Developing GHz Acoustic Methods for Imaging and Measuring the Mechanical Properties of Individual Cells

细胞通过附着到周围环境来迁移，并通过重新排列内部结构来产生牵引力。这些牵引力的有效性取决于细胞内部结构(细胞骨架)和周围材料的相对刚性。这可以通过测量细胞的弹性属性(刚性)以及这些属性在迁移过程中在整个细胞中的变化来进行探索。有一些证据表明，随着细胞从正常状态转变为癌变状态，它们的僵硬程度会降低，随着这些细胞逐渐变得更具侵袭性，僵硬程度会进一步降低。因此，通过发展探索细胞机械特性的方法，我们可以研究细胞生物学和癌细胞生物学的一些基本方面。在这项提案中，我们将研究使用超高频声学成像来研究单个细胞的机械特性。在声学显微镜中，样品由频率范围为100 MHz-1 GHz的声波成像。图像对比度产生于声速的局部差异，而声速又是被成像材料弹性刚度的函数。因此，通过在一定的声频范围内测量细胞图像的对比度，可以确定空间分辨率约为1微米的局部机械特性。然而，为了使这项技术适用于研究细胞迁移过程中发生的生化和物理过程，有必要进一步发展这项技术，使其能够通过每隔几秒钟拍摄的图像快速获取数据。这项技术将通过对细胞系迁移的研究来演示，通过改变迁移过程中使用的一种蛋白质可以控制细胞系的迁移，从而使我们能够比较迁移迅速的细胞和更稳定的细胞。我们还将与英国癌症研究中心合作，他们将为我们提供已知侵袭能力的细胞系的例子，以表征它们的机械特性。

Cells migrate by attaching themselves to their surroundings and generating traction forces by rearranging their internal structure. The effectiveness of these tractions depend on the relative rigidity of the cells internal structure (its cytoskeleton) and that of the surrounding material. This can be probed by measuring the elastic properties (stiffness) of a cell and how these properties vary across the cell during migration. There is some evidence that as cells transform from the normal to the cancerous state, their stifness is reduced, and as these cells become progressively more invasive the stiffness is reduced further. Thus by developing methods to probe the mechanical properties of cells we can investigate some fundamental aspects of cell biology and cancer cell biology. In this proposal we will investigate the use of ultra-high frequency acoustic imaging to study the mechanical properties of individual cells. In an acoustic microscope specimens are imaged by acoustic waves in the frequency range 100 MHz - 1 GHz. Image contrast occurs from local differences in the speed of sound, which in turn is a function of the elastic stiffness of the material being imaged. Thus, by measuring the contrast of images of cells at a range of acoustic frequencies it is possible to determine local mechanical properties with a spatial resolution of around 1 micron. However, for this technique to be applicable to the study of the biochemical and physical processes that occur during cell migration, it is necessary to further develop the technique to allow the rapid acquisition of data through images taken every few seconds. The technique will be demonstrated through the investigation of the migration of cell lines that can be controlled by altering one of the proteins used during the migration process thus allowing us to compare cells that migrate rapidly with those that are more static. We will also work in collabnoration with Cancer Research UK who will provide examples of cell lines of known invasive capability for us to characterize their mechanical properties.