Development and validation of multiresidue method for organophosphorus pesticides in lanolin using gas chromatography-tandem mass spectrometry

A MnO2 nanosheet-mediated CRISPR/Cas12a system for the detection of organophosphorus pesticides in environmental water

Nowadays, easy, convenient, and sensitive sensing strategies are still critical for organophosphorus pesticides in environmental water samples. Herein, a novel organophosphorus pesticide (OP) assay based on acetylcholinesterase (AChE) and a MnO2 nanosheet-mediated CRISPR/Cas12a reaction is reported. The single-strand DNA (ssDNA) activator of CRISPR/Cas12a was simply adsorbed on the MnO2 nanosheets as the nanoswitches of the assay. In the absence of target OPs, AChE hydrolyzed acetylcholine (ATCh) to thiocholine (TCh), which reduced the MnO2 nanosheets to Mn2+, resulting in the release of the activator followed by activation of the CRISPR/Cas12a system. The activated Cas12a thereafter nonspecifically cleaved the FAM/BHQ1-labeled ssDNA (FQ-reporter), producing a fluorescence signal. Upon the addition of target OPs, the hydrolysis of ATCh by AChE was inhibited owing to OPs combining with AChE, and thus effective quantification of OPs could be achieved by measuring the fluorescence changes of the system. As a proof of concept, dichlorvos (DDVP) was chosen as a model OP analyte to address the feasibility of the proposed method. Attributed to the excellent trans-cleavage activity of Cas12a, the fluorescent biosensor exhibits a satisfactory limit of detection (LOD) for DDVP at 0.135 ng mL-1. In addition, the excellent recoveries for the detection of DDVP in environmental water samples demonstrate the applicability of the proposed assay in real sample research.

Serum butyrylcholinesterase activity in healthy dogs with and without exposure to diazinon

BACKGROUND

Cholinesterase is a biomarker for poisonings by anticholinesterase agents, but its reference values are scarce, and possible interaction with collars containing parasiticides has not been studied.

OBJECTIVES

We aimed to evaluate the serum cholinesterase activity of healthy dogs without a history of contact with anticholinesterase agents and healthy animals exposed to commercial collars containing organophosphate.

METHODS

Ninety-nine dogs were used and included healthy animals without recent exposure to anticholinesterase agents and healthy animals previously exposed to diazinon collars. Serum quantification of the enzyme butyrylcholinesterase (BuchE) through spectrophotometry was conducted on all samples. In experiment 1, BuchE activity was quantified at time 0 and 7 days after, a time when the samples were kept at -18°C. In experiment 2, sampling times were 0, 7, 14, 21, 28, and 56 days.

RESULTS

Time 0 values were 4622.38 ± 1311.53 U/L. After 7 days, a significant decay was observed, with a mean of 3934.45 ± 1430.45 U/L. Spearman's test was performed, finding a weak correlation between ALT, creatinine, total plasma proteins, age, weight, red blood cells, platelets, leukocytes, and BuchE activities. In experiment 2, the mean at time 0 was 4753 ± 454.8 U/L. With exposure to the collar, there was a decay of up to 93% after 14 days.

CONCLUSIONS

Normality values of serum BuchE in healthy dogs without a history of exposure to anticholinesterase agents were 4360.8-4883.96 U/L. Freezing serum caused a decrease in BuchE activity. Exposure to commercial collars containing diazinon also reduced BuchE activity without clinical signs, indicating that previously exposed animals should be evaluated carefully.