A Sensitive and Selective Colorimetric Method Based on the Acetylcholinesterase-like Activity of Zeolitic Imidazolate Framework-8 and Its Applications

Abstract

In this study, a simple colorimetric method was established to detect copper ion (Cu2+), sulfathiazole (ST), and glucose based on the acetylcholinesterase (AChE)-like activity of zeolitic imidazolate framework-8 (ZIF-8). The AChE-like activity of ZIF-8 can hydrolyze acetylthiocholine chloride (ATCh) to thiocholine (TCh), which will further react with 5,5′-dithiobis (2-nitrobenzoic acid) (DTNB) to generate 2-nitro-5-thiobenzoic acid (TNB) that has a maximum absorption peak at 405 nm. The effects of different reaction conditions (buffer pH, the volume of ZIF-8, reaction temperature and time, and ATCh concentration) were investigated. Under the optimized conditions, the value of the Michaelis-Menten constant (Km) is measured to be 0.83 mM, which shows a high affinity toward the substrate (ATCh). Meanwhile, the ZIF-8 has good storage stability, which can maintain more than 80.0% of its initial activity after 30 days of storage at room temperature, and the relative standard deviation (RSD) of batch-to-batch (n = 3) is 5.1%. The linear dependences are obtained based on the AChE-like activity of ZIF-8 for the detection of Cu2+, ST, and glucose in the ranges of 0.021–1.34 and 5.38–689.66 µM, 43.10–517.24 µM, and 0.0054–1.40 mM, respectively. The limit of detections (LODs) are calculated to be 20.00 nM, 9.25 µM, and 5.24 µM, respectively. Moreover, the sample spiked recoveries of Cu2+ in lake water, ST in milk, and glucose in strawberry samples were measured, and the results are in the range of 98.4–115.4% with the RSD (n = 3) lower than 3.3%. In addition, the method shows high selectivity in the real sample analysis.

Preparation of Alcohol Dehydrogenase–Zinc Phosphate Hybrid Nanoflowers through Biomimetic Mineralization and Its Application in the Inhibitor Screening

“…For an enzyme kinetic reaction, the K m (Michaelis–Menten constant) is an important parameter that can reflect the affinity between the substrate and enzyme, which is calculated through the Lineweaver–Burk Equation (1) [ 52 ]. where [S] is the concentration of the substrate (β-NAD + ), V max and V are the maximum and reaction rate of the enzyme reaction, respectively.…”

“…IC 50 was measured by varying the concentration of ranitidine (0.2–0.8 mM) with a fixed β-NAD + concentration at 3 mM. The % of inhibition ( I %) can be calculated through Equation (2) [ 52 ]: where A i and A 0 are the absorbances of the reaction product with and without the inhibitor, respectively. I (%) is the inhibitory percentage.…”

“…For an enzyme kinetic reaction, the K m (Michaelis-Menten constant) is an important parameter that can reflect the affinity between the substrate and enzyme, which is calculated through the Lineweaver-Burk Equation (1) [52].…”

“…IC 50 was measured by varying the concentration of ranitidine (0.2-0.8 mM) with a fixed β-NAD + concentration at 3 mM. The % of inhibition (I%) can be calculated through Equation ( 2) [52]:…”

Applications of magnetic solid‐phase extraction in the sample preparation of natural product analysis (2020–2023)

“…ZIF‐67 is one of the most representative ZIFs, which has served as the SPE adsorbent to enrich different small‐molecule compounds, including antibiotics [27], insecticides [28], and dyes [29], on account of its extraordinary chemical and thermal stability in water, weakly acidic or alkaline solutions. In our previous study, through a single‐step coating method, a core‐shell‐derived structural magnetic ZIF‐67 (Fe 3 O 4 ‐COOH@ZIF‐67) nanocomposite was synthesized for the MSPE of theophylline (TP) [30]. After the characterization of MNPs and the optimization of adsorption and elution process conditions, the adsorption kinetics of TP on Fe 3 O 4 ‐COOH@ZIF‐67 were found to follow pseudo‐second‐order kinetics.…”