Ultrasensitive colorimetric biosensor for BRCA1 mutation based on multiple signal amplification strategy

Colorimetric biosensors have attracted wide attention due to their low cost, simple operation, rapid response and good reproducibility. However, insufficient sensitivity limits their applications. This report describes the design of a colorimetric biosensor based on a three-step multiple signal amplification strategy to detect breast cancer-associated BRCA1 mutation. The capture unit, signal unit, and target DNA form a sandwich construction. The signal probes are immobilized on the surface of nanomaterials to form the signal unit, which can catalyze the reduction of a colorimetric substrate 4-nitrophenol (4-NP). Firstly, 0D gold nanoparticles (AuNPs) are employed to catalyze 4-NP reduction and reaches 10²-fold signal amplification. Then AuNPs are decorated on the surface of 2D material, such as graphene oxide (GO), the catalytic efficiency is further enhanced to 10⁴-fold signal amplification. The third step amplification is achieved by replacing stable GO with oxidizable 2D material (Bi₂Se₃ nanosheets), resulting in a nearly 10¹⁰-fold amplification. The sandwich-type Bi₂Se₃-AuNPs biosensor shows excellent sensitivity and selectivity. The detection limit can reach up to 10^-18 M and there is a good linear relationship between the reaction kinetics constant and the DNA concentration in the range of 10^-12-10^-18 M. In addition, one-base mismatch, two-base mismatch and non-complementary sequences can be distinguished clearly by this biosensor. This design may have beneficial clinical application prospects for cancer genetic screening and early diagnosis.