School of Mechanical Engineering, Shenyang Jianzhu University , Shenyang, China.
State Key Laboratory of Robotics, Shenyang Institute of Automation , Chinese Academy of Sciences, Shenyang, China.
Biomicrofluidics. 2015 Feb 18;9(1):014121. doi: 10.1063/1.4913365. eCollection 2015 Jan.
In this paper, the translational motion and self-rotational behaviors of the Raji cells, a type of B-cell lymphoma cell, in an optically induced, non-rotational, electric field have been characterized by utilizing a digitally programmable and optically activated microfluidics chip with the assistance of an externally applied AC bias potential. The crossover frequency spectrum of the Raji cells was studied by observing the different linear translation responses of these cells to the positive and negative optically induced dielectrophoresis force generated by a projected light pattern. This digitally projected spot served as the virtual electrode to generate an axisymmetric and non-uniform electric field. Then, the membrane capacitance of the Raji cells could be directly measured. Furthermore, Raji cells under this condition also exhibited a self-rotation behavior. The repeatable and controlled self-rotation speeds of the Raji cells to the externally applied frequency and voltage were systematically investigated and characterized via computer-vision algorithms. The self-rotational speed of the Raji cells reached a maximum value at 60 kHz and demonstrated a quadratic relationship with respect to the applied voltage. Furthermore, optically projected patterns of four orthogonal electrodes were also employed as the virtual electrodes to manipulate the Raji cells. These results demonstrated that Raji cells located at the center of the four electrode pattern could not be self-rotated. Instead any Raji cells that deviated from this center area would also self-rotate. Most importantly, the Raji cells did not exhibit the self-rotational behavior after translating and rotating with respect to the center of any two adjacent electrodes. The spatial distributions of the electric field generated by the optically projected spot and the pattern of four electrodes were also modeled using a finite element numerical simulation. These simulations validated that the electric field distributions were non-uniform and non-rotational. Hence, the non-uniform electric field must play a key role in the self-rotation of the Raji cells. As a whole, this study elucidates an optoelectric-coupled microfluidics-based mechanism for cellular translation and self-rotation that can be used to extract the dielectric properties of the cells without using conventional metal-based microelectrodes. This technique may provide a simpler method for label-free identification of cancerous cells with many associated clinical applications.
本文利用数字可编程和光激活微流控芯片，在外加交流偏压的辅助下，研究了 Raji 细胞（一种 B 细胞淋巴瘤细胞）在光诱导、非旋转电场中的平移运动和自旋转行为。通过观察 Raji 细胞对投射光图案产生的正负光诱导介电泳力的不同线性平移响应，研究了 Raji 细胞的交叉频率谱。这个数字投影光斑充当虚拟电极，产生轴对称和非均匀电场。然后，可以直接测量 Raji 细胞的膜电容。此外，在这种情况下，Raji 细胞还表现出自旋转行为。通过计算机视觉算法，系统地研究和表征了 Raji 细胞在外部施加的频率和电压下的可重复和可控的自旋转速度。Raji 细胞的自旋转速度在 60 kHz 时达到最大值，并与施加的电压呈二次关系。此外，还使用四个正交电极的光投影图案作为虚拟电极来操纵 Raji 细胞。这些结果表明，位于四个电极图案中心的 Raji 细胞不能自旋转。相反，任何偏离该中心区域的 Raji 细胞也会自旋转。最重要的是，Raji 细胞在相对于任何两个相邻电极的中心平移和旋转后不会表现出自旋转行为。使用有限元数值模拟对光投影光斑和四个电极图案产生的电场分布进行建模。这些模拟验证了电场分布是不均匀和非旋转的。因此，非均匀电场必须在 Raji 细胞的自旋转中起关键作用。总的来说，本研究阐明了一种基于光电耦合的微流控细胞平移和自旋转机制，可以在不使用传统金属微电极的情况下提取细胞的介电特性。该技术可能为癌症细胞的无标记识别提供一种更简单的方法，具有许多相关的临床应用。
