A Triode-like Enzyme-free Catalytic Circuit with Junction Fuel

Abstract

Target detection circuits have been previously designed, which are propelled by conventional PCR, isothermal amplification and strand-displacement reaction. These detection circuits obtain the target signal via the replication of the target strand, the aggregation of the signal particles or the branch migration. Here we constructed a triode-like enzyme-free catalyst strand-displacement circuit for target DNA detection. The target strand triggered the reaction and released the fluorescence signal strand circularly through branch migration. However, the main challenge of strand-displacement reaction is the signal leakage. Therefore, we designed a double strand structure “junction fuel”, which was used to increase the binding energy across the displacement process. Ultimately, the leakage of the system obtained stable inhabitation due to the junction fuel strand. The limit of detection of the system was as low as 0.11 nmol/L and the gain of the system was as high as 28-fold(the concentration of target was 50 nmol/L). Furthermore, the process of the system was visualized vividly in the reaction curve through the kinetic simulation implemented, which suggests that the combination of the kinetic simulation and the experiment exhibits a promising prospect towards the use of strand-displacement circuit in analytical, diagnostic application and synthetic biology.