Goicochea A Gama, Guardado S J Alas
Instituto de Física, Universidad Autónoma de San Luis Potosí Álvaro Obregón 64, San Luis Potosí 78000, Mexico.
Departamento de Ciencias Naturales, Universidad Autónoma Metropolitana Unidad Cuajimalpa, Av. Vasco de Quiroga 4871, Distrito Federal 05300, Mexico.
Sci Rep. 2015 Aug 28;5:13218. doi: 10.1038/srep13218.
We report a model for atomic force microscopy by means of computer simulations of molecular brushes on surfaces of biological interest such as normal and cancerous cervical epithelial cells. Our model predicts that the force needed to produce a given indentation on brushes that can move on the surface of the cell (called "liquid" brushes) is the same as that required for brushes whose ends are fixed on the cell's surface (called "solid" brushes), as long as the tip of the microscope covers the entire area of the brush. Additionally, we find that cancerous cells are softer than normal ones, in agreement with various experiments. Moreover, soft brushes are found to display larger resistance to compression than stiff ones. This phenomenon is the consequence of the larger equilibrium length of the soft brushes and the cooperative association of solvent molecules trapped within the brushes, which leads to an increase in the osmotic pressure. Our results show that a careful characterization of the brushes on epithelial cells is indispensable when determining the mechanical response of cancerous cells.
我们通过对生物相关表面（如正常和癌性宫颈上皮细胞）上的分子刷进行计算机模拟，报告了一种原子力显微镜模型。我们的模型预测，只要显微镜尖端覆盖刷子的整个区域，在可在细胞表面移动的刷子（称为“液体”刷子）上产生给定压痕所需的力与末端固定在细胞表面的刷子（称为“固体”刷子）所需的力相同。此外，我们发现癌细胞比正常细胞更柔软，这与各种实验结果一致。而且，发现软刷子比硬刷子表现出更大的抗压性。这种现象是软刷子平衡长度较大以及被困在刷子内的溶剂分子协同缔合的结果，这导致渗透压增加。我们的结果表明，在确定癌细胞的力学响应时，仔细表征上皮细胞上的刷子是必不可少的。
