Rapid Evaporative Ionization Mass Spectrometry – real-time, in-situ diagnostics of cancer, inflammatory diseases and infections
Dr. Zoltan Takats
Department of Surgery and Cancer
Imperial College London
Friday, August 8, 2014
C2-361 (Reading Room)
Abstract: Development of ambient ionization mass spectrometry has opened new opportunities regarding the in-vivo analysis of biological tissues. While certain ambient MS methods (e.g. desorption electrospray ionization; DESI) allows the non-invasive interrogation of biological systems, the technique is not capable of the analysis of the bulk cellular composition of tissues. The more recently developed Rapid Evaporative Ionization Mass Spectrometry (REIMS) method overcomes this obstacle. REIMS technology employs radio frequency electric current for the Joule-heating and subsequent evaporation of biological material resulting also in the formation of tissue-originated molecular ions. The REIMS spectral data – similarly to that of DESI – features predominantly ions associated with the complex lipid constituents and low-to-medium polarity metabolites of the corresponding tissues. Since the composition of cellular lipidome shows excellent correlation with the histological classification of cells, REIMS technology is capable of the near real-time identification of biological tissues, even in surgical environment. The REIMS-based surgical tissue identification device (aka. iKnife) has been tested in human surgical environment for in-situ identification of malignant tissues and it was found to deliver 90-100 % correct tissue classification results on the timescale of 0.7-2.8 s.
REIMS technology can also be used for the mass spectrometric characterisation of arbitrary samples given they bear sufficient electric conductivity. For example, colonies of unicellular organisms including pathogenic bacteria can also be easily subjected to REIMS analysis, yielding taxonomically specific spectral fingerprints. In this sense, REIMS represents a competitive technology to MALDI-based bacterial identification method. A potential advantage of REIMS is its capability of in-situ analysis, especially in case of mucous membrane-associated infections. This potential has been exploited in case of endoscopic analysis, where the REIMS technology is utilized as an in-situ analysis tool for mucosal surfaces. The approach was tested in both upper and lower gastrointestinal endoscopy applications and promising preliminary results were obtained for both in-situ cancer diagnostics and analysis of mucosal microbiome.