Acetylcholinesterase Inhibitors Assay Using Colorimetric pH Sensitive Strips and Image Analysis by a Smartphone

Abstract

Smartphones are widely spread and their usage does not require any trained personnel. Recently, smartphones were successfully used in analytical chemistry as a simple detection tool in some applications. This paper focuses on immobilization of acetylcholinesterase (AChE) onto commercially available pH strips with stabilization in the gelatin membrane. AChE degrades acetylcholine into choline and acetic acid which causes color change of acid-base indicator. Smartphone served as a tool for measurement of indicator color change from red to orange while inhibitors blocked this process. AChE inhibitors were measured with limits of detection, 149 nM and 22.3 nM for galanthamine and donepezil, respectively. Organic solvents were measured for method interferences. Measurement procedure was performed on 3D printed holder and digital photography was evaluated using red-green-blue (RGB) channels. The invented assay was validated to the standard Ellman's test and verified on murine plasma samples spiked with inhibitors. We consider that the assay is fully suitable for practical performance.

Paper-Based Analytical Device for the On-Site Detection of Nerve Agents

“…Paraoxon and dichlorvos (DDVP) were purchased from Sigma-Aldrich Co., Inc. (St. Louis, MO) and Fujifilm Wako Pure Chemical Co., Ltd. (Osaka, Japan), respectively. Organophosphorus compounds were detected using AChE from Electrophorus electricus (electric eel) [Type VI-S, lyophilized powder, 155 or 253 kU/mg (measured by Ellman’s assay); Sigma-Aldrich], ACh (Nacalai Tesque, Inc., Kyoto, Japan), bovine serum albumin (BSA; Sigma-Aldrich), d -(+)-trehalose anhydrous (Tokyo Chemical Industry Co., Ltd., Tokyo, Japan), phenol red (Tokyo Chemical Industry), and 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES; Nacalai Tesque). Interference was evaluated using drug-free urine (from a single donor, Lee Biosolutions, Inc., Maryland Heights, MO) and common liquid hand soap (Lion Corporation, Tokyo, Japan).…”

Rationally Designed Functionalization of Single‐Walled Carbon Nanotubes for Real‐Time Monitoring of Cholinesterase Activity and Inhibition in Plasma

“…On the other hand, the LOD of CHE activity based on the Ellman assay has been reported to be in the range of nm. [ 104,108 ] This indicates that our method for determining CHE activity is comparable to the gold standard Ellman assay, particularly in terms of sensitivity.…”

Biomimetic Membranes with Transmembrane Proteins: State-of-the-Art in Transmembrane Protein Applications

“…AChE degrades acetylcholine into choline and acetic acid, which induces a color change in the acid-base indicator. Kostelnik et al immobilized AChE onto commercially available pH strips with a gelatin membrane and evaluated the color change by using a smartphone [76]. Liu et al and Sun et al used gold nanoparticles to develop colorimetric sensors [77,78], while Hai et al used quantum dots [79] (Figure 5A).…”