ONCHIP ELECTROCHEMICAL DETECTION OF DNA HYBRIDIZATION BY 2-ELECTRODES LINEAR SWEEP VOLTAMMETRY

The implementation of a large number of diagnostic screening tests requires a paradigm change from the classical hospital-centred analysis lab, towards a decentralized point-of-care testing that is expected to foster the birth of personalized medicine in the near future. Low-cost, automatic fool-proof testing instrumentation and parallelized analyses will represent key technologies for the implementation of such epochal change. Even if the best limits of detection are currently obtained by using optical transducer techniques, electrochemical biosensors are promising for the implementation of highly integrated, programmable and massively parallelized analytical devices. The techniques used for such parallelized electrochemical assays are nowadays performed with strategies that derive directly from ―classical‖ techniques which involve different types of electrodes which are usually bulky and made of materials hardly compatible with standard industrial fabrication processes. An example is the work from Choi et al. [1], where an array of microfabricated working electrodes is used with an external common Ag/AgCl reference electrode and a common Pt counter electrode. In a more modern approach all miniaturized electrodes necessary for the measurements are fabricated on-chip with a standard industrial process, In this communication, we report the design, implementation and characterization of a 2-electrodes on-chip biosensor based on the selective binding of Hoechst 33258 [2‘-(4-hydroxyphenyl)-5-(4-methyl-1-piperazinyl)-2,5‘-bi(1H-benzimidazole)], an electrochemically active groove binder, to a DNA duplex. The electrochemical technique operates on the same principle as Linear Sweep Voltammetry (LSV), but the voltage is swept linearly between the two electrodes of the biochip, without a direct control of the voltage at the surface of the working electrode. The anodic currents are qualitatively comparable to a standard system (fig.1), and the biosensor has the same limit of detection of 10nM (fig.2) as a standard bulky 3-electrodes setup [1]. Such technique has proved to work in a device composed of several measuring micro-electrodes embedded in a microfluidic system (fig. 3), and fabricated with standard industrial processes, and is promising for applications that require massively parallelized biosensors.