A modular single-cell pipette microfluidic chip coupling to ETAAS and ICP-MS for single cell analysis

Accurate single-cell capture is a crucial step for single cell biological and chemical analysis. Conventional single-cell capturing often confront operational complexity, limited efficiency, cell damage, large scale but low accuracy, incompetence in the acquirement of nano-upgraded single-cell liquid. Flow cytometry has been widely used in large-scale single-cell detection, while precise single-cell isolation relies on both a precision operating platform and a microscope, which is not only extre...     

The use of internal standards in ICP-MS

Careful study of the matrix effect in ICP-MS showed that, in all cases studied, the magnitude of the signal suppression or enhancement depends in a regular way on the mass number. Hence, accurate correction for non-spectral interferences is only possible using an internal standard with mass number close to that of the analyte element(s). It is also shown that using an internal standard with mass number close to that of the analyte improves the precision. For both cases, the ionization energy of the internal standard seems to be of no or only secondary importance. To obtain optimal precision and accuracy, the internal standard should be selected as close in mass number as possible to that of the analyte element(s). When a number of elements over a considerable mass range are to be determined, several internal standards have to be used.     

Live single-cell molecular analysis by video-mass spectrometry.

The direct molecular analysis of a live single cell viewed under a video-microscope has been developed. The cell contents are sucked into a nano-electrospray tip, and hundreds of peaks of ionic compounds of low molecular weight are detected by nano-ESI Q-TOF mass spectrometry (MS). Cell-specific MS peaks in a single mouse-embryonic fibroblasts cell are extracted by a t-test, and one of the peaks is proceeded to MS/MS analysis for molecular identification. This method is direct and quick to identify the molecules of a cell with simultaneous observation by a video-microscope.     

Nanofluidics for single-cell analysis

Living single-cell analysis is vital for cell biology, disease pathology, drug discovery and medical treatment. It is of great significance to reveal the law of creature and to explore the mechanism of serious disease. The conventional single cell analysis focuses on a large number of cells or cell lysis, in order to obtain the average information about cells. Therefore, it fails to analyze the real-time and continuous data of differences between the individual cells, thus limiting the developme...     

A single-cell analysis of myogenic dedifferentiation induced by small molecules

An important direction in chemical biology is the derivation of compounds that affect cellular differentiation or its reversal. The fragmentation of multinucleate myofibers into viable mononucleates (called cellularization) occurs during limb regeneration in urodele amphibians, and the isolation of myoseverin, a trisubstituted purine that could apparently activate this pathway of myogenic dedifferentiation in mammalian cells, generated considerable interest. We have explored the mechanism and outcome of cellularization at a single-cell level, and we report findings that significantly extend the previous work with myoseverin. Using a panel of compounds, including a triazine compound with structural similarity and comparable activity to myoseverin, we have identified microtubule disruption as critical for activation of the response. Time-lapse microscopy has enabled us to analyze the fate of identified mononucleate progeny, and directly assess the extent of dedifferentiation.     

Parallel single-cell analysis microfluidic platform

We report a PDMS microfluidic platform for parallel single-cell analysis (PaSCAl) as a powerful tool to decipher the heterogeneity found in cell populations. Cells are trapped individually in dedicated pockets, and thereafter, a number of invasive or non-invasive analysis schemes are performed. First, we report single-cell trapping in a fast (2-5 min) and reproducible manner with a single-cell capture yield of 85% using two cell lines (P3x63Ag8 and MCF-7), employing a protocol which is scalable and easily amenable to automation. Following this, a mixed population of P3x63Ag8 and MCF-7 cells is stained in situ using the nucleic acid probe (Hoechst) and a phycoerythrin-labeled monoclonal antibody directed at EpCAM present on the surface of the breast cancer cells MCF-7 and absent on the myeloma cells P3x63Ag8 to illustrate the potential of the device to analyze cell population heterogeneity. Next, cells are porated in situ using chemicals in a reversible (digitonin) or irreversible way (lithium dodecyl sulfate). This is visualized by the transportation of fluorescent dyes through the membrane (propidium iodide and calcein). Finally, an electrical protocol is developed for combined cell permeabilization and electroosmotic flow (EOF)-based extraction of the cell content. It is validated here using calcein-loaded cells and visualized through the progressive recovery of calcein in the side channels, indicating successful retrieval of individual cell content.     

Mechanical response analysis and power generation by single-cell stretching.

To harvest useful information about cell response due to mechanical perturbations under physiological conditions, a cantilever-based technique was designed, which allowed precise application of arbitrary forces or deformation histories on a single cell in vitro. Essential requirements for these investigations are a mechanism for applying an automated cell force and an induced-deformation detection system based on fiber-optical force sensing and closed loop control. The required mechanical stability of the setup can persist for several hours since mechanical drifts due to thermal gradients can be eliminated sufficiently (these gradients are caused by local heating of the cell observation chamber to 37 degrees C). During mechanical characterization, the cell is visualized with an optical microscope, which enables the simultaneous observation of cell shape and intracellular morphological changes. Either the cell elongation is observed as a reaction against a constant load or the cell force is measured as a response to constant deformation. Passive viscoelastic deformation and active cell response can be discriminated. The active power generated during contraction is in the range of Pmax= 10(-16) Watts, which corresponds to 2500 ATP molecules s(-1) at 10 k(B)T/molecule. The ratio of contractive to dissipative power is estimated to be in the range of 10(-2). The highest forces supported by the cell suggest that about 10(4) molecular motors must be involved in contraction. This indicates an energy-conversion efficiency of approximately 0.5. Our findings propose that, in addition to the recruitment of cell-contractile elements upon mechanical stimulation, the cell cytoskeleton becomes increasingly crosslinked in response to a mechanical pull. Quantitative stress-strain data, such as those presented here, may be employed to test physical models that describe cellular responses to mechanical stimuli.     

Evaluation of semiquantitative analysis mode in ICP-MS

Semiquantitative analysis mode in inductively coupled plasma mass spectrometry (ICP-MS) has been popularly used for fast screening purposes. Although the benefit of it has been studied by many researchers, its performance of application in real-world routine analyses has not been reported.

In this study, we evaluated the reliability of semiquantitative analysis mode through inter-laboratory comparison using two different ICP-MS systems with one multi-element calibration standard. The suitability of semiquantitative analysis mode in routine analysis laboratory was demonstrated by evaluating its application in different laboratories and in real production laboratory practices. Twenty one elements were measured, namely, Be, B, Al, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, As, Sr, Mo, Ag, Cd, Sn, Sb, Ba, Tl, and Pb in various fresh water reference samples. Good results concerning accuracy (relative percentage error within 10%) and reproducibility (relative standard deviation lower than 5%) were obtained in more than 90% analyzed samples at concentrations equal to or greater than 10 times the detection limit (DL). Semiquantitative analysis mode also enabled the determination of elements that are not present in the calibration standard. The results demonstrated the potential of semiquantitative analysis mode as a reliable approach in routine laboratory determination of simple matrices, where high throughput and cost-effectiveness are desired, as well as in emergency situations where speed of analysis is critical and quite often limited sample information is available.     

Analysis of single-cell differences by use of an on-chip microculture system and optical trapping

A method is described for continuous observation of isolated single cells that enables genetically identical cells to be compared; it uses an on-chip microculture system and optical tweezers. Photolithography is used to construct microchambers with 5-microm-high walls made of thick photoresist (SU-8) on the surface of a glass slide. These microchambers are connected by a channel through which cells are transported, by means of optical tweezers, from a cultivation microchamber to an analysis microchamber, or from the analysis microchamber to a waste microchamber. The microchambers are covered with a semi-permeable membrane to separate them from nutrient medium circulating through a "cover chamber" above. Differential analysis of isolated direct descendants of single cells showed that this system could be used to compare genetically identical cells under contamination-free conditions. It should thus help in the clarification of heterogeneous phenomena, for example unequal cell division and cell differentiation.     

Microfluidic techniques for dynamic single-cell analysis

Dynamic single-cell analysis is a very important and frontier research field of single-cell analysis. Microfluidic techniques have become new and effective tools for precise, high-throughput, automatic analysis of single-cell dynamic process. This review aims to give an overview of dynamic single-cell analysis methods based on microfluidic platforms, with emphasis on the recent developments of microfluidic devices and its application to real-time dynamic monitoring of the signal molecules release from single living cell with temporal and spatial resolution, dynamic gene expression in single cells, the cell death dynamic events at the level of a single cell, and direct cell—cell communication between individual cell pairs.     

The analysis of high-purity noble metals and their salts by ICP-MS

Ongoing work is being carried out at Mintek to establish methods for the determination of trace levels of impurities in high-purity noble metals and their salts. The sample-preparation methods are outlined, and the optimum instrumental parameters that were established are tabulated. Spectral interferences arising from the presence of a matrix element at high concentration levels, including abundance sensitivity overlap and the formation of noble-metal oxides, are discussed. Accuracy was established by the comparison of the results with those obtained by a DC-arc method, and by spike recovery tests. The precision of measurement was found to vary from 0.72 to 49% S(r) for concentrations of between 15 and 0.5 gmg/g, respectively.     

微波消解ICP-MS快速测定生物样品中的多种元素

建立了微波辅助HNO3消解样品,ICP-MS快速测定生物样品中Ti、Cr、Mn、Fe、Co、Ni、Cu、Zn、Ge、As、Se、Sr、Mo、Ag、Cd、I、Ba、Hg、Tl、Pb、Bi共21种微量及痕量元素。通过在线加入内标来校正基体效应和信号漂移对测量所造成的影响。各元素线性相关系数在0.9990以上,RSD小于6.0%。用本方法对国家标准样品GBW07601a(头发),GBW10010(大米),GBW10016(茶叶),GBW10023(紫菜)进行分析,结果满意。方法能满足生物样品痕量分析的要求。     

Use of chromatographic pre-concentration for routine uranium bioassay analysis by ICP-MS

Routine monitoring of urine is an effective way to detect occupational intake of radioactive material. Historically, determinations of uranium isotopic ratios have been performed by radiochemical separation followed by alpha spectrometry. With recent advancements in technology, inductively coupled plasma-mass spectrometry (ICP-MS) has become widely available for the determination of trace metals as well as radioactive nuclides with long half-lives, such as ²³⁸U in urine. Furthermore, ICP-MS measurements of ²³⁸U do not require radiochemical separation since the number of atoms in the sample is determined instead of the number of alpha particles emitted. However, this method does not provide good sensitivity for the determination of ²³⁵U due to its shorter half-life. An improved procedure using pre-concentration of uranium and determination by ICP-MS decreases the detection limit by a factor of ten or greater with only slight increase in total analysis time. The method also has the capability of accurately determining the isotopic ratio of the sample, which is very important in cases where enriched or depleted uranium is involved.     

Multielemental analysis of Mn-Fe nodules by ICP-MS: optimisation of analytical method

Two acid digestion procedures (microwave-assisted and room temperature) were developed for the quantitative analysis of ferromanganese nodules by inductively coupled plasma double focusing sector field mass spectrometry (ICP-SFMS). Different compositions of the acid mixture, dilution factors and corrections for spectral interferences were tested. A combination of nitric, hydrochloric and hydrofluoric acids is necessary for complete sample digestion, with lowest acid to sample ratios (v/m) of 15 and 1.5, respectively, for the last two acids. Sample dilution factors higher than 2 x 10(4) should be used in order to decrease matrix effects and provide robust long-term instrumental operation. In spite of high dilution, method detection limits in the sub-microg g(-1) range were obtained for 54 out of 71 elements tested, due to the high detection capability of ICP-SFMS, as well as the special care taken to ensure the purity of reagents, to clean the instrument sample introduction system and to minimise sample handling. Owing to the presence of unresolved (at the resolution available) spectral interferences, accurate determination of Au, Hg, Os, Pd, Re and Rh is impossible without matrix separation. The accuracy of the entire analytical method was tested by the analysis of two nodule reference materials. The results generated agreed to within +/-2% for about 10, within +/-10% for more than 40 and within +/-20% for about 50 of 53 elements for which certified, recommended or literature values are available. A precision better than 3%, expressed as the between-digestion relative standard deviation (n = 4), was obtained for the majority of elements, except in cases limited by low analyte concentrations.     

Strategy for water analysis using ICP-MS

The developed strategy permits determination in three steps of sixty-seven elements using inductively coupled plasma mass spectrometry (ICP-MS). Sodium, Mg, Si, S, Cl, K, and Ca are determined in a first step; B, Al, P, Cr, Fe, Mn, Ni, Cu, Zn, As, Se, Ag, Cd, Sb, Ba, Hg, and Pb are determined in a second step; and Li, Be, Ti, V, Co, Ga, Ge, Br, Rb, Sr, Y, Zr, Nb, Mo, Sn, Te, I, Cs, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, Ta, W, Pt, Au, Tl, Bi, Th, and U are analyzed in a third step. The figures of merit obtained are adequate to carry out water quality monitoring and other hydrochemical studies, such those based in the application of hydrochemical fingerprinting to water management.     

Elemental analysis of Pterocarpus Santalinus by PIXE and ICP-MS: chemometric approach

Journal of Radioanalytical and Nuclear Chemistry - A biomonitoring study of air pollution using lichen Flavoparmelia caperata (L.) Hale was conducted at indoor and outdoor environments of primary...     

icp-ms法测定化妆品中铬的方法

用电感耦合等离子体质谱法(ICP-MS),建立了不同化妆品基质中铬的测定分析方法。样品预处理采用以HNO3水溶液作消化试剂的微波消解方法,并对5种不同化妆品基质中消化试剂的用量进行了比较。优化选择电感耦合等离子体质谱仪的工作参数,考察了测量过程中的基体效应及质谱干扰,针对不同化妆品样品,选择52Cr、53Cr作为测量同位素,72Ge为内标元素,对试样进行定量分析,有效地补偿基体效应所引起的测量偏差。实验证明,52Cr、53Cr的检测结果差异不大,均能满足化妆品中铬的测定要求。对照分析了参考标准物质。铬质量浓度在0.1~100μg/L范围内,校正曲线的相关系数为0.9999;铬添加质量浓度为0.5mg/kg,添加平均回收率为85.3%~104%;相对标准偏差(RSD)为1.5%~7.3%,52Cr检出限为0.052μg/kg,53Cr检出限为0.036μg/kg。     

电感耦合等离子体质谱法测定米托坦中的汞

介绍了电感耦合等离子体质谱法(ICP-MS)测定米托坦中的汞,重点从消解方式、酸体系和微波消解程序等方面对样品前处理方法进行了优化。在优化的实验条件下,本方法检出限为0.005 mg/kg,6次平行测定结果的相对标准偏差为7.7%,加标回收率为82.3%～85.7%。本方法灵敏度高、稳定性好,而且准确度高。