Direct detection of acetylcholinesterase by Fe(HCOO)2.6(OH)0.3. H2O nanosheets with oxidase-like activity on a smartphone platform

Monitoring acetylcholinesterase (AChE) is crucial in clinical diagnosis and drug screening. Traditional methods for detecting AChE usually require the addition of intermediates like acetylthiocholine, which complicates the detection process and introduces interference risks. Herein, we develop a direct colorimetric assay based on alkaline iron formate nanosheets (Fe(HCOO)2.6(OH)0.3·H2O NSs, Fef NSs) for the detection of AChE without any intermediates. The as-prepared Fef NSs exhibit oxidase-like activity, catalyzing the generation of O2·-, 1O2 and ·OH, which leads to a color change from colorless to blue when exposed to 3,3′,5,5′-tetramethylbenzidine. AChE directly inhibits the oxidase-like activity of Fef NSs, resulting in a hindered color reaction, enabling the detection of AChE. The biosensor has a linear detection range of 0.1–30 mU/mL, with a minimum detection limit of 0.0083 mU/mL (S/N = 3), representing a 100-fold improvement in detection sensitivity over the traditional Ellman's method. Satisfactory results were obtained when analyzing real AChE samples. Attractively, a method for the quantitative detection of AChE by a smartphone is established based on the Fef NSs. This method enables instant acquisition of AChE concentrations, achieving real-time visualized detection. TOC Figure. (a) Schematic diagram of the traditional method for detecting AChE. (b) Schematic diagram of the proposed method for detecting AChE. AChE directly inhibits Fef NSs, preventing the generation of free radicals. The detection process utilizes the smartphone platform to directly output AChE concentration. [Display omitted] •Fe(HCOO)2.6(OH)0.3·H2O nanosheet with remarkable oxidase-like activity was prepared through a simple room-temperature reaction method.•Based on these nanosheets, a direct colorimetric biosensor was developed for the sensitive detection of acetylcholinesterase.•The biosensor detected acetylcholinesterase without requiring any intermediate substances, such as acetylthiocholine, overcoming the limitations of traditional methods in this regard.•A smartphone-based approach was developed to instantly obtain the concentration of acetylcholinesterase.