The paper describes a voltammetric method for the quantitation of the activity of telomerase extracted from cancer cells. A thiolated single-stranded telomerase substrate primer was firstly immobilized on a gold electrode. In the presence of a mixture of telomerase and deoxynucleotide triphosphates, the primer becomes elongated and contains repetitive nucleotide sequences (TTAGGG) n . After hybridization with blocker DNA, gold nanoparticles are added and captured by the elongated single-stranded DNA. This reduces the charge transfer resistance of the gold electrode. The telomerase activity is then quantified via differential pulse voltammetry, typically at 0.12 V (vs. SCE). The method is PCR-free, rapid, and convenient. It was applied to the detection of HeLa cells via the telomerase activity of lysed cells. The detection range was from 500 to 50,000 cells/mL and the detection limit was as low as 500 cells/mL.
A telomerase substrate (TS) primer is immobilized on a gold electrode as the sensing interface to detect the activity of telomerase extracted from cancer cells. Unmodified gold nanoparticles (AuNPs) are utilized which change the electrochemical responses.
We describe a PCR-free, enzyme-free, and simple biosensing platform for the electrochemical monitoring of telomerase activity based on Au nanorods (AuNRs) as an electrocatalytic redox mediator, which enhances the electrochemical signal by catalyzing acetaminophen (AP). In this process, acid-functionalized ordered mesoporous carbon (OMC) was modified on a glassy carbon electrode (GCE) surface to offer -COOH sites. Moreover, the amino-modified S1 was fixed on the modified electrode by conducting an amide reaction. TS is extended to (TTAGGG) n repeat units in the presence of telomerase extract and dNTPs. One end (5′) is hybridized with S1 on the electrode, and the remaining end (3′) is combined with AuNRs-S2 probe. Clearly, the telomerase activity is relevant to the amount of connected AuNRs, resulting in different response signals. Therefore, with the telomerase extension triggered hybridization reaction, a large amount of AuNRs catalyst was introduced onto the surface of GCE as the sensing platform, thus achieving a sensitive electrochemical telomerase activity assay in the range of 20–2.15 × 10 6 HeLa cells mL −1 . This sensing platform shows that the limit of detection is 1.74 HeLa cells mL −1 , thus providing a promising method for the determination of telomerase activity and a powerful biosensor for accurate cancer monitoring and diagnosis.
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