Hyperspectral characterization of the MSTO-211H cell spheroid model: A FPA–FTIR imaging approach

Multicellular spheroids are the new frontier for studying how the tumour micro-environment interferes with drug uptake and response, since they can reproduce a three-dimensional cellular organisation mimicking the behaviour of in vivo solid tissues. In this study, we exploited Focal Plane Array - Fourier Transform Infrared Imaging spectroscopy to characterize the biochemical features, in terms of distribution and composition of the meaningful macromolecules (lipids, proteins, sugars and nucleic acids), of malignant pleural mesothelioma spheroid sections, and, as further extent, to investigate the penetrating effects of cisplatin within the spheroid mass. The hyperspectral imaging analysis evidenced, in untreated spheroids, the occurrence of a replicative outer region and a hypoxic inner one, as suggested by the band area ratios related to lipid alkyl chains (2925/2960) and glycogen (1020/1650), which showed the highest values in the inner region. Moreover, the HCA spectroscopic images showed, after cisplatin treatment, an increase of the band area ratio related to lipid carbonyl ester moiety (1740/2925), suggesting the occurrence of lipid peroxidation; furthermore, the band area ratio related to nucleic acids (1240/1220) revealed a DNA fragmentation along all regions of spheroids that may be related to apoptotic mechanisms, whereas a reduction of the band area ratios related to glycogen and carbohydrates (1020/1650 and 1054/1650, respectively) appeared consistent with an inhibition of cell division. The few spectral differences between the outer and the inner regions of cisplatin-treated spheroids pointed out the diffuse penetrating effect of the drug.