Magnetoresponsive nanozyme: magnetic stimulation on the nanozyme activity of iron oxide nanoparticles

Nanozymes and Their Potential Roles in the Origin of Life

The origin of life has long been a central scientific challenge, with various hypotheses proposed. The chemical evolution, which supposes that inorganic molecules can transform into organic molecules and subsequent primitive cells, laid the foundation for modern theories. Inorganic minerals are believed to play crucial catalytic roles in the process. However, the harsh reaction conditions of inorganic minerals hinder the accumulation of organic molecules, preventing the efficient transition from inorganic molecules to biomacromolecules. Given the inherent physicochemical properties and enzyme-like activities, this study proposes that nanozymes, nanomaterials with enzyme-like activities, act as efficient prebiotic catalysts in the origin of life. This hypothesis is based on the following: First, unlike traditional minerals, nanominerals can catalyze organic synthesis under milder conditions. Second, nanominerals can not only protect biomolecules from radiation damage but also catalyze polymerization reactions to form functional biomacromolecules and further lipid vesicles. More importantly, nanominerals are abundant in terrestrial and extraterrestrial environments. This perspective will systematically discuss the potential roles of nanozymes in the emergence of life based on the functions of minerals and the characteristics of nanozymes. We hope the research on nanozymes and the origin of life will bridge the gap between inorganic precursors and biomolecules under primitive environments.

Iron oxide nanozymes as versatile analytical tools: an overview of their application as detection technique

Iron oxide nanozymes (IONzymes) have become fundamental components in various analyte detection methodologies such as colorimetric, electrochemistry, fluorescence and luminescence. Their tunability, stability and the possibility of modification, alongside their ability to mimic the catalytic properties of natural enzymes like peroxidase, render them invaluable in analytical chemistry. This review explores the diverse applications of IONzymes across analytical chemistry, with a particular highlighting on their roles in different detection techniques and their potential in biomedical and diagnostic applications. This information would be valuable for researchers and practitioners in the fields of analytical chemistry, biochemistry, biotechnology and materials science who are interested in applying IONzymes in their work. In essence, this review article on iron oxide nanozymes in analytical chemistry would serve as a valuable resource for researchers, educators and industry professionals, offering insights, guidance and inspiration for further study and application of this promising class of nanomaterials.

Multienzyme-mimic Fe single-atom nanozymes regulate infection microenvironment for photothermal-enhanced catalytic antibacterial therapy

The rational design of nanozymes with highly efficient reactive oxygen species (ROS) generation to overcome the resistant infection microenvironment still faces a significant challenge. Herein, the highly active Fe single-atom nanozymes (Fe SAzymes) with a hierarchically porous nanostructure were prepared through a colloidal silica-induced template method. The proposed Fe SAzymes with satisfactory oxidase (OD)-like and peroxidase (POD)-like activity can transform O2 and H2O2 to superoxide anion free radical (•O2-) and hydroxyl radical (•OH), which possess an excellent bactericidal effect. Also, the glutathione peroxidase (GPX)-like activity of Fe SAzymes can consume glutathione in the infection microenvironment, thus facilitating ROS generation to enhance the sterilization effect. Besides, the intrinsic photothermal effect of Fe SAzymes further significantly boosts the enzyme-like activity to generate much more reactive oxygen species for efficient antibacterial therapy. Accordingly, both in vitro and in vivo results indicate that the Fe SAzymes with synergistically photothermal-catalytic performances exhibit satisfactory antibacterial effects and biocompatibility. This work provides new insights into designing highly efficient SAzymes for effective sterilization applications by an amount of ROS generation.

Intracellular Magnetic Hyperthermia Sensitizes Sorafenib to Orthotopic Hepatocellular Carcinoma Via Amplified Ferroptosis

Sorafenib (SRF) is recognized as the primary treatment for hepatocellular carcinoma (HCC), yet the emergence of SRF resistance in many HCC patients results in unfavorable outcomes. Enhancing the efficacy of SRF in HCC remains a significant challenge. SRF works in inducing ferroptosis, a form of cell death, in cancer cells through the inhibition of glutathione peroxidase 4 (GPX4). The effectiveness of this process is limited by the low levels of cellular iron and reactive oxygen species (ROS). A promising approach to circumvent this limitation is the use of intracellular magnetic hyperthermia (MH) mediated by magnetic iron oxide nanomaterials (MIONs). When MIONs are subjected to an alternating magnetic field (AMF), they heat up, enhancing the Fenton reaction, which in turn significantly increases the production of ROS within cells. In this study, we explore the capability of MH facilitated by high-performance ferrimagnetic vortex-domain iron oxide nanoring (FVIO) to enhance the effectiveness of SRF treatment in HCC. The increased iron uptake facilitated by FVIO significantly enhances the sensitivity of HCC cells to SRF-induced ferroptosis. Moreover, the nanoheat generated by FVIO in response to an AMF further elevates ROS levels and stimulates lipid hydroperoxide (LPO) production and GPX4 inactivation, thereby intensifying ferroptosis. Both in vitro and in vivo animal studies demonstrate that combining FVIO-mediated MH with SRF significantly reduces cell viability and inhibits tumor growth, primarily through enhanced ferroptosis, with minimal side effects. The effectiveness of this combination therapy is affected by the ferroptosis inhibitor ferrostatin-1 (Fer-1) and the iron chelator deferoxamine (DFO). The combination treatment of FVIO-mediated MH and SRF offers a strategy for HCC treatment by promoting accelerated ferroptosis, presenting a different perspective for the development of ferroptosis-based anticancer therapies.

Nanozymes: Classification and Analytical Applications - A Review

The recent discovery of a new class of nanomaterials called nanozymes, which have the action of enzymes and are thus of tremendous significance, has altered our understanding of these previously believed to be biologically inert nanomaterials. As a significant and exciting class of synthetic enzymes, nanozymes have distinct advantages over natural enzymes. They are less expensive, more stable, and easier to work with and store, making them a viable substitute. This practical advantage of nanozymes over natural enzymes reassures us about the potential of this new technology. Peroxidase-like nanozymes have been investigated for the purpose of creating adaptable biosensors via the use of molecularly imprinted polymers (MIPs) or particular bio recognition ligands, including enzymes, antibodies, and aptamers. This review delves into the distinctions between synthetic and natural enzymes, explaining their structures and analytical applications. It primarily focuses on carbon-based nanozymes, particularly those that contain both carbon and hydrogen, as well as metal-based nanozymes like Fe, Cu, and Au, along with their metal oxide (FeO, CuO), which have applications in many fields today. Analytical chemistry finds great use for nanozymes for sensing and other applications, particularly in comparison with other classical methods in terms of selectivity and sensitivity. Nanozymes, with their unique catalytic capabilities, have emerged as a crucial tool in the early diagnosis of COVID-19. Their application in nanozyme-based sensing and detection, particularly through colorimetric and fluorometric methods, has significantly advanced our ability to detect the virus at an early stage.

MOFs-Based Magnetic Nanozyme to Boost Cascade ROS Accumulation for Augmented Tumor Ferroptosis

The emerging cell death modality of ferroptosis has garnered increasing attention for antitumor treatment but still suffers from low therapeutic efficacy. A metal-organic frameworks (MOFs)-based magnetic nanozyme (PZFH) comprising porphyrin-based Zr-MOF (PCN) on zinc ferrite (ZF) nanoparticles modified with hyaluronic acid, delivering excellent magnetophotonic response for efficient ferroptosis, is reported here. PZFH shows multienzyme-like cascade activity encompassing a photon-triggered oxidase-like catalysis to generate O2 -, which is converted to H2O2 by superoxide dismutase-like activity and subsequent ·OH by magneto-promoted peroxidase (POD) behavior. Newly formed Fe─N coordination and increased Fe2+/Fe3+ levels in the PZFH contribute to the enhanced POD activity, which is further enhanced by accelerated surface electron transfer when exposure to alternated magnetic field. Accumulation of lipid peroxides is eventually accomplished through the conversion of ·OH radicals and singlet oxygen (1O2) produced through laser irradiation. When combined with the depletion of inhibition of glutathione and glutathione peroxidase 4, PZFH exhibits significantly enhanced ferroptosis in tumor-bearing mice, offering insights into nanomedicine for ferroptosis and holding great promise in clinical antitumor therapies.

Construction and Application of Nanozyme Sensor Arrays

Compared with traditional "lock-key mode" biosensors, a sensor array consists of a series of sensing elements based on intermolecular interactions (typically hydrogen bonds, van der Waals forces, and electrostatic interactions). At the same time, sensor arrays also have the advantages of fast response, high sensitivity, low energy consumption, low cost, rich output signals, and imageability, which have attracted widespread attention from researchers. Nanozymes are nanomaterials which own enzyme-like properties. Because of the adjustable activity, high stability, and cost effectiveness of nanozymes, they are potential candidates for construction of sensor arrays to output different signals from analytes through the chemoresponse of colorants, which solves the shortcomings of traditional sensors that they cannot support multiple detection and lack universality. Recently, a sensor array based on nanozymes as nonspecific recognition receptors has attracted much more attention from researchers and has been applied to precise recognition of proteins, bacteria, and heavy metals. In this perspective, attention is given to nanozymes and the regulation of their enzyme-like activity. Particularly, the building principles and methods for sensor arrays based on nanozymes are analyzed, and the applications are summarized. Finally, the approaches to overcome the challenges and perspectives are also presented and analyzed for facilitating further research and development of nanozyme sensor arrays. This perspective should be helpful for gaining insight into research ideas within the field of nanozyme sensor arrays.

Nanozyme as a rising star for metabolic disease management

Nanozyme, characterized by outstanding and inherent enzyme-mimicking properties, have emerged as highly promising alternatives to natural enzymes owning to their exceptional attributes such as regulation of oxidative stress, convenient storage, adjustable catalytic activities, remarkable stability, and effortless scalability for large-scale production. Given the potent regulatory function of nanozymes on oxidative stress and coupled with the fact that reactive oxygen species (ROS) play a vital role in the occurrence and exacerbation of metabolic diseases, nanozyme offer a unique perspective for therapy through multifunctional activities, achieving essential results in the treatment of metabolic diseases by directly scavenging excess ROS or regulating pathologically related molecules. The rational design strategies, nanozyme-enabled therapeutic mechanisms at the cellular level, and the therapies of nanozyme for several typical metabolic diseases and underlying mechanisms are discussed, mainly including obesity, diabetes, cardiovascular disease, diabetic wound healing, and others. Finally, the pharmacokinetics, safety analysis, challenges, and outlooks for the application of nanozyme are also presented. This review will provide some instructive perspectives on nanozyme and promote the development of enzyme-mimicking strategies in metabolic disease therapy.

Nanozyme-based Clusterphene for Enhanced Electrically Catalytic Cancer Therapy

Nanozyme mediated catalytic therapy is an attractive strategy for cancer therapy. However, the nanozymes are tended to assemble into 3D architectures, resulting in poor catalytic efficiency for therapy. This study designs the assembly of nanozymes and natural enzymes into the layered structures featuring hexagonal pores as nanozyme clusterphene and investigates their catalytic therapy with the assistance of electric field. The nanozyme-based clusterphene consists of polyoxometalate (POM) and natural glucose oxidase (GOx), named POMG-based clusterphene, which facilitate multi-enzyme activities including peroxidase (POD), catalase (CAT), and glutathione oxidase (GPx). The highly ordered layers with hexagonal pores of POMG units significantly improve the peroxidase-like (POD-like) activity of the nanozyme and thus the sustained production of reactive oxygen species (ROS). At the same time, GOx can increase endogenous H2O2 and produce gluconic acid while consuming glucose, the nutrient of tumor cell growth. The results indicate that the POD-like activity of POMG-based clusterphene increase approximately sevenfold under electrical stimulation compared with Nd-substituted keggin type POM cluster (NdPW11). The experiments both in vitro and in vivo show that the proposed POMG-based clusterphene mediated cascade catalytic therapy is capable of efficient tumor inhibiting and preventing tumor proliferation in tumor-bearing mice model, promising as an excellent candidate for catalytic therapy.

Advanced nanozymes possess peroxidase-like catalytic activities in biomedical and antibacterial fields: review and progress

Infectious diseases caused by bacterial invasions have imposed a significant global health and economic burden. More worryingly, multidrug-resistant (MDR) pathogenic bacteria born under the abuse of antibiotics have further escalated the status quo. Nowadays, at the crossroads of multiple disciplines such as chemistry, nanoscience and biomedicine, nanozymes, as enzyme-mimicking nanomaterials, not only possess excellent bactericidal ability but also reduce the possibility of inducing resistance. Thus, nanozymes are promising to serve as an alternative to traditional antibiotics. Nanozymes that mimic peroxidase (POD) activity are also known as POD nanozymes. In recent years, POD nanozymes have become one of the most frequently reported and effective nanozymes due to their broad-spectrum bactericidal properties and unique sterilization mechanism. In this review, we introduce the mechanism as well as the classification of POD nanozymes. More importantly, to further improve the antibacterial efficacy of POD nanozymes, we elaborate on three aspects: (1) improving the physicochemical properties; (2) regulating the catalytic microenvironment; and (3) designing multimodel POD nanozymes. In addition, we review the nanosafety of POD nanozymes for discussing their potential toxicity. Finally, the remaining challenges of POD nanozymes and possible future directions are discussed. This work provides a systematic summary of POD nanozymes and hopefully contributes to the early clinical translation.

Nanozyme-Engineered Hydrogels for Anti-Inflammation and Skin Regeneration

Inflammatory skin disorders can cause chronic scarring and functional impairments, posing a significant burden on patients and the healthcare system. Conventional therapies, such as corticosteroids and nonsteroidal anti-inflammatory drugs, are limited in efficacy and associated with adverse effects. Recently, nanozyme (NZ)-based hydrogels have shown great promise in addressing these challenges. NZ-based hydrogels possess unique therapeutic abilities by combining the therapeutic benefits of redox nanomaterials with enzymatic activity and the water-retaining capacity of hydrogels. The multifaceted therapeutic effects of these hydrogels include scavenging reactive oxygen species and other inflammatory mediators modulating immune responses toward a pro-regenerative environment and enhancing regenerative potential by triggering cell migration and differentiation. This review highlights the current state of the art in NZ-engineered hydrogels (NZ@hydrogels) for anti-inflammatory and skin regeneration applications. It also discusses the underlying chemo-mechano-biological mechanisms behind their effectiveness. Additionally, the challenges and future directions in this ground, particularly their clinical translation, are addressed. The insights provided in this review can aid in the design and engineering of novel NZ-based hydrogels, offering new possibilities for targeted and personalized skin-care therapies.

Nanozymatic magnetic nanomixers for enzyme immobilization and multiplexed detection of metabolic disease biomarkers

Nanozymes with enzyme-mimicking catalytic activity and unique functions have stimulated increasing interest in the biosensing field. Herein, we report a magnetic nanozyme (MNE) with integrated superior peroxidase-like activity and efficient mixing ability. This nanozymatic magnetic nanomixer is synthesized by depositing a Fe2+-doped polydopamine coating on the surface of well-aligned magnetic nanoparticles to form a rigid chain-like nanostructure. Polydopamine coating of the nanozymatic MNE allows for efficient immobilization of natural enzymes such as glucose oxidase, cholesterol oxidase or urate oxidase to produce a series of enzymes-immobilized MNE (MNE@enzymes) with intrinsic multienzyme cascade properties. These MNE@enzymes show synchronously rotating capability in spinning magnetic fields, which leads to an 80∼100% improvement in their overall catalytic efficiencies. In the on-chip detection of small molecular metabolites (i.e., glucose, cholesterol, and uric acid), the rotating MNE@enzymes lead to detection sensitivities 2.1∼4.3 times higher than those of the static ones. Importantly, the consistent performance of the rotating MNE@enzymes offers the possibility of integrating the detection of glucose, free cholesterol and uric acid into a single multiplexing microchip assay with smartphone readout, affording an improved sensitivity, good selectivity and reliability. The designed enzymes-loaded MNEs holds great promise in developing rapid and ultrasensitive measurements of diverse targets of healthcare concerns using portable devices.

Engineering magnetic nano-manipulators for boosting cancer immunotherapy

Cancer immunotherapy has shown promising therapeutic results in the clinic, albeit only in a limited number of cancer types, and its efficacy remains less than satisfactory. Nanoparticle-based approaches have been shown to increase the response to immunotherapies to address this limitation. In particular, magnetic nanoparticles (MNPs) as a powerful manipulator are an appealing option for comprehensively regulating the immune system in vivo due to their unique magnetically responsive properties and high biocompatibility. This review focuses on assessing the potential applications of MNPs in enhancing tumor accumulation of immunotherapeutic agents and immunogenicity, improving immune cell infiltration, and creating an immunotherapy-sensitive environment. We summarize recent progress in the application of MNP-based manipulators to augment the efficacy of immunotherapy, by MNPs and their multiple magnetically responsive effects under different types of external magnetic field. Furthermore, we highlight the mechanisms underlying the promotion of antitumor immunity, including magnetically actuated delivery and controlled release of immunotherapeutic agents, tracking and visualization of immune response in real time, and magnetic regulation of innate/adaptive immune cells. Finally, we consider perspectives and challenges in MNP-based immunotherapy.

Nanozyme-Based Artificial Organelles: An Emerging Direction for Artificial Organelles

Artificial organelles are compartmentalized nanoreactors, in which enzymes or enzyme-mimic catalysts exhibit cascade catalytic activities to mimic the functions of natural organelles. Importantly, research on artificial organelles paves the way for the bottom-up design of synthetic cells. Due to the separation effect of microcompartments, the catalytic reactions of enzymes are performed without the influence of the surrounding medium. The current techniques for synthesizing artificial organelles rely on the strategies of encapsulating enzymes into vesicle-structured materials or reconstituting enzymes onto the microcompartment materials. However, there are still some problems including limited functions, unregulated activities, and difficulty in targeting delivery that hamper the applications of artificial organelles. The emergence of nanozymes (nanomaterials with enzyme-like activities) provides novel ideas for the fabrication of artificial organelles. Compared with natural enzymes, nanozymes are featured with multiple enzymatic activities, higher stability, easier to synthesize, lower cost, and excellent recyclability. Herein, the most recent advances in nanozyme-based artificial organelles are summarized. Moreover, the benefits of compartmental structures for the applications of nanozymes, as well as the functional requirements of microcompartment materials are also introduced. Finally, the potential applications of nanozyme-based artificial organelles in biomedicine and the related challenges are discussed.

Design of Magnetic Nanoplatforms for Cancer Theranostics

Cancer is the top cause of death globally. Developing smart nanomedicines that are capable of diagnosis and therapy (theranostics) in one-nanoparticle systems are highly desirable for improving cancer treatment outcomes. The magnetic nanoplatforms are the ideal system for cancer theranostics, because of their diverse physiochemical properties and biological effects. In particular, a biocompatible iron oxide nanoparticle based magnetic nanoplatform can exhibit multiple magnetic-responsive behaviors under an external magnetic field and realize the integration of diagnosis (magnetic resonance imaging, ultrasonic imaging, photoacoustic imaging, etc.) and therapy (magnetic hyperthermia, photothermal therapy, controlled drug delivery and release, etc.) in vivo. Furthermore, due to considerable variation among tumors and individual patients, it is a requirement to design iron oxide nanoplatforms by the coordination of diverse functionalities for efficient and individualized theranostics. In this article, we will present an up-to-date overview on iron oxide nanoplatforms, including both iron oxide nanomaterials and those that can respond to an externally applied magnetic field, with an emphasis on their applications in cancer theranostics.

An intrinsically thermogenic nanozyme for synergistic antibacterial therapy

Bacterial infections with a high mortality rate have become serious health issues for human beings. As natural enzymes play an important role in the survival and proliferation of bacteria, effective inhibition of bacterial natural enzyme activities is important for antimicrobial therapy. Herein, a novel enzymatic antibacterial strategy, of enhancing nanozyme activity but reducing bacterial natural enzyme activity, is developed based on yolk-shell Fe₂C@Fe₃O₄-PEG thermogenic nanozymes with highly magnetothermal properties and thermal-enhanced peroxidase-like activities. When applying an alternating magnetic field, the special yolk-shell Fe₂C@Fe₃O₄-PEG nanozymes show a better magnetothermal effect than Fe₂C (yolk) and Fe₃O₄ (shell) due to the increased value of their magnetic energy product, and the peroxidase-like activity of the nanozymes is further improved. Meanwhile, remarkably restrained by the enhanced magnetothermal effect from the nanozymes, typical natural enzyme activities of bacteria are detected with an inhibition rate of nearly 80%. Both in vitro and in vivo experiments exhibit superior synergistic antibacterial efficacy. The antimicrobial mechanisms are explained as the reduction of natural enzyme activities and the disruption of cell walls and membranes induced by the self-magnetothermal effect of nanozymes along with the production of abundant ˙OH radicals derived from the thermal-enhanced peroxidase-like activity of nanozymes. Overall, this work focuses on an intrinsically thermogenic nanozyme, which provides a potential platform for future synergistic antibacterial application.

Precise Regulation of Enzyme-Nanozyme Cascade Reaction Kinetics by Magnetic Actuation toward Efficient Tumor Therapy

Spatiotemporal regulation of multi-enzyme catalysis with stimuli is crucial in nature to meet different metabolic requirements but presents a challenge in artificial cascade systems. Here, we report a strategy for precise and tunable modulation of enzyme-nanozyme cascade reaction kinetics by remote magnetic stimulation. As a proof of concept, glucose oxidase (GOx) was immobilized onto a ferrimagnetic vortex iron oxide nanoring (Fe3O4 NR) functionalized with poly(ethylene glycol) of different molecular weights to construct a series of Fe3O4 NR@GOx with nanometer linking distances. The activities of GOx and the Fe3O4 NR nanozyme in these systems were shown to be differentially stimulated by Fe3O4 NR-mediated local heat in response to an alternating magnetic field (AMF), leading to modulated cascade reaction kinetics in a distance-dependent manner. Compared to the free GOx and Fe3O4 NR mixture, Fe3O4 NR(D2)@GOx with an optimum linking distance of 1 nm exhibits a superior kinetic match between GOx and the Fe3O4 NR nanozyme and over a 400-fold higher cascade activity under AMF exposure. This enables remarkable intracellular reactive oxygen species production and significantly improved tumor inhibition of AMF-stimulated Fe3O4 NR(D2)@GOx in 4T1 tumor-bearing mice. The strategy reported here offers a straightforward new tool for fine-tuning multi-enzyme catalysis at the molecular level using magnetic stimuli and holds great promise for use in a variety of biotechnology and synthetic biology applications.