Immobilized acetylcholinesterase in magnetic nanoparticles for in-line inhibition studies using a capillary electrophoresis system

Dual-mode sensing platform based on an iodide ion synergistic covalent triazine frameworks (CTFs) for point-of-care testing (POCT) of acetylcholinesterase

Acetylcholinesterase (AChE) plays a critical role in maintaining nervous system homeostasis and coordinating essential biological reactions. AChE is an important biomarker for early diagnosis and treatment, including Parkinson's disease (PD), Alzheimer's disease (AD), and Huntington's disease (HD). Therefore, developing efficient and immediate sensing platforms for AChE detection is crucial for advancing early diagnostic tools. In this study, we developed a dual-mode colorimetric/photothermal sensing platform based on iodide ion-synergized covalent porphyrin-triazine backbone nanozymes (Zn-CTF/I) to detect AChE with high sensitivity and reliability. The synergistic interaction between iodide ions and zinc atoms effectively modulated the electronic structure of the catalytic active site, significantly enhancing the peroxidase-like (POD-like) activity of Zn-CTF/I. This enhancement led to a 10-fold reduction in the AChE detection limit compared to controls, with a minimum detection limit of 0.003 U L-1, outperforming other reported assays. The integration of temperature-based photothermal signals with colorimetric detection improved the platform's accuracy and reliability. The system also demonstrated excellent recovery performance in detecting AChE in complex serum samples. The proposed dual-mode sensing platform provides a sensitive, reliable, and robust tool for AChE detection, with promising applications in early diagnosis and treatment monitoring of neurodegenerative diseases.

Development and Application of an In-Capillary CE-DAD Method for the Inhibitory Screening of Natural Extracts Towards Acetylcholinesterase Enzyme

Background: The enzymatic activity of acetylcholinesterase (AChE) has been a focal point in neurodegenerative diseases research, particularly in relation to Alzheimer's disease. This is attributed to the significantly reduced levels of cholinergic neurons observed in Alzheimer's patients compared to healthy individuals. The strategy to mitigate the onset of these diseases in patients lies in the exploration of new potential AChE inhibitors with a focus also on natural extracts. A rapid and specific capillary electrophoresis method with direct ultraviolet detection (CZE-UV/Vis) was developed to screen natural extracts by assessing their potential to inhibit AChE. Materials and Methods: To enhance the specificity when analysing complex matrixes such as natural extracts, a sequential analysis approach based on the "sandwich model" was implemented using Ellman's reagent [5,5'-dithiobis-(2-nitrobenzoic acid)] (DTNB) as a colorimetric indicator. Results: A reference inhibitor, neostigmine, was used for system validation through IC50 and Ki values determination by subsequent injections of acetylthiocholine substrate in the presence of neostigmine at increasing concentrations, and the enzyme combined with DTNB in borate-phosphate buffer (30 mM, pH 8.0). The enzymatic product was selectively detected at 412 nm. The validated system was applied to the analysis of seven natural extracts. Conclusions: Results demonstrated promising outcomes for identifying phytotherapeutic agents with potential applications in the prevention of neurodegenerative diseases. This method provides high selectivity and automation, offering a streamlined and effective approach for screening natural matrices containing potential AChE inhibitors.

Ultrafast protein digestion using an immobilized enzyme reactor following high-resolution mass spectrometry analysis for rapid identification of abrin toxin

Abrin toxin, highly dangerous with an estimated human lethal dose of 0.1-1 μg per kg body weight, has attracted much attention regarding criminal and terroristic misuse over the past decade. Therefore, developing a rapid detection method for abrin toxin is of great significance in the field of biosecurity. In this study, based on the specific dissociation method of an immobilized enzyme reactor, the trypsin immobilized reactor Fe3O4@CTS-GA-Try was prepared to replace free trypsin, and the immobilized enzyme digestion process was systematically investigated and optimized by using bovine serum albumin as the simulant of abrin. After 5 min one-step denaturation and reduction, a satisfactory peptide number and coverage were yielded with only 15 s assisted by an ultrasound probe to identify model proteins. Subsequently, abrin was rapidly digested using the established method, resulting in a stable and highly reproducible characteristic peptide number of 39, which can be analyzed by nanoelectrospray ionization coupled with high-resolution mass spectrometry. With the acquisition mode of full MS scan coupled with PRM, not only MS spectroscopy of total abrin peptides but also the corresponding MS/MS spectroscopy of specific abrin peptides can achieve the characteristic detection of abrin toxin and its different isoforms in less than 10 minutes, with high repeatability. This assay provides a universal platform and has great potential for the development of on-site detection and rapid mass spectrometric analysis techniques for macromolecular protein toxins and can further be applied to the integrated detection of chemical and biological agents.

Determination of physicochemical parameters of (bio)molecules and (bio)particles by capillary electromigration methods

The review provides an overview of recent developments and applications of capillary electromigration (CE) methods for the determination of important physicochemical parameters of various (bio)molecules and (bio)particles. These parameters include actual and limiting (absolute) ionic mobilities, effective electrophoretic mobilities, effective charges, isoelectric points, electrokinetic potentials, hydrodynamic radii, diffusion coefficients, relative molecular masses, acidity (ionization) constants, binding constants and stoichiometry of (bio)molecular complexes, changes of Gibbs free energy, enthalpy and entropy and rate constants of chemical reactions and interactions, retention factors and partition and distribution coefficients. For the determination of these parameters, the following CE methods are employed: zone electrophoresis in a free solution or in sieving media, isotachophoresis, isoelectric focusing, affinity electrophoresis, electrokinetic chromatography, and electrochromatography. In the individual sections, the procedures for the determination of the above parameters by the particular CE methods are described.

Screening of Acetylcholinesterase Inhibitors by Capillary Electrophoresis with Oriented-Immobilized Enzyme Microreactors Based on Gold Nanoparticles

A facial and efficient method for the screening of acetylcholinesterase (AChE) inhibitors by capillary electrophoresis was developed. Based on the specific affinity of concanavalin A (Con A) for binding to the glycosyl group of AChE, enzyme molecules were oriented-immobilized on the surface of gold nanoparticles (AuNPs@Con A@AChE). Then, these modified nanoparticles were bounded to the capillary inlet (about 1.0 cm) by electrostatic self-assembly to obtain the oriented-immobilized enzyme microreactor (OIMER). Compared to an IMER with a free enzyme, the peak area of the product obtained by the OIMER increased by 52.6%. The Michaelis-Menten constant (Km) was as low as (0.061 ± 0.003) mmol/L. The method exhibits good repeatability with a relative standard deviation (RSD) of 1.3% for 100 consecutive runs. The system was successfully applied to detect the IC50 values of donepezil and four components from Chinese medicinal plants. This work demonstrates the potential of this method as a low cost, simple, and accurate screening method for other enzyme inhibitors.