Savin Thierry, Doyle Patrick S
Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Biophys J. 2005 Jan;88(1):623-38. doi: 10.1529/biophysj.104.042457. Epub 2004 Nov 8.
Particle tracking techniques are often used to assess the local mechanical properties of cells and biological fluids. The extracted trajectories are exploited to compute the mean-squared displacement that characterizes the dynamics of the probe particles. Limited spatial resolution and statistical uncertainty are the limiting factors that alter the accuracy of the mean-squared displacement estimation. We precisely quantified the effect of localization errors in the determination of the mean-squared displacement by separating the sources of these errors into two separate contributions. A "static error" arises in the position measurements of immobilized particles. A "dynamic error" comes from the particle motion during the finite exposure time that is required for visualization. We calculated the propagation of these errors on the mean-squared displacement. We examined the impact of our error analysis on theoretical model fluids used in biorheology. These theoretical predictions were verified for purely viscous fluids using simulations and a multiple-particle tracking technique performed with video microscopy. We showed that the static contribution can be confidently corrected in dynamics studies by using static experiments performed at a similar noise-to-signal ratio. This groundwork allowed us to achieve higher resolution in the mean-squared displacement, and thus to increase the accuracy of microrheology studies.
粒子跟踪技术经常被用于评估细胞和生物流体的局部力学特性。提取的轨迹被用于计算均方位移，该均方位移表征了探针粒子的动力学特性。有限的空间分辨率和统计不确定性是改变均方位移估计准确性的限制因素。我们通过将这些误差源分为两个独立的部分，精确量化了定位误差在均方位移测定中的影响。“静态误差”出现在固定粒子的位置测量中。“动态误差”来自于可视化所需的有限曝光时间内粒子的运动。我们计算了这些误差在均方位移上的传播。我们研究了误差分析对生物流变学中使用的理论模型流体的影响。使用模拟和视频显微镜进行的多粒子跟踪技术，对纯粘性流体验证了这些理论预测。我们表明，在动力学研究中，通过使用在类似信噪比下进行的静态实验，可以可靠地校正静态贡献。这项基础工作使我们能够在均方位移上实现更高的分辨率，从而提高微观流变学研究的准确性。
