A Single-Atom Manganese Nanozyme Mn-N/C Promotes Anti-Tumor Immune Response via Eliciting Type I Interferon Signaling

TME-responsive nanocomposite hydrogel with targeted capacity for enhanced synergistic chemoimmunotherapy of MYC-amplified osteosarcoma

The oncogene MYC is one of the most commonly activated oncogenic proteins in human tumors, with nearly one-fourth of osteosarcoma showing MYC amplification and exhibiting the worst clinical outcomes. The clinical efficacy of single radiotherapy, chemotherapy, and immunotherapy for such osteosarcoma is poor, and the dysregulation of MYC amplification and immune-suppressive tumor microenvironment (TME) may be potential causes of anti-tumor failure. To address the above issues, we developed an injectable TME-responsive nanocomposite hydrogel to simultaneously deliver an effective MYC inhibitor (NHWD-870) and IL11Rα-targeted liposomes containing cisplatin-loaded MnO2 (Cis/Mn@Lipo-IL11). After in situ administration, NHWD-870 effectively degrades MYC and downregulates CCL2 and IL13 cytokines to trigger M1 type activation of macrophages. Meanwhile, targeted delivery of Cis/Mn@Lipo-IL11 reacts with excess intratumoral GSH to generate Mn2+ and thus inducing excess active oxygen species (ROS) production through Fenton-like reaction, along with cisplatin, thereby inducing immunogenic cell death (ICD) to promote dendritic cell maturation. Through synergistic regulation of MYC and ICD levels, the immune microenvironment was reshaped to enhance immune infiltration. In the osteosarcoma-bearing model, the nanocomposite hydrogel significantly enhanced tumor T cell infiltration, induced effective anti-tumor immunity and attenuated lung metastasis. Therefore, our results reveal a powerful strategy for targeted combination therapy of MYC-amplified osteosarcoma.

Single-atom nanozymes for enhanced electrochemical biosensing: A review

Enzyme-based electrochemical biosensors have broad and significant applications in biomedical, environmental monitoring, and food safety fields. However, the application of natural enzymes is limited due to issues such as poor stability, complex preparation, and high cost. Single-atom nanozymes (SAzymes), with their unique catalytic properties and efficient enzyme-like activities, present a promising alternative in the field of electrochemical biosensing. Compared to traditional enzymes, SAzyme offer enhanced stability and controllability, making them particularly effective in complex detection environments. This work presents the first systematic review of the progress made since 2018 in the use of SAzymes as alternatives to natural enzymes in electrochemical biosensors, and presents the latest advancements in this area. The review begins with a discussion of various enzyme-like activities of single-atom materials, including peroxidase (POD)-like, oxidase (OXD)-like, catalase (CAT)-like, and superoxide dismutase (SOD)-like activities. It then explores the advantages of SAzymes in improving the performance of electrochemical biosensors from multiple perspectives. The review also summarizes the applications of SAzyme-based electrochemical sensors for reactive oxygen species (ROS), metabolites, neurotransmitters, and other analytes, highlighting specific examples to elucidate underlying catalytic mechanisms and understand fundamental structure-performance relationships. In the final section, the challenges faced by SAzyme-based electrochemical biosensing are discussed, along with potential solutions.

Nano drug delivery systems for advanced immune checkpoint blockade therapy

Immune checkpoint inhibitors (ICIs) have been widely utilized in the first-line therapy of various types of cancer. However, immune-related adverse events (irAEs) and resistance to ICIs remain intractable challenges for immune checkpoint blockade (ICB) therapy during clinic treatment. Nano drug delivery systems (NDDSs) have shown promising potential to improve anticancer efficacy and reduce side effects of small molecular drugs. The combination of nanotechnology and ICB provides new opportunities to overcome the challenges of immunotherapy. Nanoplatforms have been employed for direct delivery of ICIs, and they are preferred vehicles for combination therapy of ICIs and other therapeutic agents. In this review, the strategies of using NDDSs for advancing ICB therapy in recent years are surveyed, emphasizing the employment of NDDSs for combination treatment by ICIs and other agents to manipulate antitumor immunity. Analysis of current strategies for applying NDDSs for ICB leads to future research directions and development trends.

Dual-modality immune nano-activator harnessing Mn2⁺ and quercetin to potentiate the cGAS-STING pathway for advanced cancer metalloimmunotherapy

Manganese ions (Mn2+) have emerged as promising activators of the cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway. However, their clinical application was hindered by low bioavailability and limited immune activation pathways, which impaired their ability to trigger robust immune responses and achieve significant antitumor effects. To address these challenges, we developed a dual-modality immune nano-activator by coordinating manganese ions with quercetin. This strategy was designed to enhance the cGAS-STING pathway activation and elicit the immunogenic cell death, thereby strengthening the antitumor immune response. The engineered nano-activator demonstrated superior tumor-targeting ability and efficient cellular internalization. Upon exposure to near-infrared irradiation, the system harnessed photothermal effects to induce apoptosis in tumor cells while simultaneously accelerating the release of manganese ions and quercetin. The released manganese ions facilitated the generation of reactive oxygen species, which in conjunction with quercetin-induced apoptosis, amplified photothermal-induced DNA damage. This DNA damage further promoted the release of cytosolic DNA, which in turn activated the cGAS-STING pathway, thereby intensifying immune activation. Notably, the nano-activator also triggered immunogenic cell death, which synergized with the cGAS-STING activation to promote dendritic cell maturation and activate antigen-specific T-cell, significantly enhancing the immune response against the tumor. Both in vitro and in vivo studies confirmed that this nano-activator effectively inhibited tumor growth, with particularly pronounced effects when combined with anti-CTLA-4 antibodies.

Boosting Peroxidase-Mimetic Activity of FeMn-NCe Dual-Atom Radiosensitizing Nanozymes for Augmented Radiodynamic Immunotherapy

Dual-atom nanozymes (DAzymes) have garnered considerable attention as catalysts for reactive oxygen species (ROS)-based therapies, effectively leveraging ROS generation within the tumor microenvironment (TME). Herein, we introduce the FeMn-NCe DAzymes, which are meticulously engineered for enhanced peroxidase (POD)-mimetic activity and potent radiosensitization to advance radioimmunotherapy. Density functional theory (DFT) calculations reveal that FeMn-NCe DAzymes lower the energy barrier and increase the substrate affinity, enabling highly efficient catalytic performance. Within the TME, these DAzymes efficiently convert overexpressed hydrogen peroxide (H2O2) into hydroxyl radicals (•OH), potentially activating the cGAS-STING immune pathway. This POD-mimetic catalysis is further accelerated under X-ray irradiation, significantly enhancing radiosensitization. Additionally, a uniform coating of ultrasmall gold nanoparticles on FeMn-NCe significantly enhances X-ray absorption within cancer cells. The incorporation of the STING agonist diABZI onto the DAzymes induces long-term antitumor immunity, reprograms the immunosuppressive TME, and effectively suppresses tumor growth and metastasis following a single low-dose X-ray treatment. This work highlights a valuable strategy for designing DAzymes to advance radiodynamic immunotherapy.

Tumor Microenvironment-Driven Structural Transformation of Vanadium-Based MXenzymes to Amplify Oxidative Stress for Multimodal Tumor Therapy

MXenzymes, a promising class of catalytic therapeutic material, offer great potential for tumor treatment, but they encounter significant obstacles due to suboptimal catalytic efficiency and kinetics in the tumor microenvironment (TME). Herein, this study draws inspiration from the electronic structure of transition metal vanadium, proposing the leverage of TME specific-features to induce structural transformations in sheet-like vanadium carbide MXenzymes (TVMz). These transformations trigger cascading catalytic reactions that amplify oxidative stress, thereby significantly enhancing multimodal tumor therapy. Specifically, the engineered HTVMz, coated with hyaluronic acid, exhibits good stability and generates a thermal effect under NIR-II laser irradiation. The thermal effect, combined with TME characteristics, facilities a structural transformation into ultra-small vanadium oxide nanozymes (VOx). The enlarged surface area of VOx substantially enhances ROS regeneration and amplifies oxidative stress, which promotes lysosomal permeability and induces endoplasmic reticulum stress. The high-valent vanadium in VOx interacts with intracellular glutathione, disrupting redox homeostasis and intensifying oxidative stress further. These amplifications accelerate tumor apoptosis, induce ferroptosis, and suppress HSP90 expression. Consequently, the heightened thermal sensitivity of HTVMz synergistically promotes tumor cell death via multimodal therapeutic pathways. This study presents an innovative strategy for tumor catalytic therapy by manipulating MXenzymes structures, advancing the field of catalytic therapy.

A Single-Atom Mn/MoO3- x Nanoagonist for Cascade cGAS/STING Activation in Tumor-Specific Catalytic Metalloimmunotherapy

The cyclic GMP-AMP synthase (cGAS)/stimulator of interferon genes (STING) pathway plays a crucial role in initiating anti-tumor immunity. Despite the development of various STING agonists, their effectiveness is often limited by suboptimal activation efficiency and poor sustainability. To address this, a Mn/MoO3- x nanoagonist featuring Mn single-atom sites is presented, designed for cascade cGAS/STING activation in tumor-specific catalytic metalloimmunotherapy. The single-atom nanoagonist (SANA) is meticulously crafted by doping Mn atoms into defective molybdenum oxide (MoO3- x), enabling robust peroxidase-mimicking catalysis and inducing severe double-stranded DNA (dsDNA) damage in tumors. Of note, Mn2+ and MoO4 2- can be responsively released from Mn/MoO3- x SANA and enhance the sensitivity of cGAS to dsDNA. Importantly, MoO4 2- with a relatively slow-release profile and facile cellular accumulation compensates for Mn2+ that has poor cellular accumulation due to continuous efflux, thus continuatively triggering the secretion of type I interferon for beyond 72 h. Remarkably, Mn/MoO3- x SANA significantly inhibits tumor growth and metastasis without supplementary STING agonists or external stimulation. This study offers a promising cascade cGAS/STING activation approach to enhance the efficacy and sustainability of catalytic metalloimmunotherapy.

Ce Single Atom with Cascaded Self-Circulating Enzyme-Like Activities and Photothermal Activities for Cancer Therapy

Specific regulation of the tumor microenvironment (TME) is a potential strategy for tumor therapy. Although many TME-responsive nanozymes have been developed for tumor therapy, the limited substrates affect the therapeutic effect. In this study, cerium single-atom nanozymes (Ce SAs) are prepared by immobilizing cerium (Ce) using zeolitic imidazolate framework-8 (ZIF-8) as a precursor. The reversible conversion between Ce3+ and Ce4+ endows Ce SAs with multiple enzyme-like activities, such as peroxidase (POD)-like activity, oxidase (OD)-like activity, catalase (CAT)-like activity, glucose oxidase (GOD)-like activity, and glutathione peroxidase (GSH-Px)-like activity. All of the above enzyme activities give Ce SAs cascade self-circulation properties and can be used for tumor therapy in the TME. In addition, the prepared Ce SAs also have photothermal properties, which can achieve photothermal therapy (PTT) of tumor cells under 808 nm near-infrared (NIR) irradiation. Combining the cascade self-cycling enzyme-like activities and the photothermal properties of Ce SAs, this synergistic therapy makes Ce SAs have attractive efficacy in tumor treatment.

Mechanisms and Applications of Manganese-Based Nanomaterials in Tumor Diagnosis and Therapy

Tumors are the second most common cause of mortality globally, ranking just below heart disease. With continuous advances in diagnostic technology and treatment approaches, the survival rates of some cancers have increased. Nevertheless, due to the complexity of the mechanisms underlying tumors, cancer remains a serious public health issue that threatens the health of the population globally. Manganese (Mn) is an essential trace element for the human body. Its regulatory role in tumor biology has received much attention in recent years. Developments in nanotechnology have led to the emergence of Mn-based nanoparticles that have great potential for use in the diagnosis and treatment of cancers. Mn-based nanomaterials can be integrated with conventional techniques, including chemotherapy, radiation therapy, and gene therapy, to augment their therapeutic effectiveness. Further, Mn-based nanomaterials can play a synergistic role in emerging treatment strategies for tumors, such as immunotherapy, photothermal and photodynamic therapy, electromagnetic hyperthermia, sonodynamic therapy, chemodynamic therapy, and intervention therapy. Moreover, Mn-based nanomaterials can enhance both the precision of tumor diagnostics and the capability for combined diagnosis and treatment. This article examines the roles and associated mechanisms of Mn in the field of physiology and tumor biology, with a focus on the application prospects of Mn-based nanomaterials in tumor diagnosis and treatment.

A Synergistic Dual-Atom Sites Nanozyme Augments Immunogenic Cell Death for Efficient Immunotherapy

Inducing immunogenic cell death (ICD) is a promising approach to elicit enduring antitumor immune responses. Hence, extensive efforts are being made to develop ICD inducers. Herein, a cascaded dual-atom nanozyme with Fe and Cu sites (FeCu-DA) as an efficient ICD inducer is presented. The Fe and Cu dual-atom sites synergistically enhance peroxidase (POD) and catalase activities, effectively converting intratumoral hydrogen peroxide (H2O2) to hydroxyl radicals (·OH) and oxygen (O2). Moreover, FeCu-DA exhibits superior glutathione-oxidase (GSH-OXD) activity, catalyzing GSH oxidation to generate H2O2, enabling cascaded catalysis for sustainable ∙OH generation and reducing reactive oxygen species (ROS) resistance by consuming GSH. Steady-state kinetic analysis and density functional theory calculations indicate that FeCu-DA exhibits a higher catalytic rate and efficiency than Fe single-atom nanozymes (Fe-SA) because of its stronger interactions with H2O2. Its POD activity is 948.05 U mg-1, which is 2.8-fold greater than that of Fe-SA. Furthermore, FeCu-DA exhibits impressive photothermal effects and photothermal-enhanced cascaded catalysis kinetics for ROS generation, thereby inducing potent ICD. Combined with anti-PD-L1 antibody (αPD-L1) blockade, FeCu-DA shows synergistic enhancement in treatment under near-infrared irradiation. This study provides insights for designing efficient dual-atom nanozymes and demonstrates their potential in ICD-induced cancer immunotherapy.

MnGA with multiple enzyme-like properties for acute wound healing by reducing oxidative stress and modulating signaling pathways

Nanozymes with specific catalytic activity inhibit inflammation and promote wound healing efficiently and safely. In this work, multifunctional manganese-based nanozymes (MnGA) with antioxidant properties were successfully constructed via a simple coordination reaction in which manganese chloride was used as the manganese source and gallic acid (GA) was used as the ligand solution. MnGA possesses both catalase-like (CAT-like) and superoxide dismutase-like (SOD-like) activities and a reactive nitrogen species (RNS) scavenging capacity, which enables it to efficiently inhibit the inflammatory response. Specifically, MnGA scavenges superoxide anions and produces H2O2 via SOD-like activity and then consumes H2O2 to convert it to nontoxic H2O and O2 via CAT-like activity, resulting in a cascade of catalytic reactions to scavenge reactive oxygen species (ROS). Moreover, the scavenging of RNS by MnGA can amplify the anti-inflammatory effect in combination with the scavenging of ROS. RNA sequencing of mouse skin tissue further revealed that MnGA significantly reduces inflammation by modulating the nuclear factor kappa-B (NF-κB), Toll-like receptor (TLR), and NOD-like receptor (NLR) signaling pathways and promotes skin regeneration. In summary, MnGA nanocatalysts possess excellent antioxidative and anti-inflammatory properties, highlighting their potential applications in wound healing and inflammation treatment.

A Cardiac-Targeting and Anchoring Bimetallic Cluster Nanozyme Alleviates Chemotherapy-Induced Cardiac Ferroptosis and PANoptosis

Doxorubicin (DOX), a potent antineoplastic agent, is commonly associated with cardiotoxicity, necessitating the development of strategies to reduce its adverse effects on cardiac function. Previous research has demonstrated a strong correlation between DOX-induced cardiotoxicity and the activation of oxidative stress pathways. This work introduces a novel antioxidant therapeutic approach, utilizing libraries of tannic acid and N-acetyl-L-cysteine-protected bimetallic cluster nanozymes. Through extensive screening for antioxidative enzyme-like activity, an optimal bimetallic nanozyme (AuRu) is identified that possess remarkable antioxidant characteristics, mimicking catalase-like enzymes. Theoretical calculations reveal the surface interactions of the prepared nanozymes that simulate the hydrogen peroxide decomposition process, showing that these bimetallic nanozymes readily undergo OH⁻ adsorption and O₂ desorption. To enhance cardiac targeting, the atrial natriuretic peptide is conjugated to the AuRu nanozyme. These cardiac-targeted bimetallic cluster nanozymes, with their anchoring capability, effectively reduce DOX-induced cardiomyocyte ferroptosis and PANoptosis without compromising tumor treatment efficacy. Thus, the therapeutic approach demonstrates significant reductions in chemotherapy-induced cardiac cell death and improvements in cardiac function, accompanied by exceptional in vivo biocompatibility and stability. This study presents a promising avenue for preventing chemotherapy-induced cardiotoxicity, offering potential clinical benefits for cancer patients.

Enzymes in Addressing Hypoxia for Biomaterials Engineering

Oxygen is essential for normal cellular functions. Hypoxia impacts various cellular processes, such as metabolism, growth, proliferation, angiogenesis, metastasis, tumorigenesis, microbial infection, and immune response, mediated by hypoxia-inducible factors (HIFs). Hypoxia contributes to the progression and development of cancer, cardiovascular diseases, metabolic disorders, kidney diseases, and infections. The potential alleviation of hypoxia has been explored through the enzymatic in situ decomposition of hydrogen peroxide, leading to the generation of oxygen. However, challenges such as limited stability restrict the effectiveness of enzymes such as catalase in biomedical and in vivo applications. To overcome these limitations, targeted delivery of the enzymes has been proposed. This review offers a critical comparison of i) current approaches to enhance the in vivo stability of catalase; and ii) the structure, mechanism of action, and kinetics of catalase and catalase-like nanozymes.

Triggering immunogenic death of cancer cells by nanoparticles overcomes immunotherapy resistance

Immunotherapy resistance poses a significant challenge in oncology, necessitating novel strategies to enhance the therapeutic efficacy. Immunogenic cell death (ICD), including necroptosis, pyroptosis and ferroptosis, triggers the release of tumor-associated antigens and numerous bioactive molecules. This release can potentiate a host immune response, thereby overcoming resistance to immunotherapy. Nanoparticles (NPs) with their biocompatible and immunomodulatory properties, are emerging as promising vehicles for the delivery of ICD-inducing agents and immune-stimulatory adjuvants to enhance immune cells tumoral infiltration and augment immunotherapy efficacy. This review explores the mechanisms underlying immunotherapy resistance, and offers an in-depth examination of ICD, including its principles and diverse modalities of cell death that contribute to it. We also provide a thorough overview of how NPs are being utilized to trigger ICD and bolster antitumor immunity. Lastly, we highlight the potential of NPs in combination with immunotherapy to revolutionize cancer treatment.

Polyvalent Aptamer Nanodrug Conjugates Enable Efficient Tumor Cuproptosis Therapy Through Copper Overload and Glutathione Depletion

Cuproptosis, a recently identified form of copper-dependent cell death, shows promising tumor suppressive effects with minimal drug resistance. However, its therapeutic efficacy is hampered by its dependence on copper ions and the glutathione (GSH)-rich microenvironment in tumors. Here, we have developed polyvalent aptamer nanodrug conjugates (termed CuPEs@PApt) with a nucleosome-like structure to improve tumor cuproptosis therapy by exploiting mitochondrial copper overload and GSH depletion. Polyvalent aptamer (PApt), comprising polyvalent epithelial cell adhesion molecule aptamers for tumor targeting and repetitive PolyT sequences for copper chelation, facilitates efficient loading and targeted delivery of copper peroxide-Elesclomol nanodots (CuPEs). Upon internalization by tumor cells, Elesclomol released from CuPEs@PApt accumulates copper ions in mitochondria to initiate cuproptosis, while lysosomal degradation of CuP nanodots generates exogenous Cu2+ and H2O2, triggering a Fenton-like reaction for GSH depletion to enhance cuproptosis. In vitro and in vivo experiments confirm the efficacy of this strategy in inducing tumor cell cuproptosis and immunogenic cell death, the latter contributing to the activation of the antitumor immune response for synergistic tumor growth inhibition.

Multienzyme-Like Polyoxometalate-Based Single-Atom Enzymes for Cancer-Specific Therapy Through Acid-Triggered Nontoxicity-to-Toxicity Transition

Single-atom enzymes (SAzymes) exhibit great potential for chemodynamic therapy (CDT); while, general application is still challenged by their instability and unavoidable side effects during delivery. Herein, a manganese-based polyoxometalate single-atom enzyme (Mn-POM SAE) is first introduced into tumor-specific CDT, which exhibits tumor microenvironment (TME)-activated transition of nontoxicity-to-toxicity. Different from traditional POM materials, the aggregates of low-toxic Mn-POM SAE nanospheres are obtained at neutral conditions, facilitating efficient delivery and avoiding toxicity problems in normal tissues. Under acid TME conditions, these nanospheres are degraded into smaller units of toxic Mn(II)-PW11; thus, initiating cancer cell-specific therapy. The released active units of Mn(II)-PW11 exhibit excellent multienzyme-like activities (including peroxidase (POD)-like, oxidase (OXD)-like, catalase (CAT)-like, and glutathione peroxidase (Gpx)-like activities) for the synergistic cancer therapy due to the stabilized high valence Mn species (MnIII/MnIV). As demonstrated by both intracellular evaluations and in vivo experiments, ROS is generated to cause damage to lysosome membranes, further facilitating acidification and impaired autophagy to enhance cancer therapy. This study provides a detailed investigation on the acid-triggered releasing of active units and the electron transfer in multienzyme-mimic-like therapy, further enlarging the application of POMs from catalytical engineering into cancer therapy.

Manganese-based nanomaterials promote synergistic photo-immunotherapy: green synthesis, underlying mechanisms, and multiple applications

Single phototherapy and immunotherapy have individually made great achievements in tumor treatment. However, monotherapy has difficulty in balancing accuracy and efficiency. Combining phototherapy with immunotherapy can realize the growth inhibition of distal metastatic tumors and enable the remote monitoring of tumor treatment. The development of nanomaterials with photo-responsiveness and anti-tumor immunity activation ability is crucial for achieving photo-immunotherapy. As immune adjuvants, photosensitizers and photothermal agents, manganese-based nanoparticles (Mn-based NPs) have become a research hotspot owing to their multiple ways of anti-tumor immunity regulation, photothermal conversion and multimodal imaging. However, systematic studies on the synergistic photo-immunotherapy applications of Mn-based NPs are still limited; especially, the green synthesis and mechanism of Mn-based NPs applied in immunotherapy are rarely comprehensively discussed. In this review, the synthesis strategies and function of Mn-based NPs in immunotherapy are first introduced. Next, the different mechanisms and leading applications of Mn-based NPs in immunotherapy are reviewed. In addition, the advantages of Mn-based NPs in synergistic photo-immunotherapy are highlighted. Finally, the challenges and research focus of Mn-based NPs in combination therapy are discussed, which might provide guidance for future personalized cancer therapy.