The enzyme telomerase is present in about 85% of human cancers which makes it not only a good target for cancer treatment but also an excellent marker for cancer detection. Using a single stranded DNA probe specific for telomerase binding and reverse transcription tethered to an interdigital gold electrode array surface, the chromosome protection provided by the telomerase was replicated and followed by Electrochemical Impedance Spectroscopy as an unlabeled biosensor. Using this system designed in-house, easy and affordable, impedance measurements were taken while incubating at 37 °C and promoting the probe elongation. This resulted in up to 14-fold increase in the charge transfer resistance when testing a telomerase-positive nuclear extract from Jurkat cells compared to the heat-inactivated telomerase-negative nuclear extract. The electron transfer process at the Au electrodes was studied before the elongation, at different times after the elongation, and after desorption of non-specific binding.

DNA sensors are innovative diagnostic tools that have gained broad acceptance in recent years. Different procedures have been used to develop these sensors. One of the most frequently used method is the self-assemble monolayer (SAMs) that provides advantages in terms of simplicity, efficiency and cost of electrode design. Gold surface modification with SAMs change the electrochemical capacitive behavior of their surface which can be measured by Electrochemical Impedance Spectroscopy (EIS). Tethering of ssDNA via SAMs techniques onto metallic Au surface provide a biosensing probe which is sensitive to changes on the surface, and these changes on the ssDNA conformation correlate to changes in the double layer capacitance (Cdl). Using this as the basis, a novel microchip with an interdigitated array electrodes was done and used as a real-time electrochemical biosensor for the detection of DNA amplification directly on its surface. The microchip was designed using a silicon/SiO2 substrate and gold thin film patterned by photolithography. The microchip is connected by a USB type A connector. In this device, the polymerase chain reaction (PCR) takes place on the surface interface, and the primer ssDNA tethered to the surface is elongated. Every modification, variation or alteration of the DNA on the surface of the electrodes result in changes in the Cdl and measured by EIS having a non-faradaic and label-free detection. The recognized sensitivity of electrochemical platforms and the well-known specificity of exclusive primers provide portability, reliability, rapidness, and accuracy in a robust biosensor microchip. Moreover, by avoiding the use of optical labels we are able to measure complex or unpurified biofluid samples without the need of extensive purification. All these features will have a tremendous impact on the biomedical science filling the absence of methods that can detect DNA in real-time and in a direct readout of crude biological fluids.