期刊
MICROCHIMICA ACTA
卷 180, 期 13-14, 页码 1271-1277出版社
SPRINGER WIEN
DOI: 10.1007/s00604-013-1044-1
关键词
Molecular beacon; Gold nanoparticles; Conjugates; Signal amplification; Electrochemical impedance spectra
资金
- National Natural Science Foundation of China [20675002]
We describe a highly sensitive and selective molecular beacon-based electrochemical impedance biosensor for the sequence-specific detection of DNA. DNA-capped conjugates between gold nanoparticles (Au-NPs) and streptavidin are used for signal amplification. The molecular beacon was labeled with a thiol at its 5' end and with biotin at its 3' end, and then immobilized on the surface of a bare gold electrode through the formation of Au-S bonds. Initially, the molecular beacon is present in the closed state, and this shields the biotin from being approached by streptavidin due to steric hindrance. In the presence of the target DNA, the target DNA molecules hybridize with the loop and cause a conformational change that moves the biotin away from the surface of the electrode. The biotin thereby becomes accessible for the reporter (the DNA-streptavidin capped Au-NPs), and this results in a distinct increase in electron transfer resistance. Under optimal conditions, the increase in resistance is linearly related to the logarithm of the concentration of complementary target DNA in the range from 1.0 fM to 0.1 mu M, with a detection limit of 0.35 fM (at an S/N of 3). This biosensor exhibits good selectivity, and acceptable stability and reproducibility.
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