Engineering biomimetic nanosystem targeting multiple tumor radioresistance hallmarks for enhanced radiotherapy

Tumor cells establish a robust self-defense system characterized by hypoxia, antioxidant overexpression, DNA damage repair, and so forth to resist radiotherapy. Targeting one of these features is insufficient to overcome radioresistance due to the feedback mechanisms initiated by tumor cells under radiotherapy. Therefore, we herein developed an engineering biomimetic nanosystem (M@HHPt) masked with tumor cell membranes and loaded with a hybridized protein-based nanoparticle carrying oxygens (O2) and cisplatin prodrugs (Pt(IV)) to target multiple tumor radioresistance hallmarks for enhanced radiotherapy. After administration, M@HHPt actively targeted and smoothly accumulated in tumor cells by virtue of its innate homing abilities to realize efficient co-delivery of O2 and Pt(IV). O2 introduction induced hypoxia alleviation cooperated with Pt(IV) reduction caused glutathione consumption greatly amplified radiotherapy-ignited cellular oxidative stress. Moreover, the released cisplatin effectively hindered DNA damage repair by crosslinking with radiotherapy-produced DNA fragments. Consequently, M@HHPt-sensitized radiotherapy significantly suppressed the proliferation of lung cancer H1975 cells with an extremely high sensitizer enhancement ratio of 1.91 and the progression of H1975 tumor models with an excellent tumor inhibition rate of 94.7%. Overall, this work provided a feasible strategy for tumor radiosensitization by overcoming multiple radioresistance mechanisms.

Biosynthesis of NIR-II Ag2 Se Quantum Dots with Bacterial Catalase for Photoacoustic Imaging and Alleviating-Hypoxia Photothermal Therapy

Developing the second near-infrared (NIR-II) photoacoustic (PA) agent is of great interest in bioimaging. Ag2 Se quantum dots (QDs) are one kind of potential probe for applications in NIR-II photoacoustic imaging (PAI). However, the surfaces with excess anions of Ag2 Se QDs, which increase the probability of nonradiative transitions of excitons benefiting PA imaging, are not conducive to binding electron donor ligands for potential biolabeling and imaging. In this study, Staphylococcus aureus (S. aureus) cells are driven for the biosynthesis of Ag2 Se QDs with catalase (CAT). Biosynthesized Ag2 Se (bio-Ag2 Se-CAT) QDs are produced in Se-enriched environment of S. aureus and have a high Se-rich surface. The photothermal conversion efficiency of bio-Ag2 Se-CAT QDs at 808 and 1064 nm is calculated as 75.3% and 51.7%, respectively. Additionally, the PA signal responsiveness of bio-Ag2 Se-CAT QDs is ≈10 times that of the commercial PA contrast agent indocyanine green. In particular, the bacterial CAT is naturally attached to bio-Ag2 Se-CAT QDs surface, which can effectively relieve tumor hypoxia. The bio-Ag2 Se-CAT QDs can relieve heat-initiated oxidative stress while undergoing effective photothermal therapy (PTT). Such biosynthesis method of NIR-II bio-Ag2 Se-CAT QDs opens a new avenue for developing multifunctional nanomaterials, showing great promise for PAI, hypoxia alleviation, and PTT.

Tumor microenvironment-responsive delivery nanosystems reverse immunosuppression for enhanced CO gas/immunotherapy

Carbon monoxide (CO) gas therapy demonstrates great potential to induce cancer cell apoptosis and antitumor immune responses, which exhibits tremendous potential in cancer treatment. However, the therapeutic efficacy of CO therapy is inhibited by the immunosuppressive tumor microenvironment (TME). Herein, a facile strategy is proposed to construct hollow-structured rough nanoplatforms to boost antitumor immunity and simultaneously reverse immunosuppression by exploring intrinsic immunomodulatory properties and morphological optimization of nanomaterials. The TME-responsive delivery nanosystems (M-RMH) are developed by encapsulating the CO prodrug within hollow rough MnO2 nanoparticles and the subsequent surface functionalization with hyaluronic acid (HA). Rough surfaces are designed to facilitate the intrinsic properties of HA-functionalized MnO2 nanoparticles (RMH) to induce dendritic cell maturation and M1 macrophage polarization by STING pathway activation and hypoxia alleviation through enhanced cellular uptake. After TME-responsive degradation of RMH, controlled release of CO is triggered at the tumor site for CO therapy to activate antitumor immunity. More importantly, RMH could modulate immunosuppressive TME by hypoxia alleviation. After the combination with aPD-L1-mediated checkpoint blockade therapy, robust antitumor immune responses are found to inhibit both primary and distant tumors. This work provides a facile strategy to construct superior delivery nanosystems for enhanced CO/immunotherapy through efficient activation of antitumor immune responses and reversal of immunosuppression.

Recent Advances in Nanoplatform Construction Strategy for Alleviating Tumor Hypoxia

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

Melanin-Based Immunoregulatory Nanohybrids Enhance Antitumor Immune Responses in Breast Cancer Mouse Model

Natural melanin nanoparticles (MNPs) have demonstrated a potential for eliciting antitumor immune responses through inducing immunogenic cell death (ICD); however, the tumor microenvironment (TME) has been shown to inhibit T cell-mediated antitumor immunity. To address this challenge, we designed TME-responsive biodegradable melanin/MnO_x nanohybrids via a biomineralization process. Under near-infrared (NIR) light irradiation, the photothermal property of melanin/MnO_x nanohybrids triggers ICD and release of tumor-associated antigens (TAAs), while Mn²⁺ and TAAs induce dendritic cell (DC) maturation to provoke immune responses. Furthermore, the immunoregulatory properties of the nanohybrids themselves are exploited to reshape immunosuppressive TME and downregulate PD-L1 through alleviation of the hypoxic and acidic TME. Although MNPs demonstrate higher photothermal killing efficiency than the nanohybrids in vitro due to their superior photothermal effect, the melanin/MnO_x nanohybrids exhibit significantly enhanced antitumor and antimetastatic effects in vivo, benefiting from their ability to reverse immunosuppression and induce DC maturation. Transcriptomics analysis confirmed the successful activation of immune responses. This work presents a promising approach for immunomodulation-enhanced cancer therapy through the intrinsic properties of melanin/MnO_x nanohybrids.

Molecularly Self-Engineered Nanoamplifier for Boosting Photodynamic Therapy via Cascade Oxygen Elevation and Lipid ROS Accumulation

Photodynamic therapy (PDT) has been extensively explored as a noninvasive cancer treatment modality. However, the dilemma of tumor hypoxia and short half-life of singlet oxygen (¹O₂) severely restrict the therapeutic efficacy of PDT. Herein, we develop a facile three-in-one PDT nanoamplifier (AA@PPa/Hemin NPs) assembled by pyropheophorbide a (PPa), hemin, and arachidonic acid (AA). Interestingly, AA not only acts as an enabler to facilitate the assembly of PPa and hemin in the construction of ternary hybrid nanoassemblies but also acts as a lipid reactive oxygen species (ROS) amplifier for robust PDT. In tumor cells, hemin plays the role of a catalase-like catalyst that accelerates the production of oxygen (O₂) from hydrogen peroxide (H₂O₂), significantly alleviating tumor hypoxia. Under laser irradiation, vast amounts of ¹O₂ generated by PPa trigger the peroxidation of AA to produce large amounts of cytotoxic lipid ROS, immensely amplifying the efficiency of PDT by promptly eliciting cellular oxidative stress. As expected, AA@PPa/Hemin NPs exert potent antitumor activity in a 4T1 breast-tumor-bearing BALB/c mice xenograft model. Such a cascade nanohybrid amplifier provides a novel codelivery platform for accurate and effective PDT of cancer.

A Porous Bimetallic Au@Pt Core-Shell Oxygen Generator to Enhance Hypoxia-Dampened Tumor Chemotherapy Synergized with NIR-II Photothermal Therapy

The characteristic hypoxia of solid tumors and inadequate oxygen supply become a key causation of the resistance to chemotherapy in cancer treatment. Herein, a bimetallic oxygen nanogenerator, i.e., porous Au@Pt core-shell nanostructures, is particularly developed to reduce the multidrug resistance by oxygenating the tumor along with synergistic chemo-photothermal therapy for efficient tumor eradication. The porous platinum (Pt) shell was able to catalyze oxygen generation from endogenous hydrogen peroxide in the tumor, reducing the exocytosis of doxorubicin (DOX) via suppressed expression of hypoxia-inducible factor-1α, multidrug resistance gene 1, and P-glycoprotein. The strong absorbance of Au@Pt nanostructures in NIR window II enabled NIR-II photothermal therapy. Further incorporation of DOX into the mesopores of Au@Pt nanostructures with the assistance of phase change materials (PCM) led to the formulation of Au@Pt-DOX-PCM-PEG nanotherapeutics for NIR-II-activated chemotherapy. This work presents an efficient H₂O₂-driven oxygenerator for enhanced hypoxia-dampened chemotherapy and NIR-II photothermal therapy.

Ultrasmall Manganese Ferrites for In Vivo Catalase Mimicking Activity and Multimodal Bioimaging

Manganese ferrite nanoparticles display interesting features in bioimaging and catalytic therapies. They have been recently used in theranostics as contrast agents in magnetic resonance imaging (MRI), and as catalase-mimicking nanozymes for hypoxia alleviation. These promising applications encourage the development of novel synthetic procedures to enhance the bioimaging and catalytic properties of these nanomaterials simultaneously. Herein, a cost-efficient synthetic microwave method is developed to manufacture ultrasmall manganese ferrite nanoparticles as advanced multimodal contrast agents in MRI and positron emission tomography (PET), and improved nanozymes. Such a synthetic method allows doping ferrites with Mn in a wide stoichiometric range (Mn_x Fe_3-x O₄ , 0.1 ≤ x ≤ 2.4), affording a library of nanoparticles with different magnetic relaxivities and catalytic properties. These tuned magnetic properties give rise to either positive or dual-mode MRI contrast agents. On the other hand, higher levels of Mn doping enhance the catalytic efficiency of the resulting nanozymes. Finally, through their intracellular catalase-mimicking activity, these ultrasmall manganese ferrite nanoparticles induce an unprecedented tumor growth inhibition in a breast cancer murine model. All of these results show the robust characteristics of these nanoparticles for nanobiotechnological applications.

A Cascade Nanozyme with Amplified Sonodynamic Therapeutic Effects through Comodulation of Hypoxia and Immunosuppression against Cancer

The tumor microenvironment (TME) featured by immunosuppression and hypoxia is pivotal to cancer deterioration and metastasis. Thus, regulating the TME to improve cancer cell ablation efficiency has received extensive interest in oncotherapy. However, to reverse the immunosuppression and alleviate hypoxia simultaneously in the TME are major challenges for effective cancer therapy. Herein, a multifunctional platform based on Au nanoparticles and a carbon dots modified hollow black TiO₂ nanosphere (HABT-C) with intrinsic cascade enzyme mimetic activities is prepared for reversing immunosuppression and alleviating hypoxia in the TME. The HABT-C NPs possess triple-enzyme mimetic activity to act as self-cascade nanozymes, which produce sufficient oxygen to alleviate hypoxia and generate abundant ROS. The theoretical analysis demonstrates that black TiO₂ facilitates absorption of H₂O and O₂, separation of electron-holes, and generation of ROS, consequently amplifying the sonodynamic therapy (SDT) efficiency. Specifically, HABT-C exhibits favorable inhibition of immunosuppressive mediator expression, along with infiltrating of immune effector cells into the TME and reversing the immunosuppression in the TME. As a result, HABT-C can effectively kill tumor cells via eliciting immune infiltration, alleviating hypoxia, and improving SDT efficiency. This cascade nanozyme-based platform (HABT-C@HA) will provide a strategy for highly efficient SDT against cancer by modulation of hypoxia and immunosuppression in the TME.

Multifunctional Graphdiyne-Cerium Oxide Nanozymes Facilitate MicroRNA Delivery and Attenuate Tumor Hypoxia for Highly Efficient Radiotherapy of Esophageal Cancer

Radioresistance is an important challenge for clinical treatments. The main causes of radioresistance include hypoxia in the tumor microenvironment, the antioxidant system within cancer cells, and the upregulation of DNA repair proteins. Here, a multiple radiosensitization strategy of high-Z-element-based radiation enhancement is designed, attenuating hypoxia and microRNA therapy. The novel 2D graphdiyne (GDY) can firmly anchor and disperse CeO₂ nanoparticles to form GDY-CeO₂ nanocomposites, which exhibit superior catalase-mimic activity in decomposing H₂ O₂ to O₂ to significantly alleviate tumor hypoxia, promote radiation-induced DNA damage, and ultimately inhibit tumor growth in vivo. The miR181a-2-3p (miR181a) serum levels in patients are predictive of the response to preoperative radiotherapy in locally advanced esophageal squamous cell carcinoma (ESCC) and facilitate personalized treatment. Moreover, miR181a can act as a radiosensitizer by directly targeting RAD17 and regulating the Chk2 pathway. Subsequently, the GDY-CeO₂ nanocomposites with miR181a are conjugated with the iRGD-grafted polyoxyethylene glycol (short for nano-miR181a), which can increase the stability, efficiently deliver miR181a to tumor, and exhibit low toxicity. Notably, nano-miR181a can overcome radioresistance and enhance therapeutic efficacy both in a subcutaneous tumor model and human-patient-derived xenograft models. Overall, this GDY-CeO₂ nanozyme and miR181a-based multisensitized radiotherapy strategy provides a promising therapeutic approach for ESCC.

Persistent Regulation of Tumor Hypoxia Microenvironment via a Bioinspired Pt-Based Oxygen Nanogenerator for Multimodal Imaging-Guided Synergistic Phototherapy

Multifunctional nanoplatforms for imaging-guided synergistic antitumor treatment are highly desirable in biomedical applications. However, anticancer treatment is largely affected by the pre-existing hypoxic tumor microenvironment (TME), which not only causes the resistance of the tumors to photodynamic therapy (PDT), but also promotes tumorigenesis and tumor progression. Here, a continuous O2 self-enriched nanoplatform is constructed for multimodal imaging-guided synergistic phototherapy based on octahedral gold nanoshells (GNSs), which are constructed by a more facile and straightforward one-step method using platinum (Pt) nanozyme-decorated metal-organic frameworks (MOF) as the inner template. The Pt-decorated MOF@GNSs (PtMGs) are further functionalized with human serum albumin-chelated gadolinium (HSA-Gd, HGd) and loaded with indocyanine green (ICG) (ICG-PtMGs@HGd) to achieve a synergistic PDT/PTT effect and fluorescence (FL)/multispectral optoacoustic tomography (MSOT)/X-ray computed tomography (CT)/magnetic resonance (MR) imaging. The Pt-decorated nanoplatform endows remarkable catalase-like behavior and facilitates the continuous decomposition of the endogenous H2O2 into O2 to enhance the PDT effect under hypoxic TME. HSA modification enhances the biocompatibility and tumor-targeting ability of the nanocomposites. This TME-responsive and O2 self-supplement nanoparticle holds great potential as a multifunctional theranostic nanoplatform for the multimodal imaging-guided synergistic phototherapy of solid tumors.

A Porous Au@Rh Bimetallic Core-Shell Nanostructure as an H2 O2 -Driven Oxygenerator to Alleviate Tumor Hypoxia for Simultaneous Bimodal Imaging and Enhanced Photodynamic Therapy

In treatment of hypoxic tumors, oxygen-dependent photodynamic therapy (PDT) is considerably limited. Herein, a new bimetallic and biphasic Rh-based core-shell nanosystem (Au@Rh-ICG-CM) is developed to address tumor hypoxia while achieving high PDT efficacy. Such porous Au@Rh core-shell nanostructures are expected to exhibit catalase-like activity to efficiently catalyze oxygen generation from endogenous hydrogen peroxide in tumors. Coating Au@Rh nanostructures with tumor cell membrane (CM) enables tumor targeting via homologous binding. As a result of the large pores of Rh shells and the trapping ability of CM, the photosensitizer indocyanine green (ICG) is successfully loaded and retained in the cavity of Au@Rh-CM. Au@Rh-ICG-CM shows good biocompatibility, high tumor accumulation, and superior fluorescence and photoacoustic imaging properties. Both in vitro and in vivo results demonstrate that Au@Rh-ICG-CM is able to effectively convert endogenous hydrogen peroxide into oxygen and then elevate the production of tumor-toxic singlet oxygen to significantly enhance PDT. As noted, the mild photothermal effect of Au@Rh-ICG-CM also improves PDT efficacy. By integrating the superiorities of hypoxia regulation function, tumor accumulation capacity, bimodal imaging, and moderate photothermal effect into a single nanosystem, Au@Rh-ICG-CM can readily serve as a promising nanoplatform for enhanced cancer PDT.

Cu2 MoS4 /Au Heterostructures with Enhanced Catalase-Like Activity and Photoconversion Efficiency for Primary/Metastatic Tumors Eradication by Phototherapy-Induced Immunotherapy

Photoimmunotherapy can not only effectively ablate the primary tumor but also trigger strong antitumor immune responses against metastatic tumors by inducing immunogenic cell death. Herein, Cu₂ MoS₄ (CMS)/Au heterostructures are constructed by depositing plasmonic Au nanoparticles onto CMS nanosheets, which exhibit enhanced absorption in near-infrared (NIR) region due to the newly formed mid-gap state across the Fermi level based on the hybridization between Au 5d orbitals and S 3p orbitals, thus resulting in more excellent photothermal therapy and photodynamic therapy (PDT) effect than single CMS upon NIR laser irradiation. The CMS and CMS/Au can also serve as catalase to effectively relieve tumor hypoxia, which can enhance the therapeutic effect of O₂ -dependent PDT. Notably, the NIR laser-irradiated CMS/Au can elicit strong immune responses via promoting dendritic cells maturation, cytokine secretion, and activating antitumor effector T-cell responses for both primary and metastatic tumors eradication. Moreover, CMS/Au exhibits outstanding photoacoustic and computed tomography imaging performance owing to its excellent photothermal conversion and X-ray attenuation ability. Overall, the work provides an imaging-guided and phototherapy-induced immunotherapy based on constructing CMS/Au heterostructures for effectively tumor ablation and cancer metastasis inhibition.

A Mesoporous Nanoenzyme Derived from Metal-Organic Frameworks with Endogenous Oxygen Generation to Alleviate Tumor Hypoxia for Significantly Enhanced Photodynamic Therapy

Tumor hypoxia compromises the therapeutic efficiency of photodynamic therapy (PDT) as the local oxygen concentration plays an important role in the generation of cytotoxic singlet oxygen (¹ O₂ ). Herein, a versatile mesoporous nanoenzyme (NE) derived from metal-organic frameworks (MOFs) is presented for in situ generation of endogenous O₂ to enhance the PDT efficacy under bioimaging guidance. The mesoporous NE is constructed by first coating a manganese-based MOFs with mesoporous silica, followed by a facile annealing process under the ambient atmosphere. After removing the mesoporous silica shell and post-modifying with polydopamine and poly(ethylene glycol) for improving the biocompatibility, the obtained mesoporous NE is loaded with chlorin e6 (Ce6), a commonly used photosensitizer in PDT, with a high loading capacity. Upon the O₂ generation through the catalytic reaction between the catalytic amount NE and the endogenous H₂ O₂ , the hypoxic tumor microenvironment is relieved. Thus, Ce6-loaded NE serves as a H₂ O₂ -activated oxygen supplier to increase the local O₂ concentration for significantly enhanced antitumor PDT efficacy in vitro and in vivo. In addition, the NE also shows T₂ -weighted magnetic resonance imaging ability for its in vivo tracking. This work presents an interesting biomedical use of MOF-derived mesoporous NE as a multifunctional theranostic agent in cancer therapy.

Gold Cube-in-Cube Based Oxygen Nanogenerator: A Theranostic Nanoplatform for Modulating Tumor Microenvironment for Precise Chemo-Phototherapy and Multimodal Imaging

Engineering a versatile oncotherapy nanoplatform integrating both diagnostic and therapeutic functions has always been an intractable challenge in targeted cancer treatment. Herein, to actualize the theme of precise medicine, a nanoplatform is developed by anchoring Mn-Cdots to doxorubicin (DOX)-loaded mesoporous silica-coated gold cube-in-cubes core/shell nanocomposites and further conjugating them to a Arg-Gly-Asp (RGD) peptide (denoted as RGD-CCmMC/DOX) to achieve an active-targeting effect. Under 635 nm irradiation, the nanoplatform acts as oxygen nanogenerator that produces O₂ in situ and amplifies the content of singlet oxygen (¹O₂) in the hypoxic tumor microenvironment (TME), which has been demonstrated to attenuate tumor hypoxia and synchronously enhance photodynamic efficacy. Moreover, the gold cube-in-cube core in this work has been proven as a photothermal agent for hyperthermia, which exhibits a favorable photothermal effect with a 65.6% calculated photothermal conversion efficiency under 808 nm irradiation. In addition, the nanoplatform achieves heat- and pH-sensitive drug release with precise control to specific-tumor sites, executing combined chemo-phototherapy functions. Besides, it functions as a multimodal bioimaging agent of photothermal, fluorescence, and magnetic resonance imaging for the accurate diagnosis and guidance of therapy. As validated by in vivo and in vitro assays, the TME-responsive nanoplatform is highly biocompatible and effectively obliterates 4T1 tumor xenografts on nude mice after triple-synergetic treatment. This work presents a rational design of versatile nanoplatforms, which modulate the TME to enable high therapeutic performance and multiplexed imaging, which provides an innovative paradigm for targeted tumor therapy.