Specific "Unlocking" of a Nanozyme-Based Butterfly Effect To Break the Evolutionary Fitness of Chaotic Tumors

Photo-Switchable Peroxidase/Catalase-Like Activity of Carbon Quantum Dots

Nanozymes possess multi-enzyme activities over the natural enzymes, which produce multi-pathway synergistic effects for varies of biomedical applications. Unfortunately, their multi-enzyme activities are in fighting, significantly reducing the synergistic effects. Dynamic regulation of their multi-enzyme activities is the bottleneck for intelligent therapies. Herein, we construct a novel oxygen-nitrogen functionalized carbon quantum dots (O/N-CQDs) with peroxidase-like (Reactive oxygen species (ROS) producer) activity. Interestingly, the peroxidase-like activity can be reversibly converted to catalase-like (ROS scavenger) activity under visible light irradiation. It is found that both the peroxidase/catalase-like activity of O/N-CQDs can be precisely manipulated by the light intensity. The mechanism of switchable enzyme activities is attributed to the polarization of quinoid nitrogen in polyaniline (PANI) precursor retained on O/N-CQDs under visible light, which consumes the ROS to produce O2 and H2O. As a proof-of-concept demonstration, we are able to non-intrusively up and down regulate the ROS level in cells successfully by simply switching off and on the light respectively, potentially facilitating the precise medicine based on the development of the disease. Indeed, the photo-switchable peroxidase/catalase-like activity of O/N-CQDs opens a non-invasive strategy for better manipulations of the multi-activity of nanozymes, promising their wider and more intelligent biomedical applications.

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.

De Novo Designed Ru(II) Metallacycle as a Microenvironment-Adaptive Sonosensitizer and Sonocatalyst for Multidrug-Resistant Biofilms Eradication

Albeit sonodynamic therapy (SDT) has achieved encouraging progress in microbial sterilization, the scarcity of guidelines for designing highly effective sonosensitizers and the intricate biofilm microenvironment (BME), substantially hamper the therapeutic efficacy against biofilm infections. To address the bottlenecks, we innovatively design a Ru(II) metallacycle-based sonosensitizer/sonocatalyst (named Ru-A3-TTD) to enhance the potency of sonotherapy by employing molecular engineering strategies tailored to BME. Our approach involves augmenting Ru-A3-TTD's production of ultrasonic-triggered reactive oxygen species (ROS), surpassing the performance of commercial sonosensitizers, through a straightforward but potent π-expansion approach. Within the BME, Ru-A3-TTD synergistically amplifies sonotherapeutic efficacy via triple-modulated approaches: (i) effective alleviation of hypoxia, leading to increased ROS generation, (ii) disruption of the antioxidant defense system, which shields ROS from glutathione consumption, and (iii) enhanced biofilm penetration, enabling ROS production in deep sites. Notably, Ru-A3-TTD sono-catalytically oxidizes NADPH, a critical coenzyme involved in antioxidant defenses. Consequently, Ru-A3-TTD demonstrates superior biofilm eradication potency against multidrug-resistant Escherichia coli compared to conventional clinical antibiotics, both in vitro and in vivo. To our knowledge, this study represents the pioneering instance of a supramolecular sonosensitizer/sonocatalyst. It provides valuable insights into the structure-activity relationship of sonosensitizers and paves a promising pathway for the treatment of biofilm infections.

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.

Biosystem-Inspired Engineering of Nanozymes for Biomedical Applications

Nanozymes with intrinsic enzyme-mimicking activities have shown great potential to become surrogates of natural enzymes in many fields by virtue of their advantages of high catalytic stability, ease of functionalization, and low cost. However, due to the lack of predictable descriptors, most of the nanozymes reported in the past have been obtained mainly through trial-and-error strategies, and the catalytic efficacy, substrate specificity, as well as practical application effect under physiological conditions, are far inferior to that of natural enzymes. To optimize the catalytic efficacies and functions of nanozymes in biomedical settings, recent studies have introduced biosystem-inspired strategies into nanozyme design. In this review, recent advances in the engineering of biosystem-inspired nanozymes by leveraging the refined catalytic structure of natural enzymes, simulating the behavior changes of natural enzymes in the catalytic process, and mimicking the specific biological processes or living organisms, are introduced. Furthermore, the currently involved biomedical applications of biosystem-inspired nanozymes are summarized. More importantly, the current opportunities and challenges of the design and application of biosystem-inspired nanozymes are discussed. It is hoped that the studies of nanozymes based on bioinspired strategies will be beneficial for constructing the new generation of nanozymes and broadening their biomedical applications.

Nanozyme-Based Regulation of Cellular Metabolism and Their Applications

Metabolism is the sum of the enzyme-dependent chemical reactions, which produces energy in catabolic process and synthesizes biomass in anabolic process, exhibiting high similarity in mammalian cell, microbial cell, and plant cell. Consequently, the loss or gain of metabolic enzyme activity greatly affects cellular metabolism. Nanozymes, as emerging enzyme mimics with diverse functions and adjustable catalytic activities, have shown attractive potential for metabolic regulation. Although the basic metabolic tasks are highly similar for the cells from different species, the concrete metabolic pathway varies with the intracellular structure of different species. Here, the basic metabolism in living organisms is described and the similarities and differences in the metabolic pathways among mammalian, microbial, and plant cells and the regulation mechanism are discussed. The recent progress on regulation of cellular metabolism mainly including nutrient uptake and utilization, energy production, and the accompanied redox reactions by different kinds of oxidoreductases and their applications in the field of disease therapy, antimicrobial therapy, and sustainable agriculture is systematically reviewed. Furthermore, the prospects and challenges of nanozymes in regulating cell metabolism are also discussed, which broaden their application scenarios.

Biodegradable Osmium Nanoantidotes for Photothermal-/Chemo- Combined Treatment and to Prevent Chemotherapy-Induced Acute Kidney Injury

Acute kidney injury (AKI) is a common adverse event in chemotherapy patients. AKI is accompanied by the generation of reactive oxygen species (ROS) and inflammation. Therefore, the management of ROS and inflammation is a potential strategy for AKI mitigation. Herein, polyethylene glycol-coated osmium nanozyme-based antidotes (Os) are developed for imaging-guided photothermal therapy (PTT) in combination with cisplatin (Pt); while, avoiding AKI induced by high-dose Pt. Os nanoantidotes can enhance the efficiency of tumor treatment during combined PTT and chemotherapy and inhibit tumor metastasis by improving the hypoxic and inflammatory tumor microenvironment. Os nanoantidotes preferentially accumulate in the kidney because of their 2-nm size distribution; and then, regulate inflammation by scavenging ROS and generating oxygen to alleviate Pt-induced AKI. Os nanoantidotes can be cleared from the kidneys by urine excretion but can be degraded under hydrogen peroxide stimulation, reducing the bio-retention of these compounds. By integrating PTT with inflammatory regulation, Os nanoantidotes have the potential to reduce the side effects of chemotherapy, offering an alternative route for the clinical management of cancer patients with chemotherapy-induced AKI.

Recent advances in nanomedicine for metabolism-targeted cancer therapy

Metabolism denotes the sum of biochemical reactions that maintain cellular function. Different from most normal differentiated cells, cancer cells adopt altered metabolic pathways to support malignant properties. Typically, almost all cancer cells need a large number of proteins, lipids, nucleotides, and energy in the form of ATP to support rapid division. Therefore, targeting tumour metabolism has been suggested as a generic and effective therapy strategy. With the rapid development of nanotechnology, nanomedicine promises to have a revolutionary impact on clinical cancer therapy due to many merits such as targeting, improved bioavailability, controllable drug release, and potentially personalized treatment compared to conventional drugs. This review comprehensively elucidates recent advances of nanomedicine in targeting important metabolites such as glucose, glutamine, lactate, cholesterol, and nucleotide for effective cancer therapy. Furthermore, the challenges and future development in this area are also discussed.

Synergistic Combination of an Intelligent Nanozyme and Radiotherapy for Treating Renal Cancer

Background

Preserving nephrons while avoiding tumor recurrence during the treatment of renal cell carcinoma remains as a challenge in clinic. To achieve desired therapeutic outcome, we developed specific nanozymes based on the tumor microenvironment and evaluated its efficacy in combination with radiotherapy.

Methods

Herein, a hybrid nanozyme CeO2@Au-PEG nanocomposite nanoparticle (NPs) was developed for the treatment of renal tumor. It was composed of gold nanozyme decorated CeO2 nanorods and exhibited both glucose-oxidase like by gold nanozyme and peroxidase-like catalytic activities. Due to the high metabolic rate of tumor cells, they take up a huge amount of glucose to survive and proliferate. Therefore, we generated CeO2@Au-PEG NPs, which exhausted glucose in the tumor tissue and generated hydrogen peroxide, depleting the source of energy and causing tumor cell death. Then the generated hydrogen peroxide was degraded by the peroxidase-mimicking properties of CeO2@Au-PEG NPs, elevating oxidative stress and thus enhancing tumor cell death. Moreover, due to the high mass nuclei of gold and cerium, they could further sensitize the tumors to radiotherapy and thus thoroughly eliminate tumors.

Results

With enough biocompatibility, CeO2@Au-PEG NPs showed superior ability to deplete glucose as well as enhance oxidative stress by producing reactive oxygen species in RENCA cells under ionizing irradiation. Moreover, CeO2@Au-PEG NPs greatly improved radiotherapy mediated tumor ablation in tumor bearing mice.

Conclusion

Systematic experiments demonstrated the synergistic therapeutic effects of the combination of CeO2@Au-PEG NPs and radiotherapy in renal tumor model, which may serve as a promising strategy for treating renal cancer patients in the clinic.

Multi-Enzyme Co-Expressed Nanomedicine for Anti-Metastasis Tumor Therapy by Up-Regulating Cellular Oxidative Stress and Depleting Cholesterol

Tumor cells movement and migration are inseparable from the integrity of lipid rafts and the formation of lamellipodia, and lipid rafts are also a prerequisite for the formation of lamellipodia. Therefore, destroying the lipid rafts is an effective strategy to inhibit tumor metastasis. Herein, a multi-enzyme co-expressed nanomedicine: cholesterol oxidase (CHO) loaded Co─PN3 single-atom nanozyme (Co─PN3 SA/CHO) that can up-regulate cellular oxidative stress, disrupt the integrity of lipid rafts, and inhibit lamellipodia formation to induce anti-metastasis tumor therapy, is developed. In this process, Co─PN3 SA can catalyze oxygen (O2 ) and hydrogen peroxide (H2 O2 ) to generate reactive oxygen species (ROS) via oxidase-like and Fenton-like properties. The doping of P atoms optimizes the adsorption process of the intermediate at the active site and enhances the ROS generation properties of nanomedicine. Meantime, O2 produced by catalase-like catalysis can combine with excess cholesterol to generate more H2 O2 under CHO catalysis, achieving enhanced oxidative damage to tumor cells. Most importantly, cholesterol depletion in tumor cells also disrupts the integrity of lipid rafts and inhibits the formation of lamellipodia, greatly inhibiting the proliferation and metastasis of tumor cells. This strategy by up-regulating cellular oxidative stress and depleting cellular cholesterol constructs a new idea for anti-metastasis-oriented cancer therapy strategies.

Mechanoregulatory Cholesterol Oxidase-Functionalized Nanoscale Metal-Organic Framework Stimulates Pyroptosis and Reinvigorates T Cells

Cancer cells alter mechanical tension in their cell membranes. New interventions to regulate cell membrane tension present a potential strategy for cancer therapy. Herein, the increase of cell membrane tension by cholesterol oxidase (COD) via cholesterol depletion in vitro and the design of a COD-functionalized nanoscale metal-organic framework, Hf-TBP/COD, for cholesterol depletion and mechanoregulation of tumors in vivo, are reported. COD is found to deplete cholesterol and disrupt the mechanical properties of lipid bilayers, leading to decreased cell proliferation, migration, and tolerance to oxidative stress. Hf-TBP/COD increases mechanical tension of plasma membranes and osmotic fragility of cancer cells, which induces influx of calcium ions, inhibits cell migration, increases rupturing propensity for effective caspase-1 mediated pyroptosis, and decreases tolerance to oxidative stress. In the tumor microenvironment, Hf-TBP/COD downregulates multiple immunosuppressive checkpoints to reinvigorate T cells and enhance T cell infiltration. Compared to Hf-TBP, Hf-TBP/COD improves anti-tumor immune response and tumor growth inhibition from 54.3% and 79.8% to 91.7% and 95% in a subcutaneous triple-negative breast cancer model and a colon cancer model, respectively.

Iridium nanozyme-mediated photoacoustic imaging-guided NIR-II photothermal therapy and tumor microenvironment regulation for targeted eradication of cancer stem cells

Cancer stem cells (CSCs) are found in many solid tumors, which play decisive roles in the occurrence, recurrence and metastasis of tumors. However, drugs are difficult to kill CSCs due to their limited number and location in oxygen-deprived tissue far from the blood vessels. Meanwhile, the survival and stemness maintenance of CSCs strongly depend on the tumor microenvironment (TME). Herein, we developed a CD44 antibody modified iridium nanosheet with enzyme-like activity (defined as Ir Nts-Ab) that effectively eradicates CSCs for cancer therapy. We observe that Ir Nts-Ab can enrich tumor tissues to remove excessive reactive oxygen species and produce oxygen, thus alleviating hypoxia and the inflammatory TME to reduce the proportion of CSCs and inhibit metastasis. In addition, Ir Nts-Ab targets CSCs and normal cancer cells with near infrared II-region photothermal therapy (NIR-II PTT), and is easily taken up by CSCs due to recognition of the CD44 proteins. Moreover, photoacoustic imaging helps monitor drug accumulation and hypoxic TME improvement in tumor tissue. Importantly, Ir Nts-Ab has good biological safety, making it suitable for biomedical applications. This iridium nanozyme based on TME regulation as well as NIR-II PTT will be a promising strategy for the treatment of cancer. STATEMENT OF SIGNIFICANCE: Cancer stem cells (CSCs) are key factors that make tumors difficult to eradicate, and strongly depend on the hypoxic tumor microenvironment (TME), which plays a crucial role in the occurrence and metastasis of tumors. Herein, an antibody modified iridium nanosheet (definition as Ir Nts-Ab) was developed for targeted eradication of CSCs by photoacoustic imaging guided photothermal therapy (PTT) and TME regulation. Ir Nts-Ab with catalase-like activity could inhibit HIF-1α by producing oxygen, thus effectively reducing the proportion of CSCs and inhibiting tumor metastasis. Additionally, Ir Nts-Ab achieved the eradication of CSCs by PTT, and eliminated reactive oxygen species to decrease the inflammatory response, resulting in reduced tumor metastasis, which was promising for the cure of solid tumors in the clinics.

Decoupling of the Confused Complex in Oxidation of 3,3',5,5'-Tetramethylbenzidine for the Reliable Chromogenic Bioassay

Regulation of the reaction pathways is a perennial theme in the field of chemistry. As a typical chromogenic substrate, 3,3',5,5'-tetramethylbenzidine (TMB) generally undertakes one-electron oxidation, but the product (TMBox1) is essentially a confused complex and is unstable, which significantly hampers the clinic chromogenic bioassays for more than 50 years. Herein, we report that sodium dodecyl sulfate (SDS)-based micelles could drive the direct two-electron oxidation of TMB to the final stable TMBox2. Rather than activation of H2O2 oxidant in the one-electron TMB oxidation by common natural peroxidase, activation of the TMB substrate by SDS micelles decoupled the thermodynamically favorable complex between TMBox2 with unreacted TMB, leading to an unusual direct two-electron oxidation pathway. Mechanism studies demonstrated that the complementary spatial and electrostatic isolation effects, caused by the confined hydrophobic cavities and negatively charged outer surfaces of SDS micelles, were crucial. Further cascading with glucose oxidase, as a proof-of-concept application, allowed glucose to be more reliably measured, even in a broader range of concentrations without any conventional strong acid termination.

Mn2+ /Ir3+ -Doped and CaCO3 -Covered Prussian Blue Nanoparticles with Indocyanine Green Encapsulation for Tumor Microenvironment Modulation and Image-Guided Synergistic Cancer Therapy

The development of smart theranostic nanoplatforms has gained great interest in effective cancer treatment against the complex tumor microenvironment (TME), including weak acidity, hypoxia, and glutathione (GSH) overexpression. Herein, a TME-responsive nanoplatform named PMICApt /ICG, based on PB:Mn&Ir@CaCO3 Aptamer /ICG, is designed for the competent synergistic photothermal therapy and photodynamic therapy (PDT) under the guidance of photothermal and magnetic resonance imaging. The nanoplatform's aptamer modification targeting the transferrin receptor and the epithelial cell adhesion molecule on breast cancer cells, and the acid degradable CaCO3 shell allow for effective tumor accumulation and TME-responsive payload release in situ. The nanoplatform also exhibits excellent PDT properties due to its ability to generate O2 and consume antioxidant GSH in tumors. Additionally, the synergistic therapy is achieved by a single wavelength of near-infrared laser. RNA sequencing is performed to identify differentially expressed genes, which show that the expressions of proliferation and migration-associated genes are inhibited, while the apoptosis and immune response gene expressions are upregulated after the synergistic treatments. This multifunctional nanoplatform that responds to the TME to realize the on-demand payload release and enhance PDT induced by TME modulation holds great promise for clinical applications in tumor therapy.

Cascade strategy for glucose oxidase-based synergistic cancer therapy using nanomaterials

Nanomaterial-based cancer therapy faces significant limitations due to the complex nature of the tumor microenvironment (TME). Starvation therapy is an emerging therapeutic approach that targets tumor cell metabolism using glucose oxidase (GOx). Importantly, it can provide a material or environmental foundation for other diverse therapeutic methods by manipulating the properties of the TME, such as acidity, hydrogen peroxide (H2O2) levels, and hypoxia degree. In recent years, this cascade strategy has been extensively applied in nanoplatforms for ongoing synergetic therapy and still holds undeniable potential. However, only a few review articles comprehensively elucidate the rational designs of nanoplatforms for synergetic therapeutic regimens revolving around the conception of the cascade strategy. Therefore, this review focuses on innovative cascade strategies for GOx-based synergetic therapy from representative paradigms to state-of-the-art reports to provide an instructive, comprehensive, and insightful reference for readers. Thereafter, we discuss the remaining challenges and offer a critical perspective on the further advancement of GOx-facilitated cancer treatment toward clinical translation.

Design and Mechanism Insight of Monodispersed AuCuPt Alloy Nanozyme with Antitumor Activity

The abrogation of the self-adaptive redox evolution of tumors is promising for improving therapeutic outcomes. In this study, we designed a trimetallic alloy nanozyme AuCuPt-PpIX (ACPP), which mimics up to five naturally occurring enzymes: glucose oxidase (GOD), superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and glutathione peroxidase (GPx). Facilitated by these enzyme-mimicking traits, the constructed ACPP nanozymes can not only disrupt the established redox homeostasis in tumors through a series of enzymatic cascade reactions but also achieve cyclic regeneration of the relevant enzyme substrates. Density functional theory (DFT) calculations have theoretically explained the synergistic effect of multimetallic doping and the possible mechanism of enzymatic catalysis. The doped Cu and Pt sites are conducive to the adsorption, activation, and dissociation of reactant molecules, whereas the Au sites are conducive to desorption, which significantly improves catalytic efficiency via a synergistic effect. Additionally, ACPP nanozymes can improve the effect of protoporphyrin (PpIX)-enabled sonodynamic therapy (SDT) by alleviating hypoxia and initiating ferroptosis by inducing lipid peroxidation (LPO) and inhibiting GPX4 activity, thus achieving multimodal synergistic therapy. This study presents a typical paradigm to enable the use of multimetallic alloy nanozymes for the treatment of tumor cells with self-adaptive properties.

Sonoactivated Cascade Fenton Reaction Enhanced by Synergistic Modulation of Electron-Hole Separation for Improved Tumor Therapy

Chemodynamic therapy (CDT) is an emerging targeted treatment technique for tumors via the generation of highly cytotoxic hydroxyl radical (·OH) governed by tumor microenvironment-assisted Fenton reaction. Despite high effectiveness, it faces limitations like low reaction efficiency and limited endogenous H2 O2 , compromising its therapeutic efficacy. This study reports a novel platform with enhanced CDT performance by in situ sono-activated cascade Fenton reaction. A piezoelectric g-C3 N4 (Au-Fe-g-C3 N4 ) nanosheet is developed via sono-activated synergistic effect/H2 O2 self-supply mediated cascade Fenton reaction, realizing in situ ultrasound activated cascade Fenton reaction kinetics by synergistic modulation of electron-hole separation. The nanosheets consist of piezoelectric g-C3 N4 nanosheet oxidizing H2 O to highly reactive H2 O2 from the valence band, Fe3+ /Fe2+ cycling activated by conduction band to generate ·OH, and Au nanoparticles that lower the bandgap and further adopt electrons to generate more 1 O2 , resulting in improved CDT and sonodynamic therapy (SDT). Moreover, the Au-Fe-g-C3 N4 nanosheet is further modified by the targeted peptide to obtain P-Au-Fe-g-C3 N4 , which inhibits tumor growth in vivo effectively by generating reactive oxygen species (ROS). These results demonstrated that the sono-activated modulation translates into a high-efficiency CDT with a synergistic effect using SDT for improved anti-tumor therapy.

Smart Nanozymes for Cancer Therapy: The Next Frontier in Oncology

Nanomaterials that mimic the catalytic activity of natural enzymes in the complex biological environment of the human body are called nanozymes. Recently, nanozyme systems have been reported with diagnostic, imaging, and/or therapeutic capabilities. Smart nanozymes strategically exploit the tumor microenvironment (TME) by the in situ generation of reactive species or by the modulation of the TME itself to result in effective cancer therapy. This topical review focuses on such smart nanozymes for cancer diagnosis, and therapy modalities with enhanced therapeutic effects. The dominant factors that guide the rational design and synthesis of nanozymes for cancer therapy include an understanding of the dynamic TME, structure-activity relationships, surface chemistry for imparting selectivity, and site-specific therapy, and stimulus-responsive modulation of nanozyme activity. This article presents a comprehensive analysis of the subject including the diverse catalytic mechanisms of different types of nanozyme systems, an overview of the TME, cancer diagnosis, and synergistic cancer therapies. The strategic application of nanozymes in cancer treatment can well be a game changer in future oncology. Moreover, recent developments may pave the way for the deployment of nanozyme therapy into other complex healthcare challenges, such as genetic diseases, immune disorders, and ageing.

Recent theranostic applications of hydrogen peroxide-responsive nanomaterials for multiple diseases

It is well established that hydrogen peroxide (H2O2) is associated with the initiation and progression of many diseases. With the rapid development of nanotechnology, the diagnosis and treatment of those diseases could be realized through a variety of H2O2-responsive nanomaterials. In order to broaden the application prospects of H2O2-responsive nanomaterials and promote their development, understanding and summarizing the design and application fields of such materials has attracted much attention. This review provides a comprehensive summary of the types of H2O2-responsive nanomaterials including organic, inorganic and organic-inorganic hybrids in recent years, and focused on their specific design and applications. Based on the type of disease, such as tumors, bacteria, dental diseases, inflammation, cardiovascular diseases, bone injury and so on, key examples for above disease imaging diagnosis and therapy strategies are introduced. In addition, current challenges and the outlook of H2O2-responsive nanomaterials are also discussed. This review aims to stimulate the potential of H2O2-responsive nanomaterials and provide new application ideas for various functional nanomaterials related to H2O2.

Antioxidant and Prooxidant Nanozymes: From Cellular Redox Regulation to Next-Generation Therapeutics

Nanozymes, nanomaterials with enzyme-mimicking activity, have attracted tremendous interest in recent years owing to their ability to replace natural enzymes in various biomedical applications, such as biosensing, therapeutics, drug delivery, and bioimaging. In particular, the nanozymes capable of regulating the cellular redox status by mimicking the antioxidant enzymes in mammalian cells are of great therapeutic significance in oxidative-stress-mediated disorders. As the distinction of physiological oxidative stress (oxidative eustress) and pathological oxidative stress (oxidative distress) occurs at a fine borderline, it is a great challenge to design nanozymes that can differentially sense the two extremes in cells, tissues and organs and mediate appropriate redox chemical reactions. In this Review, we summarize the advances in the development of redox-active nanozymes and their biomedical applications. We primarily highlight the therapeutic significance of the antioxidant and prooxidant nanozymes in various disease model systems, such as cancer, neurodegeneration, and cardiovascular diseases. The future perspectives of this emerging area of research and the challenges associated with the biomedical applications of nanozymes are described.

Transferrin-targeted iridium nanoagglomerates with multi-enzyme activities for cerebral ischemia-reperfusion injury therapy

Cerebral ischemia-reperfusion injury (CIRI) is a complex pathological condition with high mortality. In particular, reperfusion can stimulate overproduction of reactive oxygen species (ROS) and activation of inflammation, causing severe secondary injuries to the brain. Despite tremendous efforts, it remains urgent to rationally design antioxidative agents with straightforward and efficient ROS scavenging capability. Herein, a potent antioxidative agent was explored based on iridium oxide nano-agglomerates (Tf-IrO2 NAs) via the facile transferrin (Tf)-templated biomineralization approach, and innovatively applied to treat CIRI. Containing some small-size IrO2 aggregates, these NAs possess intrinsic hydroxyl radicals (•OH)-scavenging ability and multifarious enzyme activities, such as catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPx). Moreover, they also showed improved blood-brain barrier (BBB) penetration and enhanced accumulation in the ischemic brain via Tf receptor-mediated transcytosis. Therefore, Tf-IrO2 NAs achieved robust in vitro anti-inflammatory and cytoprotection effects against oxidative stress. Importantly, mice were effectively protected against CIRI by enhanced ROS scavenging activity in vivo, and the therapeutic mechanism was systematically verified. These findings broaden the idea of expanding Ir-based NAs as potent antioxidative agents to treat CIRI and other ROS-mediated diseases. STATEMENT OF SIGNIFICANCE: (1) The ROS-scavenging activities of IrO2 are demonstrated comprehensively, which enriched the family of nano-antioxidants. (2) The engineering Tf-IrO2 nano-agglomerates present unique multifarious enzyme activities and simultaneous transferrin targeting and BBB crossing ability for cerebral ischemia-reperfusion injury therapy. (3) This work may open an avenue to enable the use of IrO2 to alleviate ROS-mediated inflammatory and brain injury diseases.

Cascade nanozymatic network mimicking cells with selective and linear perception of H2O2

A single stimulus leading to multiple responses is an essential function of many biological networks, which enable complex life activities. However, it is challenging to duplicate a similar chemical reaction network (CRN) using non-living chemicals, aiming at the disclosure of the origin of life. Herein, we report a nanozyme-based CRN with feedback and feedforward functions for the first time. It demonstrates multiple responses at different modes and intensities upon a single H₂O₂ stimulus. In the two-electron cascade oxidation of 3,3',5,5'-tetramethylbenzidine (TMB), the endogenous product H₂O₂ competitively inhibited substrates in the first one-electron oxidation reaction on a single-atom nanozyme (Co-N-CNTs) and strikingly accelerated the second one-electron oxidation reaction under a micellar nanozyme. As a proof-of-concept, we further confined the nanozymatic network to a microfluidic chip as a simplified artificial cell. It exhibited remarkable selectivity and linearity in the perception of H₂O₂ stimulus against more than 20 interferences in a wide range of concentrations (0.01-100 mM) and offered an instructive platform for studying primordial life-like processes.

Highly efficient carbon supported Co-Ir nanozyme for the determination of total antioxidant capacity in foods

Nanozyme-based colorimetric assays have aroused extensive attention in biosensing due to quick response, low cost and simplicity. However, their practical applications are limited by the unsatisfactory stability and catalytic activity of nanozymes in complex detection environments. Herein, using the one-pot chemical vapor deposition method, we successfully prepare a highly efficient and stable carbon supported Co-Ir nanozyme (termed as Co-Ir/C nanozyme) for the determination of total antioxidant capacity (TAC) in food samples. The Co-Ir/C nanozyme shows excellent durability under extensive pH ranges, high temperature and high salt concentration due to the protection of carbon supporter. It can be recycled by simple magnetic separation, and its catalytic activity remains stable after long-term operation and storage. Taking full advantage of the superior peroxidase-like activity of Co-Ir/C nanozyme, it is used for colorimetric detection of ascorbic acid (or known as vitamin C), an important vitamin to adjust body's normal physiological function, with results showing higher sensitivity (detection limit of 0.27 μM) than most of the recently published works. Moreover, the determination of TAC in vitamin C tablets and fruits are further achieved, which are in good agreement with those of commercial colorimetric test kits. This study helps guide the rational preparation of versatile and highly stable nanozymes, and develops a robust TAC determination platform for future food quality monitoring.

From liver fibrosis to hepatocarcinogenesis: Role of excessive liver H2O2 and targeting nanotherapeutics

Liver fibrosis and hepatocellular carcinoma (HCC) have been worldwide threats nowadays. Liver fibrosis is reversible in early stages but will develop precancerosis of HCC in cirrhotic stage. In pathological liver, excessive H₂O₂ is generated and accumulated, which impacts the functionality of hepatocytes, Kupffer cells (KCs) and hepatic stellate cells (HSCs), leading to genesis of fibrosis and HCC. H₂O₂ accumulation is associated with overproduction of superoxide anion (O₂^•−) and abolished antioxidant enzyme systems. Plenty of therapeutics focused on H₂O₂ have shown satisfactory effects against liver fibrosis or HCC in different ways. This review summarized the reasons of liver H₂O₂ accumulation, and the role of H₂O₂ in genesis of liver fibrosis and HCC. Additionally, nanotherapeutics targeting H₂O₂ were summarized for further consideration of antifibrotic or antitumor therapy.

•

Liver fibrosis and HCC are closely related because ROS induced liver damage and inflammation, especially over-cumulated H₂O₂.

•

Excess H₂O₂ diffusion in pathological liver was due to increased metabolic rate and diminished cellular antioxidant systems.

•

Freely diffused H₂O₂ damaged liver-specific cells, thereby leading to fibrogenesis and hepatocarcinogenesis.

•

Nanotherapeutics targeting H₂O₂ are summarized for treatment of liver fibrosis and HCC, and also challenges are proposed.

Engineering Cell Membrane-Cloaked Catalysts as Multifaceted Artificial Peroxisomes for Biomedical Applications

Artificial peroxisomes (APEXs) or peroxisome mimics have caught a lot of attention in nanomedicine and biomaterial science in the last decade, which have great potential in clinically diagnosing and treating diseases. APEXs are typically constructed from a semipermeable membrane that encloses natural enzymes or enzyme-mimetic catalysts to perform peroxisome-/enzyme-mimetic activities. The recent rapid progress regarding their biocatalytic stability, adjustable activity, and surface functionality has significantly promoted APEXs systems in real-life applications. In addition, developing a facile and versatile system that can simulate multiple biocatalytic tasks is advantageous. Here, the recent advances in engineering cell membrane-cloaked catalysts as multifaceted APEXs for diverse biomedical applications are highlighted and commented. First, various catalysts with single or multiple enzyme activities have been introduced as cores of APEXs. Subsequently, the extraction and function of cell membranes that are used as the shell are summarized. After that, the applications of these APEXs are discussed in detail, such as cancer therapy, antioxidant, anti-inflammation, and neuron protection. Finally, the future perspectives and challenges of APEXs are proposed and outlined. This progress review is anticipated to provide new and unique insights into cell membrane-cloaked catalysts and to offer significant new inspiration for designing future artificial organelles.

Redox Imbalance Triggered Intratumoral Cascade Reaction for Tumor "turn on" Imaging and Synergistic Therapy

The redox homeostasis in tumors enhances their antioxidant defense ability, limiting reactive oxygen species mediated tumor therapy efficacy. The development of strategies for specific and continuous disruption of the redox homeostasis in tumor cells facilitates the improvement of the cancer therapeutic effect by promoting the apoptosis of tumor cells. Herein, a responsively biodegradable targeting multifunctional integrated nanosphere (HDMn-QDs/PEG-FA) is designed to enhance the anti-tumor efficacy by triggering intratumoral cascade reactions to effectively disrupt intracellular redox homeostasis. Once HDMn-QDs/PEG-FA enters tumor cells, manganese dioxide (MnO₂ ) shell on the surface of nanosphere consumes glutathione (GSH) to produce Mn²⁺ , enabling enhanced chemodynamic therapy (CDT) via a Fenton-like reaction and T₁ -weighted magnetic resonance imaging. Meanwhile, the degradation of MnO₂ can also cause the fluorescence recovery of quantum dots conjugated on the surface of the shell, realizing "turn-on" fluorescence imaging. In addition, the doxorubicin is released because of the cleavage of the embedded SS bond in the hybrid core framework by GSH. A superior synergistic therapeutic efficiency combined CDT and chemotherapy is shown by HDMn-QDs/PEG-FA in vivo. The tumor-inhibition rate reaches to 94.8% and does not cause normal tissue damage due to the good targeting and tumor microenvironment-specific response.

A pH-Activatable Copper-Biomineralized Proenzyme for Synergistic Chemodynamic/Chemo-Immunotherapy against Aggressive Cancers

Artificial enzymes have demonstrated therapeutic benefits against diverse malignant tumors, yet their antitumor potencies are still severely compromised by non-selective catalysis, low atomic-utilization efficiency, and undesired off-target toxicity. Herein, it is reported that peroxidase-like biomineralized copper (II) carbonate hydroxide nanocrystals inside single albumin nanocages (CuCH-NCs) act as a pH-activatable proenzyme to achieve tumor-selective and synergistic chemodynamic/chemo-immunotherapy against aggressive triple-negative breast cancers (TNBCs). These CuCH-NCs show pH-sensitive Cu²⁺ release, which spontaneously undergoes glutathione (GSH)-mediated reduction into Cu⁺ species for catalyzing the evolution of H₂ O₂ into hydroxyl radicals (·OH) in a single-atom-like manner to cause chemodynamic cell injury, and simultaneously activates non-toxic disulfiram to cytotoxic complex for yielding selective chemotherapeutic damage via blocking cell proliferation and amplifying cell apoptosis. CuCH-NCs exhibit considerable tumor-targeting capacity with deep penetration depth, thus affording preferable efficacy against orthotopic breast tumors through synergistic chemodynamic/chemotherapy, together with good in vivo safety. Moreover, CuCH-NCs arouse distinct immunogenic cell death effect and upregulate PD-L1 expression upon disulfiram combination, and thus synergize with anti-PD-L1 antibody to activate adaptive and innate immunities, together with relieving immunosuppression, finally yielding potent antitumor efficacy against both primary and metastatic TNBCs. These results provide insights into smart and high-performance proenzymes for synergistic therapy against aggressive cancers.

Platinum-Nickel Nanoparticles with Enhanced Oxidase-like Activity for Total Antioxidant Capacity Bioassay

While great progress in nanozyme-enabled analytical chemistry has been made, most current nanozyme-based biosensing platforms are based on peroxidase-like nanozymes. However, peroxidase-like nanozymes with multienzymatic activities can influence the detection sensitivity and accuracy, while the use of unstable hydrogen peroxide (H₂O₂) in a peroxidase-like catalytic reaction may result in the reproducibility challenge of sensing signals. We envision that constructing biosensing systems by using oxidase-like nanozymes can address these limitations. Herein, we reported that platinum-nickel nanoparticles (Pt-Ni NPs) with Pt-rich shells and Ni-rich cores possessed high oxidase-like catalytic efficiency, exhibiting a 2.18-fold higher maximal reaction velocity (v_max) than initial pure Pt NPs. The oxidase-like Pt-Ni NPs were applied to develop a colorimetric assay for the determination of total antioxidant capacity (TAC). The antioxidant levels of four bioactive small molecules, two antioxidant nanomaterials, and three cells were successfully measured. Our work not only provides new insights for preparing highly active oxidase-like nanozymes but also manifests their applications for TAC analysis.

Integrating Incompatible Nanozyme-Catalyzed Reactions for Diabetic Wound Healing

Multi-nanozymes are widely applied in disease treatment, biosensing, and other fields. However, most current multi-nanozyme systems exhibit only moderate activity since reaction microenvironments of different nanozyme are often distinct or even incompatible. Conventional assemble strategies are inapplicable for designing multi-nanozymes consisting of incompatible nanozymes. Herein, a versatile fiber-based compartmentalization strategy is developed to construct multi-nanozyme system capable of simultaneously performing incompatible reactions. In this system, the incompatible nanozymes are spatially distributed in distinct compartmentalized fibers, where different microenvironments can be tailored by controlling the doping reagent, endowing each nanozymes with the preferential microenvironments to exhibit their highest activity. As a proof of concept, pH-incompatible peroxidase-like and catalase-like catalytic reactions are tested to verify the feasibility of this strategy. By doping with benzoic acid in the desired location, the two pH-incompatible nanozymes can work simultaneously without interference. Further, it is demonstrated that the oxygen supply and antimicrobial power of the integrated platform can be applied for accelerating diabetic wound healing. It is hoped that this work provides a way to integrate incompatible nanozyme and broadens the application potential of multi-nanozymes.

Single-Atom Nanozyme with Asymmetric Electron Distribution for Tumor Catalytic Therapy by Disrupting Tumor Redox and Energy Metabolism Homeostasis

Nanozyme catalytic therapy triggered by tumor-specific endogenous stimuli is an emerging tumor therapy that attracts wide attention. However, the current therapeutic efficacy of nanozyme catalytic therapy is severely limited by the catalytic efficiency of nanozymes and the concentration of endogenous reaction substrates. Herein, a novel and efficient IrN₅ single-atom (IrN₅ SA) nanozyme is developed with multiple enzyme-like catalytic activities. Due to the synergistic effect of central Ir single-atom and axial N coordination, IrN₅ SA exhibits better enzymatic catalytic performance than IrN₄ SA. At tumor sites, IrN₅ SA can generate a large amount of reactive oxygen species (ROS) through oxidase (OXD)-like and peroxidase (POD)-like catalytic activities. Moreover, IrN₅ SA can also generate O₂ and hydrogen peroxide (H₂ O₂ ) through catalase (CAT)-like and nicotinamide adenine dinucleotide (NADH) oxidase (NOX)-like catalytic activities, realizing the efficient nanozyme catalytic therapy in a substrate-cycle manner. Additionally, IrN₅ SA can effectively break the intracellular NADH/NAD⁺ cycle balance by mimicking NOX, and then cooperate with fatty acid synthase cerulenin (Cer) to interfere with the energy metabolism homeostasis of tumor cells. Consequently, the designed IrN₅ SA/Cer nanoagent can disrupt redox and metabolic homeostasis in the tumor region through an enzyme-mimicking cascade reaction, effectively overcoming the shortcomings of current nanozyme catalytic therapy.

Molecular insights of nanozymes from design to catalytic mechanism

Emerging as cost-effective potential alternatives to natural enzymes, nanozymes have attracted increasing interest in broad fields. To exploit the in-depth potential of nanozymes, rational structural engineering and explicit catalytic mechanisms at the molecular scale are required. Recently, impressive progress has been made in mimicking the characteristics of natural enzymes by constructing metal active sites, binding pockets, scaffolds, and delicate allosteric regulation. Ingenious in-depth studies have been conducted with advances in structural characterization and theoretical calculations, unveiling the "black box" of nanozyme-catalytic mechanisms. This review introduces the state-of-art synthesis strategies by learning from the natural enzyme counterparts and summarizes the general overview of the nanozyme mechanism with a particular emphasis on the adsorbed intermediates and descriptors that predict the nanozyme activity The emerging activity assessment methodology that illustrates the relationship between electrochemical oxygen reduction and enzymatic oxygen reduction is discussed with up-to-date advances Future opportunities and challenges are presented in the end to spark more profound work and attract more researchers from various backgrounds to the flourishing field of nanozymes.

Carbon Dot@MXene Nanozymes with Triple Enzyme-Mimic Activities for Mild NIR-II Photothermal-Amplified Nanocatalytic Therapy

Nanozymes have shown promising potential in disease treatment owing to the advantages of low-cost, facile fabrication, and high stability. However, the highly complex tumor microenvironment (TME) and inherent low catalytic activity severely restrict the clinical applications of nanozymes. Herein, a novel mild hyperthermia-enhanced nanocatalytic therapy platform based on Z-scheme heterojunction nanozymes by depositing N-doped carbon dots (CDs) onto Nb₂ C nanosheets is constructed. CD@Nb₂ C nanozymes not only display outstanding photothermal effects in the safe and efficient NIR-II window but also possess triple enzyme-mimic activities to obtain amplified ROS levels. The triple enzyme-mimic activities and NIR-II photothermal properties of CD nanozymes are enhanced by the construction of Z-scheme heterojunctions owing to the accelerated carrier transfer process. More importantly, the introduction of mild hyperthermia can further improve the peroxidase-mimic and catalase-mimic activities as well as the glGSH depletion abilities of CD@Nb₂ C nanozymes, thereby producing more ROS to efficiently inhibit tumor growth. The combined therapy effect of CD@Nb₂ C nanozymes through mild NIR-II photothermal-enhanced nanocatalytic therapy can achieve complete tumor eradication. This work highlights the efficient tumor therapy potential of heterojunction nanozymes.

Mesoporous carbon nanoenzyme as nano-booster for photothermal-enhanced photodynamic therapy compared with graphene oxide

The over-expressed GSH in tumor microenvironment significantly weakens the lethal reactive oxygen species (ROS) generated by photodynamic therapy (PDT) and catalysis of nanoenzyme. Hence, it is necessary to excavate a versatile and effective vehicle with oxidative stress-enhancement and GSH-depletion capacity to break the redox homeostasis in tumor microenvironment. GO has been reported to possess GSH-depletion and peroxidase (POD)-like capacity. Based on this, PEGylated mesoporous carbon (MC-PEG) was prepared as ICG vehicle to compare with PEGylated graphene oxide (GO-PEG). Excitingly, MC-PEG was found to exhibit three times higher oxidative capacity by POD-like process than GO-PEG, and owned more effective and continuous GSH-depletion capacity to further amplify the oxidative stress. Meanwhile, MC-PEG exhibited better protective effect on the loaded ICG against unwanted light excitation than GO-PEG. Together with the higher photothermal conversion effect, under the NIR light irradiation, MC-PEG could markedly improve the temperature of tumor cells and produce more hydroxyl radical, continuously consume GSH and provide more better protection for ICG compared with GO-PEG, thus further boosting the combination of photothermal and photodynamic effects. The anti-tumor experiment in cell and in-vivo level both validated that ICG/MC-PEG showed better synergistic effect with lower IC₅₀ value and higher tumor suppression rate than ICG/GO-PEG.

A metabolic intervention strategy to break evolutionary adaptability of tumor for reinforced immunotherapy

The typical hallmark of tumor evolution is metabolic dysregulation. In addition to secreting immunoregulatory metabolites, tumor cells and various immune cells display different metabolic pathways and plasticity. Harnessing the metabolic differences to reduce the tumor and immunosuppressive cells while enhancing the activity of positive immunoregulatory cells is a promising strategy. We develop a nanoplatform (CLCeMOF) based on cerium metal-organic framework (CeMOF) by lactate oxidase (LOX) modification and glutaminase inhibitor (CB839) loading. The cascade catalytic reactions induced by CLCeMOF generate reactive oxygen species "storm" to elicit immune responses. Meanwhile, LOX-mediated metabolite lactate exhaustion relieves the immunosuppressive tumor microenvironment, preparing the ground for intracellular regulation. Most noticeably, the immunometabolic checkpoint blockade therapy, as a result of glutamine antagonism, is exploited for overall cell mobilization. It is found that CLCeMOF inhibited glutamine metabolism-dependent cells (tumor cells, immunosuppressive cells, etc.), increased infiltration of dendritic cells, and especially reprogrammed CD8⁺ T lymphocytes with considerable metabolic flexibility toward a highly activated, long-lived, and memory-like phenotype. Such an idea intervenes both metabolite (lactate) and cellular metabolic pathway, which essentially alters overall cell fates toward the desired situation. Collectively, the metabolic intervention strategy is bound to break the evolutionary adaptability of tumors for reinforced immunotherapy.

Glucose metabolism-inspired catalytic patches for NIR-II phototherapy of diabetic wound infection

Medical patches hold great prospects for diabetic wound administration, while their practical effects in diabetic wound management remain mired by the complexity of wound microenvironments. Here, inspired by the biological processes of glucose metabolism, we present a catalytic microneedle patch that encapsulates near-infrared-II responsive and dual-nanozyme active Au-Cu₂MoS₄ nanosheets (Au-CMS NSs) for treating diabetic wound infection. Since microneedle patches have great tissue penetration ability, the Au-CMS NSs can be delivered to deep tissues and fully interact with wound environments. Benefitting from the dual nanozyme activities (glucose oxidase and catalase) and near-infrared-II photothermal performances of Au-CMS NSs, the composited catalytic patch realizes in situ glucose consumption, oxygen generation, and bacterial elimination. Notably, their repeatability of near-infrared-II responsive antibacterial capability has been proved both in vitro and in diabetic mice against methicillin-resistant Staphylococcus aureus. The catalytic patch can find wide catalytic applications in wound care and infection prevention. STATEMENT OF SIGNIFICANCE: Effective treatment of diabetic wound infection remains still challenging in the clinic owing to the complex wound microenvironments. Herein, inspired by the biological processes of glucose metabolism in lives, we propose a novel strategy to treat wound infections by modulating the diabetic wound microenvironments. A near-infrared-II (NIR-II) responsive biocatalytic microneedle patch with both glucose oxidase- and catalase-like activities capable of killing bacteria, reducing glucose level, and supplying O₂ is developed. The patch not only achieves efficient antibacterial outcomes in vitro, but also is a valuable wound patch for efficient treatment of MRSA-infected wounds in diabetic mice. We anticipate that this therapeutic strategy will provide the applications in chronic inflammation and infections.

Amorphous NiB@IrOx nanozymes trigger efficient apoptosis-ferroptosis hybrid therapy

The apoptosis-ferroptosis hybrid therapy opens up a new avenue for tumor eradication. Constructing efficient self-cascade platform is highly desired to enhance its therapeutic effect. Herein, we report on the synthesis of novel nanozyme consist of amorphous NiB alloy completely coated with an ultrathin layer of IrOx shell (A-NiB@C-IrO_x). These core-shell nanoparticles exhibited peroxidase (POD)-, catalase (CAT)- and glutathione oxidase (GSH-OXD)-like properties for inducing self-cascade catalysis. Specifically, the amorphous IrO_x shell with abundant active sites can effectively convert intratumor hydrogen peroxide (H₂O₂) to cytotoxic reactive oxygen species (ROS) and oxygen (O₂). In presence of O2, amorphous NiB core and ultrathin IrOx shell collectively catalyze the oxidation of GSH to generate H₂O₂, which is subsequently converted to ROS and O₂ by IrO_x component. Thus, these enzymatic activities endow A-NiB@C-IrO_x nanozymes with the ability of unceasing generation of ROS and O₂ and depletion of GSH. In vitro and in vivo studies demonstrate a high therapeutic efficiency of A-NiB@C-IrO_x nanozymes via apoptosis-ferroptosis combination therapy. STATEMENT OF SIGNIFICANCE: Apoptosis-ferroptosis hybrid therapy opens up new avenues for eradicating tumor cells. However, its actual therapeutic effect is still unsatisfied. Current efforts on this hybrid therapy focus on developing efficient self-cascade nanozymes to improve the efficiency of both ROS generation and GSH depletion. In this study, we constructed amorphous NiB alloy with a completed thin layer of IrO_x shell (denoted as A-NiB@C-IrO_x) for apoptosis-ferroptosis combination therapy. As expected, A-NiB@C-IrO_x can trigger efficient cascade catalytic reactions to continuously generate ROS and consume GSH, finally inducing augmented apoptosis-ferroptosis combination therapy.

Modulating Nanozyme-Based Nanomachines via Microenvironmental Feedback for Differential Photothermal Therapy of Orthotopic Gliomas

Gliomas are common and refractory primary tumors closely associated with the fine structures of the brain. Photothermal therapy (PTT) has recently shown promise as an effective treatment for gliomas. However, nonspecific accumulation of photothermal agents may affect adjacent normal brain structures, and the inflammatory response induced during PTT may result in an increased risk of brain tumor recurrence or metastasis. Here, the design and fabrication of an intelligent nanomachine is reported based on Gd₂ O₃ @Ir/TMB-RVG29 (G@IT-R) hybrid nanomaterials. These nanomaterials enable tumor-specific PTT and eliminate inflammation to protect normal brain tissue. The mechanism involves the rabies virus glycopeptide-29 peptide (RVG29) passing through the blood-brain barrier (BBB) and targeting gliomas. In the tumor microenvironment, Ir nanozymes can act as logic control systems to trigger chromogenic reaction amplification of 3,3',5,5'-tetramethylbenzidine (TMB) for tumor-specific PTT, whereas in normal brain tissues, they scavenge reactive oxygen species (ROS) generated by poor therapy and function as protective agents. Autophagy inhibition of Gd₂ O₃ enables excellent photothermal therapeutic effects on orthotopic gliomas and protection against inflammation in normal cells. The results of this study may prove useful in developing highly efficient nanomedicines for glioma treatment.

A Cell Selective Fluoride-Activated MOF Biomimetic Platform for Prodrug Synthesis and Enhanced Synergistic Cancer Therapy

As a burgeoning bioorthogonal reaction, the fluoride-mediated desilylation is capable of prodrug activation. However, due to the reactions lack of cell selectivity and unitary therapy modality, this strongly impedes their biomedical applications. Herein, we construct a cancer cell-selective biomimetic metal-organic framework (MOF)-F platform for prodrug activation and enhanced synergistic chemodynamic therapy (CDT). With cancer cell membranes camouflage, the designed biomimetic nanocatalyst displays preferential accumulation to homotypic cancer cells. Then, pH-responsive nanocatalyst releases fluoride ions and ferric ions. For activation of our designed prodrug tert-butyldimethyl silyl (TBS)-hydroxycamptothecin (TBSO-CPT), fluoride ions can desilylate TBS and cleave the designed silyl ether linker to synthesize the OH-CPT (10-hydroxycamptothecin) drug molecule, which effectively kills cancer cells. Intriguingly, the bioorthogonal-synthesized OH-CPT drug upregulates intracellular H₂O₂ by activating nicotinamide adenine dinucleotide phosphate oxidase (NOX), amplifying the released iron induced Fenton reaction for synergistic CDT. Both in vitro and in vivo studies demonstrate our strategy presents a versatile fluoride-activated bioorthogonal catalyst for cancer cell-selective drug synthesis. Our work may accelerate the biomedical applications of fluoride-activated bioorthogonal chemistry.

Photo-induced stress relaxation in reconfigurable disulfide-crosslinked supramolecular films visualized by dynamic wrinkling

Stress relaxation in reconfigurable supramolecular polymer networks is strongly related to intermolecular behavior. However, the relationship between molecular motion and macroscopic mechanics is usually vague, and the visualization of internal stress reflecting precise regulation of molecules remains challenging. Here, we present a strategy for visualizing photo-driven stress relaxation induced by infinitesimal perturbations in the intermolecular exchange reaction via reprogrammable wrinkle patterns. The supramolecular films exhibit visible changes in microscopic wrinkle topography through ultraviolet (UV)-induced dynamic disulfide exchange reaction. In accordance with the trans-scale theoretical models, which quantitatively evaluate the chemical-dependent mechanical stresses in the supramolecular network, the unexposed disordered wrinkles evolved into highly oriented patterns and underwent subsequent mutations after thermal treatment. The stress-sensitive wrinkle macro-patterns can be repetitively written/erased through network topology rearrangement using different stimuli. This strategy provides an approach for visualizing and understanding the molecular behavior from dynamic chemistry to mechanical changes, and directly programming wrinkle patterns with regulated structures.

Bioactive Iridium Nanoclusters with Glutathione Depletion Ability for Enhanced Sonodynamic-Triggered Ferroptosis-Like Cancer Cell Death

Ferroptosis is a regulated form of necrotic cell death that involves the accumulation of lipid peroxide (LPO) species in an iron- and reactive oxygen species (ROS)-dependent manner. Previous investigations have reported that ferroptosis-based cancer therapy can overcome the limitations of traditional therapeutics targeting the apoptosis pathway. However, it is still challenging to enhance the antitumor efficacy of ferroptosis due to intrinsic cellular regulation. In this study, a ferroptosis-inducing agent, i.e., chlorin e6 (Ce6)-conjugated human serum albumin-iridium oxide (HSA-Ce6-IrO₂ , HCIr) nanoclusters, is developed to achieve sonodynamic therapy (SDT)-triggered ferroptosis-like cancer cell death. The sonosensitizing role of both Ce6 and IrO₂ within the HCIr nanoclusters exhibits highly efficient ¹ O₂ generation capacity upon ultrasound stimulation, which promotes the accumulation of LPO and subsequently induces ferroptosis. Meanwhile, the HCIr can deplete glutathione (GSH) by accelerating Ir (IV)-Ir (III) transition, which further suppresses the activity of glutathione peroxidase 4 (GPX4) to enhance the ferroptosis efficacy. Through in vitro and in vivo experiments, it is demonstrated that HCIr possesses tremendous capacity to reduce the intracellular GSH content, which enhances SDT-triggered ferroptosis-like cancer cell death. Thus, an iridium-nanoclusters-based ferroptosis-inducing agent is developed, providing a promising strategy for inducing ferroptosis-like cancer cell death.

Combining Cobalt Ferrite Nanozymes with a Natural Enzyme to Reshape the Tumor Microenvironment for Boosted Cascade Enzyme-Like Activities

Nanozymes with the merits of effective enzyme-mimic activities, tunable catalytic properties, pH/temperature tolerance, and high stability have been consumingly researched for nanocatalytic therapy. Herein, the union nanozymes and a natural enzyme nanoplatform (DMSN@CoFe₂O₄/GOD-PCM) are elaborately designed by simply depositing an ultrasmall cobalt ferrite (CoFe₂O₄) bimetallic oxide nanozyme and natural glucose oxidase (GOD) that are loaded into the aperture (∼12 nm) of dendritic mesoporous silica (DMSN) for near-infrared-II-enhanced tumor therapy. Upon irradiation, the hyperthermia generated by CoFe₂O₄ nanozymes unlocks the "gate" of phase-change material (PCM) for releasing GOD, which reshapes the specific tumor microenvironment (TME) through the glucose metabolism pathway. The resulting strengthened acid condition and a considerable amount of H₂O₂ efficiently initiate the cascade catalysis reactions. Moreover, highly toxic hydroxyl radicals are generated with a Co/Fe dual-cycle system of ultrasmall CoFe₂O₄ nanozymes. The in situ glutathione consumption and hypoxia relief further amplify oxidative stress. In addition, chemotherapeutic effects due to the cytotoxicity of cobalt ions enhance the therapeutic performance. Collectively, this study provides a proof of concept for TME-reshaped natural and artificial nanozyme cascade catalysis for combined reactive oxygen species-based therapy and chemotherapy.

Modulation of the Tumor Immune Microenvironment by Bi2 Te3 -Au/Pd-Based Theranostic Nanocatalysts Enables Efficient Cancer Therapy

Nanozymes with multienzyme-mimicking activities have shown great potential in cancer therapy due to their ability to modulate the complex tumor microenvironment (TME). Herein, a second near-infrared (NIR-II) photothermal-nanocatalyst by decorating Bi₂ Te₃ nanosheets with ultrasmall Au/Pd bimetallic nanoparticles (Bi₂ Te₃ -Au/Pd) to reverse the immunosuppressive TME is developed. The peroxidase (POD)-like and catalase (CAT)-like activities, and glutathione (GSH) consumption capacity of Au/Pd modulates the TME by disrupting the intracellular redox homeostasis and relieving hypoxia in the TME. Notably, the amplified oxidative stress induces the accumulation of lipid hydroperoxides (LPO) for enhanced ferroptosis. Moreover, upon NIR-II photoirradiation at 1064 nm, the localized heat generated by Bi₂ Te₃ not only directly ablates the cancer cells but also enhances the Au/Pd-mediated catalysis-mediated cancer therapy. Furthermore, both in vitro and in vivo studies confirm that the Bi₂ Te₃ -Au/Pd nanocatalysts (BAP NCs) can effectively suppress tumor growth by inducing immunogenic cell death (ICD), and suppressing metastasis and recurrence by the synergistic treatment. Overall, this study provides a promising theranostic strategy for effective tumor inhibition.

Catalase-Like Nanozymes: Classification, Catalytic Mechanisms, and Their Applications

The field of nanozymes has developed rapidly over the past decade. Among various oxidoreductases mimics, catalase (CAT)-like nanozyme, acting as an essential part of the regulation of reactive oxygen species (ROS), has attracted extensive research interest in recent years. However, CAT-like nanozymes are not as well discussed as other nanozymes such as peroxidase (POD)-like nanozymes, etc. Compared with natural catalase or artificial CAT enzymes, CAT-like nanozymes have unique properties of low cost, size-dependent properties, high catalytic activity and stability, and easy surface modification, etc., which make them widely used in various fields, especially in tumor therapy and disease treatment. Consequently, there is a great requirement to make a systematic discussion on CAT-like nanozymes. In this review, some key aspects of CAT-like nanozymes are deeply summarized as: 1) Typical CAT-like nanozymes classified by different nanomaterials; 2) The catalytic mechanisms proposed by experimental and theoretical studies; 3) Extensive applications in regard to tumor therapy, cytoprotection and sensing. Therefore, it is prospected that this review will contribute to the further design of CAT-like nanozymes and optimize their applications with much higher efficiency than before.