Determination of Cadmium Ions Based on Electrochemical DNA Biosensors in Rat Tissues

A highly sensitive electrochemical biosensor was fabricated for Cd2+ determination based on a dsDNA modified carbon paste electrode (CPE) and brilliant green (BG) indicator. The binding of Cd2+ on the modified dsDNA could result in the destabilization of the double helix structure of DNA, which was detected by the oxidation of a DNA hybridization indicator BG on the electrode surface. The reduction current of BG on the modified electrode increased significantly with the presence of Cd2+. Based on such electrochemical response, this electrode was further used determine the concentration of Cd2+ with a linear range from 0.05 x10(-9) to 1.2 x10(-9) mol/L and a limit of detection of 0.1 x10(-12) mol/L. The portable, low-cost modified electrode showed good sensitivity, selectivity, and stability. The method developed in this study was also applied to the direct determination of Cd2+ in rat tissue samples with satisfactory results. This work reveals that the dsDNA-modified CPE is a promising tool for the food detection and animal diagnosis.