Dietary Supplementation of Chromium Can Alleviate Negative Impacts of Heat Stress on Performance,Carcass Yield,and Some Blood Hematology and Chemistry Indices of Growing Japanese Quail

Ideal coatings for orthopedic implants should be able to induce excellent osseointegration with host bone tissue, which requires good osteogenic responses and limited inflammatory reactions. Cerium oxide (CeO₂) ceramics have anti-oxidative properties and can be used to decrease mediators of inflammation, making them attractive for biomedical application. In this study, two kinds of CeO₂ incorporated calcium silicate coatings (CS-10Ce and CS-30Ce) were prepared via plasma spraying technique, and the effects of CeO₂ addition on the responses of bone mesenchymal stem cells (BMSCs) and RAW264.7 macrophages were evaluated. The CS-10Ce and CS-30Ce coatings were characterized by X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy. An increase in CeO₂ content in the coatings resulted in enhanced chemical stability and better BMSCs osteogenic behaviors in terms of cell adhesion, proliferation, ALP activity, and mineralized nodule formation. With respect to either ZrO₂-added or unmodified CS coating, the CS-30Ce coating elicited higher effects on the macrophages, suppressing the gene expressions of pro-inflammatory (M1) markers (CCR7, IL-6, and TNF-α), while upregulating the expressions of anti-inflammatory (M2) markers (CD206, IL-1ra, and IL-10); moreover, it could also increase the expression of osteoinductive molecules (BMP2 and TGF-β1) by the macrophages. The results suggested that the regulation of BMSCs behaviors and macrophage-mediated responses at the coating’s surface was related to CeO₂ incorporation. The incorporation of CeO₂ in CS coatings can be a valuable strategy to promote osteogenic responses and mitigate inflammatory reactions.     

Decomposition of water by cerium oxide of δ-phase

Reduced cerium dioxide (CeO_2?x) can reduce water, producing hydrogen at ?298 K. Kinetic studies were focused on the stoichiometric reaction of δ-phase cerium oxide (CeO_1.818) with water vapor. Different activation energies of 18.1 and 33.4 kJ mol^?1 were observed for the reactions at the temperature ranges above and below ca. 453 K, respectively. Rate equations observed in the two temperature ranges were also different. These results strongly suggest that the rate-determining steps are different between the two temperature ranges. Rapid oxygen exchange observed between H₂¹⁸O and lattice oxygen in cerium oxide of δ- phase at ? 298 K indicated that neither the adsorption of water molecules not the diffusion of oxygen ions in the bulk of the oxide can be the rate-determining step. H₂D₂ exchange occurred rapidly at 373 K compared to the rate of water decomposition, suggesting that the recombination of hydrogen atoms on the surface is not rate- determining either. A tentative reaction mechanism was proposed to explain the results of the kinetic studies. The rate-determining step at high temperatures (>453 K) is the reduction of OH^? by the six-coordinated Ce³⁺ which is present in the nonstoichiometric cerium oxide, while that at low temperatures (<453 K) is the subsequent reduction of H⁺ by the seven-coordinated Ce³⁺.     

Various physicochemical and surface properties controlling the bioactivity of cerium oxide nanoparticles

Amidst numerous emerging nanoparticles, cerium oxide nanoparticles (CNPs) possess fascinating pharmacological potential as they can be used as a therapeutic for various oxidative stress-associated chronic diseases such as cancer, inflammation and neurodegeneration due to unique redox cycling between Ce³⁺ and Ce⁴⁺ oxidation states on their surface. Lattice defects generated by the formation of Ce³⁺ ions and compensation by oxygen vacancies on CNPs surface has led to switching between CeO₂ and CeO_2–x during redox reactions making CNPs a lucrative catalytic nanoparticle capable of mimicking key natural antioxidant enzymes such as superoxide dismutase and catalase. Eventually, most of the reactive oxygen species and nitrogen species in biological system are scavenged by CNPs via an auto-regenerative mechanism in which a minimum dose can exhibit catalytic activity for a longer duration. Due to the controversial outcomes on CNPs toxicity, considerable attention has recently been drawn towards establishing relationships between the physicochemical properties of CNPs obtained by different synthesis methods and biological effects ranging from toxicity to therapeutics. Unlike non-redox active nanoparticles, variations in physicochemical properties and the surface properties of CNPs obtained from different synthesis methods can significantly affect their biological activity (inactive, antioxidant, or pro-oxidant). Moreover, these properties can influence the biological identity, cellular interactions, cellular uptake, biodistribution, and therapeutic efficiency. This review aims to highlight the critical role of various physicochemical and the surface properties of CNPs controlling their biological activity based on 165 cited references.     

Comparison between 8‐prenylnarigenin and narigenin concerning their activities on promotion of rat bone marrow stromal cells’ osteogenic differentiation in vitro

A number of recent studies have suggested that flavonols (a class of phytochemical with many biological activities), might exert protective effects against post‐menopausal bone loss. In the present study, we compared naringenin (NG) and 8‐prenylnaringenin (PNG), two major naturally occurring flavonols, on in vitro differentiation of osteoblasts and bone resorbing activity, of rat bone marrow stromal cells (BMSCs). Our results indicated that both compounds, at 10^?6 m , enhanced BMSCs’ differentiation. Then effects of the two compounds at 10^?6 m on ALP activity, osteocalcin secretion and calcium deposition, were compared over a time course. Numbers and areas of colonies stained for ALP (CFU‐F_ALP) expression, and mineralized bone nodules, were histochemically analysed after 12 days and 16 days osteogenic induction, respectively. Expression of BMP‐2, OPG, OSX, RUNX‐2 genes and p38MAPK protein were examined using real‐time PCR and western blotting, respectively. The data presented indicate that PNG, significantly enhanced the rat BMSCs’ differentiation and mineralization through the BMP‐2/p38MAPK/Runx2/Osterix signal pathway, greater than did NG. In conclusion, PNG has a more pronounced ability to enhance osteoblast differentiation and mineralization, than NG.     

Enhanced photocatalytic activity of ceria-doped zinc oxide under UV illumination prepared via chemical precipitation

Transition metal oxide has emerged as one of the most potential candidates for environment remediation by utilizing solar energy through photocatalysis. This study compares the optical characteristics of zinc oxide (ZnO) and ceria-doped zinc oxide (CeZnO) nanoparticles synthesized through a facile chemical precipitation method without using any assistant catalyst. The present work investigates the consequences of ceria (cerium dioxide, CeO₂) intrusion on the photocatalytic activity of ZnO nanoparticles using methylene blue (MB) as a probe pollutant. The CeZnO showed an increase in photoactivity when compared to ZnO nanoparticles for degradation of MB in an aqueous solution under ultraviolet (UV) irradiance. The resulting heterojunction between ZnO and that of ceria enhances the charge separation efficiency showing a strong correlation between ZnO and CeO₂ heterojunction on the charge transfer mechanism across the interface.     

Bone morphogenetic protein 2 promotes osteogenesis of bone marrow stromal cells in type 2 diabetic rats via the Wnt signaling pathway

Type 2 diabetes mellitus impairs osteogenesis in bone marrow stromal cells (BMSCs). Bone morphogenetic protein 2 (BMP2) has been extensively applied for bone defect restoration and has been shown to activate the Wnt signaling pathway. The objective of this study was to investigate the effects of BMP2 on the cell proliferation and osteogenesis of type 2 diabetic BMSCs in rats and explore whether BMP2 induced osteogenesis via the stimulation of Wnt signaling pathway. The cell experiments were divided into DM (diabetic BMSCs), BMP25 (induced with 25 ng/ml BMP2), BMP100 (induced with 100 ng/ml BMP2) and BMP25  + XAV groups. All cells with or without the different concentrations of BMP2 were cultured under the same experimental conditions. The in vitro results indicated that BMP2 enhanced cell proliferation by 130%–157% and osteogenic differentiation by approximately two-fold in type 2 diabetic BMSCs. The expression levels of β-catenin, cyclin D1, Runx2 and c-myc related to the Wnt signaling pathway were also upregulated from 180% to 212% in BMP2-induced type 2 diabetic rat BMSCs, while the level of GSK3β decreased to 43%. In BMP2-induced type 2 diabetic BMSCs with calcium phosphate cement (CPC) scaffolds for osteoblast study in vivo, the appearance of newly formed bone dramatically increased to 175% compared with type 2 diabetic BMSCs. These data demonstrated that BMP2 enhanced bone regeneration in diabetic BMSCs by stimulating the Wnt signaling pathway with the accumulation of β-catenin and the depressed expression of GSK3β. Diabetic BMSCs associated with BMP2 might be a potential tissue-engineered construct for bone defects in type 2 diabetes mellitus.     

Effects of recombinant adeno-associated viral vectors on angiopoiesis and osteogenesis in cultured rabbit bone marrow stem cells via co-expressing hVEGF and hBMP genes: A preliminary study in vitro

Objective

VEGF and BMP play important roles in angiogenesis and osteogenesis. Combining these two factors may be a promising therapeutic strategy for avascular necrosis of the femoral head (ANFH).

Methods

Rabbit bone marrow-derived mesenchymal stem cells (BMSCs) were isolated and purified by density gradient centrifugation combined with attachment culture methods. The purity and characteristics of the BMSCs were detected by cell surface antigen identification. The best MOI of BMSCs transfected with rAAV was detected by fluorescent cell counting, and cell viability was determined by MTT assay. Expression of the genes of interest was detected by GFP gene expression, RT-PCR assay, and ELISA assay. The biological activities of VEGF and BMP were detected by angiogenic and osteogenic assays.

Results

The best MOI of BMSCs transfected with rAAV was 5 × 10⁴ v.g./cell. Cell growth curves showed vigorous cell viability. Expressions of the GFP, VEGF165, and BMP₇ genes were detected 1 day post-transfection and peaked 14 days post-transfection. Expression of the genes of interest was sustained over 1 month. VEGF and BMP proteins secreted from BMSCs transfected with rAAV-hVEGF₁₆₅-IRES-hBMP₇ enhanced angiogenesis and osteogenesis in vitro.

Conclusion

Recombinant adeno-associated viral vectors co-expressing the hVEGF₁₆₅ and hBMP₇ genes showed efficient gene expression ability. The VEGF₁₆₅ and BMP₇ proteins expressed from the vector have efficient biological activity in vitro.     

Cerium Oxide Decorated Polymer Nanofibers as Effective Membrane Reinforcement for Durable,High‐Performance Fuel Cells

High‐power, durable composite fuel cell membranes are fabricated here by direct membrane deposition (DMD). Poly(vinylidene fluoride‐co ‐hexafluoropropylene) (PVDF‐HFP) nanofibers, decorated with CeO₂ nanoparticles are directly electrospun onto gas diffusion electrodes. The nanofiber mesh is impregnated by inkjet‐printed Nafion ionomer dispersion. This results in 12 µm thin multicomponent composite membranes. The nanofibers provide membrane reinforcement, whereas the attached CeO₂ nanoparticles promote improved chemical membrane durability due to their radical scavenging properties. In a 100 h accelerated stress test under hot and dry conditions, the reinforced DMD fuel cell shows a more than three times lower voltage decay rate (0.39 mV h^?1) compared to a comparably thin Gore membrane (1.36 mV h^?1). The maximum power density of the DMD fuel cell drops by 9%, compared to 54% measured for the reference. Impedance spectroscopy reveals that ionic and mass transport resistance of the DMD fuel cell are unaffected by the accelerated stress test. This is in contrast to the reference, where a 90% increase of the mass transport resistance is measured. Energy dispersive X‐ray spectroscopy reveals that no significant migration of cerium into the catalyst layers occurs during degradation. This proves that the PVDF‐HFP backbone provides strong anchoring of CeO₂ in the membrane.     

Cerium oxide nanoparticles as potential antibiotic adjuvant. Effects of CeO2 nanoparticles on bacterial outer membrane permeability

BackgroundTherapeutic options against Multi Drug Resistant (MDR) pathogens are limited and the overall strategy would be the development of adjuvants able to enhance the activity of therapeutically available antibiotics. Non-specific outer membrane permeabilizer, like metal-oxide nanoparticles, can be used to increase the activity of antibiotics in drug-resistant pathogens. The study aims to investigate the effect of cerium oxide nanoparticles (CeO₂ NPs) on bacterial outer membrane permeability and their application in increasing the antibacterial activity of antibiotics against MDR pathogens.MethodsThe ability of CeO₂ NPs to permeabilize Gram-negative bacterial outer membrane was investigated by calcein-loaded liposomes. The extent of the damage was evaluated using lipid vesicles loaded with FITC-dextran probes. The effect on bacterial outer membrane was evaluated by measuring the coefficient of permeability at increasing concentrations of CeO₂ NPs. The interaction between CeO₂ NPs and beta-lactams was evaluated by chequerboard assay against a Klebsiella pneumoniae clinical isolate expressing high levels of resistance against those antibiotics.ResultsCalcein leakage increases as NPs concentrations increase while no leakage was observed in FITC-dextran loaded liposomes. In Escherichia coli the outer membrane permeability coefficient increases in presence of CeO₂ NPs. The antibacterial activity of beta-lactam antibiotics against K. pneumoniae was enhanced when combined with NPs.ConclusionsCeO₂ NPs increases the effectiveness of antimicrobials which activity is compromised by drug resistance mechanisms. The synergistic effect is the result of the interaction of NPs with the bacterial outer membrane. The low toxicity of CeO₂ NPs makes them attractive as antibiotic adjuvants against MDR pathogens.     

Variability in Bioreactivity Linked to Changes in Size and Zeta Potential of Diesel Exhaust Particles in Human Immune Cells

Acting as fuel combustion catalysts to increase fuel economy, cerium dioxide (ceria, CeO₂) nanoparticles have been used in Europe as diesel fuel additives (Envirox™). We attempted to examine the effects of particles emitted from a diesel engine burning either diesel (diesel exhaust particles, DEP) or diesel doped with various concentrations of CeO₂ (DEP-Env) on innate immune responses in THP-1 and primary human peripheral blood mononuclear cells (PBMC). Batches of DEP and DEP-Env were obtained on three separate occasions using identical collection and extraction protocols with the aim of determining the reproducibility of particles generated at different times. However, we observed significant differences in size and surface charge (zeta potential) of the DEP and DEP-Env across the three batches. We also observed that exposure of THP-1 cells and PBMC to identical concentrations of DEP and DEP-Env from the three batches resulted in statistically significant differences in bioreactivity as determined by IL-1β, TNF-α, IL-6, IFN-γ, and IL-12p40 mRNA (by qRT-PCR) and protein expression (by ELISPOT assays). Importantly, bioreactivity was noted in very tight ranges of DEP size (60 to 120 nm) and zeta potential (−37 to −41 mV). Thus, these physical properties of DEP and DEP-Env were found to be the primary determinants of the bioreactivity measured in this study. Our findings also point to the potential risk of over- or under- estimation of expected bioreactivity effects (and by inference of public health risks) from bulk DEP use without taking into account potential batch-to-batch variations in physical (and possibly chemical) properties.     

Role of ecto-NTPDases on UDP-sensitive P2Y(6) receptor activation during osteogenic differentiation of primary bone marrow stromal cells from postmenopausal women

This study aimed at investigating the expression and function of uracil nucleotide‐sensitive receptors (P2Y₂, P2Y₄, and P2Y₆) on osteogenic differentiation of human bone marrow stromal cells (BMSCs) in culture. Bone marrow specimens were obtained from postmenopausal female patients (68 ± 5 years old, n = 18) undergoing total hip arthroplasty. UTP and UDP (100 µM) facilitated osteogenic differentiation of the cells measured as increases in alkaline phosphatase (ALP) activity, without affecting cell proliferation. Uracil nucleotides concentration‐dependently increased [Ca²⁺]_i in BMSCs; their effects became less evident with time (7 > 21 days) of the cells in culture. Selective activation of P2Y₆ receptors with the stable UDP analog, PSB 0474, mimicked the effects of both UTP and UDP, whereas UTPγS was devoid of effect. Selective blockade of P2Y₆ receptors with MRS 2578 prevented [Ca²⁺]_i rises and osteogenic differentiation caused by UDP at all culture time points. BMSCs are immunoreactive against P2Y₂, P2Y₄, and P2Y₆ receptors. While the expression of P2Y₆ receptors remained fairly constant (7～21 days), P2Y₂ and P2Y₄ became evident only in less proliferative and more differentiated cultures (7 < 21 days). The rate of extracellular UTP and UDP inactivation was higher in less proliferative and more differentiated cell populations. Immunoreactivity against NTPDase1, ‐2, and ‐3 rises as cells differentiate (7 < 21 days). Data show that uracil nucleotides are important regulators of osteogenic cells differentiation predominantly through the activation of UDP‐sensitive P2Y₆ receptors coupled to increases in [Ca²⁺]_i. Endogenous actions of uracil nucleotides may be balanced through specific NTPDases determining whether osteoblast progenitors are driven into proliferation or differentiation. J. Cell. Physiol. 227: 2694–2709, 2012. © 2011 Wiley Periodicals, Inc.     

Gentiopicroside promotes the osteogenesis of bone mesenchymal stem cells by modulation of β-catenin-BMP2 signalling pathway

Osteoporosis is characterized by increased bone fragility, and the drugs used at present to treat osteoporosis can cause adverse reactions. Gentiopicroside (GEN), a class of natural compounds with numerous biological activities such as anti-resorptive properties and protective effects against bone loss. Therefore, the aim of this work was to explore the effect of GEN on bone mesenchymal stem cells (BMSCs) osteogenesis for a potential osteoporosis therapy. In vitro, BMSCs were exposed to GEN at different doses for 2 weeks, whereas in vivo, ovariectomized osteoporosis was established in mice and the therapeutic effect of GEN was evaluated for 3 months. Our results in vitro showed that GEN promoted the activity of alkaline phosphatase, increased the calcified nodules in BMSCs and up-regulated the osteogenic factors (Runx2, OSX, OCN, OPN and BMP2). In vivo, GEN promoted the expression of Runx2, OCN and BMP2, increased the level of osteogenic parameters, and accelerated the osteogenesis of BMSCs by activating the BMP pathway and Wnt/β-catenin pathway, effect that was inhibited using the BMP inhibitor Noggin and Wnt/β-catenin inhibitor DKK1. Silencing the β-catenin gene and BMP2 gene blocked the osteogenic differentiation induced by GEN in BMSCs. This block was also observed when only β-catenin was silenced, although the knockout of BMP2 did not affect β-catenin expression induced by GEN. Therefore, GEN promotes BMSC osteogenesis by regulating β-catenin-BMP signalling, providing a novel strategy in the treatment of osteoporosis.     

Interfacial Super‐Assembled Porous CeO2/C Frameworks Featuring Efficient and Sensitive Decomposing Li2O2 for Smart Li–O2 Batteries

The Li–O₂ battery (LOB) represents a promising candidate for future electric vehicles owing to its outstanding energy density. However, the practical application of LOB cells is largely blocked by the poor cycling performance of cathode materials. Herein, an ultralong 440‐cycle life of an LOB cell is achieved using CeO₂ nanocubes super‐assembled on an inverse opal carbon matrix as the cathode material without any additives. CeO₂ is proved to be effective for the complete and sensitive decomposition of loosely stacked Li₂O₂ films during the oxygen evolution reaction process and full accommodation of volume changes caused by the fast growth of Li₂O₂ films during the oxygen reduction reaction process. The super‐assembled porous CeO₂/C frameworks satisfy critical requirements including controlled size, morphology, high Ce³⁺/Ce⁴⁺ ratio, and efficient volume change accommodation, which dramatically increase the cycle life of LOB cell to 440 cycles. This study reveals the design strategy for high performance CeO₂ catalyst cathodes for LOB cells and the generation mechanisms of Li₂O₂ films during the discharge process by using density functional theory calculations, showing new avenues for improving the future smart design of CeO₂‐based cathode catalysts for Li–O₂ batteries.     

Antibacterial Activity of Polymer Coated Cerium Oxide Nanoparticles

Cerium oxide nanoparticles have found numerous applications in the biomedical industry due to their strong antioxidant properties. In the current study, we report the influence of nine different physical and chemical parameters: pH, aeration and, concentrations of MgSO₄, CaCl₂, KCl, natural organic matter, fructose, nanoparticles and Escherichia coli, on the antibacterial activity of dextran coated cerium oxide nanoparticles. A least-squares quadratic regression model was developed to understand the collective influence of the tested parameters on the anti-bacterial activity and subsequently a computer-based, interactive visualization tool was developed. The visualization allows us to elucidate the effect of each of the parameters in combination with other parameters, on the antibacterial activity of nanoparticles. The results indicate that the toxicity of CeO₂ NPs depend on the physical and chemical environment; and in a majority of the possible combinations of the nine parameters, non-lethal to the bacteria. In fact, the cerium oxide nanoparticles can decrease the anti-bacterial activity exerted by magnesium and potassium salts.     

Exposure to Cerium Dioxide Nanoparticles Differently Affect Swimming Performance and Survival in Two Daphnid Species

The CeO₂ NPs are increasingly used in industry but the environmental release of these NPs and their subsequent behavior and biological effects are currently unclear. This study evaluates for the first time the effects of CeO₂ NPs on the survival and the swimming performance of two cladoceran species, Daphnia similis and Daphnia pulex after 1, 10 and 100 mg.L⁻¹ CeO₂ exposures for 48 h. Acute toxicity bioassays were performed to determine EC₅₀ of exposed daphnids. Video-recorded swimming behavior of both daphnids was used to measure swimming speeds after various exposures to aggregated CeO₂ NPs. The acute ecotoxicity showed that D. similis is 350 times more sensitive to CeO₂ NPs than D. pulex, showing 48-h EC₅₀ of 0.26 mg.L⁻¹ and 91.79 mg.L⁻¹, respectively. Both species interacted with CeO₂ NPs (adsorption), but much more strongly in the case of D. similis. Swimming velocities (SV) were differently and significantly affected by CeO₂ NPs for both species. A 48-h exposure to 1 mg.L⁻¹ induced a decrease of 30% and 40% of the SV in D. pulex and D. similis, respectively. However at higher concentrations, the SV of D. similis was more impacted (60% off for 10 mg.L⁻¹ and 100 mg.L⁻¹) than the one of D. pulex. These interspecific toxic effects of CeO₂ NPs are explained by morphological variations such as the presence of reliefs on the cuticle and a longer distal spine in D. similis acting as traps for the CeO₂ aggregates. In addition, D. similis has a mean SV double that of D. pulex and thus initially collides with twice more NPs aggregates. The ecotoxicological consequences on the behavior and physiology of a CeO₂ NPs exposure in daphnids are discussed.     

Gentiopicroside promotes the osteogenesis of bone mesenchymal stem cells by modulation of β‐catenin‐BMP2 signalling pathway

Osteoporosis is characterized by increased bone fragility, and the drugs used at present to treat osteoporosis can cause adverse reactions. Gentiopicroside (GEN), a class of natural compounds with numerous biological activities such as anti‐resorptive properties and protective effects against bone loss. Therefore, the aim of this work was to explore the effect of GEN on bone mesenchymal stem cells (BMSCs) osteogenesis for a potential osteoporosis therapy. In vitro, BMSCs were exposed to GEN at different doses for 2 weeks, whereas in vivo, ovariectomized osteoporosis was established in mice and the therapeutic effect of GEN was evaluated for 3 months. Our results in vitro showed that GEN promoted the activity of alkaline phosphatase, increased the calcified nodules in BMSCs and up‐regulated the osteogenic factors (Runx2, OSX, OCN, OPN and BMP2). In vivo, GEN promoted the expression of Runx2, OCN and BMP2, increased the level of osteogenic parameters, and accelerated the osteogenesis of BMSCs by activating the BMP pathway and Wnt/β‐catenin pathway, effect that was inhibited using the BMP inhibitor Noggin and Wnt/β‐catenin inhibitor DKK1. Silencing the β‐catenin gene and BMP2 gene blocked the osteogenic differentiation induced by GEN in BMSCs. This block was also observed when only β‐catenin was silenced, although the knockout of BMP2 did not affect β‐catenin expression induced by GEN. Therefore, GEN promotes BMSC osteogenesis by regulating β‐catenin‐BMP signalling, providing a novel strategy in the treatment of osteoporosis.     

Multiphase Nanostructure of a Quinary Metal Oxide Electrocatalyst Reveals a New Direction for OER Electrocatalyst Design

Ce‐rich mixed metal oxides comprise a recently discovered class of ­electrocatalysts for the oxygen evolution reaction (OER). In particular, at current densities below 10 mA cm^?2, Ni_0.3Fe_0.07Co_0.2Ce_0.43O_x exhibits ­superior activity compared to the corresponding transition metal oxides, despite the relative inactivity of ceria. To elucidate the enhanced activity and underlying catalytic mechanism, detailed structural characterization of this quinary oxide electrocatalyst is reported. Transmission electron microscopy imaging of cross‐section films as‐prepared and after electrochemical testing reveals a stable two‐phase nanostructure composed of 3–5 nm diameter crystallites of fluorite CeO₂ intimately mixed with 3–5 nm crystallites of transition metal oxides alloyed in the rock salt NiO structure. Dosing experiments demonstrate that an electron flux greater than ≈1000 e Å^?2 s^?1 causes the inherently crystalline material to become amorphous. A very low dose rate of 130 e Å^?2 s^?1 is employed for atomic resolution imaging using inline holography techniques to reveal a nanostructure in which the transition metal oxide nanocrystals form atomically sharp boundaries with the ceria nanocrystals, and these results are corroborated with extensive synchrotron X‐ray absorption spectroscopy measurements. Ceria is a well‐studied cocatalyst for other heterogeneous and electrochemical reactions, and our discovery introduces biphasic cocatalysis as a design concept for improved OER electrocatalysts.     

BMP2/7 heterodimer enhances osteogenic differentiation of rat BMSCs via ERK signaling compared with respective homodimers

Bone morphogenetic protein (BMP)2/7 heterodimer shows greater efficacy in enhancing bone regeneration. However, the precise mechanism and the role of mitogen-activated protein kinase (MAPK) signaling network in BMP2/7-driven osteogenesis remain ambiguous. In this study, we evaluated the effects of BMP2/7 heterodimers on osteoblastic differentiation in rat bone marrow mesenchymal stem cells (BMSCs), with the aim to elaborate how MAPKs might be involved in this cellular process by treatment of rat BMSCs with BMP2/-7 with a special signal-pathway inhibitor. We found that BMP2/7 heterodimer induced a much stronger osteogenic response in rat BMSCs compared with either homodimer. Most interestingly, extracellular signal-regulated kinase (ERK) demonstrated a highly sustained phosphorylation and activation in the BMP2/7 heterodimer treatment groups, and inhibition of ERK cascades using U0126 special inhibitor that significantly reduced the activity of ALP and calcium mineralization to a substantial degree in rat BMSCs treated with BMP2/7 heterodimers. Collectively, we demonstrate that BMP2/7 heterodimer shows a potent ability to stimulate osteogenesis in rat BMSCs. The activated ERK signaling pathway involved in this process may contribute partially to an increased osteogenic potency of heterodimeric BMP2/7 growth factors.