Bioimaging of metals and biomolecules in mouse heart by laser ablation inductively coupled plasma mass spectrometry and secondary ion mass spectrometry.

Bioimaging mass spectrometric techniques allow direct mapping of metal and biomolecule distributions with high spatial resolution in biological tissue. In this study laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) was used for imaging of transition metals (Fe, Cu, Zn, Mn, and Ti), alkali and alkaline-earth metals (Na, K, Mg, and Ca, respectively), and selected nonmetals (such as C, P, and S) in native cryosections of mouse heart. The metal and nonmetal images clearly illustrated the shape and the anatomy of the samples. Zinc and copper were inhomogeneously distributed with average concentrations of 26 and 11 µg g(-1), respectively. Titanium and manganese were detected at concentrations reaching 1 and 2 µg g(-1), respectively. The highest regional metal concentration of 360 µg g(-1)was observed for iron in blood present in the lumen of the aorta. Secondary ion mass spectrometry (SIMS) as an elemental and biomolecular mass spectrometric technique was employed for imaging of Na, K, and selected biomolecules (e.g., phosphocholine, choline, cholesterol) in adjacent sections. Here, two different bioimaging techniques, LA-ICPMS and SIMS, were combined for the first time, yielding novel information on both elemental and biomolecular distributions.

Mass spectrometry imaging (MSI) of metals in mouse spinal cord by laser ablation ICP-MS.

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has been developed as a powerful MS imaging (MSI) tool for the direct investigation of element distributions in biological tissues. Here, this technique was adapted for the analysis of native mouse spinal cord cryosections of 3.1 mm × 1.7 mm by implementing a new conventional ablation system (NWR-213) and improving the spatial resolution from 120 µm to 65 µm in routine mode. Element images of the spinal cord are provided for the first time and the metalloarchitecture was established using a multimodal atlas approach. Furthermore, the spatial distribution of Rb was mapped for the first time in biological tissue. Metal concentrations were quantified using matrix-matched laboratory standards and normalization of the respective ion intensities to the average (13)C ion intensity of standards and samples as a surrogate of slice thickness. The "butterfly" shape of the central spinal grey matter was visualized in positive contrast by the distributions of Fe, Mn, Cu and Zn and in negative contrast by C and P. Mg, Na, K, S and Rb showed a more homogenous distribution. The concentrations averaged throughout grey matter and white matter were 8 and 4 µg g(-1) of Fe, 3 and 2 µg g(-1) of Cu, 8 and 5 µg g(-1) of Zn, 0.4 and 0.2 µg g(-1) of Mn. The carbon concentration in white matter exceeded that of grey matter by a factor of 1.44. Zn and Cu at 9 and 4 µg g(-1), respectively, were particularly enriched in the laminae I and II, in line with the high synaptic and cellular density there. Surprisingly Zn but not Cu was enriched in the central channel. Rb occurred at 0.3 µg g(-1) with a distribution pattern congruent to that of K. The coefficients of variation were 6%, 5%, 8% and 10% for Fe, Cu, Zn and Mn, respectively, throughout three different animals measured on different days. These MSI analyses of healthy wild type spinal cords demonstrate the suitability of the established techniques for investigating diseased or transgenic states in future imaging studies.

Biomonitoring of essential and toxic metals in single hair using on-line solution-based calibration in laser ablation inductively coupled plasma mass spectrometry.

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has been established as a powerful and sensitive surface analytical technique for the determination of concentration and distribution of trace metals within biological systems at micrometer spatial resolution. LA-ICP-MS allows easy quantification procedures if suitable standard references materials (SRM) are available. In this work a new SRM-free approach of solution-based calibration method in LA-ICP-MS for element quantification in hair is described. A dual argon flow of the carrier gas and nebulizer gas is used. A dry aerosol produced by laser ablation (LA) of biological sample and a desolvated aerosol generated by pneumatic nebulization (PN) of standard solutions are carried by two different flows of argon as carrier or nebulizer gas, respectively and introduced separately in the injector tube of a special ICP torch, through two separated apertures. Both argon flows are mixed directly in the ICP torch. External calibration via defined standard solutions before analysis of single hair was employed as calibration strategy. A correction factor, calculated using hair with known analyte concentration (measured by ICP-MS), is applied to correct the different elemental sensitivities of ICP-MS and LA-ICP-MS. Calibration curves are obtained by plotting the ratio of analyte ion M(+)/(34)S(+) ion intensities measured using LA-ICP-MS in dependence of analyte concentration in calibration solutions. Matrix-matched on-line calibration in LA-ICP-MS is carried out by ablating of human hair strands (mounted on a sticky tape in the LA chamber) using a focused laser beam in parallel with conventional nebulization of calibration solutions. Calibrations curves of Li, Na, Mg, Al, K, V, Cr, Mn, Fe, Ni, Co, Cu, Zn, Sr, Mo, Ag, Cd, I, Hg, Pb, Tl, Bi and U are presented. The linear correlation coefficients (R) of calibration curves for analytes were typically between 0.97 and 0.999. The limits of detection (LODs) of Li, V, Mn, Ni, Co, Cu, Sr, Mo, Ag, Ba, Cd, I, Hg, Pb, Bi and U in a single hair strand were in the range of 0.001-0.90 µg g(-1), whereas those of Cr and Zn were 3.4 and 5.1 µg g(-1), respectively. The proposed quantification strategy using on-line solution-based calibration in LA-ICP-MS was applied for biomonitoring (the spatial resolved distribution analysis) of essential and toxic metals and iodine in human hair and mouse hair.