Single-atom nanozymes (SAzymes) have drawn ever-increasing attention due to their maximum atom utilization efficiency and enhanced enzyme-like activity. Herein, a facile pyrolysis strategy is reported for the synthesis of the iron–nitrogen–carbon (Fe-N-C) SAzyme using ferrocene trapped within porous zeolitic imidazolate framework-8 (ZIF-8@Fc) as a precursor. The as-prepared Fe-N-C SAzyme exhibited exceptional oxidase-mimicking activity, catalytically oxidizing 3,3′,5,5′-tetramethylbenzidine (TMB) with high affinity (Km) and fast reaction rate (Vmax). Taking advantage of this property, we designed two colorimetric sensing assays based on different interaction modes between small molecules and Fe active sites. Firstly, utilizing the reduction activity of ascorbic acid (AA) toward oxidized TMB (TMBox), a colorimetric bioassay for AA detection was established, which exhibited a good linear range of detection from 0.1 to 2 μM and a detection limit as low as 0.1 μM. Additionally, based on the inhibition of nanozyme activity by the thiols of glutathione (GSH), a colorimetric biosensor for GSH detection was constructed, showing a linear response over a concentration range of 1–10 μM, with a detection limit of 1.3 μM. This work provides a promising strategy for rationally designing oxidase-like SAzymes and broadening their application in biosensing.
Nanozymes, which combine the merits of both nanomaterials and natural enzymes, have aroused tremendous attention as new representatives of artificial enzyme mimics. However, it still remains to be a great challenge to rationally engineer the morphologies and surface properties of nanostructures that lead to the desired enzyme-like activities. Here, we report a DNAprogramming seed-growth strategy to mediate the growth of platinum nanoparticles (PtNPs) on gold bipyramids (AuBPs) for the synthesis of a bimetallic nanozyme. We find that the preparation of a bimetallic nanozyme is in a sequence-dependent manner, and the encoding of a polyT sequence allows the successful formation of bimetallic nanohybrids with greatly enhanced peroxidase-like activity. We further observe that the morphologies and optical properties of T15-mediated Au/Pt nanostructures (Au/T15/Pt) change over the reaction time, and the nanozymatic activity can be tuned by controlling the experimental conditions. As a concept application, Au/T15/Pt nanozymes are used to establish a simple, sensitive, and selective colorimetric assay for the determination of ascorbic acid (AA), alkaline phosphatase (ALP), and the inhibitor sodium vanadate (Na 3 VO 4 ), demonstrating excellent analytical performance. This work provides a new avenue for the rational design of bimetallic nanozymes for biosensing applications.
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