Nanozyme-catalysed CRISPR-Cas12a system for the preamplification-free colorimetric detection of lead ion.

CRISPR-based detection was often based on the target preamplification to realize the high sensitivity. Here, we prepared a CRISPR-Cas12a system for the colorimetric detection of lead ion (Pb) based on the assistance of DNAzyme and nanozyme instead of preamplification. The recognition between GR-5 DNAzyme and Pb could trigger the CRISPR-Cas12a system. MnO nanozymes connected with magnetic beads through single stranded DNA were prepared as the colorimetric signal probes and catalyst of CRISPR-Cas12a system for the strong oxidase-like activity inducing the color change of 3,3',5,5'-tetramethylbenzidine. The nanozyme-catalysed CRISPR-Cas12a system could be used to detect Pb through the color change with high specificity and sensitivity. The linear range of this approach was 0.8 nM-2500 nM, with a limit of detection of 0.54 nM. This method was applied for the detection of the Pb in food samples indicating good accuracy and anti-interference ability.