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Working Group Raman and Infrared Histopathology

Based on Raman and infrared spectroscopy and in combination with powerful chemometrics, applications are developed to characterize cells and tissues with

  • lateral resolution down to the optical diffraction limit,
  • highest spectral resolution,
  • highest sensitivity,
  • for maximum sample throughput.

For this purpose, spectrometer systems are coupled with microscopes, fiber-optic probes or microfluidic chips. In addition, nanoparticles are used for signal enhancement, and imaging methods are applied. The results are validated with the clinical gold standard.

Important research and development activities since 2008 have included to establish an innovative single cell diagnosis and to translate the principles into clinical systems. A central application field is to identify tumor cells circulating in body fluids of cancer patients. Since these cells are rare, cultured cells were initially investigated as model systems. Strategies aim to enrich the tumor cells in the first step and / or to preselect them, so that in the second step, the tumor cells can be enumerated by means of Raman spectroscopy in the shortest possible time.

These methods are transferred to the study of diatoms. Characteristic biomolecules of these samples are chromophores of carotenoid and chlorophyll families, which are involved in photosynthesis and whose contributions in the Raman spectra are enhanced by resonance effects. Here, the complementarity of infrared spectroscopy is particularly evident, since the IR spectra are dominated by bands of biosilica, proteins and lipids.

Raman and infrared spectroscopy not only provide a marker-free specific signature, a so-called spectral fingerprint, of cells, but also of tissue composed of different cells. Starting points are studies by Raman and infrared imaging of tissue sections, which are correlated with the histopathological findings. The results are then transferred to measurements of biopsies ex vivo and to in vivo approaches. The goal is a minimally invasive and non-destructive evaluation of tissue in real time in order to distinguish normal from pathological tissue. As current fiber probes are designed for point measurements, Raman spectroscopy is combined with other optical imaging modalities. Applications have been addressed in the areas of brain tumors, atherosclerotic plaques in blood vessels, mineralization of teeth, inflammatory bowel diseases, and liver after sepsis in animal models.

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