The application of β-cyclodextrin derivative functionalized aligned carbon nanotubes for electrochemically DNA sensing via host-guest recognition.

We functionalized aligned carbon nanotubes (ACNTs) electrode with a new kind of β-cyclodextrin (β-CD) derivative through diazotization reaction. The resulting β-CD/ACNTs electrode was used to detect DNA hybridization in homogeneous solution based on host-guest recognition technology. In the sensing protocol, one special DNA probe was designed with a stem-loop structure and both ends modified, which we called dually labeled DNA probe (DLP). One end of the DLP was labeled with dabcyl as guest molecule for β-CD/ACNTs electrode capture, and the other end was labeled with a CdS nanoparticle as an electrochemical tag to indicate the occurrence of DNA hybridization. In the absence of the target DNA sequence, the DLP maintains its hairpin structure in solution phase and would not be captured and detected by the β-CD/ACNTs electrode. In the presence of the complementary target sequence, the conformational structure of the DLP was altered and a double-stranded DNA (dsDNA) molecule was formed by the hybridization of DLP and complementary DNA sequence. Consequently, the dsDNA was captured by the β-CD/ACNTs electrode owing to guest-host recognition between β-CD and dabcyl. The electrochemical signal from the CdS nanoparticle-dsDNA/β-CD/ACNTs was then measured. Under optimized detection conditions, the proposed method showed high sensitivity and selectivity with a detection limit of 5.0 × 10(-13) M for complementary DNA sequence.