Bioimaging of metals in rat brain hippocampus by laser microdissection inductively coupled plasma mass spectrometry (LMD-ICP-MS) using high-efficiency laser ablation chambers

Bioimaging of elements and in biological tissues by mass spectrometry imaging (MSI) using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has been developed to investigate elemental distribution in biological tissues in metallomic studies. Spatial resolution of LA-ICP-MS imaging is routinely achieved at several tens of micrometers. To investigate small-sized tissues and single cells, the resolution of LA-ICP-MS can be improved down to low-micrometer and sub-micrometer by combining a laser microdissection (LMD) apparatus with a quadrupole-based inductively coupled plasma mass spectrometer. Mass spectrometry imaging of metals in sections of rat brain hippocampus by LMD-ICP-MS has shown 4 different layers with spatial resolution of 4 μm in our previous study. In order to improve the performance of LMD-ICP-MS imaging technique, new laser ablation chambers for the LMD configuration were constructed and characterized regarding efficient transport of laser generated aerosols and fast washout effects. The results showed that washout was the fastest in cylindrical cell with a small volume of ∼1 cm3. Using this laser ablation cell, ion images of 23Na+, 24Mg+, 31P+, 39K+, 56Fe+ and 64Zn+ were obtained in two regions in rat brain hippocampus by imaging LMD-ICP-MS. Scan speed in imaging LA-ICP-MS was found as an important parameter, which could affect the sensitivity and stability of ICP-MS ion signals. With optimized experimental arrangement and operating parameters, LMD-ICP-MS will soon open a window for in situ elemental imaging in native tissues to investigate local variations of metals/metalloids of biological relevance.

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► Small cylindrical laser ablation cell for novel mass spectrometric imaging technique LMD-ICP-MS was constructed and provided fast aerosol washout and efficient particle transport.
► Metal distributions in rat brain hippocampus were obtained by imaging LMD-ICP-MS with high spatial resolution using such laser ablation cell.
► Scan speed in LA-ICP-MS was found to be an important parameter that affected the sensitivity and stability of ICP-MS signals.