Behavior of Bacteria in the Inductively Coupled Plasma: Atomization and Production of Atomic Ions for Mass Spectrometry

Determination of carbon in microplastics and single cells by total consumption microdroplet ICP-TOFMS

Recently, spICP-MS analyses of microplastics have demonstrated that the detection capabilities of ICP-MS are sufficient to determine the size and composition of such materials. However, solution nebulization or microdroplet generation limits the sizes of droplets, microparticles, or cells that can be efficiently introduced into commonly used horizontal ICP-MS configurations. Therefore, we introduced the development of a downward-pointing ICP coupled to a time-of-flight mass spectrometer (ICP-TOFMS), which enables quantitative transport of large microdroplets (diameters up to 90 µm) into the ICP. Here, we report the capabilities of downward ICP-TOFMS for the quantitative analysis of single cells and microplastic particles. For calibration of element mass amount per particle or cell, microdroplets (70 µm diameter) composed of multielement solutions were measured by ICP-TOFMS. Microplastic beads (polystyrene) and spleenocyte cells were then also embedded in microdroplets and measured by ICP-TOFMS with ion optics optimized to determine the signals from 12C+ and other isotopes of interest, including 140Ce, 153Eu, 165Ho, and 175Lu from the REE beads and 31P for the cells. The results achieved using the prototype instrument of a vertical downward-pointing ICP-TOFMS demonstrate that such a plasma configuration is well suited to analyze microplastics and single cells. For single microbead and cell analyses, the critical mass for carbon was 4.8 pg, and the mean determined carbon mass amounts were 14 and 23 pg, respectively. For the microbead analysis, the detected carbon mass corresponds to a particle diameter of 2.93 ± 0.24 µm, which is consistent with the scanning (transmission) electron microscopy-determined diameter of 2.97 ± 0.04 µm. Furthermore, in the analysis of spleenocyte cells, carbon and phosphorus masses were determined to be correlated.

Multielement analysis of single red blood cells by single cell - inductively coupled plasma tandem mass spectrometry

A method for the analysis of essential metals (Fe, Cu, Mg, and Zn) and non-metals (P, S) in single red blood cells was developed by single cell (SC)-ICP-MS. The use of a triple quadrupole configuration (MS/MS) enabled an effective elimination of polyatomic interferences, which affect the accuracy of ICP-MS analysis using a single quadrupole mass analyzer. Fixation with glutaraldehyde for at least 90 days was developed to improve the quantification of elements in a single red blood cell. The experimental conditions were optimized while special attention was paid to the residence time of analytes in the plasma. Addition of a surfactant (0.05% (v/v) Tween80®) improved quantification of elements in fixed red blood cells. The detection limits obtained by SC-ICP-MS/MS were lower than for ICP-MS, especially for S and P (3 fg and 1.7 fg. cell-1 instead of 163 and 6.3 fg. cell-1, respectively).

Expanding the boundaries of atomic spectroscopy at the single-cell level: critical review of SP-ICP-MS, LIBS and LA-ICP-MS advances for the elemental analysis of tissues and single cells

Metals have a fundamental role in microbiology, and accurate methods are needed for their identification and quantification. The inability to assess cellular heterogeneity is considered an impediment to the successful treatment of different diseases. Unlike bulk approaches, single-cell analysis allows elemental heterogeneity across genetically identical populations to be related to specific biological events and to the effectiveness of drugs. Single particle-inductively coupled plasma-mass spectrometry (SP-ICP-MS) can analyse single cells in suspension and measure this heterogeneity. Here we explore advances in instrumental design, compare mass analysers and discuss key parameters requiring optimisation. This review has identified that the effect of pre-treatment of cell suspensions and cell fixation approaches require further study and novel validation methods are needed as using bulk measurements is unsatisfactory. SP-ICP-MS has the advantage that a large number of cells can be analysed; however, it does not provide spatial information. Techniques based on laser ablation (LA) enable elemental mapping at the single-cell level, such as laser-induced breakdown spectroscopy (LIBS) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). The sensitivity of commercial LIBS instruments restricts its use for sub-tissue applications; however, the capacity to analyse endogenous bulk components paired with developments in nano-LIBS technology shows great potential for cellular research. LA-ICP-MS offers high sensitivity for the direct analysis of single cells, but standardisation requires further development. The hyphenation of these trace elemental analysis techniques and their coupling with multi-omic technologies for single-cell analysis have enormous potential in answering fundamental biological questions.

All-in-One Microfluidic Chip for Online Labeling, Separating, and Focusing Rare Circulating Tumor Cells from Blood Samples Followed by Inductively Coupled Plasma Mass Spectrometry Detection

Circulating tumor cell (CTC) detection is essential for early cancer diagnosis and evaluating treatment efficacy. Despite the growing interest in isolating CTCs and further quantifying surface biomarkers at the single-cell level, highly efficient separation of rare CTCs from massive blood cells is still a big challenge. Here, we developed an all-in-one microfluidic chip system for the immunolabeling, magnetic separation, and focusing of HepG2 cells (as a CTC model) and online combined it with single cell-inductively coupled plasma mass spectrometry (SC-ICP-MS) for quantitative analysis of the asialoglycoprotein receptor (ASGPR) on single HepG2 cells. Lanthanide-labeled anti-ASGPR monoclonal antibody and antiepithelial cell adhesion molecule-modified magnetic beads were prepared as signal and magnetic probes, respectively. Target cells were highly efficiently labeled with signal and magnetic probes in the mixing zone of the microfluidic chip and then focused and sorted in the separation zone by specific magnetic separation techniques to avoid matrix contamination. The average cell recovery of HepG2 cells was derived to be 94.1 ± 5.7% with high separation efficiency and purity. The sorted cells with signal probes were detected for enumeration and quantification of ASGPR on their surface by SC-ICP-MS. The developed method showed good specificity and high sensitivity, detecting an average of (1.0 ± 0.2) × 105 ASGPR molecules per cell surface. This method can be used for absolute quantitative analysis of ASGPR on the surface of single hepatocellular carcinoma cells in real-world samples, providing a highly efficient analytical platform for studying targeted drug delivery in cancer therapy.

Improving the Detectability of Microplastics in River Waters by Single Particle Inductively Coupled Plasma Mass Spectrometry

Detection of microplastics in environmental samples requires fast, sensitive and selective analytical techniques, both in terms of the size of the microparticles and their concentration. Single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) allows the detection of plastic particles down to ca. 1 µm and down to concentrations of 100 particles per mL. In SP-ICP-MS, detection of carbon-containing particles is hampered by the presence of other forms of carbon (carbonates, organic matter, microorganisms…). An acidic pre-treatment of river water samples with 10% (v/v) nitric acid for 24 h allowed the reduction of the presence of dissolved carbon to ultrapure water levels and the digestion of potential microorganisms in the samples, recovering polystyrene microparticles up to 80%. Carbon-containing particles were detected in most of the samples analysed from Spanish and French Pyrenean rivers. The presence of microplastics in these samples was confirmed by Raman microscopy and their morphology was defined by electron microscopy combined with energy-dispersive X-ray spectroscopy. The developed SP-ICP-MS method is suitable for the rapid screening of river waters for the presence of microplastics, which can then be analysed by inherently slower but more selective techniques (e.g., Raman microscopy).

Risk assessment of silver and microplastics release from antibacterial food containers under conventional use and microwave heating

The evaluation of the migration of ionic silver and nanoparticulated silver (AgNPs) from antimicrobial plastic packaging to food is crucial to ensure its safety. Migration assays were performed on reusable silver-containing polypropylene (PP) food containers and a silicone baby bottle, using food simulants, under conventional or microwave heating and repeated use. The PP containers released significant amounts of silver, increasing with temperature, contact time, acidity and lower crystallinity. Silver migration in the silicone bottle was much lower. Risk assessment of released silver was done considering European authorities safety recommendations, with some containers far exceeding these levels. No significant AgNPs release was detected in the simulants by single particle-ICPMS. Silver-containing microplastics and silicone microparticles were detected by SEM in the food simulants after the migration assays. Consumers may be continuously exposed to the harmful effects of ionic silver and microplastics, which can potentially lead to health issues.

Determination and localization of specific proteins in individual ARPE-19 cells by single cell and laser ablation ICP-MS using iridium nanoclusters as label

Single cell-inductively coupled plasma-mass spectrometry (sc-ICP-MS) and laser ablation (LA)-ICP-MS have been complementary employed to develop a comprehensive study of APOE and claudin-1 expression in ARPE-19 cells submitted to a glucose treatment (100 mM, 48 h) that induces oxidative stress conditions. Results were compared with control cells. The determination of the two proteins by ICP-MS was sequentially carried out using specific immunoprobes labelled with IrNCs that offer a huge amplification (1760 ± 90 atoms of Ir on average). A novel sample introduction system, the microFAST Single Cell set-up, was employed for sc-ICP-MS analysis. This introduction system resulted in a cellular transport efficiency of 85 ± 9% for ARPE-19 cells (91 ± 5% using a PtNPs standard). After the proper immunocytochemistry protocol with the specific IrNCs immunoprobes in cell suspensions (sc-ICP-MS), the mass of APOE and claudin-1 in individual ARPE-19 cells was obtained. Average detection limits per cell by sc-ICP-MS were 0.02 fg of APOE and 3 ag of claudin-1. The results of sample analyses obtained by sc-ICP-MS were validated with commercial ELISA kits. The distribution of both target proteins in individual cells (fixated in the chamber wall) was unveiled by LA-ICP-MS. The high amplification provided by the IrNCs immunoprobes allowed the identification of APOE and claudin-1 within individual ARPE-19 cells. High resolution images were obtained using a laser spot of 2 × 2 μm.

Review about Powerful Combinations of Advanced and Hyphenated Sample Introduction Techniques with Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) for Elucidating Trace Element Species in Pathologic Conditions on a Molecular Level

Element analysis in clinical or biological samples is important due to the essential role in clinical diagnostics, drug development, and drug-effect monitoring. Particularly, the specific forms of element binding, actual redox state, or their spatial distribution in tissue or in single cells are of interest in medical research. This review summarized exciting combinations of sophisticated sample delivery systems hyphenated to inductively coupled plasma-mass spectrometry (ICP-MS), enabling a broadening of information beyond the well-established outstanding detection capability. Deeper insights into pathological disease processes or intracellular distribution of active substances were provided, enabling a better understanding of biological processes and their dynamics. Examples were presented from spatial elemental mapping in tissue, cells, or spheroids, also considering elemental tagging. The use of natural or artificial tags for drug monitoring was shown. In the context of oxidative stress and ferroptosis iron, redox speciation gained importance. Quantification methods for Fe2+, Fe3+, and ferritin-bound iron were introduced. In Wilson’s disease, free and exchangeable copper play decisive roles; the respective paragraph provided information about hyphenated Cu speciation techniques, which provide their fast and reliable quantification. Finally, single cell ICP-MS provides highly valuable information on cell-to-cell variance, insights into uptake of metal-containing drugs, and their accumulation and release on the single-cell level.

Living in a transient world: ICP-MS reinvented via time-resolved analysis for monitoring single events

After 40 years of development, inductively coupled plasma-mass spectrometry (ICP-MS) can hardly be considered as a novel technique anymore. ICP-MS has become the reference when it comes to multi-element bulk analysis at (ultra)trace levels, as well as to isotope ratio determination for metal(loid)s. However, over the last decade, this technique has managed to uncover an entirely new application field, providing information in a variety of contexts related to the individual analysis of single entities (e.g., nanoparticles, cells, or micro/nanoplastics), thus addressing new societal challenges. And this profound expansion of its application range becomes even more remarkable when considering that it has been made possible in an a priori simple way: by providing faster data acquisition and developing the corresponding theoretical substrate to relate the time-resolved signals thus obtained with the elemental composition of the target entities. This review presents the underlying concepts behind single event-ICP-MS, which are needed to fully understand its potential, highlighting key areas of application (e.g., single particle-ICP-MS or single cell-ICP-MS) as well as of future development (e.g., micro/nanoplastics).

Ruthenium red: a highly efficient and versatile cell staining agent for single-cell analysis using inductively coupled plasma time-of-flight mass spectrometry

Staining of biological cells with heavy metals can increase their visibility in mass spectrometry. In this study, the potential of ruthenium red (RR) as a staining agent for single-cell analysis by inductively coupled plasma time-of-flight mass spectrometry (SC-ICP-TOF-MS) is explored using two different yeast strains and one algal species. Time-of-flight mass spectrometry allows the simultaneous detection of Ru and multiple intrinsic elements in single cells. Ru has a better correlation with Mg than with P in Saccharomyces cerevisiae (S. cerevisiae) cells. For the three tested strains, the staining efficiency of RR exceeded 96%; the staining strengths were 30-32 ag μm^-2 for the yeast cells and 59 ag μm^-2 for the algal cells. By deriving the cell volume of single cells from their Ru mass, the concentration of Mg and P in individual cells of S. cerevisiae can be calculated. Elemental concentrations of Mg and P were highly variable in the cell individuals, with their 25-75 percentile values of 0.10-0.19 and 0.76-2.07 fg μm^-3, respectively. RR staining has several advantages: it is fast, does not affect cell viability and is highly efficient. Provided that the shape of the individual cells of a culture is similar, Ru staining allows the elemental content to be directly correlated with the cell volume to accurately calculate the intracellular concentration of target elements in single cells. Therefore, RR can be a promising cell staining agent for future application in SC-ICP-TOF-MS research.

Determination of elemental distribution and evaluation of elemental concentration in single Saccharomyces cerevisiae cells using single cell-inductively coupled plasma mass spectrometry

Single-cell analysis using inductively coupled plasma mass spectrometry (SC-ICP-MS) is a method to obtain qualitative and quantitative information of the elemental content and distribution of single cells. Six intrinsic target elements were analyzed in yeast cells at different cell growth phases cultured in medium with different phosphorus concentrations (0, 7, 14 mM) to study its effect on cell growth and composition. SC-ICP-MS results were compared with those obtained by the acid digestion and the average ratio was 0.81. The limits of detection of this method were 0.08, 2.54, 12.5, 0.02, 0.02, and 0.08 fg cell-1 for Mg, P, K, Mn, Cu, and Zn, respectively. During the exponential growth phase, the cells exhibited higher elemental contents, wider distribution for most elements, and larger cell size in comparison to the stationary growth phase. Phosphorus-free conditions reduced the average P content in single cells of stationary growth phase from 650 to 80 fg. Phosphorus deficiency led to decreasing intracellular concentrations not only of P but also of K and Cu, and to increasing Zn concentration after 48 h. Mg maintained its concentration at ∼0.11 fg µm-3 and did not change significantly under the three investigated conditions after 48 h. Accordingly, Mg content was successfully used to estimate the intracellular concentration of other intrinsic elements in single yeast cells. SC-ICP-MS is suited to determine target elements in single yeast cells, and allows the study of heterogeneity of cell composition and effects of stressors on the elemental content, distribution, and concentrations of intrinsic elements.

Single-cell fucosylation breakdown: Switching fucose to europium

Fucosylation and its fucosidic linkage-specific motifs are believed to be essential to understand their distinct roles in cellular behavior, but their quantitative information has not yet been fully disclosed due to the requirements of ultra-sensitivity and selectivity. Herein, we report an approach that converts fucose (Fuc) to stable europium (Eu) isotopic mass signal on hard ionization inductively coupled plasma mass spectrometry (ICP-MS). Metabolically assembled azido-fucose on the cell surface allows us to tag them with an alkyne-customized Eu-crafted bacteriophage MS2 capsid nanoparticle for Eu signal multiplication, resulting in an ever lowest detection limit of 4.2 zmol Fuc. Quantitative breakdown of the linkage-specific fucosylation motifs in situ preserved on single cancerous HepG2 and paracancerous HL7702 cells can thus be realized on a single-cell ICP-MS platform, specifying their roles during the cancering process. This approach was further applied to the discrimination of normal hepatocellular cells and highly, moderately, and poorly differentiated hepatoma cells collected from real hepatocellular carcinoma tissues.

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Switching facile fucose to stable Eu mass signal on a single-cell ICP-MS platform

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Ever lowest LOD of 4.2 zmol FucAz was achieved using a Eu-decorated MS2 nanoparticle

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Single-cell breakdown of fucosidic linkage-specific motifs

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Discrimination of highly, moderately, and poorly differentiated HCC from normal ones

Argon Enclosed Droplet Based 3D Microfluidic Device Online Coupled with Time-Resolved ICPMS for Determination of Cadmium and Zinc in Single Cells Exposed to Cadmium Ion

Time-resolved (TRA)-ICPMS has become a booming subfield of single-cell analysis tools in recent years, while generation of single cells remains the major challenge. Microfluidic devices reveal their great capability and potential in encapsulation of single cells into water droplets. However, current strategies to pinch off droplets require a specific oil phase, which is not compatible to conventional ICPMS and makes the signal of cells in the water phase susceptible. Herein, we built a 3D water-in-gas microfluidic device (3D W/G MFD) with commercially available components, producing single cell droplet enclosed by argon gas. By simply tuning the flow rate of gas and water, the droplets were generated to encapsulate single cells, which significantly reduced the probability of the single signal coming from multiple cells by 1 or 2 orders of magnitude compared to direct injection. The developed oil-free 3D W/G MFD was more friendly to online coupling with TRA-ICPMS than water-in-oil devices. The effect of Cd²⁺ on HepG2 cells was studied by single cell detecting total Zn with 3D W/G MFD-TRA-ICPMS, and the variation of labile Zn was explored by flow cytometry with an N-(6-methoxy-8-quinolyl)-p-toluenesulfonamide probe. To the best of our knowledge, this work pioneered the exploration of variation in cellular metal content and speciation at the single-cell level, compensating for the deficiency of speciation analysis based on TRA-ICPMS and providing new insights into exploring the complexity of biology.

Inductively coupled plasma mass spectrometry based platforms for studies involving nanoparticle effects in biological samples

The widespread application of nanoparticles (NPs) in recent times has caused concern because of their effects in biological systems. Although NPs can be produced naturally, industrially synthesized NPs affect the metabolism of a given organism because of their high reactivity. The biotransformation of NPs involves different processes, including aggregation/agglomeration, and reactions with biomolecules that will be reflected in their toxicity. Several analytical techniques, including inductively coupled plasma mass spectrometry (ICP-MS), have been used for characterizing and quantifying NPs in biological samples. In fact, in addition to providing information regarding the morphology and concentration of NPs, ICP-MS-based platforms, such as liquid chromatography/ICP-MS, single-particle ICP-MS, field-flow fractionation (asymmetrical flow field-flow fractionation)-ICP-MS, and laser ablation-ICP-MS, yield elemental information about molecules. Furthermore, such information together with speciation analysis enlarges our understanding of the interaction between NPs and biological organisms. This study reports the contribution of ICP-MS-based platforms as a tool for evaluating NPs in distinct biological samples by providing an additional understanding of the behavior of NPs and their toxicity in these organisms.

Direct Infusion ICP-qMS of Lined-up Single-Cell Using an Oil-Free Passive Microfluidic System

When coupled online with mass spectrometry (MS), widely applied water-in-oil droplet-based microfluidics for single cell analysis met problems. For example, the oil phase rumpled the stability, efficiency, and accuracy of MS, the conventional interface between MS and the microfluidic chip suffered the low sample introduction efficiency, and the transportation rates sometimes unmatched the readout dwell times for transient signal acquisition. Considering cells are already "droplets" with hydrophilic surface and elastic hydrophobic membrane, we developed an oil-free passive microfluidic system (OFPMS) that consists of alternating straight-curved-straight microchannels and a direct infusion (dI) micronebulizer for inductively coupled plasma quadrupole-based mass spectrometry (ICP-qMS) of lined-up single-cell. OFPMS guarantees exact single cell isolation one by one just using a thermo-decomposable NH₄HCO₃ buffer, eliminating the use of any oil and incompatible polymer carriers. It is more flexible and facile to adapt to the dwell time of ICP-qMS owing to the adjustable throughput of 400 to 25000 cells/min and the controllable interval time of at least 20 ms between the lined-up adjacent single cells. Quantitative single-cell transportation and high detection efficiency of more than 70% was realized using OFPMS-dI-ICP-qMS exemplified here. Thus, cell-to-cell heterogeneity can be simply uncovered via the determination of metals in the individual cells.

Addressing the presence of biogenic selenium nanoparticles in yeast cells: analytical strategies based on ICP-TQ-MS

Complementary analytical strategies based on ICP-TQ-MS were used for the detection and characterization of selenium-containing nanoparticles in selenized yeast.

Evaluating the treatment effectiveness of copper-based algaecides on toxic algae Microcystis aeruginosa using single cell-inductively coupled plasma-mass spectrometry

Single cell-inductively coupled plasma-mass spectrometry (SC-ICP-MS) is an emerging technology. In this work, we have developed a novel SC-ICP-MS method to quantify metal ions in individual cells of a toxic cyanobacterial species, Microcystis aeruginosa (M. aeruginosa), without complicated post-dosing sample preparation, and applied this method to study the treatment effectiveness of copper-based algaecides (cupric sulfate and EarthTec®) on the toxic algae M. aeruginosa. The developed SC-ICP-MS method uses new intrinsic metal element magnesium to determine real transport efficiency and cell concentration. The cell viability and microcystin-LR release by algaecide treatment were studied by flow cytometry and ultra-fast liquid chromatography-tandem mass spectrometry, respectively. The results showed that this novel method was very rapid, highly sensitive (detection limits of intracellular copper and magnesium were 65 ag/cell and 98 ag/cell, respectively), and reproducible (relative standard deviation within 12%). The algaecide effectiveness study further demonstrated that copper in the forms of cupric sulfate and copper-based algaecide EarthTec® successfully diminished M. aeruginosa populations. The higher the copper concentration used to treat the cells, the faster the speeds of copper uptake and cell lysis in the copper concentrations ranged from 0 to 200 μg/L of copper-based algaecide. The cells exhibit obvious heterogeneity in copper uptake. The result suggests that M. aeruginosa cells uptake and cumulate copper followed by cellular lysis and microcystin-LR release. These novel results indicated that though the copper-based algaecides could control this type of harmful algal bloom, further treatment to remove the released algal toxin from the treated water would be needed.

Recent advances in single-cell analysis by mass spectrometry

Cells are the most basic structural units that play vital roles in the functioning of living organisms. Analysis of the chemical composition and content of a single cell plays a vital role in ensuring precise investigations of cellular metabolism, and is a crucial aspect of lipidomic and proteomic studies. In addition, structural knowledge provides a better understanding of cell behavior as well as the cellular and subcellular mechanisms. However, single-cell analysis can be very challenging due to the very small size of each cell as well as the large variety and extremely low concentrations of substances found in individual cells. On account of its high sensitivity and selectivity, mass spectrometry holds great promise as an effective technique for single-cell analysis. Numerous mass spectrometric techniques have been developed to elucidate the molecular profiles at the cellular level, including electrospray ionization mass spectrometry (ESI-MS), secondary ion mass spectrometry (SIMS), laser-based mass spectrometry and inductively coupled plasma mass spectrometry (ICP-MS). In this review, the recent advances in single-cell analysis by mass spectrometry are summarized. The strategies of different ionization modes to achieve single-cell analysis are classified and discussed in detail.

New Frontiers of Metallomics: Elemental and Species-Specific Analysis and Imaging of Single Cells

Single cells represent the basic building units of life, and thus their study is one the most important areas of research. However, classical analysis of biological cells eludes the investigation of cell-to-cell differences to obtain information about the intracellular distribution since it only provides information by averaging over a huge number of cells. For this reason, chemical analysis of single cells is an expanding area of research nowadays. In this context, metallomics research is going down to the single-cell level, where high-resolution high-sensitive analytical techniques are required. In this chapter, we present the latest developments and applications in the fields of single-cell inductively coupled plasma mass spectrometry (SC-ICP-MS), mass cytometry, laser ablation (LA)-ICP-MS, nanoscale secondary ion mass spectrometry (nanoSIMS), and synchrotron X-ray fluorescence microscopy (SXRF) for single-cell analysis. Moreover, the capabilities and limitations of the current analytical techniques to unravel single-cell metabolomics as well as future perspectives in this field will be discussed.

Quantitative Evaluation of Cisplatin Uptake in Sensitive and Resistant Individual Cells by Single-Cell ICP-MS (SC-ICP-MS)

One of the main limitations to the Pt-therapy in cancer is the development of associated drug resistance that can be associated with a significant reduction of the intracellular platinum concentration. Thus, intracellular Pt concentration could be considered as a biomarker of cisplatin resistance. In this work, an alternative method to address intracellular Pt concentration in individual cells is explored to permit the evaluation of different cell models and alternative therapies in a relatively fast way. For this aim, total Pt analysis in single cells has been implemented using a total consumption nebulizer coupled to inductively coupled plasma mass spectrometric detection (ICP-MS). The efficiency of the proposed device has been evaluated in combination with flow cytometry and turned out to be around 25% (cells entering the ICP-MS from the cells in suspension). Quantitative uptake studies of a nontoxic Tb-containing compound by individual cells were conducted and the results compared to those obtained by bulk analysis of the same cells. Both sets of data were statistically comparable. Thus, final application of the developed methodology to the comparative uptake of Pt-species in cisplatin resistant and sensitive cell lines (A2780cis and A2780) was conducted. The results obtained revealed the potential of this analytical strategy to differentiate between different cell lines of different sensitivity to the drug which might be of high medical interest.

Cytotoxicity of arsenic trioxide in single leukemia cells by time-resolved ICP-MS together with lanthanide tags

A novel strategy using cisplatin as a viability dye together with conjugating lanthanide tags to marker proteins was developed to examine As₂O₃cytotoxicity in single leukemia cells by ICP-MS.

Time-resolved ICP-MS analysis of mineral element contents and distribution patterns in single cells

Novel single cell techniques are attracting growing interest for clinical applications, because they can elucidate the cellular diversity and heterogeneity instead of the average masked by bulk measurements. Herein, time-resolved ICP-MS for the determination of essential mineral elements in single cells has been developed and is used to analyze the contents and distribution patterns of Fe, Cu, Zn, Mn, P and S in two types of cancer cells (HeLa and A549) and one type of normal cells (16HBE). The results show that there are obvious differences in contents and distribution patterns of the elements among the three types of cells. The mass of Fe, Zn, Cu, Mn, P, and S in individual HeLa cells is significantly higher and span a broader range of values than in the single 16HBE and A549 cells. The contents of Fe, Zn, and Cu follow log-normal distributions, and Mn, P, and S follow Poisson distributions with high λ values in single HeLa cells, indicating a large cell-to-cell variance. Comparatively, the contents of Cu, Zn, P, and S in 16HBE cells show the narrowest distribution range among the three tested cells, demonstrating the homogenous distribution of the elements in the cells. The method of single cell ICP-MS (SC-ICP-MS) provides potential applications for the monitoring of the variation of mineral elements at a single cell level.

Time-resolved ICP-MS measurement: a new method for elemental and multiparametric analysis of single cells

Time-resolved inductively coupled plasma mass spectrometry (ICP-MS) has attracted much attention for elemental and multiparametric analysis of single cells, instead of a classical bulk analysis of large amount of cells after a dissolution. In the time-resolved measurement, cells are directly introduced into the plasma via nebulizing or micro drop dispensing, and then ion plumes corresponding to single cells are individually detected with a high time resolution. The sensitivity and cell throughput in the measurement strongly depend on the time resolution. A high cell introduction efficiency into the plasma supports for a reduction of cell consumption. Biomolecules can also be measured through the attachment of elemental tags, and then the amount distribution of elements and biomolecules in single cells can be evaluated, while providing information concerning cell-to-cell variations. By applying ICP time-of-flight mass spectrometry (ICP-TOFMS), multiparametric analysis of elements and biomolecules can be achieved similar to that by a flow cytometer. This article highlights the technical aspects of the time-resolved ICP-MS measurement technique for elemental and multiparametric analysis of single cells.

Trends in single-cell analysis by use of ICP-MS

The analysis of single cells is a growing research field in many disciplines such as toxicology, medical diagnosis, drug and cancer research or metallomics, and different methods based on microscopic, mass spectrometric, and spectroscopic techniques are under investigation. This review focuses on the most recent trends in which inductively coupled plasma mass spectrometry (ICP-MS) and ICP optical emission spectrometry (ICP-OES) are applied for single-cell analysis using metal atoms being intrinsically present in cells, taken up by cells (e.g., nanoparticles), or which are artificially bound to a cell. For the latter, especially element tagged antibodies are of high interest and are discussed in the review. The application of different sample introduction systems for liquid analysis (pneumatic nebulization, droplet generation) and elemental imaging by laser ablation ICP-MS (LA-ICP-MS) of single cells are highlighted. Because of the high complexity of biological systems and for a better understanding of processes and dynamics of biologically or medically relevant cells, the authors discuss the idea of "multimodal spectroscopies."

Determination of quantum dots in single cells by inductively coupled plasma mass spectrometry

In order to assess cytotoxicity of quantum dots (QDs), new reliable analytical techniques that can provide comparative information at a single-cell level are required. In this study, a single cell ICP-MS (SC-ICP-MS) method was established to determine intracellular QDs in single cells after exposure. Uptake kinetics of QDs into cells was studied using the established method. The results were compared and validated by flow cytometry and cell digestion methods. In contrast to other methods, SC-ICP-MS can directly detect QDs and their degradation products via elements, and thus is a promising complement to available methods for single cell analysis and is expected to be a critical tool in the future.

Advances in mass spectrometry for the identification of pathogens

Mass spectrometry (MS) has become an important technique to identify microbial biomarkers. The rapid and accurate MS identification of microorganisms without any extensive pretreatment of samples is now possible. This review summarizes MS methods that are currently utilized in microbial analyses. Affinity methods are effective to clean, enrich, and investigate microorganisms from complex matrices. Functionalized magnetic nanoparticles might concentrate traces of target microorganisms from sample solutions. Therefore, nanoparticle-based techniques have a favorable detection limit. MS coupled with various chromatographic techniques, such as liquid chromatography and capillary electrophoresis, reduces the complexity of microbial biomarkers and yields reliable results. The direct analysis of whole pathogenic microbial cells with matrix-assisted laser desorption/ionization MS without sample separation reveals specific biomarkers for taxonomy, and has the advantages of simplicity, rapidity, and high-throughput measurements. The MS detection of polymerase chain reaction (PCR)-amplified microbial nucleic acids provides an alternative to biomarker analysis. This review will conclude with some current applications of MS in the identification of pathogens.

Element-tagged immunoassay with ICP-MS detection: evaluation and comparison to conventional immunoassays

We have investigated the possibility of using element-tagged antibodies for protein detection and quantification in microplate format using Inductively Coupled Plasma Mass Spectrometry (ICP-MS), and compared the results to conventional immunoassays, such as Enzyme-Linked Immunosorbent Assay (ELISA) and Western blotting. The technique was further employed to detect low levels and measure DNA-binding activity of transcription factor p53 in leukemia cell lysates through its interaction with immobilized oligonucleotides and recognition by element-tagged antibodies. The advantages of ICP-MS detection for routine performance of immunoassays include increased sensitivity, wide dynamic range, minimal interference from complex matrices, and high throughput. Our approach advances the ICP-MS technology and demonstrates its applicability to proteomic studies through the use of antibodies directly labeled with polymer tags bearing multiple atoms of lanthanides. Development of this novel methodology will enable fast and quantitative identification of multiple analytes in a single well.

Environmental applications of single collector high resolution ICP-MS

The number of environmental applications of single collector high resolution ICP-MS (HR-ICP-MS) has increased rapidly in recent years. There are many factors that contribute to make HR-ICP-MS a very powerful tool in environmental analysis. They include the extremely low detection limits achievable, tremendously high sensitivity, the ability to separate ICP-MS signals of the analyte from spectral interferences, enabling the reliable determination of many trace elements, and the reasonable precision of isotope ratio measurements. These assets are improved even further using high efficiency sample introduction systems. Therefore, external factors such as the stability of laboratory blanks are frequently the limiting factor in HR-ICP-MS analysis rather than the detection power. This review aims to highlight the most recent applications of HR-ICP-MS in this sector, focusing on matrices and applications where the superior capabilities of the instrumental technique are most useful and often ultimately required.