RESUMO
In recent years, incidents of pesticide pollution and abuse of feed additives have occurred frequently, which pose a great threat to human health. Raman spectroscopy has become an important method in the field of food safety due to its rapidity, simplicity and sensitivity. It is important to obtain complex structure to promote surface-enhanced Raman scattering (SERS) effect. In this study, gold helical nanoparticles with rich surface structure were synthesized using cysteine as induce agent. Notably, the complex helical structure and tip led to an excellent electromagnetic enhancement property. The helical structure showed ultra-sensitive detection of hazardous molecular, such as thiram and ractopamine. Interestingly, the D/L-Au structure had significant chiral optical activity and could be used as an unlabeled SERS platform for enantiomer identification. This study provided an effective strategy for the detection of pesticides and feed additives, which could be applied in other aspects of food safety in the future.
RESUMO
The trans-cleavage properties of Cas12a make it important for gene editing and disease diagnosis. In this work, the effect of spatial site resistance on the trans-cleavage activity of Cas12a was studied. First, we have explored the cutting effect of Cas12a when different-sized nanoparticles are linked with various spacings of DNA strands using the fluorescence method. The minimum spacing with different-sized nanoparticles that cas12a can cut was determined. We found that when the size of the nanoparticles increases, the minimum spacing that cas12a can cut gradually increases. Subsequently, we verified the conclusion using the surface-enhanced Raman scattering (SERS) method, and at the same time, we designed a SERS biosensor that can achieve ultrasensitive detection of P53 DNA with a linear range of 1 fM-10 nM and a limit of detection of 0.40 fM. Our work develops a deep study of the trans-cleavage activity of Cas12a and gives a guide for DNA design in cas12a-related studies, which can be applied in biomedical analysis and other fields.
