Label-Free Telomerase Activity Detection via Electrochemical Impedance Spectroscopy

Abstract

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.

Multicolor Fluorescent Graphene Oxide Quantum Dots for Sensing Cancer Cell Biomarkers

“…Therefore, we designed an experiment to make a proof-of-concept that would show the change in fluorescence produced by the interaction of GOQDs with single-stranded DNA of different sizes attached to their surface that was elongated by telomerase. Telomerase is an enzyme that is present in 85% of cancer which has been the object of study of different sensors in the last few years to detect cancer. , …”

“…Telomerase is an enzyme that is present in 85% of cancer which has been the object of study of different sensors in the last few years to detect cancer. 37,59 In order to show the change in fluorescence of GOQDs in their interaction with telomerase as a biomarker for cancer, single-stranded DNA (ssDNA) probes were tethered to the surface of the quantum dots that include the sequence 5′-TTAGGG-3′ at the end, which is known to be recognized by the enzyme telomerase to elongate the strand repeating the same sequence. 37 Using nuclear extracts from T-cells, cancerpositive (Jurkat cells) and -negative (PBMC) samples were tested, finding that the presence of this enzyme changed the fluorescence of the quantum dots, as can be seen in Figure 8.…”

Visually Intracellular Detection of Telomerase Activity Based onDNAStrand Displacement Reaction and Gold Nanoparticle Labeling

“…Considering the essential roles of telomerase in various physiological processes, a series of techniques have been developed to detect telomerase activity, such as the most classical telomere repeat amplification protocol (TRAP), which is regarded as a golden standard method for measuring telomerase activity, [ 8‐9 ] colorimetric method, [ 10‐12 ] electrochemical method, [ 13‐15 ] electrochemiluminescence method, [ 16‐17 ] surface plasmon resonance method (SPR), [ 18‐19 ] etc . Although these methods improve the reliability and sensitivity of the detection, the cell lysate is still the primary analyte used.…”

Evidence of the Cellular Senescence Stress Response in Mitotically Active Brain Cells—Implications for Cancer and Neurodegeneration

“…Similarly, telomerase activity can be quantified with a variety of measurement techniques including, most commonly, the PCR-based telomeric repeat amplification protocol (TRAP) [ 40 ]. A number of methods have also recently been developed, improving upon the convenience, throughput, sensitivity, and reliability of TRAP [ 41 , 42 , 43 ]. These methods provide objective readouts when evaluating potential mechanistic mediators of replicative senescence.…”