Abstract
Brillouin spectroscopy is an emerging technique in the biomedical field. It probes the mechanical properties of a sample through the interaction of visible light with thermally induced acoustic waves or phonons propagating at a speed of a few km/sec. Information on the elasticity and structure of the material is obtained in a nondestructive contactless manner, hence opening the way to in vivo applications and potential diagnosis of pathology. This work describes the application of Brillouin spectroscopy to the study of biomechanics in elastin and trypsin-digested type I collagen fibers of the extracellular matrix. Fibrous proteins of the extracellular matrix are the building blocks of biological tissues and investigating their mechanical and physical behavior is key to establishing structure-function relationships in normal tissues and the changes which occur in disease. The procedures of sample preparation followed by measurement of Brillouin spectra using a reflective substrate are presented together with details of the optical system and methods of spectral data analysis.
Highlights
The Brillouin light scattering (BLS) effect was discovered by Léon Brillouin in 1922.1 It consists of the inelastic scattering of visible light by thermally activated acoustic phonons in a material
Brillouin scattering spectroscopy is a unique tool by which the individual components of the elasticity tensor of a protein fiber can be characterized in unprecedented detail
The measurements can be made on a microscopic scale and thereby will provide us with novel insights into the micro-scale mechanics of biological structures, allowing us, for the first time, to understand the mechanical, and probably functional, significance of the complexities in matrix architecture and biochemistry which has been revealed in recent years
Summary
The Brillouin light scattering (BLS) effect was discovered by Léon Brillouin in 1922.1 It consists of the inelastic scattering of visible light by thermally activated acoustic phonons in a material. Networks of collagen often co-exist with networks of elastin, a protein which, unusually, generates long range elasticity through a combination of entropy and hydrophobic interactions with its environment and is essential to the functions of tissues such as lung and skin. Both fibers are modeled using a hexagonal crystal model in the current research.[9] In part 1, we describe the protocol to extract the fibers from animal tissues and to prepare the sample for the spectroscopic measurements.
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