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  • 學位論文

化學修飾電極之製備以及其在生化感測器之應用

Preparation of Chemically Modified Electrodes and Their Applications to Biochemical Sensors

指導教授 : 何國川

摘要


在本論文中,我們選擇不同的化學或生物分子,包含碘酸根、多巴胺(DA)、糖化血紅素(HbA1c)以及亞硝酸鹽,然後利用不同的材料製備化學修飾電極感測之。 碘酸根常添加於食鹽中以防止甲狀腺腫大。我們首次製備一導電高分子聚二氧乙烯噻吩(PEDOT)與氧化還原媒子核黃素腺嘌呤二核苷酸(FAD)複合薄膜以修飾玻璃碳電極(GCE)。此修飾電極定名為GCE/PEDOT-FAD。循環伏安法(CV)以及電化學式石英震盪微天秤(EQCM)實驗顯示,FAD在PEDOT聚合的過程中摻雜至其中。製備修飾電極的最佳鍍膜圈數決定為9圈。我們利用定電位法感測碘酸根,GCE/PEDOT-FAD的靈敏度為0.78 μA μM-1 cm-2,線性範圍為4-140 μM,而偵測下限(LOD)為0.16 μM。與文獻中單獨利用FAD感測碘酸根所得的結果比較,本研究將PEDOT與FAD結合改善了感測器的靈敏度與偵測下限。我們最後將此感測器應用於偵測鹽產品中的碘酸根。 DA為一重要的神經傳導物質,它的分泌異常將導致一些疾病如巴金森氏症及杭亭頓氏舞蹈症。我們利硼摻雜奈米碳管(BCNTs)修飾網印碳電極(SPCE)。BCNTs是利用一常壓的碳熱反應合成,其中氨氣(在氬氣的氛圍中)作為蝕刻氣體在多壁奈米碳管(MWCNT)中產生缺陷,三氧化二硼作為硼源。我們利用0.5wt.%的Nafion®溶液將奈米碳管分散以修飾SPCE。我們首度探討硼摻雜量與BCNT催化活性之間的關聯性,發現BCNT (B 2.1 at.%)對於DA有最佳的催化效果。旋轉盤電極分析顯示,摻雜2.1 at.%的硼於MWCNT中分別提升它的電活性面積(Ae)及標準速率常數(k0)約13%。我們利用BCNT (B 2.1 at.%)修飾的SPCE 感測DA,相較於利用CV,以微分脈衝伏安法(DPV)進行感測能夠得到較高的靈敏(35.65 μA cm-2 μM-1)與較低的偵測下限(0.017 μM)。干擾研究方面,我們探討抗壞血酸以及尿酸對於DA感測的影響。 HbA1c是評估長期糖尿病監控情形的重要指標。我們選擇網印金電極(SPGE)為電極基材,然後以滴覆的方式將Nafion®修飾其上當作選擇性物質。二茂鐵硼酸(FcBA)則用來辨識HbA1c並且提供氧化還原電流訊號。我們發現修飾Nafion®能夠防止血紅素(Hb)吸附於SPGE上,主要的原因為Nafion®與Hb之間的電性排斥。實驗上決定Nafion®的最佳修飾層數為3層。我們以人類全血進行真實樣品測試。我們也探討與HbA1c結合對於FcBA氧化還原峰電流造成的影響,並且證實與HbA1c結合是造成FcBA氧化還原峰電流下降的主因。此外,由於還原峰電流的下降量較氧化峰電流明顯,我們推論HbA1c與氧化態的FcBA(FcBA+)之間有較強的作用力。 亞硝酸鹽是評估泌尿道感染的重要指標。為了臨床應用的方便性,我們嘗試製備電化學式感測器以偵測不稀釋尿液中的亞硝酸鹽。我們利用導電高分子聚3,4-(2,2-二乙基丙烯)二氧基噻吩(PProDOT-Et2)修飾SPGE以提升它的性能表現。由於亞硝酸鹽不存在健康人的尿液中,我們將亞硝酸鹽添加於尿液樣品中進行偵測。我們發現利用CV在不稀釋的尿液中最低可偵測的濃度約為250 μM,此值較試紙呈色方法的最低可偵測濃度(20 μM)來得高。我們將利用不同的電極修飾物質以及不同的電化學感測方法改善感測器的性能表現。

並列摘要


In this dissertation, different chemical or biological molecules, including iodate, dopamine (DA), glycated hemoglobin (HbA1c), and nitrite were selected as the targets, and different materials were used to prepare the chemically modified electrodes (CMEs) for sensing them. Iodate is often added in table salts to prevent goiter. A composite film composed of the conducting polymer, poly(3,4-ethylenedioxythiophene) (PEDOT) and the mediator, flavin adenine dinucleotide (FAD), was prepared for the first time for modifying the glassy carbon electrode (GCE). This modified electrode was designated as GCE/PEDOT-FAD. Cyclic voltammetry (CV) and electrochemical quartz crystal microbalance (EQCM) analyses revealed that FAD was doped into the PEDOT film during the electrodepositon process. The optimal cycle number for preparing the modified electrode was determined to be 9. The amperometric detection of iodate was performed; the GCE/PEDOT-FAD showed a sensitivity of 0.78 μA μM-1 cm-2, a linear range of 4-140 μM, and a limit of detection (LOD) of 0.16 μM for iodate. Compared with the results in the literature obtained by using single FAD for sensing iodate, it can be said that the combination of PEDOT with FAD significantly improved the sensitivity and LOD. Eventually, the GCE/PEDOT-FAD was applied to detect iodate in a salt product. DA is a vital neurotransmitter; its abnormal transmission has been associated with several neurological disorders such as Parkinson’s disease and Huntington’s chorea. Boron doped carbon nanotubes (BCNTs) were utilized for modifying the screen printed carbon electrode (SPCE). The BCNTs were synthesized by an atmospheric carbothermal reaction, in which ammonia (in argon atmosphere) was used as the etching gas to create defects in the multi-walled carbon nanotubes (MWCNT), and boron trioxide was used as the boron source. Each CNT sample was dispersed in 0.5 wt.% Nafion® solution. The relationship between the boron doped amount and the electrocatalytic activity of the BCNT was explored for the first time; it was found that the oxidation peak current of DA is the highest on the BCNT (B 2.1 at.%) modified SPCE. Rotating disk electrode (RDE) analysis revealed that doping of 2.1 at.% boron into the MWCNT upgrades the electroactive surface area (Ae) and the standard rate constant (k0) by ca. 13%, respectively. DA sensing on the BCNT (B 2.1 at.%) modified SPCE was conducted; higher sensitivity (35.65 μA cm-2 μM-1) and lower LOD (0.017 μM) were obtained by using the differential pulse voltammetry (DPV), with respect to those obtained by using CV. The interfering effects of ascorbic acid and uric acid on DA sensing were also studied. HbA1c is an important index for assessing the long-term condition of diabetes monitoring. Screen printed gold electrode (SPGE) was chosen as the substrate, and Nafion® was dropped coated onto it as a selective material. Ferroceneboronic acid (FcBA) was utilized for recognizing HbA1c and providing the redox signal. Experimental results showed that the modification of Nafion® film effectively blocked the adsorption of hemoglobin (Hb) onto the SPGE; the main reason could be charge repulsion between Hb and Nafion®. The optimal layer of Nafion® film for modifying the SPGE was determined to be 3. Human whole blood was used for real sample test. The effect of HbA1c binding on the redox signal of FcBA was also investigated. It was verified that the binding with HbA1c is the main reason for causing the decrement of the redox signal. Furthermore, since the decrement of the reduction peak current is larger than that of the anodic peak current, it was deduced that HbA1c has stronger interaction with the oxidized FcBA (FcBA+). Nitrite is a significant index for assessing the urinary tract infection (UTI). For the convenience of clinical use, we tried to fabricate an electrochemical sensor to detect nitrite in the undiluted human urine samples. The conducting polymer, poly(3,4-(2’,2’-diethylpropylene)dioxythiophene) (PProDOT-Et2), was utilized to modify the SPGE to enhance its sensor performance. Since nitrite does not exist in the urine from healthy persons, nitrite was spiked into the urine samples for detection. It was found that the lowest concentration of nitrite that can be detect in the human urine by using the CV method is 250 μM, which is higher than the value can be achieved by the test paper coloring method, 20 μM. Different materials and different electrochemical sensing methods will be used to improve the sensor performance.

參考文獻


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