Biomineralized MnO2 Nanoplatforms Mediated Delivery of Immune Checkpoint Inhibitors with STING Pathway Activation to Potentiate Cancer Radio-Immunotherapy

Advances in antitumor application of ROS enzyme-mimetic catalysts

The rapid growth of research on enzyme-mimetic catalysts (Enz-Cats) is expected to promote further advances in nanomedicine for biological detection, diagnosis and treatment of disease, especially tumors. ROS-based nanomedicines present fascinating potential in antitumor therapy owing to the rapid development of nanotechnology. In this review, we focus on the applications of Enz-Cats based on ROS in antitumor therapy. Firstly, the definition and category of ROS are introduced, and the key factors enhancing ROS levels are carefully elucidated. Then, the rationally engineered Enz-Cats via different synthetic approaches with high ROS-producing efficiencies are comprehensively discussed. Subsequently, oncotherapy application of Enz-Cats is comprehensively discussed, which integrates diverse synergistic treatment modalities and exhibits high efficiency in ROS generation. Finally, the challenges and future research direction of this field are presented. This review is dedicated to unraveling the enigmas surrounding the interplay of nanomedicine and organisms.

Controlled release of manganese and magnesium ions by microsphere-encapsulated hydrogel enhances cancer immunotherapy

Despite the considerable potential of immune checkpoint blockade (ICB) therapy in treating various cancer types, it faces several challenges, of which the constrained objective response rate and relatively short duration of response observed in patients with cancer are the most important. This study introduces an injectable temperature-sensitive hydrogel, Pluronic F-127 (PF-127)@MnCl2/ alginate microspheres (ALG-MS)@MgCl2, that enhances the therapeutic efficacy of programmed cell death-ligand 1 (PD-L1) in cancer cells. The hydrogel material used in this study facilitated the rapid release of a significant amount of manganese ions (Mn2+) and the gradual and sustained release of magnesium ions (Mg2+) within the tumor microenvironment. This staged release profile promotes an immune microenvironment conducive to the cytotoxicity of CD8+ T cells and natural killer cells, thereby enhancing the efficacy of ICB therapy. Furthermore, the PF-127@MnCl2/ALG-MS@MgCl2 composite hydrogel exhibits the ability to convert drug-resistant tumor ("cold tumor") with a low PD-L1 response to a "hot tumor" with a high PD-L1 response. In summary, the PF-127@MnCl2/ALG-MS@MgCl2 hydrogel manipulates the immune microenvironment through the precise discharge of Mg2+ and Mn2+, thus, augmenting the efficacy of ICB therapy.

Light-Activated In Situ Vaccine with Enhanced Cytotoxic T Lymphocyte Infiltration and Function for Potent Cancer Immunotherapy

In situ cancer vaccination is an attractive strategy that stimulates protective antitumor immunity. Cytotoxic T lymphocytes (CTLs) are major mediators of the adaptive immune defenses, with critical roles in antitumor immune response and establishing immune memory, and are consequently extremely important for in situ vaccines to generate systemic and lasting antitumor efficacy. However, the dense extracellular matrix and hypoxia in solid tumors severely impede the infiltration and function of CTLs, ultimately compromising the efficacy of in situ cancer vaccines. To address this issue, a robust in situ cancer vaccine, Au@MnO2 nanoparticles (AMOPs), based on a gold nanoparticle core coated with a manganese dioxide shell is developed. The AMOPs modulated the unfavorable tumor microenvironment (TME) to restore CTLs infiltration and function and efficiently induced immunogenic cell death. The Mn2+-mediated stimulator of the interferon genes pathway can be activated to further augment the therapeutic efficacy of the AMOPs. Thus, the AMOPs vaccine successfully elicited long-lasting antitumor immunity to considerably inhibit primary, recurrent, and metastatic tumors. This study not only highlights the importance of revitalizing CTLs efficacy against solid tumors but also makes progress toward overcoming TME barriers for sustained antitumor immunity.

Immunogenic Material Vaccine for Cancer Immunotherapy by Structure-Dependent Immune Cell Trafficking and Modulation

Inherently immunogenic materials offer enormous prospects in enhancing vaccine efficacy. However, the understanding and improving material adjuvanticity remain elusive. Herein how the structural presentation of immunopotentiators in a material governs the dynamic dialogue between innate and adaptive immunity for enhanced cancer vaccination is reported. The immunopotentiator manganese into six differing structures that resemble the architectures of two types of pathogens (spherical viruses or rod-like bacteria) is precisely manipulated. The results reveal that innate immune cells accurately sense and respond to the architectures, of which two outperformed material candidates (151 nm hollow spheres and hollow microrods with an aspect ratio of 4.5) show higher competence in creating local proinflammatory environment with promoted innate immune cell influx and stimulation on dendritic cells (DCs). In combination with viral peptides, model proteins, or cell lysate antigens, the outperformed microrod material remarkably primes antigen-specific CD8 cytolytic T cells. In prophylactic and therapeutic regimens, the microrod adjuvanted vaccines display optimal aptitude in tumor suppression in four aggressive murine tumor models, by promoting the infiltration of heterogeneous cytolytic effector cells while decreasing suppressive immunoregulatory populations in tumors. This study demonstrates that a rationally selected architecture of immunogenic materials potentially advances the clinical reality of cancer vaccination.

Biosynthetic MnSe nanobomb with low Mn content activates the cGAS-STING pathway and induces immunogenic cell death to enhance antitumour immunity

Triple-negative breast cancer (TNBC) is a relatively "cold" tumour with low immunogenicity compared to other tumour types. Especially, the immune checkpoint inhibitors to treat metastatic TNBC only shows the modest immune response rates. Here, we used Chlorella vulgaris as a bioreactor to synthesize an efficient nanobomb (Bio-MnSe) aimed at eliciting systemic anti-tumour immune response. Despite possessing extremely low Mn content, Bio-MnSe effectively produced more ROS and activated stronger cGAS-STING signal pathway compared to pure Se nanoparticles and free Mn2+ ions, promoting the infiltration of natural killer (NK) cells, cytotoxic T lymphocytes (CTLs) in tumour, effectively turning "cold" tumour into "hot" tumour, and achieving strong antitumour immunotherapy. Additionally, the use of αPD-L1 as an immune checkpoint antagonist further increased the anti-tumour immune response of Bio-MnSe, resulting in enhanced anti-tumour effects. Doxorubicin (Dox), an immunogenic cell death (ICD) inducer, was combined with Bio-MnSe to form Bio-MnSe@Dox. This Bio-MnSe@Dox not only directly damaged tumour cells and induced tumour ICD but also promoted dendritic cell maturation, cytotoxic T lymphocyte infiltration, and NK cell recruitment, synergistically intensifying anti-tumour immune responses and suppressing tumour relapse and lung metastasis. Collectively, our findings propose an effective strategy for transforming 'cold' tumours to 'hot' ones, thereby advancing the development of anti-tumour immune drugs. STATEMENT OF SIGNIFICANCE: A biogenic MnSe (Bio-MnSe) nanocomposite was synthesized using Chlorella vulgaris as a bioreactor for enhanced immunotherapy of TNBC. Bio-MnSe demonstrated a stronger ability to activate the cGAS-STING signalling pathway and generate more ROS compared to pure Se nanoparticles and free Mn2+ ions. Apoptotic cells induced by Bio-MnSe released a significant amount of interferon, leading to the activation of T and natural killer (NK) cells, ultimately transforming immunologically 'cold' breast tumours to 'hot' tumours and enhancing the tumour's response to immune checkpoint inhibitors. The combination of Bio-MnSe with Dox or αPD-L1 further enhanced the anti-tumour immune response, fostering dendritic cell maturation, infiltration of cytotoxic T lymphocytes, and recruitment of NK cells, thereby enhancing the anti-tumour immunotherapy of TNBC.

Differential reinforcement of cGAS-STING pathway-involved immunotherapy by biomineralized bacterial outer membrane-sensitized EBRT and RNT

Radiotherapy (RT), including external beam radiation therapy (EBRT) and radionuclide therapy (RNT), realizes physical killing of local tumors and activates systemic anti-tumor immunity. However, these effects need to be further strengthened and the difference between EBRT and RNT should be discovered. Herein, bacterial outer membrane (OM) was biomineralized with manganese oxide (MnO2) to obtain OM@MnO2-PEG nanoparticles for enhanced radio-immunotherapy via amplifying EBRT/RNT-induced immunogenic cell death (ICD) and cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) activation. OM@MnO2-PEG can react with H2O2 and then gradually produce O2, Mn2+ and OM fragments in the tumor microenvironment. The relieved tumor hypoxia improves the radio-sensitivity of tumor cells, resulting in enhanced ICD and DNA damage. Mn2+ together with the DNA fragments in the cytoplasm activate the cGAS-STING pathway, further exhibiting a positive role in various aspects of innate immunity and adaptive immunity. Besides, OM fragments promote tumor antigen presentation and anti-tumor macrophages polarization. More importantly, our study reveals that OM@MnO2-PEG-mediated RNT triggers much stronger cGAS-STING pathway-involved immunotherapy than that of EBRT, owing to the duration difference of RT. Therefore, this study develops a powerful sensitizer of radio-immunotherapy and uncovers some differences between EBRT and RNT in the activation of cGAS-STING pathway-related anti-tumor immunity.

Programmed Targeting Pyruvate Metabolism Therapy Amplified Single-Atom Nanozyme-Activated Pyroptosis for Immunotherapy

Increasing cellular immunogenicity and reshaping the immune tumor microenvironment (TME) are crucial for antitumor immunotherapy. Herein, this work develops a novel single-atom nanozyme pyroptosis initiator: UK5099 and pyruvate oxidase (POx)-co-loaded Cu-NS single-atom nanozyme (Cu-NS@UK@POx), that not only trigger pyroptosis through cascade biocatalysis to boost the immunogenicity of tumor cells, but also remodel the immunosuppressive TME by targeting pyruvate metabolism. By replacing N with weakly electronegative S, the original spatial symmetry of the Cu-N4 electron distribution is changed and the enzyme-catalyzed process is effectively regulated. Compared to spatially symmetric Cu-N4 single-atom nanozymes (Cu-N4 SA), the S-doped spatially asymmetric single-atom nanozymes (Cu-NS SA) exhibit stronger oxidase activities, including peroxidase (POD), nicotinamide adenine dinucleotide (NADH) oxidase (NOx), L-cysteine oxidase (LCO), and glutathione oxidase (GSHOx), which can cause enough reactive oxygen species (ROS) storms to trigger pyroptosis. Moreover, the synergistic effect of Cu-NS SA, UK5099, and POx can target pyruvate metabolism, which not only improves the immune TME but also increases the degree of pyroptosis. This study provides a two-pronged treatment strategy that can significantly activate antitumor immunotherapy effects via ROS storms, NADH/glutathione/L-cysteine consumption, pyruvate oxidation, and lactic acid (LA)/ATP depletion, triggering pyroptosis and regulating metabolism. This work provides a broad vision for expanding antitumor immunotherapy.

ATP-Responsive Manganese-Based Bacterial Materials Synergistically Activate the cGAS-STING Pathway for Tumor Immunotherapy

Stimulating the cyclic guanosine monophophate(GMP)-adenosine monophosphate (AMP) synthase (cGAS)-stimulator of interferon genes (STING) pathway is a crucial strategy by which bacteria activate the tumor immune system. However, the limited stimulation capability poses significant challenges in advancing bacterial immunotherapy. Here, an adenosine 5'-triphosphate (ATP)-responsive manganese (Mn)-based bacterial material (E. coli@PDMC-PEG (polyethylene glycol)) is engineered successfully, which exhibits an exceptional ability to synergistically activate the cGAS-STING pathway. In the tumor microenvironment, which is characterized by elevated ATP levels, this biohybrid material degrades, resulting in the release of divalent manganese ions (Mn2+) and subsequent bacteria exposure. This combination synergistically activates the cGAS-STING pathway, as Mn2+ enhances the sensitivity of cGAS to the extracellular DNA (eDNA) secreted by the bacteria. The results of the in vivo experiments demonstrate that the biohybrid materials E. coli@PDMC-PEG and VNP20009@PDMC-PEG effectively inhibit the growth of subcutaneous melanoma in mice and in situ liver cancer in rabbits. Valuable insights for the development of bacteria-based tumor immunotherapy are provided here.

Nanoparticle-mediated immunogenic cell death for cancer immunotherapy

The field of cancer therapy is witnessing the emergence of immunotherapy, an innovative approach that activates the body own immune system to combat cancer. Immunogenic cell death (ICD) has emerged as a prominent research focus in the field of cancer immunotherapy, attracting significant attention in recent years. The activation of ICD can induce the release of damage-associated molecular patterns (DAMPs), such as calreticulin (CRT), adenosine triphosphate (ATP), high mobility group box protein 1 (HMGB1), and heat shock proteins (HSP). Subsequently, this process promotes the maturation of innate immune cells, including dendritic cells (DCs), thereby triggering a T cell-mediated anti-tumor immune response. The activation of the ICD ultimately leads to the development of long-lasting immune responses against tumors. Studies have demonstrated that partial therapeutic approaches, such as chemotherapy with doxorubicin, specific forms of radiotherapy, and phototherapy, can induce the generation of ICD. The main focus of this article is to discuss and review the therapeutic methods triggered by nanoparticles for ICD, while briefly outlining their anti-tumor mechanism. The objective is to provide a comprehensive reference for the widespread application of ICD.

Circulating immunotherapy strategy based on pyroptosis and STING pathway: Mn-loaded paclitaxel prodrug nanoplatform against tumor progression and metastasis

Immunotherapy has emerged as a promising strategy against tumors. However, its efficacy is limited by low immunogenicity, poor antigen presentation, and inadequate lymphocyte infiltration. Herein, we develop a nanoplatform (Mn-HSP) loaded with manganese ions (Mn2+) and paclitaxel (PTX) prodrug based on hyaluronic acid. PTX in Mn-HSP induces DNA damage and pyroptosis to release tumor-associated antigens (TAAs), enhancing tumor-specific adaptive immunity. Meanwhile, Mn2+ in Mn-HSP, together with PTX-induced DNA damage, activates the stimulator of interferon gene (STING) pathway to amplify innate immunity. Mn-HSP combines with adaptive and innate immunity, effectively enhancing the presentation of antigen-presenting cells (APCs) and promoting tumor infiltration of cytotoxic T lymphocytes (CTLs). In turn, the granzyme B (GZMB) secreted by CTLs triggers pyroptosis again, thereby establishing a "circulating immunotherapy" against tumors. Our results demonstrate that Mn-HSP efficiently inhibits primary breast tumors, as well as rechallenge tumors and lung metastasis in vivo. Therefore, the circulating immunotherapy that combines pyroptosis mediated adaptive immunity and STING pathway amplified innate immunity provides a novel strategy for enhancing tumor immunotherapy.

Metal nanoparticles for cancer therapy: Precision targeting of DNA damage

Cancer, a complex and heterogeneous disease, arises from genomic instability. Currently, DNA damage-based cancer treatments, including radiotherapy and chemotherapy, are employed in clinical practice. However, the efficacy and safety of these therapies are constrained by various factors, limiting their ability to meet current clinical demands. Metal nanoparticles present promising avenues for enhancing each critical aspect of DNA damage-based cancer therapy. Their customizable physicochemical properties enable the development of targeted and personalized treatment platforms. In this review, we delve into the design principles and optimization strategies of metal nanoparticles. We shed light on the limitations of DNA damage-based therapy while highlighting the diverse strategies made possible by metal nanoparticles. These encompass targeted drug delivery, inhibition of DNA repair mechanisms, induction of cell death, and the cascading immune response. Moreover, we explore the pivotal role of physicochemical factors such as nanoparticle size, stimuli-responsiveness, and surface modification in shaping metal nanoparticle platforms. Finally, we present insights into the challenges and future directions of metal nanoparticles in advancing DNA damage-based cancer therapy, paving the way for novel treatment paradigms.

Ultrathin Clay Nanoparticles-Mediated Mutual Reinforcement of Ferroptosis and Cancer Immunotherapy

Ferroptosis-triggered immunogenic cell death (ICD) is widely adopted to potentiate the body's antitumor immunity by catalyzing the production of toxic reactive oxygen species (ROS). However, the efficacy of ferroptosis and immunotherapy is greatly restricted by intracellular abundant glutathione (GSH) and immunosuppressive tumor microenvironment (TME). Herein, a facile bottom-up method for solvent-free synthesis of ultrathin manganese (Mn)-based layered double hydroxide nanosheets with high loading efficiency for pro-inflammatory cytokine interferon (IFNγ) (IFNγ/uMn-LDHs) is proposed to mutually reinforce the ferroptosis and systemic immunity. The introduction of manganese ions significantly contributes to GSH depletion and hydroxyl radical generation, which can be further enhanced by IFNγ delivery-induced SLC7A11 downregulation. The ICD effect after cell ferroptosis cooperates with the intrinsic immunomodulatory property of IFNγ/uMn-LDHs to facilitate the maturation of dendritic cells (DCs) and the priming of T cells. IFNγ secretion from activated CD8+ T cells in turn involves cascade immunogenic ferroptosis, thus constructing a closed-loop therapy. Remarkably, a potent abscopal effect is observed in the growth inhibition of both primary and distant tumors. Overall, the ultrathin Mn-based clay nanoplatform provides a simple approach for mutual regulation between ferroptosis and antitumor immune response, overcoming the obstacles of current cancer immunotherapy.

Manganese Dioxide Nanoplatform with a Hollow Rhombic Dodecahedron Morphology for Drug Delivery

Manganese dioxide (MnO2) is considered as a promising drug carrier material suitable for the tumor microenvironment while lacking conducive structures for drug loading. Herein, we construct a MnO2 nanoplatform with a hollow rhombic dodecahedral morphology for drug delivery. In this work, we obtained zeolitic imidazolate framework nanoparticles (ZIF-90 NPs) via a coordination reaction. Furthermore, the drug-loading nanoparticles (ZIF-90/DOX NPs) were obtained by Schiff's base reaction and then selected as a sacrificial template to obtain the hollow nanoplatforms (ZIF-90@MnO2 NPs). Moreover, the photothermal effect and multiresponsive drug release behaviors were revealed by loading the photothermal agent IR-820 and the anticancer drug doxorubicin hydrochloride (DOX). Our study demonstrates that the ZIF-90@MnO2 NPs loaded with photosensitizers exhibited excellent photothermal conversion performance. Benefiting from the hollow structure and redox activity, remarkable drug loading and release performances of ZIF-90@MnO2 NPs were achieved. It is shown that ZIF-90@MnO2 NPs achieved a satisfactory drug-loading efficiency (up to ca. 69.7%) for DOX. More promisingly, the ZIF-90@MnO2 NPs exhibited significant glutathione (GSH)/pH-responsive drug release and degradation performances. Overall, this work highlights the potential of controlled drug release of nanocarriers and offers unique insights into the design of nanocarriers with hollow structures.

STING Agonist-Loaded Nanoparticles Promotes Positive Regulation of Type I Interferon-Dependent Radioimmunotherapy in Rectal Cancer

Hypoxia-associated radioresistance in rectal cancer (RC) has severely hampered the response to radioimmunotherapy (iRT), necessitating innovative strategies to enhance RC radiosensitivity and improve iRT efficacy. Here, a catalytic radiosensitizer, DMPtNPS, and a STING agonist, cGAMP, are integrated to overcome RC radioresistance and enhance iRT. DMPtNPS promotes efficient X-ray energy transfer to generate reactive oxygen species, while alleviating hypoxia within tumors, thereby increasing radiosensitivity. Mechanistically, the transcriptomic and immunoassay analysis reveal that the combination of DMPtNPS and RT provokes bidirectional regulatory effects on the immune response, which may potentially reduce the antitumor efficacy. To mitigate this, cGAMP is loaded into DMPtNPS to reverse the negative impact of DMPtNPS and RT on the tumor immune microenvironment (TiME) through the type I interferon-dependent pathway, which promotes cancer immunotherapy. In a bilateral tumor model, the combination treatment of RT, DMPtNPS@cGAMP, and αPD-1 demonstrates a durable complete response at the primary site and enhanced abscopal effect at the distant site. This study highlights the critical role of incorporating catalytic radiosensitizers and STING agonists into the iRT approach for RC.

Nanomaterial-encapsulated STING agonists for immune modulation in cancer therapy

The cGAS-STING signaling pathway has emerged as a critical mediator of innate immune responses, playing a crucial role in improving antitumor immunity through immune effector responses. Targeting the cGAS-STING pathway holds promise for overcoming immunosuppressive tumor microenvironments (TME) and promoting effective tumor elimination. However, systemic administration of current STING agonists faces challenges related to low bioavailability and potential adverse effects, thus limiting their clinical applicability. Recently, nanotechnology-based strategies have been developed to modulate TMEs for robust immunotherapeutic responses. The encapsulation and delivery of STING agonists within nanoparticles (STING-NPs) present an attractive avenue for antitumor immunotherapy. This review explores a range of nanoparticles designed to encapsulate STING agonists, highlighting their benefits, including favorable biocompatibility, improved tumor penetration, and efficient intracellular delivery of STING agonists. The review also summarizes the immunomodulatory impacts of STING-NPs on the TME, including enhanced secretion of pro-inflammatory cytokines and chemokines, dendritic cell activation, cytotoxic T cell priming, macrophage re-education, and vasculature normalization. Furthermore, the review offers insights into co-delivered nanoplatforms involving STING agonists alongside antitumor agents such as chemotherapeutic compounds, immune checkpoint inhibitors, antigen peptides, and other immune adjuvants. These platforms demonstrate remarkable versatility in inducing immunogenic responses within the TME, ultimately amplifying the potential for antitumor immunotherapy.

Metal-Organic Framework-Based Nano-Activators Facilitating Microwave Combined Therapy via a Divide-and-Conquer Tactic for Triple-Negative Breast Cancer

Aiming at the clinical problems of high recurrence and metastasis rate of triple-negative breast cancer, a divide-and-conquer tactic is developed. The designed nanoactivators enhance microwave thermo-dynamic-chemotherapy to efficiently kill primary tumors, simultaneously ameliorate the immunosuppressive microenvironment, activate the tumor infiltration of T lymphocytes, and enhance the accumulation and penetration of PD-1/PD-L1 immune agents, ultimately boosting the efficacy of immune checkpoint blocking therapy to achieve efficient inhibition of distal tumors and metastases. Metal-organic framework (MOF)-based MPPT nano-activator is synthesized by packaging chemotherapeutic drug Pyrotinib and immunosuppressant PD-1/PD-L1 inhibitor 2 into MnCa-MOF and then coupling target molecule triphenylphosphine, which significantly improved the accumulation and penetration of Pyrotinib and immunosuppressant in tumors. In addition to the combined treatment of microwave thermo-dynamic-chemotherapy under microwave irradiation, Mn2+ in the nano-activator comprehensively promotes the cGAS-STING pathway to activate innate immunity, microwave therapy, and hypoxia relief are combined to ameliorate the tumor immunosuppressive microenvironment. The released Pyrotinib down-regulates epidermal growth factor receptor and its downstream pathways PI3K/AKT/mTOR and MAPK/ERK signaling pathways to maximize the therapeutic effect of immune checkpoint blocking, which helps to enhance the antitumor efficacy and promote long-term memory immunity. This nano-activator offers a generally promising paradigm for existing clinical triple-negative breast cancer treatment through a divide-and-conquer strategy.

Advanced Generation Therapeutics: Biomimetic Nanodelivery System for Tumor Immunotherapy

Tumor immunotherapy is a safe and effective strategy for precision medicine. However, immunotherapy for most cancer cases still ends in failure, with the root causes of the immunosuppressive and extraordinary heterogeneity of the solid tumors microenvironment. The emerging biomimetic nanodelivery system provides a promising tactic to improve the immunotherapy effect while reducing the adverse reactions on nontarget cells. Herein, we summarize the relationship between tumor occurrence and tumor immune microenvironment, mechanism of tumor immune escape, immunotherapy classification (including adoptive cellular therapy, cytokines, cancer vaccines, and immune checkpoint inhibitors) and recommend target cells for immunotherapy first, and then emphatically introduce the recent advances and applications of the latest biomimetic nanodelivery systems (e.g., immune cells, erythrocytes, tumor cells, platelets, bacteria) in tumor immunotherapy. Meanwhile, we separately summarize the application of tumor vaccines. Finally, the predictable challenges and perspectives in a forward exploration of biomimetic nanodelivery systems for tumor immunotherapy are also discussed.

Tumor Microenvironment-Specific Driven Nanoagents for Synergistic Mitochondria Damage-Related Immunogenic Cell Death and Alleviated Immunosuppression

Despite significant breakthroughs in immunotherapy, the limitations of inadequate immune stimulation and stubborn immune resistance continue to present opportunities and challenges. Therefore, a two-pronged approach, encompassing the activation of immunogenic cell death (ICD) and blocking the indoleamine 2,3-dioxygenase (IDO)-mediated pathway, is devised to elicit systemic anti-tumor immunity and alleviate immunosuppression. Herein, a tumor microenvironment (TME)-specific driven nanoagent is composed of a tetrasulfide bond-bridged mesoporous silica layer (MON) coated up-conversion nanoparticles as a nano-carrier, combines Fe2+ , curcumin, and indoximod for operating chemodynamic therapy/chemotherapy/immunotherapy. The consumption of glutathione (GSH) caused by MON degradation, the Fenton reaction of Fe2+ , and curcumin triggering mitochondrial damage collectively exacerbate the oxidative stress, leading to a violent immunoreaction and reversal of the immunosuppressive TME through a combination of IDO-inhibitors. Meanwhile, upconversion luminescence (UCL) imaging serves as a significant guiding tool for drug delivery and the treatment of nanoagents. In vivo and in vitro experiment results demonstrate that the nanosystem not only effectively inhibits the growth of primary tumors but also induces immune priming and memory effects to reject re-challenged tumors. The strategy as a complementary approach displays great potential for future immunotherapy along with other multimodal treatment modes.

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.

Ultrasmall PtMn nanoparticles as sensitive manganese release modulator for specificity cancer theranostics

Manganese-based nanomaterials (Mn-nanomaterials) hold immense potential in cancer diagnosis and therapies. However, most Mn-nanomaterials are limited by the low sensitivity and low efficiency toward mild weak acidity (pH 6.4-6.8) of the tumor microenvironment, resulting in unsatisfactory therapeutic effect and poor magnetic resonance imaging (MRI) performance. This study introduces pH-ultrasensitive PtMn nanoparticles as a novel platform for enhanced ferroptosis-based cancer theranostics. The PtMn nanoparticles were synthesized with different diameters from 5.3 to 2.7 nm with size-dominant catalytic activity and magnetic relaxation, and modified with an acidity-responsive polymer to create pH-sensitive agents. Importantly, R-PtMn-1 (3 nm core) presents "turn-on" oxidase-like activity, affording a significant enhancement ratio (pH 6.0/pH 7.4) in catalytic activity (6.7 folds), compared with R-PtMn-2 (4.2 nm core, 3.7 folds) or R-PtMn-3 (5.3 nm core, 2.1 folds), respectively. Moreover, R-PtMn-1 exhibits dual-mode contrast in high-field MRI. R-PtMn-1 possesses a good enhancement ratio (pH 6.4/pH 7.4) that is 3 or 3.2 folds for T1- or T2-MRI, respectively, which is higher than that of R-PtMn-2 (1.4 or 1.5 folds) or R-PtMn-3 (1.1 or 1.2 folds). Moreover, their pH-ultrasensitivity enabled activation specifically within the tumor microenvironment, avoiding off-target toxicity in normal tissues during delivery. In vitro studies demonstrated elevated intracellular reactive oxygen species production, lipid peroxidation, mitochondrial membrane potential changes, malondialdehyde content, and glutathione depletion, leading to enhanced ferroptosis in cancer cells. Meanwhile, normal cells remained unaffected by the nanoparticles. Overall, the pH-ultrasensitive PtMn nanoparticles offer a promising strategy for accurate cancer diagnosis and ferroptosis-based therapy.

Radiotherapy combined with nano-biomaterials for cancer radio-immunotherapy

Radiotherapy (RT) plays an important role in tumor therapy due to its noninvasiveness and wide adaptation. In recent years, radiation therapy has been discovered to induce an anti-tumor immune response, which arouses widespread concern among scientists and clinicians. In this review, we highlight recent advances in the applications of nano-biomaterials for radiotherapy-activated immunotherapy. We first discuss the combination of different radiosensitizing nano-biomaterials and immune checkpoint inhibitors to enhance tumor immune response and improve radiotherapy efficacy. Subsequently, various nano-biomaterials-enabled tumor oxygenation strategies are introduced to alleviate the hypoxic tumor environment and amplify the immunomodulatory effect. With the aid of nano-vaccines and adjuvants, radiotherapy refreshes the host's immune system. Additionally, ionizing radiation responsive nano-biomaterials raise innate immunity-mediated anti-tumor immunity. At last, we summarize the rapid development of immune modulatable nano-biomaterials and discuss the key challenge in the development of nano-biomaterials for tumor radio-immunotherapy. Understanding the nano-biomaterials-assisted radio-immunotherapy will maximize the benefits of clinical radiotherapy and immunotherapy and facilitate the development of new combinational therapy modality.

Manganese-Based Nanotheranostics for Magnetic Resonance Imaging-Mediated Precise Cancer Management

Manganese (Mn)-based magnetic resonance imaging (MRI) has become a competitive imaging modality for cancer diagnosis due to its advantages of non-invasiveness, high resolution and excellent biocompatibility. In recent years, a variety of Mn contrast agents based on different material systems have been synthesized, and a series of multi-purpose Mn nanocomposites have also emerged, showing satisfactory relaxation efficiency and MRI performance thus possess the transformation and application value in MRI-synergized cancer diagnosis and treatment. This tutorial review starts from the classification and properties of Mn-based nanomaterials, and then summarizes various preparation and functionalization strategies of nanosized Mn contrast agents, especially focuses on the latest progress of Mn contrast agents in MRI-synergized precise cancer theranostics. In addition, present review also discusses the current clinical transformation obstacles such as unclear molecular mechanisms, potential nanotoxicity, and scale production constraints. This paper provides evidence-based recommendations about the future prospects of multifunctional nanoplatforms, as well as technical guidance and panoramic expectations for the design of clinically meaningful cancer management programs.

In situ hypoxia modulating nano-catalase for amplifying DNA damage in radiation resistive colon tumors

Radiation therapy (RT) is a mainstream clinical approach in cancer treatment. However, the therapeutic efficacy of RT is greatly hindered by the presence of excessive hydrogen peroxide (H2O2) in the hypoxic region of the solid tumor, thus leading to tumor recurrence and metastasis. Herein, a thioketal-linked amphiphilic nano-assembly (MTS) loaded with hydrophobic manganese oxide (HMO) nanoparticles (MTS@HMO) is examined as a promising multi-purpose reactive oxygen species (ROS)-catalytic nanozyme for transforming an RT-resistant hypoxic tumor microenvironment (TME) into an RT-susceptible one by scavenging ROS in the hypoxic core of the solid tumor. After intravenous injection, the MTS@HMO nano-assembly was able to sense and be degraded by the abundant ROS in the hypoxic TME, thereby releasing HMO particles for subsequent scavenging of H2O2. The oxygen generated during peroxide scavenging then relieved the hypoxic TME, thereby resulting in an increased sensitivity of the hypoxic tumor tissue towards RT. Moreover, the in situ hypoxic status was monitored via the T1-enhanced magnetic resonance (MR) imaging of the Mn2+ ions generated by the ROS-mediated degradation of HMO. The in vitro results demonstrated a significant H2O2 elimination and enhanced oxygen generation after the treatment of the MTS@HMO nano-assembly with tumor cells under hypoxic conditions, compared to the control MTS group. In addition, the combination of RT and pre-treatment with MTS@HMO nano-assembly significantly amplified the permanent DNA strand breaks in tumor cells compared to the control RT group. More importantly, the in vivo results proved that the systemic injection of the MTS@HMO nano-assembly prior to RT irradiation enhanced the RT-mediated tumor suppression and down-regulated the hypoxic marker of HIF-1α in the solid tumor compared to the control RT group. Overall, the present work demonstrates the great potential of the versatile ROS-catalytic hypoxia modulating strategy using the MTS@HMO nano-assembly to enhance the RT-induced antitumor efficacy in hypoxic solid tumors.

Escherichia coli-Based In Situ Triggerable Probe as an Amplifier for Sensitive Diagnosis and Penetrated Therapy of Cancer

Escherichia coli (E. coli) was used for cancer therapy due to the tumor-targeting, catalytic, and surface-reducing properties. Effective diagnosis combined with treatment of cancer based on E. coli, however, was rarely demonstrated. In this study, E. coli was used to surface reduce HAuCl4 and as a carrier to modify riboflavin (Rf) and luminol (E-Au@Rf@Lum). After targeted delivery to tumor, the E-Au@Rf@Lum probe could actively emit 425 nm blue-violet chemiluminescence (CL) to achieve cell imaging for cancer diagnosis. Furthermore, this light could in situ trigger the photosensitizer (Rf) through CL resonance energy transfer, which produces reactive oxygen species (ROS) for accurate photodynamic therapy. In return, the excessive ROS enhanced the blue-violet light which was further absorbed by Rf, and ROS production was cyclically amplified. Abundant ROS broke down the dense extracellular matrix network and penetrated deep into tumors. Besides, E. coli with excellent catalytic property could decompose H2O2 to O2 to relieve tumor hypoxia for a long time and enhance the photosensitized process of Rf. By self-illumination, effective penetration, and tumor hypoxia relief, this work opens a self-amplified therapy modality to tumor.

Cancer Stem-Like Cells-Oriented Surface Self-Assembly to Conquer Radioresistance

Cancer stem-like cells (CSCs), capable of indefinite self-renewal and differentiation, are considered to be the root cause of tumor radiotherapy (RT) resistance. However, the CSCs-targeted therapy still remains to be a great challenge because they are commonly located in the deep tumor making drugs hard to approach, and their hypoxic and acidic niche can further aggravate radioresistance. Herein, based on the finding that hypoxic CSCs highly express carbonic anhydrase IX (CAIX) on the cell membrane, a CAIX-targeted induced in situ self-assembly system on the surface of CSC is reported to overcome hypoxic CSC-mediated radioresistance. Via the sequential processes of "monomer release-target accumulation-surface self-assembly", the constructed peptide-based drug delivery system (CA-Pt) exhibits the advantages of deep penetration, amplified CAIX inhibition, and enhanced cellular uptake, which greatly relieves the hypoxic and acidic microenvironment to promote the hypoxic CSC differentiation and combines with platinum to boost the RT-inducing DNA damage. In both lung cancer tumor mouse and zebrafish embryo models, CA-Pt treatment can effectively assist RT in suppressing tumor growth and preventing tumor invasion and metastasis. This study uses a surface-induced self-assembly strategy to differentiate hypoxic CSCs, which may provide a universal treatment strategy for overcoming tumor radioresistance.

Nanotechnology-Assisted Immunogenic Cell Death for Effective Cancer Immunotherapy

Tumor vaccines have been used to treat cancer. How to efficiently induce tumor-associated antigens (TAAs) secretion with host immune system activation is a key issue in achieving high antitumor immunity. Immunogenic cell death (ICD) is a process in which tumor cells upon an external stimulus change from non-immunogenic to immunogenic, leading to enhanced antitumor immune responses. The immune properties of ICD are damage-associated molecular patterns and TAA secretion, which can further promote dendritic cell maturation and antigen presentation to T cells for adaptive immune response provocation. In this review, we mainly summarize the latest studies focusing on nanotechnology-mediated ICD for effective cancer immunotherapy as well as point out the challenges.