Spontaneous and Stimulated Brillouin Scattering for Biomedicine

The mechanical properties of biological tissues are increasingly recognized as critical parts of signaling cascades involved in pathological processes. Conventional mechanical measurement techniques require either the destruction of the tissue for access, such as atomic force microscopy (AFM) or provide insufficient spatial resolution. Brillouin imaging overcomes these disadvantages. It is based on the interaction of optical and acoustic waves. The resulting Doppler frequency shift depends on the mechanical properties of the tissue. Brillouin imaging enables volumetric and contactless mapping of living cells and tissues. We compare measurement techniques that use spontaneous and stimulated Brillouin scattering. The latter is generated with a Q-switch laser, measured with FFT-based signal processing and can be used for flow cytometry. Spontaneous scattering is measured with a spectrometer based on a virtually imaged phase array (VIPA). The mechanical properties of native larvae zebrafish tissues were mapped in vivo for studies of spinal cord tissue mechanics during regeneration. We present perspectives of various Brillouin imaging in neuroscience and flow cytometry.