| Electrochemiluminescence (ECL) has received increasing attention in recent years, especially in the determination of organic or biochemical compounds and immune diagnostic field. As an analytical technique, ECL possesses some favorable advantages. First, it is repeatable due to the light-emitting process which is realized in ECL is in accurate controlling for synchronization and dimensional orientation with the electrochemical reaction on electrode surface. Second, the ECL detection is separated from the electrochemical excitation, it is beneficial for enhancement of signal/noise ratio therefore the sensitivity. Third, the ECL can be controlled by manipulating the applied potential and/or other electric parameters to realize selective detection. Forth, in ECL procedure, more than one of the reactive species is electrochemically produced in situ, therefore to avoid the problems of the use of some violent and instable chemicals. In addition, the ECL instrument is often simpler than many electrochemical or fluorescence instruments. Luminol, noticed as a typical strong chemiluminescence (CL) reagent, has also been widely researched for ECL application. However, to the general knowledge, the researches of CL and ECL of luminol have been limited in strong alkaline solution algate, and its ECL behavior in neutral medium has almost been ignored. With regard to the bioactive molecules, the neutral medium would be more suitable for keeping their original properties. For example, it is affirmed that neutral medium is of the most favorable condition for noctilucent systems because the organisms such as amino acid, protein in disadvantageous conditions would alter their qualities to induce wrong exhibitions in reactions. During the discussions between the colleagues around the world, most researchers declared that the ECL of luminol in neutral medium was too weak to be practically applied. That is to say, as a preferential opinion that the luminol-based ECL detection for biomolecules was suffered from the usual requirement of high pH condition, it is difficult to use it directly for the detection of important biological compounds at physiological pH.Due to the exceeding ECL sensitivity, expedience and inexpensiveness, the authors paid strong interest on luminol to attempt its feasibility for determination of biomolecules contained in bio-fluids with trace amount. The ECL detection of luminol in neutral medium is realized if there was proper intensifier presented. In the ECL system of luminol, the ECL intensity of luminol was enhanced obviously in the presence of nanosized Au and Pt particles which were synthesized by reduction methods and characterized by transmission electron microscope (TEM) method, and the sensitization was attributed to nanoparticle’s character. Organic molecules including chloramphenicol (CAP) and Cysteine also could enhance the ECL of luminol. Microemulsion and ionic liquid which have become hot topics in many fields for having several unique physical and chemical properties are enhancers for ECL of luminol, too. Experimental results showed that significant increases in ECL intensity of the luminol were observed when adding above-mentioned materials. The sensitization efficiency was always related to the content of the enhancers, which could be used to improve the sensitivity of determined method based on the ECL of luminol. The paper lucubrated the mechanisms of all these enhancers enhanced ECL of luminol in neutral and the weak alkaline media by other techniques. Based on the sensitization, some biomolecules were determined. For example, Vitamin C and melatonin could quench the ECL signals. The ECL luminous intensity linearly decreases with the concentration of quenchers, and the samples have been determined with satisfactory results. It should be a sensitive and reliable method for the determination of such biomolecules.As reported in this paper, the sensitization greatly improved the ECL performance of luminol in neutral and the weak alkaline media, part of which were related with the reactive oxygen species (ROSs) which could enhance the ECL intensity of luminol. The results indicated that whether the enhancers were dissolved in solutions or immobilized on the surface of conventional electrodes, stronger ECL intensity of luminol could be obtained. Enhanced ECL by ROSs helped to provide ground work for the detection of biomolecules for which would further enhance or quench the ECL signals. The powerful sensitization from ROSs related with organics and organisms were examined under selected conditions which were suitable for biochemical analysis. And the applications for biodetecting target related to superoxide dismutase (SOD), horseradish peroxidase (HRP), xanthine oxidase (XOD), uric acid (UA) and alanine aminotransferase (ALT) became true based on the progress. Different enzyme biosensors were fabricated according to enzymatic reactions. The ECL-based biosensor showed excellent character for some certain measurement. It can detect the lower concentration of samples due to the highly sensitivity of ECL and highly selectivity of enzyme. So, the studies on sensitization ECL of luminol not only extended the region of ECL research into the physiological category, but also established a basis for ECL research of biomaterials. The technique may provide new means in a variety of fields such as clinical diagnostics, immunological analysis and environmental monitoring due to its simplicity and high efficiency.Rapid detection, quantification and sequencing of deoxyribonucleic acid (DNA) are important tasks in the fields of biology, drug discovery, medical diagnostics, agriculture, as well as environmental science. In the thesis, we have reported the quenching effect of DNA on ECL of luminol and the further development of a DNA sensing device. The typical design of a DNA sensor involves the appropriate immobilization of the DNA molecules or introduction of an effective indicator or so called labeled probe. In this field, the nano-material modified electrodes are inherently ideal because of the enormous specific surface, which is highly susceptible to heterogeneous redox with surrounding environments. With the pre-functionalization by composite of carbon nano-tubes (CNTs) and Au nanoparticles (Au NPs), the sensor provides a novel and valuable label-free approach for DNA sensing. The results indicated that the ECL response was correlative with the presence of dsDNA. Based on the researches, the possible quenching mechanism of dsDNA for ECL of luminol has also been discussed. It might be resulted from the interaction of luminol with dsDNA, and the elimination of ROSs by dsDNA.Based on the ability of CAP to enhance the ECL signals, the above-mentioned DNA-biosensor was used for the study of interaction of DNA and CAP in a neutral aqueous solution in the thesis. The interaction of DNA and CAP had been examined in detail using ECL method, Ultraviolet-Visible Absorption Spectrum, fluorescence spectroscopy, cyclic voltammogram technique and the mechanism was proposed based on the experiments data. The method which was presented here could be act as a model leading to applications in DNA damage caused by other chemicals in clinical practice, medicine and basic research.The thesis reports an ECL sensing technique for label-free characterization of oligonucleotide complementation. Followed the pre-function for glassy carbon electrode by composite of Au NPs and CNTs, the sensor was constructed by immobilizing the probing oligonucleotide with ECL of luminol as sensing signal. Its availability for characterization of oligonucleotide hybridization and further potentiality for DNA detection were reported herein. The variational regression slope is distinguishable for complementation status of oligonucleotide hybridization. It was found that high degree of complementation caused efficient quenching for ECL of luminol. Furthermore, it was revealed that the response could be attributed to the interaction between luminol and oligo-strands, and also related to the reducing of ROSs. |
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