A non-immobilizing electrochemical DNA sensing strategy with homogenous hybridization based on the host-guest recognition technique

In this paper, we report a new strategy for electrochemical DNA detection in homogeneous solution based on the host-guest molecule recognition technique. In this sensing protocol, a novel dually labeled DNA probe (DLP) in a stem-loop structure was employed, which was designed with dabcyl labeled at one end as a guest molecule, and with Au nanoparticle labeled at the other end as electrochemical tag to indicate the hybridization occurrence. One α-CD/MCNTs/GCE was used for capturing the DNA hybridization and electrochemical signal transduction. Before the hybridization, the DLP remained in the stem-loop structure, which forced the dabcyl molecular to be closed to the Au nanoparticle. Due to the steric effect of the Au nanoparticle, the dabcyl was prevented from conjugating with the α-CD on the electrode and resulting in that the DLP could not be captured by the electrode. After hybridized with the target DNA, the target-binding DLP caused the DLP's loop-stem structure opened and then the dabcyl molecule was easily entering the cavity of the α-CD modified electrode and resulting in that the DLP could be captured by the α-CD modified electrode and the capture efficiency was proportion with the concentration of the target DNA. Therefore, the target hybridization event can be sensitively transduced via detecting the electrochemical reduction current signal of AuCl₄^- of Au nanoparticles labeled at the DLP. Using this strategy, as low as 2.6×10^-10M DNA target had been detected with excellent differentiation ability for even single mismatch.