A CRISPR-driven aptasensor for colorimetric monitoring of lead (II) ion assisted by rolling circle amplification process: Effective in controlling food and health safety.

Herein, an efficient colorimetric aptasensor has been introduced for highly sensitive measurement of lead (II) ions (Pb2+) by integrating the advantages of clustered regularly interspaced short palindromic repeats (CRISPR) system, the rolling circle amplification (RCA) process, and the catalytic activity of gold nanoparticles (AuNPs) for the first time. The presence of Pb2+ inactivates the CRISPR system, making it unable to cleave the complementary sequence (CS) on the surface of ferrofluids (FFDs) and the formation of RCA product. By trapping AuNPs inside the RCA mass and subsequent magnetic separation of FFDs, the supernatant color remains yellow after adding 4-nitrophenol (4-NP). In the absence of Pb2+, the supernatant color changes to colorless, due to the activation of CRISPR-Cas12a and the lack of large DNA structures. The colorimetric aptasensor can monitor Pb2+ ions in the concentration ranges of 0.1 pM-20 nM and 20 nM-800 nM with a detection limit of 0.024 pM. It can also quantify Pb2+ in the biological, cosmetic, and marine samples.