TY - JOUR
T1 - Multilabel Per-Pixel Quantitation in Mass Spectrometry Imaging
AU - Dewez, F.
AU - De Pauw, E.
AU - Heeren, R.M.A.
AU - Balluff, B.
N1 - Funding Information:
This research was financially supported in part through the LINK program of the Province of Limburg (The Netherlands). F.D. received support from the Joint Imaging Valley program of the University of Li?ge and the Maastricht University. F.D. and B.B. received financial support from the European Union (ERA-NET TRANSCAN 2; Grant No. 643638). We thank Professor Bouvy from Maastricht University, the Netherlands, for providing the pig tissue.
Funding Information:
This research was financially supported in part through the LINK program of the Province of Limburg (The Netherlands). F.D. received support from the Joint Imaging Valley program of the University of Liège and the Maastricht University. F.D. and B.B. received financial support from the European Union (ERA-NET TRANSCAN 2; Grant No. 643638). We thank Professor Bouvy from Maastricht University, the Netherlands, for providing the pig tissue.
Publisher Copyright:
© 2020 American Chemical Society
PY - 2021/1/26
Y1 - 2021/1/26
N2 - In quantitative mass spectrometry imaging (MSI), the gold standard adds a single structural homologue of the target compound at a known concentration to the sample. This internal standard enables to map the detected intensity of the target molecule against an external calibration curve. This approach, however, ignores local noise levels and disproportional ion suppression effects, which might depend on the concentration of the target compound. To overcome these issues, we propose a novel approach that applies several isotopically labeled versions, each at a different concentration, to the sample. This allows creating individual internal calibration curves for every MSI pixel. As proof of principle, we have quantified an endogenous peptide of histone H4 by matrix-assisted laser desorption/ionization-QMSI (MALDI-QMSI), using a mixture of three isotopically labeled versions. The usage of a fourth label allowed us to compare the gold standard to our multilabel approach. We observed substantial heterogeneity in ion suppression across the tissue, which disclosed itself as varying slopes in the per-pixel regression analyses. These slopes were histology-dependent and differed from each other by up to a factor of 4. The results were validated by liquid chromatography-mass spectrometry (LC-MS), exhibiting a high agreement between LC-MS and MALDI-Q : MSI (Pearson correlation r = 0.87). A comparison between the multilabel and single-label approaches revealed a higher accuracy for the multilabel method when the local target compound concentration differed too much from the concentration of the single label. In conclusion, we show that the multilabel approach provides superior quantitation compared to a single-label approach, in case the target compound is inhomogeneously distributed at a wide concentration range in the tissue.
AB - In quantitative mass spectrometry imaging (MSI), the gold standard adds a single structural homologue of the target compound at a known concentration to the sample. This internal standard enables to map the detected intensity of the target molecule against an external calibration curve. This approach, however, ignores local noise levels and disproportional ion suppression effects, which might depend on the concentration of the target compound. To overcome these issues, we propose a novel approach that applies several isotopically labeled versions, each at a different concentration, to the sample. This allows creating individual internal calibration curves for every MSI pixel. As proof of principle, we have quantified an endogenous peptide of histone H4 by matrix-assisted laser desorption/ionization-QMSI (MALDI-QMSI), using a mixture of three isotopically labeled versions. The usage of a fourth label allowed us to compare the gold standard to our multilabel approach. We observed substantial heterogeneity in ion suppression across the tissue, which disclosed itself as varying slopes in the per-pixel regression analyses. These slopes were histology-dependent and differed from each other by up to a factor of 4. The results were validated by liquid chromatography-mass spectrometry (LC-MS), exhibiting a high agreement between LC-MS and MALDI-Q : MSI (Pearson correlation r = 0.87). A comparison between the multilabel and single-label approaches revealed a higher accuracy for the multilabel method when the local target compound concentration differed too much from the concentration of the single label. In conclusion, we show that the multilabel approach provides superior quantitation compared to a single-label approach, in case the target compound is inhomogeneously distributed at a wide concentration range in the tissue.
U2 - 10.1021/acs.analchem.0c03186
DO - 10.1021/acs.analchem.0c03186
M3 - Article
C2 - 33373197
SN - 0003-2700
VL - 93
SP - 1393
EP - 1400
JO - Analytical Chemistry
JF - Analytical Chemistry
IS - 3
ER -