Use of synchrotron-radiation-based FTIR imaging for characterizing changes in cell contents

FTIR imaging of individual cells is still limited by the low signal-to-noise ratio obtained from analysis of such weakly absorbing organic matter when using a Globar IR source. In this study, we used FTIR imaging with a synchrotron radiation source and a focal plane array detector to determine changes in the cellular contents of cryofixed cells after culture for 48 h on Si3N4 substrate. Several spectral differences were observed for cells deprived of glucose compared with control cells: a lower amide I-to-amide II ratio (P < 0.01); a different secondary structure profile of proteins (obtained from amide I spectral region curve fitting), with a significant increase in non-ordered structure components (P < 0.01); and a higher nu(C = C-H)/nu (as)(CH3) absorption ratio (P < 0.01), suggesting increased unsaturation of fatty acyl chains. Therefore, our study has shown that FTIR imaging with a synchrotron radiation source enables determination of several spectral changes of individual cells between two experimental conditions, which thus opens the way to cell biology studies with this vibrational spectroscopy technique.