| Summary: | 碩士 === 國立中興大學 === 生物產業機電工程學系所 === 96 === Recently, the biosensors fabricated by microfabrication techniques have attracted a wide interest. The biosensor by using cells as the recognition element can be developed to become a cell-estimated platform. Because cellular metabolism will release the organic acid and carbon dioxide, the change of extracellular pH values can be used to estimate the metabolic physiological response of cells.
In this study, a pH-sensitive microchip integrated with a microfluidic system was developed to measure the pH change of medium resulted from the cellular metabolism. The microchip consisted of an glass substrate containing the pH-sensitive iridium oxide (IrOx) electrodes and a polydimethylsiloxane (PDMS) slab with a chamber connecting a microchannel. The pH-sensitive electrodes (20 μm × 20 μm) were made by electrodepositing IrOx layer onto the Au thin-film electrodes by means of the cyclic voltammetry from 0 V to 0.6 V with a scanning rate of 20 mV/s for 300 cycles, the surface of chip substrate was modified sequentially by poly-L-lysin and fibronectin to facilitate the adhesion of cells. The IrOx electrodes showed a good stability when dipping in a PBS solution for 24 h. The pH change calculated from the sensitivity within 10 min was only 0.002 mV. When flowing into and extract the PBS buffer solution of pH6.00 and pH7.00, respectively, the potential response was -77.80±2.39 mV, about 3.07% relative standard deviation (RSD). The HeLa cells were seeded in the microchamber for 10 min with the cell density of 1016 cells/mm2. The acidification rates of the adhered cells in 1 mM HEPES buffer containing glucose or insulin molecules were monitored. The result shows the acidification rate obtained in 25 mM glucose-containing and 25 mM glucose +1% insulin-containing buffer were 2.0 and 3.0 times larger than that in mannitol-containing buffer, respectively. The results indicate that the IrOx chip can successfully in situ monitor the metabolic response of cells to the extrinsic stimulation. In the future, it can be applied to drug screening area, etc.
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