Abstract Designing efficient, biocompatible radiation-sensitive materials to activate systemic immune responses can maximize tumoricidal effects against malignant tumors. Here, inspired by natural Mn-peroxidase, we propose the de novo design of the RuMn-oxygen complex (MnBTC-Ru) for biocatalytic and radiosensitization therapies to eradicate primary and metastatic tumors. Our results reveal that Mn-organic ligands can enhance the electron density of Ru clusters, thereby optimizing their binding to oxygen species and resulting in high reactive oxygen species and oxygen generation. Accordingly, MnBTC-Ru with radiation can enhance cell membrane and DNA damage, triggering apoptosis though oxidative damage, heightening radiosensitization, and activating CD8^+ T cells. When combined with anti-PD-1 therapy, this synergistic approach generates robust systemic antitumor responses in female mice, promoting the abscopal effect and establishing enduring immune memory against tumors, thereby reducing recurrence and metastasis. This design presents superior biocatalytic and radiosensitizing properties, which may provide promising and practical bio-nanotechnology for future treatments on eradicating primary and metastatic tumors. Subject terms: Nanotechnology in cancer, Nanoparticles, Nanocomposites, Nanostructures __________________________________________________________________ Radiosensitising agents can enhance radiotherapy and improve outcomes. Here, the authors report on the design of bioinspired Radiosensitising and biocatalytic nanoparticles to increase radiation tiggered cell death and immunogenic response to combat both primary and metastatic tumours. Introduction Cancer is a leading cause of death worldwide, responsible for millions of deaths each year and posing a significant challenge to global public health^[46]1–[47]4. Radiotherapy (RT), a widely utilized cancer treatment strategy that generates reactive oxygen species (ROS) and induces double-strand DNA breaks, has demonstrated significant efficacy when combined with immune checkpoint inhibitors in treating refractory, recurrent, and metastatic tumors, marking a breakthrough in cancer treatment^[48]5,[49]6. Nevertheless, factors such as radiation resistance, tumor heterogeneity, and the tumor microenvironment (TME) pose significant challenges to the clinical efficacy of RT-based immune checkpoint inhibitor therapy in certain solid tumors^[50]7–[51]10. Recently, studies have shown that creating radiation-sensitive drugs or materials to stimulate both local and systemic immune responses can maximize the tumoricidal effects on primary, regional recurrence, and metastatic tumors^[52]11–[53]13. However, the currently developed radiosensitizing materials (e.g., lanthanides, hafnium, and gold) are limited in their potential clinical translation due to their insufficient tumoricidal effects and low biodegradability, which may lead to chronic toxicities^[54]14–[55]16. Designing next-generation radiosensitizing materials to meet clinical tumor RT treatments encounters two significant challenges: 1) developing highly biocompatible and biodegradable radiosensitizing materials that enhance the energy deposition of X-ray radiation and ROS production; 2) the enhancement of ROS and oxygen (O[2]) generation to reverse the hypoxic TME condition, mitigate radioresistance, reduce material dosage, and activate systemic antitumor responses, thereby maximizing the therapeutic efficacy and preventing metastasis and recurrence^[56]17–[57]20. In recent years, artificial peroxidases that can generate ROS and O[2] in acidic and hydrogen peroxide (H[2]O[2])-rich TME are gaining increased popularity^[58]21–[59]23; for instance, metal oxides, metal hydroxides, and metal-coordinated carbon nanomaterials^[60]21,[61]24–[62]26. However, developing high-performance ROS- and O[2]-generating artificial peroxidases remains challenging due to the complex multielectron reactions involving H[2]O[2] molecules and oxygen radicals, intricate formation of intermediate bonds, and energy-intensive desorption of oxygen species^[63]27–[64]31. Furthermore, most artificial peroxidases consist of abundant inorganic or metallic components, which raises concerns regarding biological safety as next-generation radiosensitizing materials^[65]32–[66]35. Natural peroxidases, such as manganese (Mn)-peroxidase, which features Mn-oxygen complex site coordinated by organic ligands with spatial configuration, exhibit high ROS generation capabilities by facilitating the entry of reactants through distinctive three-dimensional spatial arrangements and modulating the redox reactions of the Mn sites via organic ligand coordination^[67]36–[68]38. Recently, our research team reported that ruthenium (Ru), a relatively high atomic number metal belonging to the iron group, possesses good biocompatibility and unique biocatalytic properties—specifically, more d electrons, sufficient unoccupied orbitals, and superior redox stability—that enable efficient O[2] generation through rapid electron transfer with H[2]O[2] as the substrate^[69]39–[70]42. Therefore, by mimicking the structural properties and Mn active sites of natural Mn-peroxidase, the development of artificial peroxidase materials that integrate Mn-oxygen complex with Ru species through organic ligand coordination strategies is anticipated to offer a biocompatible and biodegradable approach to overcome the challenges associated with unbalanced multielectron reactions involving ROS and O[2] cycling catalysis^[71]43–[72]45, while this has not been reported. Here, drawing inspiration from the coordination and catalytic properties of natural Mn-peroxidase, we propose the de novo design of RuMn-oxygen complex (MnBTC-Ru) that contains catalytic sites formed by Ru clusters coordinated within the Mn-organic ligands for biocatalytic and radiosensitization therapies to eradicate primary and metastatic tumors (Fig. [73]1a). The core motivation behind this research stems from two key factors: 1) the bioinspired design of MnBTC-Ru showcases dual functional biocatalytic properties and effective radiosensitizing capabilities, swiftly increasing ROS and O[2] levels concurrently in TME condition to maximize the tumoricidal effects on primary tumor; and 2) the biocompatible and biodegradable Mn-organic coordination structures of MnBTC-Ru allow for potential applications for stimulating systemic antitumor responses to prevent metastatic tumors. Notably, our experimental and theoretical investigations reveal that the Mn-organic ligands play a critical role in increasing the electron density of Ru clusters, which optimizes the binding affinity of oxygen species and results in high ROS and O[2] generation capacities. Our findings have disclosed that the MnBTC-Ru can effectively enhance DNA damage and trigger robust apoptosis by promoting oxidative damage to the cell membrane, thereby increasing the sensitivity of cancer cells to X-ray irradiation. Accordingly, the MnBTC-Ru+RT treatment promotes a transformative response in the tumor’s microenvironment, heightening radiosensitization and activating CD8^+ T cells within the tumor. Furthermore, when combined with anti-PD-1 therapy, this synergetic approach leads to intensive systemic antitumor responses, fostering the abscopal effect and establishing enduring memory against tumors, which effectively prevents tumor recurrence and metastasis and significantly enhances treatment outcomes and long-term prognosis. Noteworthy, our design showcases biocatalytic and radiosensitizing properties, thus providing promising bio-nanotechnology with superior effects on eradicating primary and metastatic tumors, especially malignant tumors. Fig. 1. Design and structure characterizations of MnBTC-Ru complex. [74]Fig. 1 [75]Open in a new tab a Schematic illustration of the synthesis of MnBTC-Ru complex and its role as a biocatalytic and radiosensitive agent that activates systemic antitumor response, facilitating the eradication of primary and metastatic tumors. b Natural Mn-peroxidase-inspired construction of RuMn-oxygen complex for ROS biocatalysis. c FTIR spectrum of MnBTC-Ru and MnBTC. d SEM, e TEM, and f HAADF-STEM images of MnBTC-Ru. g Diameter analysis of Ru clusters on MnBTC-Ru. h Atomic-resolution HAADF-STEM image of MnBTC-Ru. i, j EDS mapping and k EDS spectra of MnBTC-Ru. Experiments were repeated independently (d–f, h–j) three times with similar results. In (a), ICD indicates immunogenic cell death, HMGB1 indicates high mobility group box-1, DC indicates dendritic cell, CRT indicates cell surface calreticulin, ATP indicates adenosine triphosphate. Atomic color coding in (a, b): Ru, yellow; Mn, blue; C, khaki; H, white; O, purple. In (i), Mix indicates mixture. In (c, g, k), a.u. indicates the arbitrary units. Source data are provided as a [76]Source Data file. Results Design and structure characterizations of MnBTC-Ru complex In a typical synthetic process, the MnBTC-Ru complex, containing catalytic sites formed by Ru clusters coordinated with the Mn-organic ligands, is synthesized through a sequential reaction process. First, Mn-organic precursors (MnBTC) are created via a one-step hydrothermal method that combines Mn salt and 1,3,5-benzenetricarboxylic acid (BTC). Subsequently, Ru ions are introduced into the MnBTC through metal ion adsorption, exchange, and nucleation processes to form MnBTC-Ru (Fig. [77]1a). For comparisons, carbon-supported Ru sites without spatial organic ligands, denoted as C-Ru, are also synthesized following methods outlined in the Methods. Inspired by the inherent catalytic properties of Mn-organic ligands in natural Mn-peroxidase, it can be inferred that the developed biocatalytic MnBTC-Ru complex may offer several structural advantages (Fig. [78]1b). These advantages include: i) the ability of Mn-BTC ligands to donate electrons, ii) the facilitation of *OOH desorption by the electron-rich Ru clusters, and iii) the capacity of MnBTC-Ru with spatial organic ligands for efficient and cycling ROS. X-ray diffraction analysis confirms the successful synthesis of crystalline MnBTC support (Supplementary Fig. [79]1). The molecular structure of MnBTC-Ru is evaluated through Fourier transform infrared (FTIR) spectroscopy, revealing the presence of -OH and -COOH groups, which are consistent with those found in MnBTC (Fig. [80]1c). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images illustrate that MnBTC-Ru showcases well-preserved spherical structures with an average diameter of around 350 nm (Fig. [81]1d and Supplementary Figs. [82]2, [83]3). Dynamic light scattering analysis indicates that MnBTC-Ru maintains good dispersion in both phosphate-buffered saline (PBS) and mouse serum, with average hydrodynamic diameters of 578 and 525 nm, respectively (Supplementary Fig. [84]4). These values closely correspond to the inherent particle size of MnBTC-Ru, demonstrating favorable dispersibility under simulated physiological conditions and supporting its low potential for in vivo aggregation and related adverse effects. Furthermore, detailed crystal facets of Ru clusters within MnBTC-Ru are observed in high-resolution TEM images, offering views along the (100) and (110) planes that align precisely with facet distances (Fig. [85]1e). High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images illustrate the presence of Ru clusters (denoted by yellow arrows) with an average size of 1.08 nm (Fig. [86]1f, g). Subsequent atomic-resolution HAADF-STEM imaging reveals that the Ru clusters (marked by yellow circles) are surrounded by a few atomically dispersed Mn atoms (marked by green circles; Fig. [87]1h and Supplementary Fig. [88]5). Energy-dispersive spectroscopy (EDS) mappings and spectra demonstrate the existence of Ru, Mn, C, and O elements, with Ru clusters primarily distributed on the outer surface of the MnBTC spherical structure (Fig. [89]1i–k and Supplementary Fig. [90]6). X-ray photoelectron spectroscopy (XPS) is employed to investigate the valence states and electronic configurations of the biocatalytic MnBTC-Ru complex (Supplementary Table [91]1). The high-resolution O 1s spectra validate the presence of metal-O peaks in both MnBTC-Ru and MnBTC, thus verifying the formation of MnBTC (Fig. [92]2a). Mn 2p analysis reveals the coexistence of Mn^2+ and Mn^3+ valence states within MnBTC-Ru, with MnO[6] centers coordinated exclusively to the oxygen atoms of BTC ligands exhibiting a +3 oxidation state, Mn species with unsaturated coordination exhibiting a +2 oxidation state, and electron transfer between the RuMn active centers inducing Mn to display valence states ranging from +2 to +3 (Fig. [93]2b and Supplementary Fig. [94]7)^[95]46–[96]48. Notably, the O 1s and Mn 2p spectra of MnBTC-Ru show a positive core level shift compared to those of MnBTC. In contrast, the Ru^0 species in MnBTC-Ru exhibit a significant negative level shift of 0.6 eV in the binding energy of the 3p[3/2] orbital when compared to C-Ru (Fig. [97]2c). These findings suggest that electrons are transferred from the electron-donating MnBTC to the Ru cluster sites. This electron transfer may facilitate overcoming the multiple electron reactions of oxygen intermediates on the Ru clusters, thereby ensuring a rapid redox reaction. Furthermore, the high electronegativity of Ru species, characterized by a Pauling scale value of 2.2, is also beneficial to enhance the electron transfer process. Fig. 2. Analysis of precise atomic coordination structures in MnBTC-Ru complex. [98]Fig. 2 [99]Open in a new tab The high-resolution XPS of a O 1s, b Mn 2p, and c Ru 3p for different catalysts. d Ru K-edge XANES spectra of MnBTC-Ru and references (Ru