A New Electrochemical Sensor for DNA Detection Based on Au Nanoparticles Surface-Modified with <i>β</i>-Cyclodextrins

Abstract

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 NH2 group was immobilized on multi-walled carbon nanotube modified glassy carbon electrode (MCNTs/GCE) surface, and the Au nanoparticles surface-modified with b-cyclodextrins (CD-AuNPs) 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 CD-AuNPs 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 b-cyclodextrin (b-CD) and dabcyl, thus the target hybridization event could be sensitively transduced to electrochemical signal provided by CD-AuNPs. 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.