Electrochemiluminescence And Its Application In DNA Biosensors

Electrogenerated chemiluminescence (ECL), know as electrochemilumicescence, which combines chemiluminescence (CL) and electrochemistry. The CL reaction was initiated by an electrochemical reaction at electrode surface. Such an electro-initiation reaction introduces a large number of additional advantages, such as high sensitivity and selectivity, rapid and convenient operation and relatively simple instrumentation system. So ECL is becoming more and more important in many fields.Deoxyribonucleic Acid (DNA) is known as inherited substance in life body. The analysis of DNA sequence and DNA mutant detection play fundamental roles in the rapid development of molecular diagnostics and in the anticancer drug screening.Therefor many detection techniques of DNA sequence have been developed in recent years. These techniques mainly depend on the nucleic acid hybridization and their sensitivities are related to the specific activity of the label linked to the DNA probe. The degree of hybridization of probe to its complementary DNA sequence in sample is translated into a useful electric signal, which is a measurement of the amount of that specific sequence in the sample.In this dissertation we focused on the preparation of a new type of DNA probes which were labeled with ECL activated substances. Based on coupling with the DNA hybridization and immobilization techniques, we have developed new ECL methods for the determination of special DNA sequence. Compared with other methods the new methods are simple, rapid as well as sensitive and selective. The dissertation is composed of three chapters as followings:Chapter 1: Introduced the ECL and its application in analytical chemistry field, paid more attention to the types of ECL reaction and ECL sensors. Reviewed the DNA sensors, including their principles, advantage and disadvantage. At last pointed out the purpose of the dissertation.Chapter 2: Study on the ECL behaviors of two substances and establish their ECL analytical system.1 The catalytic reaction of ferrocenecarboxylic acid (FCA) to Luminol and hydrogen peroxide was investigated. It was found the Chemiluminescent intensity of Luminol with hydrogen peroxide can be greatly enhanced by electrochemically oxidizing of FCA at low potential in Tris buffer solution. Under optimal conditions the ECL intensity exhibits a good linear response with the concentration of FCA in the range of 5.0 10-9~2.0 10-4mol/L. The detection limit is 1.5 10-9mol/L.2 The electrogenerated chemiluminescence (ECL) behavior of oleanlic acid(OA) in neutral solution was studied. It has been found that oleanlic acid gives ECL emission at Pt electrode when the applied potentials were over 0.8 V (vs. Ag/AgCl). The ECL intensity was greatly influenced by the electrochemical parameters. The strongest ECL signal was observed in 1.0 mol/L KCL solution, whose pH is 7.0. And adding H2O2 could catalyze its signal. Under optimum conditions the ECL intensity has a linear relationship with the concentration of oleanlic acid in the range of 4.38xlO-7 ~ 4.38x10-5mol/L . The detection limit was 2.0xlO-7 mol L-1. The proposed ECL mechanism was discussed.Chapter 3: Preparation of new DNA-ECL probes and their applications to DNA assay1 FCA-DNA probe. This probe was made by convalent bound between carboxyl group of FCA and 5'-amino of oligonucleotide in the presence of a water-soluble carbodiimide. The hybridization reaction was conducted by immersing the ssDNA-immobilized electrode in FCA-DNA probe solution. The hybridization events were estimated by the ECL signals from FCA. The results showed that the FCA-DNA probe was able to recognize three-base mismatch sequence and formed dsDNA only with complementary sequence. The linear response to the complementary sequence is of 2 10-10~5 10-8 mol/L and the detection limit is 5.0 10-11 mol/L .2 Luminol-SiO2-DNA probe. Luminol-SiO2 nanoparticles were first synthesized by hydrolysis of tetraethoxysilane (TEOS) within a reverse microemulsion system. Particles in the size range 55 ~70...