Cerium Ions Research Articles

Development and evaluation of thiosalicylic-modified/ion-imprinted chitosan for selective removal of cerium (III) ion

Chitosan was used in this study as the bio-based product for the development of microparticles for the specifically targeted removal of cerium ions (Ce3+) by ion-imprinting technology. A thiosalicylic hydrazide-modified chitosan (TSCS) is produced via cyanoacetylation of chitosan, followed by hydrazidine derivatization to finally introduce the thiosalicylate chelating units. Ion-imprinted Ce-TSCS sorbent microparticles were prepared by combining the synthesized TSCS with Ce3+, crosslinking the polymeric Ce3+/TSCS complex with glutaraldehyde, and releasing the chelated Ce3+ using an eluent solution containing a mixture of EDTA and HNO3. Ce-TSCS had a capacity of 164 ± 1 mg/g and better removal selectivity for Ce3+ because it was smart enough to figure out which target ions would fit into the holes made by Ce3+ during the imprinting process. The kinetic data were well suited to a pseudo-second-order model, and the isotherms were well described by the Langmuir model, both of which pointed to chemisorption and adsorption through Ce3+ chelation. XPS and FTIR analyses demonstrate that the predominant adsorption mechanism is the coordination of Ce3+ with the -NH-, -NH2, and -SH chelating units of the thiosalicylic hydrazidine. These findings provide fresh direction for the development of sorbent materials that can effectively and selectively remove Ce3+ from aqueous effluents.

Enhancement of Ni–Zn ferrite nanoparticles parameters via cerium element for optoelectronic and energy applications

This work is concerned with fabricating ferrite nanoparticles of nickel–zinc with the chemical formula: Ni0.55Zn0.45Fe2−xCexO4, 0 ≤ x ≤ 0.011 by co-deposition technique and modifying their electrical, microscopic, spectroscopic, optical, electrical and dielectric properties as advanced engineering materials through doping with the cerium (Ce) element. XRD patterns displayed that the samples have a monophasic Cerium–Nickel–zinc (CNZ) spinel structure without other impurities for cerium concentration (x) ≤ 0.066. Both values of crystallite size and lattice parameters decrease from 33.643 to 23.137 nm and from 8.385 to 8.353 nm, respectively, with the increasing Ce ions substitution content from 0 to 0.066. SEM images indicate that grains of the fabricated compounds are smaller, more perfect, more homogeneous, and less agglomeration than those of the un-doped Ni–Zn nano-ferrites. The maximum intensity of first-order Raman spectral peaks (Eg, F2g(2), A1g(2), and A1g(1)) of CNZ ferrite nanoparticles are observed at about (330, 475, 650, 695) cm−1, respectively, that confirms the CNZ samples have the cubic spinel structure. The direct and indirect optical energy bandgaps of CNZ samples have a wide spectrum of values from semiconductors to insulators according to cerium concentration. The results showed that the values of dielectric constant, dielectric loss factor, and Ac conductivity and the conductivity transition temperature are sensitive to cerium ions content. AC conductivity exhibited by the CNZ samples has the semiconductor materials behavior, where the AC conductivity increases due to temperature or doping concentration. The results indicate that Ni0.55Zn0.45Fe1.944Ce0.066O4 ferrite nanoparticles may be selected for optoelectronic devices, high-frequency circuits, and energy storage applications.

Ammonium salts of microcrystalline cellulose-g-poly (acrylonitrile): toxicity, antioxidant and anti-inflammatory properties

Cellulose is an excellent starting material for the construction of bioactive polymers. In the present work, we have synthesized quaternized graft copolymers of cellulose and tested their biological properties. Cellulose was grafted with acrylonitrile in a cerium ion catalyzed reaction. High yield of the grafting reaction, 89%, was achieved. Next, the poly (acrylonitrile) chains were aminated using three different amines and finally, the amino functions were quaternized using methyl iodide. In addition to chemical and physical characterization of the polymers, several tests on their bioactive properties have been conducted. The polymers turned out to have good antioxidant properties, as assessed studying how they scavenge ABTS radicals. Anti-inflammatory properties were investigated by a membrane stabilization method. The results showed that the quaternized polymers had anti-inflammatory effects and the one aminated with tris(2-aminoethyl)amine was the most significant compared with indomethacin. The cytotoxicity was evaluated in vitro against HepG2 and WI-38 cell lines. All quaternized polymers showed moderate effects against the cancerous cell line HEPG2. On the other hand, their effect against normal fibroblast WI-38 was weak. The acute toxicity in vivo was evaluated for one of the polymers, for which the LD50 was 6606 mg/kg. The high LD50 indicates the polymer is relatively non-toxic, and will be considered in future for in vivo studies.Graphical abstract

Construction of Ce3+ modified conversion film on oxide scale of plain steel rebars to greatly enhance the corrosion resistance

Steel rebars with oxide scale, which is usually rich of defects, are widely used in industry. On the surface of the oxide scale, it is difficult to prepare a conversion film with desirable corrosion resistance because of the acidity of conventional conversion solutions. In this work, a sol–gel solution (pH = 11) was employed to retard the diffusion of cerium ions avoiding the formation of cerium salt precipitates at room temperature. After treatments, the diffusion of cerium ions would be accelerated and a protective conversion film would form to repair natural defects on oxide scale of steel rebars at a higher temperature. This strategy can not only avoid the peeling of the oxide scale by the acid solution, but also prevent a large amount of non-uniform precipitation of the film-forming Ce3+ ions. The conversion film@oxide scale was characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), potentiodynamic polarization curve (PPC) etc. It is found that the corrosion resistance of the prepared film@oxide scale was enhanced greatly when the concentration of added cerium ion (III) was 0.5 M, with pH adjusted to 11. After 30 days of immersion, Rct of surface treated rebar is more 180 times that of blank sample. The excellent corrosion resistance is closely related to the double-layer structure of the prepared sol-gel film, especially an about 2 nm inner layer of cerium oxide.

Cerium ions immobilized magnetic graphite nitride decorated with L-Alanyl-L-Glutamine as new chelator for enrichment of phosphopeptides.

Cerium ions immobilized magnetic graphite nitride materialhave been prepared using L-Alanyl-L-Glutamine as the new chelator. The resulting Fe3O4/g-C3N4-L-Ala-L-Gln-Ce4+, as an immobilized metal ion affinity chromatography (IMAC) sorbent, was reusable. This is due to the strong coordination interaction between L-Alanyl-L-Glutamine and cerium ions. After a series of characterizations, the magnetic nanocomposite showed high surface area, good hydrophilicity, positive electricity, and magnetic response. Fe3O4/g-C3N4-L-Ala-L-Gln-Ce4+ had high sensitivity (0.1 fmol), selectivity (α-/β-casein/bovine serum albumin, 1:1:5000), and good recyclability (10 cycles). A total of 647 unique phosphopeptides mapped to 491 phosphoproteins were identified from A549 cell lysate by nano LC-MS analysis.

Multiple green spectroscopic methods for erdosteine determination in bulk and dosage form with extensive greenness evaluation

Four simple, sensitive, economical, and eco-friendly spectrophotometric and spectrofluorimetric methods for the assay of erdosteine (ERD) in bulk and dosage form have been developed and validated as per the current ICH guidelines. Method I involved the addition of the powerful oxidizing agent, potassium permanganate to ERD and measuring the oxidation product at 600 nm. Another oxidizing agent; ceric ammonium sulfate was used in Method II where ERD is oxidized resulting in a decline in the absorbance intensity of cerium (IV) ions, measured at 320 nm. Similarly, Method III employed the use of ceric ammonium sulfate, However, the fluorescence intensity of the resulting cerium (III) ions was recorded at λex/λem 255/355 nm, respectively. Whereas in Method IV, ERD was added to acriflavine leading to a proportional decrease in its native fluorescence. Various reaction conditions affecting the intensity of measurement were attentively investigated, optimized, and validated. All the suggested methods did not require any tedious extraction procedures nor organic solvents. The implementation of the proposed methods in ERD assay resulted in linear relationships between the measured signals and the corresponding concentrations of ERD in the range of 1–6, 0.1–1.0, 0.01–0.1, and 10–100 μg/mL with LOD values 0.179, 0.024, 0.0027 and, 3.2 μg/mL for methods I, II, III and IV respectively. The suggested methods were successfully applied to ERD analysis in pure form and in commercial capsules. Furthermore, the eco-friendliness of the proposed methods was thoroughly checked using various greenness testing tools. Lastly, this work, not only presents highly sensitive, green, mix-and-read methods for ERD determination, but also, describes the determination of ERD spectrofluorimetrically for the first time in the literature.

Comprehensive Improvement of Various Features of Cu-Cd Ferrites (Cu0.5Cd0.5Fe2-xCexO4) by Cerium (Ce3+) Ion Substitution.

Cerium (Ce3+) substitution in Cu-Cd spinel nanoferrites with the compositional formula Cu0.5Cd0.5Fe2-xCexO4 (x = 0.0, 0.0125, 0.0250, 0.0375, 0.050) was performed by the hydrothermal route. The structural, morphological, optical, electrical, and dielectric properties of Ce-substituted Cu-Cd ferrites were explored. X-ray diffraction revealed the single-phase cubic structure of all nanoferrites. The average crystallite size (72.42-11.61 nm) and lattice constant (8.419-8.449 Å) were observed for the synthesized ferrites. The surface shapes of particles were determined by scanning electron microscopy. The substitution was also verified by Fourier transform infrared spectroscopy and ultraviolet-visible spectrophotometry. The semiconducting behavior of ferrites was determined from their electrical properties, such as direct current (DC) electrical resistivity. The Curie temperature was observed at 523 K temperature for all nanoferrites. The dielectric constant and dielectric loss significantly indicated the reducing behavior with an increase in the cerium concentration. The sample Cu0.5Cd0.5Fe1.975Ce0.025O4 resulted in the lowest optical bandgap energy, DC resistivity, and dielectric losses. The nature of the electrical resistivity and dielectric constants indicate that the designed materials are highly appropriate for the design of microwave gadgets.

Structure and tunable white-light emission of the Ce3+/Dy3+ co-doped MgO–K2O–B2O3–P2O5 borophosphate glasses by modulating Mg/K ratio

In this work, the Ce3+/Dy3+ co-doped MgO–K2O–B2O3–P2O5 borophosphate glasses were successfully fabricated by the melt-quenching technique. The structure and optical characteristics were investigated using XRD, DSC, FTIR, Raman spectra, transmittance spectra and photoluminescence (PL) spectra. With increasing Mg/K ratio, the free oxygen introduced by MgO as its contents increase facilitated the conversion of [BO3] triangular units to the denser [BO4] tetrahedral units. The phonon energy of the glass system was estimated to be about 1020 cm−1 from the Raman spectra. Spectroscopic analysis revealed the energy transfer (ET) between Ce3+ and Dy3+ may exist, and the ET between Ce3+ and Dy3+ was explored in detail. Under 315 and 349 nm excitation, the PL spectra disclosed three distinct emission peaks at about 370, 484, and 575 nm, which corresponded to the 5d-4f (Ce3+), 4F9/2 → 6H15/2 (Dy3+), and 4F9/2 → 6H13/2 transitions (Dy3+), respectively. The blue shift in the peak position of the cerium ions within the excitation and emission spectra was associated with the decrease in the overall optical basicity of the glass caused by compositional modulation. Tunable white light emission can be achieved by varying the excitation wavelength. Under 349 nm excitation, the optimum chromaticity coordinate (0.325, 0.333) with a correlated color temperature value of 5856 K is obtained at the Mg/K ratio of 3:2, which points to the Ce3+/Dy3+ co-doped MgO–K2O–B2O3–P2O5 borophosphate glasses are a prospective fluorescent material for exploitation of white light-emitting diodes (WLEDs).

Influence of CeO2 on glass formation, structural and thermal properties of sodium niobium phosphate glass

Cerium is a well-known surrogate to trivalent and tetravalent actinides and has been investigated to explore the structural and thermal characteristics of simulated radwaste-loaded material systems. The solubility and distribution of CeO2 into a sodium niobium phosphate glass have been explored with the objective of developing a host matrix for radioactive waste immobilization. Niobium phosphate glasses of (100-x) (40Na2O–20Nb2O5–40P2O5)-xCeO2 (x = 0, 1, 3, 5, 8, and 10 mol%) compositions are prepared by melt-quenching method and are characterized by X-ray diffractometry (XRD), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and scanning electron microscopy (SEM). This study summarises the influence of cerium ion incorporation on the structure, thermal stability, and formation of crystalline phases of the niobium phosphate glass. The various glass stability parameters, such as Hruby (KH), Weinberg (KW), and Lu–Liu (KLL) parameters are estimated to assess the stability of the glass melt against devitrification in the supercooled region. The spectroscopic analysis ascertains the presence of metaphosphate and pyrophosphate networks as primary structural building units in the glass. However, the Raman analysis demonstrates the influence of CeO2 on the network linkages arising from the corner-sharing of NbO6 octahedrons and Nb–O–P bonding in the glass. The CeO2 loading is optimized up to 8 mol% into the base 40Na2O–20Nb2O5–40P2O5 glass matrix without precipitation of any crystalline phase. The glasses are heat treated to obtain glass-ceramics embedded with the crystalline phases, namely, monazite CePO4, NbOPO4, NaNbO3, and niobium phosphate bronze Na6Nb8(PO4)5O15. The microanalysis of these glass ceramics shows that the CeO2 is more aggregated inside the niobium phosphate bronze framework than in the bulk at a higher temperature. It is also observed that the surface crystallization process is a prevalent mechanism for the crystallization of glasses on heating at crystallization onset temperature.

Monolayers of bottlebrush amphiphilic polymers and their mixed monolayers with dihexadecyl phosphate at the air–water interface. The effect of cerium (III) ions and quaternization of polymers

Monolayers of bottlebrush amphiphilic polymers and their mixed monolayers with dihexadecyl phosphate at the air–water interface. The effect of cerium (III) ions and quaternization of polymers

A switch from ferro- to antiferromagnetic ordering in the solid solutions CeAuGe1−x Sn x

Abstract CeAuGe and CeAuSn (both NdPtSb type, space group P63 mc) form a complete solid solution CeAuGe1−x Sn x with Vegard-type behavior of the cell volume. Samples with steps of x = 0.1 were synthesized from the pure elements by arc-melting. The structure of CeAuGe0.13(2)Sn0.87(2) was refined from single-crystal X-ray diffractometer data: a = 469.10(6), c = 773.90(10) pm, wR 2 = 0.0359, 251 F 2 values and 12 variables. The induced structural disorder caused by the Ge/Sn mixing affects the magnetic ground state of the cerium ions. From the germanium-rich side, the Curie temperature of CeAuGe (10.0 K) decreases towards CeAuGe0.6Sn0.4, while the Néel temperature of CeAuSn (4.4 K) decreases at the tin-rich side toward CeAuGe0.4Sn0.6. The switch of the magnetic ground state occurs approximately around the Ge/Sn ratio of 1:1. 119Sn Mössbauer spectra of CeAuGe0.1Sn0.9 and CeAuGe0.7Sn0.3 confirm the presence of single crystallographic tin sites in both cases, and the isomer shifts are comparable to that of pure CeAuSn, indicating similar electron density distribution at the tin nuclei.

Characterization of YAG:Ce ceramics with graphene oxide

Yttrium-aluminum garnet (Y3Al5O12) is an optical material that shows great potential due to its favorable light-emitting and mechanical properties, as well as its chemical stability and thermal resistance. It is commonly utilized in laser technology, optical instruments, and solid-state light sources as a result of its activation by transition metal or rare earth element ions. In this work, experiments were carried out on the procedure for compacting samples of luminescent ceramics Y3Al5O12:Ce3+, by single-base pressing followed by sintering. Comprehensive studies of the influence of graphene oxide of variable concentration (x=0.1;0.5; 1 wt.%) on the radiative characteristics of ceramic samples. It was found that the addition of graphene oxide in an amount from 0.1 to 1 wt. % affects the density and luminescent properties of YAG:Ce ceramics. There is a decrease in the value of the density parameter at concentrations of graphene oxide 0.1-1 wt. % before annealing, after annealing, the relative density value increases to ~99 %. The luminescence spectrum when excited by a blue LED chip appears as a wide band in the spectral range 460-750, the nature of which is associated with radiative transitions in the cerium ion. It has been established that the light-emitting characteristics have a downward trend when activated by graphene oxide. The integral luminescence intensity decreases from 27.1 % to 19 % with an increase in the concentration of graphene oxide.

Pressure-Induced Coordination Number Transition in Lanthanide Mellitate Coordination Polymers: Structure and Spectroscopy.

High external pressure is found to induce a non-coordinated water molecule to bond to cerium in a previously studied mellitate coordination polymer, as determined by high-pressure single-crystal X-ray diffraction, resulting in a coordination number transition at 3.85 GPa from 9 to 9.5 where half the cerium ions are 10-coordinate. Also, bond length changes due to increased pressure are experimentally measured, whereas the cerium-carboxylate bond lengths overall change by -0.004(9) Å/GPa, the cerium-water bonds by -0.016(3) Å/GPa, and cerium-oxygen bonds overall by -0.010(6) Å/GPa, which corresponds well with theoretical bond length decreases determined for similar compounds. The high-pressure absorbance spectra of the analogous neodymium mellitate are examined and compared with the structural changes observed.

Interaction of Cerium Oxide Nanoparticles and Ionic Cerium with Duckweed (Lemna minor L.): Uptake, Distribution, and Phytotoxicity.

As one of the most widely used nanomaterials, CeO2 nanoparticles (NPs) might be released into the aquatic environment. In this paper, the interaction of CeO2 NPs and Ce3+ ions (0~10 mg/L) with duckweed (Lemna minor L.) was investigated. CeO2 NPs significantly inhibited the root elongation of duckweed at concentrations higher than 0.1 mg/L, while the inhibition threshold of Ce3+ ions was 0.02 mg/L. At high doses, both reduced photosynthetic pigment contents led to cell death and induced stomatal deformation, but the toxicity of Ce3+ ions was greater than that of CeO2 NPs at the same concentration. According to the in situ distribution of Ce in plant tissues by μ-XRF, the intensity of Ce signal was in the order of root > old frond > new frond, suggesting that roots play a major role in the uptake of Ce. The result of XANES showed that 27.6% of Ce(IV) was reduced to Ce(III) in duckweed treated with CeO2 NPs. We speculated that the toxicity of CeO2 NPs to duckweed was mainly due to its high sensitivity to the released Ce3+ ions. To our knowledge, this is the first study on the toxicity of CeO2 NPs to an aquatic higher plant.

Osteogenesis and cytocompatibility compression of cerium and gallium doped mesoporous bioactive glass-ceramics

Bone defects have recently become one of the biggest problems for surgeons. This study aims to compression osteogenic properties of cerium and gallium doping in mesoporous bioactive glass-ceramics (MBGCs). MBGCs are synthesized using sol-gel method through evaporation induced self-assembly technique. Small-angle X-ray scattering (SAXS) revealed size of nanoparticle in MBGCs is ∼29 nm. The impact of cerium and gallium ions on ceramics was characterized using Fourier transform infrared (FTIR) and 29Si Magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopic methods. Images of samples taken with a transmission electron microscope show aggregated particles with irregular forms. MBGCs doped with cerium and gallium in vitro biocompatibility investigations do not show any cytotoxicity towards MG63 cells and also have considerably improved osteogenic properties. Overall, Ga doped MBGCs with desired osteogenesis properties compared to Ce doped MBGCs, and Ga doped MBGCs offers encouraging possibilities for the effective repair of bone fractures with implants.

Extracting light rare earth elements by applying electric field assisted mining technique

Light rare earth elements are critical raw materials that present several applications, including the use in the manufacturing of high-tech products and green energy production systems. Considering their criticality, there is a need to increase the production of these commodities. The electric field assisted mining is an eco-friendly technique that uses the electrokinetic phenomena to remove metallic species from soils. Considering that electric field strength and electrolyte concentration are key factors that directly influence the species extraction via the electrokinetic process, the aim of the present work was to evaluate the effect of these variables on the removal of the cerium, lanthanum, and neodymium ions. To that end, a full factorial design was conducted to assist in statistical analysis, and response surfaces were built aiming to analyze the rare earths removal. The results showed that the main effects of electric field strength and electrolyte concentration presented individually a positive effect on the removal of the species. In addition, the neodymium removal also presented the interaction effect between the variables in the analysis. The experiment that showed the best performance was conducted using acetic acid at 0.1 mol L−1 and an electric field of 1.0 V cm−1, resulting in a mining efficiency of 78.5% of Ce4+, 47.7% of La3+ and 35.1% of Nd3+, with an energy consumption of 6.5 W h after 240 h of experiment. Regarding these results, and also taking into account the use of weak and organic acid and mild experiments conditions, electric field assisted mining presents itself as a feasible and eco-friendly technique to remove rare earth elements from soils.

Defective S‐TiO2−x/CeO2 Heterojunction for Mutual Reinforcing Chemodynamic/Sonocatalytic Antibacterial Therapy and Sonoelectric/Ion‐Activated Bone Regeneration

AbstractSonocatalysis and chemodynamics have attracted widespread attention in antibacterial therapy. The transfer efficiency of electrons plays an important role in sonocatalysis and chemodynamics, and how to regulate electron transfer and achieve mutual‐reinforcement between sonocatalysis and chemodynamic to achieve efficient antibacterial therapy is a difficult problem. Here, this study develops a defective S‐doped TiO2 and CeO2 heterojunction(S‐TiO2−x/CeO2）sonosensitizer that can enhance chemodynamic therapy by regulating valence transitions of CeIII/CeIV by sonoelectrons, and enhancing sonocatalytic therapy by creating heterojunctions to accelerate the transfer of interface electron, thereby achieving mutual reinforcement of sonocatalysis and chemodynamic. It could kill 99.3% of S. aureus under ultrasound (US) irradiation . Due to the presence of mixed valence states CeIII/CeIV in CeO2, S‐TiO2−x/CeO2 could be as oxy‐substrates. Ce4+ can deplete glutathione and reacts with H2O2 in bacteria to produce reactive oxygen species (ROS). These activities combines with ROS generated from sonocatalysis, resulting in bacterial death. Meanwhile, the electrical signal generated by S‐TiO2−x/CeO2 under US stimulation and the cerium ions could activate the Wnt/β‐catenin signaling pathway to induce hBMSCs to differentiate into osteoblast. S‐TiO2−x/CeO2 successfully treats osteomyelitis under US irradiation by effectively clearing infection, suppressing inflammatory, and promoting bone regeneration, and it provides effective treatment for patients with deep infection.

"Off/On” Fluorescent Probe based on Aggregation-Induced Quenching of ZnO-Quantum dots for Determination of Ara-C: Pharmacokinetic Applications, Adsorption Kinetics & Green Profile Assessment

Herein, a turn “Off/On” fluorescence probe based on ZnO quantum dots (ZnO-QDs) has been proposed and successfully utilized for the determination of Ara-C (cytarabine) using ceric ions (Ce4+) as quencher and ethylenediamine (ED) as a linker. The probe is based initially on the quenching effect of Ce4+ ions on the strong native fluorescence of ZnO-QDs forming the Turn Off system (Ce@ZnO-QDs) that believed to occur due to the aggregation-induced quenching (AIQ) mechanism. The second step is the addition of Ara-C in the presence of ethylenediamine (ED) that encourages the formation of Ara-C/ED/Ce4+ as well as the release of the free ZnO-QDs, leading to the recovery of the fluorescence intensity. The developed sensing platform shows a linear response towards Ara-C over the range of 10 to 1000 ng mL−1 giving a limit of detection (LOD) and limit of quantitation (LOQ) of 1.22 ng mL−1 and 3.70 ng mL−1, respectively. A dispersive magnetic solid phase micro-extraction (dMSPE) method was developed and optimized for the extraction of Ara-C in spiked human plasma using thiol-modified magnetite nanoparticles (S-MNPs). The proposed platform exhibits good sensitivity toward Ara-C in the presence of different interfering substances. Excellent recoveries are obtained after spiking different concentrations of Ara-C into rabbit plasma samples. The validated experimental parameters have been successfully applied to monitor the pharmacokinetic profile of Ara-C in rabbit plasma. A detailed adsorption kinetics study has been carried out to provide a deep insight into the adsorption behavior of Ara-C on the thiol-doped-magnetite nanoparticles. The greenness assessment of the proposed method was achieved and compared with other reported methods using two tools of greenness; the green analytical procedure index (GAPI) and the analytical greenness calculator AGREE.

Nacre-mimetic cerium-doped nano-hydroxyapatite/chitosan layered composite scaffolds regulate bone regeneration via OPG/RANKL signaling pathway

Autogenous bone grafting has long been considered the gold standard for treating critical bone defects. However, its use is plagued by numerous drawbacks, such as limited supply, donor site morbidity, and restricted use for giant-sized defects. For this reason, there is an increasing need for effective bone substitutes to treat these defects. Mollusk nacre is a natural structure with outstanding mechanical property due to its notable “brick-and-mortar” architecture. Inspired by the nacre architecture, our team designed and fabricated a nacre-mimetic cerium-doped layered nano-hydroxyapatite/chitosan layered composite scaffold (CeHA/CS). Hydroxyapatite can provide a certain strength to the material like a brick. And as a polymer material, chitosan can slow down the force when the material is impacted, like an adhesive. As seen in natural nacre, the combination of these inorganic and organic components results in remarkable tensile strength and fracture toughness. Cerium ions have been demonstrated exceptional anti-osteoclastogenesis capabilities. Our scaffold featured a distinct layered HA/CS composite structure with intervals ranging from 50 to 200 μm, which provided a conducive environment for human bone marrow mesenchymal stem cell (hBMSC) adhesion and proliferation, allowing for in situ growth of newly formed bone tissue. In vitro, Western-blot and qPCR analyses showed that the CeHA/CS layered composite scaffolds significantly promoted the osteogenic process by upregulating the expressions of osteogenic-related genes such as RUNX2, OCN, and COL1, while inhibiting osteoclast differentiation, as indicated by reduced TRAP-positive osteoclasts and decreased bone resorption. In vivo, calvarial defects in rats demonstrated that the layered CeHA/CS scaffolds significantly accelerated bone regeneration at the defect site, and immunofluorescence indicated a lowered RANKL/OPG ratio. Overall, our results demonstrate that CeHA/CS scaffolds offer a promising platform for bone regeneration in critical defect management, as they promote osteogenesis and inhibit osteoclast activation.

The Role of Cerium Valence in the Conversion Temperature of H2Ti3O7 Nanoribbons to TiO2-B and Anatase Nanoribbons, and Further to Rutile.

CeO2-TiO2 is an important mixed oxide due to its catalytic properties, particularly in heterogeneous photocatalysis. This study presents a straightforward method to obtain 1D TiO2 nanostructures decorated with CeO2 nanoparticles at the surface. As the precursor, we used H2Ti3O7 nanoribbons prepared from sodium titanate nanoribbons by ion exchange. Two cerium sources with an oxidation state of +3 and +4 were used to obtain mixed oxides. HAADF-STEM mapping of the Ce4+-modified nanoribbons revealed a thin continuous layer at the surface of the H2Ti3O7 nanoribbons, while Ce3+ cerium ions intercalated partially between the titanate layers. The phase composition and morphology changes were monitored during calcination between 620 °C and 960 °C. Thermal treatment led to the formation of CeO2 nanoparticles on the surface of the TiO2 nanoribbons, whose size increased with the calcination temperature. The use of Ce4+ raised the temperature required for converting H2Ti3O7 to TiO2-B by approximately 200 °C, and the temperature for the formation of anatase. For the Ce3+ batch, the presence of cerium inhibited the conversion to rutile. Analysis of cerium oxidation states revealed the existence of both +4 and +3 in all calcined samples, regardless of the initial cerium oxidation state.