Glucose Oxidase-Instructed Multimodal Synergistic Cancer Therapy

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.

Enzyme-Engineered Conjugated Polymer Nanoplatform for Activatable Companion Diagnostics and Multistage Augmented Synergistic Therapy

Companion diagnostics (CDx) provides critical information for precision medicine. However, current CDx is mostly limited to in vitro tests, which cannot accurately evaluate the disease progression and treatment response in real time. To overcome this challenge, herein a glucose oxidase (GOx)-engineered conjugated polymer (polyaniline, PANI) nanoplatform (denoted as PANITG) is reported for activatable imaging-based CDx and multistage augmented photothermal/starvation synergistic therapy. PANITG comprises a pH-activatable conjugated polymer as a photothermal convertor and photoacoustic (PA) emitter, a GOx as a cancer starvation inducer as well as a H₂ O₂ and acid producer, and a H₂ O₂ -cleavable linker as a "switch" for GOx activity. The in vivo PA imaging and photothermal therapy abilities are activated by acidic tumor microenvironment and self-augmented by the reaction between GOx and glucose. Meanwhile, the photothermal effect will enhance the GOx activity in turn. Such multistage augmentation of the therapeutic effects will facilitate effective cancer management. In addition, the in vivo PA imaging with PANITG reveals the tumor pH level which is correlated to the efficiency of the photothermal therapy and to the catalytic activity of GOx at each stage, enabling real-time activatable CDx.

Improving the Therapeutic Efficiency of Hypoxic-Activated Prodrugs by Enhancing Hypoxia in Solid Tumors

The low sensitivity of hypoxic regions in solid tumors to radiotherapy and chemotherapy remains a major obstacle to cancer treatment. By taking advantage of hypoxic-activated prodrugs, tirapazamine (TPZ), generating cytotoxic reductive products and the glucose oxidase (GO_x)-based glucose oxidation reaction, we designed a nanodrug-loading system that combined TPZ-induced chemotherapy with GO_x-mediated cancer-orchestrated starvation therapy and cancer oxidation therapy. In this work, we first prepared mesoporous silica (MSN) loaded with TPZ. Then, in order to prevent the leakage of TPZ in advance, the surface was coated with a layer of carMOF formed by Fe³⁺ and carbenicillin (car), and GO_x was adsorbed on the outermost layer to form the final nanosystem MSN-TPZ@carMOF-GO_x (MT@c-G). GO_x could effectively consume oxygen and catalyzed glucose into gluconic acid and hydrogen peroxide. First, the generated gluconic acid lowered the pH of tumor tissues, promoted the decomposition of carMOF, and released TPZ. Second, oxygen consumption could improve the degree of hypoxia in tumor tissues, so that enhanced the activity of TPZ. Furthermore, GO_x could generate cancer-orchestrated starvation/oxidation therapy. Therefore, our study provided a new strategy that TPZ combined with GO_x achieved starvation/oxidation/chemotherapy for enhancing anticancer effects in hypoxic regions.

Disruption of dual homeostasis by a metal-organic framework nanoreactor for ferroptosis-based immunotherapy of tumor

Ferroptosis, a newfound non-apoptotic cell death pathway that is iron- and reactive oxygen species (ROS)-dependent, has shown a promise for tumor treatment. However, engineering ferroptosis inducers with sufficient hydrogen peroxide (H₂O₂) and iron supplying capacity remains a great challenge. To address this issue, herein, we report a powerful nanoreactor by modifying MnO₂, glucose oxidase, and polyethylene glycol on iron-based metal-organic framework nanoparticles for disrupting redox and iron metabolism homeostasis, directly providing the Fenton reaction-independent downstream ferroptosis for tumor therapy. By consuming glutathione and oxidizing glucose to increase the H₂O₂ level in cancer cells and downregulating ferroportin 1 to accumulate intracellular iron ions, the homeostasis disruptor could effectively enhance the ferroptosis. Subsequently, the ferroptosis cells release tumor immune-associated antigens, which combine with in situ injected aptamer-PD-L1 to further strengthen the tumor treatment efficiency. This work not only paves a way to enhance the efficacy of ferroptosis-based cancer therapy by associating intracellular redox homeostasis with the iron metabolism system in tumor cells but also offers an engineered nanoreactor as a promising mimetic antigen for activating immunotherapy.

Targeted-detection and sequential-treatment of small hepatocellular carcinoma in the complex liver environment by GPC-3-targeted nanoparticles

Despite advancements in diagnostic methods and therapeutic strategies, the mortality rate of hepatocellular carcinoma (HCC) remains as high as its incidence rate. Most liver cancers are detected in the advanced stages, when treatment options are limited. Small HCC is difficult to diagnose and is often overlooked by current imaging methods because of the complexity of the liver environment, especially in cirrhotic livers. In the present study, we developed a tumor "cruise missile", mesoporous Fe₃O₄-containing glucose oxidase-conjugated GPC3 peptide nanoparticles (FGP NPs). It was designed to enhance the accuracy of small HCC visualization to 85.7% using combined ultrasound/photoacoustic imaging in complex liver environment, which facilitated sequential catalytic targeted therapy for small HCC. In a carcinogen-induced mouse HCC model, FGP NPs could be used to accurately diagnose HCC in a liver cirrhosis background as well as distinguish HCC nodules from other abnormal liver nodules, such as cirrhosis nodules and necrotic nodules, by dynamic contrast-enhanced photoacoustic imaging. In a mouse xenograft HCC model, highly reactive oxygen species were formed by sequential catalytic reactions, which promoted HCC cell apoptosis, significantly increasing the survival of the model mice. The present study provides a basis for the precise detection and elimination of small HCCs in the complex liver environment.

A Copper Peroxide Fenton Nanoagent-Hydrogel as an In Situ pH-Responsive Wound Dressing for Effectively Trapping and Eliminating Bacteria

Bacterial infection has been a great threat to wounds due to the abuse of antibiotics and drug resistance. Elaborately constructing an efficient antibacterial strategy for accelerated healing of bacteria-infected wounds is of great importance. Herein, we develop a transferrin-conjugated copper peroxide nanoparticle-hydrogel (denoted as CP@Tf-hy) wound dressing with no toxicity to mammalian cells at a test dosage. When exposed to an initial acidic wound environment, the CP@Tf-hy simultaneously displays in situ self-supplied H₂O₂ and pH-responsive release of Fenton catalytic copper ions accompanied by highly toxic hydroxyl radical (•OH) generation against antibiotic-resistant bacteria. Meanwhile, the positively charged CP@Tf-hy can efficiently trap and restrain negatively charged bacteria to the range of •OH destruction to greatly overcome its intrinsic disadvantages of short life and diffusion distance. Importantly, the CP@Tf-hy consumes the bacterial overexpressed antioxidant glutathione while boosting Fenton catalytic copper(I) ions to generate more •OH. The synergistic effects of the enhanced Fenton reaction, responsive copper ion release, and bacterial trapping can achieve high bacterial elimination efficacy (7 log reduction). In vivo investigations demonstrate that the porous CP@Tf-hy significantly promotes hemostasis, cell proliferation, and migration of the wound, consequently accelerating bacteria-infected wound healing. The safe, low-cost, and all-in-one CP@Tf-hy holds great prospects as an antibacterial dressing for rapid resistant bacteria-infected purulent wound healing.

Antibacterial Cascade Catalytic Glutathione-Depleting MOF Nanoreactors

Nanozymes with peroxidase-like activity have great application potential in combating pathogenic bacterial infections and are expected to become an alternative to antibiotics. However, the near-neutral pH and high glutathione (GSH) levels in the bacterial infection microenvironment severely limit their applications in antibacterial therapy. In this work, a metal-organic framework (MOF)-based cascade catalytic glutathione-depleting system named MnFe2O4@MIL/Au&GOx (MMAG) was constructed. The MMAG cascade-catalyzed glucose to provide H+ and produces a large amount of toxic reactive oxygen species. In addition, MMAG consumed GSH, which can result in bacterial death more easily. Systematic antibacterial experiments illustrated that MMAG has superior antibacterial effects on both Gram-positive bacteria and Gram-negative bacteria.

Programmed Stimuli-Responsive Carbon Dot-Nanogel Hybrids for Imaging-Guided Enhanced Tumor Phototherapy

For harmonizing the contradiction of nanotheranostic agents between enhanced tumor accumulation and penetration, efficient cell internalization and fast elimination are key tactics for promoting their clinical applications. Herein, programmed stimuli-responsive poly(N-isopropylacrylamide)-carbon dot (PNIPAM-CD) hybrid nanogels are designed to address the abovementioned conflicts. The enlarged particle size of PNIPAM-CDs enables one to effectively improve their accumulation at tumor sites. Once the hybrid nanogels are docked in tumors and exposed to deep-red-light (660 nm) irradiation, heat and reactive oxygen species (ROS) are generated from the CDs, consequently activating photothermal therapy (PTT) and photodynamic therapy (PDT) effects and meanwhile inducing partial degradation of PNIPAM-CDs for deep tissue penetration. Further, enhanced cellular internalization of the functional components can be achieved owing to the pH-responsive charge reversal and temperature-dependent hydrophilic/hydrophobic conversion characteristics of PNIPAM-CDs. Finally, the overexpressed glutathione (GSH) in tumor cells would trigger further cleavage of the partially degraded hybrid nanogels, which is beneficial for their rapid clearance from the body. This work not only proposed a novel strategy to fabricate nanotheranostic agents using just a single functional component (i.e., the versatile CDs) to simplify the preparation process but also achieved effective delivery of agents into tumor cells by overcoming the multiple biological barriers to enhance therapeutic efficacy and decrease side effects.

A Potent Strategy of Combinational Blow Toward Enhanced Cancer Chemo-Photodynamic Therapy via Sustainable GSH Elimination

Excessive glutathione (GSH), which is produced owing to abnormal metabolism of tumor cells, scavenges photo-induced reactive oxygen species (ROS) and consumes chemotherapeutic drugs, thereby attenuating the efficacy of photodynamic therapy and chemotherapy, respectively. Predominant strategies for GSH inhibition involve its chemical depletion, which only leads to a temporary therapeutic effect because GSH is replenished via various compensatory routes in tumor cells. Here, a versatile GSH-inhibiting nanosystem (termed PCNPs) for persistent synergistic therapy of cancer is reported. The porous skeleton of PCNPs allows easy encapsulation of buthionine sulfoximine (BSO) to sustainably suppress the biosynthesis of GSH. Thus, PCNPs not only demonstrate a prolonged release of BSO and improve drug utilization for efficient chemotherapy, but also act as an efficient photo-induced singlet oxygen radical generator that prevents the loss of ROS, thereby enhancing photodynamic therapy. In addition, the liposomal coating prevents cargo release in the blood, improves the accumulation of PCNPs at the tumor site, and promotes the cellular uptake of oxaliplatin and BSO. This strategy is applicable to ROS-based therapy and chemotherapy, which are suppressed by GSH, and may further enhance the synergistic effect of GSH-restrained therapy.

Glucose-responsive multifunctional metal-organic drug-loaded hydrogel for diabetic wound healing

As the incidence of diabetes increases, its complication, diabetic foot ulcers, has become the main type of clinically chronic refractory wounds. Due to the hyperglycemic microenvironment of the diabetic wound, which leads to vascular defects and bacterial growth, the therapeutic effect of wound dressings lacking strategic design is relatively limited. In this study, we designed an injectable, "self-healing", and glucose-responsive multifunctional metal-organic drug-loaded hydrogel (DG@Gel) for diabetic wound healing. The functionalized hydrogel was prepared by phase-transfer-mediated metallo-nanodrugs, which were made by co-assembling zinc ions, organic ligands, and a small-molecule drug, deferoxamine mesylate (DFO), and the programmed loading of glucose oxidase (GOX). When injected into a diabetic wound, the GOX in DG@Gel changed the hyperglycemic wound microenvironment by decomposing excess glucose into hydrogen peroxide and glucuronic acid, which decreased the pH of the wound site. The low pH promoted the release of zinc ions and DFO, which exhibited synergistic antibacterial and angiogenesis activity for diabetic wound repair. In vitro experiments revealed the antibacterial activity and the cell proliferation, migration, and tube formation ability of DG@Gel. Moreover, in vivo experiments showed that DG@Gel can induce re-epithelialization, collagen deposition, and angiogenesis during wound healing in diabetic mice with good biocompatibility and biodegradability. The results suggest that this hydrogel is a promising innovative dressing for the treatment of diabetic wounds. STATEMENT OF SIGNIFICANCE: Diabetic ulcers, as one of the main types of chronic refractory wounds, are not treated effectively in the clinic due to a lack of strategic approach. In this study, we designed a glucose-responsive multifunctional metal-organic drug-loaded hydrogel (DG@Gel), which can change the hyperglycemic wound microenvironment by decomposing excess glucose into hydrogen peroxide and glucuronic acid. This in turn promoted the release of zinc ions and deferoxamine mesylate (DFO) in the hydrogel, which exhibited synergistic antibacterial and angiogenic activity for diabetic wound repair. Furthermore, the DG@Gel exhibited good biocompatibility and biodegradability in vivo. In general, this innovative strategy design may have great application potential in the treatment of various chronic wounds.

A "Valve-Closing" Starvation Strategy for Amplification of Tumor-Specific Chemotherapy

Starvation-dependent differential stress sensitization effect between normal and tumor cells provides a potentially promising strategy to amplify chemotherapy effects and reduce side effects. However, the conventional starvation approaches such as glucose oxidase (Gox)-induced glucose depletion and nanomedicine-enabled vascular embolism usually suffer from aggravated tumor hypoxia, systemic toxicity, and unpredictable metabolic syndrome. Herein, a novel "valve-closing" starvation strategy is developed to amplify the chemotherapy effects via closing the "valve" of glucose transported into tumor cells, which is accomplished by a glucose transporters 1 (GLUT1, valve of glucose uptake) inhibitor (Genistein, Gen) and chemotherapeutic agent (Curcumin, Cur) coloaded hybrid organosilica-micelles nanomedicine (designated as (Gen + Cur)@FOS) with controllable stability. In vitro and in vivo results demonstrate that (Gen + Cur)@FOS can effectively reduce glucose/adenosine triphosphate levels in tumor cells by inhibiting GLUT1 expression (i.e., "valve-closing") to induce the starvation of tumor cells, thus weakening the resistance of tumor cells to apoptosis caused by chemotherapy, and consequently contributing to the remarkably improved antitumor efficiency and minimized side effects based on the stress sensitization effect mediated by GLUT1 inhibition-induced starvation. This "valve-closing" starvation strategy provides a promising paradigm for the development of novel nanotherapeutics with amplified chemotherapy effect.

Albumin-Based Therapeutics Capable of Glutathione Consumption and Hydrogen Peroxide Generation for Synergetic Chemodynamic and Chemotherapy of Cancer

A nanoscale therapeutic system with good biocompatibility was facilely fabricated by the coassembly of human serum albumin and glucose oxidase (GOD), where the former was pretreated with metal ions through a chelating agent or the chemotherapeutic prodrug oxaliplatin (Oxa(IV)). Among different chelating metal ions used, Mn²⁺ ion was selected to produce hydroxyl radical (•OH) efficiently through Fenton-like reaction, while GOD loaded in the system was able to generate a large amount of hydrogen peroxide for promoting efficient conversion into highly toxic •OH. In the meanwhile, the conversion of the Oxa(IV) prodrug into chemotherapeutic Oxa(II) was beneficial for the consumption of glutathione, thereby enhancing the chemodynamic therapy (CDT) efficacy. Based on the combined chemotherapy and CDT, the treatment with this system leads to superior antitumor outcome.

Concentrically Encapsulated Dual-Enzyme Capsules for Synergistic Metabolic Disorder Redressing and Cytotoxic Intermediates Scavenging

Enzyme therapy has important implications for the treatment of metabolic disorders and biological detoxification. It remains challenging to prepare enzymatic nanoreactors with high therapeutic efficiency and low emission of cytotoxic reaction intermediates. Here, we propose a novel strategy for the preparation of enzymes-loaded polypeptide microcapsules (EPM) with concentrically encapsulated enzymes to achieve higher cascade reaction rates and minimal emission of cytotoxic intermediates. Mesoporous silica spheres (MSS) are used as a highly porous matrix to efficiently load a therapeutic enzyme (glucose oxidase, GOx), and a layer-by-layer (LbL) assembly strategy is employed to assemble the scavenging enzyme (catalase) and polyelectrolyte multilayers on the MSS surface. After removal of the MSS, a concentrically encapsulated EPM is obtained with the therapeutic enzyme encapsulated inside the capsule, and the scavenging enzyme immobilized in the polypeptide multilayer shell. Performance of the concentrically encapsulated GOx-catalase capsules is investigated for synergistic glucose metabolism disturbance correction and cytotoxic intermediate H₂O₂ clearance. The results show that the EPM can simultaneously achieve 99% H₂O₂ clearance and doubled glucose consumption rate. This strategy can be extended to the preparation of other dual- or multi-enzyme therapeutic nanoreactors, showing great promise in the treatment of metabolic disorders.

Enhanced ROS-Boosted Phototherapy against Pancreatic Cancer via Nrf2-Mediated Stress-Defense Pathway Suppression and Ferroptosis Induction

In situ oxygen generation is the most common strategy to boost reactive oxygen species (ROS) for enhancing the efficacy of phototherapy in cancer, including photodynamic therapy (PDT) and photothermal therapy (PTT). However, hyperoxidation or hyperthermia often triggers stress-defense pathways and promotes tumor cell survival, thus severely limiting the therapeutic efficacy. To overcome the tumor hypoxia and thermal resistance existing in phototherapy, we constructed a self-synergistic nanoplatform for tumors by incorporating brusatol, a nuclear factor erythroid 2-related factor (Nrf2) inhibitor, into the silica nanonetwork. It was then sequentially decorated with MnO₂ and the photosensitizer chlorin e6 (Ce6) and then coated with poly(ethylene glycol)-folate (PEG-FA)-functionalized polydopamine (PDA) (designated as brusatol/silica@MnO₂/Ce6@PDA-PEG-FA). As an oxygen generator, MnO₂ can promote ROS production, which not only directly enhances Ce6-mediated PDT but also strengthens PDA-mediated PTT by attacking heat shock proteins (HSPs). Particularly, brusatol could efficiently inhibit the activation of Nrf2 defense pathway under hyperoxidation and hyperthermia and cause glutathione peroxidase 4 (GPX4) and ferritin heavy chain (FTH) inactivation, thereby inducing ferroptosis and ultimately enhancing the phototherapeutic effects. By exploiting these features, brusatol/silica@MnO₂/Ce6@PDA-PEG-FA exhibited excellent antitumor efficacy with enhanced PDT and PTT both in in vitro and in vivo studies. Overall, our work highlights a promising strategy against hypoxia- and hyperthermia-associated resistance in phototherapy via suppressing stress-defense system and inducing ferroptosis.

Bimetal metal-organic framework domino micro-reactor for synergistic antibacterial starvation/chemodynamic therapy and robust wound healing

Antibacterial chemodynamic therapy (aCDT) has captured considerable attention in the treatment of pathogen-induced infections due to its potential to inactivate bacteria through germicidal reactive oxygen species (ROS). However, the lifespan of ROS generated by CDT is too short to achieve the efficacy of complete sterilization; thus, residual bacteria inevitably reproduce and cause super-infections. To address this concern, we devise an innovative bimetal, metal-organic framework (BMOF) domino micro-reactor (BMOF-DMR), consisting of Cu/Zn-rich BMOF and glucose oxidase (GOx), via electrostatic self-assembly. GOx catalyzes conversion of glucose into H₂O₂, and the Cu²⁺ ions then convert H₂O₂ into ˙OH to kill bacteria, thereby showing a domino effect. Accordingly, the BMOF-DMR not only blocks the nutrient/energy supply for bacteria, but also triggers a Fenton(-like) reaction and glutathione (GSH) depletion in a self-generating H₂O₂ microenvironment, all leading to high-efficiency bactericidal performance through synergistic starvation/chemodynamic therapy. Remarkably, in vitro and in vivo assessments demonstrate that the BMOF-DMR has superior cytocompatibility and exhibits robust ability to accelerate infectious full-thickness cutaneous regeneration through eradicating bacteria, promoting epithelialization of the wound beds and facilitating angiogenesis from the antibacterial activity and delivery of bimetal elements. The advantage of this antibacterial platform is that it suppresses bacterial metabolism by blocking the energy supply, which might prevent secondary infections from residual bacteria. As envisaged, the use of such a micro-reactor with starvation/chemodynamic therapy is a promising approach for combating bacterial skin wounds.

In Situ Sprayed Starvation/Chemodynamic Therapeutic Gel for Post-Surgical Treatment of IDH1 (R132H) Glioma

Complete resection of isocitrate dehydrogenase 1 (IDH1) (R132H) glioma is unfeasible and the classic post-surgical chemo/radiotherapy suffers from high recurrence and low survival rate. IDH1 (R132H) cells are sensitive to low concentrations of glucose and high concentrations of reactive oxygen species (ROS) due to inherent metabolism reprograming. Hence, a starvation/chemodynamic therapeutic gel is developed to combat residual IDH1 (R132H) tumor cells after surgery. Briefly, glucose oxidase (GOx) is mineralized with manganese-doped calcium phosphate to form GOx@MnCaP nanoparticles, which are encapsulated into the fibrin gel (GOx@MnCaP@fibrin). After spraying gel in the surgical cavity, GOx catalyzes the oxidation of glucose in residual IDH1 (R132H) cells and produces H₂ O₂ . The generated H₂ O₂ is further converted into highly lethal hydroxyl radicals (•OH) by a Mn²⁺ -mediated Fenton-like reaction to further kill the residual IDH1 (R132H) cells. The as-prepared starvation/chemodynamic therapeutic gel shows much higher therapeutic efficacy toward IDH1 (R132H) cells than IDH1 (WT) cells, and achieves long-term survival.

Stimuli-Responsive Nanoparticles for Controlled Drug Delivery in Synergistic Cancer Immunotherapy

Cancer immunotherapy has achieved promising clinical progress over the recent years for its potential to treat metastatic tumors and inhibit their recurrences effectively. However, low patient response rates and dose-limiting toxicity remain as major dilemmas for immunotherapy. Stimuli-responsive nanoparticles (srNPs) combined with immunotherapy offer the possibility to amplify anti-tumor immune responses, where the weak acidity, high concentration of glutathione, overexpressions of enzymes, and reactive oxygen species, and external stimuli in tumors act as triggers for controlled drug release. This review highlights the design of srNPs based on tumor microenvironment and/or external stimuli to combine with different anti-tumor drugs, especially the immunoregulatory agents, which eventually realize synergistic immunotherapy of malignant primary or metastatic tumors and acquire a long-term immune memory to prevent tumor recurrence. The authors hope that this review can provide theoretical guidance for the construction and clinical transformation of smart srNPs for controlled drug delivery in synergistic cancer immunotherapy.

Stabilizing Enzymes in Plasmonic Silk Film for Synergistic Therapy of In Situ SERS Identified Bacteria

Increasing antibiotic resistance becomes a serious threat to public health. Photothermal therapy (PTT) and antibacterial enzyme-based therapy are promising nonresistant strategies for efficiently killing drug-resistant bacteria. However, the poor thermostability of enzymes in PTT hinders their synergistic therapy. Herein, antibacterial glucose oxidase (GOx) is embedded in a Ag graphitic nanocapsule (Ag@G) arrayed silk film to fabricate a GOx-synergistic PTT system (named silk-GOx-Ag@G, SGA). The SGA system can stabilize GOx by a vitrification process through the restriction of hydrogen bond and rigid β-sheet, and keep the antibacterial activity in the hyperthermal PTT environment. Moreover, the arrayed Ag@G possesses excellent chemical stability due to the protection of graphitic shell, providing stable plasmonic effect for integrating PTT and surface enhanced Raman scattering (SERS) analysis even in the GOx-produced H₂ O₂ environment. With in situ SERS identification of bacterial intrinsic signals in the mouse wound model, such SGA realizes superior synergistic antibacterial effect on the infected Escherichia coli, Staphylococcus aureus, and methicillin-resistant Staphylococcus aureus in vivo, while without causing significant biotoxicity. This system provides a therapeutic method with low resistance and in situ diagnosis capability for efficiently eliminating bacteria.

In-situ TiO2-x decoration of titanium carbide MXene for photo/sono-responsive antitumor theranostics

BACKGROUND

Sonodynamic therapy (SDT) has emerged as a noninvasive therapeutic modality that involves sonosensitizers and low-intensity ultrasound. However, owing to the rapid recombination of charge carriers, most of the sonosensitizers triggered poor reactive oxygen species (ROS) generation, resulting in unsatisfactory sonodynamic therapeutic effects.

RESULTS

Herein, a photo/sono-responsive nanoplatform was developed through the in-situ systhesis of TiO2-x on the surface of two-dimensional MXene (titanium carbide, Ti3C2) for photoacoustic/photothermal bimodal imaging-guided near-infrared II (NIR-II) photothermal enhanced SDT of tumor. Because of several oxygen vacancies and smaller size (~ 10 nm), the in-situ formed TiO2-x nanoparticles possessed narrow band gap (2.65 eV) and high surface area, and thus served as a charge trap to restrict charge recombination under ultrasound (US) activation, resulting in enhanced sonodynamic ROS generation. Moreover, Ti3C2 nanosheets induced extensive localized hyperthermia relieves tumor hypoxia by accelerating intratumoral blood flow and tumor oxygenation, and thus further strengthened the efficacy of SDT. Upon US/NIR-II laser dual-stimuli, Ti3C2@TiO2-x nanoplatform triggered substantial cellular killing in vitro and complete tumor eradication in vivo, without any tumor recurrence and systemic toxicity.

CONCLUSION

Our work presents the promising design of photo/sono-responsive nanoplatform for cancer nanotheranostics.

Two birds with one stone: Copper metal-organic framework as a carrier of disulfiram prodrug for cancer therapy

Disulfiram (DSF) has a copper (II)-potentiated anticancer activity in various cancers. Synchronous delivery of DSF and cupric ions to tumor tissues is challenging but holds great potential in improving antitumor outcomes and promoting clinical translation. Herein, we reported a disulfiram prodrug (DQ)-loaded and glucose oxidase (GOD) conjugated copper (II)-based nanoscale metal-organic framework (MOF), MPDG, for tumor-specific, enhanced chemo-chemodynamic therapy. Copper MOF, MOF-199, played a dual role of drug nanocarrier of DQ and copper ion reservoir for sufficient generation of copper (II) diethylthiocarbamate (Cu(DTC)₂), a complex of DSF and Cu²⁺. GOD improved the stability of Cu(II) nano-depot and enabled catalytic generation of H₂O₂ in response to high concentration of glucose in cancer cells. The catalytically generating and endogenous H₂O₂ boosted the activation of encapsulated H₂O₂-activatable prodrug DQ to generate highly cytotoxic Cu(CDTC)₂ in situ for tumor-specific chemotherapy. Meanwhile, the elevated H₂O₂ significantly augmented the production of OH for enhanced chemodynamic therapy. The self-activated amplified chemo-chemodynamic therapy nanosystem led to a significantly enhanced inhibition of 4T1 murine breast cancer cells (half inhibitory concentration reduced from 5 μg/mL to 0.8 μg/mL) in the presence of glucose. The in vivo study verified that MPDG showed the highest tumor inhibition rate of 86.2% and negligible toxicity to main organs. Overall, this study provides a novel disulfiram prodrug/Cu²⁺ co-delivery strategy for enhanced and selective cancer treatment.

Tumor microenvironment responsive self-cascade catalysis for synergistic chemo/chemodynamic therapy by multifunctional biomimetic nanozymes

Chemodynamic therapy (CDT) is an emerging approach to treat cancer based on the tumor microenvironment (TME), but its limited content of endogenous hydrogen peroxide (H₂O₂) weakens the anticancer effects. Herein, a multifunctional biomimetic nanozyme (Se@SiO₂-Mn@Au/DOX, named as SSMA/DOX) is fabricated, which undergoes TME responsive self-cascade catalysis to facilitate MRI guided enhanced chemo/chemodynamic therapy. The SSMA/DOX nanocomposites (NCs) responsively degrade in acidic conditions of tumor to release Se, DOX, Au and Mn²⁺. Mn²⁺ not only enables MRI to guided therapy, but also catalyzes the endogenous H₂O₂ into hydroxyl radical (˙OH) for CDT. In addition, the Au NPs continuously catalyze glucose to generate H₂O₂, enhancing CDT by supplementing a sufficiently reactive material and cutting off the energy supply of the tumor by consuming glucose. Simultaneously, Se enhances the chemotherapy of doxorubicin hydrochloride (DOX) and CDT by upregulating ROS in the tumor cells, achieving remarkable inhibition effect towards tumor. Moreover, SSMA/DOX NCs have good biocompatibility and degradability, which avoid long-term toxicity and side effects. Overall, the degradable SSMA/DOX NCs provide an innovative strategy for tumor microenvironment responsive self-cascade catalysis to enhance tumor therapy.

pH-switchable nanozyme cascade catalysis: a strategy for spatial-temporal modulation of pathological wound microenvironment to rescue stalled healing in diabetic ulcer

The management of diabetic ulcer (DU) to rescue stalled wound healing remains a paramount clinical challenge due to the spatially and temporally coupled pathological wound microenvironment that features hyperglycemia, biofilm infection, hypoxia and excessive oxidative stress. Here we present a pH-switchable nanozyme cascade catalysis (PNCC) strategy for spatial–temporal modulation of pathological wound microenvironment to rescue stalled healing in DU. The PNCC is demonstrated by employing the nanozyme of clinically approved iron oxide nanoparticles coated with a shell of glucose oxidase (Fe₃O₄-GOx). The Fe₃O₄-GOx possesses intrinsic glucose oxidase (GOx), catalase (CAT) and peroxidase (POD)-like activities, and can catalyze pH-switchable glucose-initiated GOx/POD and GOx/CAT cascade reaction in acidic and neutral environment, respectively. Specifically, the GOx/POD cascade reaction generating consecutive fluxes of toxic hydroxyl radical spatially targets the acidic biofilm (pH ~ 5.5), and eradicates biofilm to shorten the inflammatory phase and initiate normal wound healing processes. Furthermore, the GOx/CAT cascade reaction producing consecutive fluxes of oxygen spatially targets the neutral wound tissue, and accelerates the proliferation and remodeling phases of wound healing by addressing the issues of hyperglycemia, hypoxia, and excessive oxidative stress. The shortened inflammatory phase temporally coupled with accelerated proliferation and remodeling phases significantly speed up the normal orchestrated wound-healing cascades. Remarkably, this Fe₃O₄-GOx-instructed spatial–temporal remodeling of DU microenvironment enables complete re-epithelialization of biofilm-infected wound in diabetic mice within 15 days while minimizing toxicity to normal tissues, exerting great transformation potential in clinical DU management. The proposed PNCC concept offers a new perspective for complex pathological microenvironment remodeling, and may provide a powerful modality for the treatment of microenvironment-associated diseases.

Molecular Cloning, Expression, and Enzyme Activity of Glucose Oxidase Gene from Soil Thermophilic Streptomyces

Background

Glucose oxidase is an oxidoreductase that depletes oxygen in food processing and is used in biosensors, glucose diagnostic kits, food processing, cosmetics, and chemical industries. This enzyme is often isolated from fungi, such as Penicillium and Aspergillus Niger.

Objectives

The objective of this study was to clone and express a full-length GOX gene from soil thermophilic streptomyces for bioinformatic and enzyme activity evaluations.

Materials and Methods

After collecting samples from the Gandom Beryan area of Kerman province, Iran, Streptomyces strains were identified with specific biochemical and molecular tests. Streptomyces strains with glucose oxidase gene were detected by PCR, and the amplified gene fragment was cloned into Escherichia coli host bacterium using TA cloning technique. The expression of the cloned GOX gene in the host bacterium was measured using real-time PCR, and the recombinant plasmids were sequenced. The enzymatic activity was measured in the extracts of E. coli cells carrying the plasmids.

Results

After screening the samples, 12 strains of Streptomyces were identified, 4 of which carried the GOX gene. The GOX open reading frame, obtained by PCR, was cloned into a vector and transformed into Escherichia coli origami to generate GOX-producing bacteria. Enzyme activity was confirmed and a phylogenetic tree showed the degree of kinship between Streptomyces species and other species, including Streptomyces SP MI02-7b. The expression levels of GOX genes mRNA were found to be approximately 4-fold higher in transformed E. coli than in soil thermophilic Streptomyces (P <0.001).

Conclusion

This study showed that natural thermostable streptomyces producing glucose oxidase enzyme could be found in Iran. The enzyme gene was successfully transformed into Escherichia coli generating a recombinant host with high yield capability that can be a major step towards the production of this enzyme from indigenous strains. It should be emphasized that the GOX enzyme produced by these strains is profitable due to high production levels correlated to the optimum condition in cheap culture media, short fermentation cycles, high expression capability, and ease of growth.

Combination of phototherapy with immune checkpoint blockade: Theory and practice in cancer

Immune checkpoint blockade (ICB) therapy has evolved as a revolutionized therapeutic modality to eradicate tumor cells by releasing the brake of the antitumor immune response. However, only a subset of patients could benefit from ICB treatment currently. Phototherapy usually includes photothermal therapy (PTT) and photodynamic therapy (PDT). PTT exerts a local therapeutic effect by using photothermal agents to generate heat upon laser irradiation. PDT utilizes irradiated photosensitizers with a laser to produce reactive oxygen species to kill the target cells. Both PTT and PDT can induce immunogenic cell death in tumors to activate antigen-presenting cells and promote T cell infiltration. Therefore, combining ICB treatment with PTT/PDT can enhance the antitumor immune response and prevent tumor metastases and recurrence. In this review, we summarized the mechanism of phototherapy in cancer immunotherapy and discussed the recent advances in the development of phototherapy combined with ICB therapy to treat malignant tumors. Moreover, we also outlined the significant progress of phototherapy combined with targeted therapy or chemotherapy to improve ICB in preclinical and clinical studies. Finally, we analyzed the current challenges of this novel combination treatment regimen. We believe that the next-generation technology breakthrough in cancer treatment may come from this combinational win-win strategy of photoimmunotherapy.

An autophagy-inhibitory MOF nanoreactor for tumor-targeted synergistic therapy

An autophagy-inhibitory metal-organic framework (MOF) nanoreactor was developed for tumor-targeted synergistic therapy. The nanoreactor could inhibit autophagy to enhance the glucose oxidase (GOx)-mediated starvation therapy. And the H2O2 generated in...

Autocatalytic oncotherapy nanosystem with glucose depletion for cascade amplification of hypoxia-activated chemotherapy and H2O2-dependent chemodynamic therapy

Hypoxia-activated prodrug is an appealing oncotherapy strategy, but limited by insufficient tumor hypoxia. Moreover, standalone prodrug fails to treat tumor satisfactorily due to tumor complexity. Herein, a nanosystem (TPZ@FeMSN-GOX) was...

Component-optimized chemo-dynamic nanoagent for enhanced tumour cell-selective chemo-dynamic therapy with minimal side effect in glioma mouse model

Although CuO-deposited bovine serum albumin (CuO-BSA) and glucose oxidase (Gox) were combined to achieve H2O2 self-supplied chemo-dynamic therapy (CDT) and glucose consumption-based starvation therapy, the uses of copper and Gox...

A targeted and efficient CDT system with photocatalytic supplement of H2O2 and hydroxyl radical production at a neutral pH

The bottleneck problems of chemodynamic therapy (CDT) are the dependence on an acidic pH (2.0-4.0), insufficient H2O2 level in tumor tissues and potential systematic toxicity of inorganic nanomaterials-based CDT agents....

Nanocatalyst-Mediated Chemodynamic Tumor Therapy

Traditional tumor treatments, including chemotherapy, radiotherapy, photodynamic therapy, and photothermal therapy, are developed and used to treat different types of cancer. Recently, chemodynamic therapy (CDT) has been emerged as a novel cancer therapeutic strategy. CDT utilizes Fenton or Fenton-like reaction to generate highly cytotoxic hydroxyl radicals (•OH) from endogenous hydrogen peroxide (H₂ O₂ ) to kill cancer cells, which displays promising therapeutic potentials for tumor treatment. However, the low catalytic efficiency and off-target side effects of Fenton reaction limit the biomedical application of CDT. In this regard, various strategies are implemented to potentiate CDT against tumor, including retrofitting the tumor microenvironment (e.g., increasing H₂ O₂ level, decreasing reductive substances, and reducing pH), enhancing the catalytic efficiency of nanocatalysts, and other strategies. This review aims to summarize the development of CDT and summarize these recent progresses of nanocatalyst-mediated CDT for antitumor application. The future development trend and challenges of CDT are also discussed.

A Luminol-Based Self-Illuminating Nanocage as a Reactive Oxygen Species Amplifier to Enhance Deep Tumor Penetration and Synergistic Therapy

The dense extracellular matrix (ECM) in tumor tissues resists drug diffusion into tumors and leads to a poor prognosis. To address this problem, glucose oxidase (GOx)-modified ferritin loaded with luminol-curcumin was fabricated. Once delivered to the tumor, this luminol-based self-illuminating nanocage could actively convert glucose to reactive oxygen species (ROS) to achieve starvation therapy. Then, excessive ROS were transmitted to luminol, thereby emitting 425 nm blue-violet light. Momentarily, light was further absorbed by curcumin and ROS production was amplified. Abundant ROS helps break down the ECM network to penetrate deep into tumors. In addition, ROS produced after cell internalization can induce apoptosis of tumor cells by decreasing the mitochondrial membrane potential and can promote ferroptosis by consuming reduced glutathione. Effective penetration and multiple pathways inducing tumor cell death contributed to the efficient antitumor effect (tumor inhibition rate of GOx-modified ferritin loaded with luminol-curcumin: 71.73%). This study developed a glucose-driven self-illuminating nanocage for active tumor penetration via ROS-mediated destruction of the ECM and provided the synergetic mechanism of apoptosis and ferroptosis.

Triple cascade nanocatalyst with laser-activatable O2 supply and photothermal enhancement for effective catalytic therapy against hypoxic tumor

Nanozymes have been combined with glucose oxidase (GOx) for dual-enzyme cascade catalytic therapy. However, their catalysis efficiency is restricted because of the hypoxia tumor microenvironment (TME). Although many methods are developed for O₂ supply, the O₂ leakage and consumption of H₂O₂ compromised their practical application. Herein, a biocompatible carbon nitride (C₃N₄)/nanozyme/GOx triple cascade nanocatalyst was designed with laser-activatable O₂ self-supply via water splitting to relieve tumor hypoxia and thus improve the catalysis efficiency. To this end, polydopamine (PDA) nanosphere was prepared and attached with C₃N₄ nanosheet to improve water splitting efficiency and realize photothermal-enhanced catalysis, simultaneously. The PDA@C₃N₄ composite was then coated with MIL-100 (Fe), where GOx was loaded, to form C₃N₄/MIL-100/GOx triple cascade nanocatalyst. The triple cascade catalysis was realized with laser-activatable O₂ supply from PDA@C₃N₄, H₂O₂ generation with GOx, and •OH production from peroxidase-like MIL-100 (Fe) for tumor therapy. Upon 808 nm irradiation, PDA, as a photothermal agent, realized photothermal therapy and enhanced the catalytic therapy. Thus, the synergy of laser-activatable O₂ supply and photothermal enhancement in our triple cascade nanocatalyst improved the performance of catalytic therapy without drug resistance and toxicity to normal tissues.

2D antimonene-integrated composite nanomedicine for augmented low-temperature photonic tumor hyperthermia by reversing cell thermoresistance

The overexpression of heat shock proteins (HSPs) in tumor cells can activate inherent defense mechanisms during hyperthermia-based treatments, inducing thermoresistance and thus diminishing the treatment efficacy. Here, we report a distinct "non-inhibitor involvement" strategy to address this issue through engineering a calcium-based nanocatalyst (G/A@CaCO₃-PEG). The constructed nanocatalyst consists of calcium carbonate (CaCO₃)-supported glucose oxidase (GOD) and 2D antimonene quantum dots (AQDs), with further surface modification by lipid bilayers and polyethylene glycol (PEG). The engineered G/A@CaCO₃-PEG nanocatalyst features prolonged blood circulation, which is stable at neutral pH but rapidly degrades under mildly acidic tumor microenvironment, resulting in rapid release of drug cargo in the tumor microenvironment. The integrated GOD effectively catalyzes the depletion of glucose for reducing the supplies of adenosine triphosphate (ATP) and subsequent down-regulation of HSP expression. This effect then augments the therapeutic efficacy of photothermal hyperthermia induced by 2D AQDs upon irradiation with near-infrared light as assisted by reversing the cancer cells' thermoresistance. Consequently, synergistic antineoplastic effects can be achieved via low-temperature photothermal therapy. Systematic in vitro and in vivo evaluations have demonstrated that G/A@CaCO₃-PEG nanocatalysts feature potent antitumor activity with a high tumor-inhibition rate (83.92%). This work thus paves an effective way for augmenting the hyperthermia-based tumor treatments via restriction of the ATP supply.

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.

Biomimetic Nanomaterials Triggered Ferroptosis for Cancer Theranostics

Ferroptosis, as a recently discovered non-apoptotic programmed cell death with an iron-dependent form, has attracted great attention in the field of cancer nanomedicine. However, many ferroptosis-related nano-inducers encountered unexpected limitations such as immune exposure, low circulation time, and ineffective tumor targeting. Biomimetic nanomaterials possess some unique physicochemical properties which can achieve immune escape and effective tumor targeting. Especially, certain components of biomimetic nanomaterials can further enhance ferroptosis. Therefore, this review will provide a comprehensive overview on recent developments of biomimetic nanomaterials in ferroptosis-related cancer nanomedicine. First, the definition and character of ferroptosis and its current applications associated with chemotherapy, radiotherapy, and immunotherapy for enhancing cancer theranostics were briefly discussed. Subsequently, the advantages and limitations of some representative biomimetic nanomedicines, including biomembranes, proteins, amino acids, polyunsaturated fatty acids, and biomineralization-based ferroptosis nano-inducers, were further spotlighted. This review would therefore help the spectrum of advanced and novice researchers who are interested in this area to quickly zoom in the essential information and glean some provoking ideas to advance this subfield in cancer nanomedicine.

A Versatile Calcium Phosphate Nanogenerator for Tumor Microenvironment-activated Cancer Synergistic Therapy

Gas therapy is an emerging "green" cancer treatment strategy; however, its outcome often restricted by the complexity, diversity, and heterogeneity of tumor. Herein, a tumor targeting and tumor microenvironment-activated calcium phosphate nanotheranostic system (denoted as GCAH) is constructed for effective synergistic cancer starvation/gas therapy. GCAH is obtained by a facile biomineralization strategy using glucose oxidase (GOx) as a biotemplate, followed by loading of l-Arginine (L-Arg) and modification of hyaluronic acid (HA) to allow special selectivity for glycoprotien CD44 overexpressed cancer cells. This nanotheranostic system not only exhausts the glucose nutrients in tumor region by the GOx-triggered glucose oxidation, the generated H₂ O₂ can oxidize L-Arg into NO under acidic tumor microenvironment for enhanced gas therapy. As such, there are significant enhancement effects of starvation therapy and gas therapy through the cascade reactions of GOx and L-Arg, which yields a remarkable synergistic therapeutic effect for 4T1 tumor-bearing mice without discernible toxic side effects.

Cell membrane camouflaged cerium oxide nanocubes for targeting enhanced tumor-selective therapy

Anticancer therapies with profound efficacy but negligible toxicity are a fundamental pursuit that has been made humanly possible through either targeting or tumor-selective therapeutic (TST) approaches. Herein, we developed a targeting-enhanced tumor-selective cancer therapy aimed at integrating the two approaches by preparing cerium oxide (CeO₂) nanocubes with glucose oxidase (GOx) modified on the cube surface and cancer cell membrane (CCM) camouflaged outside. The immune escape and homotypic binding of camouflaged CCM enable targeted delivery of the resultant CeO₂-GOx@CCM nanoparticles mostly into cancer tissue, while its acidic environment (pH < 6.6) activated a cascade reaction, in which the glucose was first catalyzed by GOx into H₂O₂ and then by CeO₂ into highly cytotoxic ˙OH killing cancer cells. In the case of off-targeting, when very few CeO₂-GOx@CCM nanoparticles were accidentally delivered into normal tissue, its neutral pH environment (pH = 7.4) triggered a protective reaction, in which the H₂O₂ generated was catalyzed by CeO₂ into non-toxic H₂O and O₂. Both in vitro and in vivo results demonstrated that this targeting-enhanced TST achieved the most remarkable antitumor performance with negligible toxic side effects.

Conquering the Hypoxia Limitation for Photodynamic Therapy

Photodynamic therapy (PDT) has aroused great research interest in recent years owing to its high spatiotemporal selectivity, minimal invasiveness, and low systemic toxicity. However, due to the hypoxic nature characteristic of many solid tumors, PDT is frequently limited in therapeutic effect. Moreover, the consumption of O₂ during PDT may further aggravate the tumor hypoxic condition, which promotes tumor proliferation, metastasis, and invasion resulting in poor prognosis of treatment. Therefore, numerous efforts have been made to increase the O₂ content in tumor with the goal of enhancing PDT efficacy. Herein, these strategies developed in past decade are comprehensively reviewed to alleviate tumor hypoxia, including 1) delivering exogenous O₂ to tumor directly, 2) generating O₂ in situ, 3) reducing tumor cellular O₂ consumption by inhibiting respiration, 4) regulating the TME, (e.g., normalizing tumor vasculature or disrupting tumor extracellular matrix), and 5) inhibiting the hypoxia-inducible factor 1 (HIF-1) signaling pathway to relieve tumor hypoxia. Additionally, the O₂ -independent Type-I PDT is also discussed as an alternative strategy. By reviewing recent progress, it is hoped that this review will provide innovative perspectives in new nanomaterials designed to combat hypoxia and avoid the associated limitation of PDT.

Manipulating Intratumoral Fenton Chemistry for Enhanced Chemodynamic and Chemodynamic-Synergized Multimodal Therapy

Chemodynamic therapy (CDT) uses the tumor microenvironment-assisted intratumoral Fenton reaction for generating highly toxic hydroxyl free radicals (•OH) to achieve selective tumor treatment. However, the limited intratumoral Fenton reaction efficiency restricts the therapeutic efficacy of CDT. Recent years have witnessed the impressive development of various strategies to increase the efficiency of intratumoral Fenton reaction. The introduction of these reinforcement strategies can dramatically improve the treatment efficiency of CDT and further promote the development of enhanced CDT (ECDT)-based multimodal anticancer treatments. In this review, the authors systematically introduce these reinforcement strategies, from their basic working principles, reinforcement mechanisms to their representative clinical applications. Then, ECDT-based multimodal anticancer therapy is discussed, including how to integrate these emerging Fenton reinforcement strategies for accelerating the development of multimodal anticancer therapy, as well as the synergistic mechanisms of ECDT and other treatment methods. Eventually, future direction and challenges of ECDT and ECDT-based multimodal synergistic therapies are elaborated, highlighting the key scientific problems and unsolved technical bottlenecks to facilitate clinical translation.

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.

Biological protein mediated ferroptotic tumor nanotherapeutics

Ferroptosis, a cell death pathway involving iron-related generation of lipid hydroperoxides for achieving incredible tumor suppression, has reignited the hope of chemotherapy in tumor treatment in the past decade. With extensive research studies, various bioactive proteins and cellular pathways have been demonstrated to regulate the occurrence and development of ferroptosis. The gradually established ferroptotic regulatory network is conducive to find effective proteins from a holistic perspective and guides better designs for future ferroptotic tumor therapies. The first section of this review summarizes the recent advances in ferroptotic regulatory mechanisms of proteins and attempts to clarify their latent function in the ferroptotic regulatory network. Second, the existing protein-mediated ferroptotic tumor nanotherapeutic strategies were reviewed, including the protein-mediated iron supplement, cell membrane transporter inhibition, glutathione peroxidase 4 interference, glutathione depletion, bioenzyme-mediated reactive oxygen species generation, heat shock protein inhibition, and tumor-overexpressed protein-triggered drug release for ferroptotic therapy. Finally, the future expectations and challenges of ferroptotic tumor nanotherapeutics for clinical cancer therapy are highlighted.

Hybrid theranostic microbubbles for ultrasound/photoacoustic imaging guided starvation/low-temperature photothermal/hypoxia-activated synergistic cancer therapy

Constructing a theranostic agent for high-contrast multimodality imaging-guided synergistic therapy with long-term tumor retention and minimum systemic side effects still remains a major challenge. Herein, a hybrid microbubble-based theranostic platform was developed for dual-modality ultrasound (US) and enhanced photoacoustic (PA) imaging-guided synergistic tumor therapy by combining starvation therapy, low-temperature photothermal therapy (PTT), and hypoxia-activated therapy, based on polydopamine (PDA) doped poly(vinyl alcohol) microbubbles loaded with glucose oxidase (GOx) (PDA-PVAMBs@GOx) and hypoxia-activated prodrug (HAP) tirapazamine (TPZ). For dual-modality US/enhanced PA imaging, PDA-PVAMBs provided 6.5-fold amplified PA signals relative to freely dispersed PDA nanoparticles (PDA NPs). For synergistic cancer therapy, oxygen (O₂) carried by PDA-PVAMBs@GOx was first released to promote starvation therapy by loaded GOx. Then, moderate near-infrared (NIR) laser irradiation triggered PTT and improved enzymatic activity of GOx with its optimal activity around 47 °C. Subsequently, GOx-mediated tumor starvation depleted O₂ and exacerbated the hypoxia environment, thereby activating the toxicity of TPZ in the tumor site. Through dual-modality US/PA imaging monitoring, PDA-PVAMBs@GOx with long-term retention (∼7 days) combined with PTT and TPZ significantly inhibited the growth of solid tumors with minimum systemic side effects, which might be a powerful tool for effective tumor treatment.

Pillar[6]arene-Based Supramolecular Nanocatalysts for Synergistically Enhanced Chemodynamic Therapy by the Intracellular Cascade Reaction

Chemodynamic therapy (CDT) based on the intracellular Fenton reaction has become increasingly explored in cancer treatment. However, the mildly acidic tumor microenvironment and the limited amount of intracellular hydrogen peroxide (H₂O₂) will create issues for CDT to perform a sustained and high-efficiency treatment. Therefore, how to selectively reduce the pH value and augment the amount of H₂O₂ in tumor tissues has become the key factor for realizing excellent CDT. Besides, the majority of the reported CDT systems have been constructed from iron-based inorganic or metal-organic framework nanomaterials due to the decisive role of metals in CDT, which restricts the development of CDT. In this study, inspired by the host-guest interactions between pillar[6]arene and ferrocene, a ternary pillar[6]arene-based supramolecular nanocatalyst (GOx@T-NPs) for CDT is reported for the first time. GOx@T-NPs not only exhibited a high-efficiency catalytic ability to convert glucose into hydroxyl radicals (^•OH) and to reduce the pH value inside cancer cells for significant enhancement of the CDT effect, but they also showed sensitive glutathione-induced camptothecin (CPT) prodrug release capacity for further improving the efficiency of CDT. Hence, GOx@NPs possessed excellent ability to synergistically enhance the CDT. Additionally, an antitumor mechanism study showed that the prominent tumor inhibition capacity of GOx@T-NPs was derived from trimodal synergistic interactions of CDT, starvation therapy, and chemotherapy. Moreover, GOx@T-NPs manifested good biocompatibility and tumor selectivity with few side effects in major organs. This work broadens the range of materials available for CDT and demonstrates new developments in pillar[n]arene-based multimodal synergistic treatment systems.

"Four-in-One" Nanozyme and Natural Enzyme Symbiotic System of Cu2-x Se-GOx for Cervical Cancer Therapy

Cervical cancer, as a common malignant tumor of the reproductive system, seriously threatens women's life and health, and is difficult to be cured by traditional treatments, such as surgery, chemotherapy and radiotherapy. Fortunately, tumor microenvironment (TME)-activated catalytic therapy with high efficiency and reduced off-target toxicity has emerged as a novel treatment model. Herein, we designed a "four-in-one" nanozyme and natural enzyme symbiotic system of Cu_2-x Se-GOx for TME-triggered cascaded catalytic enhanced cancer treatment. In response to unique TME, Cu_2-x Se with catalase activity could effectively catalyze over-expressed H₂ O₂ in cancer cells into O₂ . Subsequently, the glucose oxidase (GOx) could deplete intracellular glucose with the assistance of O₂ ; this not only achieves starvation therapy, but also regenerates H₂ O₂ to boost the generation of highly cytotoxic ^. OH due to the peroxidase activity of Cu_2-x Se. Moreover, although the free-radical scavenger glutathione (GSH) is overexpressed in tumor cells, Cu_2-x Se with glutathione oxidase activity could effectively consume GSH for enhanced ROS production. Thus, the "four-in-one" nanozyme@natural enzyme symbiotic system of Cu_2-x Se-GOx could induce significant ROS accumulation at the tumor regions, thus providing a potential approach for the treatment of cervical cancer.

Multifunctional nanoreactors-integrated microneedles for cascade reaction-enhanced cancer therapy

Starvation therapy based on glucose oxidase (GOx) has attracted considerable attention in tumor treatment. However, several shortcomings severely hinder its further applications, including limited therapeutic efficacy, poor enzyme stability, and potential side effects. Herein, a strategy of cascade reaction-enhanced combined therapy based on the oxygen-evolving multifunctional nanoreactors is proposed for tumor therapy. The GOx and catalase (CAT) are immobilized in metal-organic frameworks by biomimetic mineralization to improve their stability via spatial confinement. The GOx can consume glucose, reduce ATP levels, and down-regulate the expression of heat shock proteins, which consequently sensitize tumor cells to indocyanine green-based photothermal therapy. Furthermore, the hydrogen peroxide generated by GOx as well as overexpressed in tumor can be decomposed by CAT and continuously generate oxygen, which further enhance the efficacy of oxygen-dependent starvation therapy and photodynamic therapy. The nanoreactors are directly delivered to the superficial tumor by microneedles, achieving efficient tumor accumulation and dramatically strengthened antitumor efficacy without obvious side effects, which provides a valuable paradigm for the application of cascade reaction-based combined therapy.

Current trends in smart mesoporous silica-based nanovehicles for photoactivated cancer therapy

Photoactivated therapeutic strategies (photothermal therapy and photodynamic therapy), due to the adjusted therapeutic area, time and light dosage, have prevailed for the fight against tumors. Currently, the monotherapy with limited treatment effect and undesired side effects is gradually replaced by multimodal and multifunctional nanosystems. Mesoporous silica nanoparticles (MSNs) with unique physicochemical advantages, such as huge specific surface area, controllable pore size and morphology, functionalized modification, satisfying biocompatibility and biodegradability, are considered as promising candidates for multimodal photoactivated cancer therapy. Excitingly, the innovative nanoplatforms based on the mesoporous silica nanoparticles provide more and more effective treatment strategies and display excellent antitumor potential. Given the rapid development of antitumor strategies based on MSNs, this review summarizes the current progress in MSNs-based photoactivated cancer therapy, mainly consists of (1) photothermal therapy-related theranostics; (2) photodynamic therapy-related theranostics; (3) multimodal synergistic therapy, such as chemo-photothermal-photodynamic therapy, phototherapy-immunotherapy and phototherapy-radio therapy. Based on the limited penetration of irradiation light in photoactivated therapy, the challenges faced by deep-seated tumor therapy are fully discussed, and future clinical translation of MSNs-based photoactivated cancer therapy are highlighted.