An amplified fluorescence biosensor for intracellular telomerase determination and in situ imaging based on thioflavin T and conjugated polymer nanoparticles

Abstract

Telomerase, as a significant tumor biomarker, is highly associated with cancers. Highly sensitive determination of telomerase activity is beneficial to accurate diagnosis and treatment of malignant tumors. A new simple and elegant fluorescence sensing strategy based on thioflavin T (ThT) and conjugated polymer nanoparticles was established to determine telomerase activity in living cells. In the presence of telomerase, the primer is prolonged with repeated sequence of (TTAGGG)n. This long G-riched sequence can form G-quadruplex in the mediation of ThT. The combination of ThT and G-quadruplex allows ThT to emit robust fluorescence. The fluorescence can be further amplified by positively charged conjugated polymer nanoparticles (PPE-PLL). The remarkable amplification is attributed to the disaggregation of PPE-PLL nanoparticles and a good superposition of fluorescence emission from ThT and PPE-PLL. The results demonstrated a new amplification assay for the determination of telomerase activity in cell extracts and living cells with high specificity and sensitivity. The limit of detection is estimated to be 3 HeLa cells in 400 μL. It is not only more sensitive than most reported biosensors for telomerase detection. Still, it is extremely simple, rapid, and low-cost since it is PCR-free, label-free, and enzyme-free.