Electrochemical detection of DNA hybridization based on the probe labeled with carbon-nanotubes loaded with silver nanoparticles

A sensitive electrochemical method for the detection of DNA hybridization based on the probe labeled with multiwall carbon-nanotubes (MWNTs) loaded with silver nanoparticles (Ag-MWNTs) has been developed. MWNTs were electroless-plated with a large number of silver nanoparticles to form Ag-MWNTs. Probe single strand DNA (ss-DNA) with a thiol group at the Y-terminal labeled with Ag-MWNTs by self-assembled monolayer (SAM) technique was employed as an electrochemical probe. Target ss-DNA with a thiol group was immobilized on a gold electrode by SAM technique, and then hybridized with the electrochemical probe. Binding events were monitored by differential pulse voltammetric (DPV) signal of silver nanoparticles. The signal difference permitted to distinguish the match of two perfectly complementary DNA strands from the near perfect match where just three base pairs were mismatched. There was a linear relation between the peak current at + 120 mV (vs. SCE) and complementary target ss-DNA concentration over the range from 3.1 x 10(-14) to 1.0 x 10(-11) mol/L with a detection limit of 10 fmol/L of complementary target ss-DNA. The proposed method has been successfully applied to detection of the DNA sequence related to cystic fibrosis. This work demonstrated that the MWNTs loaded with silver nanoparticles offers a great promising approach for sensitive detection of DNA hybridization.