Investigations of the steric effect on electrochemical transduction in a quinone-based DNA sensor

Electrochemical biosensors for DNA hybridization are receiving increasing interest. A key point for their efficiency is to obtain a high signal level for low DNA concentration. This implies the design of an efficient transducing surface. Conducting polymers are interesting for this purpose but the great majority of conducting polymer-based electrodes present a signal decrease upon hybridization (a "signal-off" behavior), which impedes their response and makes them sensitive to false positive ones. The sensor described here presents a "signal-on" behavior, due to the use of a quinone group as the transducing agent. The specific aim of this work is to study the steric effect on transduction. To this end, the electrochemical response was monitored versus the DNA target length, for a constant DNA probe length. The results indicate that the current depends on the length of the double strand. A model which can explain the electrochemical behavior takes into account the steric hindrance of the ODN strands.