Kohles Sean S, Nève Nathalie, Zimmerman Jeremiah D, Tretheway Derek C
Department of Mechanical and Materials Engineering, Portland State University, Portland, OR 97207, USA.
J Biomech Eng. 2009 Dec;131(12):121006. doi: 10.1115/1.4000121.
Advancements in technologies for assessing biomechanics at the cellular level have led to discoveries in mechanotransduction and the investigation of cell mechanics as a biomarker for disease. With the recent development of an integrated optical tweezer with micron resolution particle image velocimetry, the opportunity to apply controlled multiaxial stresses to suspended single cells is available (Neve, N., Lingwood, J. K., Zimmerman, J., Kohles, S. S., and Tretheway, D. C., 2008, "The muPIVOT: An Integrated Particle Image Velocimetry and Optical Tweezers Instrument for Microenvironment Investigations," Meas. Sci. Technol., 19(9), pp. 095403). A stress analysis was applied to experimental and theoretical flow velocity gradients of suspended cell-sized polystyrene microspheres demonstrating the relevant geometry of nonadhered spherical cells, as observed for osteoblasts, chondrocytes, and fibroblasts. Three flow conditions were assessed: a uniform flow field generated by moving the fluid sample with an automated translation stage, a gravity driven flow through a straight microchannel, and a gravity driven flow through a microchannel cross junction. The analysis showed that fluid-induced stresses on suspended cells (hydrodynamic shear, normal, and principal stresses in the range of 0.02-0.04 Pa) are generally at least an order of magnitude lower than adhered single cell studies for uniform and straight microchannel flows (0.5-1.0 Pa). In addition, hydrostatic pressures dominate (1-100 Pa) over hydrodynamic stresses. However, in a cross junction configuration, orders of magnitude larger hydrodynamic stresses are possible without the influence of physical contact and with minimal laser trapping power.
细胞水平生物力学评估技术的进步推动了机械转导方面的发现，并将细胞力学作为疾病生物标志物进行研究。随着最近具有微米分辨率粒子图像测速技术的集成光镊的发展，现在有机会对悬浮的单个细胞施加可控的多轴应力（Neve, N., Lingwood, J. K., Zimmerman, J., Kohles, S. S., and Tretheway, D. C., 2008, “The muPIVOT: An Integrated Particle Image Velocimetry and Optical Tweezers Instrument for Microenvironment Investigations,” Meas. Sci. Technol., 19(9), pp. 095403）。对悬浮的细胞大小的聚苯乙烯微球的实验和理论流速梯度进行了应力分析，展示了未粘附的球形细胞的相关几何形状，如在成骨细胞、软骨细胞和成纤维细胞中观察到的那样。评估了三种流动条件：通过自动平移台移动流体样本产生的均匀流场、通过直微通道的重力驱动流以及通过微通道交叉路口的重力驱动流。分析表明，对于均匀和直微通道流动，悬浮细胞上的流体诱导应力（流体动力剪切、法向应力和主应力范围为0.02 - 0.04 Pa）通常比粘附单细胞研究中的应力至少低一个数量级（0.5 - 1.0 Pa）。此外，静水压力（1 - 100 Pa）比流体动力应力占主导地位。然而，在交叉路口配置中，在没有物理接触影响且激光捕获功率最小的情况下，可能会出现数量级大得多的流体动力应力。
