Development of Brillouin Spectroscopy for Mechanotransduction Research

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Mechanobiology is a rapidly developing area of science with the potential to improve significantly our knowledge of how cells function at a tissue/organ level. A better understanding of how cells react to their local mechanical environment (extracellular matrix, fluid flow, etc.) will also lead to advanced biomedical applications such as improved biomaterials and cell therapy. For such new therapeutic strategies, it is necessary to provide cells with a confined environment (niche) that enhances and regulates their proliferation and differentiation. In this regard, biomaterial technology currently leads the way in trying to fulfil these requirements by artificially recreating native-like three-dimensional environments. However, understanding how, why, and in what environment these cells differentiate in a lineage-specific manner is essential for understanding regenerative biology and developing better tissue engineering and stem cell therapy approaches. We believe that this underlying biology (i.e., the cell's responses to local mechanical stimuli) has not yet been properly investigated, due to a lack of appropriate tools, and that this is likely to undermine current attempts to i) understand mechanobiology; and ii) recreate the stem cell niche using purposeful biomaterials. Therefore, we plan to understand the role substrate stiffness plays in maintaining/directing cell phenotype at an unprecedented level by developing a sophisticated microscope that can quantify mechanical properties of the cells and their immediate environment whilst simultaneously measuring the cells' response to this environment at a gene and protein level. Our novel approach uses only light, and thus requires no direct physical contact with the sample and can probe deep into tissue structures. Most importantly, it can be performed under physiological conditions on live cells, facilitating real-time measurements under dynamic conditions. Such experiments have not previously been possible.However, based on our recent success in building a confocal imaging system to measure tissue stiffness in 3D, we think this is now possible. Using the principle of Brillouin spectroscopy, the system detects light that has been scattered inelastically from acoustic phonons in the sample in a confocal optical arrangement to facilitate a non-contact, direct readout of the mechanical properties of tissues. We now wish to explore if this same confocal system can be used simultaneously to excite fluorescent molecules within the probed tissues. As such, our aims are to modify our existing machine so that confocal images of fluorescently-labelled proteins (from cells, tissues or tissue-engineered constructs) can be resolved and overlaid with simultaneous measurements of the mechanical properties of said cells/tissues. Ultimately, this will allow, for the first time and with unprecedented detail, the direct, real-time account of a cell's molecular response to differing local mechanical environments.