A Multi-Enzyme Cascade Response for the Colorimetric Recognition of Organophosphorus Pesticides Utilizing Core-Shell Pd@Pt Nanoparticles with High Peroxidase-like Activity.

In modern agricultural practices, organophosphorus pesticides or insecticides (OPs) are regularly used to restrain pests. Their limits are closely monitored since their residual hinders the capability of acetylcholinesterase (AChE) and brings out a threatening accumulation of the neurotransmitter acetylcholine (ACh), which affects human well-being. Therefore, spotting OPs in food and the environment is compulsory to prevent human health. Several techniques are available to identify OPs but encounter shortcomings like time-consuming, operating costs, and slow results achievement, which calls for further solutions. Herein, we present a rapid colorimetric sensor for quantifying OPs in foods using TMB as a substrate, a multi-enzyme cascade system, and the synergistic property of core-shell Palladinum@Platinum (Pd@Pt) nanoparticles. The multi-enzyme cascade response framework is a straightforward and effective strategy for OPs recognition and can resolve the previously mentioned concerns. Numerous OPs, including Carbofuran, Malathion, Parathion, Phoxim, Rojor, and Phosmet, were successfully quantified at different concentrations. The cascade method established using Pd@Pt had a simple and easy operation, a lower detection limit range of (1-2.5 ng/mL), and a short detection time of about 50 min. With an R2 value of over 0.93, OPs showed a linear range of 10-200 ng/mL, portraying its achievement in quantifying pesticide residue. Lastly, the approach was utilized in food samples and recovered more than 80% of the residual OPs.

Phosphatase-like activity of single-atom CeNC nanozyme for rapid detection of Al3.

Single-atom nanozymes are a class of nanozymes with attractive enzyme-like activities. They usually mimic oxidoreductases and lack other types of enzyme-like activities. Hence, we verified a single-atom CeNC (SACeNC) nanozyme with an excellent phosphatase-like (PPA-like) activity, which could catalyze the dephosphorylation of inorganic phosphates. Meanwhile, we found that Al3+ could specifically combine with the O atom in its structure to form an Al-O bond, which could inhibit its PPA-like activity. Based on this principle, we have constructed a fast, portable, and efficient fluorescent liquid phase sensor to detect Al3+. The detection time was only 4 min, and the limit of detection (LOD) was 22.89 ng/mL in the linear range of 5-25 µg/mL. This study not only verified that single-atom nanozymes mimic phosphatase activities, but also applied its unique enzyme-like to the field of food safety rapid detection.

Zwitterion-modified antifouling swab joint "Snake-Eye" for detection of Salmonella in colored foodstuffs.

Salmonella can be found in foods such as meat, eggs and milk, posing a serious threat to human health. To address the challenge of interference with detection signals from large molecular contaminants and colored substances in complex food matrices, we had dived into easy-to-use antifouling swabs, which were modified with sodium sulfonyl methacrylate (SBMA) by photopolymerization and incubated with Salmonella-specific aptamers. Surface modification of SBMA showed the antifouling property of the swab, and the aptamer collected Salmonella in the sample. Gold-palladium (Au-Pd) nanoparticles with photothermal properties were combined with the aptamer by freezing technique to identify Salmonella on the swab and output the signal. In addition, we used a simple "Snake-Eye" device, which consists of laser transmitter, infrared thermometer and smartphone to quantitatively identify Salmonella in colored foodstuffs. The linear detection range was 102-107 CFU mL-1, and the detection limit was 13.20 CFU mL-1. The findings suggest that our swabs had strong antifouling effect, exhibit high sensitivity in complex food matrices especially colored foodstuffs, and was easy to use on site.