Label-free detection of telomerase activity using guanine electrochemical oxidation signal

Eskiocak U., Ozkan-Ariksoysal D., Ozsoz M., Oktem H. A.

ANALYTICAL CHEMISTRY, vol.79, no.22, pp.8807-8811, 2007 (Peer-Reviewed Journal) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 79 Issue: 22
  • Publication Date: 2007
  • Doi Number: 10.1021/ac071014r
  • Journal Indexes: Science Citation Index Expanded, Scopus
  • Page Numbers: pp.8807-8811


Telomerase is an important biomarker for cancer cells and its activation in 85% of all cancer types confers a clinical diagnostic value. A label-free electrochemical assay based on guanine oxidation signal to measure telomerase activity is described. This developed technology combined with a disposable sensor, carbon graphite electrode (CGE), and differential pulse voltammetry (DPV) was performed by using PCR amplicons with/without telomeric repeats as the guanine oxidation signal observed at +1.0 V measured after the immobilization of PCR products. Guanine oxidation signal was chosen as a measure of telomerase activity because a substantial increase in the number of guanines was introduced by the action of telomerase which adds hexameric repeats (TTAGGG)(n) that contain 50% guanine. The developed assay was shown to specifically measure telomerase activity from cell extracts, and elongation rates increased linearly in a concentration dependent manner. Telomerase activity could be detected in cell extracts containing as low as 100 ng/mu L of protein. All of the electrochemical measurements were also confirmed with the conventional TRAP-silver staining assay. Rapidity, simplicity, and the label-free nature of the developed assay make it suitable for practical use in quantitative determination of telomerase activity from clinical samples for diagnosis of cancer.