Dual-mode colorimetric and fluorescence detection of BRCA1 based on a CRISPR-Cas12a system

Breast cancer, the most common malignant tumor in the world, seriously threatens human life and health. Early diagnosis of breast cancer may help enhance the survival rate. In this work, a colorimetric and fluorescent dual-mode biosensor based on the CRISPR-Cas12a system was constructed to detect the breast cancer biomarker BRCA1. The intact G4 DNA, with the assistance of K⁺ and hemin, catalyses the oxidation of o-phenylenediamine (OPD) with the assistance of hydrogen peroxide (H₂O₂), generating the oxidation product 2,3-diaminophenazine (DAP), which has distinct absorption and fluorescence peaks. The presence of the target BRCA1 activates the trans-cleavage activity of CRISPR-Cas12a, leading to the cleavage of G4 DNA and inhibiting the catalytic oxidation of OPD. Target BRCA1 was quantitatively determined by measuring both the absorbance and fluorescence intensity of DAP. The detection limits were calculated to be 0.615 nM for the colorimetric method and 0.289 nM for the fluorescence method. The dual-mode biosensor showed good selectivity and reliability for BRCA1 and can resist interference from complex substrates, and it has great potential in biomedical detection.