New Types Of Bipyridine-Ruthenium CyclodextrinsSupramolecular Compounds: Synthesis, Properties And Studies On Their Applications In DNA ECL Biosensors

Living things was created after millions of years of evolution of nature, and living functions are performed by numerous supramolecular systems. Supramolecular chemistry is a science that complicated and ordered molecular aggregates are formed by intermolecular interactions. Supramolecular chemistry has been developed a newly emerging molecular information chemistry, in which modification, transmission and processing in supramolecular level are achieved by information storage on structure characteristic in molecular level and molecular recognition on specific interactions. Supramolecular chemistry is a highly interdisciplinary field of science covering chemistry and multi-subjects such as physics, materials, information, environmental science. It plays an important role in the studies and application of life sciences. In supramolecular chemistry many phenomena, for instance, life regulation by highly specific recognition between smaller molecules and macromolecules, communication (electron transfer, energy transfer, substance transport and chemical transformation) and acceptor-donor within a living organism are covered.Cyclodextrins are one of the most important host molecules in supramolecular chemistry, and they can bind many molecules such as organic, inorganic and biological molecules and form the inclusion complexes. Based on these special characteristic, cyclodextrins supramolecular chemistry has been developed and an extensive focus of researchers'attention. Studies on cyclodextrins have been developed from the mechanism of host-guest recognition to the applications for analytical chemistry, pharmaceuticals preparation, environment detecting, biosensors. Metallocyclodextrins resulted by attaching photoactive metal centers onto cyclodextrin are more appropriative for the design of supramolecular devices and sensors owing to the properties of host-guest recognition of cyclodextrins and luminescent properties of metals like ruthenium. Therefore, more and more attention is focused on the research of metallocyclodextrins supramolecular compounds However, up to now, Most of metallocyclodextrins prepared contain only a signal metal center. It is noteworthy that polynuclear metal complexes, especially polypyridine ruthenium, because of their special multielectron redox processes and high photovoltaic or photocatalytic efficiency stemming from multiple chromophores to a single molecule have been successfully applied in the construction of photovoltaic molecular devices, fluorescence switches and biomolecules multi-label.Electrochemiluminescence (ECL), especially ECL techniques based on Ru(bpy)32+ have been extensively applied in clinical diagnosticians, for example, Ru(bpy)3 included with magnetic bead has been applied in the detection of clinical immune and tumour labels. For the valuable applications of ECL detection technique based on Ru(bpy)32+ in biosensors, many researchers devoted to the studies of new types of Ru(bpy)32+-biosensors with a view to improve the sensitivity of ECL biosensor under the condition that activity of biomolecules are maintained on ECL active labeling, for multi-bipyridine ruthenium labeling and nanoparticles included with Ru(bpy)32+. However, this kind of labeling methods increase the quantity of Ru(bpy)32+ labeled on biomolecules, but the disadvantage for the activity of biomolecules decreased and instabilities are observed. Therefore, it has been the target of researcher that the biological activity can be maintained in the process of the labeling ECL active compounds and ECL sensitivity can be improved.Herein, on the basis of the preparation of existing cyclodextrins derivatives, mono-, di-and tri-substituted anilineβ-cyclodextrin derivatives have been synthesized, based on which, six metallocyclodextrins in two categories: multi-ruthenium and muti-cyclodextrins bipyridine ruthenium cyclodextrins supramolecular compounds. The studies on the luminescent characteristic of these bipyridine ruthenium cyclodextrins supramolecular compounds showed that multi-ruthenium compounds exhibited very strong fluorescence and ECL intensity, more importantly, they showed highly efficient fluorescence and ECL quenching based on the host-guest recognition for some specific guest molecules. Furthermore, based on the efficient ECL quenching of multi-ruthenium metallocyclodextrins for the guest dabcyl, ECL DNA biosensors were constructed, and this strategy of the sensor has the advantage that it avoids the complicated processes of luminescent active compouns modification and biolabeling and it can achieve directly attaching ECL signal reporter onto the biomolecules and a high sensibility as well, which will make it have great potential in ECL biosensors.The innovation of the thesis is listed as follows:1) A series of new type of metallocyclodextrins supramolecular compounds especially multi-ruthenium have been firstly synthesized, in which six metallocyclodextrins in two categories compounds are included:multi-ruthenium centers and multi-cyclodextrins. Especially the multi-ruthenium centers metallocyclodextrins represents a new family of metallocyclodextrins.2) Studies on the applications of the metallocyclodextrins supramolecular compounds in ECL sensors have not been reported up till now. Herein, we firstly research the ECL properties and energy transfer mechanism of the synthesized in our thesis.3) ECL DNA biosensor based on bipyridine ruthenium cyclodextrins supramolecular compounds and host-guest recognition is a novel technique. The new strategy for biosensor in our thesis will improve the traditional methods of directly labeling Ru(bpy)32+on biomolecules. In this new strategy, ECL luminescent active compounds are introduced onto the biomolecules by host-guest recognition of cyclodextrins from the bipyridine ruthenium cyclodextrins supramolecular compounds, by which the indirect labeling of biomolecules is achieved. This method will make the biomolecules labeling simpler, low-cost and maintain biological activity. In addition, owing to the presence of multi-bipyridine ruthenium for multi-ruthenium metallocyclodextrins, multi-label on one site of biomolecules is accessible, which to some extent raise not only the efficiency of labeling process but also the insensibility of ECL biomolecules detection.The thesis consists of seven chapters. Chapter 1:PrefaceFirstly, we introduce the conception and background of supramolecular chemistry, in addition, we review the conception and development of the host-guest chemistry, supramolecular self-assembly, molecular electronic. Secondly, we introduce the development backgrounds of supramolecular chemistry, in which the classification and research status of cyclodextrins derivatives, the application of cyclodextrins in chemical sensors are highlighted. Lastly, we illustrate the conception, principle and application of DNA electrochemical sensor, besides, we introduce the principle and development status of ECL and classification research status of ECL biosensor. Based on the above introduction, we point out the purpose and signification of the thesis.Chapter 2:the synthesis of aniline substitutedβ-cyclodextrin derivativesBased on the important role of cyclodextrins derivatives in supramolecular chemistry focused on research of the host-guest recognition, we synthesize mono-, di-and tri-substituted aniline on the 6-position ofβ-cyclodextrin derivatives. In order to obtain the target compounds successfully, we give five synthetic strategies, and the results of research demonstrated that three of them are unsuccessful ones, and two of them are successful ones. For the successful strategies, one is an ideal route for the synthesis of multi-substitution on the 6-position ofβ-cyclodextrin, the other is the improvement for the route. By the improved route, we achieved the preparation of aniline substitutedβ-cyclodextrin derivative in two steps, though the mono-substitution derivative is obtained, the optimization of conditions about the route is under progress. These aniline multi-substitution ofβ-cyclodextrin derivatives will be applied in the preparation of electrochemical modified electrode and used as the important materials for the synthesis of bipyridine-ruthenium cyclodextrins supramolecular compounds.Chapter 3:The synthesis of new types of bipyridine-ruthenium cyclodextrins supramolecular compoundsBased on the development and research status of cyclodextrins and metallocyclodextrins and the synthesis of aniline multi-substitution ofβ-cyclodextrin derivatives, we synthesize a series of new types of bipyridine-ruthenium cyclodextrins supramolecular compounds. These metallocyclodextrins are classified into two catagories:the ones containing single cyclodextrin and multi-ruthenium centers and the ones containing single ruthenium center and multi-cyclodextrins, the former includes Ru-CD,2Ru-CD and 3Ru-CD, the latter includes Ru-2CD, Ru-3CD and Ru-6CD. The structures of these compounds are confirmed by NMR and Mass.Chapter 4:The studies of characteristic of new types of bipyridine-ruthenium cyclodextrins supramolecular compoundsIn order to explore the application of the synthesized new types of bipyridine-ruthenium cyclodextrins supramolecular compounds in the field of fluorescence and electrochemical sensor, in this chapter, we study the UV absorbance, fluorescence, electrochemistry and ECL properties of the metallocyclodextrins in two categories. The research results demonstrated that multi-ruthenium metallocyclodextrin exhibit highly strong fluorescence and ECL properties, which will give very important principle basis for the design of fluorescence sensors and electrochemical biosensors.Chapter 5:The fluorescence properties studies of new types of bipyridine-ruthenium cyclodextrins supramolecular compounds based on host-guest recognitionIn this chapter, we investigate the fluorescence quenching of the new types of bipyridine-ruthenium metallocyclodextrins based on the host-guest recognition of the three guest molecules Fc, Dab and MB in two categories. The research results show in presence of Dab and MB, both of the multi-ruthenium and multi-cyclodextrins metallocyclodextrins exhibit highly efficient fluorescence quenching, while for the guest Fc,3Ru-CD and Ru-6CD show more efficient fluorescence quenching properties. Chapter 6:The study of Aniline substitutedβ-cyclodextrin derivative modified electrodeIn this chapter, by diazotization, we modify the synthesized aniline substitutedβ-cyclodextrin derivative (MPA-β-CD) onto the glassy carbon electrode, and the modification is characterized by IR spectrum and electrochemical cyclic voltammetry. The research show that the modified electrode by electrochemical reduction diazotization has the characteristics such as simple operation, rapid reaction, easy control. By the (3-CD modified electrode, we investigate the host-guest recognition ofβ-CD for Fc, in which, quantities of Fc molecules are captured by the MPA-β-CD on the surface of the modified electrode. Therefore, MPA-β-CD modified electrode will have a great potential for the application of electrochemical sensor.Chapter 7: The studies of ECL DNA biosensors based on the host-guest recognition of new types of bipyridine-ruthenium cyclodextrins supramolecular compoundsBased on the ECL properties studies of new type of bipyridine-ruthenium cyclodextrins supramolecular compounds, as the multi-ruthenium metallocyclodextrins namely Ru-CD,2Ru-CD and 3Ru-CD the research focus, we investigated the ECL behavior effects of Dab on the three metallocyclodextrins. The results show 3Ru-CD exhibit highly efficient ECL quenching in presence of Dab, which is because the efficient electron or energy transfer stemming from the presence of multi-ruthenium centers. Based on the conclusion, we construct ECL DNA biosensors of 3Ru-CD for detecting the target DNA. The biosensor strategy based on the host-guest recognition of metallocyclodextrins achieve a quite low detecting limit, in addition, compared with the traditional ECL DNA biosensor, it avoids the complicated processes of biolabelling, at the same time, the direct detection in the solution has an advantage of simple operation over Ru(bpy)32+ modification on some substrates.