Electrochemical Biosensor for Polycyclic Organic Compounds Screening Based on a Methylene Blue-incorporated DNA Polyion Complex Modified Electrode.

A reagent-less electrochemical DNA biosensor for rapid non-electroactive polycyclic organic compounds (POCs) screening and detection was proposed. In this method, methylene blue (MB) was incorporated into DNA/chitosan polyion complex membrane and then modified onto a glassy carbon electrode (GCE). The electrochemical analysis for the prepared DNA-MB/chitosan/GCE showed that the modified electrode exhibited high electrochemical activity and stability. The addition of tetracycline hydrochloride (TC), a model analyte of non-electroactive POCs, resulted in an obvious peak current decrease in DNA-MB/chitosan/GCE, and this electrochemical response was affected by the DNA type and MB/DNA ratio in the modified electrodes. Ultraviolet-visible (UV-Vis) absorption spectroscopy was utilized to furthermore investigate the interaction between TC and DNA-MB/chitosan/GCE. As a result, a competitive interaction and displacement effect between TC and the intercalated MB was proposed. In our condition, the prepared DNA-MB/chitosan/GCE showed high sensitivity to POCs and had almost no response to common interferences. Besides, the good stability and reproducibility of the prepared electrode made it suitable for practical use.