Yalan Liu,Jiao Li,Gang Chang,Ruizhi Zhu,Hanping He,Xiuhua Zhang,Shengfu Wang
Electrochemical sensors have been highly developed and play an important role in the early diagnosis of different diseases. In this work, a simple and rapid electrochemical method was developed for the quantitative detection of a trinucleotide repeat (TNR) sequence d(CAG)n based on magnetic beads and screen-printed carbon electrodes. Their combination greatly simplified the operation process. The intensity of the electrochemical signal was linearly correlated against the concentration of the TNR sequence d(CAG)n in the range from 100 pM to 1 μM, with a limit of detection as low as 24 pM. Furthermore, the number of repeats of the TNR sequence d(CAG)n could be detected and also showed a good linear relationship. The proposed method provides a promising rapid and simple method for the detection of a CAG TNR sequence for point-of-care testing in clinical applications.
Jiao Li,Yalan Liu,Xiaoqian Zhu,Gang Chang,Hanping He,Xiuhua Zhang,Shengfu Wang
Electrochemical sensors now play an important role in analysis and detection of nucleic acids. In this work, we present a novel double-signal technique for electrochemically measuring the sequence and length of the d(CAG)n repeat. The double-signal technique used an electrochemical molecular beacon (a hairpin DNA labeled with ferrocene), which was directly modified on the surface of a gold electrode, while a reporter probe (a DNA sequence labeled with horseradish peroxidase) was hybridized to the target DNA. First a simple single-signal sensor was characterized in which d(CAG)n repeats were detected using a short reporter DNA strand labeled with horseradish peroxidase. To obtain a reliable signal that was dependent on repeat number, a double-signal biosensor was created in which the single strand capture DNA in single-signal sensor was replaced by an electrochemical molecular beacon labeled with ferrocene. When the hairpin DNA hybridized to the target–reporter DNA complex, it opened, resulting in a decreased ferrocene current. Both electrochemical biosensors exhibited high selectivity and sensitivity with low detection limits of 0.21 and 0.15 pM, respectively, for the detection of d(CAG)n repeats. The double-signal sensor was more accurate for the determination of repeat length, which was measured from the ratio of signals for HRP and ferrocene (H/F). A linear relationship was found between H/F and the number of repeats (n), H/F = 0.1398n + 9.89788, with a correlation coefficient of 0.974. Only 10 nM of target DNA was required for measurements based on the value of H/F in the double-signal technique. These results indicated that this new double-signal electrochemical sensor provided a reliable method for the analysis of CAG trinucleotide repeats.
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