Nanozymes are widely used in various applications as nanosized catalysts for replacing enzymes. An accurate estimation of the catalytic activity of nanozymes in real conditions is critical. In this article, for the first time, we systematically studied the effect of macromolecular molecules co-existing in the real system on the oxidoreductase (peroxidase, oxidase, and catalase)-mimicking nanozymes made of a gold nanoparticle core and a platinum shell, Prussian Blue, Mn₂O₃ and CoO nanoparticles. Comparisons were made with horseradish peroxidase. We distinguished two main mechanisms of the negative impact of macromolecules on nanozyme catalysis—slowed diffusion and surface shielding of nanoparticles. While the first mechanism is typical for enzymes, the second one is specific only for nanozymes. Understanding the mechanisms is essential for developing approaches to reduce the unavoidable impact of macromolecules for various analytical and biomedical applications.

The use of functional nanoparticles as peroxidase-like (POD-like) catalyst has recently become a focus of research in cancer therapy. Phthalocyanine is a macrocyclic conjugated metal ligand, which is expected to achieve a high POD-like catalytic activity, generating free radicals and inhibiting the proliferation of cancer cells. In this paper, we synthesized phthalocyanine nanocrystals with different structures through noncovalent self-assembly confined within micro-emulsion droplets, and manganese phthalocyanine (MnPc) possessing a metal–N–C active center was used as the building block. These nano-assemblies exhibit shape-dependent POD-like catalytic activities, because the emulsifier and MnPc co-mixed assembly reduced the close packing between MnPc molecules and exposed more active sites. The assembly had a water-dispersed nanostructure, which is conducive to accumulation at tumor sites through the enhanced permeability and retention effect (EPR). Because of a highly efficient microenvironmental response, the assembly showed higher catalytic activity only emerged under the acidic tumor-like microenvironment, but caused less damage to normal tissues in biomedical applications. In vivo and in vitro catalytic therapy tests showed excellent anti-tumor effects. This work explored a new way for the application of metal–organic macromolecules such as MnPc as nanozymes for catalytic tumor therapy.

Metal ions play critical roles in chemical, biological, and environmental processes. Various biomolecules have the ability to coordinate with metal ions and form various materials. Nucleobases, nucleosides, and nucleotides, as the essential components of DNA, have emerged as a useful building block for the construction of functional nanomaterials. In recent years, DNA oligonucleotides have also been used for this purpose. We herein review the strategies for the synthesis of soft nanomaterials through the assembly of nucleotides (or DNA) and metal ions to yield various nanoparticles, fibers, and hydrogels. Such coordination methods are simple to operate and can be carried out under ambient conditions. The luminescent, catalytic, and molecular recognition properties of these coordination materials are described with representative recent examples. Their applications ranging from biosensing, enzyme encapsulation, catalysis, templated shell growth to cancer therapy are highlighted. Finally, challenges of this field and future perspectives are discussed.

Developing nanomaterial-based enzyme mimics for DNA cleavage is an interesting challenge and it has many potential applications. Single-layered graphene oxide (GO) is an excellent platform for DNA adsorption. In addition, GO has been employed for photosensitized generation of reactive oxygen species (ROS). Herein, we demonstrate that GO sheets could cleave DNA as a nuclease mimicking nanozyme in the presence of UV or blue light. For various DNA sequences and lengths, well-defined product bands were observed along with photobleaching of the fluorophore label on the DNA. Different from previously reported GO cleavage of DNA, our method did not require metal ions such as Cu²⁺. Fluorescence spectroscopy suggested a high adsorption affinity between GO and DNA. For comparison, although zero-dimensional fluorescent carbon dots (C-dots) had higher photosensitivity in terms of producing ROS, their cleavage activity was much lower and only smeared cleavage products were observed, indicating that the ROS acted on the DNA in solution. Based on the results, GO behaved like a classic heterogeneous catalyst following substrate adsorption, reaction, and product desorption steps. This simple strategy may help in the design of new nanozymes by introducing light.

Nanoparticles and proteins are similar in a number of aspects, and using nanoparticles to mimic the catalytic function of enzymes is an interesting yet challenging task. Impressive developments have been made over the past two decades on this front. The term nanozyme was coined to refer to nanoparticlebased enzyme mimics. To date, many different types of nanozymes have been reported to catalyze a broad range of reactions for chemical, analytical, and biomedical applications. Since chemical reactions happen mainly on the surface of nanozymes, an interesting aspect for investigation is surface modification. In this review, we summarize three types of nanozyme materials catalyzing various reactions with a focus on their surface chemistry. For metal oxides, cerium oxide and iron oxide are discussed as they are the most extensively studied. Then, gold nanoparticles and graphene oxide are reviewed to represent metallic and carbon nanomaterials, respectively. Types of modifications include ions, small molecules, and polymers mainly by physisorption, while in a few cases, covalent modifications were also employed. The functional aspect of such modification is to improve catalytic activity, substrate specificity, and stability. Future perspectives of this field are speculated at the end of this review.