A systematic study of high resolution multielemental quantitative bioimaging of animal tissue using LA-ICP-TOFMS

Abstract

Methodology for quantitative bioimaging of essential metals including Mg, Mn, Fe, Cu and Zn in tissue cryosections based on the use of high-resolution laser ablation coupled with inductively coupled plasma time-of-flight mass spectrometry (LA-ICP-TOFMS) has been systematically developed and characterized for the first time. Cryosectioned gelatin standards spiked with all the elements of interest were used for calibration. Analysis under ‘no gas’ conditions showed satisfactory selectivity and 3-fold improved limits of detection for Mn, Fe and Cu when compared with those when using 2.4 ml min⁻¹ H₂ in the collision/reaction cell of the ICP-TOFMS instrument. Absolute single-pixel limits of detection at 3 μm spatial resolution were in the range of 4–9 femtograms for Mn, Cu and Zn and approximately 40 femtograms for Mg and Fe. Gelatin standards spiked with acidified single-element solutions and with solutions prepared from metal salts were shown to have similar elemental homogeneity. The impact of variable thickness of cryosectioned gelatin on the signal intensity was studied and the linearity of response was established for thicknesses between 10 and 30 μm. The developed method was used for the quantification of essential metals in kidney sections of rats dosed with bis-choline tetrathiomolybdate (TTM) to regulate Cu levels in relation with Wilson's disease as well as in kidney sections of control animals. To achieve this, the developed methodology was extended to also include Mo and detailed distribution of Mo/Cu ratios at cellular to subcellular resolution was obtained, showing fine correlation between these elements in the medulla regions of the kidney.