微流控技术在循环肿瘤细胞异质性分析领域的应用

循环肿瘤细胞(circulating tumor cells,CTCs)的检测是液体活检的重要组成部分,可以通过低损伤甚至无创的方法达到检测体液中肿瘤细胞的目的 .肿瘤细胞在增殖、转移过程中极易产生多种类型的变异,如基因突变、蛋白质组学和表观遗传学改变等,这导致肿瘤细胞个体间发生差异,给临床诊疗带来巨大挑战.通过CTC...     

Direct imaging of single cells and tissue at sub‐cellular spatial resolution using transmission geometry MALDI MS

The need of cellular and sub‐cellular spatial resolution in laser desorption ionization (LDI)/matrix‐assisted LDI (MALDI) imaging mass spectrometry (IMS) necessitates micron and sub‐micron laser spot sizes at biologically relevant sensitivities, introducing significant challenges for MS technology. To this end, we have developed a transmission geometry vacuum ion source that allows the laser beam to irradiate the back side of the sample. This arrangement obviates the mechanical/ion optic complications in the source by completely separating the optical lens and ion optic structures. We have experimentally demonstrated the viability of transmission geometry MALDI MS for imaging biological tissues and cells with sub‐cellular spatial resolution. Furthermore, we demonstrate that in conjunction with new sample preparation protocols, the sensitivity of this instrument is sufficient to obtain molecular images at sub‐micron spatial resolution. Copyright © 2012 John Wiley & Sons, Ltd.     

Improved HPLC method for doxorubicin quantification in rat plasma to study the pharmacokinetics of micelle-encapsulated and liposome-encapsulated doxorubicin formulations

An improved simple, rapid and accurate HPLC method for quantification of doxorubicin derived from micelle-encapsulated or liposome-encapsulated doxorubicin formulation in rat plasma was described. The mobile phase consisting of a mixture of methanol-water [containing 0.1% formic acid anhydrous and 0.1% ammonia solution (25%), pH 3.0], 60:40, was delivered at a flow rate of 1.0 mL/min. Sample preparation for micelle- or liposome-encapsulated doxorubicin in rat plasma were achieved directly by protein precipitation with acetonitrile. Doxorubicin and daunorubicin (internal standard, IS) were separated on a C(18) reversed-phase HPLC column and quantified by a fluoresence detection with an excitation wavelength of 475 nm and an emission wavelength of 580 nm. The linearity was obtained over the range of 5.0-1000.0 ng/mL and 1.0-200.0 microg/mL for doxorubicin and the lower limit of quantitation was 5.0 ng/mL. For each level of quality control samples, inter- and intra-assay precision was less than 9.6 and 5.1% (relative standard deviation), respectively, and percentage error was within +/-2.6%. The extraction recoveries of doxorubicin in the range of 10 ng/mL to 100 microg/mL in rat plasma were between 94.1 and 105.6%. This method was successfully applied to the pharmacokinetic study of doxorubicin formulations after i.v. administration to rats.     

The effect of sample salt additives on capillary electrophoresis analysis of intact proteins using surface modified capillaries

The effect of adding alkali salts to protein samples for capillary electrophoretic (CE) analysis of intact proteins was studied. A high degree of peak stacking, even for large proteins, was found to occur when alkali salts were added to the sample. The addition of salt to the protein sample promotes a strong improvement in the peak efficiency of individual proteins giving up to 2.1 × 10⁶ apparent plates/m. The concentration of salt required in the sample to reach optimal peak efficiency show dependency on both the molecular weight and molar concentration of the protein. However, adding salt will, at a sufficiently high concentration, cause a mixture of proteins to co-migrate to one very sharp peak. The observed sample stacking effect was obtained with a number of different surface modified silica capillaries indicating a general phenomenon and not surface coating specific.     

Separation of single‐base sequential isomers of single‐stranded DNA by capillary electrophoresis and its application in the discrimination of single‐base DNA mutations

Separation of single‐base substitution sequential DNA isomers remains one of the most challenging tasks in DNA separation by capillary electrophoresis. We developed a simple, versatile capillary electrophoresis technique for the separation of single‐base sequential isomers of DNA having the same chain length. This technique is based on charge differences resulting from the different protonation (acid dissociation) properties of the four DNA bases. A mixture of 13 single‐base sequential isomers of 12‐mer single‐stranded DNA was separated by using an electrophoretic buffer solution containing 20 mM phosphoric acid (pH 2.0) and 8 M urea. We demonstrated that our method could separate all possible mutation patterns under identical experimental conditions. In addition, application of our method to the separation of the polymerase chain reaction product of a 68‐mer gene fragment and its single‐base isomers indicates that in combination with the appropriate genomic DNA extraction techniques, the method can detect single‐base gene mutations.     

Quantitative separation of oxytocin,norfloxacin and diclofenac sodium in milk samples using capillary electrophoresis

A simple, sensitive and rapid method has been developed for simultaneous separation and quantification of three different drugs: oxytocin (OT), norfloxacin (NOR) and diclofenac (DIC) sodium in milk samples using capillary electrophoresis (CE) with UV detection at 220 nm. Factors affecting the separation were pH, concentration of buffer and applied voltage. Separation was obtained in less than 9 min with sodium tetraborate buffer of pH 10.0 and applied voltage 30 kV. The separation was carried out from uncoated fused silica capillary with effective length of 50 cm with 75 µm i.d. The carrier electrolyte gave reproducible separation with calibration plots linear over 0.15–4.0 µg/mL for OT, 5–1000 µg/mL for NOR and 3–125 µg/mL for DIC. The lower limits of detection (LOD) were found to be 50 ng/mL for OT, and 1 µg/mL for NOR and DIC. The method was validated for the analysis of drugs in milk samples and pharmaceutical preparations with recovery of drugs within the range 96–100% with RSD 0.9–2.8%. Copyright © 2009 John Wiley & Sons, Ltd.     

Electrochemical study of the effect of functionalized nickel nanoparticles on cellular uptake of leukemia cancer cells in vitro

In this study, we have fabricated the functionalized nickel nanoparticles and investigated their effects on cellular uptake of quercetin in leukemia K562 cancer cells by using electrochemical assay. The results indicate that nickel nanoparticles could efficiently enhance the quercetin uptake and increase the intracellular accumulation in cancer cells, implying the great potential of functionalized nickel nanoparticles in target cancer therapy.     

Non-aqueous capillary electrophoresis for separation and simultaneous determination of fraxin, esculin and esculetin in Cortex fraxini and its medicinal preparations

A non-aqueous capillary electrophoresis method has been developed for the separation and simultaneous determination of fraxin, esculin and esculetin in Cortex fraxini and its preparation for the first time. Optimum separation of the analytes was obtained on a 47 cm x 75 microm i.d. fused-silica capillary using a non-aqueous buffer system of 60 mM sodium cholate, 20 mM ammonium acetate, 20% acetonitrile and 3% acetic acid at 20 kV and 292 K, respectively. The relative standard deviations (RSDs) of the migration times and the peak heights of the three analytes were in the range of 0.23-0.28 and 2.12-2.60%, respectively. Detection limits of fraxin, esculin and esculetin were 0.1557, 0.4073 and 0.5382 microg/mL, respectively. In the tested concentration range, good linear relationships (correlation coefficients 0.9995 for fraxin, 0.9999 for esculin and 0.9992 for esculetin) between peak heights and concentrations of the analytes were observed. This method has been successfully applied to simultaneous determination of the three bioactive components with the recoveries from 90.2 to 109.2% in the five samples.     

LC–MS/MS method development for quantification of doxorubicin and its metabolite 13‐hydroxy doxorubicin in mice biological matrices: Application to a pharmaco‐delivery study

This study describes the development of simple, rapid and sensitive liquid chromatography tandem mass spectrometry method for the simultaneous analysis of doxorubicin and its major metabolite, doxorubicinol, in mouse plasma, urine and tissues. The calibration curves were linear over the range 5–250 ng/mL for doxorubicin and 1.25–25 ng/mL for doxorubicinol in plasma and tumor, over the range 25–500 ng/mL for doxorubicin and 1.25–25 ng/mL for doxorubicinol in liver and kidney, and over the range 25–1000 ng/mL for doxorubicin and doxorubicinol in urine. The study was validated, using quality control samples prepared in all different matrices, for accuracy, precision, linearity, selectivity, lower limit of quantification and recovery in accordance with the US Food & Drug Administration guidelines. The method was successfully applied in determining the pharmaco‐distribution of doxorubicin and doxorubicinol after intravenously administration in tumor‐bearing mice of drug, free or nano‐formulated in ferritin nanoparticles or in liposomes. Obtained results demonstrate an effective different distribution and doxorubicin protection against metabolism linked to nano‐formulation. This method, thanks to its validation in plasma and urine, could be a powerful tool for pharmaceutical research and therapeutic drug monitoring, which is a clinical approach currently used in the optimization of oncologic treatments.     

Measurement of alkaline phosphatase isoenzymes in individual mouse bone marrow fibroblast cells based on capillary electrophoresis with on-capillary enzyme-catalyzed reaction and electrochemical detection

A novel method for the determination of alkaline phosphatase (ALP) isoenzymes in individual fibroblast cells of mouse bone marrow was developed by combining capillary electrophoresis with an on-capillary enzyme-catalyzed reaction and electrochemical detection. In this method, a single an cell, followed by 5.0 x 10(-2) mol/L Na2B4O7- 3.0 x 10(-2) mol/L NaCl (pH 9.8) as cell lysis solution, was injected into the inlet of the separation capillary by electromigration. The cell was lysed by applying a voltage of 2 kV. The ALP isoenzymes in the cell were preseparated at 20 kV for 1 min, and then allowed to react for 30 min with disodium phenyl phosphate as enzyme substrate in the running buffer. ALP converted disodium phenyl phosphate into its product, phenol, at a relatively high reaction rate without consumption, with resultant amplification of the signal on prolonged reaction time, producing an adequate amount of product for final detection. A mass detection limit as low as 3.5 x 10(-21) mol/L (corresponding to 1.5 nU) was achieved. Finally, the two zones of products generated by ALP isoenzymes were detected at the outlet of the capillary by using the end-capillary amperometric detection at a carbon fiber microdisk bundle electrode with a constant potential.     

Determination of quinolizidine alkaloids in Sophora flavescens and its preparation using capillary electrophoresis

A simple and accurate capillary electrophoresis method was developed for the determination of four quinolizidine alkaloids in Sophora flavescens and Kuhuang injection. Optimum separation of the analytes was obtained on a 65 cm x 75 microm i.d. uncoated fused-silica capillary using a aqueous buffer system of 60 mmol L(-1) sodium borate at pH 8.5, with applied voltage and capillary temperature of 12 kV and 25 degrees C, respectively. Detection wavelength was set at 204 nm and jatrorrhizine was used as the internal standard. Good linear relationships between peak-area ratios and concentrations of the analytes were observed over the concentration range 0.044-0.792 mg mL(-1) for matrine, 0.142-1.926 mg mL(-1) for oxymatrine, 0.0377-0.3393 mg mL(-1) for sophocarpine and 0.0664-1.062 mg mL(-1) for sophoridine. The recoveries of four alkaloids ranged between 93.08 and 101.4% with relative standard deviations from 0.7 to 9.2% (n = 6) as determined by standard addition. The limits of detection for four alkaloids were determined to be over the range 8.8-48.0 microg mL(-1). Contents of four alkaloids in Sophora flavescens and three alkaloids in Kuhuang injection were successfully determined under the optimum conditions.     

Study of the peak broadening due to detection in the electrophoretic separation of DNA by CE and microchip CE and the application of image sensor for ultra‐small detection cell length

Narrow peaks are important to high‐resolution and high‐speed separation of DNA fragments by capillary electrophoresis and microchip capillary electrophoresis. Detection cell length is one of the broadening factors, which is often ignored in experiments. However, is it always safe to neglect detection cell length under any condition? To answer this question, we investigated the influence of detection cell length by simulation and experiments. A parameter named as detection cell length ratio was proposed to directly compare the detection cell length and the spatial length of sample band. Electrophoretic peaks generated by various detection cell length ratios were analyzed. A simple rule to evaluate the peak broadening due to detection cell length was obtained. The current states of the detection cell length of detection system and their reliabilities in capillary electrophoresis and microchip capillary electrophoresis were analyzed. Microchip capillary electrophoresis detection with an ultra‐small detection cell length of 0.36 μm was easily achieved by using an image sensor.     

Dual polarization interferometric and capillary electrophoretic analysis of supported lipid bilayer constructed on silica-based surface: Evaluation of its anti-protein adsorption effect

Supported lipid bilayer (SLB) has been demonstrated as a model of cell membranes with prospective bioanalytical or biotechnological applications. In this study, the formation of SLB and their potential biofunctionality against protein adsorption were investigated by Dual Polarization Interferometry (DPI) and Capillary Electrophoresis (CE). DPI studies on different formulations of double-chained, zwitterionic phospholipidlipids, allow the process of bilayer formation to be followed in situ and in real time. Furthermore the anti-protein adsorption effect provided by the various formulated SLBs was examined by DPI. In addition, the SLB coatings of the same lipid formulations were subsequently employed in CE experiments as a pseudo-stationary phase for demonstrating more efficient separation of alkaline protein standard mixtures. SLB-assisted CE was found to be capable of separating 4 alkaline proteins (protonated at neutral pH). This study demonstrates the applicability of DPI to monitor the process of SLB formation; and our findings, obtained by both DPI and CE, confirm that the presence of the SLB reduced drastically the problematic interactions between cationic, alkaline proteins and the negatively charged silica capillary wall, leading to better recovery and efficient separation of the proteins under investigation.     

Sorting Semiconducting Single‐Walled Carbon Nanotubes by Water‐Soluble Polyfluorene Assisted Electrophoresis and Its Application in Field‐effect Transistors

We report a considerably promising method based on agarose gel electrophoresis (AGE) to separate single‐walled carbon nanotubes by adding a water‐soluble polyfluorene (w‐PFO) as surfactant into the agarose gel. In this effective method, the AGE/w‐PFO gel network will trap more semiconducting single‐walled carbon nanotubes (SWNTs) with the assistance of w‐PFO, for the strong interaction between w‐PFO and semiconducting species. The optical absorbance, photoluminescence emission and resonant Raman scattering characterization were used to verify the separation effect. The purity of separated semiconducting species is as high as (98±1)%. The demonstrated field effect transistors give the on/off ratio and mobility about 27000 and 10.2 cm²·V^?1·s^?1, respectively.     

Determination of neurotransmitters in PC 12 cells by microchip electrophoresis with fluorescence detection

A sensitive fluorescence detection system with an Hg-lamp as the excitation source and a photon counter as the detector for microchip CE (MCE) has been developed. O-Phthaldialdehyde (OPA, lambda(ex) = 340 nm) was employed to label the catecholamine neurotransmitters such as dopamine (DA), norepinephrine (NE), and amino acid neurotransmitters including alanine (Ala), taurine (Tau), glycine (Gly), glutamic acid (Glu), and aspartic acid (Asp). The separation of seven derivatized neurotransmitters was successfully performed in MCE and the detection limits (S/N = 3) for DA, NE, Ala, Tau, Gly, Glu, and Asp were 0.85, 0.49, 0.23, 0.15, 0.13, 0.18, and 0.29 fmol, respectively. The system was then successfully applied for separation and determination of neurotransmitters in rat pheochromocytoma (PC 12) cells, and the average amounts of analyte per cell from a cell population were 2.5 fmol for DA, 3.3 fmol for Ala, 8.2 fmol for Tau, 4.0 fmol for Gly, and 1.9 fmol for Glu, respectively. By single-cell injection mode, electrophoresis separation and quantitative measurement of Glu in individual PC 12 cells was obtained. The average value of Glu per cell from single PC 12 cells analysis was found to be 3.5 +/- 3.1 fmol.     

Determination of ascorbic acid in individual rat hepatocyte cells based on capillary electrophoresis with electrochemiluminescence detection

A novel method to detect ascorbic acid (AA) in individual rat hepatocyte cells was developed by combining CE with electrochemiluminescence (ECL) based on tris(2,2'-bipyridine) ruthenium(II) (Ru(bpy)(3)2+). A single cell, followed by 0.1% SDS as cell lysis solution, was injected into the inlet of the separation capillary by electromigration. After optimizing the analytical conditions, the RSDs of migration time and peak height were 0.38% and 2.6% for 1.0x10(-5) M AA (n=10), respectively. The linear range of AA was from 1.0x10(-8) to 5.0x10(-5) M with a correlation coefficient of 0.9979 and the LOD (S/N=3) was estimated to be 1.0x10(-8) M. This method has been successfully applied to determine AA in single rat hepatocytes and the amount of AA in seven rat hepatocytes ranged from 16 to 62 fmol. The above results demonstrated that CE coupled with ECL is convenient, sensitive, and will become an attractive alternative method for single-cell analysis.     

Sequential-dissociation kinetics of non-covalent complexes of DNA with multiple proteins in separation-based approach: General theory and its application

Binding of multiple proteins to DNA is crucial in many regulatory cellular processes. The kinetics of assembly and disassembly of DNA–multiple protein complexes is very difficult to study in detail due to the lack of suitable experimental approaches. A separation-based approach has been recently proposed to resolve disassembly kinetics of such complexes. While conceptually simple, the separation-based approach generates experimental data with very complex patterns. The analysis of these patterns is a challenging problem on its own. Here we report on a mathematical approach that can extract a solution for the experimental data obtained in separation-based analysis of sequential dissociation of a DNA complex with multiple proteins. This case describes the dissociation of proteins one-by-one from the complex. Generally speaking, a mathematical solution of such problems requires calculations of multiple integrals. Our approach reduces this procedure to taking double integrals and constructing their superposition. We tested this approach with the experimental data obtained for three-step sequential dissociation of complexes of DNA with two protein copies.