MSACL 2019 EU Abstract

Laser Desorption Imaging – Rapid Evaporative Ionisation Mass Spectrometry Platform for Tissue Imaging

Daniel Simon (1,2), Julia Abda (1), Hanifa J.A. Koguna (1,2), Stefania M. Stravrakaki (1), Julia Balog (1,3), Tamas Karancsi (3), Josephine Bunch (1,2), Zoltan Takats (1)
(1)Imperial College London, London, United Kingdom (2)National Physical Laboratory, London, United Kingdom (3)Waters Research Center, Budapest, Hungary

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Daniel Simon (Presenter) Imperial College London

Presenter Bio: Academic experience:

2019 - PhD Imperial College London, London, United Kingdom, Department of Surgery and Cancer
- Fundamental research and instrumentation on REIMS technology

2014 - 2017 MSc in Pharmaceutical Engineering, Budapest University of Technology and Economics, Budapest, Hungary

2010 - 2014 BSc in Molecular Biotics engineering, Pazmany Peter Catholic University, Budapest, Hungary

Other Experience:
2013 - 2019 Intern/Research Scientist at Medimass/Waters Research Center (renamed after acquisition by Waters in 2014)

Relevant Financial Disclosures (within past 24 months) No relevant financial relationship(s) to disclose. Discussing Products? NO, presenter will NOT present educational content related to products/services of the ineligible company(ies) listed above. Conflict mitigation NOT REQUIRED.

INTRODUCTION: Mass Spectrometry Imaging (MSI) is an emerging technique in the field of histopathology which enables the capturing of molecular information of clinically important tissue samples, thus allowing the histological characterisation of tissues. Several techniques are currently available, for example Matrix Assisted Laser Desorption Ionisation, Secondary Ion Mass Spectrometry or Desorption Electrospray Ionisation, however all these techniques have some technical challenges (extensive sample preparation, sampling in vacuum or high voltage requirements). In this presentation a new technique, Laser Desorption Imaging – Rapid Evaporative Ionisation Mass Spectrometry (LDI-REIMS) is described as a new MSI technique suitable for the rapid analysis of a wide range of samples without any sample preparation and under ambient conditions.
METHODS: A Xevo G2-S QToF (Waters, Wilmslow UK) Mass Spectrometer equipped with a REIMS source was used for the experiments. A home built motorised 2D XY stage coupled with laser optics was used as a sampling platform for all imaging experiments. An Intelliguide CO2 laser (Omniguide, Lexington, USA) at 10600 nm, a Medley MF3003 Er:YAG laser (2940 nm) and an Opolette HE2731 OPO laser (Opotek, Carlsbad, USA) tunable between 2700 – 3100 nm was used to map the Infrared laser parameter space for the experiments. 12 µm fresh frozen and formalin fixed paraffin embedded (FFPE) pork liver, rat brain and cancerous human breast tissues (all obtained under ethical approval) were used as samples.
RESULTS: Initial experiment show that the molecular coverage of the LDI – REIMS is sufficiently large for proper analysis. A wide array of metabolites, small molecules, peptides and structure molecules (glycerophospholipids) were observed during initial experiments. Comparisons were made using different wavelengths and laser pulse width and found the optimal mobilisation wavelength to be at 2900 – 2950 nm, correlated with the absorption maximum of the water content of tissues. Pulse widths between msec and nsec range were tested, finding the shorter pulses to be better for mobilisation. The currently achievable imaging resolution of our system is 50 – 70 µm. The pulse width and resolution are under further optimisation/investigation.
Successful tissue imaging experiments were conducted on several different tissue types, for example human breast tumour, rat brain glioma and pork liver molecular images were successfully created. The molecular changes observed in the data correlate well with the histopathological status of different tissues. After optimisation of the system, FFPE tissue slides were successfully measured without any sample preparation or extensive washing steps. Combining this feature with the high automation ability of the LDI-REIMS could enable autonomous processing of huge FFPE tissue banks, gaining useful insight behind the molecular changes in cancer and other diseases.