Infrared and Raman imaging of biological and biomimetic samples

Established methods for imaging of biological or biomimetic samples, such a s fluorescence and optical microscopy, magnetic resonance imaging (MRI), X- ray tomography or positron emission tomography (PET) are currently compleme nted by infrared (both near-IR and mid-IR) as well as Raman spectroscopic i maging, whether it be on a microscopic or macroscopic scale. These vibratio nal spectroscopic techniques provide a wealth of information without a prio ri knowledge of either the spectral data or the composition of the sample. Infrared radiation does not harm the organism, no electric potential needs to be applied, and the measurements are not influenced by electromagnetic f ields, in addition, no extrinsic labeling or staining, which may perturb th e system under investigation, has to be added. The immense volume of inform ation contained in spectroscopic images requires multivariate analysis meth odologies in order to effectively mine the chemical and spatial information contained within the data as well as to analyze a time-series of images in order to reveal the origin of a chemical or biochemical process. The promi se and limitations of this new analytical tool are surveyed in this review.