Electrocatalytic microelectrode detectors for choline and acetylcholine following separation by capillary electrophoresis

An overview of recent analysis and detection of acetylcholine

Acetylcholine (ACh), the major neurotransmitter secreted by cholinergic neurons, is widely found in the peripheral and central nervous systems, and its main function is to complete the transmission of neural signals. When cholinergic neurons are impaired, the synthesis and decomposition of ACh are abnormal and the neural signalling transition is blocked. To some extent, the concentration changes of ACh reflects the occurrence and development of many kinds of nervous system diseases, such as Alzheimer's disease, Parkinson's disease, Myasthenia gravis and so on. Thus, researches of the physiological and pathological roles and the tracking of the concentration changes of ACh in vivo are significant to the prevention and treatment of these diseases. In the paper, the pathophysiological functions and the comprehensive research progress on detection methods of ACh are summarized. Specifically, the latest research and related applications of the optical and electrochemical biosensors are described, and the future development directions and challenges are prospected, which provides a reference for the detection and applications of ACh.

Bioguided Isolation and Structure Identification of Acetylcholinesterase Enzyme Inhibitors from Drynariae Rhizome

Drynariae Rhizome, widely distributed in southern China, was clinically used as a traditional treatment for cognitive disfunction, such as Alzheimer's disease (AD). The aim of our work was to evaluate the AChE inhibition activities of extracts of Drynariae Rhizome and pure compounds using a bioguided fractionation procedure. The classical approach for screening potential AChE inhibitors was developed by Ellman. However, the background color of compounds or herb extracts remained uncertain and frequently interfered with the detection of the secondary reaction, thereby easily yielding false positive or false negative results. Here, a high-throughput assay monitoring the transformation of iodized choline from iodized acetylcholine catalyzed by AChE was established based on UPLC-MS/MS. The bioguided fractionation of the extract using this method resulted in the isolation of eight AChE inhibitory flavonoids, including naringenin, eriodictyol, kaempferol, luteolin, astragalin, luteolin-7-O-β-D-glucoside, naringin, and neoeriocitrin, with the IC₅₀ values of 3.81 ± 0.21 μM, 7.19 ± 0.62 μM, 11.09 ± 1.02 μM, 17.26 ± 0.23 μM, 18.24 ± 2.33 μM, 17.13 ± 1.02 μM, 26.4 ± 1.17 μM, and 22.49 ± 1.25 μM. It is assumed that the identified flavonoids contribute to the AChE inhibition activity of Drynariae Rhizome. These results are in agreement with the traditional uses of Drynariae Rhizome for AD.

A colorimetric sensor of H2O2 based on Co3O4–montmorillonite nanocomposites with peroxidase activity

Schematic of the colorimetric detection of H₂O₂ catalyzed using Co₃O₄–MMT NPs.

Synthesis and characterization of luminescent cadmium selenide/zinc selenide/zinc sulfide cholinomimetic quantum dots

Luminescent quantum dots conjugated with highly selective molecular recognition ligands are widely used for targeting and imaging biological structures. In this paper, water soluble cholinomimetic cadmium selenide (core), zinc selenide/zinc sulfide (shell) quantum dots were synthesized for targeting cholinergic sites. Cholinomimetic specificity was incorporated by conjugation of the quantum dots to an aminated analogue of hemicholinium-15, a well known competitive inhibitor of the high affinity choline uptake transporter. Detailed evaluation of the nanocrystal synthesis and characterization of the final product was conducted by (1)H and (31)P NMR, absorption and emission spectroscopy, as well as transmission electron microscopy.

Electrochemical methods in conjunction with capillary and microchip electrophoresis

Electromigrative techniques such as capillary and microchip electrophoresis (CE and MCE) are inherently associated with various electrochemical phenomena. The electrolytic processes occurring in the buffer reservoirs have to be considered for a proper design of miniaturized electrophoretic systems and a suitable selection of buffer composition. In addition, the control of the electroosmotic flow plays a crucial role for the optimization of CE/MCE separations. Electroanalytical methods have significant importance in the field of detection in conjunction with CE/MCE. At present, amperometric detection and contactless conductivity detection are the predominating electrochemical detection methods for CE/MCE. This paper reviews the most recent trends in the field of electrochemical detection coupled to CE/MCE. The emphasis is on methodical developments and new applications that have been published over the past five years. A rather new way for the implementation of electrochemical methods into CE systems is the concept of electrochemically assisted injection which involves the electrochemical conversions of analytes during the injection step. This approach is particularly attractive in hyphenation to mass spectrometry (MS) as it widens the range of CE-MS applications. An overview of recent developments of electrochemically assisted injection coupled to CE is presented.

Recent progress for capillary electrophoresis with electrochemical detection

Capillary electrophoresis (CE) is an attractive technique in separation science because of its high separation performance, short analysis time and low cost. Electrochemical detection (EC) is a powerful tool for CE because of its high sensitivity. In this review, developments of CE-EC from 2008 to August, 2011 are reviewed. We choose papers of innovative and novel results to demonstrate the newest and most important progress in CE-EC.

Fieldable flow injection analysis system with chemiluminescence detection capable of quantifying

We developed a highly sensitive biosensor for quantifying acetylcholine (ACh) using flow injection analysis system with 1,1'-oxalyldiimidazole chemiluminescence (ODI-CL) detection designed based on the principle of liquid core waveguide. ACh in Tris-HCl (pH 8.5) was incubated with the mixture of 1.0 U/ml acetylcholinesterase, 0.5 U/ml choline oxidase, 0.04 U/ml horseradish peroxidase, and 1.0 μM Amplex Red in PBS (pH 7.4) for 15 min at room temperature. The concentration of resorufin formed from the consecutive enzyme reactions was proportional to the concentration of ACh in analytical sample. The dynamic range of linear calibration curve (y = 12444x + 11617, R2 = 0.998) for the quantification of ACh using the biosensor with ODI CL detection was 0.7∼11.3 μM. The limit of detection (LOD = background noise + 3σ) of the biosensor was as low as 0.14 μM. Based on the results of recovery test and linearity study, finally, we confirmed that FIA system with ODI CL detection is accurate, precise, and reproducible.