BACKGROUND Biological cells exhibit complex mechanical properties which determine their responses to applied force. OBJECTIVE We developed an optical method to probe the temporal evolution of power-law rheology of single cells. METHODS The method consisted in applying optically a constant mechanical torque to a birefringent microparticle bound to the cell membrane, and observing dynamics of the particle's in-plane rotation. RESULTS The deformation dynamics of the membrane followed a power law of time, which directly relates to cytoskeletal prestress as reported in the literature. The temporal evolution of this rheological behaviour, over time scales of several minutes, showed strong variations of the exponent on single adherent cells not subject to any specific treatment. CONCLUSIONS The consistent observation of variations in the exponent suggests that, in their normal activity, living cells modulate their prestress by up to three orders of magnitude within minutes.

中文翻译：

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光学扭曲可监控单个细胞的流变性。

背景技术生物细胞表现出复杂的机械性能，这些机械性能决定了它们对施加力的反应。目的我们开发了一种光学方法来探测单细胞幂律流变学的时间演变。方法该方法包括在光学上向与细胞膜结合的双折射微粒施加恒定的机械扭矩，并观察微粒在平面内旋转的动力学。结果膜的变形动力学遵循时间幂律，这直接关系到文献中报道的细胞骨架预应力。在几分钟的时间内，这种流变行为的时间演变表明，未经任何特殊处理的单个贴壁细胞的指数变化很大。