Preparation And Application Of DNA Biosensors Based On Gold And Magnetic Nanoparticles

Specific sequences DNA detection has become a most important research field due to its application in disease diagnosis, drug screening, epidemic prevention and environmental protection. DNA Biosensors could clearly analysis DNA sequences and have been developed rapidly in recent years because of its simple, rapid, inexpensive, high sensitivity and selectivity. In this paper, we used nanomaterial and light, electrochemical technology to research several sensitive DNA biosensors. Also we discussed their applications in actual sample tests. This dissertation includes three parts:Chapter I: In this chapter, we briefly introduced the DNA molecule and the composition, principle, type, application and research progress of the DNA biosensor.Chapter II: A sensitive electrochemical DNA biosensor was prepared based on mercaptoacetic acid / gold nanoparticles modified electrode. Gold nanoparticles were firstly electrodeposited on the surface of the gold electrode, and then the electrode was immersed in a solution of mercaptoacetic acid to form a self-assembled monolayer. Probe DNA (NH2-DNA) was covalently linked to the carboxyl group of MAA in the presence of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxyl-succinimide. Scanning electron microscopy and electrochemical impedance spectra were used to investigate the film assembly process. The DNA hybridization event was monitored by differential pulse voltammetry and adriamycin was used as the electrochemical indicator. Also the factors influencing the performance of the DNA hybridization were investigated in detail.Chapter III: In this study, we reported two sensitive fluorescent biosensors for detection of DNA hybridization based on Fe@Au and Fe₃O₄@Au nanoparticles. First, nanoparticles were synthesized using reverse micelle method and the size of nanoparticle was confirmed by transmission electron microscopy. Scanning electron microscopy was performed in order to elucidate the morphology of the nanoparticle. Then probe DNA with -SH at the 5′-phosphate end was covalently immobilized onto the surface of nanoparticle. The DNA hybridization event was detected by fluorescent method and methylene blue as fluorescent probe. In addition, this approach of DNA detection exhibited excellent selectivity, even for single-mismatched DNA detection.