A Host‐Guest‐Recognition‐Based Electrochemical Sensor for Sequence‐Specific DNA Detection

We herein constructed a sensor that converts target DNA hybridization‐induced conformational transformation of the probe DNA to electrochemical response based on host‐guest recognition and nanoparticle label. In the sensor, the hairpin DNA terminal‐labeled with 4‐((4‐(dimethylamino)phenyl)azo)benzoic acid (dabcyl) and thiol group was immobilized on Au electrode surface as the probe DNA by Au‐S bond, and the CdS nanoparticles surface‐modified with β‐cyclodextrins (CdS‐CDs) were employed as electrochemical signal provider and host‐guest recognition element. Initially, the probe DNA immobilized on electrode kept the stem‐loop configuration, which shielded dabcyl from docking with the CdS‐CDs in solution due to the steric effect. After target hybridization, the probe DNA underwent a significant conformational change, which forced dabcyl away from the electrode. As a result, formerly‐shielded dabcyl became accessible to host‐guest recognition between β‐cyclodextrin (β‐CD) and dabcyl, thus the target hybridization event could be sensitively transduced to electrochemical signal provided by CdS‐CDs. This host‐guest recognition‐based electrochemical sensor has been able to detect as low as picomolar DNA target with excellent differentiation ability for even single mismatch.