Nanoclustered Cascaded Enzymes for Targeted Tumor Starvation and Deoxygenation-Activated Chemotherapy without Systemic Toxicity

Catalytic Nanoparticles in Biomedical Applications: Exploiting Advanced Nanozymes for Therapeutics and Diagnostics

Catalytic nanoparticles (CNPs) as heterogeneous catalyst reveals superior activity due to their physio-chemical features, such as high surface-to-volume ratio and unique optical, electric, and magnetic properties. The CNPs, based on their physio-chemical nature, can either increase the reactive oxygen species (ROS) level for tumor and antibacterial therapy or eliminate the ROS for cytoprotection, anti-inflammation, and anti-aging. In addition, the catalytic activity of nanozymes can specifically trigger a specific reaction accompanied by the optical feature change, presenting the feasibility of biosensor and bioimaging applications. Undoubtedly, CNPs play a pivotal role in pushing the evolution of technologies in medical and clinical fields, and advanced strategies and nanomaterials rely on the input of chemical experts to develop. Herein, a systematic and comprehensive review of the challenges and recent development of CNPs for biomedical applications is presented from the viewpoint of advanced nanomaterial with unique catalytic activity and additional functions. Furthermore, the biosafety issue of applying biodegradable and non-biodegradable nanozymes and future perspectives are critically discussed to guide a promising direction in developing span-new nanozymes and more intelligent strategies for overcoming the current clinical limitations.

Opportunities for nanomaterials in enzyme therapy

In recent years, enzyme therapy strategies have rapidly evolved to catalyze essential biochemical reactions with therapeutic potential. These approaches hold particular promise in addressing rare genetic disorders, cancer treatment, neurodegenerative conditions, wound healing, inflammation management, and infectious disease control, among others. There are several primary reasons for the utilization of enzymes as therapeutics: their substrate specificity, their biological compatibility, and their ability to generate a high number of product molecules per enzyme unit. These features have encouraged their application in enzyme replacement therapy where the enzyme serves as the therapeutic agent to rectify abnormal metabolic and physiological processes, enzyme prodrug therapy where the enzyme initiates a clinical effect by activating prodrugs, and enzyme dynamic or starving therapy where the enzyme acts upon host substrate molecules. Currently, there are >20 commercialized products based on therapeutic enzymes, but approval rates are considerably lower than other biologicals. This has stimulated nanobiotechnology in the last years to develop nanoparticle-based solutions that integrate therapeutic enzymes. This approach aims to enhance stability, prevent rapid clearance, reduce immunogenicity, and even enable spatio-temporal activation of the therapeutic catalyst. This comprehensive review delves into emerging trends in the application of therapeutic enzymes, with a particular emphasis on the synergistic opportunities presented by incorporating enzymes into nanomaterials. Such integration holds the promise of enhancing existing therapies or even paving the way for innovative nanotherapeutic approaches.

Microfluidic-Enabled Assembly of Multicomponent Artificial Organelle for Synergistic Tumor Starvation Therapy

Artificial organelles (AOs) encapsulating enzymes are engineered to facilitate biocatalytic reactions for exerting therapeutic effects in various diseases. Exploiting the confinement effect, these catalytic properties exhibit significant enhancements without being influenced by the surrounding medium, enabling more efficient cascade reactions. In this study, we present a novel approach for synergistic tumor starvation therapy by developing multicomponent artificial organelles that combine enzymatic oncotherapy with chemotherapy. The construction process involves a microfluidic-based approach that enables the encapsulation of cationic cores containing doxorubicin (DOX), electrostatic adsorption of cascade enzymes, and surface assembly of the protective lipid membrane. Additionally, these multicomponent AOs possess multicompartment structures that enable the separation and sequential release of each component. By coencapsulating enzymes and chemotherapeutic agent DOX within AOs, we achieve enhanced enzymatic cascade reactions (ECR) and improved intrinsic permeability of DOX due to spatial confinement. Furthermore, exceptional therapeutic effects on 4T1 xenograft tumors are observed, demonstrating the feasibility of utilizing AOs as biomimetic implants in living organisms. This innovative approach that combines starvation therapy with chemotherapy using multicompartment AOs represents a promising paradigm in the field of precise cancer therapy.

Increasing Multienzyme Cascade Efficiency and Stability of MOF via Partitioning Immobilization

Enhancing the stability of multienzyme cascade reactions in metal-organic frameworks (MOFs) is a challenging task in the fields of biotechnology and chemistry. However, addressing this challenge could yield far-reaching benefits across the application range in the biomedical, food, and environmental sectors. In this study, multienzyme partitioning immobilization that sequentially immobilizes cascade enzymes with hierarchical MOFs is proposed to reduce substrate diffusion resistance. Conversion results of ginsenosides indicate that this strategy improves the cascade efficiency up to 1.26 times. The substrate diffusion model is used to investigate the dual-interenzyme mass transfer behavior of substrates in the restricted domain space and evaluate the substrate channeling effect under partitioning immobilization. Molecular docking and kinetic simulations reveal that the MOFs effectively limit the conformational changes of cascade enzymes at high temperatures and in organic solvents while maintaining a large pocket of active centers. This phenomenon increased efficient substrate docking to the enzyme molecules, further optimizing cascade efficiency. The results of the immobilization of GOX and horseradish peroxidase as model enzymes indicate that the partitioned MOF immobilization strategy could be used for universal adaptation of cascade enzymes.

Immobilized Multi-Enzyme/Nanozyme Biomimetic Cascade Catalysis for Biosensing Applications

Multiple enzyme-induced cascade catalysis has an indispensable role in the process of complex life activities, and is widely used to construct robust biosensors for analyzing various targets. The immobilized multi-enzyme cascade catalysis system is a novel biomimetic catalysis strategy that immobilizes various enzymes with different functions in stable carriers to simulate the synergistic catalysis of multiple enzymes in biological systems, which enables high stability of enzymes and efficiency enzymatic cascade catalysis. Nanozymes, a type of nanomaterial with intrinsic enzyme-like characteristics and excellent stabilities, are also widely applied instead of enzymes to construct immobilized cascade systems, achieving better catalytic performance and reaction stability. Due to good stability, reusability, and remarkably high efficiency, the immobilized multi-enzyme/nanozyme biomimetic cascade catalysis systems show distinct advantages in promoting signal transduction and amplification, thereby attracting vast research interest in biosensing applications. This review focuses on the research progress of the immobilized multi-enzyme/nanozyme biomimetic cascade catalysis systems in recent years. The construction approaches, factors affecting the efficiency, and applications for sensitive biosensing are discussed in detail. Further, their challenges and outlooks for future study are also provided.

Dual Enzyme-Encapsulated Materials for Biological Cascade Chemistry and Synergistic Tumor Starvation

Framework and polymeric nanoreactors (NRs) have distinct advantages in improving chemical reaction efficiency in the tumor microenvironment (TME). Nanoreactor-loaded oxidoreductase enzyme is activated by tumor acidity to produce H2O2 by increasing tumor oxidative stress. High levels of H2O2 induce self-destruction of the vesicles by releasing quinone methide to deplete glutathione and suppress the antioxidant potential of cancer cells. Therefore, the synergistic effect of the enzyme-loaded nanoreactors results in efficient tumor ablation via suppressing cancer-cell metabolism. The main driving force would be to take advantage of the distinct metabolic properties of cancer cells along with the high peroxidase-like activity of metalloenzyme/metalloprotein. A cascade strategy of dual enzymes such as glucose oxidase (GOx) and nitroreductase (NTR) wherein the former acts as an O2-consuming agent such as overexpression of NTR and further amplified NTR-catalyzed release for antitumor therapy. The design of cascade bioreductive hypoxia-responsive drug delivery via GOx regulates NTR upregulation and NTR-responsive nanoparticles. Herein, we discuss tumor hypoxia, reactive oxygen species (ROS) formation, and the effectiveness of these therapies. Nanoclusters in cascaded enzymes along with chemo-radiotherapy with synergistic therapy are illustrated. Finally, we outline the role of the nanoreactor strategy of cascading enzymes along with self-synergistic tumor therapy.

Targeted protein delivery based on stimuli-triggered nanomedicine

Protein-based drugs have shown unique advantages to treat various diseases in recent years. However, most protein therapeutics in clinical use are limited to extracellular targets with low delivery efficiency. To realize targeted protein delivery, a series of stimuli-triggered nanoparticle formulations have been developed to improve delivery efficiency and reduce off-target release. These smart nanoparticles are designed to release cargo proteins in response to either internal or external stimuli at pathological tissues. In this way, varieties of protein-based drugs including antibodies, enzymes, and pro-apoptotic proteins can be effectively delivered to desired sites for the treatment of cancer, inflammation, metabolic diseases, and so on with minimal side effects. In this review, recent advances in the design of stimuli-triggered nanomedicine for targeted protein delivery in different biomedical applications will be discussed. A deeper understanding of these emerging strategies helps develop more efficient protein delivery systems for clinical use in the future.

ATP Inhibition for Starvation/Mild Photothermal/Photodynamic Synergy Therapy Using Polypeptide Nanoparticles Conjugating 2-Deoxy-D-Glucose and Dye under NIR Phototheranostic Strategy

Rapid propagation of tumor cells requires plenty of energy, which is adenosine triphosphate (ATP) dependent. ATP inhibition in tumors not only results in the starvation of tumor cells but also down-regulation of the level of heat shock proteins (HSPs), which usually increase during traditional photothermal therapy (PTT), especially when the temperature is up 50 °C. 2-deoxy-D-glucose (2DG) is an anti-glycolytic reagent and can be used as an efficient agent for ATP inhibition in tumors. Compared with typical PTT, low-temperature mild photothermal therapy (MPTT) is receiving more and more attention because it avoids the high temperatures causing damage to the normal tissue, and the increase of HSPs which decrease PTT. Here, multifunctional polypeptide nanoparticles pDG@Ahx conjugating both a NIR probe Ahx-BDP and 2DG into the side chain of the amphiphilic polypeptide have been prepared. In vitro and in vivo studies reveal that the as-prepared nanoparticles achieve a synergistic effect of starvation/MPTT/PDT (photodynamic therapy), and it provides a new strategy to NIR-I/II fluorescence imaging-guided starvation/MPTT/PDT synergy therapy for tumors.

Application and progress of nanozymes in antitumor therapy

Tumors remain one of the major threats to public health and there is an urgent need to design new pharmaceutical agents for their diagnosis and treatment. In recent years, due to the rapid development of nanotechnology, biotechnology, catalytic science, and theoretical computing, subtlety has gradually made great progress in research related to tumor diagnosis and treatment. Compared to conventional drugs, enzymes can improve drug distribution and enhance drug enrichment at the tumor site, thereby reducing drug side effects and enhancing drug efficacy. Nanozymes can also be used as tumor tracking imaging agents to reshape the tumor microenvironment, providing a versatile platform for the diagnosis and treatment of malignancies. In this paper, we review the current status of research on enzymes in oncology and analyze novel oncology therapeutic approaches and related mechanisms. To date, a large number of nanomaterials, such as noble metal nanomaterials, nonmetallic nanomaterials, and carbon-based nanomaterials, have been shown to be able to function like natural enzymes, particularly with significant advantages in tumor therapy. In light of this, the authors in this review have systematically summarized and evaluated the construction, enzymatic activity, and their characteristics of nanozymes with respect to current modalities of tumor treatment. In addition, the application and research progress of different types of nicknames and their features in recent years are summarized in detail. We conclude with a summary and outlook on the study of nanozymes in tumor diagnosis and treatment. It is hoped that this review will inspire researchers in the fields of nanotechnology, chemistry, biology, materials science and theoretical computing, and contribute to the development of nano-enzymology.

Intelligent Delivery Systems in Tumor Metabolism Regulation: Exploring the Path Ahead

Cancer metabolism plays multifaceted roles in the initiation and progression of tumors, and interventions in metabolism are considered fundamental approaches for cancer control. Within the vast metabolic networks of tumors, there exist numerous potential therapeutic targets, intricately interconnected with each other and with signaling networks related to immunity, metastasis, drug resistance, and more. Based on the characteristics of the tumor microenvironment, constructing drug delivery systems for multi-level modulation of the tumor microenvironment is proven as an effective strategy for achieving multidimensional control of cancer. Consequently, this article summarizes several features of tumor metabolism to provide insights into recent advancements in intelligent drug delivery systems for achieving multi-level regulation of the metabolic microenvironment in cancer, with the aim of offering a novel paradigm for cancer treatment.

Immobilization of horseradish peroxidase on metal-organic framework to imporve enzyme activity for enhanced chemodynamic therapy

Bio-enzymes have the advantages of strong substrate specificity, high catalytic efficiency, and minimal toxic side effects, making them promising drugs in cancer therapy. However, the poor stability and cellular penetrability of uncoated protein in the physiological environment severely restricts the direct application of Bio-enzyme. To address it, we report a metal-organic framework (MOF), Hf-DBA (H2DBA, biphenyl carboxylic acid ligands). The morphology of the Hf-DBA was revealed by TEM and the diameter was in the range of 200 to 350 nm. Hf-DBA acted a carrier for intracellular delivery and protection of horseradish peroxidase (HRP). The prepared HRP@Hf-DBA can catalyze the excess H2O2 in the tumor cells to generation of •OH for chemodynamic therapy (CDT). Compared with free HRP, the catalytic activity of HRP@Hf-DBA is significantly improved, and the optimal catalytic conditions are explored. The catalytic stability of HRP@Hf-DBA remained above 70% after 12 cycles of catalysis. After treatment with HRP@Hf-DBA, the apoptosis rates of A549 and Hela cells was 71.64%, and 76.86%. The results in vitro show that HRP@Hf-DBA can effectively inhibit the growth of tumor cells through enhanced CDT.

Amino Acid-Starved Cancer Cells Utilize Macropinocytosis and Ubiquitin-Proteasome System for Nutrient Acquisition

To grow in nutrient-deprived tumor microenvironment, cancer cells often internalize and degrade extracellular proteins to refuel intracellular amino acids. However, the nutrient acquisition routes reported by previous studies are mainly restricted in autophagy-lysosomal pathway. It remains largely unknown if other protein degradation systems also contribute to the utilization of extracellular nutrients. Herein, it is demonstrated that under amino acid starvation, extracellular protein internalization through macropinocytosis and protein degradation through ubiquitin-proteasome system are activated as a nutrient supply route, sensitizing cancer cells to proteasome inhibition. By inhibiting both macropinocytosis and ubiquitin-proteasome system, an innovative approach to intensify amino acid starvation for cancer therapy is presented. To maximize therapeutic efficacy and minimize systemic side effects, a pH-responsive polymersome nanocarrier is developed to deliver therapeutic agents specifically to tumor tissues. This nanoparticle system provides an approach to exacerbate amino acid starvation for cancer therapy, which represents a promising strategy for cancer treatment.

Manganese Dioxide-Entrapping Dendrimers Co-Deliver Protein and Nucleotide for Magnetic Resonance Imaging-Guided Chemodynamic/Starvation/Immune Therapy of Tumors

Development of a nanoscale drug delivery system that can simultaneously exert efficient tumor therapeutic efficacy while creating the desired antitumor immune responses is still challenging. Herein, we report the use of a manganese dioxide (MnO2)-entrapping dendrimer nanocarrier to codeliver glucose oxidase (GOx) and cyclic GMP-AMP (cGAMP), an agonist of the stimulator of interferon genes (STING) for improved tumor chemodynamic/starvation/immune therapy. Methoxy poly(ethylene glycol) (mPEG)- and phenylboronic acid (PBA)-modified generation 5 (G5) poly(amidoamine) dendrimers were first synthesized and then entrapped with MnO2 nanoparticles (NPs) to generate the hybrid MnO2@G5-mPEG-PBA (MGPP) NPs. The created MGPP NPs with an MnO2 core size of 2.8 nm display efficient glutathione depletion ability, and a favorable Mn2+ release profile under a tumor microenvironment mimetic condition to enable Fenton-like reaction and T1-weighted magnetic resonance (MR) imaging. We show that the MGPP-mediated GOx delivery facilitates enhanced chemodynamic/starvation therapy of cancer cells in vitro, and further codelivery of cGAMP can effectively trigger immunogenic cell death (ICD) to strongly promote the maturation of dendritic cells. In a bilateral mouse colorectal tumor model, the dendrimer delivery nanosystem elicits a potent antitumor performance with a strong abscopal effect, greatly improving the overall mouse survival rate. Importantly, the dendrimer-mediated codelivery not only allows the coordination of Mn2+ with GOx and cGAMP for respective chemodynamic/starvation-triggered ICD and augmented STING activation to boost systemic antitumor immune responses, but also enables T1-weighted tumor MR imaging, potentially serving as a promising nanoplatform for enhanced antitumor therapy with desired immune responses.

Glucose-responsive enzymatic biomimetic nanodots for H2O2 self-supplied catalytic photothermal/chemodynamic anticancer therapy

Photothermal therapy (PTT) combined with chemodynamic therapy (CDT) presents an appealing complementary anti-tumor strategy, wherein PTT accelerates the production of reactive oxygen species (ROS) in CDT and CDT eliminates residual tumor tissues that survive from PTT treatment. However, nanomaterials utilized in PTT/CDT are limited by non-specific damage to the entire organism. Herein, a glucose-responsive enzymatic Fe@HRP-ABTS/GOx nanodot is judiciously designed for tumor-specific PTT/CDT via a simple and clean protein-templated biomimetic mineralization synthesis. By oxidizing glucose in tumor cells, glucose oxidase (GOx) activates glucose-responsive tumor therapy and increases the concentration of H2O2 at the tumor site. More importantly, the self-supplied peroxide hydrogen (H2O2) can convert ABTS (2,2'-Hydrazine-bis(3-ethylbenzothiazoline-6-sulfonic acid) diamine salt) into oxidized ABTS (oxABTS) through horseradish peroxidase (HRP) catalysis for PTT and photoacoustic (PA) imaging. Furthermore, the Fe2+ arising from the reduction of Fe3+ by overexpressed GSH reacts with H2O2 to generate intensely reactive •OH through the Fenton reaction, concurrently depleting GSH and inducing efficient tumor CDT. The in vitro and in vivo experiments demonstrate superior cancer cell killing and tumor eradication effect of Fe@HRP-ABTS/GOx nanodot under near-infrared (NIR) laser irradiation. Collectively, the nanodots provide mutually reinforcing catalytic PTT/CDT anti-tumor strategies for treating liver cancer and potentially other malignancies. STATEMENT OF SIGNIFICANCE: Combinatorial antitumor therapy with nanomedicines presents great prospects for development. However, the limitation of non-specific damage to normal tissues hinders its further clinical application. In this work, we fabricated tumor-selective biomimetic Fe@HRP-ABTS/GOx nanodots for H2O2 self-supplied catalytic photothermal/chemodynamic therapy of tumors. The biomimetic synthesis strategy provides the nanodots with enzymatic activity in response to glucose to produce H2O2. The self-supplied H2O2 initiates photothermal therapy with oxidized ABTS and enhances chemodynamic therapy through simultaneous •OH generation and GSH depletion. Our work provides a new paradigm for developing tumor-selective catalytic nanomedicines and will guide further clinical translation of the enzymatic biomimetic synthesis strategy.

Biomimetic Nano-Immunoactivator via Ionic Metabolic Modulation for Strengthened NIR-II Photothermal Immunotherapy

Reprogramming the immunologically "cold" environment of solid tumors is currently becoming the mainstream strategy to elicit powerful and systemic anticancer immunity. Here, a facile and biomimetic nano-immunnoactivator (CuS/Z@M4T1 ) is detailed by engineering a Zn2+ -bonded zeolitic imidazolate framework-8 (ZIF-8) with CuS nanodots (NDs) and cancer cell membrane for amplified near-infrared-II (NIR-II) photothermal immunotherapy via Zn2+ metabolic modulation. Taking advantage of the NIR-II photothermal effect of CuS NDs and the acidic responsiveness of ZIF-8, CuS/Z@M4T1 rapidly causes intracellular Zn2+ pool overload and disturbs the metabolic flux of 4T1 cells, which effectively hamper the production of heat shock proteins and relieve the resistance of photothermal therapy (PTT). Thus, amplified immunogenic cell death is evoked and initiates the immune cascade both in vivo and in vitro as demonstrated by dendritic cells maturation and T-cell infiltration. Further combination with antiprogrammed death 1 (aPD-1) achieves escalated antitumor efficacy which eliminates the primary, distant tumor and avidly inhibits lung metastasis due to cooperation of enhanced photothermal stimulation and empowerment of cytotoxic T lymphocytes by aPD-1. Collectively, this work provides the first report of using the intrinsic modulation property of meta-organometallic ZIF-8 for enhanced cancer photoimmunotherapy together with aPD-1, thereby inspiring a novel combined paradigm of ion-rich nanomaterials for cancer treatment.

Polydopamine-cloaked Fe-based metal organic frameworks enable synergistic multidimensional treatment of osteosarcoma

One of the major challenges in effective cancer therapy arises because of the hypoxic microenvironment in the tumor. This compromises the efficacy of both chemo- and radiotherapy, and thus hinders patient outcomes. To solve this problem, we constructed polydopamine (PDA)-cloaked Fe-based metal organic frameworks (MOFs) loaded with d-arginine (d-Arg), glucose oxidase (GOX), and the chemotherapeutic drug tirapazamine (TPZ). These offer simultaneous multifaceted therapy combining chemodynamic therapy (CDT)/radiotherapy (RT)/starvation therapy (ST)/gas therapy (GT) and chemotherapy. The particles further can act as contrast agents in magnetic resonance imaging. GOX catalyses the conversion of endogenous glucose and O2 to hydrogen peroxide and gluconic acid, blocking the cells' energy supply and providing ST. With the resultant acidification of the local environment, the breakdown of the MOF releases TPZ (for chemotherapy) and Fe3+, which reacts with H2O2 to produce reactive oxygen species and thus stimulates the conversion of d-Arg to NO for GT and RT sensitization. The PDA coating not only seals the pores and chelates Fe3+ to enhance the T1-weighted magnetic resonance imaging (MRI) properties, but also is used to graft folate bovine serum albumin (FA-BSA) and thereby target the tumor site. The combined administration of low doses of X-ray irradiation and nanoparticles reduces the side effects on healthy tissue and can prevent lung metastases in mice. This work highlights the synergistic treatment of osteosarcoma via ST/GT/CDT/RT/MRI/ chemotherapy using a PDA-cloaked MOF system.

Protein-based Nanoparticles: From Drug Delivery to Imaging, Nanocatalysis and Protein Therapy

Proteins and enzymes are versatile biomaterials for a wide range of medical applications due to their high specificity for receptors and substrates, high degradability, low toxicity, and overall good biocompatibility. Protein nanoparticles are formed by the arrangement of several native or modified proteins into nanometer-sized assemblies. In this review, we will focus on artificial nanoparticle systems, where proteins are the main structural element and not just an encapsulated payload. While under natural conditions, only certain proteins form defined aggregates and nanoparticles, chemical modifications or a change in the physical environment can further extend the pool of available building blocks. This allows the assembly of many globular proteins and even enzymes. These advances in preparation methods led to the emergence of new generations of nanosystems that extend beyond transport vehicles to diverse applications, from multifunctional drug delivery to imaging, nanocatalysis and protein 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.

Peptide-Appended Nanosonosensitizers Targeting Tumor Glycolysis for Synergistic Sonodynamic-Immunometabolic Therapy of Spinal-Metastasized Tumors

Despite recent advancements in cancer immunotherapy, challenges have yet to be surmounted to achieve two major goals of magnifying antitumor immunity and remodeling the immunosuppressive tumor microenvironment. Here, a nanosystem (ODM-R) that integrates oxygen-deficient molybdenum oxide (ODM) nanosonosensitizers and R7 peptides with tumor metabolism regulation effects is designed and fabricated for synergistic sonodynamic-immunometabolic therapy of spinal-metastasized tumors. The ODM generates reactive oxygen species upon ultrasound irradiation to implement sonodynamic therapy (SDT), inducing cancer cell apoptosis and immunogenic cell death. The R7 attached on ODM markedly inhibits the uptake of glucose and excretion of lactic acid in cancer cells by perturbing the glycolysis process. The combination of SDT and tumor glycolysis obstruction by ODM-R guarantees satisfactory efficacy in synergizing with PD-L1 antibody to eradicate spinal-metastasized tumors, achieving concurrent sonodynamic-triggered immune activation and immunosuppressive tumor microenvironment remodeling. This work provides a proof-of-concept of nanosonosensitizers for boosting cancer immunotherapy by SDT and tumor metabolic regulation.

Compartmentalized Nano-MOFs as Co-delivery Systems for Enhanced Antitumor Therapy

Therapeutic bioactive macromolecules hold great promise in cancer therapy, but challenges such as low encapsulation efficiency and susceptibility to inactivation during the targeted co-delivery hinder their widespread applications. Compartmentalized nano-metal-organic frameworks (nMOFs) can easily load macromolecules in the innermost layer, protect them from the outside environment, and selectively release them in the target location after stimulation, showing great potential in the co-delivery of biomacromolecules. Herein, the rationally designed (GOx + CAT)/ZIF-8@BSATPZ/ZIF-8 (named GCZ@BTZ) nMOFs with compartmentalized structures are employed to deliver cascaded enzymes and the chemotherapeutic drug tirapazamine (TPZ)-conjugated bovine serum albumin (BSATPZ). Benefiting from the compartmentalized structure and protective shell, the GCZ@BTZ system is stable during blood circulation and preferentially accumulates in the tumor. Furthermore, in response to the acidic tumor environment, GCZ@BTZ effectively released the loading enzymes and BSATPZ. Along with the tumor starvation caused by depletion of glucose, cascaded reactions could also contribute to the enhancement of tumor hypoxia, which further activated BSATPZ-based chemotherapy. Notably, in the mouse tumor models, GCZ@BTZ treatment significantly inhibits tumor survival and metastasis. Such a compartmentalized nMOF delivery system presents a promising avenue for the efficient delivery of bioactive macromolecules.

Recent Advances in Nanoplatform Construction Strategy for Alleviating Tumor Hypoxia

Hypoxia is a typical feature of most solid tumors and has important effects on tumor cells' proliferation, invasion, and metastasis. This is the key factor that leads to poor efficacy of different kinds of therapy including chemotherapy, radiotherapy, photodynamic therapy, etc. In recent years, the construction of hypoxia-relieving functional nanoplatforms through nanotechnology has become a new strategy to reverse the current situation of tumor microenvironment hypoxia and improve the effectiveness of tumor treatment. Here, the main strategies and recent progress in constructing nanoplatforms are focused on to directly carry oxygen, generate oxygen in situ, inhibit mitochondrial respiration, and enhance blood perfusion to alleviate tumor hypoxia. The advantages and disadvantages of these nanoplatforms are compared. Meanwhile, nanoplatforms based on organic and inorganic substances are also summarized and classified. Through the comprehensive overview, it is hoped that the summary of these nanoplatforms for alleviating hypoxia could provide new enlightenment and prospects for the construction of nanomaterials in this field.

Multistage-Responsive Dual-Enzyme Nanocascades for Synergistic Radiosensitization-Starvation Cancer Therapy

Radiotherapy is a common cancer treatment approach in clinical practice, yet its efficacy has been restricted by tumor hypoxia. Nanomaterials-mediated systemic delivery of glucose oxidase (GOx) and catalase (CAT) or CAT-like nanoenzymes holds the potential to enhance tumor oxygenation. However, they face the challenge of intermediate (hydrogen peroxide [H2 O2 ]) escape during systemic circulation if the enzyme pair is not closely placed to largely decompose H2 O2 , leading to oxidative stress on normal tissues. In the present study, a oxygen-generating nanocascade, n(GOx-CAT)C7A , constructed by strategically placing an enzymatic cascade (GOx and CAT) within a polymeric coating rich in hexamethyleneimine (C7A) moieties, is reported. During blood circulation, C7A remains predominantly non-protonated , achieving prolonged blood circulation due to its low-fouling surface. Once n(GOx-CAT)C7A reaches the tumor site, the acidic tumor microenvironment (TME) induces protonation of C7A moieties, resulting in a positively charged surface for enhanced tumor transcytosis. Moreover, GOx and CAT are covalently conjugated into close spatial proximity (<10 nm) for effective H2 O2  elimination. As demonstrated by the in vivo results, n(GOx-CAT)C7A achieves effective tumor retention and oxygenation, potent radiosensitization and antitumor effects. Such a dual-enzyme nanocascade for smart O2  delivery holds great potential for enhancing the hypoxia-compromised cancer therapies.

A Bioresponsive Diselenide-functionalized Hydrogel with Cascade Catalytic Activities for Enhanced Local Starvation- and Hypoxia-Activated Melanoma Therapy

Glutathione (GSH) consumption-enhanced cancer therapies represent important potential cancer treatment strategies. Herein, we developed a new multifunctional diselenide-crosslinked hydrogel with glutathione peroxidase (GPx)-like catalytic activity for GSH depletion-enhanced glucose oxidase (GOx)-mediated tumor starvation and hypoxia-activated chemotherapy. By increasing acid and H₂O₂ during GOx-induced tumor starvation, the degradation of the multiresponsive scaffold could be promoted, which led to accelerated release of the loaded drugs. Meanwhile, the overproduced H₂O₂ led to accelerated intracellular GSH consumption under the cascade catalysis of small molecular selenides released from the degraded hydrogel, further enhancing the curative effect of in situ H₂O₂ and subsequent multimodal cancer treatment. Following the GOx-induced amplification of hypoxia, tirapazamine (TPZ) was transformed into the highly toxic benzotriazinyl radical (BTZ·), exhibiting enhanced antitumor activity. This GSH depletion-augmented cancer treatment strategy effectively boosted GOx-mediated tumor starvation and activated the hypoxia drug, leading to significantly enhanced local anticancer efficacy. STATEMENT OF SIGNIFICANCE: There has been a growing interest in depleting intracellular GSH as a potential strategy for improving ROS-based cancer therapy. Herein, a bioresponsive diselenide-functionalized dextran-based hydrogel with GPx-like catalytic activity was developed for GSH consumption-enhanced local starvation- and hypoxia-activated melanoma therapy. Results showed that the overproduced H₂O₂ led to accelerated intracellular GSH consumption under the cascade catalysis of small molecular selenides released from the degraded hydrogel, further enhancing the curative effect of in situ H₂O₂ and subsequent multimodal cancer treatment.

Targeting tumor energy metabolism via simultaneous inhibition of mitochondrial respiration and glycolysis using biodegradable hydroxyapatite nanorods

Tumor cells obtain energy supply from the unique metabolic pathways of mitochondrial respiration and glycolysis, which can be used interchangeably to produce adenosine triphosphate (ATP) for survival. To simultaneously block the two metabolic pathways and sharply cut off ATP supply, a multifunctional "nanoenabled energy interrupter" (called as HNHA-GC) was prepared by attaching glucose oxidase (GOx), hyaluronic acid (HA), and 10-hydroxycamptothecin (CPT) on the surface of degradable hydroxyapatite (NHA) nanorods. After targeted delivery of HNHA-GC to the tumor site by HA, the tumor-selective acid degradation of HNHA-GC as well as the subsequent deliveries of Ca²⁺, drug CPT, and GOx take place. The released Ca²⁺ and CPT induce mitochondrial dysfunction by Ca²⁺ overload and chemotherapy respectively, while the GOx-triggered glucose oxidation inhibits glycolysis by starvation therapy (exogenous effect). The generated H₂O₂ and released CPT increase the intracellular reactive oxygen (ROS) level. Moreover, the generated H⁺ and enhanced ROS promote Ca²⁺ overload by accelerating the degradation of HNHA-GC and preventing intracellular Ca²⁺ efflux, respectively (endogenous effect). As a result, the HNHA-GC displays a promising therapeutic modality for simultaneously cutting off mitochondrial and glycolytic ATP production through a combination of Ca²⁺ overload, chemotherapy, and starvation therapy.

Prussian Blue-Derived Nanoplatform for In Situ Amplified Photothermal/Chemodynamic/Starvation Therapy

Chemodynamic therapy (CDT) is an emerging tumor treatment; however, it is hindered by insufficient endogenous hydrogen peroxide (H₂O₂) and high glutathione (GSH) concentrations in the tumor microenvironment (TME). Furthermore, CDT has limited therapeutic efficacy as a monotherapy. To overcome these limitations, in this study, a nanoplatform is designed and constructed from Cu-doped mesoporous Prussian blue (CMPB)-encapsulated glucose oxidase (GOx) with a coating of hyaluronic acid (HA) modified with a nitric oxide donor (HN). In the proposed GOx@CMPB-HN nanoparticles, the dopant Cu²⁺ ions are crucial to combining and mutually promoting multiple therapeutic approaches, namely, CDT, photothermal therapy (PTT), and starvation therapy. The dopant Cu²⁺ ions in CMPB protect against reactive oxygen species to deplete the intracellular GSH in the TME. Additionally, the byproduct Cu⁺ ions act as a substrate for a Fenton-like reaction that activates CDT. Moreover, H₂O₂, which is another important substrate, is produced in large quantities through intracellular glucose depletion caused by the nanoparticle-loaded GOx, and the gluconic acid produced in this reaction further enhances the TME acidity and creates a better catalytic environment for CDT. In addition, Cu²⁺ doping greatly improves the mesoporous Prussian blue (MPB) photothermal conversion performance, and the resultant increase in temperature accelerates CDT catalysis. Finally, the HN coating enables the nanoparticles to actively target CD44 receptors in cancer cells and also enhances vascular permeability. Therefore, this coating has multiple effects, such as facilitating enhanced permeability and retention and deep laser penetration. In vitro and in vivo experiments demonstrate that the proposed GOx@CMPB-HN nanoplatform significantly inhibits tumor growth with the help of in situ enhanced synergistic therapies based on the properties of the TME. The developed nanoplatform has the potential to be applied to cancer treatment and introduces new avenues for tumor treatment research.

Recent advances in sonodynamic immunotherapy

Tumor immunotherapy has become an important means of tumor therapy by enhancing the immune response and triggering the activation of immune cells. However, currently, only a small number of patients respond to immunotherapy alone, and patients may experience immune-related adverse events (irAEs) during the course of treatment. Sonodynamic therapy (SDT) can produce cytotoxic substances to tumor tissue, induce apoptosis and enhance immunity. SDT combined with immunotherapy is considered a promising strategy for cancer treatment. In this mini review, we summarize the role of SDT in immunotherapy in recent years, including the application of SDT-triggered immunotherapy and the combination of SDT and immunotherapy.

Acidity-responsive nanoplatforms aggravate tumor hypoxia via multiple pathways for amplified chemotherapy

Since the hypoxia tumor microenvironment (TME) will not only limit the treatment effect but also cause tumor recurrence and metastasis, intratumoral aggravated hypoxia level induced by vascular embolization is one of the major challenges in tumor therapy. The chemotherapeutic effect of hypoxia-activated prodrugs (HAPs) could be enhanced by the intensified hypoxia, the combination of tumor embolization and HAP-based chemotherapy exhibits a promising strategy for cancer therapy. Herein, an acidity-responsive nanoplatform (TACC NP) with multiple pathways to benefit the hypoxia-activated chemotherapy is constructed by loading the photosensitizer Chlorin e6 (Ce6), thrombin (Thr), and AQ4N within the calcium phosphate nanocarrier via a simple one-pot method. In the acidic TME, TACC NPs could be degraded to release Thr and Ce6, resulting in the destruction of tumor vessels and consumption of intratumoral oxygen under laser irradiation. Therefore, the intratumoral hypoxia level could be significantly aggravated, further leading to the enhanced chemotherapeutic effect of AQ4N. With the guidance of in vivo fluorescence imaging, the TACC NPs exhibited excellent tumor embolization/photodynamic/prodrug synergistic therapeutic effects with good biosafety.

Glucose oxidase-loaded colloidal stable WS2 nanobowls for combined starvation/photothermal therapy of colorectal tumors

Glucose is used as an important nutrient to support cell growth. The glucose oxidase (GOx) can transform glucose into gluconic acid and toxic H₂O₂, which can be used for tumor starvation therapy. However, the leakage of GOx may cause severe side effects to the normal tissue. To prevent the accidental leakage of GOx, this study proposes the chemical modification of GOx on the photothermal transducing agent surface, to realize the safe and combined starvation and photothermal therapy of colorectal tumors. Polyvinylpyrrolidone (PVP)-modified WS₂ nanobowls (WS₂-PVP) as a photothermal transducing agent were produced using a one-pot preparation method. Then, α-lipoic acid (LA) molecules were immobilized at the sulfur-deficient sites on the surface of WS₂ nanobowls to afford the chemical loading of GOx through amide bonds. Under the irradiation of a near-infrared laser (808 nm), thermal energy is generated by WS₂ to kill colorectal cancer cells locally. The photothermal conversion efficiency of WS₂-PVP-LA was 27.2%. This study is anticipated to open up an alternative avenue for the rational design of multifunctional nanotherapeutics for tumor therapy.

Starvation-assisted and photothermal-thriving combined chemo/chemodynamic cancer therapy with PT/MR bimodal imaging

Chemodynamic therapy (CDT) reflects a novel reactive oxygen species (ROS)-related cancer therapeutic approach. However, CDT monotherapy is often limited by weak efficacy and insufficient endogenous H₂O₂. Herein, a multifunctional combined bioreactor (MnFe-LDH/MTX@GOx@Ta, MMGT) relying on MnFe-layered double hydroxide (MnFe-LDH) loaded with methotrexate (MTX) and coated with glucose oxidase (GOx)/tannin acid (Ta) is established for applications in H₂O₂ self-supply and photothermal enhanced chemo/chemodynamic combined therapy along with photothermal (PT) /magnetic resonance (MR) dual-modality imaging ability for cancer treatment. Once internalized into tumor cells, MMGT achieves starvation therapy by catalyzing the oxidation of glucose with GOx, accompanied by the regeneration of H₂O₂, enabling a Fenton-like reaction to accomplish GOx catalytic amplified CDT. Moreover, MMGT manifests significant tumor-killing ability through improved CDT performance with outstanding photothermal conversion efficiency (η = 52.2%) under 808 nm laser irradiation. In addition, the release of Mn²⁺ from MnFe-LDH in a solid tumor can significantly enhance T₁-contrast MR imaging signals. Combined with MnFe-LDH-induced PT imaging under 808 nm laser irradiation, a dual-modality imaging directed theranostic nanoplatform has been developed. The present study provides a new strategy to design H₂O₂ self-supply and ROS evolving NIR light-absorption theranostic nanoagent for highly efficient and combined chemo/chemodynamic cancer treatment.

Nanotechnological strategies to increase the oxygen content of the tumor

Hypoxia is a negative prognostic indicator of solid tumors, which not only changes the survival state of tumors and increases their invasiveness but also remarkably reduces the sensitivity of tumors to treatments such as radiotherapy, chemotherapy and photodynamic therapy. Thus, developing therapeutic strategies to alleviate tumor hypoxia has recently been considered an extremely valuable target in oncology. In this review, nanotechnological strategies to elevate oxygen levels in tumor therapy in recent years are summarized, including (I) improving the hypoxic tumor microenvironment, (II) oxygen delivery to hypoxic tumors, and (III) oxygen generation in hypoxic tumors. Finally, the challenges and prospects of these nanotechnological strategies for alleviating tumor hypoxia are presented.

A Cascade Nanoreactor of Metal-Protein-Polyphenol Capsule for Oxygen-Mediated Synergistic Tumor Starvation and Chemodynamic Therapy

Starvation therapy kills tumor cells via consuming glucose to cut off their energy supply. However, since glucose oxidase (GOx)-mediated glycolysis is oxygen-dependent, the cascade reaction based on GOx faces the challenge of a hypoxic tumor microenvironment. By decomposition of glycolysis production of H₂ O₂ into O₂ , starvation therapy can be enhanced, but chemodynamic therapy is limited. Here, a close-loop strategy for on demand H₂ O₂ and O₂ delivery, release, and recycling is proposed. The nanoreactor (metal-protein-polyphenol capsule) is designed by incorporating two native proteins, GOx and hemoglobin (Hb), in polyphenol networks with zeolitic imidazolate framework as sacrificial templates. Glycolysis occurs in the presence of GOx with O₂ consumption and the produced H₂ O₂ reacts with Hb to produce highly cytotoxic hydroxyl radicals (•OH) and methemoglobin (MHb) (Fenton reaction). Benefiting from the different oxygen carrying capacities of Hb and MHb, oxygen on Hb is rapidly released to supplement its consumption during glycolysis. Glycolysis and Fenton reactions are mutually reinforced by oxygen supply, consuming more glucose and producing more hydroxyl radicals and ultimately enhancing both starvation therapy and chemodynamic therapy. This cascade nanoreactor exhibits high efficiency for tumor suppression and provides an effective strategy for oxygen-mediated synergistic starvation therapy and chemodynamic therapy.

Research Progress of Nanomedicine-Based Mild Photothermal Therapy in Tumor

With the booming development of nanomedicine, mild photothermal therapy (mPTT, 42-45°C) has exhibited promising potential in tumor therapy. Compared with traditional PTT (>50°C), mPTT has less side effects and better biological effects conducive to tumor treatment, such as loosening the dense structure in tumor tissues, enhancing blood perfusion, and improving the immunosuppressive microenvironment. However, such a relatively low temperature cannot allow mPTT to completely eradicate tumors, and therefore, substantial efforts have been conducted to optimize the application of mPTT in tumor therapy. This review extensively summarizes the latest advances of mPTT, including two sections: (1) taking mPTT as a leading role to maximize its effect by blocking the cell defense mechanisms, and (2) regarding mPTT as a supporting role to assist other therapies to achieve synergistic antitumor curative effect. Meanwhile, the special characteristics and imaging capabilities of nanoplatforms applied in various therapies are discussed. At last, this paper puts forward the bottlenecks and challenges in the current research path of mPTT, and possible solutions and research directions in future are proposed correspondingly.

A dual-response drug delivery system with X-ray and ROS to boost the anti-tumor efficiency of TPZ via enhancement of tumor hypoxia levels

The selective anti-tumor activity and less toxic nature of hypoxia-activated prodrugs including tirapazamine (TPZ) are harbored by hypoxia levels in tumors, the inadequacy of which leads to failure in clinical trials. Thus, the development of effective clinical applications of TPZ requires advanced strategies to intensify hypoxia levels in tumors effectively and safely. In this study, we designed and fabricated a paclitaxel (PTX)-loaded dual-response delivery system with a low dose (e.g., 2 Gy) of X-ray and reactive oxygen species on the basis of diselenide block copolymers. Upon the external X-ray stimulus, the system accurately released encapsulated PTX at tumor sites and remarkably improved tumor hypoxia levels by causing severe damage to tumor blood vessels. Subsequently, these enhanced tumor hypoxia levels effectively activated the reduction of TPZ into benzotriazinyl free radicals, which significantly improved the antitumor efficacy of our system against 4T1 breast cancer cells with an initial tumor volume of 500 mm³. Moreover, the dual-stimulus coordinated and controlled release of PTX was found to largely avoid the off-target effects of PTX on normal cells while exhibiting very limited side effects in experimental mice. The current novel strategy for regulating tumor hypoxia levels offers an effective and safe way to activate TPZ for the treatment of large solid tumors.

An Enzyme-Engineered Nonporous Copper(I) Coordination Polymer Nanoplatform for Cuproptosis-Based Synergistic Cancer Therapy

Cuproptosis, a newly identified form of regulated cell death that is copper-dependent, offers great opportunities for exploring the use of copper-based nanomaterials inducing cuproptosis for cancer treatment. Here, a glucose oxidase (GOx)-engineered nonporous copper(I) 1,2,4-triazolate ([Cu(tz)]) coordination polymer (CP) nanoplatform, denoted as GOx@[Cu(tz)], for starvation-augmented cuproptosis and photodynamic synergistic therapy is developed. Importantly, the catalytic activity of GOx is shielded in the nonporous scaffold but can be "turned on" for efficient glucose depletion only upon glutathione (GSH) stimulation in cancer cells, thereby proceeding cancer starvation therapy. The depletion of glucose and GSH sensitizes cancer cells to the GOx@[Cu(tz)]-mediated cuproptosis, producing aggregation of lipoylated mitochondrial proteins, the target of copper-induced toxicity. The increased intracellular hydrogen peroxide (H₂ O₂ ) levels, due to the oxidation of glucose, activates the type I photodynamic therapy (PDT) efficacy of GOx@[Cu(tz)]. The in vivo experimental results indicate that GOx@[Cu(tz)] produces negligible systemic toxicity and inhibits tumor growth by 92.4% in athymic mice bearing 5637 bladder tumors. This is thought to be the first report of a cupreous nanomaterial capable of inducing cuproptosis and cuproptosis-based synergistic therapy in bladder cancer, which should invigorate studies pursuing rational design of efficacious cancer therapy strategies based on cuproptosis.

Smart pH-responsive polyhydralazine/bortezomib nanoparticles for remodeling tumor microenvironment and enhancing chemotherapy

The clinical translation of nanomedicines has been impeded by the unfavorable tumor microenvironment (TME), particularly the tortuous vasculature networks, which significantly influence the transport and distribution of nanomedicines into tumors. In this work, a smart pH-responsive bortezomib (BTZ)-loaded polyhydralazine nanoparticle (PHDZ/BTZ) is presented, which has a great capacity to augment the accumulation of BTZ in tumors by dilating tumor blood vessels via specific release of vasodilator hydralazine (HDZ). The Lewis acid-base coordination effect between the boronic bond of BTZ and amino of HDZ empowered PHDZ/BTZ nanoparticles with great stability and high drug loading contents. Once triggered by the acidic tumor environment, HDZ could be released quickly to remodel TME through tumor vessel dilation, hypoxia attenuation, and lead to an increased intratumoral BTZ accumulation. Additionally, our investigation revealed that this pH-responsive nanoparticle dramatically suppressed tumor growth, inhibited the occurrence of lung metastasis with fewer side effects and induced immunogenic cell death (ICD), thereby eliciting immune activation including massive cytotoxic T lymphocytes (CTLs) infiltration in tumors and efficient serum proinflammatory cytokine secretion compared with free BTZ treatment. Thus, with efficient drug loading capacity and potent immune activation, PHDZ nanoparticles exhibit great potential in the delivery of boronic acid-containing drugs aimed at a wide range of diseases.

Glucose Metabolism Intervention-Facilitated Nanomedicine Therapy

Ordinarily, cancer cells possess features of abnormally increased nutrient intake and metabolic pathways. The disorder of glucose metabolism is the most important among them. Therefore, starvation therapy targeting glucose metabolism specifically, which results in metabolic disorders, restricted synthesis, and inhibition of tumor growth, has been developed for cancer therapy. However, issues such as inadequate targeting effectiveness and drug tolerance impede their clinical transformation. In recent years, nanomaterial-assisted starvation treatment has made significant progress in addressing these challenges, whether as a monotherapy or in combination with other medications. Herein, representative researches on the construction of nanosystems conducting starvation therapy are introduced. Elaborate designs and interactions between different treatment mechanisms are meticulously mentioned. Not only are traditional treatments based on glucose oxidase involved, but also newly sprung small molecule agents targeting glucose metabolism. The obstacles and potential for advancing these anticancer therapies were also highlighted in this review.

Multifunctional metal-organic framework-based nanoreactor for starvation/oxidation improved indoleamine 2,3-dioxygenase-blockade tumor immunotherapy

Inhibited immune response and low levels of delivery restrict starvation cancer therapy efficacy. Here, we report on the co-delivery of glucose oxidase (GOx) and indoleamine 2,3-dioxygenase (IDO) inhibitor 1-methyltryptophan using a metal-organic framework (MOF)-based nanoreactor, showing an amplified release for tumor starvation/oxidation immunotherapy. The nanosystem significantly overcomes the biobarriers associated with tumor penetration and improves the cargo bioavailability owing to the weakly acidic tumor microenvironment-activated charge reversal and size reduction strategy. The nanosystem rapidly disassembles and releases cargoes in response to the intracellular reactive oxygen species (ROS). GOx competitively consumes glucose and generates ROS, further inducing the self-amplifiable MOF disassembly and drug release. The starvation/oxidation combined IDO-blockade immunotherapy not only strengthens the immune response and stimulates the immune memory through the GOx-activated tumor starvation and recruitment of effector T cells, but also effectively relieves the immune tolerance by IDO blocking, remarkably inhibiting the tumor growth and metastasis in vivo.

Inhibited immune response and low levels of delivery inhibit starvation cancer therapies. Here, the authors report on the co-delivery of glucose oxidase and IDO inhibitor 1-methyltryptophan using metal organic frameworks and show amplified release in response to starvation therapy along with immune modulatory effects.

Liposomal Glucose Oxidase for Enhanced Photothermal Therapy and Photodynamic Therapy against Breast Tumors

Organic near-infrared fluorescent dye mediated photothermal therapy (PTT) and photodynamic therapy (PDT) suffer from heat shock response, since, heat shock proteins (HSPs) are overexpressed and can repair the proteins damaged by PTT and PDT. Starvation therapy by glucose oxide (GOx) can inhibit the heat shock response by limiting the energy supply. However, the delivery of sufficient and active GOx remains a challenge. To solve this problem, we utilize liposomes as drug carriers and prepare GOx loaded liposome (GOx@Lipo) with a high drug loading content (12.0%) and high enzymatic activity. The successful delivery of GOx shows excellent inhibition of HSPs and enhances PTT and PDT. Additionally, we apply the same liposome formulation to load near-infrared dye 1,1'-dioctadecyl-3,3,3',3'-tetramethylindotricarbo cyanine iodide (DiR) and prepare DiR contained liposomes (DiR@Lipo) for PTT and PDT. The liposomal formulation substantially enhances the PTT and PDT properties of DiR as well as the cellular uptake and tumor accumulation. Finally, the combination therapy shows excellent tumor inhibition on 4T1 tumor-bearing mice. Interestingly, we also find that the starvation therapy can efficiently inhibit tumor metastasis, which is probably due to the immunogenic effect. Our work presents a biocompatible and effective carrier for the combination of starvation therapy and phototherapy, emphasizing the importance of auxiliary starvation therapy against tumor metastasis and offering important guidance for clinical PTT and PDT.

Nanoreactor activated in situ for starvation-chemodynamic therapy of breast cancer

The nano-drug delivery system activated by tumor microenvironment (TME) can effectively treat tumors with low-toxicity. Based on high level of reductive GSH in TME and different coordination properties of Fe ions, this project intended to prepare a GSH-activated cascade catalytic nanoreactor for breast cancer treatment using Fe³⁺/Fe²⁺ as the molecular switch. In this study, the glucose oxidase (GOx) loaded iron alginate nano hydrogel (FeAlg/GOx) was prepared by the simple one-step titration method. Results showed that FeAlg/GOx could remain stable during in vivo circulation to avoid hypoglycaemia. When it reached targeted tumor site, reductive GSH can reduce Fe³⁺ to Fe²⁺. Thereafter, FeAlg/GOx nanogel was broken and GOx was released to consume the essential nutrient glucose (Glu) to achieve tumor starvation therapy. Next, the substrate H₂O₂ generated by the reaction between GOx and Glu can be catalyzed by Fe²⁺ to produce highly cytotoxic •OH in situ, which could further kill tumor cells. The in vivo pharmacodynamics results demonstrated that compared with the control group (V/V0 = 8.36 ± 1.73), FeAlg/GOx group showed the most significant anti-tumor effect with V/V0 of 3.08 ± 1.06. In conclusion, this "inactivated" FeAlg/GOx nanogel can be converted into "activated" therapeutic substances in situ to achieve starvation-chemodynamic combined treatment for breast cancer.

Oxygen self-supplied enzyme nanogels for tumor targeting with amplified synergistic starvation and photodynamic therapy

Tumor tissues need vast supply of nutrients and energy to sustain the rapid proliferation of cancer cells. Cutting off the glucose supply represents a promising cancer therapy approach. Herein, a tumor tissue-targeted enzyme nanogel (rGCP nanogel) with self-supply oxygen capability was developed. The enzyme nanogel synergistically enhanced starvation therapy and photodynamic therapy (PDT) to mitigate the rapid proliferation of cancer cells. The rGCP nanogel was fabricated by copolymerizing two monomers, porphyrin and cancer cells-targeted, Arg-Gly-Asp (RGD), onto the glucose oxidase (GOX) and catalase (CAT) surfaces. The cascade reaction within the rGCP nanogel could efficiently consume intracellular glucose catalyzed by GOX. Concurrently, CAT safely decomposed the produced H₂O₂ with systemic toxicity to promote oxygen generation and achieved low toxicity starvation therapy. The produced oxygen subsequently facilitated the glucose oxidation reaction and significantly enhanced the generation of cytotoxic singlet oxygen (¹O₂) in the presence of 660 nm light irradiation. Combining starvation therapy and PDT, the designed enzyme nanogel system presented an amplified synergic cancer therapy effect. This approach potentially paved a new way to fabricate a combinatorial therapy approach by employing cascaded catalytic nanomedicines with good tumor selectivity and efficient anti-cancer effect. STATEMENT OF SIGNIFICANCE: The performance of starvation and photodynamic therapy (PDT) is usually suppressed by intrinsic tumorous hypoxia. Herein, an oxygen self-supplied and tumor tissue-targeted enzyme nanogel was created by copolymerization of two monomers, porphyrin and cancer cell-targeted Arg-Gly-Asp (RGD), onto the surface of glucose oxidase (GOX) and catalase (CAT), which synergistically enhanced starvation therapy and PDT. Moreover, the enzyme nanogels possessed high stability and could be synthesized straightforwardly. This anti-cancer system provides an approach for constructing a combinatorial therapy approach by employing cascaded catalytic nanomedicine with good tumor selectivity and therapeutic efficacy.

In vivo three-dimensional multispectral photoacoustic imaging of dual enzyme-driven cyclic cascade reaction for tumor catalytic therapy

Non-invasive visualization of dynamic molecular events in real-time via molecular imaging may enable the monitoring of cascade catalytic reactions in living systems, however effective imaging modalities and a robust catalytic reaction system are lacking. Here we utilize three-dimensional (3D) multispectral photoacoustic (PA) molecular imaging to monitor in vivo cascade catalytic therapy based on a dual enzyme-driven cyclic reaction platform. The system consists of a two-dimensional (2D) Pd-based nanozyme conjugated with glucose oxidase (GOx). The combination of nanozyme and GOx can induce the PA signal variation of endogenous molecules. Combined with the PA response of the nanozyme, we can simultaneously map the 3D PA signals of dynamic endogenous and exogenous molecules associated with the catalytic process, thus providing a real-time non-invasive visualization. We can also treat tumors under the navigation of the PA imaging. Therefore, our study demonstrates the imaging-guided potential of 3D multispectral PA imaging in feedback-looped cascade catalytic therapy.

Metal-free bioorthogonal click chemistry in cancer theranostics

Bioorthogonal chemistry is a powerful tool to site-specifically activate drugs in living systems. Bioorthogonal reactions between a pair of biologically reactive groups can rapidly and specifically take place in a mild physiological milieu without perturbing inherent biochemical processes. Attributed to their high selectivity and efficiency, bioorthogonal reactions can significantly decrease background signals in bioimaging. Compared with metal-catalyzed bioorthogonal click reactions, metal-free click reactions are more biocompatible without the metal catalyst-induced cytotoxicity. Although a great number of bioorthogonal chemistry-based strategies have been reported for cancer theranostics, a comprehensive review is scarce to highlight the advantages of these strategies. In this review, recent progress in cancer theranostics guided by metal-free bioorthogonal click chemistry will be depicted in detail. The elaborate design as well as the advantages of bioorthogonal chemistry in tumor theranostics are summarized and future prospects in this emerging field are emphasized.

A hydrogen peroxide economizer for on-demand oxygen production-assisted robust sonodynamic immunotherapy

The outcome of sonodynamic immunotherapy is significantly limited by tumor hypoxia. To overcome this obstacle, one common solution is to catalyze the conversion of endogenous H₂O₂ into O₂. However, the effectiveness of this strategy is limited by the insufficient concentration of H₂O₂ in the tumor microenvironment (TME). Herein, we developed a H₂O₂ economizer for on-demand O₂ supply and sonosensitizer-mediated reactive oxygen species production during ultrasound activation, thereby alleviating hypoxia-associated limitations and augmenting the efficacy of sonodynamic immunotherapy. Methods: The H₂O₂ economizer is constructed by electrostatic adsorption and π-π interactions between the Fe-doped polydiaminopyridine (Fe-PDAP) nanozyme and chlorin e6. By employing a biomimetic engineering strategy with cancer cell membranes, we addressed the premature leakage issue and increased tumor-site accumulation of nanoparticles (membrane-coated Fe-PDAP/Ce6, MFC). Results: The prepared MFC could significantly attenuate the catalytic activity of Fe-PDAP by reducing their contact with H₂O₂. Ultrasound irradiation promoted MFC dissociation and the exposure of Fe-PDAP for a more robust O₂ supply. Moreover, the combination of MFC-enhanced sonodynamic therapy with anti-programmed cell death protein-1 antibody (aPD-1) immune checkpoint blockade induced a strong antitumor response against both primary tumors and distant tumors. Conclusion: This as-prepared H₂O₂ economizer significantly alleviates tumor hypoxia via reducing H₂O₂ expenditure and that on-demand oxygen-elevated sonodynamic immunotherapy can effectively combat tumors.

AgNPs/nGOx/Apra Nanocomposites for Synergistic Antimicrobial Therapy and Scarless Skin Recovery

The misuse of antimicrobials has caused a remarkable increase of antibiotic-resistant bacteria. Developing novel antimicrobial agents with high activity and low rates of resistance development is in great demand yet...

A MXene-Based Bionic Cascaded-Enzyme Nanoreactor for Tumor Phototherapy/Enzyme Dynamic Therapy and Hypoxia-Activated Chemotherapy

The enzyme-mediated elevation of reactive oxygen species (ROS) at the tumor sites has become an emerging strategy for regulating intracellular redox status for anticancer treatment. Herein, we proposed a camouflaged bionic cascaded-enzyme nanoreactor based on Ti₃C₂ nanosheets for combined tumor enzyme dynamic therapy (EDT), phototherapy and deoxygenation-activated chemotherapy. Briefly, glucose oxidase (GOX) and chloroperoxidase (CPO) were chemically conjugated onto Ti₃C₂ nanosheets, where the deoxygenation-activated drug tirapazamine (TPZ) was also loaded, and the Ti₃C₂-GOX-CPO/TPZ (TGCT) was embedded into nanosized cancer cell-derived membrane vesicles with high-expressed CD47 (m_eTGCT). Due to biomimetic membrane camouflage and CD47 overexpression, m_eTGCT exhibited superior immune escape and homologous targeting capacities, which could effectively enhance the tumor preferential targeting and internalization. Once internalized into tumor cells, the cascade reaction of GOX and CPO could generate HClO for efficient EDT. Simultaneously, additional laser irradiation could accelerate the enzymic-catalytic reaction rate and increase the generation of singlet oxygen (¹O₂). Furthermore, local hypoxia environment with the oxygen depletion by EDT would activate deoxygenation-sensitive prodrug for additional chemotherapy. Consequently, m_eTGCT exhibits amplified synergistic therapeutic effects of tumor phototherapy, EDT and chemotherapy for efficient tumor inhibition. This intelligent cascaded-enzyme nanoreactor provides a promising approach to achieve concurrent and significant antitumor therapy.

Graphene quantum dots‐based targeted nanoprobes detecting drug delivery, imaging, and enhanced chemotherapy of nasopharyngeal carcinoma

One of the main clinical treatments for advanced nasopharyngeal carcinoma is chemotherapy, but systemic administration can cause serious adverse reactions. New type of nanomaterial which can actively targeting, imaging, and treating nasopharyngeal carcinoma at the same time to enhance the effect of chemotherapy, meanwhile monitoring the intracellular drug release process at the level of single cancer cell was urgently needed. GE11, an EGFR antagonist peptide, was used to target nasopharyngeal carcinoma which has positive expression of EGFR on its nucleus. GE11‐modified graphene quantum dots (GQDs@GE11) were used as drug carriers for clinical chemotherapeutics cisplatin (CDDP) and doxorubicin (DOX). The emission spectrum of GQDs (460 nm) and the excitation spectrum of DOX (470 nm) have a good overlap, thus the transfer and release process of DOX can be sensitively detected by the fluorescence resonance energy transfer (FRET). CDDP was used to enhance the chemotherapy effect of nanoprobe, and the loading amount of DOX and CDDP on GQDs@GE11 nanoprobe were up to 67 and 50 mg/g, respectively. In vivo experiments have confirmed that GQDs@GE11/CDDP/DOX nanoprobe can be enriched to tumor site through specific targeting effect, and significantly inhibit tumor cell proliferation. This new type of targeted therapy fluorescent probe provides new ideas for the study of drug release process and the treatment of nasopharyngeal carcinoma.

Rational design of non-toxic GOx-based biocatalytic nanoreactor for multimodal synergistic therapy and tumor metastasis suppression

Rationale: Glucose oxidase (GOx)-based biocatalytic nanoreactors can cut off the energy supply of tumors for starvation therapy and deoxygenation-activated chemotherapy. However, these nanoreactors, including mesoporous silica, calcium phosphate, metal-organic framework, or polymer nanocarriers, cannot completely block the reaction of GOx with glucose in the blood, inducing systemic toxicity from hydrogen peroxide (H₂O₂) and anoxia. The low enzyme loading capacity can reduce systemic toxicity but limits its therapeutic effect. Here, we describe a real 'ON/OFF' intelligent nanoreactor with a core-shell structure (GOx + tirazapamine (TPZ))/ZIF-8@ZIF-8 modified with the red cell membrane (GTZ@Z-RBM) for cargo delivery.

Methods: GTZ@Z-RBM nanoparticles (NPs) were prepared by the co-precipitation and epitaxial growth process under mild conditions. The core-shell structure loaded with GOx and TPZ was characterized for hydrate particle size and surface charge. The GTZ@Z-RBM NPs morphology, drug, and GOx loading/releasing abilities, system toxicity, multimodal synergistic therapy, and tumor metastasis suppression were investigated. The in vitro and in vivo outcomes of GTZ@Z-RBM NPs were assessed in 4T1 breast cancer cells.

Results: GTZ@Z-RBM NPs could spatially isolate the enzyme from glucose in a physiological environment, reducing systemic toxicity. The fabricated nanoreactor with high enzyme loading capacity and good biocompatibility could deliver GOx and TPZ to the tumors, thereby exhausting glucose, generating H₂O₂, and aggravating hypoxic microenvironment for starvation therapy, DNA damage, and deoxygenation-activated chemotherapy. Significantly, the synergistic therapy effectively suppressed the breast cancer metastasis in mice and prolonged life without systemic toxicity. The in vitro and in vivo results provided evidence that our biomimetic nanoreactor had a powerful synergistic cascade effect in treating breast cancer.

Conclusion: GTZ@Z-RBM NPs can be used as an 'ON/OFF' intelligent nanoreactor to deliver GOx and TPZ for multimodal synergistic therapy and tumor metastasis suppression.

A tyrosinase-responsive tumor-specific cascade amplification drug release system for melanoma therapy

Tumor-selective drug delivery could enhance anticancer efficacy and avoid drug side effects. However, because of tumor heterogeneity, current nanoparticle-based drug delivery systems rarely improve clinical outcomes significantly, commonly only reducing systemic toxicity. In this work, a new tumor-specific, tyrosinase-responsive cascade amplification release nanoparticle (TR-CARN) was developed to fulfill the needs for tumor-specific drug delivery and high efficacy cancer treatment. Tyrosinase (Tyr) is specifically expressed in melanomas and can catalyze acetaminophen (APAP) to increase reactive oxygen species (ROS). It was therefore utilized here to initiate the ROS amplification procedure. In TR-CARN, a ROS-responsive prodrug BDOX was loaded into an amphiphilic polymer, and APAP was linked to the polymer through a ROS-cleavable thioether bond. TR-CARN caused reduced side effects during the delivery because of the low toxicity of BDOX. Once TR-CARN entered into the tumor, endogenous ROS triggered initial APAP and BDOX release. Tyr-mediated ROS synthesis by APAP then accelerated APAP and BDOX release and toxification. Consequently, TR-CARN achieved melanoma-specific treatment of high efficacy through the cascade amplification strategy with enhanced biosafety.