Department of Mechanical Engineering, Department of Biomedical Engineering, Tufts University, Medford, MA 02155, USA.
Methods. 2013 Apr 1;60(2):202-13. doi: 10.1016/j.ymeth.2013.03.037. Epub 2013 Apr 30.
Here we overview and further develop a quantitative method to measure mechanics of biological cells in indentation experiments, which is based on the use of atomic force microscopy (AFM). We demonstrate how the elastic modulus of the cell body should be measured when the cellular brush is taken into account. The brush is an essential inelastic part of the cell, which surrounds all eukaryotic (the brush is mostly microvilli and glycocalyx) and gram-negative prokaryotic cells (the brush is polysaccharides). The other main feature of the described method is the use of a relatively dull AFM probe to stay in the linear stress-strain regime. In particular, we show that the elastic modulus (aka the Young's modulus) of cells is independent of the indentation depth up to 10-20% deformation for the eukaryotic cells studied here. Besides the elastic modulus, the method presented allows obtaining the parameters of cellular brush, such as the effective length and grafting density of the brush. Although the method is demonstrated on eukaryotic cells, it is directly applicable for all types of cells, and even non-biological soft materials surrounded by either a brush or any field of long-range forces.
在这里，我们概述并进一步开发了一种在压痕实验中测量生物细胞力学的定量方法，该方法基于原子力显微镜（AFM）的使用。我们展示了当考虑细胞刷时如何测量细胞体的弹性模量。刷是细胞的一个必不可少的非弹性部分，它包围着所有真核生物（刷主要是微绒毛和糖萼）和革兰氏阴性原核生物（刷是多糖）。所述方法的另一个主要特点是使用相对钝的 AFM 探针保持在线性应力-应变范围内。特别是，我们表明，对于这里研究的真核细胞，弹性模量（又名杨氏模量）与压痕深度无关，可达 10-20%的变形。除了弹性模量外，所提出的方法还允许获得细胞刷的参数，例如刷的有效长度和接枝密度。尽管该方法是在真核细胞上进行演示的，但它可直接应用于所有类型的细胞，甚至是被刷或任何长程力场包围的非生物软材料。
