A New Platform for Biomechanical Imaging Based on Brillouin Scattering

人体组织的机械变化广泛地与各种临床问题有关，包括糖尿病、动脉粥样硬化和癌症等许多严重的并发症，但其微观结构基础尚不清楚。在大血管中，僵硬与心血管死亡的风险增加有关--尽管单个组织成分的僵硬对这种风险的贡献尚不清楚。我们在长度尺度上测量机械性能的能力限制了我们对将硬度与结构联系起来的机制的理解，这使得我们能够建立与组织结构和组成的关系。BLS显微镜有可能填补这一空白，正如最近的一篇论文(Palombo，Madami，Stone and Fioretto，Analyst，2014,139,729-733)所展示的那样，其中基于对应于特定组织成分的布里渊峰值生成了结构和弹性的机械图。成像细胞和组织的化学成分的新技术正在生物学和医学的许多领域产生重大影响。这项建议涉及发展布里渊光散射(BLS)成像，这是一种新的力学性能的微观成像方法。结缔组织、软骨或血管的机械性能是其生理功能的核心，机械功能的变化与从糖尿病到骨关节炎的各种疾病有关。因此，BLS成像提供了直接成像的前景，无论是在组织中还是在单一成分如胶原和弹性蛋白纤维中，其生物力学在多个频率下的探索几乎是完全未知的，这将打开组织力学的新窗口，并提供开发新诊断技术的前景。该方法的原理是检测样品中产生的声波引起的非弹性散射光的频率变化。对波速的计算提供了对材料机械性能的测量。初步研究已经使用共聚焦BLS显微镜来产生上皮组织的布里渊频率图，该图可以与化学成分的拉曼显微光谱图相结合(Palombo等人。分析师2014)。补充性研究已经研究了胶原和弹性蛋白中的布里渊散射，以及它们与纤维微观力学的关系(Palombo等人。J R Soc接口，ASAP)。这项工作为拟议的调查提供了基础。该方法将适用于结缔组织生理学和病理学的许多问题，但近期的目标将是研究细胞外蛋白纤维-胶原蛋白、弹性蛋白、蛋白多糖-的机制以及生理和病理条件的影响。这些变化广泛地与各种临床问题有关，包括许多严重的骨关节炎和糖尿病并发症，但其微观结构基础尚不清楚。该项目将需要建造一个系统，该系统将通过使用虚拟成像相位阵列(VIPA)光谱仪的布里渊散射实现生物力学成像。这将使我们能够开发一种更快、更通用的纤维(和组织)分析技术，并确定功能上的重大变化，从长远来看，这些变化可能成为监测或治疗干预的目标。

Mechanical changes in body tissues are widely associated with diverse clinical problems including many of the serious complications of diabetes, atherosclerosis and cancer, but their microstructural bases are poorly understood. In large blood vessels, stiffness is linked to increased risk of cardiovascular mortality - although the contribution of the stiffness from individual tissue constituents to this risk is unknown. Understanding the mechanisms linking stiffness to structure is limited by our ability to measure mechanical properties on length-scales which allow the relationships with tissue structure and composition to be established. BLS microscopy has the potential to fill this void, as demonstrated in a recent publication (Palombo, Madami, Stone and Fioretto, Analyst, 2014, 139, 729-733) where mechanical maps of structure and elasticity were generated based on Brillouin peaks corresponding to specific tissue components. New techniques of imaging the chemical composition of cells and tissues are making a major impact in many fields of biology and medicine. This proposal is concerned with the development of Brillouin light scattering (BLS) imaging, a new method for microscopic imaging of mechanical properties. The mechanical properties of the connective tissues, cartilage or blood vessels are central to their physiological function and changes in mechanical function are implicated in diseases ranging from diabetes to osteoarthritis. BLS imaging therefore offers the prospect of directly imaging a functionally important property, both in tissues and single constituents e.g. collagen and elastin fibres, whose biomechanics probed at multiple frequencies are almost completely unexplored, which will open a new window on tissue mechanics and offers the prospect of developing new diagnostic techniques.The principle of the approach is to detect the change in frequency of inelastically scattered light arising from the generation of sound waves in the sample. Calculation of the speed of the wave provides a measure of the mechanical properties of the material. Preliminary studies have used confocal BLS microscopy to produce Brillouin frequency maps of an epithelial tissue, which can be combined with Raman micro-spectroscopic maps of chemical composition (Palombo et al. Analyst 2014). Complementary studies have investigated Brillouin scattering in collagen and elastin, the fibrous proteins of the extracellular matrix, and their relationships to fibre micromechanics (Palombo et al. J R Soc Interface, asap).This work provides the basis for the proposed investigations. The methodology will be applicable to many problems of connective tissue physiology and pathology, but the immediate aim will be to investigate the mechanics of extracellular protein fibres - collagens, elastin, proteoglycans - and the effects of physiological and pathological conditions. These changes are widely associated with diverse clinical problems including many of the serious complications of osteoarthritis and diabetes, but their microstructural bases are poorly understood. The project will require construction of a system that will enable biomechanical imaging through Brillouin scattering with a Virtually Imaged Phase Array (VIPA) spectrometer. This will enable us to develop a significantly faster and more versatile technology for the analysis of fibres (and tissues) and to define functionally significant changes which can, in the longer term, become targets for monitoring or therapeutic intervention.