Dissertations / Theses on the topic 'Urea biosensor'

An impedance bioanalyzer system comprising an in-vitro biotransducer, instrumentation and control software for the measurement of urea, potentially in blood dialysate, has been developed. The biotransducer comprises of a microlithographically fabricated interdigitated microsensor electrode (IME) onto which was cast a biorecognition layer conferred with the specificity of the enzyme urease. Urease hydrolysis of urea produces NH4+, HC03- and OH- ions that decrease the device's impedance. The temporal rate of change (kinetic) and the extent of change (equilibrium) of ion concentration were measured as the sensor's response. Five formats: [i) unPEGylated urease-containing poly(hydroxyethylmethacrylate) [p(HEMA)] hydrogel, ii) PEGylated urease-containing p(HEMA) hydrogel, iii) via glutaraldehyde crosslinking in the presence of albumin, iv) the direct covalent immobilization of urease to the IME, and v) solution borne urease]. Michaelis-Menten parameters KM, ZMAX and kcat revealed the following rank: PEGylated urease-Gel >> Free Urease > unPEGylated urease-Gel = BSA in Glutaraldehyde > covalently immobilized urease. The unPEGylated-urease sensor provided a higher enzyrne- substrate binding rate and catalysis rate than PEGylated and thus provided a faster impedimetric response to various molar concentrations of urea. Long-term stability (one month) of the PEGylated-urease hydrogel was favorable. A dedicated three-element array impedimetric instrument, the 3EIC BioAnalyzer was designed and produced. A pair of demodulating logarithmic amplifiers (AD8302) was used to calculate the change in phase and amplitude corresponding to the impedimetric response to a 4.0 kHz, 50 mVPP sine wave from a function generator (MAX038). A graphic user interface (GUI), programmed in LabVIEW 7.0 established instrument control, data acquisition via a USB-48A-30A16 μDAQ and graphical data presentation of temporal impedimetric responses.

Sensores são dispositivos capazes de captar um determinado sinal físico -químico do meio e converte-lo num sinal elétrico mensurável por meio de um transdutor. Biossensor é um sensor que tem como parte funcional um receptor biológico específico a determinado analito alvo. Os sinais físico-químicos experimentados por estes dispositivos são convertidos em sinais elétricos de magnitude proporcional à concentração de um ou mais compostos químicos. Neste trabalho, foi construído um sensor de pH utilizando filmes finos comerciais de óxido de estanho dopado com flúor (FTO) como receptor a íons. O sensor foi feito ligando-se amostras de FTO ao terminal de porta de um transistor de efeito de campo do tipo MOS (Metal Oxide Semiconductor). Quando colocado em solução, os íons presentes interagem com a amostra sendo adsorvidos na superfície do filme de FTO. O potencial gerado pelos íons adsorvidos modulam a tensão na porta do transistor e, desta maneira, pode -se determinar a concentração dos íons presentes na solução de acordo com a magnitude da resposta do transistor. A este tipo de dispositivo dá -se o nome de EGFET (Extended Gate Field Effect Transistor). O EGFET construído apresentou responsividade de 55 mV/pH e resposta linear em soluções de pH 2 ao 12. Através de técnicas de imobilização enzimática foi possível ligar covalentemente proteínas urease sobre a superfície dos filmes de FTO, convertendo o sensor de pH em biossensor de ureia. Soluções tampão com diferentes pHs e concentrações foram testadas e determinou -se que as condições ideais para o uso deste biossensor de ureia são soluções tampão com pH = 6 e concentração de 10mM. Nessas condições, o biossensor apresentou uma responsividade de 114,5 mV/p(ureia) e linearidade no intervalo de concentrações de ureia entre 3,2.10 -4 e 3,2.10 -2 mol/L.
Sensors are devices capable of capturing a certain physical-chemical signal from environment and convert it into a measurable electrical signal by a transducer. Biosensor is a sensor which has a biological sensing element as receptor specific to a particular target analyte. The physical-chemical signals experienced by these devices are converted into electrical signals with magnitude proportional to the concentration of one or more chemical compounds. In this work, we built a pH-sensor using commercial thin films of tin oxide doped with fluorine (FTO) as ions receptor. The sensor was made by linking FTO samples to the gate of a field effect transistor MOS type. In solution, the ions interact with the sample being adsorbed on the surface of FTO film. The potential generated by the ions adsorbed on film\'s surface modulate the gate voltage of the transistor and, in this way, we can determine the concentration of ions present in solution correlated with the magnitude of the transistor response. This kind of device is given the name of EGFET (Extended Gate Field Effect Transistor). The EGFET built exhibits sensitivity of 55 mV/pH and linear response in the range of pH 2 to 12. Through enzyme immobilization techniques we could covalently bind urease proteins on the surface of FTO film, changing the pH-sensor in urea biosensor. Buffer solutions with differents pHs and concentrations were tested and was determined that optimal environment conditions for this urea biosensor is buffer solutions with pH = 6 and 10mM of concentration. Under these conditions, the biosensor showed sensitivity of 114.5 mV/p(urea) and linear response in the range of 3,2.10 -4 to 3,2.10 -2 mol/L

Este trabalho apresenta o desenvolvimento de biossensores de pH, ureia e glicose, utilizando óxidos como plataforma para a parte seletiva. Os filmes finos de óxidos condutores foram produzidos por diferentes técnicas de deposição, como spin-coat, dip-coat, spray-pyrolysis e casting. Os materiais fabricados foram AZO e TiO2, ambos depositados sobre substratos de FTO, ITO ou vidro hidroflilizado. O número de camadas foi variado para cada técnica e as caracterizações morfológicas e estruturais foram feitas por MEV, DRX e FTIR. As caracterizações elétricas foram feitas por EGFET e voltametria cíclica. Os filmes foram testados como sensores de pHs na faixa de 2 a 8. O filme depositado com AZO em substrato de FTO pela técnica de spray-pyrolysis apresentou melhor resposta, com sensibilidade de 31,7 mV/pH entre toda a faixa de pHs do 2 ao 8. Já para os filmes de TiO2, o filme produzido por dip-coat com 5 camadas em substrato de FTO apresentou sensibilidade de 37,8 mV/pH entre a faixa de pHs de 2 a 8. Paralelamente, os filmes tiveram suas superfícies funcionalizadas com proteínas como urease ou glicose oxidase. Neste caso, os dispositivos foram testados entre as concentrações de 5 a 200 mg/dL de ureia e glicose. Como biossensor de ureia, o filme de TiO2 depositado por spin-coat com 5 camadas em substrato de FTO apresentou a maior sensibilidade, com valor 3,32 mV/(mg/dL) entre as concentrações de 5 a 120 mg/dL. Para os filmes estudados como biossensores de glicose, o melhor resultado também foi obtido pelo filme de TiO2 depositado por spin-coat com 5 camadas em substrato de FTO, apresentando sensibilidade em torno de 6,18 mV/(mg/dL) entre as concentrações de 5 a 200 mg/dL. Alguns resultados encontrados foram iguais ou melhores aos encontrados na literatura vigente, mesmo que os dispositivos ainda são passíveis de otimização.
This study presents the development of pH, urea and glucose biosensors, by the use of oxides as the base of the sensing membrane. Conducting oxide thin films were prepared by different deposition techniques, such as spin-coat, dip-coat, spray-pyrolysis, and casting. AZO and TiO2 were produced and coated onto FTO, ITO and glass substrates. The number of layers were changed for each deposition technique, and the surface characterizations were made by SEM, XRD and FTIR, while the electrical characterizations were performed with an EGFET device and cyclic voltammetry. The samples were used as pH sensors in the pH range from 2 to 8. The AZO thin film onto FTO substrate deposited by spray-pyrolysis deposition technique presented sensitivity as 31.7 mV/pH for the total pH range from 2 to 8. TiO2 thin films, produced by dip-coat deposition technique with 5 layers onto FTO substrate presented 37.8 mV/pH as sensitivity, for the same pH range. All the films have their surfaces immobilized with proteins as urease or glucose oxidase. In this case, the samples were performed in different concentrations of urea or glucose, respectively, from 5 to 200 mg/dL, for both. Urea biosensors presented good results for measurements performed with the same sample as well as performed with individuals samples, for all the concentrations range. Spin-coated TiO2 thin films with 5 layers onto FTO substrates presented 3.32 mV/(mg/dL) as sensitivity from 5 to 120 mg/dL urea concentrations, while for glucose biosensors presented 6.18 mV/(mg/dL) for the same film between the glucose concentration range from 5 to 20 mg/dL. Some results were equal or better than the results in current literature, even the films are still capable of optimization.

Modélisation théorique de la variation de pression de gonflement d'un gel de polyacide faiblement dissocié dans le cas d'une variation du pH ou de la force ionique, d'une réaction enzymatique produisant une base forte dans la solution externe ou dans le gel même. Etude expérimentale des variations de pression de gonflement de gels de polyacrylamide partiellement hydrolysé ou de gélatine lors de l'hydrolyse de l'urée par l'uréase. Discussion de l'application de ces systèmes au domaine des biocapteurs

Orientador: Graciliano de Oliveira Neto
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica
Made available in DSpace on 2018-07-19T23:53:12Z (GMT). No. of bitstreams: 1 RoverJunior_Laercio_M.pdf: 1973498 bytes, checksum: a8176355af0b235fa0b0fdf3bd93dfe8 (MD5) Previous issue date: 1995
Mestrado

碩士
淡江大學
化學學系碩士班
95
The copper(I) oxide based urea biosensor was fabricated in this experiment, and it possessed reduced overvoltage for ammonia determination. The enzyme Urease (EC 3.5.1.5) was drop-coated on the up-stream of dual electrode and subsequently the NH3 was determination through copper(I) oxide modified down-stream electrode. The preparation of this biosensor was as follows, carbon ink and 20% copper(I) oxide had been well mixed and drop-coated on the downsteam electrode ; the urease (0.5 unit) was dropped on the upstream and dried secondly;the 1% 0.5 μl bovine serum albumin drop-coated on the upstream and dried; the 1% 0.5 μl glutaraldehyde dropped on the upstream and dried finally. The optimized conditions in the 0.05M pH 9 carbonate buffer ; applied potential was 0.2 V (vs. Ag/AgCl) ; flow rate was 0.5 ml/min; sample loop was 50 μl. The analytical performances of biosensor equipped with linear range upto 10 mM(R=0.99) and sensitivity is 85.736 nA/mM, detection limit (S/N=3) was 85 μM, and precision is 1.8% by twenty successive measurement. In order to eliminate interference, PbO2 was used to pre-oxidize those easily oxidative compounds, such as ,dopamine, epinephrine, serotonin, histamine , acetaminophen ,uric acid, ascorbic acid. Compared with standard method (sigma640), the correlation coefficient was 0.995.

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

碩士
逢甲大學
化學工程學系
101
In this study, ITO glass as a substrate and using constant potential method on ITO glass coated with ZnO film to increase its electrical conductivity. after that, we use self-assembled technology at the 3-aminopropyltrimethoxysilane (APTMS) coated on the ZnO film and use the covalent bonding method that to form amide bond between urease and amino group on the sensor electrode. Pt-C catalyst was added to enhance potential signal. The enzyme electrode to be detect in electrochemical sensing system. Looking for the best preparation conditions for the enzyme electrode. Finally, the performances of the enzyme electrodes made from different temperature and different pH were examined and compared. 　　According to the experimental results, urease concentration of 80 mg/ml makes the best enzyme electrode. At T = 50℃, pH = 7 environment, with the best sensitivity 43.600 mV / decade. After two weeks the enzyme activity of the biosensor still 75%.

碩士
國立雲林科技大學
電子與資訊工程研究所碩士班
91
In this thesis, the principle of the MOSFET was be used for the ion-sensitive field effect transistor (ISFET). The gate metal of the MOSFET was substituted for the insulator over the SiO2 , which must be sensitive for the H+ and OH- in the buffer solution. Reference electrode was used to supply the reference potential for the buffer solution. The threshold voltage (VT) of the ISFET will shift in the various pH buffer solutions. Hence, the pH value of the solution can be detected by the ISFET. Then we use gel entrapment to coating enzyme on sensing membrane as enzyme membrane, which by the enzyme immobilizing technology. The enzyme membrane can detect certain of the substance for the biochemical reaction（redox reaction）, use the ion sensitive field effect transistor to detect pH value of redox reaction which make the enzyme sensitive field effect transistor（EnFET）. In this thesis, we make a study of the gel entrapment to modify the urease on the ionic sensing membrane as the urea sensor.

碩士
逢甲大學
化學工程學所
99
A potentiometric urea biosensor has been prepared. It uses platinum as the sensing element and has urease as its biocomponent which catalyzes the hydrolysis of urea to ammonium and bicarbonate ions. Two methods, electropolymerization and covalent bond, have been used to immobilize the urease on the platinum electrode. According to the experimental results, the covalent bond enzyme electrode has made a better sensor. It showed that the sensor has good selectivity and high sensitivity, 21.31 mV/decade, at pH=6, when the electrode was made at 0.24 M EDOT and 100 mg/ml urease. The response is linear in the range of 10-5 ~ 10-1 M urea. After two weeks the enzyme activity of the biosensor still holds up to 80%.

碩士
逢甲大學
化學工程學所
100
In this study, a sensor device has been developed for detecting urea.3-aminopropyltrimethoxysilane, APTMS, has been coated on titanium dioxide and generated amine group on the surface by using self-assembled technology. Then the titanium dioxide was dipped into a urease solution, which had been activated by premixed EDC/NHS, to form amide bond between urease and amino group on the sensor electrode. Pt-C catalyst was added to the urease solution to make a stronger potential signal. The performances of the enzyme electrodes made from various different conditions were examined and compared. From the experimental results,urease concentration of 40 mg/ml with Pt-C catalyst makes the best enzyme electrode. At T = 20℃、pH = 6 environment, it shows that the sensor has high sensitivity 61.91 mV/decade, response time 95 ~ 195 s, and the linear range is 0.0005 ~ 0.01 M urea. After three weeks the enzyme activity of the biosensor still holds up to 67%.

博士
中原大學
電子工程研究所
93
Recently, pH sensors and biosensors play important roles in chemical assays and clinical analysis. For this reason, this thesis employs the tin oxide (SnO2) thin films, which are deposited on the indium tin oxide (ITO) glass using the sputtering method, to manufacture a pH electrode. Furthermore, the characterizations of SnO2 thin films are analyzed by using the electron spectroscopy for chemical analysis (ESCA), the X-ray diffraction (XRD) and the scanning probe microscopy (SPM), respectively. To prove the sensitivity of the pH electrode, the two-point calibration is employed. Moreover, the deposition conditions are controlled to design an effective pH electrode. According to experimental results, the deposition conditions are presented as follows: the sensing area is 4mm2, the O2 gas concentration is 20%(w/w), the reaction pressure is 20 mtorr, the substrate temperature is 150 ºC and the thin film thickness is 200nm. The pH sensitivity of the pH electrode is about 59.17 mV/pH, which is close to ideal Nernst slope at the room temperature. Using a reference electrode to serve a base potential is a serious drawback for a conventional potentiometric sensor, because it is difficult to design a miniature reference electrode for fabricating a micro sensor or a disposable sensor. To solve this problem, this thesis designs a differential pH sensor by using the conductive polymer technique. This differential pH sensor includes three parts, a SnO2 pH electrode, a polypyrrole pH electrode and a SnO2 pseudo-reference electrode. This differential pH sensor has a linear pH sensitivity of about 30.14mV/pH. Additionally, this thesis designs a solid-state urea biosensor based on the differential method and employs different immobilization methods for fabricating the urea biosensor. As indicated by experimental results, the solid-state urea biosensor has good sensing characteristics of between 5 mg/dl and 80 mg/dl. To design a measurement system for a solid-state urea biosensor, this thesis designs a readout circuit by using UMC 0.5μ 2P2M CMOS technology. The data acquisition card (PCI-6052) and program (LabVIEW6.0) are employed to obtain and analyze sensing signals. This thesis successfully designed a data acquisition system for the solid-state urea biosensor by using this technique.

碩士
華梵大學
電子工程學系碩士班
96
In this study, the extended-gate field effect transistors of the Sputter TiO2/ITO Glass, Sol-gel TiO2/ITO Glass and Sol-gel TiO2/ITO PET were applied to fabricate the durable ammonium ion selective electrodes. The potentiometric solid-state urea biosensor prepared by immobilization of urease directly onto the surface of an ammonium ion-selective electrode is described. The substrate of the ammonium ion-selective electrodes include TiO2 / ITO Glass, TiO2 / ITO PET and the enzyme was immobilized by entrapment method on a nonactin membrane incorporated carboxylated polyvinylchloride (PVC-COOH). The experimental results show that the optimized measurement environment of the ammonium ion selective electrode was in 0.5mM Tris /EDTA pH 7.5 and the best response curves can be gotten. The ammonium ion selective electrodes were measured in the ammonium buffer solution, concentration range from 10-7M ~ 1 M. The sensitivity is Sputter TiO2/ITO Glass about 46.31 mV/decade, Sol-gel TiO2/ITO Glass about 37.2 mV/decade, and Sol-gel TiO2/ITO PET 36.6 mV/decade in the linear range, respective. In addition, the ammonium ion selective electrode must emphasize its stability and reproducibility mechanism, the emphasis of the ion selective electrode also included the ion interference. The optimize measurement environment to fabricate a stable ammonium selective electrode was found. In experiment by each ten of the Sputter TiO2/ITO Glass, Sol-gel TiO2/ITO Glass and Sol-gel TiO2/ITO PET were observed in each ammonium ion concentration to study the response voltage of reproducibility. They showed Sputter TiO2/ITO Glass good sensitivity about 41~55 mV/decade, Sol-gel TiO2/ITO Glass sensitivity is about 35~45 mV/decade and Sol-gel TiO2/ITO PET sensitivity is 35~45 mV/decade. The corresponding average values are Sputter TiO2/ITO Glass about 49.8 mV/decade, Sol-gel TiO2/ITO Glass about 41.4 mV/decade and Sol-gel TiO2/ITO PET about 40.1 mV/decade. Keywords: Ammonium Ion Selective Electrode, Separated Extended-gate Field Effect Transistor, Titanium dioxide, reproducibility

博士
國立交通大學
電子研究所
98
In this thesis, a miniaturized urease biosensor constructed with an enzymy field-effect transistor (EnFET) and solid state reference systems were designed and developed. The EnFETs and the reference systems were developed based on the ion-sensitive FET (ISFET) technology. The ISFETs based biosensors have the advantages of rapid response, small size, high input-impedance and low output-impedance as well as the applicability of semiconductor and integrated-circuit technologies. The ISFET, which is a MOSFET with the gate connection separated in the form of a reference gate immersed in aqueous solution which is contact with the sensing layer above gate oxide. It is working based on the approach of electrochemical measurement of pH. With incorporating the entrapment immobilization technology, the biological or ion-insensitive materials can be attached on the ISFETs and transform the functionalities to be EnFETs or reference FETs (REFETs). Entrapment was a popular method to immobilize the various biological materials, such as urease, glucose and protein, with ISFETs. This method needs supporting matrixes provided by polymers with resistant to chemical attack and low interference to the materials entrapped. In our study, the NafionTM was found to be suitable candidate as supporting material. To develop a miniaturized ISFET based biosensor, three programs were executed. Firstly, the ZrO2-gated ISFET was fabricated and characterized. The optimal post annealing process was determined to be 600 , 30 mins. with N2 gas. The fabricated ISFET demonstrated good performances of high sensitivity, linearity, low drift and hysteresis. Secondly, the immobilization method was developed. The Nafion was utilized as supporting matrix, which entrapped ion-insensitive polymers, to produce REFET. Meanawhile, the EnFET was fabricated with similar approach of immobilizing urease in Nafion. Finally, for the miniaturization purpose, the reference systems, such as solid-state reference electrode (SRE) and reference FET (REFET) with quasi-reference electrode (QRE), were integrated with the sensors in the on-chip level. With differential measurements, the biosensors demonstrated comparable detecting performances.

碩士
長庚大學
電子工程學系
101
We successfully integrate extended-gate field-effect-transistor (EGFET) sensor into microfluidic chip and use it to measure concentrations of glucose, urea, and protein. Magnetic powder-containing enzyme-carrying alginate microgel was used to carry and immobilize glucose oxidase enzyme and urease on the sensor surface . We inject the alginate microgel to the micro channel, and use magnet to make it immobilize on EGFET sensing area and then enzyme will react with solution. In our study, we successfully detected pH, glucose, and urea. Otherwise we use 120 nm magnetic beads link antibody to catch the protein, and use DNA labeling technique, which have negative electron to improve signal. After the immuno-reaction was done, then we use magnet to immobilize the magnetic beads on sensing area to measure the concentration of protein. The smallest concentration of protein we can detect is 12.5ng/mL. We measure the chip selectivity for hydrogen ionwith sodium ions, potassium ions, and calcium ions. Experimental result shows that the sodium ions have the interference for hydrogen ion, which is about 0.03~0.07 pH variation . The sensitivity of pH is 37.45 mV/pH, and linearity is 99.39 %. The sensitivity of glucose detection is 7 mV/mM, and linearity is 99.62 %. The sensitivity of urea detection is 8.01mV/mM, and linearity is 98.09 %.

碩士
東海大學
化學工程與材料工程學系
97
In this study, urea biosensors were fabricated by the immobilization of urease on OMC. The effects of fabricated methods on the sensing characteristics of urea biosensor were investigated. Urea biosensor was used to detect the heavy metal ions due to the inhibition of enzymatic activity. OMC was prepared using a one-step synthesis method as the supports of enzyme. The surface area of OMC was found about 853 m2g-1. The major pore size of OMC was about 9.2 nm. The pore volume of OMC was about 1.37 m3g-1. The Nafion®/OMC/PANI-Nafion®/Au/Al2O3 sensors prepared by electrochemical polymerization and casting were used to detect the ammonium ion (NH4+). The three linear relationships between sensing current and the concentration of NH4+ were found in the range of 0.05~0.1、0.1~1 and 5～100 mM with the sensitivities of 5400、390 and 21.9 µA mM-1 cm-2, respectively. The detecting limit was found to be 0.05 mM. Based on the Nafion/urease/OMC/PANI-Nafion/Au/Al2O3 as the sensing electrode the concentration of urea could be measured by monitoring the level of ammonium ion formed in the enzymatic reaction of urea. The maximum net cathodic peak current was obtained to be 417 μA in pH 6.88 phosphate buffer solution(PBS) when the loading of urease and sensing temperature were fixed at 2.12 U and 25 ℃, respectively. The maximum sensitivity of the urea biosensor was obtained to be 3595 µA mM-1 cm-2 with the sensing limit of 0.005 mM Using Nafion/urease(2.12 U)/OMC/PANI-Nafion/Au/Al2O3 as the sensing electrode for the 5 ppm of Hg2+,it was found that the enzymatic activity was diminished about 58%. The sensitivity and the sensing limit to detect Hg2+ based on the same electrodes were obtained to be 5400 µA ppm-1 cm-2 and 0.005 ppm for the concentration of Hg2+ in the ranges of 0.01～0.1 ppm. OMC was also treated with acid to improve the hydrophilism by increasing carboxyl group using sulfuric acid/nitric acid mixture of volume ratio of 3 to 1. The surface area of OMC decreased from 853 to 431 m2g-1 by increasing the time of acid treatment from 0 to 60 min. The pore structure was destroyed by acid treatment in low pressure, especially. The storage efficiency was found to be the best for the Nafion/urease(2.12U)/OMC/PANI-Nafion/Au/Al2O3 biosensor prepared by immobilizing urease using impregnation casting in low pressure ,and OMC treated with acid for 15 mins.

碩士
國立雲林科技大學
電子工程系
106
In this thesis, two kinds of metal oxide were proposed as martrix for flexible arrayed urea biosensor. The metal oxide films were Nickel Oxide (NiO) and Titanium dioxide (TiO2), respectively. The radio frequency sputtering system deposits the sensing film, and the screen printing technology were used to prepare the conductive arrayed wires and the reference electrode, and the epoxy is to encapsulate flexible arrayed urea biosensor. However, the covalent binding method is used to immobilize the enzyme between the matrix of the urea biosensor, and the preparation of the urea biosensors were completed. Afterwards, the sensing films of nickel oxide and titanium dioxide were modified by using graphene oxide and magnetic beads to improve its properties. The basically sensing properties of the two kinds of matrix biosensors were measured, and response time, interference and detection limit were also measured. However, the urea biosenosrs were integrated into the microfluidic measurement system and wireless real-time sensing system to measure the sensing properties of the urea biosensor under dynamic conditions, and it achieved remote monitoring. In addition, the feasibility of TiO2 matrix for the development of glucose sensors were discussed. Finally, we compared the literatures with the urea biosensors and glucose sensor in this thesis.

The use of a conductive polypyrrole urea biosensor for the detection of urea in blood plasma is investigated.Urease was incorporated into a polypyrrole film by galvanostatic polymerisation. The presence of urea was verified, and the activity of the enzyme in the polypyrrole film was confirmed. The inherent electroactive properties of the polypyrrole-urease film has enabled the production of a flow injection amperometric biosensor for the reliable determination of urea. Greater sensitivity and stability was achieved when a pulsed amperometric detection system was implemented. The analysis of urea in human blood plasma by potentiometry, amperometry and pulsed amperometry was achieved with the assistance of an anion exchange separation prior to the electrochemical detection of urea. A polypyrrole-sulfite oxidase film was developed for use in an amperometric biosensor for sulfite determination. The response of the biosensor to sulfate was linear from 0 to 80 mg/L and the minimum detectable amount was 5 mg/L. Useful interferants in sulfite determination such as ascorbic acid, sodium nitrate and sodium sulfate did not respond to the biosensor. The excellent reproducibility of the sulfite response provides the basis for the construction of a disposable or renewable biosensor for sulfite determination. The analysis of sulfite in wine and beer was accomplished and no pretreatment was required.
Doctor of Philosophy (PhD)

博士
東海大學
化學工程學系
94
Urea and uric acid are the important indicators for the kidney diseases and clinic diagnosis. In this study, preparing urea and uric acid biosensors based on various polyaniline (PANI) conducting composite film/Au and iridium-modified carbon (Ir-C)/C/Au electrodes were carried out, respectively. And the properties of sensing electrodes and sensing characteristics were investigated. Ammonium ion (NH4+) is a non-electroactive specie. And it is the major product from catalyzing urea by enzymatic reaction. Consequently, the detection of NH4+ could be used to quantify the urea. Therefore, the preparation of the various NH4+-selective sensing electrodes based on the PANI-Nafion, PANI-PSSMA(I), PANI-PSSMA(II), PANI-PSSMA(III), nano-structural PANI-PSSMA(IV) and nano-structural PANI-Nafion on the Au were employed as NH4+-sensing electrodes. The sensing properties for NH4+ were also obtained in this study. The sensitivity and detecting limit of 100.4 A mM-1 and 0.025 mM for NH4+, respectively, were found by using the PANI(cycle no.=5)-Nafion(casting 4 l (2 wt%))/Au as the working electrode. The NH4+-sensitive electrode based on nano-structural PANI-Nafion(casting 8 l (1 wt%))/Au was also employed. The sensitivity of 836.39 A mM-1 and detecting limit of 0.005 mM were found, respectively. And there are four kinds of PANI-poly(styrenesulfonate-co-maleic acid, sodium type) (PSSMA) to be fabricated in NH4+ sensing electrodes. The highest sensitivity of 126.2 A mM-1 was obtained within the NH4+ concentration range of 0 ~ 1.0 mM based on nano-structural PANI-PSSMA(16 l (0.5 wt%))(IV)/Au electrode at 25C. Urea biosensor based on PANI(cycle no.=5)-Nafion(casting 8 l (1 wt%))/Au and nano-structural PANI(current density=80 A cm-2, 30 min)-Nafion(casting 8 l (1 wt%))/Au were fabricated in this study. The highest sensitivity of 87.26 A mM-1 and detecting limit of 5 M were found by using Nafion (urease, 160 U)/nano-structural PANI-Nafion/Au as working electrode. Also, cross linked urease (320 U) onto the nano-structural PANI-PSSMA(IV) by glutaraldehyde (GA) as cross-linker was used for sensing urea. The sensitivity of 52.02 A mM-1 was obtained in this study. The sensitivity of 36.71 A mM-1 and response time (t90) between 18.4 and 25 s were found for sensing H2O2 based on Ir(20 wt%)-C/C/Au at 37C. And the interferences caused by ascorbic acid (AA) and glucose could be minimized. Cross linked uricase (16 U) on the Ir(20 wt%)-C/C/Au formed uricase/Ir(20 wt%)-C/C/Au UA-sensing electrode. The sensitivity of 23.32 A mM-1 was obtained in pH 7 PBS at 37C. And the sensitivity of 14.03 A mM-1 for sensing UA was obtained when the minimum enzyme loading of 2 U was cast on Ir(20 wt%)-C/C/Au The UA sensor base on Ir(5 wt%)-C was employed in this work. The oxidative potential of 0.255 V (vs. Ag/AgCl) for AA by using differential pulse voltammetric (DPV) method was higher than the oxidative potential for UA. Therefore, the minimized interference by AA was demonstrated at the operating potential of 0.2 V. Using Ir(5 wt%)-C as UA-sensitive electrode, the sensitivity of 1.08 A mM-1 was found in pH 8 PBS at 37C. Furthermore, the Ir(5 wt%)-C electrode was employed to monitor UA in the serum and plasma. The sensing results were shown the Ir(5 wt%)-C could be used to sense UA directly in human serum and plasma, and the interference cased by other species in the blood was insignificant.