Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was utilized for spatially resolved bioimaging of the distribution of silver and gold nanoparticles in individual fibroblast cells upon different incubation experiments. High spatial resolution was achieved by optimization of scan speed, ablation frequency, and laser energy. Nanoparticles are visualized with respect to cellular substructures and are found to accumulate in the perinuclear region with increasing incubation time. On the basis of matrix-matched calibration, we developed a method for quantification of the number of metal nanoparticles at the single-cell level. The results provide insight into nanoparticle/cell interactions and have implications for the development of analytical methods in tissue diagnostics and therapeutics.

A method for phosphopeptide identification by capillary liquid chromatography (muLC) interfaced alternatively to element mass spectrometry (inductively coupled plasma mass spectrometry, ICPMS) and to electrospray ionization mass spectrometry (ESI-MS) is described. ICPMS is used for 31P detection and ESI-MS provides the corresponding molecular weight information. Alignment of the two separate muLC runs is performed using the baseline distortion at the elution front, which shows up in both muLC-ICPMS and muLC-ESI-MS. Both a quadrupole and a magnetic sector field mass analyzer were used in combination with ICP. The detection limit achieved for the muLC-ICP-HRMS runs is approximately 0.1 pmol of phosphopeptide injected. Without any further precautions, contamination by phosphate-containing compounds at this level was found to be uncritical. The method is demonstrated for the analysis of a complex mixture of synthetic phosphopeptides and a set of tryptic digests of three phosphoproteins. These include beta-casein, activated human MAP kinase ERK1, and protein kinase A catalytic subunit. The tryptic phosphopeptides of these proteins could all be detected and identified by our new strategy. Analysis of three fractions of protein kinase A catalytic subunit with different phosphorylation status gives direct access to the order in which the phosphorylation of the four phosphorylation sites occurs. The two most important aspects of using muLC-ICPMS with 31P detection for phosphopeptide identification are (i) that a high selectivity is achieved and (ii) that the signal intensity is independent of the chemical form of phosphorus and directly proportional to the molar amount of 31P in the muLC eluate. Thus, muLC-ICPMS with 31P detection is introduced as a new, robust, and specific method in phosphoproteomics.

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The application of mass spectrometry with soft ionization techniques (ESI, electrospray ionization, and MALDI, matrix-assisted laser desorption ionization) in the life sciences for the detection and identification of biomolecules is already well established, whereas the application of elemental mass spectrometry and in particular inductively coupled plasma mass spectrometry (ICP-MS) for the determination of metals, metalloids and non-metals in biomolecules is rather new and there is some hesitation in accepting this analytical method, although it offers many advantages. Therefore, it is the aim of this tutorial review to highlight new analytical strategies consisting of the combined applications of elemental and molecular mass spectrometric techniques. In fact, elemental and biomolecular mass spectrometric methods are highly complementary: elemental mass spectrometry methods, such as ICP-MS, offer very sensitive element analysis in the trace and ultra-trace concentration range with multielement capability and the excellent and uniform sensitivity is structure-independent and can be used analytically for accurate quantification as well as for fast screening of specific elements even in complex samples. Laser ablation (LA) ICP-MS, as a solid state mass spectrometric technique, allows the direct determination of trace elements in biological and environmental samples and is applied for microlocal analysis with spatial resolution in the mum range. In contrast, molecular weight determination and structural information is completely lost during the ionization step so that these features have to be provided by biomolecular mass spectrometry and in particular by ESI- and MALDI-MS. On the basis of selected examples, it will be shown that only the combination of different elemental and biomolecular mass spectrometric techniques can solve analytical problems in the life sciences and environmental research in a synergistic way where neither technique alone would be successful. This synergy will be demonstrated by selected applications from various areas: food and nutrition, toxicology, clinical and pharmaceutical research, biochemistry and in particular proteomics. Future developments and trends will be discussed concerning instrumental developments of new mass spectrometric techniques providing high sensitivity with lower detection limits for many elements measured quasi-simultaneously so that new analytical information about biological systems can be drawn from isotopic information and the application of stable non-radioactive isotopic tracers. In addition, elemental labels enable the development of new high-throughput screening techniques based on multiplexed biomarkers. Advanced powerful surface mass spectrometric techniques are required for the imaging of elemental and molecular information in order to analyse tissue samples and to develop novel array-based biochips.

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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."

Laser ablation inductively coupled plasma-mass spectrometry (ICP-MS) with (31)P detection has been used for spotting of phosphoproteins after one-dimensional polyacrylamide gel electrophoresis (1-D PAGE) and membrane transfer. By analyzing a mixture of myoglobin, alpha-casein and reduced fibrinogen it is demonstrated that phosphoproteins are specifically recognized by this method. A special washing step was found to be necessary to remove phosphate noncovalently bound to proteins. The (31)P signal was found to contain quantitative information both with respect to relative and absolute amounts of phosphorus present in phosphoproteins. Normalizing the (31)P signal from a single laser ablation trace by the total amount of phosphoprotein applied to the gel, a detection limit of 5 pmol of phosphorus is estimated.