Use of a chitosan–cadmium polymer as a redox hybridization indicator for CaMV35S promoter gene detection

A water-soluble chitosan-coordinated cadmium polymer was synthesized, and its recognition of single-stranded and double-stranded DNA was investigated. The electrochemical analysis in the homogeneous solutions revealed that the chitosan-coordinated cadmium polymer association with a single stranded DNA was 48 times greater than with double-stranded DNA due to the different interaction with the two kinds of DNA. The surface-based electrochemically absorbed chitosan-coordinated cadmium polymer molecules were easily removed from the double-stranded DNA-modified electrode via rinsing but could not be removed from a single-stranded DNA-modified electrode. Based on this fact, the polymer was utilized as a redox indicator for DNA hybridization detection, as the polymer was able to recognize complementary, noncomplementary, and base-mismatched sequences with a low background interference. The target DNA sequence was quantified from 5.0 × 10-9 to 5.0 × 10-7 M with a detection limit of 4.2 × 10-9 M. The polymerase c...