An electrochemical biosensor with integrated microheater to improve the sensitivity of electrochemical nucleic acid biosensors

Electrochemical impedance spectroscopy (EIS) is often used for biomolecular detection based on the interaction of a molecule with a receptor functionalised electrode surface and consequent impedance change. Though its performance is well established, there is still a need for improved sensitivity and specificity, especially when attempting to detect nucleic acids from clinical samples with minimal amplification steps. Localised heating is a potential approach for improving nucleic hybridisation rates and reducing non-specific interactions, and thereby producing high sensitivity and selectivity [1-3]. The aim of the study was therefore to develop a microheater surrounding Au thin film electrodes, an integrated hybrid chip, for detecting genes of Mycobacterium tuberculosis with enhanced sensitivity. The performance of the integrated hybrid chip was determined using the changes in the charge transfer resistance (Rct) upon DNA hybridisation using probe sequences for Mycobacterium tuberculosis. Heat transfer within the system was simulated by using COMSOL Multiphysics as a mathematical modelling tool. When a temperature of 50 °C was applied to the microheater during DNA hybridisation steps, Rct values (which were indicative of DNA-DNA hybridisation) increased 236% and 90% as opposed to off-chip non-heated experiments and off-chip heated experiments. It is concluded from these observations that the microheater indeed can significantly improve the performance of the nucleic acid hybridisation assay and paves the way for the development of highly- sensitive and specific integrated label-free biosensors