Double Isothermal Amplification and CRISPR-Cas12a for Sensitive Detection of Citrinin
Man Zhang, Xiaoting Xue, Haiyue Gong, Baolin Liu, Lei Ye
Abstract
An analytical method is developed for ultrasensitive detection of citrinin using double isothermal amplification and CRISPR-Cas12a. Gold nanoparticles (AuNPs) modified with antigen and thiol-terminated, single-strand DNA (ssDNA) are used as a probe. The antigen-modified AuNPs compete with citrinin to bind to magnetic beads coated with an anticitrinin antibody. After a simple magnetic separation, the AuNPs are collected, and the ssDNA are released after they are washed with a dithiothreitol solution. The ssDNA is first amplified by an exponential amplification reaction and then used as a primer in a subsequent hybridization chain reaction to produce double-stranded DNA (dsDNA) that contains a protospacer adjacent motif to allow recognition by CRISPR-Cas12a. The dsDNA activates the Cas12a-gRNA to cleave a reporter ssDNA to generate a fluorescence signal. The developed analytical method has a low detection limit (0.127 ng mL–1) and a wide linear range (0.005–500 μg mL–1) for detection of citrinin. For detection of citrinin in oat and flour, recoveries of 97–104% and 105–111% are obtained, respectively. By combining double isothermal amplification with CRISPR-Cas12a, ultrahigh sensitivity and selectivity can be achieved for detection of toxins in food.