Search

Iron-anchored nitrogen/doped carbon single-atom nanozymes (Fe-N/C), which possess homogeneous active sites and adjustable catalytic environment, represent an exemplary model for investigating the structure-function relationship and catalytic activity. However, the development of pyrolysis-free synthesis technique for Fe-N/C with adjustable enzyme-mimicking activity still presents a significant challenge. Herein, Fe-N/C anchored three carrier morphologies were created via a pyrolysis-free approach by covalent organic polymers. The peroxidase-like activity of these Fe-N/C nanozymes was regulated via the pores of the anchored carrier, resulting in varying electron transfer efficiency due to disparities in contact efficacy between substrates and catalytic sites within diverse microenvironments. Additionally, a colorimetric sensor array for identifying antioxidants was developed: (1) the Fe-N/C catalytically oxidized two substrates TMB and ABTS, respectively; (2) the development of a colorimetric sensor array utilizing oxTMB and oxABTS as sensing channels enabled accurate discrimination of antioxidants such as ascorbic acid (AsA), glutathione (GSH), cysteine (Cys), gallic acid (GA), and caffeic acid (CA). Subsequently, the sensor array underwent rigorous testing to validate its performance, including assessment of antioxidant mixtures and individual antioxidants at varying concentrations, as well as target antioxidants and interfering substances. In general, the present study offered valuable insights into the active origin and rational design of nanozyme materials, and highlighting their potential applications in food analysis., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

Single-atom nanozymes have garnered significant attention due to their exceptional atom utilization and ability to establish well-defined structure-activity relationships. However, conventional pyrolytic synthesis methods pose challenges such as high energy consumption and random local environments at the active sites, while achieving non-pyrolytic synthesis of single-atom nanozymes remains a formidable technical hurdle. The present study focuses on the synthesis of laccase-like iron-based single-atom nanozymes (Fe-SAzymes) using a non-pyrolysis method facilitated by microwave irradiation. Under low iron loading conditions, Fe-SAzymes exhibited significantly enhanced laccase activity (12.1 U/mg), surpassing that of laccase by 24-fold. Moreover, Fe-SAzymes demonstrated efficient catalytic oxidation of epinephrine (EP), enabling its colorimetric detection. Owing to the remarkable laccase activity of Fe-SAzymes, the conventional nanozymes EP detection time was reduced from 60 min to 20 min, with an impressive low detection limit as low as 2.95 μM. In addition, an ultra-sensitive fluorescence method for EP detection was developed using the internal filter effect of EP oxidation products and CDs combined with carbon dots probe. The detection limit of fluorescence method was only 0.39 μM. Therefore, an visual, fast, and highly sensitive dual-mode EP detection strategy has great potential in the clinical diagnostic industry., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

We select the peptide mimics of blood group A antigen by a monoclonal anti-A from a phage display 15-mer peptide library. Monoclonal anti-A was used in biopanning a phage display 15-mer peptide library. After four rounds of panning, ELISA was carried out to confirm the positive phage clones. The exogenous DNAs of the positive phages were sequenced and the corresponding amino acid sequences were deduced. Both the synthesized peptide and the phage clones were used to bind to anti-A in competitive ELISA. Erythrocyte agglutination inhibition tests were carried out to determine the mimic ability of the free synthesized peptide to the natural blood group A antigen. Computer softwares were used to simulate the interaction between the peptide and anti-A. After four rounds of biopanning, the eluted phage reached an enrichment of approximately 1600 times. Thirty-seven phage clones were chosen randomly and amplified. There were eleven clones that interacted specifically with anti-A in ELISA. DNA sequencing of the inserted oligonucleotide revealed that nine clones present a same peptide - TRWLVYFSRPYLVAT (named TRW) and each of the other two clones presented a different peptide. The synthesized free peptide TRW could inhibit the interaction of both phage displayed peptide and group A red blood cell with anti-A in competitive ELISA and hemagglutination inhibition test. Both the peptide TRW and the natural group A antigen were docked into a same cavity of anti-A in a computer simulation assay. The results indicate that peptide TRW can mimic blood group A antigen. It may be used as a proxy of natural blood group A antigen in clinical application., (© 2013.)