Develop urea biosensor based on an ammonium electrode

• Main Authors: Hao-Yu Wu, 吳皓羽
• Other Authors: Li-Te Yin
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/60809417830706171256

碩士 === 中華醫事科技大學 === 生物醫學研究所 === 102 === Ammonia (NH3) is a compound that exists ubiquitously in the atmosphere and natural water and is the compound having the simplest chemical structure among the nitrogen-containing species. In the case of pH value below 8, as ammonia dissolves in water, it reacts with water molecules to form ammonium ions (NH4+) mostly. When there is too much ammonia dissolved in water, the water becomes eutrophic, leading to the aquatic ecological imbalance. In the human body, the normal urea concentration in the plasma is 18-36 mg/dl whereas in the clinical practice urea is most often measured in term of the amount of nitrogen, namely the urea nitrogen. The concentration of urea nitrogen of 1 mg/dl is equivalent to a concentration of urea of 2.14 mg/dl. Urea nitrogen varies according to the human body condition and reflects on the variation of urea concentration. Therefore, measuring the concentration of urea in blood can be a meaningful method to monitor the body condition in the clinical practice. For the demand of detecting the ammonium ions of the ammoniacal nitrogen in the environment and of the urea nitrogen in the human body, if the lowest detection limit of the electrode described in this research publication can be fully developed, further lower concentrations of urea in the environment or human blood and urine can be measured more accurately. In this publication, the extended ITO/PET ion-sensitive field-effect transistors are used to produce the durable ammonium ion-selective electrodes for investigating the impact to the overall reaction affected by each parameter. According to the results of several experiments, the concentration of ammonium ion in the range between 10-5 ~ 1M is detectable with a linear range of about 0.99 and the average sensibility is 55.09 mV / pNH4+. As for the buffer solution, PB and Tris buffer solutions are used for measurement whereas the use of Tris buffer can stabilize the measuring results. While researching the references, some references indicate that the sensitivity can be better by adding EDTA in the buffer solution. Therefore, experiments with EDTA added and without EDTA added in the buffer solutions were both conducted. However, the results show that the experiments without adding EDTA have better sensitivities to the reactions. Since then, the experiments proceeded without EDTA. In order to demonstrate the value of this sensor whose lowest detection limit is lower than that of a traditional urea sensor, experiments thus have been conducted with the interval expansion of urea concentration (1mg/dl ~ 8mg/dl). The expansion result shows that this electrode is more sensitive than a regular sensor in reacting to lower urea concentrations, and the detection limit of this electrode is also lower. For monitoring the human body condition, to apply this dilution method to dilute the urea or blood from a normal body to the most suitable concentration level for measurement will bring the most sensitive and reliable reaction result in the future. Nothing is more serious than the water pollution in the detection of the environmental hazards. Therefore, this sensor is even more valuable when it comes to the monitoring of the water bodies. Since the urea produced by the ammonium ions in the water bodies is found in trace quantities, the lower the detection limit of the sensor is, the more sensitive and reliable result the sensor can produce while monitoring the extreme low concentration of urea produced by the ammonium ions. Therefore, this sensor can be used to monitor natural water bodies and environments. This sensor has a detection limit lower than that of a regular sensor and is of better sensitivity. This sensor can more quickly detect the low concentrations of urea exists in the environment in the future and can monitor the blood and urine in human bodies. If this electrode can be fully developed in the future, it can bring significant contribution to the environmental protection and human body wellness. Keywords: Ammonia, Ammonium biosensor, Ammonium ion-selective electrode