Highly sensitive electrochemical detection of sequence-specific DNA of 35S promoter of cauliflower mosaic virus gene using CdSe quantum dots and gold nanoparticles

Cadmium selenide (CdSe) quantum dots modified with ethylenediamine were synthesized under hydrothermal conditions, and labeled onto the probe DNA owing to the electrostatic interaction between the amino group and the negatively charged phosphate skeleton of the DNA molecule. The surface of a chitosan-entrapped carbon paste electrode was modified with gold nanoparticles. The target DNA was immobilized on the gold nanoparticle membrane electrode and hybridized with the probe DNA labeled with CdSe. Then, CdSe was dissolved by the HNO3 solution. The target DNA was detected by differential pulse anodic stripping voltammetry of cadmium. Sequence-specific DNA of the 35S promoter of cauliflower mosaic virus gene was successfully determined with a dynamic detection range from 5.0 x 10(-12) to 5.0 x 10(-7) molaEuro cent L-1, with a detection limit of 6.5 x 10(-13) molaEuro cent L-1. Complementary DNA could be recognized by this method with good selectivity over non-complementary DNA and 2-base mismatched DNA.