A novel “signal on-off-super on” sandwich-type aptamer sensor of CRISPR-Cas12a coupled voltage enrichment assay for VEGF detection

Vascular endothelial growth factor (VEGF) plays an important role in atherosclerosis, and the detection of VEGF is critical for the prevention, monitoring, and diagnosis of cardiovascular diseases. Here, a novel "signal on-off-super on" sandwich-type aptamer sensor with a triple signal amplification strategy was developed for the first time. Based on the capture aptamer was labeled with methylene blue (MB) on the internal bases, clustered regularly interspaced short palindromic repeats (CRISPR)-Cas12a-coupled voltage enrichment was used to amplify the electrochemical signal. To improve the analytical performance of the aptamer sensor, gold nanoparticles@Ti3C2Tx-Mxene (AuNPs@Ti3C2Tx-Mxene) were synthesized through the electrodeposition of AuNPs on the Ti3C2Tx-Mxene surface, providing active sites for the immobilization of the aptamer and amplifying the electrochemical signals. The excellent trans-cleavage activity of the CRISPR-Cas12a system was harnessed to cleave signal probes. The cleaved signal probes were enriched using an electrochemical signal instead of complicated target amplification steps before detection. Hence, we report a simplified detection process for amplifying electrochemical signals. Under optimal conditions, the aptamer sensor exhibited high sensitivity, acceptable stability, and reproducibility with a wide linear range from 1 pM to 10 μM (R2 = 0.9917) and an ultralow detection limit of 0.33 pM (S/N = 3). Therefore, we propose a novel strategy of CRISPR-Cas12a-based protein detection that opens a new window for the diagnostic applications of various biomarkers.