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.

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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 mm to 65 mm 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 mg g À1 of Fe, 3 and 2 mg g À1 of Cu, 8 and 5 mg g À1 of Zn, 0.4 and 0.2 mg g À1 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 mg g À1, 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 mg g À1 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.

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