Development of a Mass Spectrometry Sampling Probe for Chemical Analysis in Surgical and Endoscopic Procedures

Abstract

A sampling probe based on ambient desorption ionization was designed for in-vivo chemical analysis by mass spectrometry in surgical and endoscopic procedures. Sampling ionization of analytes directly from tissue was achieved by sealing the sampling tip against the tissue surface without allowing leakage of the auxiliary gas used for desorption ionization. The desorbed charged species were transferred over a long distance (up to 4 m) through a flexible tube of internal diameter as small as 1/16 inch to the inlet of the mass spectrometer used for analysis. The conditions used for desorption electrospray ionization (DESI) were optimized to achieve biocompatibility for clinical applications while obtaining adequate efficiency for the analysis. This optimization involved removal of high voltage and use of pure water as spray solvent instead of the organic solvents or aqueous mixtures normally used. Improved sensitivity was achieved under these conditions by increasing the gas flow rate in the transfer tube. The destructive effect on tissue surfaces associated with typical desorption ionization was avoided by altering the local gas dynamics in the sample area without compromising the overall analysis efficiency.

Nondestructive tissue analysis for ex vivo and in vivo cancer diagnosis using a handheld mass spectrometry system

“…Intraoperative diagnosis and surgical margin evaluation continue to be research focuses of clinical ambient ionization MS, with efforts used to develop devices for in vivo diagnosis (18). For example, a sampling probe using a DESI-MSI source to produce a continuous high-pressure spray of microdroplets has been proposed for tissue analysis (38), but it has not been demonstrated for cancer diagnosis or in vivo use. Ultraviolet and infrared laser approaches have been reported for tissue analysis through ablation processes (23, 24).…”

Real-Time Sample Analysis Using a Sampling Probe and Miniature Mass Spectrometer

“…25 Some recent studies have shown the potential of using real-time MS analysis to provide rich molecular information on tissue to assist in surgical decision making. 5,35,36 The use of a miniature MS system, instead of a lab-scale mass spectrometer, would certainly make the implementation of real-time MS analysis much more convenient in surgical room.…”

“…Auxiliary pumping was used to pull the gas for ion transfer, which altered the gas dynamics of the sampling area and minimized the destruction to the tissue surface. 25 …”

Towards Practical Endoscopic Mass Spectrometry

“…One used a remote sampling desorption ESI of over 1 m. 31) Unlike the normal operation, the sampling tip of the remote DESI had to be pressed against the tissue sample to seal o the gap so as to direct the carrier gas and ions to the MS inlet. To meet the clinical requirement, the high voltage supply to the ESI source had to be removed, and the solvent needed to be replaced with pure water.…”