Applying CRISPR/Cas system as a signal enhancer for DNAzyme-based lead ion detection

Heavy metal lead accumulation in the environment pollutes the ecology systems and further threatens the human health. It is necessary to develop a sensitive method to detect it. Here, we propose a highly sensitive lead detection method by combining DNAzyme and CRISPR system. Once the lead ion is recognized, the substrate chain of DNAzyme is cleaved to produce single strand DNA. The produced single strand DNA can be detected by Cas protein/guide RNA complex and further trigger the collateral cleavage effect of CRISPR system, which can indiscriminately cut short single strand DNA reporters. By this way, the detection signals can be greatly amplified. This method can detect lead ions as low as 0.48 nM. The sensitivity is higher than the DNAzyme method. Furthermore, the portable 3D printing device is designed to observe the fluorescent signals so the end-point detection results can be visualized by the naked eyes. The entire detection process can avoid using bulky and expensive instruments, which can promote on-site lead ion detection.