Circulating tumor DNA (ctDNA) is a characteristic tumor biomarker used for cancer diagnosis, treatment, and prognosis. However, the low concentration of ctDNA in peripheral blood and the interference of complex matrices with signals make the detection of ctDNA extremely challenging. Single-particle collision electrochemistry (SPCE) has been widely used in bioanalysis due to its advantages such as high throughput, simple operation, high sensitivity, and low detection limit. In this work, a novel SPCE biosensor for the rapid detection of ctDNA was developed by combining CRISPR/Cas12a with excellent cleavage activity and magnetic beads (MBs) with good separation and enrichment capabilities. The trans-cleavage ability of CRISPR/Cas12a can only be triggered in the presence of target ctDNA to effectively cleave the ssDNA2 on the surface of Ag NPs-ssDNA2 within 1 h, thereby activating the collision activity of silver nanoparticles (Ag NPs). ctDNA was quantified by the collision frequency of Ag NPs. The detection limit of the developed SPCE biosensor for ctDNA was as low as 4.2 fM, and the linear range was 10 fM-1 nM. In addition, MBs allow the biosensor to detect ctDNA in complex samples by directly sampling from complex matrices, with excellent sensitivity and specificity, demonstrating the great potential of the developed SPCE biosensor in the detection of patient samples.
