| Summary: | 博士 === 國立成功大學 === 醫學工程研究所碩博士班 === 92 === Recently, electrical impedance monitoring has become an emerging tool for biomedical research and medical practice. The passive electrical properties provide fruitful information of biological components. The traditional measuring technique revealed several important physical parameters including impedance, admittance, phase angle, and frequency response, those can be resolved precisely in a real-time manner. The measurements require no sophisticated instrumentation to achieve the bioanalytical goals. Recent impedimetric bioanalytical applications include pharmaceutical screening, coulter counter, hematocrit measurement, toxin detection, cell culture, and other clinical and environmental monitoring. Microfabricated devices (microelectrodes) further expended their bioanalytical possibility.
Impedimetric monitoring for cell attachment/detachment
In this thesis, impedimetric approaches for monitoring cellular behaviors are demonstrated. The changes in admittance on interdigitated microelectrode plate (IMP) could be obtained when the seeding cell attached to the electrode surface coated with or without RGD-C (Arginine-Glycine-Aspartic Acid-Cellulose binding domain) peptide. The results indicated that a decrement of the conductance at a low frequency of less than 10 kHz responded to the degree of the cell attachment on the electrode surface of IMP. However, there was no significant relationship between the conductance and cell status under the high operating frequency ranging from 105 to 106 Hz. In contrary to the change in conductance, the more cell attachment was, the larger suspectance increased in higher frequency. On RGD-C coated electrode, both the initial time and the finished time for MDCK cell attachment were significantly shorter than that on bare IMP. The conductance change obtained at lower frequency (1 kHz) can allow us to calculate the initial (ti) and finished (tf) time of cell attachment, and the decrement in conductivity (delta G) from ti to tf was obtained and further used to count the initial number of seeding cell. A relationship between delta G and the number of MDCK cell attachment on IMP at 1 kHz frequency was established. As a result, the detection range was around at 102-107 cells/cm2 by using the bare or RGD-C coated IMP, and -0.0003 (r = 0.92) and -0.0002 (r = 0.94) was separately calculated as the quantitative slope (correlation coefficient r), indicative of a good ability in counting cell number.
Quantitative study on perspiration by applying EIA technique
Clinical applications of impedimetric method were also studied; a sensitive and real-time device was constructed to monitor sweating process. The humidity sensor is effective in diagnosing hypohidrosis syndrome. The impedance type humidity transducer was made from a poly- (2-acrylamido-2-methy propane sulfonate) polymer film (PAMPS), was impedance type. The detecting range of the sensor is from 30%RH to 95%RH with a log scale, a good linearity exists between the impedance and humidity change, and the resolution (sensitivity) is 6%RH/ms (0.1%RH). This device was applied to assessing the sweating on palm of the normals. Measuring system constructed by a conductometric humidity sensor and a stopped-flow manifold with suitable dynamic range to monitor impaired perspiration. The perspiration from palms of normal individuals and hypohidrosis patients were also monitored and compared. Tangent slopes of the sensorograms were used as an index for discriminating hypohidrosis patients from normal individuals. The conductometric min-sensor and the stopped-flow manifold were proven to be useful as a diagnostic tool for hypohidrosis.
In summary, these researches have successfully demonstrated that EIA method with microelectrodes of interdigited structure can be used to monitor the cell attachment/detachment over a wide range of frequencies, the interaction between cell and ECM and for the diagnosis of hypohidrosis patients. Currently, this method is continuously improved for applications in cryo-biology study and various cell physiology studies
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