Fabrication of a microfluidic platform for investigating dynamic biochemical processes in living samples by FTIR microspectroscopy

Here we present the optimization of fabrication steps for realizing an infrared–visible microfluidic chip to study single-living cell behaviour in physiological environment by synchrotron radiation FTIR microspectroscopy. We optimized subtractive and additive lithographic processes on CaF2 substrate, employing X-ARP 3100/10 photoresist both as etching-mask and for the device fabrication. Using prototype microfabricated liquid cells 9 and 5 μm thick, we measured the response of small groups of THP1 monocytic cells to mechanical compression and chemical stimulation with fMLP using conventional IR globar source, aiming to evaluate biochemical rearrangements of leukocytes during the capillary circulation or recruitment processes. Stimulated monocytes have spectral features recognizable, differentiating them from un-stimulated, especially affecting the spectral region 1280–1000 cm−1, characteristic of nucleic acids and carbohydrates, and specific band ratios, such as proteins on lipids and methylene on methyl. Spectra variations have been correlated with biochemical events such as transcription, synthesis of new-proteins and variations in membrane fluidity.