Metal-Based Nanozymes with Multienzyme-Like Activities as Therapeutic Candidates: Applications, Mechanisms, and Optimization Strategy

DNA-based FeCuAg nanoclusters with peroxidase-like and GSH depletion activities for toxicity of in vitro cancer cells

Developing the efficient nanozymes for reactive oxygen species (ROS)-mediated highly potent tumor catalytic therapy has become a great challenge. In this study, we prepared the DNA-Fe, -FeAg, and -FeCuAg nanocluster (NCs) using the G-/C-rich single-stranded DNA (ssDNA) templates. The steady-state kinetic and the catalytic performances and mechanisms of DNA-metal NCs were first systematically investigated. The results indicated that c-kit-TBA-Fe, c-kit-TBA-FeAg, and c-kit-TBA-FeCuAg NCs exhibited the high peroxidase-like activity. All of three types of NCs presented the higher affinity to the substrate TMB and better storage stability at 4 °C than horseradish peroxidase (HRP). Moreover, c-kit-TBA-FeAg and c-kit-TBA-FeCuAg NCs presented the 6.7- and 4.7-fold stronger affinity to TMB than c-kit-TBA-Fe, respectively. However, the maximum reaction rate (Vmax) of c-kit-TBA-FeCuAg NCs with H2O2 was the largest, which promoted the generation of much more •OH in the reaction system. More importantly, c-kit-TBA-FeCuAg NCs were able to deplete largely the intracellular GSH and thus generate lots of endogenous ROS in HeLa cells, thereby exhibiting the significant and specific in vitro cancer cells toxicity. Therefore, c-kit-TBA-FeCuAg NCs, with peroxidase-like activity and glutathione (GSH) consumption ability, hold the ROS-based promising therapeutic effects for cancer.

Iridium nanoparticles supported on polyaniline nanotubes for peroxidase mimicking towards total antioxidant capacity assay of fruits and vegetables

In this study, a straightforward approach is presented for the first time to anchor Ir nanoparticles on the surface of uniform polyaniline (PANi) nanotubes (NTs), which can be used as an efficient peroxidase (POD)-like catalyst. The morphology and chemical structure of the PANi-Ir nanocomposite are characterized by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffractometer (XRD), Raman and X-ray photoelectron spectroscopy (XPS) measurements. Owing to the strong interaction between Ir nanoparticles and PANi, a remarkable catalytic enhancement is achieved compared to the bare Ir black catalyst and individual PANi NTs, dominating withan electron transfer mechanism. Furthermore, an efficient colorimetric sensor for ascorbic acid (AA) is developed with a low detection limit of 1.0 μM (S/N = 3), and a total antioxidant capacity (TAC) sensing platform is also constructed for the rigorous detection and analysis of fruits and vegetables.

Transition-metal-based nanozymes for biosensing and catalytic tumor therapy

Nanozymes, as an emerging class of enzyme mimics, have attracted much attention due to their adjustable catalytic activity, low cost, easy modification, and good stability. Researchers have made great efforts in developing and applying high-performance nanozymes. Recently, transition-metal-based nanozymes have been designed and widely developed because they possess unique photoelectric properties and high enzyme-like catalytic activities. To highlight these achievements and help researchers to understand the research status of transition-metal-based nanozymes, the development of transition-metal-based nanozymes from material characteristics to biological applications is summarized. Herein, we focus on introducing six categories of transition-metal-based nanozymes and highlight their progress in biomarker sensing and catalytic therapy for tumors. We hope that this review can guide the further development of transition-metal-based nanozymes and promote their practical applications in cancer diagnosis and treatment.

Emerging Chemodynamic Nanotherapeutics for Cancer Treatment

Chemodynamic therapy (CDT) has emerged as a transformative paradigm in the realm of reactive oxygen species -mediated cancer therapies, exhibiting its potential as a sophisticated strategy for precise and effective tumor treatment. CDT primarily relies on metal ions and hydrogen peroxide to initiate Fenton or Fenton-like reactions, generating cytotoxic hydroxyl radicals. Its notable advantages in cancer treatment are demonstrated, including tumor specificity, autonomy from external triggers, and a favorable side-effect profile. Recent advancements in nanomedicine are devoted to enhancing CDT, promising a comprehensive optimization of CDT efficacy. This review systematically elucidates cutting-edge achievements in chemodynamic nanotherapeutics, exploring strategies for enhanced Fenton or Fenton-like reactions, improved tumor microenvironment modulation, and precise regulation in energy metabolism. Moreover, a detailed analysis of diverse CDT-mediated combination therapies is provided. Finally, the review concludes with a comprehensive discussion of the prospects and intrinsic challenges to the application of chemodynamic nanotherapeutics in the domain of cancer treatment.

Transition-Metal-Based Nanozymes: Synthesis, Mechanisms of Therapeutic Action, and Applications in Cancer Treatment

Cancer, as one of the leading causes of death worldwide, drives the advancement of cutting-edge technologies for cancer treatment. Transition-metal-based nanozymes emerge as promising therapeutic nanodrugs that provide a reference for cancer therapy. In this review, we present recent breakthrough nanozymes for cancer treatment. First, we comprehensively outline the preparation strategies involved in creating transition-metal-based nanozymes, including hydrothermal method, solvothermal method, chemical reduction method, biomimetic mineralization method, and sol-gel method. Subsequently, we elucidate the catalytic mechanisms (catalase (CAT)-like activities), peroxidase (POD)-like activities), oxidase (OXD)-like activities) and superoxide dismutase (SOD)-like activities) of transition-metal-based nanozymes along with their activity regulation strategies such as morphology control, size manipulation, modulation, composition adjustment and surface modification under environmental stimulation. Furthermore, we elaborate on the diverse applications of transition-metal-based nanozymes in anticancer therapies encompassing radiotherapy (RT), chemodynamic therapy (CDT), photodynamic therapy (PDT), photothermal therapy (PTT), sonodynamic therapy (SDT), immunotherapy, and synergistic therapy. Finally, the challenges faced by transition-metal-based nanozymes are discussed alongside future research directions. The purpose of this review is to offer scientific guidance that will enhance the clinical applications of nanozymes based on transition metals.

Multienzyme-Like Nanozyme Encapsulated Ocular Microneedles for Keratitis Treatment

Keratitis, an inflammation of the cornea caused by bacterial or fungal infections, is one of the leading causes of severe visual disability and blindness. Keratitis treatment requires both the prevention of infection and the reduction of inflammation. However, owing to their limited therapeutic functions, in addition to the ocular barrier, existing conventional medications are characterized by poor efficacy and low bioavailability, requiring high dosages or frequent topical treatment, which represents a burden on patients and increases the risk of side effects. In this study, manganese oxide nanocluster-decorated graphdiyne nanosheets (MnOx/GDY) are developed as multienzyme-like nanozymes for the treatment of infectious keratitis and loaded into hyaluronic acid and polymethyl methacrylate-based ocular microneedles (MGMN). MGMN not only exhibits antimicrobial and anti-inflammatory effects owing to its multienzyme-like activities, including oxidase, peroxidase, catalase, and superoxide dismutase mimics but also crosses the ocular barrier and shows increased bioavailability via the microneedle system. Moreover, MGMN is demonstrated to eliminate pathogens, prevent biofilm formation, reduce inflammation, alleviate ocular hypoxia, and promote the repair of corneal epithelial damage in in vitro, ex vivo, and in vivo experiments, thus providing a better therapeutic effect than commercial ophthalmic voriconazole, with no obvious microbial resistance or cytotoxicity.

Multi-Enzyme-Based Superabsorbent Hydrogel for Self-Enhanced NIR-II Photothermal-Catalytic Antibacterial Therapy

The synergistic strategy of nanozyme-based catalytic therapy and photothermal therapy holds great potential for combating bacterial infection. However, challenges such as single and limited enzyme catalytic property, unfavorable catalytic environment, ineffective interaction between nanozymes and bacteria, unsafe laser irradiation ranges, and failed trauma fluid management impede their antibacterial capability and wound healing speed. Herein, for the first time, a PNMn hydrogel is fabricated with multi-enzyme activities and excellent near-infrared (NIR)-II photothermal performance for self-enhanced NIR-II photothermal-catalytic capabilities to efficiently eradicate bacteria. This hydrogel triggers parallel and cascade reactions to generate •OH, •O2 -, and 1O2 radicals from H2O2 and O2 without external energy input. Notably, it provides a suitable catalytic environment while capturing bacteria (≈30.1% of Escherichia coli and ≈29.3% of Staphylococcus aureus) to reinforce antibacterial activity. Furthermore, the PNMn hydrogel expedites skin wound healing by managing excess fluid (swelling rate up to ≈7299%). The PNMn hydrogel possesses remarkable stretching, elasticity, toughness, and adhesive characteristics under any shape of the wound, thus making it suitable for wound dressing. Therefore, the PNMn hydrogel has great potential to be employed as a next-generation wound dressing in the clinical context, providing a non-antibiotic strategy to improve the antibacterial performance and promote wound healing.

Nanoarchitectonics of Bimetallic Cu-/Co-Doped Nitrogen-Carbon Nanozyme-Functionalized Hydrogel with NIR-Responsive Phototherapy for Synergistic Mitigation of Drug-Resistant Bacterial Infections

Superbug infections and transmission have become major challenges in the contemporary medical field. The development of novel antibacterial strategies to efficiently treat bacterial infections and conquer the problem of antimicrobial resistance (AMR) is extremely important. In this paper, a bimetallic CuCo-doped nitrogen-carbon nanozyme-functionalized hydrogel (CuCo/NC-HG) has been successfully constructed. It exhibits photoresponsive-enhanced enzymatic effects under near-infrared (NIR) irradiation (808 nm) with strong peroxidase (POD)-like and oxidase (OXD)-like activities. Upon NIR irradiation, CuCo/NC-HG possesses photodynamic activity for producing singlet oxygen(1O2), and it also has a high photothermal conversion effect, which not only facilitates the elimination of bacteria but also improves the efficiency of reactive oxygen species (ROS) production and accelerates the consumption of GSH. CuCo/NC-HG shows a lower hemolytic rate and better cytocompatibility than CuCo/NC and possesses a positive charge and macroporous skeleton for restricting negatively charged bacteria in the range of ROS destruction, strengthening the antibacterial efficiency. Comparatively, CuCo/NC and CuCo/NC-HG have stronger bactericidal ability against methicillin-resistant Staphylococcus aureus (MRSA) and ampicillin-resistant Escherichia coli (AmprE. coli) through destroying the cell membranes with a negligible occurrence of AMR. More importantly, CuCo/NC-HG plus NIR irradiation can exhibit satisfactory bactericidal performance in the absence of H2O2, avoiding the toxicity from high-concentration H2O2. In vivo evaluation has been conducted using a mouse wound infection model and histological analyses, and the results show that CuCo/NC-HG upon NIR irradiation can efficiently suppress bacterial infections and promote wound healing, without causing inflammation and tissue adhesions.

Neuromodulation by nanozymes and ultrasound during Alzheimer's disease management

Alzheimer's disease (AD) is a neurodegenerative disorder with complex pathogenesis and effective clinical treatment strategies for this disease remain elusive. Interestingly, nanomedicines are under extensive investigation for AD management. Currently, existing redox molecules show highly bioactive property but suffer from instability and high production costs, limiting clinical application for neurological diseases. Compared with natural enzymes, artificial enzymes show high stability, long-lasting catalytic activity, and versatile enzyme-like properties. Further, the selectivity and performance of artificial enzymes can be modulated for neuroinflammation treatments through external stimuli. In this review, we focus on the latest developments of metal, metal oxide, carbon-based and polymer based nanozymes and their catalytic mechanisms. Recent developments in nanozymes for diagnosing and treating AD are emphasized, especially focusing on their potential to regulate pathogenic factors and target sites. Various applications of nanozymes with different stimuli-responsive features were discussed, particularly focusing on nanozymes for treating oxidative stress-related neurological diseases. Noninvasiveness and focused application to deep body regions makes ultrasound (US) an attractive trigger mechanism for nanomedicine. Since a complete cure for AD remains distant, this review outlines the potential of US responsive nanozymes to develop future therapeutic approaches for this chronic neurodegenerative disease and its emergence in AD management.

Gold nanoparticles (AuNPs) decrease the viability of cervical cancer cells by inducing the BAX gene and activating antioxidant enzymes

BACKGROUND

Cervical Cancer (CC), a leading cause of female mortality worldwide, demonstrates a direct association with high-risk human papillomavirus (HPV) infections. However, not all CC patients exhibit HPV infection, suggesting additional predisposing factors. Recently, disturbances in the oxidant-antioxidant balance have been implicated in CC development. This study explores the impact of gold nanoparticles (AuNPs) on the survival and antioxidant capacity of HeLa cells, aiming to contribute to novel CC therapy approaches.

METHODS AND RESULTS

Synthesized and characterized AuNPs (25.5 nm, uniform distribution according to the DLS analysis) were administered to HeLa cells at varying concentrations. After 24 h, cell viability was assessed using the (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2 H-tetrazolium bromide) (MTT) assay. Real-time PCR measured expression levels of apoptosis-related genes (BCL2 associated X (BAX) and p53). Catalase and superoxide dismutase (SOD) activities, key antioxidant enzymes, were also evaluated post-AuNP treatment. AuNPs dose-dependently reduced HeLa cell viability, with an IC50 value of 113 µg/ml. BAX gene expression significantly increased, indicating pro-apoptotic effects. Moreover, enzyme activities significantly rose under AuNP influence.

CONCLUSIONS

AuNPs demonstrated the potential to induce HeLa cell death by upregulating pro-apoptotic BAX gene expression and altering antioxidant system enzyme activities. These findings underscore the promise of AuNPs as a therapeutic avenue for CC, emphasizing their impact on crucial cellular processes involved in cancer progression.

Core-Shell Structured Nanozyme with PDA-Mediated Enhanced Antioxidant Efficiency to Treat Early Intervertebral Disc Degeneration

Early intervention during intervertebral disc degeneration (IDD) plays a vital role in inhibiting its deterioration and activating the regenerative process. Aiming at the high oxidative stress (OS) in the IDD microenvironment, a core-shell structured nanozyme composed of Co-doped NiO nanoparticle (CNO) as the core encapsulated with a polydopamine (PDA) shell, named PDA@CNO, was constructed, hoping to regulate the pathological environment. The results indicated that the coexistence of abundant Ni3+/Ni2+and Co3+/Co2+redox couples in CNO provided rich catalytic sites; meanwhile, the quinone and catechol groups in the PDA shell could enable the proton-coupled electron transfer, thus endowing the PDA@CNO nanozyme with multiple antioxidative enzyme-like activities to scavenge •O2-, H2O2, and •OH efficiently. Under OS conditions in vitro, PDA@CNO could effectively reduce the intracellular ROS in nucleus pulposus (NP) into friendly H2O and O2, to protect NP cells from stagnant proliferation, abnormal metabolism (senescence, mitochondria dysfunction, and impaired redox homeostasis), and inflammation, thereby reconstructing the extracellular matrix (ECM) homeostasis. The in vivo local injection experiments further proved the desirable therapeutic effects of the PDA@CNO nanozyme in a rat IDD model, suggesting great potential in prohibiting IDD from deterioration.

Au/Pt@ZIF-90 Nanoenzyme Capsule-Based "Explosive" Signal Amplifier for "All-in-Tube" POCT

The sensitive, convenient, and visual detection of low-concentration disease markers in biological samples has always been a priority in disease diagnosis. However, existing research has been problematic due to complex operation and unsatisfactory sensitivity. Consequently, an "explosive" signal amplification platform based on Au/Pt@ZIF-90 was developed for sensitive visual detection of disease markers. In this study, a controllable and explosively released Au/Pt nanoparticles (NPs) "nanoenzyme capsule" was prepared by encapsulating Au/Pt NPs with excellent peroxidase activity in ZIF-90. This was achieved by adjusting the particle size of ZIF-90 and the encapsulation amount of Au/Pt NPs. Using the prepared capsules as the signal output module and aptamer as the target recognition module, an "All-in-Tube" portable point-of-care (POC) platform was constructed by integrating the Au/Pt@ZIF-90/filter paper and TMB/strips into an Eppendorf (EP) tube. By utilizing specific competitive binding of targets to aptamers, the platform enabled the sensitive and convenient measurement of small molecular disease markers. Taking adenosine as the proof of concept, the portable detection achieved excellent sensitivity. Moreover, the platform can achieve universal detection of various targets by varying the aptamer sequence. This signal amplification strategy provides a design pattern for the detection of low-concentration targets in biological samples and holds significant potential in the fields of disease diagnosis and environmental monitoring.

A comprehensive exploration of the latest innovations for advancements in enhancing selectivity of nanozymes for theranostic nanoplatforms

Nanozymes have captured significant attention as a versatile and promising alternative to natural enzymes in catalytic applications, with wide-ranging implications for both diagnosis and therapy. However, the limited selectivity exhibited by many nanozymes presents challenges to their efficacy in diagnosis and raises concerns regarding their impact on the progression of disease treatments. In this article, we explore the latest innovations aimed at enhancing the selectivity of nanozymes, thereby expanding their applications in theranostic nanoplatforms. We place paramount importance on the critical development of highly selective nanozymes and present innovative strategies that have yielded remarkable outcomes in augmenting selectivities. The strategies encompass enhancements in analyte selectivity by incorporating recognition units, refining activity selectivity through the meticulous control of structural and elemental composition, integrating synergistic materials, fabricating selective nanomaterials, and comprehensively fine-tuning selectivity via approaches such as surface modification, cascade nanozyme systems, and manipulation of external stimuli. Additionally, we propose optimized approaches to propel the further advancement of these tailored nanozymes while considering the limitations associated with existing techniques. Our ultimate objective is to present a comprehensive solution that effectively addresses the limitations attributed to non-selective nanozymes, thus unlocking the full potential of these catalytic systems in the realm of theranostics.

Bacteria-derived topologies of Cu2O nanozymes exert a variable antibacterial effect

The ability of bacteria to facilitate fabrication of nanomaterials has been adapted towards bacterial sensing applications. In this work, we fabricate spherical, cubic and truncated octahedron topologies of Cu2O nanoparticles via E. coli-facilitated redox reaction in an electrochemical setup. The Cu2O nanoparticles exhibit cytochrome c oxidase-like activity with the spherical topology displaying higher catalytic rate compared to the other geometries. The topology-dependent catalytic behavior of Cu2O nanoparticles has not been reported previously. The Cu2O nanozymes also display E. coli killing activity in a topology-correlated manner. The E. coli mediated redox reaction in an electrochemical setup is being reported for the first time for synthesis of different topologies of Cu2O which also exert a variable antibacterial effect.