Immobilization-Free Electrochemical DNA Sensor based on signal cascade amplification strategy.

The development of convenient and efficient strategies without using complex nanomaterials or enzymes for signal amplification is very important for bioanalytical applications. Herein, a novel electrochemical DNA sensor was developed by harnessing the signal amplification efficiency of catalytic hairpin assembly (CHA) and bran-new signal marker tetraferrocene. The prepared sensor had both ends of the probe H2 labeled with tetraferrocene, the both ends has a large number of unhybridized T bases, which causes tetraferrocene to move closer to the electrode surface, generating high-efficiency amplification signal. In the presence of target DNA, it induced strand exchange reactions promoting the formation of double-stranded DNA and recycling of target DNA. Under optimal conditions, the sensor showed good linear correlation between the peak currents and logarithm of target DNA concentrations (ranging from 0.1 fM to 0.3125 pM) with a detection limit of 0.06 fM, which is obtained by triple signal-to-noise ratio. Additionally, the prepared sensor possesses excellent selectivity, reproducibility and stability, demonstrating efficient and stable DNA detection methodology. This article is protected by copyright. All rights reserved.