Structure Defect Tuning of Metal–Organic Frameworks as a Nanozyme Regulatory Strategy for Selective Online Electrochemical Analysis of Uric Acid

Abstract

Nanozymes have been designed to address the limitations of high cost and poor stability involving natural enzymes in analytical applications. However, the catalytic efficiency of the nanozyme still needs to be improved so that it can meet the selectivity and stability requirements of accurate biomolecule analysis. Here, we presented structure defects of metal−organic frameworks (MOFs) as a tuning strategy to regulate the catalytic efficiency of artificial nanozymes and investigated the roles of defects on the catalytic activity of oxidase-like MOFs. Structural defects were introduced into a novel Co-containing zeolitic imidazolate framework with gradually loosened morphology (ZIF-L-Co) by doping cysteine (Cys). It was found that with the increase in defect degree, the properties of materials such as ascorbate oxidase-like, glutathione oxidase-like, and laccase-like were obviously enhanced by over 5, 2, and 3 times, respectively. In-depth structural investigations indicate that the doping of sulfur inducing structural defects which may destroy the equilibrium state between cobalt and nitrogen in 2-methylimidazole and distort the crystal lattice, thereby enhancing the adsorption of oxygen and thus promoting the oxidase-like activity. The ZIF-L-Co-10 mg with enhanced ascorbate oxidase-and laccase-like activity was loaded into a microreactor and integrated into an online electrochemical system (OECS) in the upstream of the detector. This nanozyme-based microreactor can completely remove ascorbic acid, dopamine, and 3,4-dihydroxyphenylacetic acid which are the main interference toward uric acid (UA) electrochemical measurement, and the ZIF-L-Co-10 mg Cys-based OECS system is capable of continuously capturing UA change in rat brain following ischemia−reperfusion injury. Structure defect tuning of ZIF-L-Co not only provides a new regulatory strategy for artificial nanozyme activity but also provides a critical chemical platform for the investigation of UA-related brain function and brain diseases.

Sensitive colorimetric assay of T4 DNA ligase by the oxidase nanozyme of LaMnO3.26 coupled with a hyperbranched amplification reaction

“…3C), indicating the production of 1 O 2 in the system. 5,5-Dimethyl-1-pyrroline-N-oxide (DMPO) was used to trap O 2 •− in the system, 32,33 and the resulting DMPO-O 2…”

“…3C), indicating the production of 1 O 2 in the system. 5,5-Dimethyl-1-pyrroline- N -oxide (DMPO) was used to trap O 2 ˙ − in the system, 32,33 and the resulting DMPO-O 2 ˙ − showed a spectrum with a characteristic peak intensity of 1 : 1 : 1 : 1 in the ESR spectra (Fig. 3D), indicating the production of O 2 ˙ − in the system.…”

Metal–Organic Frameworks‐Based Nanoplatforms for the Theranostic Applications of Neurological Diseases

“…Ren et al utilized an adjustable structure defect method to construct a MOF-based biosensor for selective electrochemical biosensing of uric acid. [127] Specifically, cysteine (Cys) was introduced to a new Co-containing ZIF (ZIF-L-Co) as a structure defect regulator. Catalytic activities, such as glutathione oxidase-like, ascorbate oxidase-like, and laccase-like catalytic properties of ZIF-L-Co-10 mg, were obviously improved over 2, 5, and 3 times, respectively.…”

“…Amperometric responses of different UA concentrations (G), and dynamic changes of the striatum UA level in the rat brain suffering from cerebral ischemia (H) with the online system. Reproduced with permission [127]. Copyright 2021, American Chemical Society.…”

Recent Advances on Nanozyme‐based Electrochemical Biosensors

“…And the change of DOPAC in the brain microdialysate before and after ischemia of the rats’ brain was successfully monitored (Figure 5) [68]. In addition to oxidizing the target analytes, oxidase‐like nanozymes can improve the selectivity of electrochemical biosensors by oxidizing some potential interference species [71]. Co‐containing zeolitic imidazolate frameworks were developed with excellent ascorbate oxidase‐ and laccase‐like activity.…”