| 题名 | 基于新型分子识别机制的电位型传感器技术研究 |
| 作者 | 李龙1,2 |
| 学位类别 | 博士 |
| 答辩日期 | 2016-05-30 |
| 授予单位 | 中国科学院研究生院 |
| 授予地点 | 北京 |
| 导师 | 秦伟 |
| 关键词 | 电位分析 potentiometry 聚合物膜电极 polymeric membrane electrodes 分子识别 molecular recognition 共价作用 covalent interaction 配位作用 coordination interaction 氢键 hydrogen bond 自由基反应 free radical polymerization |
| 学位专业 | 环境科学 |
| 中文摘要 | 分子识别是化学及生物传感得以实现的重要过程，传统的离子选择性电极依赖离子载体实现对目标离子的高选择性检测。自上世纪六十年代开始，得益于生物化学及超分子化学的发展，多种高效的离子载体被发现、合成并用于构建聚合物膜电位型传感器。虽然上世纪九十年代低检出限离子选择性电极的发现进一步推动了该领域的发展，但是最近一二十年关于新型离子载体（尤其是阴离子载体）的报道较少。这一方面是由于该领域没有及时将超分子化学的研究成果引入造成的，另一方面是因为发展阴离子及中性分子的载体/识别体确有难度。本论文从新型的分子识别机制出发，分别利用共价键、配位键、氢键及特殊的化学反应发展了几类新型的电位型传感器： 1. 基于硼酸寡聚反应的电位型多元醇传感器。葡萄糖氧化酶的性质不稳定，因而酶基传感器的长期稳定性欠佳。葡萄糖本身不能引起电位信号，并且缺乏能产生电位信号的高选择性葡萄糖识别体，所以目前并没有关于高选择性电位型葡萄糖传感器的报道。通过二硼酸与葡萄糖之间的可逆共价作用，两种分子可以以首尾相接的形式形成线状或环状寡聚阴离子。利用该寡聚阴离子与聚阳离子鱼精蛋白之间的静电作用及鱼精蛋白本身的电位响应，可实现葡萄糖的检测。其它单糖因为只有一对顺式二醇结构，不会和二硼酸形成寡聚阴离子，因而不会干扰葡萄糖的检测。该方法可在没有特异性识别体的情况下实现对葡萄糖的检测，并可用于植物多酚的检测。 2. 基于竞争分析的电位型磷酸根传感器。可逆共价作用只发生在特定的官能团之间，因而上述方法有一定的局限性。考虑到配位作用键能较强而且存在于大多数阴离子与金属离子之间，我们利用配位作用构建了竞争型磷酸根传感器。以Cu2+-BPMP（双（2,6 -二（2 -吡啶基甲基）氨基甲基）-4-甲基苯酚）或Zn2+-BPMP为分子识别体，以邻巯基苯酚为指示分子，利用指示分子氧化反应过程中产生的电位信号，我们实现了磷酸根的选择性检测。通过电位滴定实验与竞争实验测定了磷酸根、指示分子与分子识别体的结合常数，进一步验证了检测原理。其它阴离子不能将指示分子从分子识别体中取代下来，因而不干扰磷酸根检测。该方法可用于矿泉水、唾液、尿液等样品中磷酸根含量的检测。 3. 基于阳离子及中性锑烷的电位型氟离子传感器。氟离子的水化能很强，需要发展强亲和力的载体，将其从水相有效地萃取到膜相。以电中性及阳离子锑烷为氟离子载体，通过优化离子交换剂的种类及用量，构建了高选择性氟离子电极。研究表明，这类电极对氟离子的选择性明显优于只掺杂有阴离子交换剂的聚合物膜电极。采用双层膜夹心法测定了离子载体与各种离子之间的结合常数，该结合常数反映了电极的选择性系数。基于阳离子及电中性锑烷的氟离子电极具有优良的响应性能，可用于水溶液中氟离子浓度的测试，有一定的潜在应用价值。 4. 电中性硫酚的电位响应及其在电化学传感中的应用。对于大部分电中性分子来说，很难利用共价键及配位键发展与其相对应的分子识别体。经典的聚合物膜电极理论认为只有带电物质才能在聚合物膜上引起电位响应。研究表明，电中性的表面活性剂、苯酚及硼酸等可以间接方式改变膜表面的电荷分布进而引起电位响应。但是，这类电中性物质能够引起电位响应的报道较少。我们发现，电中性苯硫酚可在氢键作用下在阴离子交换剂掺杂的聚合物膜上引起电位响应。通过均相的紫外滴定实验及两相萃取实验，我们研究了苯硫酚与离子交换剂在均相及两相溶液中结合性质，据此推测了它的电位响应机理。该电极可作为一种简单易行的手段检测环境污染物苯硫酚。另外，利用苯硫酚氧化反应过程中的信号变化，可发展高灵敏的电位型传感平台用于多种物质的电化学检测。 5. 免标记、聚合放大型自由基反应传感器。以上几种传感方法针对的都是物理化学性质比较稳定的目标物，但是对于化学性质不稳定的目标物如自由基，很难发展一种与之相对应的分子识别体。利用自由基反应聚合乙烯型及芳香型单体的性质及高灵敏聚离子电极，我们发展了针对自由基反应的电位型传感平台。我们首先考察了经RAFT反应及FRP反应产生的聚离子及其对应的单体在聚合物膜电极上的响应性能，研究发现聚离子电极对聚合物的灵敏度显著高于对单体的灵敏度。利用葡萄糖氧化酶消除溶液中的氧气，以自由基反应聚合阳离子或阴离子单体，我们实现了对自由基引发剂（如辣根过氧化物酶、G-四联体/核酸酶、Fenton反应）及猝灭剂（过氧化氢酶）的检测。基于类似的原理，该传感平台可实现多种反应及目标物的高灵敏电位检测。 |
| 英文摘要 | Molecular recognition is of great importance for chemical and biological sensing of specific targets. Highly selective measurements can be achieved using traditional ion-selective electrodes by doping the membranes with specific ionphores. Since 1960s, with the development of biochemistry and supramolecular chemistry, many macromolecular and small molecular receptors have been discovered/synthesized and used as efficient ionphores for potentiometric sensing. Although the discovery of low-detection-limit ion-selective electrodes in 1990s has further promoted the development of this technique, very limited new ionphores (especially for anion ionphores) have been reported in the past two decades. The main reasons may be that the findings in supramolecular chemistry have not been used to ion-selective electrodes and the intrinsic difficulties of constructing new ionphores/receptors for anions/neutral species. Based on novel molecular recognition mechanisms originating from covalent, coordination and hydrogen bonding interactions and free radical polymerization reactions, potentiometric sensing platforms for several kinds of targets have been developed. 1. Potentiometric detection of polyols based on oligomerization with a diboronic acid. The instabilities originating from the intrinsic variable features of the enzymes may prevent the enzyme-based sensors from being widely utilized. Moreover, polymeric membrane electrodes for highly specific and enzyme free glucose detection have rarely been reported, probably due to the inability of glucose to induce potential response directly and unavailability of potentiometric reporters to specially recognize glucose and transduce the target-binding events. Based on the specific covalent reactions, the diboronic acid condenses with glucose via its two cis-diol units to form cyclic or linear oligomeric polyanions, which can interact electrostatically with protamine, thus efficiently decreasing the potentiometric response of protamine on a polycation-sensitive membrane electrode. Although fructose, galactose and mannose show even higher binding affinities to the diboronic acid as compared to glucose, these monosaccharides with only one cis-diol unit cannot oligomerize with the receptor, which efficiently excludes the interferences from the glucose’s stereoisomers. In this study, high selective glucose detection can be achieved when a specific receptor is unavailable. This sensing strategy can also be used for the detection of polyphenols from plants. 2. Potentiometric sensing of aqueous phosphate by competition assays. Although covalent interactions are promising for highly affinitive recognition, specific functional groups are always required, thus restricting their wide applications. Considering that coordination interactions are very powerful and exist between most aninons and metal ions, we propose a potentiometric sensing platform for phosphate by competition assays. Using Zn2+-BPMP or Cu2+-BPMP as receptor and o-mercaptophenol as indicator to initiate the signal by the oxidation of the indicator, potentiometric sensing of aqueous phosphate can be achieved. To give more insights into the detection mechanism, the binding constants between the phosphate/indicator and the receptors have been determinated by potentiometric titration experiments and competition assays. Interferences from other anions are excluded in this study because of their inabilities to displace the indicator from the receptors. This method has been successfully used for detection of phosphate levels in mineral water and human urine and saliva samples, and the results are in good accordance with those obtained by the standard method. 3. Cationic and netrual antimony based ionphores for potentiometric sensing of fluoride. Fluoride is one of the most hydrated anions which is in the front of the Hoffmeister series, and highly affinitive ionophores are needed to extract the aqueous fluoride into the polymeric membrane. Using cationic and netrual antimony compands as ionophores, highly selective fluoride sensors have been developed by optimizing the compotents (such as the types and amounts of the ion-exchangers) of the polymeric membranes. Anti-Hoffmeister series behaviors can be observed for most of the polymeric membranes doped with cationic and netrual antimony compands, which are significantly different from those of the TDMACl doped membranes. The complex formation constants between the anions and the ionphores in the solvent polymeric membranes have been determinated with segmented sandwich membranes. It is shown that the selectivity coefficients of the polymeric membrane electrodes reflect the complex formation constants. The proposed sensors can be used for aqueous fluoride detection with a high sensitivity, and are promising in real word applications. 4. Potential responses to neutral thiophenols of polymeric membrane electrodes and their applications in potentiometric biosensing. It is difficult to develop receptors for electrically neutral species by using covalent and coordination bonds mentioned above. According to the traditional theory of phase boundary potential, only charged species can induce potential responses on the polymeric membranes. It has been reported recently that electrically neutral species such as surfactants, phenols and boronic acids can show significant potential responses on the ion exchanger-doped polymeric membranes by disturbing the charge separation layer at the oil/water interface. However, electrically neutral species that can induce potential responses are rather limited. In this work, the unexpected potential responses to electrically neutral thiophenols of polymeric membranes with the assistant of hydrogen bonds are shown. The complexations between thiophenols and quaternary ammonium salts in homogeneous and heterogeneous organic solutions have been studied by titration and extraction experiments, respectively. The potential response mechanism has been investigated. The potential responses to thiophenols of the polymeric membranes provide a simple way to differentiate thiophenols from biologically important bioactive aliphatic thiols. By using thiophenols as reducing substrates, a potentiometric sensing platform for oxidases and their related reactions has been developed. 5. Label-free polymerization amplified potentiometric sensing platform for radical reactions. The methods developed in the above chapters are suitable for targets with stable physical and chemical properties. It should be noted that it is difficult to design receptors for chemically active species such as radicals. In this work, selective and sensitive sensors for these species are proposed using specific reactions. Taking advantage of the “polymerization for amplification” strategy by using enzymes or other radical initiators to produce polymers via free radical polymerization of cationic/anionic and aromatic monomers and using the polyion sensitive membrane electrodes as transducers, a highly sensitive and label-free potentiometric sensing platform for free radical reactions can be developed. By carefully examing the response characteristics of the ion-exchanger doped polymeric membrane electrodes to polycation/polyanion and their corresponding monomers, it has been found that the membrane electrodes are at least two orders of magnitude more sensitive to the polymers generated from reversible addition-fragmentation chain transfer polymerization (RAFT) and free radical polymerization (FRP) reactions than to the monomers. Thus, highly sensitive polyion detection can be achieved even in the presence of large concentrations of background monomers. We demonstrate here the use of this platform to detect low concentrations of radical initiators (such as horseradish peroxidase, G-quadruplex, as well as trace concentrations of Fe2+ and Cu2+) and quencher (such as catalase). It is believed that DNA/aptamer based biosensing can also be achieved using this platform with similar sensitivities. |
| 语种 | 中文 |
| 学科主题 | 环境科学 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.yic.ac.cn/handle/133337/17535]  |
| 专题 | 中科院烟台海岸带研究所知识产出_学位论文 |
| 作者单位 | 1.中国科学院烟台海岸带研究所 2.中国科学院大学 |
| 推荐引用方式 GB/T 7714 | 李龙. 基于新型分子识别机制的电位型传感器技术研究[D]. 北京. 中国科学院研究生院. 2016. |
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