Dielectrophoresis assisted impedance spectroscopy for detection of gold-conjugated amplified DNA samples

Abstract

Molecular diagnostics have always been at the forefront of disease identification and control. Various approaches exist for carrying out molecular diagnostics through identification of genes or proteins and are largely deployed in the laboratories for testing; although there exist a wide possibility of refinement in these existing processes. In this respect, impedance-based detection methods have emerged as one of the most deployable methods primarily due to their robust and easy nature of measurement and easy integrability with microelectronic systems. Impedance assisted technique is very commonly used for detection of DNA and DNA amplification through PCR process although it does not really make a very specific identification system parallel to some other optical techniques; like TaqMan PCR, qPCR or Molecular beacon assisted detection of DNA sequences. In the current article, we have developed a novel strategy through nanoparticle labeling and dielectrophoretic manipulation which enhances the specificity of the identification of tagged-amplified DNA samples coming out of a PCR process. Impedance characteristics with respect to a various number of PCR cycles with a product consisting of nanoparticle-labeled DNA samples are measured with respect to increasing concentration. A significant differentiation is observed between the non-labeled non-specifically amplified DNA and the labeled specifically amplified sequence through varied impedance signals. The impedance characterization is performed at the instance where the analyte is mostly near the electrodes and this is accomplished through dielectrophoresis scheme. The different dielectrophoretic capture frequencies have been observed for non-labeled and labeled DNA products. This sensor has achieved a limit of detection of the range of 25–30 DNA copies. The eventual goal here is to integrate this strategy with microchip PCR to evolve a paradigm shift in the PCR microchip technology.