IR-live: plastic microfluidic devices for infrared spectro-microscopy of living cells

Infrared (IR) spectro-microscopy (FTIR) is a label-free chemical imaging technique which has been widely used as a diagnostic and research tool to obtain detailed molecular information in biological specimens. However, its application as an imaging technology to study living systems has been limited due to the strong absorbance of water in the mid-IR; even in a thin layer, water can completely overwhelm the chemical information from the sample. Microfluidic technology can provide a platform to overcome this limitation, with benefits in terms of measurement accuracy and integration of FTIR with other technics (e.g. flow cytometry).

The non-transparency to IR light of standard materials used in microfluidic, such as glass, plastics and PDMS, has so far limited the availability of practical set-up for the application of FTIR to live cells analysis. Here we present our approach for the easy and cheap fabrication of plastic microfluidic devices suitable for both optical and IR imaging. The plastic device is produced via standard soft-lithographic process; an embedded transparent view-port allows for imaging using both visible and IR photons, while the plastic body eases the connection with external pumping systems for the injection of the samples, handling of fluids and collection of waste. Chemical maps of REF52 cells seeded acquired while they were maintained inside the device show the potential application of FTIR for single-cell analysis.