Ultrasonic Nano-imaging of Vascular Endothelial Cell

在电子扫描显微镜和激光扫描显微镜的荧光技术中，为了对细胞进行精确成像，需要进行抗体检测等预处理。无预处理的细胞非接触式纳米成像有望在各种条件下重复测量。本研究的目的是开发一种可以用高频超声测量细胞声速、衰减和声阻抗的纳米成像系统。此外，我们比较了细胞和细胞骨架（如肌动蛋白丝或微管蛋白）内声学特性的分布，以证明该系统在细胞生物力学测量中的实用性。将高速机械开关产生的脉冲宽度为2 ns的电脉冲直接输入到超声换能器中。用数字示波器分析了脉冲响应。采用微机板控制的两个伺服直线电机对成像系统的x轴和y轴进行扫描。整个系统由工作站控制，在2分钟内完成300x300点数据采集。在频域分析了试样表面反射与玻片界面反射之间的干涉。建立了计算试件厚度和声速的算法，最后给出了二维声速定量分布图。采用肌动蛋白丝染色、电阻抗测量和纳米成像技术研究肺血管内皮细胞的冷却作用。结果表明该系统在细胞生物力学研究中是有用的。

For precise imaging of cells, pre-treatments such as antibody sensing are needed in electron scanning microscopy and laser scanning microscopy with fluorescence technique. Non-contact nano-imaging of cells without pre-treatment is anticipated for repeated measurements under various conditions. The objective of the present research is to develop a nano-imaging system that can measure sound speed, attenuation and acoustic impedance of cells with high frequency ultrasound. Further, we compare the distribution of acoustic properties within a cell and cytoskeleton such as actin filaments or tubulin in order to prove the usefulness of the system in the measurement of cellular biomechanics.An electric pulse with the pulse width of 2 ns was generated by high speed mechanical switching was directly input into the ultrasonic transducer. The pulse response was analyzed by a digital oscilloscope. Two servo linear motors controlled by a microcomputer board were used for the scanning in both x- and y-axis of the imaging system. The total system was controlled by a workstation and 300x300 points data acquisition was done within two minutes. The interference between reflections from the surface of the specimen and the interface between the specimen and a glass slide was analyzed in frequency domain. The algorithm for calculation of the thickness and the sound speed of the specimen was established and finally two-dimensional mapping of quantitative sound speed distribution was displayed.Cooling effect of pulmonary vascular endothelial cells was investigated with actin filaments staining, electric impedance measurement and nano-imaging system. The results indicated the usefulness of the system for investigation of cellular biomechanics.