A dual-amplification label-free ratiometric fluorescent sensor for accurate monitoring of telomerase activity based on unique intercalation characteristics of dyes toward different DNA structures

Accurate evaluation and reliable quantitation of telomerase activity in various cancer cells is of significant importance to early cancer diagnosis and therapy. All previously reported ratiometric fluorescence telomerase activity assays inevitably required the expensive labeling or sophisticated probe synthesis, which were laborious and time-consuming. To overcome such restrictions, herein we developed, for the first time, a facile and label-free ratiometric fluorescence sensing strategy for accurately and sensitively detecting telomerase activity based on unique intercalation characteristics of dyes toward double-stranded DNA and G-quadruplex, respectively. By taking advantage of the dual amplification method consisting of catalytic hairpin assembly and exonuclease III assisted cleavage reaction, telomerase activity can be quantitatively detected in MCF-7 cells ranging from 50 to 2000 with a detection limit of 16 MCF-7 cells. Furthermore, our approach could distinguish the relative telomerase activity in cancer cells from that in normal cells, as well as in different cancer cells. It was also confirmed that our strategy displayed good analytical performance for screening the inhibitors for telomerase. More importantly, compared to those labeling and/or single signal-based methods for telomerase activity detection, this assay not only effectively circumvented the expensive labeling and complex probe preparation but also avoided false-positive results, thus exhibiting the appealing features of simplicity, low cost, and high accuracy. Overall, our method might be a promising tool in telomerase activity analysis and telomerase-targeted antitumor drugs screening.