A sensitive colorimetric method for detection of copper ions (Cu 2+ ) was developed based on surface modification of Ag/Pt nanoclusters (Ag/Pt NCs) and regulation of the peroxidase-like activity. It was found that 3-mercaptopropionic acid (MPA) could inhibit the catalytic ability of Ag/Pt NCs, however it would lose the inhibition toward catalytic ability of Ag/Pt NCs after oxidization by oxygen through the catalysis of Cu 2+ . On the basis of this, a colorimetric method was developed for the detection of Cu 2+ by measuring the colorimetric signal variation of the TMB-H 2 O 2 reaction. This method exhibited high sensitivity and selectivity toward Cu 2+ over a panel of other metal ions, in the linear range of 10–100 nM with a detection limit of 5.0 nM. The method was simple and low cost, and suitable for Cu 2+ detection in real water samples.
Accurate, rapid, and sensitive pathogenic detections play an important role in food safety. Herein, we developed a novel CRISPR/Cas12a mediated strand displacement/hybridization chain reaction (CSDHCR) nucleic acid assay for foodborne pathogenic colorimetric detection. A biotinylated DNA toehold is coupled on avidin magnetic beads and acts as an initiator strand to trigger the SDHCR. The SDHCR amplification allowed the formation of long hemin/G-quadruplex-based DNAzyme products to catalyze the TMB-H2O2 reaction. In the presence of the DNA targets, the trans-cleavage activity of CRISPR/Cas12a was activated to cleave the initiator DNA, resulting in the failure of SDHCR and no color change. Under optimal conditions, the CSDHCR has a satisfactory linear detection of DNA targets with a regression equation Y = 0.0531*X – 0.0091 (R2 = 0.9903) in the range of 10 fM to 1 nM, and the limit of detection was determined as 4.54 fM. In addition, Vibrio vulnificus, one foodborne pathogen, was used to verify the practical application of the method, and it showed satisfactory specificity and sensitivity with a limit of detection at 1.0 × 100 CFU/mL coupling with recombinase polymerase amplification. Our proposed CSDHCR biosensor could be a promising alternative method for ultrasensitive and visual detection of nucleic acids and the practical application of foodborne pathogens.
危险品化学品经营许可证（带存储）