Fig. 5. Polarity of the spheroids characterized by Raman spectroscopy.

a A representative bright-field image taken from a spheroid cultured in Matrigel, where the apical and basal membranes are indicated by blue and red arrows, respectively. Normalized Raman spectra acquired from spheroids cultured in Matrigel were plotted in b for the apical membrane (ApM) and in c for the basal membrane (BaM). d A representative bright-field image taken from a spheroid cultured by DEPMiC, where the apical and basal membranes are indicated by blue and red arrows, respectively. Normalized Raman spectra acquired from the spheroids cultured by DEPMiC were plotted in e for the apical membrane (ApM) and in f for the basal membrane (BaM). For the Raman spectra, the measured raw Raman signal and the fitted line are plotted in black and crimson, respectively. The seven Lorentzian fitting curves are shown in blue, where the two peaks at 2850 cm⁻¹ and 2885 cm⁻¹ are bolded. g The ratios (R) between the areas under the curve for the peaks at 2850 cm⁻¹ and 2885 cm⁻¹, i.e., R = A₂₈₈₅/A₂₈₅₀, were plotted for the apical membrane (ApM) and basal membrane (BaM) measured from spheroids cultured in Matrigel and by DEPMiC. Data are presented as the mean ± SD. Scale bars: 50 μm.