Current Trends in the Development of FTIR Imaging for the Quantitative Analysis of Biological Samples

Fourier transform infrared imaging instrumentation has come of age for the rapid acquisition of biosample IR images, and thus now allows developing analytical methods based upon the molecular information of samples contents. For the biomedicine field, Fourier transform infrared imaging should be able to play a role in the molecular characterization of cells and tissues where no other analytical method provides quantitative information. Now, a compromise may be obtained between an acceptable acquisition time of IR images, which should never exceed a few tens of minutes, and the necessary spatial resolution (down to the diffraction limit, although limited for biology), spectral resolution (2 to 8 cm−1 for biosample analyses), and signal-to-noise ratio level, to provide a diagnostic answer to clinicians during the surgery time. Here, we will discuss the potential of Fourier transform infrared imaging in face to major pathologies (myopathies, brain tumors, metabolic diseases) for which current imaging methods remain unable to provide sufficient information for a precise diagnosis. Quantitative molecular information may be extracted from infrared images of samples as soon as samples volume/thickness is controlled as well as absorption and absorptivity of the molecules to analyze may be isolated from other absorbing compounds. In this context, metabolic parameters appear as the main targets for providing critical information about the physiological status of a biosample due to their characteristic infrared spectra. As examples, it will be shown how to isolate and quantify glucose, lactic-acid, urea, etc. absorptions from complex biosample infrared images.