Differential mobility analysis-mass spectrometry coupled to XCMS algorithm as a novel analytical platform for metabolic profiling

Abstract

The development of additional analytical instruments is of great interest to expand metabolome coverage. Differential mobility analyzers (DMAs) are a type of ion mobility spectrometers that can be straightforwardly interfaced with commercial mass spectrometers. In this pilot study, we explored the capabilities of an ion mobility-mass spectrometry platform, based on interfacing a Differential Mobility Analyzer with a commercial quadrupole time of-flight mass spectrometer (DMA-QTOF), to phenotype the metabolic urinary fingerprint of a cohort of prostate cancer patients (n = 8) and a group of healthy counterparts (n = 20). The resolving power of the DMA and the QTOF was ∼55 and ∼6,500, respectively. The transmission efficiency of the DMA was 50%. We illustrate the benefits of incorporating the DMA through the separation of isobaric species according to their electrical mobility, which were not fully resolved by the high resolution QTOF. In addition, we show that the bidimensional electrical mobility-mass spectra obtained can be successfully processed with the XCMS routine, extending its potential to ion mobility-mass spectrometry-based platforms. Data mining with XCMS revealed seven features significantly down-regulated in cancer patients (P < 0.05). These peaks were the input of principal component analysis, showing a clear separation tendency from prostate cancer patients and healthy controls. NIST MS search algorithm was used to classify the samples according to their class, with a resulting 75% sensitivity and 80% specificity. We pursued further fragmentation experiments for structural elucidation of the most discriminant metabolites, thereby illustrating the full potential of this analytical platform for the task. In summary, DMA-MS/MS provides an additional level of separation as compared to traditional mass spectrometry-based methods, thereby increasing the array of multi-analytical platforms available to global metabolite profiling and metabolite identification.