Label-Free Telomerase Activity Detection via Electrochemical Impedance Spectroscopy

In the last decade, researchers have been searching for innovative platforms, methods, and techniques able to address recurring problems with the current cancer detection methods. Early disease detection, fast results, point-of-care sensing, and cost are among the most prevalent issues that need further exploration in this field. Herein, studies are focused on overcoming these problems by developing an electrochemical device able to detect telomerase as a cancer biomarker. Electrochemical platforms and techniques are more appealing for cancer detection, offering lower costs than the established cancer detection methods, high sensitivity inherent to the technique, rapid signal processing, and their capacity of being miniaturized. Therefore, Au interdigital electrodes and electrochemical impedance spectroscopy were used to detect telomerase activity in acute T cell leukemia. Different cancer cell concentrations were evaluated, and a detection limit of 1.9 × 10⁵ cells/mL was obtained. X-ray photoelectron spectroscopy was used to characterize the telomerase substrate (TS) DNA probe self-assembled monolayer on gold electrode surfaces. Atomic force microscopy displayed three-dimensional images of the surface to establish a height difference of 9.0 nm between the bare electrode and TS-modified Au electrodes. The TS probe is rich in guanines, thus forming secondary structures known as G-quadruplex that can be triggered with a fluorescence probe. Confocal microscopy fluorescence images showed the formation of DNA G-quadruplex because of TS elongation by telomerase on the Au electrode surface. Moreover, electrodes exposed to telomerase containing 2',3'-dideoxyguanosine-5'-triphosphate (ddGTP) did not exhibit high fluorescence, as ddGTP is a telomerase inhibitor, thus making this device suitable for telomerase inhibitors capacity studies. The electrochemical method and Au microchip device may be developed as a biosensor for a point-of-care medical device.