Figure 4

DESI-MS solvent spray has little impact on the suitability of post DESI-MS stained tissue slices for pathologic assessments. Two consecutive 10 μm slices of breast cancer tissue were obtained. The section to the left (section 1) was imaged with DESI-MS using a 1:1 mixture of acetonitrile:dimethylformamide (ACN:DMF) for lipid profiling in the negative ion mode. In contrast, the section to the right (section 2) was not exposed to DESI-MS solvent spray. (A) H&E images of the slices used in this assessment. (B) Zoomed in views of staining results. Necrotic regions appear in the red boxes, and viable regions appear in the green boxes. DESI-MS solvent treatment resulted in aberrant eosin staining of the viable cancer cells. (C) Training ROIs from section 2 (not scanned with DESI-MS) were used to perform automated segmentation of section 1 (which had come in contact with DESI-MS solvent spray prior to staining) with false colouring of the necrosis area (red), viable cancer area (green) and healthy tissue muscle (blue). The results of the morphometric analysis reveal that the relative surface area, and thus the gross morphology, of the viable cancer site (green) remain unchanged between DESI-MS imaged slice and the control.