Brillouin Spectroscopy: A Probe Of Tissue Micromechanics

Many problems in mechanobiology necessitate the characterization of cells’ and tissues’ micromechanical properties. Brillouin spectroscopy (light scattering) has been proposed as a new optical elastography technique to meet this requirement. However, the information in the Brillouin spectrum remains a source of contention due to fundamental issues in understanding the role of water in biomechanics and in relating the Brillouin data to low-frequency macroscopic mechanical parameters.

Researchers investigate this question using gelatin as a model system in which the macroscopic physical properties can be manipulated to mimic all relevant biological states of matter, from liquid to gel to glassy. Brillouin spectroscopy, the researchers show, can reveal both the elastic and viscous properties of biopolymers, which are essential to the structure and function of biological tissues.

This result demonstrates that the Brillouin frequency shift in this system is sensitive to the presence of the polymer network and that the modulus of the network can be determined if the spectrometer has an adequate resolution.

The Brillouin frequency shift is so sensitive to the network’s elastic properties that it reveals the onset of a sol-gel transition caused by forming a percolative cluster containing a population of cross-linked collagen molecules. Researchers observed this phenomenon by investigating two different gel concentrations, 10 and 20%, as a function of temperature.

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