Duke University, Department of Biomedical Engineering, Durham, North Carolina.
Duke University, Department of Biomedical Engineering, Durham, North Carolina.
Biophys J. 2019 Aug 20;117(4):696-705. doi: 10.1016/j.bpj.2019.07.008. Epub 2019 Jul 12.
Many approaches have been developed to characterize cell elasticity. Among these, atomic force microscopy (AFM) combined with modeling has been widely used to characterize cellular compliance. However, such approaches are often limited by the difficulties associated with using a specific instrument and by the complexity of analyzing the measured data. More recently, quantitative phase imaging (QPI) has been applied to characterize cellular stiffness by using an effective spring constant. This metric was further correlated to mass distribution (disorder strength) within the cell. However, these measurements are difficult to compare to AFM-derived measurements of Young's modulus. Here, we describe, to our knowledge, a new way of analyzing QPI data to directly retrieve the shear modulus. Our approach enables label-free measurement of cellular mechanical properties that can be directly compared to values obtained from other rheological methods. To demonstrate the technique, we measured shear modulus and phase disorder strength using QPI, as well as Young's modulus using AFM, across two breast cancer cell-line populations dosed with three different concentrations of cytochalasin D, an actin-depolymerizing toxin. Comparison of QPI-derived and AFM moduli shows good agreement between the two measures and further agrees with theory. Our results suggest that QPI is a powerful tool for cellular biophysics because it allows for optical quantitative measurements of cell mechanical properties.
已经开发出许多方法来描述细胞弹性。其中，原子力显微镜（AFM）结合建模已被广泛用于描述细胞顺应性。然而，这些方法通常受到使用特定仪器的困难以及分析测量数据的复杂性的限制。最近，定量相位成像（QPI）已被用于通过使用有效弹簧常数来描述细胞硬度。该指标进一步与细胞内的质量分布（无序强度）相关联。然而，这些测量结果很难与 AFM 得出的杨氏模量测量结果进行比较。在这里，我们描述了一种新的分析 QPI 数据的方法，以直接获取剪切模量。我们的方法能够对细胞力学特性进行无标记测量，并且可以与其他流变学方法获得的值直接进行比较。为了验证该技术，我们使用 QPI 测量了剪切模量和相位无序强度，以及使用 AFM 测量了两种乳腺癌细胞系在三种不同浓度细胞松弛素 D 处理下的杨氏模量，细胞松弛素 D 是一种肌动蛋白解聚毒素。QPI 衍生的模量和 AFM 模量之间的比较表明，这两种测量方法之间具有良好的一致性，并且进一步与理论一致。我们的结果表明，QPI 是细胞生物物理学的有力工具，因为它允许对细胞力学特性进行光学定量测量。
