Study And Application Of Portable Chemical Sensors Based On The Pressure Sensor

Due to the characteristic of "pocket" size, cost effectiveness, reliable quantitative results and easy operation, more and more attention has been paid to the technology of point-of-care testing ?POCT?. The development of POCT technology is a promising area of analytic for improving healthcare, maintaining sanitation and ensuring food safety. Pressure gauge is a useful portable device in our daily life or industrial production, which has not been taken full advantage in the area of analytic chemistry. In this paper, two portable biosensors by using Differential Pressure Gauge ?DPG? as readout had been developed for quantification of the analytes, the sensors have the characters of cost effectiveness, highly selective, reliable quantitative results and easy operation. Furthermore, pressure-sensitive Paint ?PSP? had been used as the sensing unit to develop a portable biosensor.In the first chapter of this paper, the fundamental conception, characteristics, classifications and development direction of piont-of-care test were introduced. Then several chemical sensors based on pressure change were described in detail. Finally, the purpose and contents of the thesis had been pointed out, the pressure changing of the system has been used as the sensing unit and three chemical biosensors had been developed. These biosensors have the character of cost effectiveness, reliable quantitative results and easy operation.In the second chapter, a portable chemical sensor for thrombin detection based on the strategy of aptamer has been developed. The detection and capture had been modified onto catalase and Streptavidin Magnespheres Paramagnetic Particles ?SA-PMPs? respectively, and employed as probes. In the presence of target, capture probe will combined with detection probe and bound with thrombin to form a G-quadruplex structure, allowing the catalase modified onto the PMPs, which can be separated easily by a magnet and added into the glass vial subsequently. Since the catalase was brought in the H₂O₂ solution along with PMPs, large amount oxygen constantly generated due to the decomposition of hydrogen peroxide and resulting in the enhancement of pressure in a closed glass vial within a defined time. Such micro-pressure change was monitored by a DPG in real time and gave out digital readout The change signal of DPG, exhibits a linear response to the concentration of thrombin in the range of 5?25 ng/mL. It is also found that the proposed sensor has good stability, high selectivity and low detection limit. Additionally, the proposed method has been applied to determine thrombin with satisfactory results.In the third chapter, a portable sensors for alpha fetoprotein ?AFP? detection based on immunoassay has been reported using a DPG as signal readout. On the basis of the second chapter, a sensor for AFP determination has been designed. In the presence of AFP, a sandwich immunocomplex of detection antibody-AFP-capture antibody ?coated in the well? was specifically formed. On the basis of the second chapter, the concentration of AFP could be quantitative readout by the DPG. And it shows a linear response to the concentration in the range of 10?200 ng/mL with the detection limit is 3.4 ng/mL. In addition, the sensor had been applied to detect AFP in the human serum sample with satisfactory results. Pt nonaparticle, a kind of efficient catalysts for decomposing of hydrogen peroxide, had been embedded in the SiO₂ to form Pt/SiO₂ nanoparticles, then the detection antibody was modified onto the SiO₂.In the fourth chapter, an optical portable biosensor for cocaine detection based on Pressure-sensitive Paint ?PSP? has been developed technology. The fluorescence and color of the PSP used are sensitive to the pressure, so PSP was employ as signal readout means which can be read by a fluorescence spectrophotometer or nake eye. A stable complex with a sanwich structure by SA-PMPs-aptamer DNA-Pt/SiO₂ was made to recognize target. In the presence of cocaine, the aptamer can react with cocaine and released the Pt/SiO₂,which can decompose hydrogen peroxide into H₂O and O₂ and be quantified by PSP. The result shows a linear response to the concentration of cocaine in the range of 50?250 nmol/L with the detection limit is 16.7 nmol/L. In addition, the sensor had been applied to detect cocaine in the sample with satisfactory results.