Selenoprotein-Regulated Hydrogel for Ultrasound-Controlled Microenvironment Remodeling to Promote Bone Defect Repair

Abnormal levels of reactive oxygen species (ROS) and the hypoxic microenvironment within bone defects are important factors that impede bone repair processes. Herein, an innovative ultrasound-modulatable hydrogel platform with selenoprotein-mediated antioxidant effects to promote bone injury repair is presented. This hydrogel platform encapsulates oxygen-enriched selene-incorporated thin-shell silicon within methacrylate gelatin (O₂-PSSG). The resultant construct orchestrates the modulation of the bone-defect microenvironment, thereby expediting the course of bone regeneration. Ultrasound (US) is used to regulate the pore size of the hydrogel to release selenium-containing nanoparticles and promote the in situ synthesis of efficient intracellular selenoproteins and hydrogen peroxide consumption. As expected, O₂-PSSG rapidly releases selenocystine ([Sec]₂) under US control to scavenge reactive oxygen species and maintain the homeostasis of bone marrow mesenchymal stem cells (BMSCs). Over time, the action of the system by selenoprotein increases the activation of Wnt/β-catenin pathways and promotes the differentiation of BMSCs. Consequently, O₂-PSSG potentiates the antioxidant proficiency of BMSCs both in vitro and in vivo, alleviates hypoxic environments, promotes osteogenic differentiation, and expedites cranial bone repair in rat models. In summary, this study suggests that the designed and constructed US-responsive antioxidant hydrogel is a promising prospective strategy for addressing bone defects and fostering bone regeneration.     

Magnetic Hyperthermia–Synergistic H2O2 Self‐Sufficient Catalytic Suppression of Osteosarcoma with Enhanced Bone‐Regeneration Bioactivity by 3D‐Printing Composite Scaffolds

Chemotherapy resistance and bone defects caused by surgical excision of osteosarcoma have been formidable challenges for clinical treatment. Although recently developed nanocatalysts based on Fenton‐like reactions for catalytic therapy demonstrate high potential to eliminate chemotherapeutic‐insensitive tumors, insufficient concentration of intrinsic hydrogen peroxide (H₂O₂) and low intratumoral penetrability hinder their applications and therapeutic efficiency. The synchronous enriching intratumor H₂O₂ amount or nanoagents and promoting osteogenesis are intriguing strategies to solve the dilemma in osteosarcoma therapy. Herein, a multifunctional “all‐in‐one” biomaterial platform is constructed by co‐loading calcium peroxide (CaO₂) and iron oxide (Fe₃O₄) nanoparticles into a three‐dimensional (3D) printing akermanite scaffold (AKT‐Fe₃O₄‐CaO₂). The loaded CaO₂ nanoparticles act as H₂O₂ sources to achieve H₂O₂ self‐sufficient nanocatalytic osteosarcoma therapy as catalyzed by coloaded Fe₃O₄ nanoagents, as well as provide calcium ion (Ca²⁺) pools to enhance bone regeneration. The synergistic osteosarcoma‐therapeutic effect is achieved from both magnetic hyperthermia as‐enabled by Fe₃O₄ nanoparticles under alternative magnetic fields and hyperthermia‐enhanced Fenton‐like nanocatalytic reaction for producing highly toxic hydroxyl radicals. Importantly, the constructed 3D AKT‐Fe₃O₄‐CaO₂ composite scaffolds are featured with favorable bone‐regeneration activity, providing a worthy base and positive enlightenment for future osteosarcoma treatment with bone defects by the multifunctional biomaterial platforms.     

Polyphenol-Mediated Synthesis of Superparamagnetic Magnetite Nanoclusters for Highly Stable Magnetically Responsive Photonic Crystals

Achieving high stability and excellent optical performance in complex environments is crucial for practical applications of magnetically responsive photonic crystals (MRPCs). It, however, remains a great challenge. This study demonstrates a polyphenol-mediated strategy for synthesizing size-controllable superparamagnetic magnetite (Fe₃O₄) colloid nanocrystal clusters (CNCs) that can be stably dispersed in various polar solvents to form MRPCs with brilliant structural colors for a long term. As tannic acid (TA) functions as a linker to robustly bind polyvinylpyrrolidone (PVP) chains to Fe₃O₄ surfaces, the MRPCs can maintain nearly constant diffraction wavelength and high reflectance for up to 4 years. The strong coordination between TA and Fe³⁺ inhibits crystal growth, ensuring the small primary crystal size and superparamagnetism of Fe₃O₄@TA-PVP CNCs. Partial oxidation of TA accelerates the crystal nucleation and growth, reducing the overall CNC particle size, which can be utilized for controlling the particle size. Additionally, enhancing the dissolution of PVP before the solvothermal reaction improves the size monodispersity of the products, making the as-constructed MRPCs ideal for practical applications in color display, sensors, anti-counterfeiting, and camouflage. The Fe₃O₄@TA-PVP CNCs with high stability and versatility for surface-functionalization are also promising for magnetic resonance imaging, targeting drug delivery, recyclable catalysis, and magnetic nanomotors.     

3D Superelastic Scaffolds Constructed from Flexible Inorganic Nanofibers with Self‐Fitting Capability and Tailorable Gradient for Bone Regeneration

Repair of bone defects with irregular shapes or at soft tissue insertion sites faces a huge challenge. Scaffolds capable of adapting to bone cavities, generating stiffness gradients, and inducing osteogenesis are necessary. Herein, a superelastic 3D ceramic fibrous scaffold is developed by assembly of intrinsically rigid, structurally flexible electrospun SiO₂ nanofibers with chitosan as bonding sites (SiO₂ NF‐CS) via a lyophilization technique. SiO₂ NF‐CS scaffolds exhibit excellent elasticity (full recovery from 80% compression), fast recovery rate (>500 mm min^?1), and good fatigue resistance (>10 000 cycles of compression) in an aqueous medium. SiO₂ NF‐CS scaffolds induce human mesenchymal stem cell (hMSC) elongation and differentiation into osteoblasts. In vivo self‐fitting capability is demonstrated by implanting compressed SiO₂ NF‐CS scaffolds into different shaped mandibular defects in rabbits, with a spontaneous recovery and full filling of defects. Rat calvarial defect repair validates enhanced bone formation and vascularization by cell (hMSC) histomorphology analysis. Further, subchondral bone scaffolds with gradations in SiO₂ nanofibers are developed, leading to a stiffness gradient and spatially chondrogenic and osteogenic differentiation of hMSCs. This work presents a type of 3D ceramic fibrous scaffold, which can closely match bone defects with irregular shapes or at different implant sites, and is promising for clinical translation.     

Electrospinning Multilayered Scaffolds Loaded with Melatonin and Fe3O4 Magnetic Nanoparticles for Peripheral Nerve Regeneration

Peripheral nerve injury is a common clinical problem bringing heavy burden to patients, due to its high incidence and unsatisfactory treatment. Nerve guidance conduit (NGC) is a promising scaffold for peripheral nerve repair, and bioactive agents are applied for great functional recovery. Melatonin (MLT) and Fe₃O₄ magnetic nanoparticles (Fe₃O₄‐MNPs) are proven to inhibit oxidative stress, inflammation, and induce nerve regeneration. Herein, a multilayered composite NGC loaded with MLT and Fe₃O₄‐MNPs is designed for sequential and sustainable drug release, creating an appropriate microenvironment for nerve regeneration. The composite scaffold shows sufficient mechanical strength and biocompatibility in vitro, and evidently promotes morphological, functional, and electrophysiological recovery of regenerated sciatic nerves in vivo. This work proves that the multilayered conduits show great prospect in the long‐term nerve defects treatment due to easy manufacture and desired efficacy.     

Bioprinted Scaffold Remodels the Neuromodulatory Microenvironment for Enhancing Bone Regeneration

Herein, a 3D bioprinted scaffold is proposed, containing a calcitonin gene-related peptide (CGRP) and the β-adrenergic receptor blocker propranolol (PRN) as a new method to achieve effective repair of bone defects. By leveraging the neuromodulation mechanism of bone regeneration, CGRP and PRN loaded mesoporous silica nanoparticles are added into a hybrid bio-ink, which initially contains gelatin methacrylate, Poly (ethylene glycol) diacrylate and bone marrow mesenchymal stem cells (BMSCs). Subsequently, the optimized bio-ink is used for 3D bioprinting to create a composite scaffold with a pre-designed micro-nano hierarchical structure. The migration and tube formation of human umbilical vein endothelial cells (HUVECs) can be promoted by the scaffold, which is beneficial to the formation of a new capillary network during the bone repair process. With the release of CGRP from the scaffold, the secretion of neuropeptides by sensory nerves is simulated. Meanwhile, the release of PRN can inhibit the binding process of catecholamine to β-adrenergic receptor, co-promoting the osteogenic differentiation of BMSCs with CGRP and silicon ions, which will effectively enhance bone repair of a critical-sized cranial defect in a rat model. In conclusion, this study provides a promising strategy for bone defect repair by understanding the neuromodulatory mechanisms during bone regeneration.     

Noncompressible Hemostasis and Bone Regeneration Induced by an Absorbable Bioadhesive Self-Healing Hydrogel

Bone bleeding and bone defects arising from trauma or bone tumor resection pose a great threat to patients and they are challenging problems to orthopedic surgeons. Traditional hemostatic materials are not suitable for bone fractures where compression cannot be applied, neither are they effective during surgeries where large amounts of body fluids prevent them from adhering to the large and irregular bone wound sites. This research introduces a catechol-conjugated chitosan (CHI-C) multi-functional hydrogel with adhesion, self-healing, cytocompatibility, hemocompatibility, and blood cell coagulation capacity. The hydrogel can be injected into internal and irregular bleeding sites and bone defective areas, and then rapidly self-heals (within 2 min) to an integrated hydrogel that fully fills the defective sites and strongly sticks to bleeding areas in the presence of body fluids during surgery. In vivo experiments using a rabbit ilium bone defect model demonstrate quick hemostasis after the hydrogel is applied and the blood loss is only ¼ compared to the untreated injuries. In addition, the bone regeneration is not interfered by the hydrogel and the bone defect is no longer visible with disappearance of the hydrogel after 4 weeks. This multi-functional hydrogel is potentially valuable for clinical applications towards tissue adhesion, hemostasis, and bone regeneration.     

Surface State Mediated NIR Two‐Photon Fluorescence of Iron Oxides for Nonlinear Optical Microscopy

The development of fluorescent iron oxide nanomaterials is highly desired for multimodal molecular imaging. Instead of incorporating fluorescent dyes on the surface of iron oxides, a ligand‐assisted synthesis approach is developed to allow near‐infrared (NIR) fluorescence in Fe₃O₄ nanostructures. Using a trimesic acid (TMA)/citrate‐mediated synthesis, fabricated Fe₃O₄ nanostructures can generate a NIR two‐photon florescence (TPF) peak around 700 nm under the excitation by a 1230‐nm femtosecond laser. By tailoring the absorption of Fe₃O₄ nanostructures toward NIR band, the NIR‐TPF efficiency can be greatly increased. Through internal etching, surface peeling, and ligand replacement, spectroscopic results validated that such resonantly enhanced NIR‐TPF is mediated by surface states with strong NIR‐IR absorption. This TPF signal evolution can be generalized to other iron oxide nanomaterials like magnetite nanoparticles and α‐Fe₂O₃ nanoplates. Using the developed fluorescent Fe₃O₄ nanostructures, it is demonstrated that their TPF and third harmonic generation (THG) contrast in the nonlinear optical microscopy of live cells. It is anticipated that the synthesized NIR photofunctional Fe₃O₄ will serve as a versatile platform for dual‐modality magnetic resonance imaging (MRI) as well as a magnet‐guided theranostic agent.     

3D Network Magnetophotonic Crystals Fabricated on Morpho Butterfly Wing Templates

A simple synthesis method combining a sol‐gel route followed by a reduction step is developed for the fabrication of magnetophotonic crystal (MPC) materials from Morpho butterfly wings. The sol‐gel route leads to hematite with a photonic crystal structure (PC‐α‐Fe₂O₃) being faithfully replicated from a biotemplate, and the desired magnetophotonic crystal Fe₃O₄ (MPC‐Fe₃O₄) is obtained by the reduction of the PC‐α‐Fe₂O₃ under a H₂/Ar atmosphere. The structural replication fidelity of the process is demonstrated on both the macro‐ and microscale, and even down to the nanoscale, as evidenced by scanning electron microscopy, X‐ray diffraction, reflectance measurements, and transmission electron microscopy. It is found that the chemical transformation of PC‐α‐Fe₂O₃ to MPC‐Fe₃O₄ changes only the dielectric constant and does not induce structural defects that could affect the photonic‐crystal properties of the composite. The photonic band gap of MPC‐Fe₃O₄ can be red‐shifted with an increase of the external magnetic field strength, which is further supported by theoretical calculations. The reported biomimetic technique provides an effective approach to produce magnetophotonic crystals from nature with 3D networks, which may open up an avenue for the creation of new magneto‐optical devices and theoretical research in this field.     

Bioresponsive Self-Reinforcing Sericin/Silk Fibroin Hydrogel for Relieving the Immune-Related Adverse Events in Tumor Immunotherapy

Despite the immense potential of immune checkpoint blockade (ICB) therapy in tumor treatment, its widespread clinical application is currently limited by unsatisfactory curative effect and off-target adverse effect. Herein, an injectable sericin (SS)/silk fibroin (SF) recombinant hydrogel, termed SF-SS-SMC hydrogel, is developed to enable local delivery of anti-CD47 antibody (α CD47). The hydrogel displays self-reinforcement in high H₂O₂ concentration of tumor microenvironment (TME), as the SS/Fe²⁺ supramolecular nanocomplex (SS-SMC) inside the hydrogel converts H₂O₂ to reactive oxygen species (ROS), further triggering additional crosslinking among the SF polymers. Therefore, the SF-SS-SMC hydrogel has an in vivo retention time longer than 21 days and acts as a reservoir for the long-term sustained release of α CD47. More importantly, the SF-SS-SMC hydrogel itself efficiently regulates the remodeling of a protumor immunosuppressive TME to an antitumoral TME through switching of tumor-associated macrophages from an anti-inflammatory M2 phenotype to a proinflammatory M1 phenotype without additional drugs. Based on the combined effect of sustained α CD47 release and TME reprogramming, the SF-SS-SMC hydrogel has satisfactory immunotherapeutic effects in the treatment of local, abscopal, remitting, and metastatic tumors. Further advantages, including low cost of production, simple fabrication, and ease of use, make it promising for commercial mass production.     

Co3O4/Fe2O3异质结复合材料的制备及其紫外光光电探测性能

分别采用旋涂法和水热法在FTO衬底上制备Co₃O₄种子层和Co₃O₄薄膜,再在Co₃O₄薄膜上水热生长Fe₂O₃纳米棒,获得了高质量的Co₃O₄/Fe₂O₃异质结复合材料。通过改变Fe₂O₃前驱体溶液浓度来改变异质结复合材料中Fe₂O₃组分的含量。结果表明,Fe₂O₃纳米棒覆盖在呈网状结构的Co₃O₄薄膜上,随着Fe₂O₃前驱体溶液浓度即Fe₂O₃组分含量的增加,Co₃O₄/Fe₂O₃异质结复合材料对紫外光的响应逐渐增强,当Fe₂O₃前驱体溶液浓度为0.015mol/L时,异质结复合材料有着很好的光电稳定性,并表现出较高的响应率(12.5mA/W)和探测率(4.4×10¹⁰Jones)。     

Microwave absorption characteristics of chiral materials with Fe3O4-polyaniline composite matrix

Fe₃O₄-polyaniline composites have been prepared in which the concentrations of Fe₃O₄ are 10%, 15%, 20%, 30% and 40% by weight. Microwave chiral composites are then prepared employing copper helices as chiral inclusions and the Fe₃O₄-polyaniline composites as the matrix. The electromagnetic parameters of the chiral Fe₃O₄-polyaniline composites are measured using a circular waveguide method at 9.5 GHz, and the normal reflectance from a perfect conductor-backed chiral slab is calculated. The microwave absorption characteristics of the chiral Fe₃O₄- polyaniline composites are studied and compared with those of a non-chiral Fe₃O₄-polyaniline composite matrix. The results show that the addition of the chiral inclusions to the non-chiral matrix improves both the dielectric and the magnetic losses. As well as this improvement in losses, the chiral materials have higher microwave absorption. The optimal concentration of Fe₃O₄ in the matrix is about 15% to obtain the lowest reflectance of chiral Fe₃O₄-polyaniline composites.     

Nitrogen‐Doped Carbon Quantum Dot Stabilized Magnetic Iron Oxide Nanoprobe for Fluorescence,Magnetic Resonance,and Computed Tomography Triple‐Modal In Vivo Bioimaging

Multimodal imaging, which combines complementary information of two or more imaging modalities, offers huge advantages. In this paper, the synthesis, characterization, and application of superparamagnetic nitrogen‐doped carbon‐iron oxide hybrid quantum dots (C‐Fe₃O₄ QDs) is reported for triple‐modal bioimaging through fluorescence/magnetic resonance/computed tomography (FL/MR/CT). Especially, C‐Fe₃O₄ QDs are synthesized by using poly (γ‐glutamic acid) as a precursor and stabilizer via a green and facile one‐pot hydrothermal approach. The as‐prepared C‐Fe₃O₄ QDs exhibit excellent water dispersibility, wavelength‐tunable FL property with high quantum yield of about 21.6%, good photostability, strong superparamagnetic property as well as favorable biocompatibility. Meanwhile, these C‐Fe₃O₄ QDs also show a transverse relaxivity value (r ₂) of 154.10 mm ^?1 s^?1 for T₂‐weighted MR imaging mode and an observable X‐ray attenuation effect for CT imaging mode. Moreover, the in vivo bioimaging of tumor‐bearing nude mice by combining FL, MR, and CT images further demonstrates that the as‐prepared C‐Fe₃O₄ QDs can be readily and efficiently used in FL/MR/CT triple‐modal tumor imaging. Hence, the new and facile one‐pot synthesis strategy for preparing multifunctional C‐Fe₃O₄ QDs nanoprobes provides a convenient way for achieving an effective and versatile agent for tumorous bioimaging/or diagnostics.     

“Naked” Magnetically Recyclable Mesoporous Au–γ‐Fe2O3 Nanocrystal Clusters: A Highly Integrated Catalyst System

Naked magnetically recyclable mesoporous Au–γ‐Fe₂O₃ clusters, combining the inherent magnetic properties of γ‐Fe₂O₃ and the high catalytic activity of Au nanoparticles (NPs), are successfully synthesized. Hydrophobic Au–Fe₃O₄ dimers are first self‐assembled to form sub‐micrometer‐sized Au–Fe₃O₄ clusters. The Au–Fe₃O₄ clusters are then coated with silica, calcined at 550 °C, and finally alkali treated to dissolve the silica shell, yielding naked‐Au–γ‐Fe₂O₃ clusters containing Au NPs of size 5–8 nm. The silica protection strategy serves to preserve the mesoporous structure of the clusters, inhibit the phase transformation from γ‐Fe₂O₃ to α‐Fe₂O₃, and prevent cluster aggregation during the synthesis. For the reduction of p‐nitrophenol by NaBH₄, the activity of the naked‐Au–γ‐Fe₂O₃ clusters is ≈22 times higher than that of self‐assembled Au–Fe₃O₄ clusters. Moreover, the naked‐Au–γ‐Fe₂O₃ clusters display vastly superior activity for CO oxidation compared with carbon‐supported Au–γ‐Fe₂O₃ dimers, due to the intimate interfacial contact between Au and γ‐Fe₂O₃ in the clusters. Following reaction, the naked‐Au–γ‐Fe₂O₃ clusters can easily be recovered magnetically and reused in different applications, adding to their versatility. Results suggest that naked‐Au–γ‐Fe₂O₃ clusters are a very promising catalytic platform affording high activity. The strategy developed here can easily be adapted to other metal NP–iron oxide systems.     

Highly Efficient Photoelectrochemical Water Splitting: Surface Modification of Cobalt‐Phosphate‐Loaded Co3O4/Fe2O3 p–n Heterojunction Nanorod Arrays

Hematite (α‐Fe₂O₃) as a photoanode material for photoelectrochemical (PEC) water splitting suffers from the two problems of poor charge separation and slow water oxidation kinetics. The construction of p–n junction nanostructures by coupling of highly stable Co₃O₄ in aqueous alkaline environment to Fe₂O₃ nanorod arrays with delicate energy band positions may be a challenging strategy for efficient PEC water oxidation. It is demonstrated that the designed p‐Co₃O₄/n‐Fe₂O₃ junction exhibits superior photocurrent density, fast water oxidation kinetics, and remarkable charge injection and bulk separation efficiency (η_inj and η_sep), attributing to the high catalytic behavior of Co₃O₄ for the oxygen evolution reaction as well as the induced interfacial electric field that facilitates separation and transportation of charge carriers. In addition, a cocatalyst of cobalt phosphate (Co‐Pi) is introduced, which brings the PEC performance to a high level. The resultant Co‐Pi/Co₃O₄/Ti:Fe₂O₃ photoanode shows a photocurrent density of 2.7 mA cm^?2 at 1.23 V_RHE (V vs reversible hydrogen electrode), 125% higher than that of the Ti:Fe₂O₃ photoanode. The optimized η_inj and η_sep of 91.6 and 23.0% at 1.23 V_RHE are achieved on Co‐Pi/Co₃O₄/Ti:Fe₂O₃, respectively, corresponding to the 70 and 43% improvements compared with those of Ti:Fe₂O₃. Furthermore, Co‐Pi/Co₃O₄/Ti:Fe₂O₃ shows a low onset potential of 0.64 V_RHE and long‐time PEC stability.     

Deposition of Fe3O4 on oxidized activated carbon by hydrazine reducing method for high performance supercapacitor

Oxidized activated carbon/Fe₃O₄ (AC/Fe₃O₄) composites for supercapacitor electrodes were synthesized by a reduction method. Poly(vinylpyrrolidone) was added as a dispersing agent for homogeneous deposition of Fe₃O₄ on AC. The obtained products were identified as AC/Fe₃O₄ by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis. Morphological characterization of AC/Fe₃O₄ was carried out by field emission scanning electron microscopy (FE-SEM); the results clearly showed the formation of Fe₃O₄ nanoparticles about 30 nm in diameter on AC. Moreover, by using N₂ adsorption/desorption isotherm analysis, we confirmed that surface areas and pore volumes decreased with increasing Fe₃O₄ content. We also carried out electrochemical characterization of AC and AC/Fe₃O₄ composites. Remarkably, we found that the value of specific capacitance increased significantly from 99.4 F g⁻¹ of raw AC to 202.6 F g⁻¹ of AC/Fe₃O₄ composites at 10 mV s⁻¹ of scan rate. This result can be ascribed to a synergistic effect of the combination of electrical double-layer capacitance and pseudo-capacitance properties. This research represents a valuable contribution to the application of supercapacitor electrodes in regard to cost effectiveness and simple fabrication.     

Multifunctional Hydroxyapatite Nanobelt Haystacks Integrated Neural Stem Cell Spheroid for Rapid Spinal Cord Injury Repair

Due to the unwarranted lifespan and differentiation, applying neural stem cells (NSCs) in spinal cord injury (SCI) remains challenging. In this study, 3D bioactive hydroxyapatite (HAp) nanobelt haystack-mouse NSC (mNSC) hybrid spheroids are customized in which the specific nanobelt haystack framework provided the structural function of hypoxia alleviation in the spherical core and biological process of neural differentiation promotion. Commodified with superparamagnetic ferroferric oxide (Fe₃O₄) nanoparticles and a polydopamine (PDA) coating, the HAp nanobelts are endowed with magnetic field-driven properties and enhanced cell-nanobelt adhesion. The engineered bioresponsive 3D nanobelt haystack-mNSC hybrid spheroids effectively repair SCI in vivo, showing new potential for stem cell therapy by incorporating nanomaterials in 3D culture based on cell-material interactions.     

Atomistic Study of a CaTiO3‐Based Mixed Conductor: Defects,Nanoscale Clusters,and Oxide‐Ion Migration

Mixed oxide‐ion and electronic conductivity can be exploited in dense ceramic membranes for controlled oxygen separation as a means of producing pure oxygen or integrating with catalytic oxidation. Atomistic simulation has been used to probe the energetics of defects, dopant‐vacancy association, nanoscale cluster formation, and oxide‐ion transport in mixed‐conducting CaTiO₃. The most favorable energetics for trivalent dopant substitution on the Ti site are found for Mn³⁺ and Sc³⁺. Dopant‐vacancy association is predicted for pair clusters and neutral trimers. Low binding energies are found for Sc³⁺ in accordance with the high oxide‐ion conductivity of Sc‐doped CaTiO₃. The preferred location for Fe⁴⁺ is in a hexacoordinated site, which supports experimental evidence that Fe⁴⁺ promotes the termination of defect chains and increases disorder. A higher oxide‐ion migration energy for a vacancy mechanism is predicted along a pathway adjacent to an Fe³⁺ ion rather than Fe⁴⁺ and Ti⁴⁺, consistent with the higher observed activation energies for ionic transport in reduced CaTi(Fe)O_3–δ.     

Schottky Heterojunction Facilitates Osteosarcoma Ferroptosis and Enhances Bone Formation in a Switchable Mode

Effective antitumor agents with concurrent osteogenic properties are essential for comprehensive osteosarcoma (OS) treatment. However, the current clinical therapeutic strategies of OS fail to completely eradicate tumors while simultaneously encouraging bone formation. To address this issue, a switchable strategy for dynamic OS ablation and static bone regeneration is developed by integrating piezoelectric BaTiO₃ (BTO) with atomic-thin Ti₃C₂ (TC) through a Schottky heterojunction, resulting in the formation of TC@BTO. Under sequential ultrasound and near-infrared irradiation, the optimized carrier transport of TC@BTO, based on Schottky heterojunction, exhibits excellent characteristics of photothermal conversion and reactive oxygen species generation. This results in ferroptosis of tumor cells and eventual elimination of OS. Moreover, in the static state, the interfacial Schottky heterojunction facilitates the carriers’ directed transfer from the semiconductor to the metal. The Schottky heterojunction-enhanced static electrical stimulation enhances the osteogenic differentiation of bone marrow-derived mesenchymal stem cells and repair of bone defects. Furthermore, RNA-sequencing analysis reveals that static TC@BTO promotes bone regeneration by activating Wnt signaling pathway, and remarkably, pharmacological inhibition of Wnt signaling suppresses the TC@BTO-induced osteogenesis. Overall, this work broadens the biomedical potential of Schottky heterojunction-based therapies and provides a comprehensive strategy for overall OS ablation and bone regeneration.     

Photocatalytic reduction of chromate oxyanions on MMnFe2O4 (M=Zn,Cd) nanoparticles

Spinel M_xMn_1−xFe₂O₄ ferrites (M=Zn or Cd) synthesized via the co-precipitation method were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), diffuse reflectance UV–vis and Mössbauer spectroscopy. MnFe₂O₄ exhibited mainly cubic structure when Cd was incorporated, whereas the Zn incorporation stimulated a mixed phase consisting of MnFe₂O₄ and ZnMnFe₂O₄. The IR spectra of both Cd- and Zn modified MnFe₂O₄ samples revealed vibration of the chemical bond Fe²⁺O²⁻ in A location of the tetrahedron which infers that dopants were uniformly distributed over the system. The optical band gap energy showed large variations; a smaller value was determined for Cd_0.2Mn_0.8Fe₂O₄ (1.46 eV) when compared with those of MnFe₂O₄ (2.16 eV) and Zn_0.2Mn_0.8Fe₂O₄ (2.8 eV). The analysis of Mössbauer spectra gave inversion values of Fe³⁺ distribution in tetrahedral coordinated sites of 24%, 57% and 65% in MnFe₂O₄, Zn_0.2Mn_0.8Fe₂O₄ and Cd_0.2Mn_0.8Fe₂O₄, respectively. It was found that Cd_0.2Mn_0.8Fe₂O₄ exhibited the best performance in the photocatalytic reduction of Cr(VI) to Cr(III) having a maximum value of 96% within 30 min, and the experimental data obeyed pseudo-second-order rate kinetic model. Also, the linear model of Langmuir attained a maximum adsorption capacity of 37 mg g⁻¹ for Cd_0.2Mn_0.8Fe₂O₄.