Ultrasonic Nano-imaging of Vascular Endothelial Cell

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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.