Breaking the pH Limitation of Nanozymes: Mechanisms, Methods, and Applications.

Although nanozymes have drawn great attention over the past decade, the activities of peroxidase-like, oxidase-like, and catalase-like nanozymes are often pH dependent with elusive mechanism, which largely restricts their application. Therefore, a systematical discussion on the pH-related catalytic mechanisms of nanozymes together with the methods to overcome this limitation is in need. In this review, various nanozymes exhibiting pH-dependent catalytic activities are collected and the root causes for their pH dependence are comprehensively analyzed. Subsequently, regulatory concepts including catalytic environment reconstruction and direct catalytic activity improvement to break this pH restriction are summarized. Moreover, applications of pH-independent nanozymes in sensing, disease therapy, and pollutant degradation are overviewed. Finally, current challenges and future opportunities on the development of pH-independent nanozymes are suggested. It is anticipated that this review will promote the further design of pH-independent nanozymes and broaden their application range with higher efficiency.

Multienzyme-Like Nanozymes: Regulation, Rational Design, and Application.

Nanomaterials with more than one enzyme-like activity are termed multienzymic nanozymes, and they have received increasing attention in recent years and hold huge potential to be applied in diverse fields, especially for biosensing and therapeutics. Compared to single enzyme-like nanozymes, multienzymic nanozymes offer various unique advantages, including synergistic effects, cascaded reactions, and environmentally responsive selectivity. Nevertheless, along with these merits, the catalytic mechanism and rational design of multienzymic nanozymes are more complicated and elusive as compared to single-enzymic nanozymes. In this review, the multienzymic nanozymes classification scheme based on the numbers/types of activities, the internal and external factors regulating the multienzymatic activities, the rational design based on chemical, biomimetic, and computer-aided strategies, and recent progress in applications attributed to the advantages of multicatalytic activities are systematically discussed. Finally, current challenges and future perspectives regarding the development and application of multienzymatic nanozymes are suggested. This review aims to deepen the understanding and inspire the research in multienzymic nanozymes to a greater extent.

Reference material of Prussian blue nanozymes for their peroxidase-like activity.

Nanozymes with wide applications have rapidly attracted tremendous attention from various fields in the last decade. However, research on the standardization of nanozymes is still lacking. Currently, the accurate evaluation and effective tracing of the enzyme-like activity of nanozymes have become a common concern. This work aims to develop a certified reference material (CRM) of Prussian blue nanozymes (PBNEs) for their peroxidase (POD)-like activity. The homogeneity and stability studies demonstrated that the property value of POD-like activity is consistent across different packing units, and remains unchanged during the one-year validity period of storage in the dark at 4 °C. The certified value of the POD-like activity of the PBNE CRM is assigned as 174 ± 13 U mg-1 (k = 2) by interlaboratory comparison studies and traceable uncertain evaluation. Furthermore, the need for quality control of the POD-like activity of nanozymes was exemplified by comparing the influence of two additional PBNEs on the dry and wet chemical detection of glucose (Glu). As the first quality assurance tool of nanozymes, the PBNE CRM is expected to replace natural horse radish peroxidase (HRP) as an effective benchmark for assessing the analytical method and laboratory competence. In addition, this work also inspires the further standardization of nanozymes.

Prussian Blue Nanozymes Prevent Anthracycline-Induced Liver Injury by Attenuating Oxidative Stress and Regulating Inflammation.

Anthracycline-induced liver injury (AILI) is becoming an increasingly serious and potential clinical complication and is linked to reactive oxygen species (ROS) production and subsequent inflammatory response. Herein, we demonstrated that artificial Prussian blue nanozymes (PBZs) prevented daunorubicin-induced liver injury, a prototype of AILI, by attenuating ROS production and regulating inflammation. PBZs exhibited multienzyme activity and could scavenge ROS and free radicals. At the cellular level, PBZs could effectively eliminate ROS, suppress hepatocyte apoptosis, reduce deoxyribonucleic acid damage, and decrease the levels of inflammatory cytokines and chemokines. According to the results of the in vivo study, pretreatment with PBZs also resulted in a desirable protective effect against AILI, as indicated by both a decrease in biochemical indicator levels and hepatocyte necrosis. PBZs upregulated antioxidative genes by activating the Nrf2 pathway to reduce oxidative stress. Meanwhile, PBZs counteracted the inflammatory response based on the decreased expression levels of myeloperoxidase and F4/80 in the liver. Collectively, our findings indicate that PBZ-based nanotherapy is a novel strategy for protecting against AILI.