Fig. 9
Results of cell surface pH analyses using SERS. a–d Examples of SERS hyperspectral pH mapping on MKN28, HepG2, MKN28 30 min after the application of EIPA and HepG2 after fixation, respectively. Each point of the maps corresponds effectively to a spot of 700 nm diameter. The relative images of Raman intensity of Band C at 1068 cm−1 are also reported. Scale bars: 10 µm. e Box plot comparing the integrated intensities at 1068 cm−1 collected from micro-aggregations (n = 9 measurements), AuNP colloidal solutions (n = 9 measurements) and AuNP on cell membrane surface (n = 864 measurements). The whiskers represent maximum and minimum; the square dot shows the mean and the segment in the rectangle indicates the median. f Mean values of surface pH in the four investigated cases (error bars show the standard deviation from the mean of n = 3 independent experiments). g–h Examples of SERS spectra collected from the outer surface of the cells and representative of pH 6.9 and 5.4, respectively. The band A + B was barely observable in the exemplifying spectrum of h. Source data are provided as a Source Data file. Source data
