Research On The Applications Of Electrochemiluminesence Biosensing Technique By Use Of Tris(Bipyridine)Ruthenium(Ⅱ)-β-cyclodextrin

Electrochemiluminescence (ECL) is generated by the electrochemical reaction. To be more specific, the electrochemical reaction generates the intermediates and plenty of energy, which leads to the formation of excitation state. Then, it causes the emission of light when it returns into the ground state. ECL technique possesses of diverse advantages, like good detection sensitivity, low backgroundand excellent controllability. As a result, it has been widely applied into the determination of biomolecule or disease diagnosis. There are various ECL systems, such as hydrazides compounds system (e.g. luminol), peroxide oxalate system, quantum dots system and Ru(bpy)32+or its derivatives system. One of the most commom ECL system is Ru(bpy)32+or its derivatives system without question. Actually, Ru(bpy)32+or its derivatives could be used as label and applied into the determination of target biomolecule by association with ECL technique.Host-guest recognition describes the special structural force between two or more molecules or ions, which is not caused by covalent bond. Instead, it could begenerated by one or more of the following forces:hydrogen bond,π-π stacking, electrostatic interaction, Van der Waals force, hydrophobic (hydrophilic) effectln the process of host-guest recognition, organic macro molecules or ligands are generally regarded as "Host". Meanwhile, smaller molecules or ions are regarded as "guest". Actually, host-guest recognition is indeed common in supramolecular chemistry research. In most cases, host-guest recognition could be applied into the switch of conformation, the construction of sensors for targets determination, the remove of hazards from environment, or even the delivery of drugs in clinical field.Cyclodextrin consists of a hydrophobic interior and a hydrophilic exterior, which enables the hydrophobic compound to be hosted in the cyclodextrin ring. Certainly, as a vital and common host, cyclodextrin could recognize guest molecules via various forms of non-covalent bond and then play key role in the construction of diverse sensors. If cyclodextrin is modified by metal or its complex, it would turn into metallocyclodextrin compound. By combination with the redox and photoactive property of metal or its complex, metallocyclodextrin compound is preferred to be used into the design of new sensors.Herein, the ECL-active property of tris(bipyridine)ruthenium(Ⅱ)-β-cyclodextrin (tris(bpyRu)-p-CD) and its host-guest recognition with aptamer are fully discussed. Based on the above characteristics, a novel ECL aptasensing technique is successfully constructed and realizes the ultrasensitive determination of thrombin and adenosine triphosphate (ATP) respectively. It means such a novel ECL aptasensing technique could be utilized to the determination of target proteins (like thrombin) and small biomolecules (like ATP) as well. According to the widespread application value of the proposed aptasensing technique, it is of significance for further research.This paper is composed of the following three chapters.Chapter One:PrefaceThe development situation of ECL sensing technique is described in this chapter. Both the principle and characteristics of different ECL systems are discussed respectively, including hydrazides compounds system, peroxide oxalate system, quantum dots system and R.u(bpy)32+or its derivatives system. Hereinto, Ru(bpy)32+or its derivatives system is emphatically introduced. Afterwards, applications of ECL in biosensing field are listed and classified into DNA sensors, immunsensors and small biomolecule sensors. Furthermore, this chapter illustrates the concept of host-guest recognition and introduces its application in biosensing technique, containing small molecule determination, drug delivery and the removal of hazards, which indicates the application value of host-guest recognition. A general introduction of metallocyclodextrin compounds is also presented. Eventually, this chapter states the purpose or significance of the research.Chapter Two:An ultrasensitive electrochemiluminescence aptasensor based on tris(bpyRu)-β-CD for the purpose of thrombin determinationThis chapter focuses on the construction of ultrasensitive ECL biosensing technique, which is esstentially based on the highly ECL-active property of tris(bpyRu)-P-CD and its recognition with thrombin aptamer. It is worthwhile to mention that the excellent ECL-active property would promote the sensitivity of the proposed aptasensor. Meanwhile, the recognition between tris(bpyRu)-β-CD and thrombin aptamer could cut out the procedures of ECL signal labeling. Thus, the principle of the aptasensor is illustrated as following:First, the thrombin aptamer should be modified onto the glassy carbon electrode. In the absence of thrombin,tris(bpyRu)-β-CD would be attached onto the aptamer-modified electrode because of host-guest recognition, and then performs strong ECL signal In the presence of thrombin, aptamer would prefer to react with thrombin rather than the host-guest recognition with tris(bpyRu)-β-CD. Thus, less tris(bpyRu)-P-CD could exist on the surface of the electrode and then leads to the decrease of ECL signal intensity. Therefore, in this protocol, the concentration of thrombin could be monitored by the decrease of ECL intensity.Besides, the detection limit of the proposed aptasensor achieves at0.1pM. It draws a conclusion that such novel ECL biosensing technique offer a creative route for thrombin or protein determination, which is simple-operated and ultrasensitive.Chapter three:A novel electrochemiluminescence ATP aptasensor by use of tris(bpyRu)-β-CDIn this chapter, a novel ECL aptasensor is successfully constructed for the sensitive determination of ATP. The core of the proposed aptasensor is to make full use of tris(bpyRu)-P-CD, both its high ECL-active property and the recognition capability with guest molecule (ATP aptamer). The principle for determination could be illustrated as following:The ATP aptamer is previously modified onto the electrode via coupling reaction. After recognition with tris(bpyRu)-P-CD, the modified electrode could be detected as strong ECL signal. While, in the presence of thrombin, the thrombin/aptamer bio-complex would be easily formed to restrict the host-guest recognition between tris(bpyRu)-P-CD and aptamer, which results in the obvious decrease of ECL signal intensity. Hence, ATP could be monitored by the proposed ECL aptasensor according to the above mechanism. Under optimal conditions, the detection limit could be0.01nM.Therefore, this novel biosensing technique based on tris(bpyRu)-β-CD could be widely applied into the determination of small biomolecule.