State Key Laboratory of Environmental and Biological Analysis, Department of Chemistry, Hong Kong Baptist University, Hong Kong SAR, People's Republic of China.
School of Biomedical and Pharmaceutical Sciences, Guangdong University of Technology, Guangzhou 510006, People's Republic of China.
Anal Chem. 2020 Jun 2;92(11):7413-7418. doi: 10.1021/acs.analchem.9b05812. Epub 2020 May 19.
Increasing studies have utilized mass spectrometry imaging (MSI) that is a label-free tool to investigate drug penetration and drug biotransformation in multicellular tumor spheroids (MCTS). Currently, the gelatin-assisted sectioning method is widely used to prepare frozen sections of MCTS for MSI. However, owing to the limited transparency of frozen gelatin, MCTS with diameters less than 500 μm that closely mimic solid tumors are difficult to be detected when cryosectioning. In order to identify the presence of MCTS, hematoxylin and eosin staining for frozen sections and dye pretreatment for MCTS were employed in previous works, which either increased the analytical time and cost in sample preparation or caused signal suppression in sample analysis. Herein, a new sectioning method was developed to prepare MCTS frozen sections. MCTS was coated with ice to ensure good visibility for small-size MCTS. The optimal cutting temperature compound was added around the ice block to assist the formation of frozen sections. A precast frozen mold was prepared to allow the acquisition of complete MCTS frozen sections. The developed method was applied to investigate lipid distribution in MCTS by using matrix-assisted laser desorption/ionization MSI. Compared to the gelatin-assisted sectioning method, our method did not cause signal suppression and analyte delocalization. Thus, this method provides an easy, universal, and innovative strategy to prepare MCTS frozen sections for further MSI analysis. Besides, we applied our method to investigate the penetration of bisphenol A in MCTS.
越来越多的研究利用质谱成像（MSI），这是一种无标记的工具，来研究多细胞肿瘤球体（MCTS）中的药物渗透和药物生物转化。目前，明胶辅助切片法广泛用于制备 MCTS 的冷冻切片进行 MSI。然而，由于冷冻明胶的透明度有限，当对小于 500μm 的 MCTS 进行冷冻切片时，很难检测到这些与实体瘤非常相似的小尺寸 MCTS。为了识别 MCTS 的存在，以前的工作中使用了对冷冻切片进行苏木精和伊红染色以及对 MCTS 进行染料预处理，这些方法要么增加了样品制备的分析时间和成本，要么导致了样品分析中的信号抑制。在此，开发了一种新的切片方法来制备 MCTS 冷冻切片。MCTS 用冰覆盖，以确保小尺寸 MCTS 的良好可见度。在冰块周围添加最佳切割温度化合物以辅助形成冷冻切片。制备了预制的冷冻模具，以获得完整的 MCTS 冷冻切片。该方法用于通过基质辅助激光解吸/电离 MSI 研究 MCTS 中的脂质分布。与明胶辅助切片法相比，我们的方法不会引起信号抑制和分析物定位。因此，该方法为进一步的 MSI 分析提供了一种简单、通用和创新的制备 MCTS 冷冻切片的策略。此外，我们还应用我们的方法研究了双酚 A 在 MCTS 中的渗透。
