Design of a microheater to improve the sensitivity of electrochemical nucleic acid biosensors

Electrochemical impedance spectroscopy (EIS) is often used for biomolecule detection based on the hybridization of the molecule onto the functionalized 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. Localized heating is a potential approach for improving nucleic hybridization rates and reducing non-specific hybridization, and thereby producing high sensitivity and selectivity. The aim of the study was therefore to develop a microheater surrounding microeledtrodes, an integrated hybrid chip, sensing the genes of Mycobacterium tuberculosis with much higher sensitivity. The performance of the integrated hybrid chip was determined using the changes in the charge transfer resistance (RCT) upon DNA hybridization using probe sequences for Mycobacterium tuberculosis. Heat transfer was simulated by using COMSOL Multiphysics as mathematical modeling. When the heat (50°C) was applied to the microheater during the DNA hybridization step, we observed that the RCT values increased about 236% and 90% as opposed to on-chip heating experiments and off-chip non-heating experiments. We conclude from this observation that the microheater indeed can significantly improve the performance of the nucleic acid hybridization assay and paves the way for the development of highly- sensitive integrated label-free biosensors Keywords: Electrochemical impedance spectroscopy, lab-on-a-chip, microheater, DNA hybridization sensitivity.