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2013|14 Annual Report Fraunhofer IGB

70 MEDICINE RAMAN-SPECTROSCOPY IN BIOMEDICAL ENGINEERING AND REGENERATIVE MEDICINE Eva Brauchle M.Sc., Prof. Dr. rer. nat. Katja Schenke-Layland M.Sc. Analysis of cell and tissue samples In biomedical engineering and regenerative medicine, the analysis of rare tissues and cells is often limited to a few bio- logical properties. Complicated processes make the analysis error-prone and time-consuming, typically altering sample characteristics and rendering the sample unusable for further studies. At the Fraunhofer IGB, we are investigating non-inva- sive technologies such as Raman spectroscopy for the global analysis of cell and tissue samples. Raman spectroscopy is an optical technology based on the effects of light scattering on a sample. Here, photons of incident monochromatic light in- teract with sample molecules, thereby shifting their frequency. The Raman spectrum represents the frequency shift of the inelastic light scattering. The spectral bands create a “finger- print”, which are specific to molecular bonds that can be iden- tified in complex samples, such as biological tissues [1, 2]. Due to its simple sample preparation, as well as the ability to gain biochemically relevant information under physiological condi- tions without the use of dyes, the method can be applied to a wide range of medical applications [2]. Non-contact cell culture quality control The proper characterization of primary cells from patients’ tis- sues is a critical step in regenerative medicine. Using Raman spectroscopy, the current state of an individual cell can be detected without contact. Apoptotic and necrotic cells have an altered Raman spectrum, which allows their identification within a population of viable cells. The molecular vibrational bands in the spectrum allow the identification of the early and late phases of apoptosis. Our studies show that the Raman spectroscopy is not only a valid method for the continuous monitoring of primary cell cultures, but is also suitable for cy- totoxic studies where the accurate detection of the cell death plays an important role. Analysis of in vitro differentiated stem cells Stem cells have great therapeutic potential because they can differentiate into diverse types of tissue-specific cells. Al- though immunohistological methods can identify the differen- tiation state of cells via marker proteins, they require the ma- nipulation of the cell culture. Stem cells and their derivatives have a molecular profile, which corresponds to their current cell phenotype. Raman spectroscopy can non-invasively moni- tor the differentiation process at the molecular level, providing a unique profile of different cell types that can arise from a stem cell. In molecular patterns of fibroblasts, keratinocytes and melanocytes, which all originate from skin, Raman bands were related to the biological functions of the respective cell type, exhibiting characteristic Raman signals [3]. In other stud- ies, Raman spectroscopy was able to identify the pathological loss of tissue-specific cell phenotypes in degenerating carti- lage [4]. Pathological changes in tissues In natural tissues, cells are in close contact with a complex network of fibrous and soluble components known as the extracellular matrix. The extracellular matrix is specific for each tissue, often consisting of collagen, elastin and proteoglycans, 1

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