Pharmacokinetic investigations with direct injection of plasma samples: possible savings using capillary electrophoresis (CE)

Application of multiplex methylated-specific PCR with capillary electrophoresis to explore prognostic value of TSGs hypermethylation for hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is a malignant tumor that severely threatens human health. To date, early detection for HCC patients is particularly significant due to their poor survival rates even after liver resection.

METHODS

Therefore, an efficient and sensitive detection method for monitoring liver cancer, multiplex methylation-specific PCR (MSP) coupled with capillary electrophoresis, is developed.

RESULTS

Simulations demonstrated that the methylation status of RASSF1A, p16, SFRP1, and ELF could be detected even when DNA equaled or exceeded 12.5 ng simultaneously. Also, its accuracy for methylation detection outweighed polyacrylamide gel electrophoresis (87.5%) and agarose electrophoresis (84.3%), reaching 92.1%. Subsequently, we implemented multiplex MSP with capillary electrophoresis to investigate methylation status of the four tumor suppressor genes in tissue specimens and explore the prognostic value for HCC patients. As the data suggested, multivariate cox regression analysis revealed that the recurrence-free survival of 46 patients was greatly associated with portal vein tumor thrombus (PVTT) and p16 methylation and receiver operating characteristic (ROC) curves demonstrated that the predictive range of portal vein tumor thrombus (PVTT) combined with p16 hypermethylation was more sensitive than that of either PVTT or p16 hypermethylation alone with regard to disease recurrence in patients with HCC, which could be testified as a valuable biomarker in Clinical application.

CONCLUSION

Multiplex MSP coupled with capillary electrophoresis has an excellent prospect of clinical application for monitoring early liver cancer and screening valuable biomarkers for prognosis of HCC patients.

Synthesis and application of FePt/CNTs nanocomposite as a sensor and novel amide ligand as a mediator for simultaneous determination of glutathione, nicotinamide adenine dinucleotide and tryptophan

In this study, we report the synthesis and application of a FePt/CNTs nanocomposite as a highly sensitive sensor and novel amide ligand (9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboximido)-4-ethylbenzene-1,2-diol as a mediator for the determination of glutathione (GSH), nicotinamide adenine dinucleotide (NADH) and tryptophan (Trp). The synthesized materials were characterized with different methods such as NMR, IR spectroscopy, TEM, XRD, FESEM, cyclic voltammetry, electrochemical impedance spectroscopy and square wave voltammetry (SWV). The modified electrode exhibited a potent and persistent electron mediating behavior followed by well-separated oxidation peaks of GSH, NADH and Trp. The peak currents were linearly dependent on GSH, NADH and Trp concentrations in the range of 0.08-220, 1.0-400 and 5.0-500 μmol L(-1), with detection limits of 0.05, 0.8 and 1.0 μmol L(-1), respectively. The modified electrode was used for the determination of these compounds in real samples.

SPE and large-volume sample stacking in MEKC for determination of doxycycline in biological fluids: comparison of direct injection to SPE-MEKC

A novel and simple method has been developed for the determination of doxycycline (DOX) in biological fluids. The method is based on SPE, large-volume sample stacking (LVSS) and MEKC with UV-DAD detection. Six SPE cartridges have been used in investigation for sample clean up and pre-concentration (Supelco LC-8, LC-18, LC-SCX, and LC-WCX, as well as Strata-X and X-C). DOX was determined on a 56 cm (effective length 50 cm) x 50 microm id fused-silica capillary. The BGE was 20 mM borate buffer, pH 9.3, containing 80 mM SDS and 7.5% v/v of methanol (30 sx50 mbar), and the temperature and voltage were 25 degrees C and 30 kV, respectively. The analytical wavelength was set at 210 nm. Under optimized conditions it is possible to determine DOX in human serum, urine, semen, tears and saliva with recovery of 97.5% (RSD 2.5%). The method was shown to be sensitive (LOD is 1 microg/L) and precise (intra-day RSD 0.2 and 2.4%; inter-days 0.4 and 3.5% for migration time and peak area, respectively). Results for developed SPE-LVSS-MEKC were compared with LVSS-MEKC method with direct sample injection. The new LVSS-MEKC method is presented as a useful technique for rapid determination without extraction procedure of DOX in human urine and serum, using 80 mM of SDS, 10% v/v of methanol and 40 mM borate buffer (pH 9.3; 30 s x 50 mbar; 25 degrees C; 30 kV; 350 nm), but not for the other biological fluids, according to lower sensitivity of the method and because of the sample composition.

Simultaneous determination of dipyridamole and salicylic acid in human plasma by high performance liquid chromatography-mass spectrometry

A sensitive, rapid and simple high-performance liquid chromatography-electrospray ionization-mass spectrometry (HPLC-ESI-MS) method for simultaneous determination of dipyridamole and salicylic acid in human plasma has been developed and validated. After the addition of diazepam and rosiglitazone as internal standard (IS), plasma samples were prepared by liquid-liquid extraction followed by an isocratic elution with methanol:2 mM ammonium acetate buffer (pH 4.25; 70/30, v/v) on a Shimadzu VP-ODS C(18) column (5 microm, 150 x 2.0 mm I.D.). Detection was performed on a quadrupole mass spectrometer with ESI interface operating in the positive-ion mode for dipyridamole and negative-ion mode for salicylic acid. Calibration curves were linear (r(2) > 0.99) over the concentration range 10-2500 ng/mL for dipyridamole and 30-4000 ng/mL for salicylic acid with acceptable accuracy and precision, respectively. The intra- and inter-batch precisions were less than 15% of the relative standard deviation. The limits of detection of dipyridamole and salicylic acid were 1 and 15 ng/mL, respectively. The validated HPLC-ESI-MS method was successfully applied to a preliminary pharmacokinetic study of fixed-dose combination of sustained-release dipyridamole/aspirin in Chinese healthy male volunteers.

Investigation on response of the metabolites in tricarboxylic acid cycle of Escherichi coli and Pseudomonas aeruginosa to antibiotic perturbation by capillary electrophoresis

Metabolomics is a new branch of systems biology exerting its influence in many aspects. In order to appraise the effects of antibiotics on central carbon metabolism, a CE based method was set up. With this platform, we estimated the organic acid metabolite pools' fluctuation of Escherichia coli and Pseudomonas aeruginosa cultured under 11 different antibiotics' stimuli. Multivariate data analysis showed that different antibiotics had clustered distributions for each strain and could be easily distinguished. Genetic, metabolic and antibiotic mechanism differences could also be deduced by the aid of further correlation analysis. For P. aeruginosa, even synergy action amid antibiotics could be ascertained.

Protein adsorption in fused-silica and polyacrylamide-coated capillaries

The model proteins cytochrome c, myoglobin, ovalbumin, and beta-lactoglobulin were investigated with regard to their adsorption properties on capillaries for electrophoresis. The model compounds were selected to cover a wide range of properties. Cytochrome c is a basic protein (isoelectric point (pI): 9.6; M(r): 11.7 kDa), beta-lactoglobulin is rather acidic (pI: 5.4, M(r): 18.4 kDa), myoglobin was chosen as a neutral reference protein (pI: 6.8-7.4, M(r): 17.8 kDa), and ovalbumin (pI: 5.1, M(r): 45.0 kDa) was selected as a relatively larger analyte. First, the pH dependence of adsorption was investigated for the bare fused silica. A clear correlation to the respective pIs was noted. For myoglobin and ovalbumin, none or negligible adsorption was found above the pI, whereas strong adsorption was noted just below this parameter. Cytochrome c and beta-lactoglobulin already showed distinct adsorption above their pIs. However, none of the proteins showed any significant adsorption more than one pH unit above the pIs. For linear polyacrylamide-coated capillaries, a decreased but not a complete lack of adsorption was observed. Here, pH-dependent adsorption was noted as well. Regeneration of the capillaries by rinsing with buffers containing 200 mM SDS was also investigated. This method was completely successful for myoglobin, but that too for only freshly-adsorbed protein. After a storage time of 24 h and due to the aging of the adsorbate, a sufficient regeneration was no longer possible.

Capillary electrophoresis-a high performance analytical separation technique

Capillary electrophoresis (CE) is often one of the preferred techniques in pharmaceutical quality control and in clinical chemistry, particularly considering the high selectivity and lower costs compared to HPLC. The precision of CE is as good as in liquid chromatography (LC). The sample-throughput is high due to short analysis times. Efforts for sample pre-treatment are usually minor in CE. Urine and even blood plasma can be directly injected without further pre-treatment. After summarising the basic principles of CE, general strategies for method development are described to achieve selective, efficient, precise, fast, sensitive, and validated methods. Sample pre-treatment requirements are discussed. Standard buffer recipes, surfactants used in micellar electrokinetic chromatography (MEKC), chiral selectors, useful buffer additives, actions to deal with complex matrices, and aspects of validation have been collected. Other techniques that can be performed with CE instruments, such as capillary isoelectric focusing (CIEF), capillary isotachophoresis (CITP), and capillary electrochromatography (CEC), are briefly discussed.

Simultaneous determination of dexamethasone and trimethoprim by liquid chromatography

A reverse phase high performance liquid chromatography (HPLC) method to determine dexamethasone phosphate and trimethoprim is described in this paper. The separation was made in a LichrCART(R) C18 column using an acetonitrile-NaH(2)PO(4) (10 mM) (70:30, v/v) (pH 3) buffer solution as mobile phase. The mobile-phase flow rate and the sample volume injected were 1 ml/min and 20 microliter, respectively. The limits of quantification were about 0.25 mg/l for each compound. The method was applied in synthetic mixtures and in pharmaceutical formulations. Analyses were made by preparing test (from the stock solution) method whose results were compared with those obtained by means of the standard addition method. Both methods showed similar results, and then it was proved that some pharmaceuticals claimed levels were in agreement with the obtained results by using our analytical method.

Analysis of antibiotics by capillary electrophoresis

This article reviews recent developments in the characterization of antibiotics. Many capillary electrophoretic techniques have been utilized in their analyses, addressing various aspects of quantifying, profiling and monitoring. Sensitive electrochemical and laser-induced fluorescence detection systems have been utilized, demonstrating trace level determinations in clinical settings and in environmental samples. Different sample introduction methods have been explored, enhancing detection sensitivity, or reducing or eliminating sample manipulation prior to injection.

Determination of salicylate, gentisic acid and salicyluric acid in human urine by capillary electrophoresis with laser-induced fluorescence detection

Acetylsalicylic acid (Aspirin) is rapidly metabolized to salicylic acid (salicylate) and other compounds, including gentisic acid and salicyluric acid. Monitoring of salicylate and its metabolites is of toxicological, pharmacological and biomedical interest. Three capillary electrophoresis (CE) methods featuring alkaline aqueous buffers, laser-induced fluorescence (LIF) detection and no solute extraction or derivatization have been explored. A competitive binding, electrokinetic capillary-based immunoassay is developed that recognizes the presence of salicylate and gentisic acid in urine. Differentiation of the two compounds, however, is problematic. With appropriate ultraviolet excitation, many salicylate-related compounds are fluorescent so that CE with direct urine injection and LIF detection permits the determination of salicylate, gentisic acid and salicyluric acid. Using a HeCd laser with 325 nm produces interference-free monitoring of all three compounds. Using 257 nm excitation from a frequency doubled Ar ion laser, native fluorescence of an endogenous urinary compound that co-migrates with gentisic acid is observed. With wavelength-resolved fluorescence detection, however, the two substances are distinguished. Furthermore, this technique, with comparison to literature data, permits the putative assignment of several peaks to other salicylate metabolites, namely glucuronide conjugates of salicylate and salicyluric acid. All three CE-LIF techniques have been applied to toxicological patient urines and urines collected after ingestion of 500 mg acetylsalicylic acid. CE results compare favorably with those obtained by a commercial fluorescence polarization immunoassay and by a conventional photometric assay.

Comparison of Capillary Electrophoresis with HPLC for Diagnosis of Factitious Hypoglycemia

Background: The diagnosis of “factitious hypoglycemia” is essentially based on the disclosure of hypoglycemic agents in blood or urine. The aim of this study was to evaluate the performance of capillary electrophoresis (CE) as a quantitative method for determination of chlorpropamide, tolbutamide, glipizide, gliclazide, and glibenclamide in serum.

Methods: Serum samples (1 mL), with internal standard added, were purified by solid-phase extraction on OASISTM HLB cartridges (Waters), dried under reduced pressure, and reconstituted with 30–60 μL of acetonitrile:H2O. Analysis was carried out by micellar electrokinetic capillary chromatography in 5 mmol/L borate, 5 mmol/L phosphate, 75 mmol/L sodium cholate, pH 8.5, containing 25 mL/L methanol. Separation was accomplished in a 20 cm × 50 μm (i.d.) silica capillary at 25 °C and a constant voltage of +10 kV. Pharmacokinetics of gliclazide (80-mg tablet) in a diabetic patient were assayed by both HPLC and CE. Two hypoglycemic patients positive by HPLC analysis for unreported gliclazide and tolbutamide overdose were also screened by CE.

Results: Separation of six drugs (including the internal standard) was accomplished in 5 min plus 5 min rinsing. The between-day CV of the ratio of the areas of the sulfonylurea drugs to internal standard was <1% (n = 10). Linearity (r2 ≥0.998) and recovery (≥80%) were good for all sulfonylurea drugs tested. Pharmacokinetic curves for gliclazide by CE and HPLC were superimposable. CE analysis confirmed the HPLC diagnosis of surreptitious abuse of gliclazide and tolbutamide.

Conclusion: CE is a useful tool in the clinical chemistry and toxicology laboratory for drug monitoring and pharmacokinetic investigations.