Design and Evaluation of a New Electrophoretic Mobility Measurement Instrument Using Microelectrophoresis System With Image Processing Method

Abstract

Electrophoretic mobility (EPM) measurement on biological particles in fluids is well established. The current method in measuring EPM is using laser which the target particles are not visible. Additional morphology information is critical for the EPM measurement. Image processing is a promising method to obtain the EPM together with the morphology information. In this study, a setup of micro electrophoresis system with a compact CCD microscope was constructed. This setup was equipped with image processing method for capturing the images of the moving particles in an electric field. With the image processing method (Horn–Schunck method), the images captured were processed in real time to obtain the EPM of the particle. Velocity of the particles was then measured and the particles’ EPM was obtained. With the captured images of the particles in real time, the system can present the image of the targeted particle together with the EPM value. The setup of this prototype was calibrated with discrete particles (Polystyrene microsphere size of 10[Formula: see text][Formula: see text]m[Formula: see text] 5%) and with a magnification value of 125[Formula: see text]X. This system is suitable for the surface charge measurement of discrete particle with size in between 4[Formula: see text][Formula: see text]m and 20[Formula: see text][Formula: see text]m. Comparison of commercialized device with our laboratory setup for calibration on EPM of polystyrene beads had a variance of solely 13%. Measurement on yeast cells, normal (hFob 1.19) and cancer bone cells (U2OS) indicated that the EPM of yeast became highly negative in the pH value of 4.5 and 6.5. The negative EPM of the cancer cell is slightly larger than that of the normal cell for pH ranging from 4.4 to 5.0. In conclusion, the real-time EPM measurement set up for this study is able to display the real-time images of the moving particles in fluid suspension during measurement.