Design and Fabrication of a Folding- and Dynamics-Based Electrochemical DNA Sensor on Indium Tin Oxide

The folding- and dynamics-based electrochemical biosensing platform has proven to be a very versatile sensing platform; it has been employed for detection of a wide range of analytes such as nucleic acids, small molecules, and proteins. One of the most well-studied sensors is the stem-loop electrochemical DNA (E-DNA) sensor. Traditionally, this sensor is fabricated via direct immobilization of thiolated DNA probes modified with a redox label such as methylene blue (MB) onto a polycrystalline gold electrode. Hybridization between the probe and target DNA leads to a change in both probe conformation and flexibility, altering the electron transfer kinetics between MB and the electrode, resulting in a large decrease in the MB current. Although polycrystalline gold is one of the most commonly used electrodes for this class of sensors, there are advantages in investigating alternative electrode substrates. In this study, we have for the first time demonstrated the fabrication of an E-DNA sensor on an indium tin oxide (ITO) electrode. We employed a new phosphonate self-assembled monolayer and potential-assisted “click” chemistry to attach the stem-loop DNA probes onto the ITO electrode. Despite the difference in the probe coverage, the E-DNA sensor fabricated using this approach was found to possess similar qualities as the sensor fabricated on a gold electrode. This sensor fabrication approach is versatile and can potentially be used with other sensors of this class, including the electrochemical aptamer-based and peptide-based sensors.