FTIR spectroscopy of single live cells in aqueous media by synchrotron IR microscopy using microfabricated sample holders

Infrared (IR) microspectroscopy is increasingly employed to reveal chemical information from biological systems beyond the tissue level at the single cell level. A significant limitation of this technique has been the relative difficulty with which it can be applied to living systems. Demountable liquid cells initially developed at Daresbury Laboratory (UK) and now in use at the Australian Synchrotron have been refined to improve the ease of use and light throughput in the mid-IR spectral region allowing single living cells to be studied in an aqueous environment by limiting the path length to 12 μm or less. For larger cells, such as microalgae, a modified commercial flow-though cell has been used, while for smaller cells, custom windows with lithographically patterned spacers were used in a commercial compression cell. Reducing the window thickness to 1.0 mm or 0.5 mm was also found to sufficiently reduce the wavelength dependent focus effects observed with high numerical aperture IR objectives.