The use of synchrotron infrared microspectroscopy in biological and biomedical investigations

Synchrotron radiation is a bright source of infrared (IR) photons. It has been exploited in microscopy, where much smaller areas can be probed. with sizes close to the diffraction limit. The experiments have been performed at two beamlines, one at the National Synchrotron Light Source (USA) and one at SuperACO, LURE (France). The potentiality of this microanalytical synchrotron-based technique is particularly well documented in the study of individual cells: functional groups imaging representing biochemical changes have been obtained at various states of mitosis and apoptosis. The higher spatial resolution and spectral quality achieved allows investigating biological tissues in more detail. In this work, this is exemplified in the study of human hair and skin, where, in both cases, highly localized compounds have been evidenced in specific areas of the analyzed tissues: high lipid concentration inside the hair medulla, and inside the Stratum Corneum (SC) of skin. Moreover, the lineshape and frequency position of the CH2 stretching mode indicates a highly ordered phase extending over almost all the Stratum Comeum. The penetration pathway of an external agent has been also studied for both hair and skin. It is clear that synchrotron-based infrared microspectroscopy is an extremely valuable analytical tool when determining the spatially resolved chemical composition of biological and biomedical samples. In the future, the combination of infrared microspectroscopy with other synchrotron-based microscopic techniques, such as X-ray microscopy, at the same sample location is discussed. (C) 2003 Elsevier B.V. All rights reserved.