Gas Cluster Ion Beam Time-of-Flight Secondary Ion Mass Spectrometry High-Resolution Imaging of Cardiolipin Speciation in the Brain: Identification of Molecular Losses after Traumatic Injury

Abstract

Gas cluster ion beam-secondary ion mass spectrometry (GCIB-SIMS) has shown the full potential of mapping intact lipids in biological systems with better than 10 μm lateral resolution. This study investigated further the capability of GCIB-SIMS in imaging high-mass signals from intact cardiolipin (CL) and gangliosides in normal brain and the effect of a controlled cortical impact model (CCI) of traumatic brain injury (TBI) on their distribution. A combination of enzymatic and chemical treatments was employed to suppress the signals from the most abundant phospholipids (phosphatidylcholine (PC) and phosphatidylethanolamine (PE)) and enhance the signals from the low-abundance CLs and gangliosides to allow their GCIB-SIMS detection at 8 and 16 μm spatial resolution. Brain CLs have not been observed previously using other contemporary imaging mass spectrometry techniques at better than 50 μm spatial resolution. High-resolution images of naive and injured brain tissue facilitated the comparison of CL species across three multicell layers in the CA1, CA3, and DG regions of the hippocampus. GCIB-SIMS also reliably mapped losses of oxidizable polyunsaturated CL species (but not the oxidation-resistant saturated and monounsaturated gangliosides) to regions including the CA1 and CA3 of the hippocampus after CCI. This work extends the detection range for SIMS measurements of intact lipids to above m/z 2000, bridging the mass range gap compared with MALDI. Further advances in high-resolution SIMS of CLs, with the potential for single cell or supra-cellular imaging, will be essential for the understanding of CL’s functional and structural organization in normal and injured brain.

SIMS imaging in neurobiology and cell biology

“…These regions are known to be involved in memory formation, seizure, and neurodegeneration. 54 This indicated that there might be a relationship between CLs and cognition.…”

“…To investigate the effect of traumatic brain injury on the molecular structure of the brain, Tian et al 54 developed a dynamic reactive ionization method for ToF-SIMS with a 20 keV (CO 2 ) 3500 + GCIB via treatment of the brain tissue with 1ethyl-3-[(dimethylamino) propyl] carbodiimide hydrochloride and phospholipase C (EDC/PLC). The EDC/PLC sample treatment was shown to suppress the signal of highly abundant phospholipids, especially PCs, and enhance the signal of high mass cardiolipin (CL) (m/z 1300-1530) and gangliosides (GM1, GD1, and GT1) (m/z > 1500) in the brain.…”

Extracellular ATP Regulates the Vesicular Pore Opening in Chromaffin Cells and Increases the Fraction Released During Individual Exocytosis Events

“…Some examples of this application include the localisation of dietary substrates in the brain or lipid changes in the brain after traumatic injury. 218,219 Studies of cells have also been done with IMS. As with tissue, lipid changes have been observed in both neuronal cell cultures and PC12 cells.…”

Mass Spectrometry Imaging: A Review of Emerging Advancements and Future Insights

“…216 Lipids also have the potential to show tumor boundaries, specifically in breast cancer. 217 Because of their diverse structure, several common ionization sources, including MALDI, 1,20,42,97 DESI, 22,217,218 SIMS, 219–221 and IR-MALDESI, 18,19 have found success in lipid imaging. Notably, newly developed laser spray ionization (LSI), with its simple sample preparation, is becoming more commonly used for lipids as well.…”