell lysates can be used directly with no pretreatment such as deproteination or solvent extraction of analytes.

Determination of bromate ion in drinking water by capillary zone electrophoresis with direct photometric detection.

Bromate ion in drinking water was determined by capillary zone electrophoresis (CZE) with direct photometric detection. Bromate ion in the sample solution was introduced and concentrated into the capillary by electrokinetic injection for 50s at -10 kV. Electrophoretic separation was made at an applied voltage of -25 kV and bromate ion was detected at wavelength 193 nm, at which the baseline was stabilized with less UV-absorbing acidic phosphate buffer. Bromate ion was detected within 5 min in the electropherogram. By increasing the electric conductivity in the migrating solution with 10 mM Na2SO4, a limit of detection (LOD) of 9 x 10(-10)M (0.1 microg/L BrO3-) was achieved. The proposed method was applied to the analysis of tap water and river water samples, but bromate ion was not detected. Because the practical samples contain relatively large amount of foreign ionic substances, the tap water sample was diluted to avoid the matrix ions. Bromate ion added in a tap water at the concentration of 8 x 10(-8)M was quantitatively recovered by diluting it 1/10.

Capillary zone electrophoretic studies of ion association between inorganic anions and tetraalkylammonium ions in aqueous-dioxane media.

Ion association between inorganic anions and symmetrical tetraalkylammonium ions, R4N+ (R = Me, Et, Pr, n-Bu, n-Am, and 2-methyl butyl {isoamyl = iAm}) was investigated using ordinary silica capillary by capillary zone electrophoresis. An improved version of the Williams-Vigh method was used for the first time to measure the mobilities of the inorganic anions. Plots of log Kass against log dielectric constant in various media, revealed a smaller change in Kass compared to dielectric constant. These plots suggest that the Bjerrum's equation is inadequate in accounting for the associations of ions in a CZE setup.

Evaluation of weak ion association between tetraalkylammonium ions and inorganic anions in aqueous solutions by capillary zone electrophoresis.

The evaluation of weak ion association between eleven (11) inorganic anions (charge -1 to -3) and five n-tetraalkylammonium ions, R4N+ (R: methyl, Me; ethyl, Et; propyl, Pr; butyl, Bu; pentyl, Am) in aqueous media at 25 degrees C was studied. The analysis of ion association equilibria was carried out under acidic condition (formate buffer, pH 3.5) at low separating potential (-10 kV) using a coated capillary with suppressed electroosmotic flow (micro = 4 x 10(-5) cm2 V(-1) s(-1)). Direct UV detection was done at anode (lambda = 220 nm). The combination of the aforementioned conditions ensured that ion association constants, Kass, between n-tetraalkylammonium ion and the small inorganic anions were reliably determined after a non-linear least squares (NLLS) treatment of the measured anion's mobility. Like their larger counterparts, small anions showed increased interaction with an increase in size of pairing ions. Moreover, for a specific cation, the interaction of small anions increased with an increase in size of the hydrated anions as reflected by the relationship between the Kass and the Stokes' radius. A favourable comparison exists between the results presented in this work and those previously documented from other analytical techniques like conductometry. Qualitatively, the mobility of the anions appeared to obey the Hückel's model more closely than the more elaborate Zwanzig and Hubbard-Onsager models.