The viscoelastic material properties of biological systems are increasingly recognized as important parts of signaling cascades involved in developmental and pathological processes. They are furthermore assumed to play a crucial role in surviving extreme environmental conditions for certain organisms, such as yeast cells. Confocal Brillouin microscopy gives access to the viscoelastic material properties of single cells and tissues in a contact- and label-free manner and with a high spatial resolution. In combination with quantitative phase imaging, it is then possible to determine the longitudinal modulus and the viscosity of the sample. In this study, we probed living zebrafish larvae in all anatomical planes, at different time points during development and after spinal cord injury. We could show, that confocal Brillouin microscopy detects the viscoelasticity of different anatomical structures without affecting the animal’s development. We furthermore observed a transiently decreasing Brillouin shift after spinal cord injury and a difference in Brillouin shift between in vivo and ex vivo measurements of the same sample region. Using quantitative phase imaging we additionally show, that the Brillouin shift of the probed tissues is mainly governed by their longitudinal modulus and viscosity. In conclusion, this work constitutes the methodical basis to identify key determinants of viscoelastic tissue properties during biologically important processes in vivo.
KEYWORDS: Spinal cord, Tissues, Signal processing, Scattering, In vivo imaging, Atomic force microscope, Spatial resolution, Magnetic resonance elastography, Biomedical optics, Phased array optics
The mechanical properties of biological tissues are increasingly recognized as crucial parts of signaling cascades involved in developmental and pathological processes. Most existing mechanical measurement techniques require either highly invasive sample preparations and destruction of the tissue for access, such as atomic force microscope, or provide insufficient spatial resolution, such as sonoelastography and magnetic resonance elastography. The optical elastography is an emerging field in biomedicine, which allows to capture an image of the elasticity module with subcellular resolution. We present as a promising method a quantitative micro-elastography based on Brillouin scattering, which is the inelastic scattering of photons by acoustic phonons with gigahertz frequency. Using a virtually imaged phased array (VIPA) based spectrometer and a confocal microscope a label-free, three-dimensional, non-intrusive micro-elastography with the absence of extrinsic mechanical loading is provided. In this paper, we present a systematic application of Brillouin micro-elastography to quantify physical properties of native larval zebrafish tissues in vivo. We detected a transiently decreasing Brillouin frequency shift after spinal cord injury. The presented work constitutes the first step towards an in vivo assessment of spinal cord tissue mechanics during regeneration, provides a basis to identify key determinants of mechanical tissue properties and allows to test their importance in combination with biochemical and genetic factors.
The mechanical properties of biological tissues are increasingly recognized as crucial parts of signaling cascades involved in developmental and pathological processes. While most techniques measuring intrinsic mechanical properties necessitate invasive sample preparations or are currently applicable only to large sample dimensions, confocal Brillouin microscopy provides means to quantify the mechanical properties of single cells and tissues in a contact- and label-free manner. Here, we show for the first time a systematic application of confocal Brillouin microscopy to quantify physical properties of tissues in vivo. By using our custom-built Brillouin microscope, zebrafish larvae were probed in all anatomical planes, at different time points during development and after spinal cord injury. These experiments revealed that confocal Brillouin microscopy is capable of detecting the mechanical properties of distinct anatomical structures without interfering with the animal’s natural development. We furthermore detected an increasing Brillouin shift of spinal cord tissue during development and a transiently decreasing Brillouin shift after spinal cord injury. The presented work constitutes the first step towards an in vivo assessment of spinal cord tissue mechanics during regeneration, provides a basis to identify key determinants of mechanical tissue properties and allows to test their importance in combination with biochemical and genetic factors.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.