Moura Afonso L D, Tejedor Jaime R, Espinosa Francisco M, Dominguez Lázaro A, de Sousa Jeanlex S, Garcia Ricardo
Instituto de Ciencia de Materiales de Madrid, CSIC c/Sor Juana Inés de la Cruz 3, 28049 Madrid, Spain.
Departamento de Física, Universidade Federal do Ceará, 60451-970 Fortaleza, Ceará, Brazil.
Nanoscale. 2025 Jun 19;17(24):14897-14903. doi: 10.1039/d5nr01236h.
AFM is the dominant method to characterize the nanomechanical properties of cells. These properties are obtained by model fitting. Semi-infinite contact mechanics models predict that the force depends on the cell's mechanical properties, indentation and the tip's geometry. Finite-thickness rheological models predict that the force should depend also on the rigidity of the substrate. The latter property has never been observed experimentally. It would make cells appear stiffer than they are. Here, we designed a force-distance curve experiment to reveal the influence of the rigidity of the substrate on the forces and the apparent moduli measured by AFM. Model fitting by using a semi-infinite power-law rheological model showed an increase of the apparent modulus with increasing force. This behavior was an artifact which disappeared when the force was fit with a bottom-effect correction model. Our findings demonstrated that the force applied on a cell depended intrinsically on the stiffness of the substrate while the mechanical properties (true values) did not.
原子力显微镜（AFM）是表征细胞纳米力学特性的主要方法。这些特性通过模型拟合获得。半无限接触力学模型预测，力取决于细胞的力学特性、压痕和尖端的几何形状。有限厚度流变模型预测，力还应取决于基底的刚度。后一种特性从未在实验中观察到。这会使细胞看起来比实际更硬。在这里，我们设计了一个力-距离曲线实验，以揭示基底刚度对通过AFM测量的力和表观模量的影响。使用半无限幂律流变模型进行模型拟合表明，表观模量随力的增加而增加。这种行为是一种假象，当使用底部效应校正模型对力进行拟合时，这种假象就会消失。我们的研究结果表明，施加在细胞上的力本质上取决于基底的刚度，而力学特性（真实值）则不然。
