Reliable Förster Resonance Energy Transfer Probe Based on Structure-Switching DNA for Ratiometric Sensing of Telomerase in Living Cells

In situ detection and monitoring of telomerase is of great importance as it is a relatively specific cancer target. However, the complexity of the biological system makes it difficult for the nanoprobe to keep absolutely stable and have a low background in living cells. This study designs a probe termed Förster resonance energy transfer (FRET) nanoflare to achieve ratiometric fluorescent detection of intracellular telomerase with higher specificity, which can effectively resist the disturbance from DNase I and GSH, etc. The probe is composed of a gold nanoparticle (AuNP) which is functioned with telomerase primer sequences (TS) and flares fluorescently labeled donors and acceptors at two terminals. In the presence of telomerase, flares are displaced from the primer sequences and form hairpin structures, so that the donors and acceptors are brought into close proximity, resulting in high FRET efficiency. The probe exhibits good performance for efficiently distinguishing tumor cells from normal cells and monitoring the change of intracellular telomerase activity during treatment with telomerase-related drugs, showing great potential for cancer diagnosis and estimating therapeutic effect.