Electrochemical Luminescent DNA Sensor Based on Polymerase-assisted Signal Amplification
Abstract A novel polymerase-based electrochemical luminescence (ECL) 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 probe DNA (CP) was immobilized on the surface of a magneto-controlled glassy carbon electrode via Au-S bond. After the addition of target mRNA, CP was opened and hybridized with mRNA to form double-stranded DNA (dsDNA). Then polymerase, primer chain (DNA1) and bases were added, which made the primer chain extend to replace the target mRNA. After one amplification cycle, the mRNA chain could open another hairpin in order to carry out next cycle of amplification. Finally, the ECL detection was carried out by adding DNA2 labeled thioglycolic acid-CdTe quantum dots. The amplification of the target mRNA by the addition of polymerase and the signal combined with the quantum dots label greatly improved the sensitivity of the sensor. The results showed that corresponding ECL signal had a good linear relationship with logarithm of target mRNA concentration in the range of 1 × 10−15 to 1 × 10−11 M, with a detection limit of 3.4 × 10−16 M (S/N = 3). Under the optimal conditions, the recoveries of mRNA spiked in human serum sample were from 97.2 % to 102.3 %. This sensor exhibited good selectivity, stability and reproducibility.