A radioactive assay for acetylcholinesterase using anion-exchange disk

Acetylcholinesterase Activity Monitoring and Natural Anti-neurological Disease Drug Screening via Rational Design of Deep Eutectic Solvents and CeO2-Co(OH)2 Nanosheets

The activity monitoring of acetylcholinesterase (AChE) and the screening of its inhibitors are critical for the diagnosis and therapy of neurological diseases. Herein, CeO₂-Co(OH)₂ nanosheets were synthesized for the first time in a newly designed deep eutectic solvent (DES) composed of l-proline and Ce(NO₃)₃·6H₂O, and a colorimetric assay was developed for quantitative detection of AChE and anti-neurological disease drug screening. Impressively, CeO₂-Co(OH)₂ composites prepared in DESs have more prominent oxidase-like activity than Co(OH)₂, CeO₂, and CeO₂-Co(OH)₂ produced in aqueous solution. The mechanism study shows that the oxygen vacancies of CeO₂-Co(OH)₂ play a vital role in oxidase-like catalysis. Based on their excellent oxidase-like activity, the CeO₂-Co(OH)₂ nanosheets have been successfully applied for highly sensitive and selective detection of AChE with a linear range of 0.2-20 mU/mL. This strategy can also be used for inhibitor screening. The sensor displays an excellent linear response in the range of 0.001-2 μg/mL toward an irreversible inhibitor (paraoxon-ethyl). Moreover, five alkaloids, namely, berberine hydrochloride, caffeine, camptothecin, matrine, and evodiamine, were screened by using neostigmine bromide as a control; berberine hydrochloride exhibited a good inhibitory effect on AChE with an IC₅₀ of 0.94 μM, while the other four had no obvious inhibitory effect. The mechanism of the different effects of alkaloids on inhibiting acetylcholinesterase activity was explored via molecular docking and kinetic simulation.

Simultaneous detection of dual biomarkers from humans exposed to organophosphorus pesticides by combination of immunochromatographic test strip and ellman assay

A novel sandwich immunoassay based immunochromatographic test strip (ICTS) has been developed for simultaneously measuring both butyrylcholinesterase (BChE) activity and the total amount of BChE (including inhibited and active enzyme) from 70 μLpost-exposure human plasma sample. The principle of this method is based on the BChE monoclonal antibody (MAb) capable of acting as both capture antibody and detection antibody. The BChE MAb which was immobilized on the test line was able to recognize both organophosphorus BChE adducts (OP-BChE) and BChE and provided equal binding affinity, permitting detection of the total enzyme amount in post-exposure human plasma samples. The formed immunocomplexes on the test line can further be excised from the test-strip for subsequent off-line measurement of BChE activity using the Ellman assay. Therefore, dual biomarkers of BChE activity and phosphorylation (OP-BChE) will be obtained simultaneously. The whole sandwich-immunoassay was performed on one ICTS, greatly reducing analytical time. The ICTS sensor showed excellent linear responses for assaying total amount of BChE and active BChE ranging from 0.22 to 3.58nM and 0.22-7.17nM, respectively. Both the signal detection limits are 0.10nM. We validated the practical application of the proposed method to measure 124 human plasma samples from orchard workers and cotton farmers with long-term exposure to organophosphorus pesticides (OPs). The results were in highly agreement with LC/MS/MS which verified our method is extremely accurate. Combining the portability and rapidity of test strip and the compatibility of BChE MAb as both capture antibody and detection antibody, the developed method provides a baseline-free, low-cost and rapid tool for in-field monitoring of OP exposures.

Evaluating organophosphate poisoning in human serum with paper

This manuscript describes the development and clinical testing of a paper-based, metabolic assay designed for rapid, semi-quantitative measurement of organophosphate poisoning. Paper-based platforms, including point-of-care devices and 96-well plates, provided semi-quantitative information regarding the concentration of AchE (a biomarker for organophosphate poisoning). The paper-based 96-well-plate developed and implemented in this study was used to measure the level of organophosphate poisoning in three different clinical patients. Results were comparable to those obtained using conventional hospital methods currently considered the "gold standard". This diagnostic device offers several advantages over conventional methods, including short operating time (twice as fast as conventional methods), procedure simplicity, and reduced fabrication cost. With further commercialization efforts, the methods described in this manuscript could be applied to a wide range of potential diagnostic applications in the field.

Electrochemical detection of dual exposure biomarkers of organophosphorus agents based on reactivation of inhibited cholinesterase

Considering inter- or intra-individual variation in the normal levels of acetylcholinesterase (AChE), real-time measurement of AChE via the reactivation from a postexposure sample was used, and thus a baseline-free and reliable approach was proposed for detecting/screening low-dose organophosphorus pesticides (OPs) poisons. The principle of this technology is on the basis of parallel measurements of AChE activity before and after reactivation from a postexposure to simultaneously provide the content of dual biomarkers of both enzyme inhibition and enzyme adducts. It is more accurate and reliable compared with only one biomarker (inhibition or adduct). Reactivation from a postexposure sample is a better individual enzyme baseline compared to pre-exposure from the population average level in currently available approaches. AChE activity was measured with an electrochemical method. Greatly enhanced sensitivity was achieved by using Fe3O4/Au nanocomposites to enrich thiocholine, the hydrolysis product of active AChE, followed by electrochemical oxidative desorption of the adsorbed thiocholine. The validation of this method for measurement of OP exposures was further explored with in vitro paraoxon inhibited human red blood cells (RBCs) samples and demonstrated its practicability.

Biomonitoring of organophosphorus agent exposure by reactivation of cholinesterase enzyme based on carbon nanotube-enhanced flow-injection amperometric detection

A portable, rapid, and sensitive assessment of subclinical organophosphorus (OP) agent exposure based on reactivation of cholinesterase (ChE) from OP-inhibited ChE using rat saliva (in vitro) was developed using an electrochemical sensor coupled with a microflow-injection system. The sensor was based on a carbon nanotube (CNT)-modified screen printed carbon electrode (SPE), which was integrated into a flow cell. Because of the extent of interindividual ChE activity variability, ChE biomonitoring often requires an initial baseline determination (noninhibited) of enzyme activity which is then directly compared with activity after OP exposure. This manuscript describes an alternative strategy where reactivation of the phosphorylated enzyme was exploited to enable measurement of both inhibited and baseline ChE activity (after reactivation by an oxime, i.e., pralidoxime iodide) in the same sample. The use of CNT makes the electrochemical detection of the products from enzymatic reactions more feasible with extremely high sensitivity (5% ChE inhibition) and selectivity. Paraoxon was selected as a model OP compound for in vitro inhibition studies. Some experimental parameters, e.g., inhibition and reactivation time, have been optimized such that 92-95% of ChE reactivation can be achieved over a broad range of ChE inhibition (5-94%) with paraoxon. The extent of enzyme inhibition using this electrochemical sensor correlates well with conventional enzyme activity measurements. On the basis of the double determinations of enzyme activity, this flow-injection device has been successfully used to detect paraoxon inhibition efficiency in saliva samples (95% of ChE activity is due to butyrylcholinesterase), which demonstrated its promise as a sensitive monitor of OP exposure in biological fluids. Since it excludes inter- or intraindividual variation in the normal levels of ChE, this new CNT-based electrochemical sensor thus provides a sensitive and quantitative tool for point-of-care assessment and noninvasive biomonitoring of the exposure to OP pesticides and chemical nerve agents.

Endogenous butyrylcholinesterase in SV40 transformed cell lines: COS-1, COS-7, MRC-5 SV40, and WI-38 VA13

Comparison of proteins expressed by SV40 transformed cell lines and untransformed cell lines is of interest because SV40 transformed cells are immortal, whereas untransformed cells senesce after about 50 doublings. In MRC-5 SV40 cells, only seven proteins have previously been reported to shift from undetectable to detectable after transformation by SV40 virus. We report that butyrylcholinesterase is an 8th protein in this category. Butyrylcholinesterase activity in transformed MRC-5 SV40 cells increased at least 150-fold over its undetectable level in MRC-5 parental cells. Other SV40 transformed cell lines, including COS-1, COS-7, and WI-38 VA13, also expressed endogenous butyrylcholinesterase, whereas the parental, untransformed cell lines, CV-1 and WI-38, had no detectable butyrylcholinesterase activity or mRNA. Infection of CV-1 cells by SV40 virus did not result in expression of butyrylcholinesterase, showing that the butyrylcholinesterase promoter was not activated by the large T antigen of SV40. We conclude that butyrylcholinesterase expression resulted from events related to cell immortalization and did not result from activation by the large T antigen.

Microtiter assay for acetylcholinesterase

A microtiter plate adaptation of the classical Ellman colorimetric procedure for measurement of acetylcholinesterase activity is described. This method permits use of an enzyme-linked immunosorbent assay plate reader for rapid analysis of multiple samples and is particularly suitable for analysis of acetylcholinesterase activity on sucrose gradients. The novel procedure is rapid and sensitive and does not require use of radioactive material.