Immobilizing Enzymes on Noble Metal Hydrogel Nanozymes with Synergistically Enhanced Peroxidase Activity for Ultrasensitive Immunoassays by Cascade Signal Amplification

Abstract

Enzyme immobilization plays an essential role in solving the problems of the inherently fragile nature of enzymes. Although prominent stability and reuse of enzymes can be achieved by enzyme immobilization, their bioactivity and catalytic efficiency will be adversely affected. Herein, PdCu hydrogel nanozymes with a hierarchically porous structure were used to immobilize horseradish peroxidase (HRP) to obtain PdCu@HRP. In addition to the improvement of stability and reusability, PdCu@HRP displayed synergistically enhanced activities than native HRP and PdCu hydrogels. Not only the specific interactions between PdCu hydrogel nanozymes and enzymes but also the enrichment of substrates around enzymes by electrostatic adsorption of hydrogels was proposed to expound the enhanced catalytic activity. Accordingly, by taking advantage of the excellent catalytic performance of the PdCu@HRP and the glucose oxidase encapsulated in zeolitic imidazolate framework-8, colorimetric biosensing of the carcinoembryonic antigen via catalytic cascade reactions for achieving signal amplification was performed. The obtained biosensor enhanced the detection sensitivity by approximately 6.1-fold as compared to the conventional HRP-based enzyme-linked immunosorbent assay, demonstrating the promising potential in clinical diagnosis.

Nanozymes: Versatile Platforms for Cancer Diagnosis and Therapy

“…Reproduced with permission from Ref. [109]. Copyright 2021, American Chemical Society mSiO 2 would be recovered, thus catalyzing the color reaction of TMB.…”

“…Human epidermal growth factor receptor 2 (HER2), a well-known breast cancer marker, could be detected using the colorimetric immunoassay with a limit of detection of 1.5 ng/mL, which was much lower than its clinical cutoff value (15 ng mL −1 ). In another work, POD-like PdCu hydrogel nanozymes with a hierarchically porous structure were employed to load the natural enzyme HRP to obtain PdCu@HRP [109]. In addition to the improved stability and reusability, PdCu@HRP showed higher enzymatic activities than HRP and PdCu hydrogels alone due to the synergistic effect.…”

Alendronate-Modified Nanoceria with Multiantioxidant Enzyme-Mimetic Activity for Reactive Oxygen Species/Reactive Nitrogen Species Scavenging from Cigarette Smoke

“…Since the first discovery of peroxidase-mimic activities in magnetic Fe 3 O 4 nanoparticles (NPs), numbers of nanomaterials based on vanadium oxides, , noble metals (Au, Ag, Pt, and Pd), − copper oxides, − carbon, − and manganous − have been reported as antioxidant enzyme mimics. In addition, novel single-atom nanozymes such as the Fe-N-C electrocatalyst have been also discovered with exceptional per­(oxidase)-like activity and widely explored as alternatives to natural enzymes. , Developing nanozymes with biocatalytic properties in a biological context is intriguing to peruse more advanced functions of natural enzymes, such as cost-effectiveness, mass production, stability, and better tolerance toward harsh environments. , Lin et al first reported a copper tannic acid coordination for ROS scavenging in cigarette smoke, opening up an opportunity for the modification of cigarette filters by nanozymes. However, challenges for meeting demanding applications also remained because of its intrinsic selective reaction and limited antioxidant capacity.…”

“…32,33 Developing nanozymes with biocatalytic properties in a biological context is intriguing to peruse more advanced functions of natural enzymes, such as cost-effectiveness, mass production, stability, and better tolerance toward harsh environments. 34,35 Lin et al 36 first reported a copper tannic acid coordination for ROS scavenging in cigarette smoke, opening up an opportunity for the modification of cigarette filters by nanozymes. However, challenges for meeting demanding applications also remained because of its intrinsic selective reaction and limited antioxidant capacity.…”

Trace Iridium as ″Adhesive″ in PtCuIr Aerogels for Robust Methanol Electrooxidation

“…As a new appealing class of cutting-edge nanomaterials, noble metal aerogels (NMAs) are currently enjoying a flourish of extensive developments due to their plentiful interconnected channels, large surface area, and extremely low density. − Combining three-dimensional (3D) porous network architectures, excellent conductivity, and catalytic performance of noble metals, NMAs have caught tremendous attention in sensing, self-propulsion devices, and electrocatalysis. − The porous hybrid nanostructures can supply abundant free and open channels for fast electron transfer and mass transport, and the interconnected NWAs with anisotropic structures provide numerous active sites derived from high index facets, grain boundaries, kinetic steps, etc. Besides, self-supported properties can alleviate the support corrosion problem, which contributes to the enhancement of stability .…”