Abstract
In this work, a sensitive electrochemical DNA sensor based on avidin modified electrode and DNA-functionalized CdS nanoparticle (DFCP) was developed. The DNA-Functionalized CdS nanoparticle contained two kinds of DNA, one was hairpin probe DNA with a biotin at the 3’ terminal and a thiol at the 5’ terminal, the other is linearity signal DNA. Without hybridized with target DNA, the loop of hairpin impeded biotin linked with avidin on electrode. However, after target hybridization, hairpin was opened and biotin was recognized by avidin resulting in DNA-functionalized CdS nanoparticle was brought on electrode surface. Electrochemical signals of methylene blue (MB) bound to the signal DNA were measured by differential pulse voltammetry (DPV). Introduction By using this new method, we demonstrate that this prototype sensor has been able to detect as low as picomolar DNA targets with excellent differentiation ability for even single mismatches.
Highlights
Nucleic acids are one of the most fundamental molecules for all life forms, and as a results the specific nucleic acid sequence quantification is essential in biological and biomedical studies, such as medical diagnostics, gene expression analysis, and the detection of infectious diseases
We employed a stem-loop DNA probe dually labeled with HS and biotin at the 5ƍ- and the 3ƍ- end, respectively, which could be facilely immobilized at CdSnanoparticle surfaces via the Au-S bridge and hybridized with target DNA
The DNA-functionalized CdS nanoparticle (DFCP) remained in the stem-loop structure, which forced the biotin to be closed to the CdS nanoparticle
Summary
Nucleic acids are one of the most fundamental molecules for all life forms, and as a results the specific nucleic acid sequence quantification is essential in biological and biomedical studies, such as medical diagnostics, gene expression analysis, and the detection of infectious diseases. Many approaches have been successfully developed for the sequence-selective DNA hybridization examination, including fluorescence, electrochemical and colorimetric etc. We reported a non-immobilizing DNAsensor with hybridization occurred in one homogeneous solution that employed DNA-functionalized CdS nanoparticle (DFCP) and avidin modified electrode. We have developed a DNA-functionalized CdS nanoparticle, integrated DNA recognition; signal amplification and specific biotin- avdin link functional section, as probe for DNA detection and featured high sensitivity up to low pmtomolar. Afterwards, when avidin modified electrode was immersed in a solution after the hybridization event happened, the biotin of the DFCP could have attached to avidin on the electrode and was captured on the electrode. Taking advantage of amplification effects of the CdS nanoparticle and binding specificity of hairpin probe, this biosensor greatly simplifies the electrochemical detection method of DNA and displays higher specificity than the linear probe in DNA detection
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