Infrared microspectroscopy of biochemical response of living cells in microfabricated devices

First experiments demonstrating the suitability of novel microfabricated fluidic devices for measuring living cells in physiological environment by synchrotron radiation (SR) Fourier Transform Infrared microspectroscopy (μ-FTIR) are presented. The devices were fabricated on CaF2 windows, using the photoresist XARP 3100/10 to define the liquid cell lay-out. Therefore, the sample holder is transparent to both visible and infrared light, robust, completely recyclable and with a precise spacing. Using prototype devices of thicknesses 9, 5 and 3 μm, we studied the response of the U937 monocytic cell line to mechanical compression. The temporal evolution of the FTIR spectra, characteristic for the status of living cells, was used to monitor the cellular system stability in time. Protein biosynthesis and lipid metabolism alterations upon deformation have been identified by monitoring specific cell band ratios such as amide I to amide II, amide I to lipids, methylene to methyl and asymmetric to symmetric stretching of phosphates. Taking advantage of the high brilliance of the synchrotron radiation, chemical maps of monocyte cells were collected, demonstrating the versatility of the device.