A novel signal-on electrochemical DNA sensor based on target catalyzed hairpin assembly strategy

We describe a novel signal-on electrochemical DNA (E-DNA) sensing platform based on target-catalyzed hairpin assembly. The thiolated modified molecular beacon 1 (MB1) was first immobilized onto the Au electrode (GE) surface and then target DNA hybridized to the MB1, the opened MB1 assembled with the ferrocene (Fc)-labeled molecular beacon 2 to displace the target DNA, which became available for the next cycle of MB1-target hybridization. Moreover, Fc was confined close to the GE surface for efficient electron transfer, resulting in a current signal. Eventually, each target strand went through many cycles, resulting in numerous Fcs confining close to the GE, which leaded to the current of Fc dramatically increase. The observed signal gain was sufficient to achieve a demonstrated detection limit of 0.74 fM, with a wide linear dynamic range from 10(-15) to 10(-10)M and discriminated mismatched DNA from perfect matched target DNA with a high selectivity. Thus, the proposed E-DNA sensor would have a wide range of sensor applications because it is enzyme-free and simple to perform.