Amplification of the Fluorescence Signal with Clustered Regularly Interspaced Short Palindromic Repeats-Cas12a Based on Au Nanoparticle-DNAzyme Probe and On-Site Detection of Pb2+ Via the Photonic Crystal Chip.

Although great headway has been made in DNAzyme-based detection of Pb2+, its adaptability, sensitivity, and accessibility in complex media still need to be improved. For this, we introduce new ways to surmount these hurdles. First, a spherical nucleic acid (SNA) fluorescence probe (Au nanoparticles-DNAzyme probe) is utilized to specifically identify Pb2+ and its suitability for precise detection of Pb2+ in complex samples due to its excellent nuclease resistance. Second, the sensitivity of Pb2+ detection is greatly enhanced via the use of a clustered regularly interspaced short palindromic repeats-Cas12a with target recognition accuracy to amplify the fluorescent signal upon the trans cleavage of the SNA (signal probe), and the limit of detection reaches as low as 86 fM. Third, we boost the fluorescence on photonic crystal chips with a bionic periodic arrangement by employing a straightforward detection device (smartphone and portable UV lamp) to achieve on-site detection of Pb2+ with the limit of detection as low as 24 pM. Based on the abovementioned efforts, the modified Pb2+ fluorescence sensor has the advantages of higher sensitivity, better specificity, accessibility, less sample consumption, and so forth. Moreover, it can be applied to accurately detect Pb2+ in complex biological or environmental samples, which is of great promise for widespread applications.