CuS quantum dots activated DNAzyme for ratiometric electrochemical detection of telomerase activity

Telomerase activity detection has attracted much attention concerning its importance for early cancer diagnosis. Here, we established a ratiometric electrochemical biosensor for telomerase detection based on CuS quantum dots (CuS QDs) dependent DNAzyme-regulated dual signals. The telomerase substrate probe was used as the linker to combine the DNA fabricated magnetic beads and CuS QDs. In this way, telomerase extended the substrate probe with repeated sequence to from hairpin structure, releasing CuS QDs as an input to DNAzyme modified electrode. DNAzyme was cleaved with high current of ferrocene (Fc) and low current of methylene blue (MB). On the basis of the obtained ratiometric signals, telomerase activity detection was achieved in the range of 1.0 × 10−12-1.0 × 10−6 IU/L, with the limit of detection down to 2.75 × 10−14 IU/L. Moreover, telomerase activity from HeLa extracts was also tested to verify the clinical application.