Colorimetric biosensing of organophosphate pesticides using enzymatic nanoreactor built on zeolitic imdiazolate-8

Abstract

A nanoreactor (NR) was synthesized by encapsulating acetylcholinesterase (AChE) in zeolitic imidazolate framework (ZIF)-8 (AChE@ZIF-8 NR). The catalytic activity of the NR was tested for the hydrolysis of acetylthiocholine chloride (ATCh) based on the Ellman’s assay to yield a characteristic yellow color at a maximum wavelength (λmax) of 412 nm. The catalytic activity of AChE@ZIF-8 NR showcased noticeable enhancements in maximum reaction rate (νmax: 1.25 × 10−12 kat) and low Michaelis-Menton constant (Km: 0.05 mM (10 ppm)). The NR-based hydrolysis of ATCh was inhibited in the presence of each of all seven types of organophosphate pesticides (malathion (MAL), methyl parathion (MP), glyphosate (GLY), glufosinate (GLU), chlorpyrifos (CPF), dichlorvos (DCV), and paraoxon (PAR)) selected in this study. The limit of detection (LOD) values for GLY, GLU, and MAL were estimated almost identically as 10−5 ppb. However, their limit of quantification (LOQ) was slightly distinguished as 0.05, 0.01, and 0.05 ppb, respectively. The NR retained 46% of its activity over the course of 5 cycles of sequential activation and MAL-induced inhibition. In comparison to the other reported studies, our approach provides a rapid means for sensing of OPs with appreciable stability, enhanced recyclability, and facile observation.