Electrochemical Luminescent DNA Sensor Based on Polymerase-assisted Signal Amplification

A novel polymerase. based electrochemiluminescence DNA sensor was constructed for messenger RNA (mRNA) detection by cyclic chain displacement polymerization, assisted by target mRNA cycle, and quantum dots signal amplification. Firstly, the mercapto. modified capture. type capture DNA (CP) was immobilized on the surface of a magneto. controlled glassy carbon electrode via Au-S bond. After adding the target mRNA, CP was opened and hybridized with mRNA to form dsDNA. After adding polymerase, primer chain (DNA1) and the base, the primer chain was extended to replace the target mRNA. After one cycle, the mRNA chain could open another hairpin in order to carry out next cycle of amplification. Finally, electrochemical luminescence detection was carried out by adding DNA2 labeled TGA-CdTe quantum dots. The amplification of the target mRNA by the addition of polymerase and the signal combined with the quantum dot mark improved the sensitivity of the sensor greatly. The result showed that the logarithm of target mRNA concentration had a good linear relationship with the corresponding ECL signal in the range of 1 x 10(-15) - 1 x 10(-11) mol/L, with the detection limit of 3.4 x 10(-16) mol/L(S/N = 3). Under the optimal conditions, the recoveries of mRNA spiked in human serum sample were 97.2% - 102.3%. This sensor exhibited good selectivity, stability and reproducibility.