Study Of Membrane Capacitance Measurement Based On Network Analyzer AD5933

The measurement of membrane capacitance of cells has important physiological significance. When cell endocytosis and exocytosis occur, the plasma membrane area will be changed, and so does the membrane capacitance, thus cell endocytosis and exocytosis can be detected by testing the membrane capacitance. Patch-clamp amplifier is an important instrument to investigate membrane capacitance. An exciting signal generated by a patch-clamp amplifier went through the cell and then returned, carring the information about quantity of the cell membrane impedance network, with which we could calculate out the membrane impedance using the orthogonal analysis multiplied by the original exciting signal. The whole impedance system of a cell membrane can be described as a equivalent circuit that included three parameters: membrane capacitance (Cm), membrane resistance (Rm) and series resistance (Rs). To detect these parameters, we may adopt the"Sine+DC"approach, which determines the actual value of each, or the"piecewise-linear"approach, through which only changes in the parameters are estimated, then the changes of membrane capacitance can be observed.In the thesis, the output and input of Impedance Converter--AD5933 were adjusted to available levels, and connected to patch-clamp amplifier to observe cell membrane capacitance. The controlling command and acquired data were transmitted by serial port communication between the Micro-Computer Unit (MCU) SST89E516 and the host computer.Three parts were included in this thesis:1) The basic functions of AD5933 were introduced, and some results of the tests were presented;2) To meet the requirements in measuring capacitance of cells membrane, the cause of inaccuracy of measurement in low frequency was analysed and the correct approach was induced;3) The time resolution of measurement by AD5933 was analysed.Our approach differed from the EPC-9 patch-clamp amplifier in that we use the hardware method rather than software ones in the first several steps of impedance measurement, By this means we expect that the measuring noise in membrane capacitance measurement could be decreased.