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, formerlyshielded 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 hostguest recognition-based electrochemical sensor has been able to detect as low as picomolar DNA target with excellent differentiation ability for even single mismatch.