Pore-Environment-Dependent Photoresponsive Oxidase-Like Activity in Hydrogen-Bonded Organic Frameworks

Mimicking the bioactivity of native enzymes through synthetic chemistry is an efficient means to advance the biocatalysts in a cell-free environment, however, remains long-standing challenges. Herein, we utilize structurally explicit hydrogen-bonded organic frameworks (HOFs) to mimic photo-responsive oxidase, and uncover the important role of pore environments on mediating oxidase-like activity by means of constructing isostructural HOFs. We discover that the HOF pore with suitable geometry can stabilize and spatially organize the catalytic substrate into a favorable catalytic route, as with the function of the native enzyme pocket. Based on the desirable photo-responsive oxidase-like activity, a visual and sensitive HOFs biosensor is established for the detection of phosphatase, an important biomarker of skeletal and hepatobiliary diseases. This work demonstrates that the pore environments significantly influence the nanozymes' activity in addition to the active center.

Single-atom Nanozymes for Biomedical Applications： Recent Advances and Challenges

Nanozymes have received extensive attention in the fields of sensing and detection, medical therapy, industry, and agriculture thanks to the combination of the catalytic properties of natural enzymes and the physicochemical properties of nanomaterials, coupled with superior stability and ease of preparation. Despite the promise of nanozymes, conventional nanozymes are constrained by their oversized size and low catalytic capacity in sophisticated practical application environments. single-atom nanozymes (SAzymes) were characterized as nanozymes with high catalytic efficiency by uniformly distributed single atoms as catalysis sites, thus effectively addressing the defects of conventional nanozymes. This paper reviews the activity improvement scheme and catalytic mechanism of SAzymes and highlights the latest research progress of SAzymes in the fields of biomedical sensing and therapy. Eventually, the challenges and future directions of SAzymes are discussed in this paper.

Magnetic nanomaterials with unique nanozymes-like characteristics for colorimetric sensors: A review

Colorimetric sensors for the rapid detection of numerous analytes have been widely applied in many fields such as biomedicine, food industry and environmental science due to their highly sensitive and selective response, easy operation and visual identification by naked eyes. In this review, the recent progress of the colorimetric sensors based on the magnetic nanomaterials with unique nanozymes-like catalytic activity (magnetic nanozyme) and their colorimetric sensing applications are presented. Emerging magnetic nanozyme-based colorimetric sensors, such as metal oxide/sulfides-based, metal-based, carbon-based, and aptamer-conjugated magnetic nanomaterials, offer many desirable features for target analytes detection. And due to the unique nanoscale physical-chemical properties, magnetic nanozymes have been used to mimic the catalytic activity of natural enzymes such as peroxidases, oxidases and catalases. This review also highlights the catalytic mechanisms of enzyme-like reactions, and promising colorimetric sensing system for the detection of chemical compounds like H₂O₂, pesticide, ascorbic acid, dopamine, tetracyclines, perfluorooctane sulfonate, phenolic compounds, heavy metal ion and sulfite have been deeply discussed. In addition, the remaining challenges and future directions in utilizing magnetic nanozyme for colorimetric sensors are addressed.

Natural Polyphenol-Vanadium Oxide Nanozymes for Synergistic Chemodynamic/Photothermal Therapy

The selection of suitable nanozymes with easy synthesis, tumor specificity, multifunction, and high therapeutics is meaningful for tumor therapy. Herein, a facile one-step assembly approach was employed to successfully prepare a novel kind of natural polyphenol tannic acid (TA) hybrid with mixed valence vanadium oxide nanosheets (TA@VO_x NSs). In this system, VO_x is assembled with TA through metal-phenolic coordination interaction to both introduce superior peroxidase-like activity and high near infrared (NIR) absorption owing to partial reduction of vanadium from V⁵⁺ to V⁴⁺ . The presence of mixed valence vanadium oxide in TA@VO_x NSs is proved to be the key for the catalytic reaction of hydrogen peroxide (H₂ O₂ ) to ^. OH, and the corresponding catalytic mechanism of H₂ O₂ by TA@VO_x NSs is proposed. Benefitting from such peroxidase-like activity of TA@VO_x NSs, the overproduced H₂ O₂ of the tumor microenvironment allows the realization of tumor-specific chemodynamic therapy (CDT). As a valid supplement to CDT, the NIR absorption enables TA@VO_x NSs to have NIR light-mediated conversion ability for photothermal therapy (PTT) of cancers. Furthermore, in vitro and in vivo experiments confirmed that TA@VO_x NSs can effectively inhibit the growth of tumors by synergistic CDT/PTT. These results offer a promising way to develop novel vanadium oxide-based nanozymes for enhanced synergistic tumor-specific treatment.

Water dispersed two-dimensional ultrathin Fe(iii)-modified covalent triazine framework nanosheets: peroxidase like activity and colorimetric biosensing applications

Peroxidase mimics have attracted increasing attention as emerging artificial enzymes due to their promising applications in many fields, including bionanotechnology, sustainable chemistry, and environmental remediation. Although many types of peroxidase mimics have been successfully exploited in the past decade, the development of an innovative peroxidase mimic that does not contain noble metals, but exhibits remarkable peroxidase-like activity and low cytotoxicity still remains a major challenge in this field. Herein, we present a bulk covalent triazine framework cleavage and metal atom anchoring strategy for the synthesis of iron-modified two-dimensional covalent triazine frameworks (2D Fe-CTFs) that demonstrate excellent peroxidase-like activity. Furthermore, three kinds of colorimetric sensing platforms for sarcosine, ochratoxin A, and fluoride ions were constructed based on the intrinsic peroxidase-like activity, salt-induced coagulation, and coordination competition of the 2D Fe-CTF, respectively. This work may provide a new synthetic method for peroxidase mimics that can be used in various colorimetric sensors.