Figure 2.

General workflow of MALDI-MSI on MCTS. MCTSs are collected when they grow to a stable size. (For HCT 116 in culture for 6000 initial cells, it is about 1 mm in diameter at day 14–20. (16)) The harvested MCTSs are washed with PBS to remove the cell culture media and then are embedded in gelatin. The samples are stored in −80 °C and cryosectioned to 12-μm thick slices. The sections are thaw mounted onto ITO slides. A matrix nebulizer can be used to spray the matrix solution onto the slides homogeneously, and MALDI-MSI can be performed. ITO, indium–tin oxide; MCTS, multicellular tumor spheroid; MSI, MS imaging.