A cascade signal amplification strategy for ultrasensitive colorimetric detection of BRCA1 gene

In this work, we reported a new cascade signal amplification strategy to combine DNAzyme assistant DNA recycling followed with rolling circle amplification (RCA) for highly sensitive colorimetric detection of breast cancer1 (BRCA1) gene. A hairpin probe (HP) was designed, containing the 3'-protruding DNA sequence as the target recognition unit and the caged 8-17 DNAzyme fragment in the loop region as a trigger for the next reaction. Once challenged with the target DNA, the DNAzyme was liberated from the caged structure. In the presence of Pb2+ cofactor, the DNAzyme led to the cleavage of a large number of molecular beacons (MBs), accompanied by the release of another free DNAzyme fragment for the successive cleavage process and autonomous generation of numerous padlock probes for triggering the RCA reaction. The amplified RCA products can form G-quadruplex/hemin DNAzyme to act as a direct signal readout element. The multi-signal amplification of this sensing system, provides a sensitive detection of BRCA1 down to the femtomolar level (3.3 fM) with a linear range of 7 orders of magnitude. Moreover, it holds promise for single nucleotide polymorphism (SNP) analysis.