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Study On The High Sensitive, High Specific Electrochemical Biosensors Based On Nanoparticles And Their Applications

Posted on:2009-09-27Degree:MasterType:Thesis
Country:ChinaCandidate:W J FengFull Text:PDF
GTID:2178360245473850Subject:Analytical Chemistry
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Deoxyribonucleic acid (DNA) is the hereditary material in humans and almost all other organisms. The information in DNA is stored as a code. The order, or sequence, of these bases determines the information available for building and maintaining an organism.The detection of specific DNA sequence in human body, viral and bacteria nucleic acid is playing a more and more important role in disease diagnose, food pollution, legal medical examination and environment detection. Especially the detection of genetic mutations at the molecular level opens up the possibility of performing reliable diagnostics even before any symptom of a disease appears.Proteins are fundamental components of human body, and they are also an important part of life science. They involved in every day activities of human. Protein quantities analyses is a vital part of protein study, and thus is quite meaningful for human nutriology, disease diagnosis, drug, and genetically modified food and clinical analysis.The development of life science is calling for more sensitive, stable and convenient DNA and protein analyses methods.The goal of the present study is to design and optimize new electrochemical biosensors with high sensitivity and selectivity. This paper combines the excellent characteristics of nanoparticles, base-complementary and the specific recognition of protein. The high sensitivity of electrochemical device coupled to their compatibility with modern micro-fabrication technologies, portability, low cost, minimal power requirements, and independence of sample turbidity, made them excellent candidates for DNA and protein detection and also it would broaden the research field of post-genetic time. The dissertation includes four parts:Chapter 1 IntroductionIn the beginning of this dissertation, the basic composition of a DNA biosensor and its classification were systematically reviewed, especially the design of a DNA electrochemical biosensor was introduced, together with the application and development of DNA biosensor. Secondly, we introduced the concept of the aptamer, emphatically reviewed the operational principle, classification, application and development trends of aptamer biosensor. Thirdly, nanoparticles were introduced, especially the application of gold nanoparticles and magnetic nanoparticles in the biosensor was presented. At last, the purpose and the significance of the dissertation were pointed out.Chapter 2 An Amplified electrochemical aptasensor for thrombin based on the enrichment of gold nanoparticles through the hybridization with the complementary oligonucleotideAn amplified electrochemical biosensor for thrombin based on the enrichment of the gold nanoparticles through the hybridization with the complementary oligonucleotide was presented. Through the specific recognition for thrombin, a sandwich format of magnetic nanoparticle-aptamerI / thrombin / gold nanoparticle-aptamerII was fabricated. And the signal amplification was further implemented by the enrichment of gold nanoparticles through the hybridization with the gold labeled complementary oligonucleotide, the resulting hybridization is capable of realizing more gold nanoparticle markers attaching for one target protein, thrombin, and hence offer a remarkable amplification of detecting thrombin. A significant sensitivity enhancement was obtained for detection of thrombin with the signal amplification. This new strategy allows the detection of the target protein down to the 4.52×10-15 mol//L. The relative standard deviation of eight replicate determinations of 7.47×10-14 mol/L thrombin was 3.0%.Chapter 3 A new amplification strategy for ultrasensitive electrochemical aptasensor with network-like thiocyanuric acid/gold nanoparticlesThiocyanuric acid is a star-like molecular. It can form network-like structure with gold nanoparticles due to its three mercapto. An ultrasensitive and highly specific electrochemical detection for thrombin based on gold nanoparticles and thiocyanuric acid is presented. For this proposed aptasensor, aptamer I was immobilized on the magnetic nanoparticles, aptamer II was labeled with gold nanoparticles. Through the specific recognition for thrombin, a sandwich format of magnetic nanoparticle /thrombin / gold nanoparticle was fabricated, and the signal amplification was further implemented by forming network-like thiocyanuric acid /gold nanoparticles. A significant sensitivity enhancement had been obtained, and the detection limit was down to 7.82 aM. The presence of other proteins such as BSA and lysozyme did not affect the detection of thrombin, which indicates a high specificity of thrombin detection could be achieved. This electrochemical detection is expected to have wide applications in protein monitoring and disease diagnosis.Chapter 4 An ultrasensitive electrochemical biosensor for detection of p53 sequence based on the aggregation of gold nanoparticlesA new aptasensor has been developed for the detection of human tumor suppression p53 gene. Two DNA sequences were designed, and the combined sequences are complementary to that of the target p53 sequence, one was immobilized on the magnetic nanoparticles for capturing the target p53 sequence, the other one is labeled with gold nanoparticles as probe, and the sandwich format was formed for detecting the p53 sequences. The ultrasensitive detection was achieved by the aggregation of gold nanoparticles with introducing thiocyanuric acid into the system, and the detection limit could go down to 2.24×10-17 mol/L. To further improve the specificity of the method, We used stem-loop capture probe. The specificity increased to 85.52%.The mutant type p53 DNA sequence could be obviously distinguished from the wide type p53 DNA sequence.
Keywords/Search Tags:gold nanoparticles, magnetic nanoparticles, DNA, aptamer, thrombin, electrochemical biosensor, aptasensor
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