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Single-atom catalysts (SACs), as homogeneous catalysts, have been widely explored for chemical catalysis. However, few studies focus on the applications of SACs in enzymatic catalysis. Herein, we report that a zinc-based zeolitic-imidazolate-framework (ZIF-8)-derived carbon nanomaterial containing atomically dispersed zinc atoms can serve as a highly efficient single-atom peroxidase mimic. To reveal its structure-activity relationship, the structural evolution of the single-atom nanozyme (SAzyme) was systematically investigated. Furthermore, the coordinatively unsaturated active zinc sites and catalytic mechanism of the SAzyme are disclosed using density functional theory (DFT) calculations. The SAzyme, with high therapeutic effect and biosafety, shows great promises for wound antibacterial applications.

Single-atom nanozymes (SAzymes) represent a new research frontier in the biomedical fields. The rational design and controllable synthesis of SAzymes with well-defined electronic and geometric structures are essential for maximizing their enzyme-like catalytic activity and therapeutic efficacy but remain challenging. Here, a melamine-mediated pyrolysis activation strategy is reported for the controllable fabrication of iron-based SAzyme containing five-coordinated structure (FeN

Dual phototherapy, including photodynamic therapy (PDT) and photothermal therapy (PTT), has shown a great prospect in cancer treatment. However, its therapeutic effect is restricted by the depth of light penetration in tissue and tumor hypoxia environment. Herein, inspired by the specific response of nanozymes to the tumor microenvironment (TME), a simple and versatile nanozyme-mediated synergistic dual phototherapy nanoplatform (denoted as FePc/HNCSs) is constructed using hollow nitrogen-doped carbon nanospheres (HNCSs) and iron phthalocyanine (FePc). FePc/HNCSs simultaneously exhibit peroxidase (POD)- and catalase (CAT)-like activities, which not only can convert endogenous hydrogen peroxide (H2 O2 ) into highly toxic hydroxyl radicals (•OH) for catalytic therapy, but also decompose H2 O2 to oxygen (O2 ) to enhance O2 -dependent PDT. In addition, their enzyme-like activities are significantly enhanced under light irradiation. Combining with the excellent photothermal effect, FePc/HNCSs realize a high tumor inhibition rate of 96.3%. This strategy opens a new horizon for exploring a more powerful tumor treatment nanoplatform.

The performances of catalysts are highly dependent on their crystallinities. It is a significant challenge to successively manipulate the crystallinities of noble metal nanocatalysts due to the strong metallic bonds, especially under ambient conditions. Herein, a post-crystallization approach is developed for successive control of the crystallinity of Pd nanosheets via selective oxidation etching of the amorphous domains. This strategy can be extended to crystallize other Pd and Ru nanomaterials. By carefully modulating the crystallinity of Pd nanosheets, the time for the complete conversion of 4-nitrostyrene via hydrogenation is reduced by 20 times. Also, crystallization can turn the selectivity of the products and improve the stability of Pd nanosheets. These findings may advance the crystal engineering of metal nanomaterials for wide applications.

Nanozyme is defined as a nanomaterial‐based artificial enzyme. It has rapidly attracted interest and been regarded as a promising alternative to natural enzymes due to its low cost, high stability, and high activity. Many researchers have recently paid attention to the optical properties of nanozymes and have found a variety of nanozymes with excellent photoactivity, called photo‐responsive nanozymes. In this minireview, we briefly introduce the mechanisms of photo‐responsive nanozymes, especially for the relationship between the enzyme‐like activity and photoactivity. Some activity regulation strategies for improving the performance of photo‐responsive nanozymes are also summarized. Moreover, the synergy of enzyme‐like activity and photoactivity in biomedical applications will also be discussed, including cancer therapy, antibacteria, and biological detection. We believe this minireview will be of great significance for understanding the optical properties of nanozymes and applying them in biomedicine.

Nanozyme-based tumor catalytic therapy has attracted widespread attention in recent years. However, its therapeutic outcomes are diminished by many factors in the tumor microenvironment (TME), such as insufficient endogenous hydrogen peroxide (H2 O2 ) concentration, hypoxia, and immunosuppressive microenvironment. Herein, an immunomodulation-enhanced nanozyme-based tumor catalytic therapy strategy is first proposed to achieve the synergism between nanozymes and TME regulation. TGF-β inhibitor (TI)-loaded PEGylated iron manganese silicate nanoparticles (IMSN) (named as IMSN-PEG-TI) are constructed to trigger the therapeutic modality. The results show that IMSN nanozyme exhibits both intrinsic peroxidase-like and catalase-like activities under acidic TME, which can decompose H2 O2 into hydroxyl radicals (•OH) and oxygen (O2 ), respectively. Besides, it is demonstrated that both IMSN and TI can regulate the tumor immune microenvironment, resulting in macrophage polarization from M2 to M1, and thus inducing the regeneration of H2 O2 , which can promote catalytic activities of IMSN nanozyme. The potent antitumor effect of IMSN-PEG-TI is proved by in vitro multicellular tumor spheroids (MCTS) and in vivo CT26-tumor-bearing mice models. It is believed that the immunomodulation-enhanced nanozyme-based tumor treatment strategy is a promising tool to kill cancer cells.