Tetrahedral DNA probe coupling with hybridization chain reaction for competitive thrombin aptasensor

A novel competitive aptasensor for thrombin detection is developed by using a tetrahedral DNA (T-DNA) probe and hybridization chain reaction (HCR) signal amplification. Sulfur and nitrogen co-doped reduced graphene oxide (SN-rGO) is firstly prepared by a simple reflux method and used for supporting substrate of biosensor. Then, T-DNA probe is modified on the electrode by Au-S bond and a competition is happened between target thrombin and the complementary DNA (cDNA) of aptamer. The aptamer binding to thrombin forms an aptamer-target conjugate and make the cDNA remained, and subsequently hybridizes with the vertical domain of T-DNA. Finally, the cDNAs trigger HCR, which results in a great current response by the catalysis of horseradish peroxidase to the hydrogen peroxide + hydroquinone system. For thrombin detection, the proposed biosensor shows a wide linearity range of 10–13–10−8M and a low detection limit of 11.6fM (S/N = 3), which is hopeful to apply in biotechnology and clinical diagnosis. •Sulfur and nitrogen co-doped reduced graphene oxide is prepared and used for supporting substrate.•A tetrahedral DNA nanostructure is used to improve the density and orientation of probe at the electrode surface.•Hybridization chain reaction is used for signal amplification.•The aptasensor shows wide linear range of 10–13–10−8M and low detection limit of 11.6fM.