Enzyme-free amplification for sensitive electrochemical detection of DNA via target-catalyzed hairpin assembly assisted current change

An isothermal, enzyme-free and sensitive method for electrochemical detection of DNA is proposed based on target catalyzed hairpin assembly and for signal amplification. Molecular beacon 1 (MB1) contains a ferrocene (Fc) tag, which was immobilized on the gold electrode as recognition probe to hybridize with target DNA. Then, molecular beacon 2 hybridized with the opened MB1, allowing the target to be displaced. The displaced target again triggered the next round of strand exchange reaction resulting in many Fc far away from the GE to achieve signal amplification for sensitive DNA detection. The current signal amplification strategy is relatively simple and inexpensive owing to avoid the use of any kind of enzyme or sophisticated equipment. It can achieve a sensitivity of 42 fM with a wide linear dynamic range from 10−13 to 10−9 M and discriminate mismatched DNA from perfect matched target DNA with a high selectivity. The proposed method showed excellent specificity, high sensitivity and low detection limit, and could be applied in analysis of real samples.