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Various exogenous contaminants typically coexist in waste activated sludge (WAS), and the long-term impacts of these co-occurring contaminants on WAS anaerobic fermentation and associated mechanisms remain largely unknown. This study reveals that the co-occurrence of surfactants and nanoparticles (NPs, i.e., Fe 2 O 3 and CeO 2 , frequently detected in sludge) exhibited time-dependent impacts on the volatile fatty acids (VFAs) biosynthesis. Surfactants triggered WAS decomposition and enhanced NPs dispersion, leading to increased exposure of functional anaerobes to NPs toxicity, negatively affecting them. Consequently, key fermentation processes, acidogenic bacterial abundance, and metabolic functions were inhibited in co-occurrence reactors compared to those containing only surfactants in the early stage (before 56 d). Surprisingly, the fermentation systems containing surfactants collapsed subsequently, with VFAs yield at 72 d decreasing by 48.59-71.27 % compared to 56 d. The keystone microbes (i.e., Acidobacteria (16 d) vs Patescibacteria (56 d)) were reshaped, and metabolic traits (i.e., proB involved in intracellular metabolism) were downregulated by 0.05-78.02 % due to reduced microbial adaptive capacity (i.e., quorum sensing (QS)). Partial least squares path modeling (PLS-PM) analysis suggests that the microbial community was the predominant factor influencing VFAs generation. This study provides new insights into the long-term effects of co-contaminants on the biological treatment of WAS., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Sustainable technologies for the recovery of rare earth elements (REE) from waste need to be developed to decrease the volume of ore mining extractions and its negative environmental consequences, while simultaneously restoring previously impacted lands. This is critical due to the extensive application of REE in everyday life from electronic devices to energy and medical technologies, and the dispersed distribution of REE resources in the world. REE recovery by plants has been previously studied but the feasibility of REE phytoextraction from a poorly soluble solid phase (i.e., nanoparticles) by different plant species has been rarely investigated. In this study, the effect of biostimulation and bioaugmentation on phytorecovery of REE nanoparticles (REE-NP) was investigated by exposing ryegrass seeds to REE-NP in hydroponic environments. This was studied in two sets of experiments: bioaugmentation (using CeO 2 nanoparticles and Methylobacterium extorquens AM1 pure culture), and biostimulation (using CeO 2 or Nd 2 O 3 nanoparticles and endogenous microorganisms). Addition of M. extorquens AM1 in bioaugmentation experiment including 500 mg/L CeO 2 nanoparticles could not promote the nanoparticles accumulation in both natural and surface-sterilized treatments. However, it enhanced the translocation of Ce from roots to shoots in sterile samples. Moreover, another REE-utilizing bacterium, Bacillus subtilis, was enriched more than M. extorquens in control samples (no M. extorquens AM1), and associated with 52% and 14% higher Ce extraction in both natural (165 μg/g dried-plant ) and surface-sterilized samples (136 μg/g dried-plant ), respectively; showing the superior effect of endogenous microorganisms' enrichment over bioaugmentation in this experiment. In the biostimulation experiments, up to 705 μg/g dried-plant Ce and 19,641 μg/g dried-plant Nd could be extracted when 500 mg/L REE-NP were added. Furthermore, SEM-EDS analysis of the surface and longitudinal cross-sections of roots in Nd 2 O 3 treatments confirmed surface and intracellular accumulation of Nd 2 O 3 -NP. These results demonstrate stimulation of endogenous microbial community can lead to an enhanced REE phytoaccumulation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Background: Biogeochemical processing of metals including the fabrication of novel nanomaterials from metal contaminated waste streams by microbial cells is an area of intense interest in the environmental sciences., Results: Here we focus on the fate of Ce during the microbial reduction of a suite of Ce-bearing ferrihydrites with between 0.2 and 4.2 mol% Ce. Cerium K-edge X-ray absorption near edge structure (XANES) analyses showed that trivalent and tetravalent cerium co-existed, with a higher proportion of tetravalent cerium observed with increasing Ce-bearing of the ferrihydrite. The subsurface metal-reducing bacterium Geobacter sulfurreducens was used to bioreduce Ce-bearing ferrihydrite, and with 0.2 mol% and 0.5 mol% Ce, an Fe(II)-bearing mineral, magnetite (Fe(II)(III) 2 O 4 ), formed alongside a small amount of goethite (FeOOH). At higher Ce-doping (1.4 mol% and 4.2 mol%) Fe(III) bioreduction was inhibited and goethite dominated the final products. During microbial Fe(III) reduction Ce was not released to solution, suggesting Ce remained associated with the Fe minerals during redox cycling, even at high Ce loadings. In addition, Fe L 2,3 X-ray magnetic circular dichroism (XMCD) analyses suggested that Ce partially incorporated into the Fe(III) crystallographic sites in the magnetite. The use of Ce-bearing biomagnetite prepared in this study was tested for hydrogen fuel cell catalyst applications. Platinum/carbon black electrodes were fabricated, containing 10% biomagnetite with 0.2 mol% Ce in the catalyst. The addition of bioreduced Ce-magnetite improved the electrode durability when compared to a normal Pt/CB catalyst., Conclusion: Different concentrations of Ce can inhibit the bioreduction of Fe(III) minerals, resulting in the formation of different bioreduction products. Bioprocessing of Fe-minerals to form Ce-containing magnetite (potentially from waste sources) offers a sustainable route to the production of fuel cell catalysts with improved performance., (© 2024. The Author(s).)

The bioavailability of cerium (Ce) and its toxic effects on aquatic organisms are still unclear, which limits the toxicity prediction and pollution control for this element. Here, the acute toxicity of Ce to Daphnia magna neonates and the responses of the antioxidant system were investigated, and the quantitative relationships between the toxicity of Ce and environmental factors were determined. The 24 and 48 h EC50 Ce-D values based on the dissolved concentration of Ce in Daphnia magna were 60.6 and 10.9 μM, respectively, and the EC50 Ce3+ values were 23.4 and 3.73 μM, respectively. After Ce exposure at environmentally relevant concentrations (0.5-3.5 μM), significant increases in superoxide dismutase activity and malondialdehyde content were observed in Daphnia magna, while significant decreases in catalase activity and H 2 O 2 content occurred. Low levels of Ce cause oxidative damage to Daphnia magna and adverse impacts on the antioxidant system; however, further molecular-based studies are needed. The addition of Ca 2+ or Na + reduced the acute toxicity of Ce to Daphnia magna. In contrast, Mg 2+ (MgSO 4 ) promoted Ce toxicity, which is a new finding related to the interaction effects between cations and rare earth elements on biological ligands; however, the effects of SO 4 2+ could not be distinguished. Complexation with organic ligands could significantly reduce the toxicity of Ce to Daphnia magna; however, complexes of Ce with citric acid and malic acid might be bioavailable to Daphnia magna. In the absence of organic ligands and competing metals, the binding constant of Ce 3+ to Daphnia magna at toxic concentrations was 5.83. The log K values for the competitive effects of Ca 2+ and Na + were 3.73 and 2.59, respectively, while the log K value for the protective effect of fulvic acid was 3.76. These results contribute to understanding the toxicity of Ce and will help predict the toxicity of Ce in freshwater., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

This research aimed to clarify the mitigative effect of exogenously applied rare earth element cerium （Ce） on the growth， zinc （Zn） accumulation， and physiological characteristics of wheat （ Triticum aestivum L.） seedlings under Zn stress. The wheat variety studied was Bainong307 （BN307）， and Zn stress was achieved by growing seedlings in a hydroponic culture experiment with 500 μmol·L -1 Zn 2 + added to the culture solution. It was found that Zn stress at 500 μmol·L -1 significantly inhibited the chlorophyll content， photosynthesis， and biomass accumulation of wheat seedlings. Seedling roots became shorter and thicker， and the lateral roots decreased under Zn stress. The Zn stress also increased MDA accumulation and the degree of cell membrane lipid peroxidation and reduced soluble protein contents and the activities of antioxidant enzymes such as superoxide dismutase （SOD）， catalase （CAT）， and ascorbate peroxidase （APX）. On the contrary， exogenous Ce decreased the adsorption and transport of Zn by the root system and alleviated the damage of Zn stress to wheat seedlings. Specifically， the increase in chlorophyll content （chlorophyll a， chlorophyll b， and total chlorophyll） and photosynthetic parameters， the enhancement of antioxidant enzymes activities and soluble protein levels， and the reduction in MDA content and the damage of lipid peroxidation to the cell membrane were all driven by exogenous Ce， which ultimately led to the increase in dry matter biomass of the root system and shoot. In summary， these results provide basic data for the application of exogenous Ce to alleviate Zn toxicity to plants.

The interaction of inorganic nanomaterials with biological fluids containing proteins can lead not only to the formation of a protein corona and thereby to a change in the biological activity of nanoparticles but also to a significant effect on the structural and functional properties of the biomolecules themselves. This work studied the interaction of nanoscale CeO 2 , the most versatile nanozyme, with human serum albumin (HSA). Fourier transform infrared spectroscopy, MALDI-TOF mass spectrometry, UV-vis spectroscopy, and fluorescence spectroscopy confirmed the formation of HSA-CeO 2 nanoparticle conjugates. Changes in protein conformation, which depend on the concentration of both citrate-stabilized CeO 2 nanoparticles and pristine CeO 2 nanoparticles, did not affect albumin drug-binding sites and, accordingly, did not impair the HSA transport function. The results obtained shed light on the biological consequences of the CeO 2 nanoparticles' entrance into the body, which should be taken into account when engineering nanobiomaterials to increase their efficiency and reduce the side effects.

Soft tissue integration around the abutment of implants is the basis of long-term retention of implants. Macrophages are an important component involved in the repair of soft tissue due to their crucial role in improving the biological structure of connective tissues by regulating the fiber synthesis, adhesion, and contraction of gingival fibroblasts. Recent studies have illustrated that cerium-doped zeolitic imidazolate framework-8 (Ce@ZIF-8) nanoparticles (NPs) can attenuate periodontitis via both antibacterial and anti-inflammatory effects. However, the effect of Ce@ZIF-8 NPs on soft tissue integration around the abutment is unknown. Herein, we first prepared Ce@ZIF-8 NPs by a one-pot synthesis. Then, we probed the regulatory effect of Ce@ZIF-8 NPs on macrophage polarization, and further experiments were performed to study the changes of fiber synthesis as well as adhesion and contraction of fibroblasts in the M2 macrophage environment stimulated by Ce@ZIF-8 NPs. Strikingly, Ce@ZIF-8 NPs can be internalized by M1 macrophages through macropinocytosis and caveolae-mediated endocytosis in addition to phagocytosis. By catalyzing hydrogen peroxide to produce oxygen, the mitochondrial function was remedied, while hypoxia inducible factor-1α was restrained. Then, macrophages were shifted from the M1 to M2 phenotype via this metabolic reprogramming pathway, provoking soft tissue integration. These results provide innovative insights into facilitating soft tissue integration around implants.

Two methanol dehydrogenases (MDHs), MxaFI and XoxF, have been characterized in methylotrophic and methanotrophic bacteria. MxaFI contains a calcium ion in its active site, whereas XoxF contains a lanthanide ion. Importantly, the expression of MxaFI and XoxF is inversely regulated by lanthanide bioavailability, i.e., the "lanthanide switch." To reveal the genetic and environmental factors affecting the lanthanide switch, we focused on two Methylosinus trichosporium OB3b mutants isolated during routine cultivation. In these mutants, MxaF was constitutively expressed, but lanthanide-dependent XoxF1 was not, even in the presence of 25 μM cerium ions, which is sufficient for XoxF expression in the wild type. Genotyping showed that both mutants harbored a loss-of-function mutation in the CQW49_RS02145 gene, which encodes a TonB-dependent receptor. Gene disruption and complementation experiments demonstrated that CQW49_RS02145 was required for XoxF1 expression in the presence of 25 μM cerium ions. Phylogenetic analysis indicated that CQW49_RS02145 was homologous to the Methylorubrum extorquens AM1 lanthanide transporter gene ( lutH ). These findings suggest that CQW49_RS02145 is involved in lanthanide uptake across the outer membrane. Furthermore, we demonstrated that supplementation with cerium and glycerol caused severe growth arrest in the wild type. CQW49_RS02145 underwent adaptive laboratory evolution in the presence of cerium and glycerol ions, resulting in a mutation that partially mitigated the growth arrest. This finding implies that loss-of-function mutations in CQW49_RS02145 can be attributed to residual glycerol from the frozen stock. IMPORTANCE Lanthanides are widely used in many industrial applications, including catalysts, magnets, and polishing. Recently, lanthanide-dependent metabolism was characterized in methane-utilizing bacteria. Despite the global demand for lanthanides, few studies have investigated the mechanism of lanthanide uptake by these bacteria. In this study, we identify a lanthanide transporter in Methylosinus trichosporium OB3b and indicate the potential interaction between intracellular lanthanide and glycerol. Understanding the genetic and environmental factors affecting lanthanide uptake should not only help improve the use of lanthanides for the bioconversion of methane into valuable products like methanol but also be of value for developing biomining to extract lanthanides under neutral conditions.

Cerium oxide nanoparticles (n-CeO 2 ) have wide applications ranging from industrial to consumer products, which would inevitably lead to their release into the environment. Despite the toxicity of n-CeO 2 on aquatic organisms has been largely reported, research on developing organisms is still lacking. In this study, we investigate the toxic effects of n-CeO 2 on the stem cells, tissue- and neuro-regeneration, using freshwater planarian Dugesia japonica as a model. Effects of bulk sized (μ-) CeO 2 and ionic Ce (Ce 3+ ) were compared with that of n-CeO 2 to explore the origin of the toxic effects of n-CeO 2 . No overt toxicity was observed in μ-CeO 2 treatment. n-CeO 2 not only impaired the homeostasis of normal planarians, but also inhibited the regeneration processes of regenerated planarians, demonstrated by the inhibited blastema growth, disturbed antioxidant defense system at molecular levels, elevated DNA-damage and decreased stem cell proliferation. Regenerating organisms are more susceptible to n-CeO 2 than the normal ones. Ce 3+ exhibited significantly higher toxicity than n-CeO 2 , even though the total Ce uptake is 0.2 % less in Ce 3+ than in n-CeO 2 treated in planarian. X-ray absorption near edge spectroscopy (XANES) analysis revealed that 12.8 % of n-CeO 2 (5.95 mg/kg Ce per planarian) was transformed to Ce 3+ after interaction with planarian, suggesting that biotransformation at the nano-bio interface might play an important role in the observed toxicity. Since the biotransformation of n-CeO 2 is a slow process, it may cause long-term chronic toxicity to planarians due to the slow while sustained release of toxic Ce 3+ ions., Competing Interests: Declaration of competing interest The authors declare that they have no competing interests., (Copyright © 2022. Published by Elsevier B.V.)

Nannochloropsis oculata can accumulate large amounts of lipids under rare earth element (REE) conditions. However, the lipid accumulation mechanism responsible for REE stress has not been elucidated. In this study, the effects of cerium (the most abundant REE) on the growth and lipid accumulation of N. oculata were investigated. The de novo transcriptome data of N. oculata under cerium conditions were subsequently collected and analyzed. The results showed that N. oculata exhibited good cerium-resistance ability, showed slightly decrease in biomass but significantly increase in lipid content (55.8 % dry cell weight) under 6.0 mg/L cerium condition. Meanwhile, about 83.4 % cerium was biological fixated. Through transcriptome analysis, we found that the inhibited photosynthesis and carbon fixation pathways coupled with the stress-sensitive expression of ribosome biogenesis genes acclimatized the cells to REE stress. The active glycolysis pathway accelerated carbon flux to pyruvate and acetyl-CoA, and the upregulation of glycerol kinase and phosphatidate cytidylyltransferase genes further induced lipid accumulation. In addition, cerium downregulated the acyl-CoA oxidase and triacylglycerol lipase genes, which inhibited the degradation of lipids. Therefore, different responses to cerium demonstrate how N. oculata cells adapt to REE stress, and this knowledge may be used to extend our understanding of triacylglycerol (TAG) and the synthesis of other important metabolites., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier B.V.)

Cerium oxide nanoparticles (CeO 2 NPs) and zinc oxide nanoparticles (ZnO NPs) are emerging pollutants that are likely to occur in the contemporary environment. So far, their combined effects on terrestrial plants have not been thoroughly investigated. Obviously, this subject is a challenge for modern ecotoxicology. In this study, Pisum sativum L. plants were exposed to either CeO 2 NPs or ZnO NPs alone, or mixtures of these nano-oxides (at two concentrations: 100 and 200 mg/L). The plants were cultivated in hydroponic system for twelve days. The combined effect of NPs was proved by 1D ANOVA augmented by Tukey's post hoc test at p = 0.95. It affected all major plant growth and photosynthesis parameters. Additionally, HR-CS AAS and ICP-OES were used to determine concentrations of Cu, Mn, Fe, Mg, Ca, K, Zn, and Ce in roots and shoots. Treatment of the pea plants with the NPs, either alone or in combination affected the homeostasis of these metals in the plants. CeO 2 NPs stimulated the photosynthesis rate, while ZnO NPs prompted stomatal and biochemical limitations. In the mixed ZnO and CeO 2 treatments, the latter effects were decreased by CeO 2 NPs. These results indicate that free radicals scavenging properties of CeO 2 NPs mitigate the toxicity symptoms induced in the plants by ZnO NPs.

Catalytic cascades have drawn much attention by avoiding the isolation of intermediates and due to high atom economy. Yet, developing an efficient, one-pot biocatalytic cascade remains challenging. Combined with the selectivity of biological enzymes and tunable activity of nanozymes, we herein demonstrate an effective bio-nanozyme cascade formed by glucose oxidase (GOx) and in situ-generated nanoceria. The prepared H 2 O 2 -nanoceria complex shows strong oxidative activity for common chromogenic substrates under physiological conditions, which are the optimal reaction conditions for most biological enzymes. Interestingly, GOx not only provides H 2 O 2 for the second step reaction but also simultaneously leads to 7.4-fold enhancement of activity. We characterized the process of in situ generation of nanoceria at pH 7.0 and how proteins boost the activity by enhancing product desorption. In addition, the proposed one-pot bio-nanozyme cascade shows high stability and analytical performance for serum glucose with a detection limit of 5 μM.

In the present study, the novel Ag/cellulose nanocrystal (CNC)-doped CeO 2 quantum dots (QDs) with highly efficient catalytic performance were synthesized using one pot co-precipitation technique, which were then applied in the degradation of methylene blue and ciprofloxacin (MBCF) in wastewater. Catalytic activity against MBCF dye was significantly reduced (99.3%) for (4%) Ag dopant concentration in acidic medium. For Ag/CNC-doped CeO 2 vast inhibition domain of G-ve was significantly confirmed as (5.25-11.70 mm) and (7.15-13.60 mm), while medium- to high-concentration of CNC levels were calculated for G + ve (0.95 nm, 1.65 mm), respectively. Overall, (4%) Ag/CNC-doped CeO 2 revealed significant antimicrobial activity against G-ve relative to G + ve at both concentrations, respectively. Furthermore, in silico molecular docking studies were performed against selected enzyme targets dihydrofolate reductase (DHFR), dihydropteroate synthase (DHPS), and DNA gyrase belonging to folate and nucleic acid biosynthetic pathway, respectively to rationalize possible mechanism behind bactericidal potential of CNC-CeO 2 and Ag/CNC-CeO 2 ., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Herein, we demonstrate that the active surface of nanoceria can be fine-tuned by phosphorylated peptides. Accordingly, a colorimetric and fluorometric dual-readout strategy is rationally developed for assaying protein kinase activity. This feature not only enables the versatile monitoring of peptide phosphorylation but also broadens the application scope of nanoceria.

Background: The main goal of our study was to explore the wound-healing property of a novel cerium-containing N-acethyl-6-aminohexanoate acid compound and determine key molecular targets of the compound mode of action in diabetic animals., Methods: Cerium N-acetyl-6-aminohexanoate (laboratory name LHT-8-17) as a 10 mg/mL aquatic spray was used as wound experimental topical therapy. LHT-8-17 toxicity was assessed in human skin epidermal cell culture using (4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. A linear wound was reproduced in 18 outbred white rats with streptozotocin-induced (60 mg/kg i.p.) diabetes; planar cutaneous defect was modelled in 60 C57Bl 6 mice with streptozotocin-induced (200 mg/kg i.p.) diabetes and 90 diabetic db / db mice. Firmness of the forming scar was assessed mechanically. Skin defect covering was histologically evaluated on days 5, 10, 15, and 20. Tissue TNF-α, IL-1β and IL-10 levels were determined by quantitative ELISA. Oxidative stress activity was detected by Fe-induced chemiluminescence. Ki-67 expression and CD34 cell positivity were assessed using immunohistochemistry. FGFR3 gene expression was detected by real-time PCR. LHT-8-17 anti-microbial potency was assessed in wound tissues contaminated by MRSA., Results: LHT-8-17 4 mg twice daily accelerated linear and planar wound healing in animals with type 1 and type 2 diabetes. The formulated topical application depressed tissue TNF-α, IL-1β, and oxidative reaction activity along with sustaining both the IL-10 concentration and antioxidant capacity. LHT-8-17 induced Ki-67 positivity of fibroblasts and pro-keratinocytes, upregulated FGFR3 gene expression, and increased tissue vascularization. The formulation possessed anti-microbial properties., Conclusions: The obtained results allow us to consider the formulation as a promising pharmacological agent for diabetic wound topical treatment.

The biological enzyme-mimetic activity of cerium oxide nanoparticles (CeNPs) is well known to scavenge the reactive oxygen and nitrogen species in cell culture and animal models, imparting protection from the deleterious effects of oxidative and nitrosative stress. The superoxide dismutase (SOD)- and catalase-mimicking activity of CeNPs is reported to be controlled by the oxidation state of the surface "Ce" ions, where a high ratio of Ce 3+/4+ or Ce 4+/3+ has been considered for the displayed SOD and catalase-like activity, respectively. However, the redox behavior of CeNPs can be controlled by certain ligands that could offer changes in their enzyme-mimetic properties. Therefore, in this work, we have studied the enzyme-mimetic activities of CeNPs under the influence of polyoxometalates [phosphomolybdic acid (PMA) and phosphotungstic acid (PTA)], which are electron-dense molecules displaying quick and reversible multielectron redox reactions. Results revealed that the interaction of PMA with CeNPs results in the inhibition of the SOD-like activity; however, it has no impact on the catalase-like activity. Contrary to this, the interaction of PTA with CeNPs improved the SOD as well as catalase-like activities of CeNPs (3+), which generally do not exhibit catalase activity in the bare form. Although CeNPs (3+) did not show any peroxidase-like activity, CeNPs (4+) showed excellent activity, which was enhanced after the interaction with polyoxometalates. Further, the autoregeneration ability of CeNPs was found to be intact even after PTA or PMA interaction; however, the full catalytic activity was observed in the case of PTA but partially with PMA.

Cerium (Ce) is a promising candidate ion for application in bone tissue engineering (BTE) since it reduces the presence of reactive oxygen species. Ce-doped mesoporous bioactive glass nanoparticles (MBGNs) serving as vectors for the local application of Ce already demonstrated stimulating effects on the expression of pro-osteogenic genes in Saos-2 cells. So far, there is no evidence available about the effects of Ce-doped MBGNs on the viability, osteogenic differentiation and the formation of the osseous extracellular matrix (ECM) of primary human bone marrow-derived mesenchymal stromal cells (BMSCs). Therefore, in this study, the biocompatibility of the ionic dissolution products (IDPs) of MBGNs containing increasing concentrations of CeO 2 (0.05 MCe-MBGNs, composition in mol%: 86.6SiO 2 -12.1CaO-1.3CeO 2 ; and 0.2 MCe-MBGNs, composition in mol%: 86.0SiO 2 -11.8CaO-2.2CeO 2 ) and unmodified MBGNs (composition in mol%: 86SiO 2 -14CaO) was evaluated using human BMSCs. Eventually, the impact of the MBGNs' IDPs on the cellular osteogenic differentiation and their ability to build and mature a primitive osseous ECM was assessed. The Ce-doped MBGNs had a positive influence on the viability and stimulated the cellular osteogenic differentiation of human BMSCs evaluated by analyzing the activity of alkaline phosphate as a marker enzyme for osteoblasts in the present setting. Furthermore, the formation and calcification of a primitive osseous ECM was significantly stimulated in the presence of Ce-doped MBGNs in a positive concentration-dependent manner as demonstrated by an elevated presence of collagen and increased ECM calcification. The results of this in-vitro study show that Ce-doped MBGNs are attractive candidates for further application in BTE., (© 2021 IOP Publishing Ltd.)

Rare earth elements (REEs) have received enormous attention in recent years. However, there are many gaps in the understanding of their behavior in the soil-plant system. The aim of this study is to investigate the behavior of three most common REEs (La, Ce, Nd) in the soil-plant system directly on soil samples using barley (Hordeum vulgare L.) in a vegetation experiment. We attribute the absence of significant changes in plant biomass and photosynthetic pigment content to the reduced availability of REEs in soil samples. The concentration of water-soluble forms of La, Ce and Nd didn't exceed 1 mg/kg, while the concentration of exchangeable forms varied and decreased in a row La > Ce > Nd. The transfer factor (TF) from soil to above-ground biomass was low for all three elements (<1). The stem-to-leaf TF increased with the increase in REEs concentration in soil. The concentration in plant material increased in the row Ce < Nd < La. REEs concentrations in barley leaves didn't exceed 1-3% of the corresponding element concentration in soil samples. REEs concentration in plant tissues is in close direct correlation with the REEs total concentration in soil, water-soluble and exchange forms. REEs concentration in barley leaves is 3-4 times higher than in the stems and for the group with extraneous concentration of 200 mg/kg for La, Ce and Nd was 6.20 ± 1.48, 2.10 ± 0.51, 6.90 ± 3.00 mg/kg, respectively. We show that there were no major changes in barley plants, but further study is needed of the relationship between the absorption of lanthanides by plants and the content of various forms of lanthanides in the soil., (Copyright © 2020 Elsevier Inc. All rights reserved.)

While transfusion of donor blood is a reasonably safe and well-established procedure, artificial oxygen carriers offer several advantages over blood transfusions. These benefits include compatibility with all blood types, thus avoiding the need for cross matching, availability, lack of infection, and long-term storage. Hemoglobin (Hb)-based oxygen carriers (HBOCs) are being explored as an "oxygen bridge" to replace or complement standard blood transfusions in extreme, life-threatening situations such as trauma in remote locations or austere battlefield or when blood is not an option due to compatibility issues or patient refusal due to religious objections. Herein, a novel HBOC was prepared using the layer-by-layer technique. A poly(lactide- co -glycolide) core was fabricated and subsequently decorated with Hb and nanozymes. The Hb was coated with poly(dopamine), and preservation of the protein structure and functionality was demonstrated. Next, cerium oxide nanoparticles were incorporated as nanozymes, and their ability to deplete reactive oxygen species (ROS) was shown. Finally, decorating the nanocarrier surface with poly(ethylene glycol) decreased protein adsorption and cell association/uptake. The as-prepared Hb-based oxygen nanocarriers were shown to be hemo- and bio-compatible. Their catalytic potential was furthermore demonstrated in terms of superoxide radical- and peroxide-scavenging abilities, which were retained over multiple cycles. Overall, these results demonstrate that the reported nanocarriers show potential as novel oxygen delivery systems with prolonged catalytic activity against ROS.

Metallic elements are one of the key components of human physiology, which are required for basic cellular and extracellular functions. Herein, we provide insight into the bioactive metallic dopants silver (Ag), zinc (Zn), copper (Cu), magnesium (Mg) and ceria (Ce), which provide resistance against human pathogenic bacteria, and summarise the pathways for their generated effects crucial for osteogenic activity in an antibacterial environment and bone regeneration. Although most of these elements interact with genetic material, resulting in denaturation to produce apoptosis of pathogenic cells, some create adverse effects in the cellular matrix, which interfere with normal cellular metabolism and inhibit cellular activity, reducing the further growth and formation of bacterial colonies. Furthermore, although remarkable antibacterial activity has been recorded, bacterial cells have developed pathways and transporter proteins that remove the excess of these antibacterial elements from the cellular matrix. Thus, a discussion of these reported pathways as limitations is presented to find more novel modes of administration of these elements since they show good biocompatibility and are non-cytotoxic at certain release concentrations. As a cofactor of several enzymes, it is worth noting that some of these elements not only help in the metabolism of bone, but also activate the genetic pathways that regulate the formation of and maintain the factors that support new bone. The choice of incorporating these materials in ionic or nanoparticle form depends on the target substrate since they exhibit different mechanisms of action and even produce selective effects depending on their physical properties.

Background: The transformation of nanoparticles (NPs) internalized in plant tissues is the human digestive system that can provide a better understanding of the impact of NPs on the human system. The presented methodology was developed to study the bioaccessibility of cerium oxide (CeO 2 ) and copper oxide (CuO) NPs from radish after the in vitro simulation of gastrointestinal digestion using single-particle inductively coupled plasma mass spectrometry (SP-ICP-MS)., Results: Radish plants were cultivated hydroponically in a growth medium containing: (i) CeO 2 NPs and (ii) CuO NPs. Both cerium (Ce) and copper (Cu) were found in all organs of the radish plants after analysis by standalone ICP-MS. This confirms the bioaccumulation of CeO 2 and CuO NPs and the translocation of their Ce and Cu to the aerial parts of the plant. Less Ce (4.095 μg g -1 ) has been detected in leaves than in roots (1.156 mg g -1 ) while Cu content in leaves was 5.245 μg g -1 and in roots was 10.41 μg g -1 . Analysis of the digestive extracts obtained after the in vitro simulation of gastro (pepsin) and gastrointestinal (pancreatin) digestion showed that Ce has easy access to human system at least by 73%., Conclusion: The size of CeO 2 NPs in digestive extracts showed no significant changes. However, the results obtained for CuO NPs digestion were variable and suggested that CuO NPs dissolved during the digestion process. The CuO NPs were observed in roots after the gastrointestinal digestion concluding that CuO NPs recovered after the initial dissolution. © 2020 Society of Chemical Industry., (© 2020 Society of Chemical Industry.)

G-quadruplex DNAs (G4s) have been reported to exhibit the DNAzyme activities by binding with some metal complexes and functional organic ligands. However, there is a challenge to develop metalloenzyme-mimic G4-based innate DNAzymes using the complexed metal ions directly serving as the active centers. This will diversify DNAzymes for developing novel devices since G4 structures are more polymorphic than the other DNA foldings. In this work, we found that the lanthanide trivalent cerium ion of Ce3+ can bind to the human telomere G4 (htG4) according to a 1 : 2 binding mode favorable for creating metalloenzymes-mimic G4 DNAzymes. This Ce3+-G4 entity exhibits a peroxidase activity towards the oxidation of the substrate of 3,3,5,5-tetramethylbenzidine (TMB) by hydrogen peroxide. The 5' G4 tetrads with the orderly arranged carbonyl oxygen atoms are believed to be the coordination sites for Ce3+ and favor the conversion between Ce3+ and Ce4+. Our work provides an alternative feasibility in developing the G4-based innate DNAzymes for variant applications.

Aim: This paper was mainly aimed at synthesis of Ce-containing nano-Mg-phosphate ceramic as a multifunctional material., Materials and Methods: Two ceramics based on Mg 3 (PO 4 ) 2 and Ce 0.2 Mg 2.8 (PO 4 ) 2 formulas (MP and MP-C, respectively) were synthesized. The synthesized powders were characterized by XRD, TEM, Zeta potential, and FTIR. Also, their dissolution behavior was tested in Tris-HCl buffer solution. Moreover, the antimicrobial efficacy was evaluated against gram-positive bacteria (Bacillus sphaericus MTCC 511 &Staphylococcus aureus MTCC 87) and gram-negative bacteria (Enterobacter aerogenes MTCC 111 &Pseudomonas aeruginosa MTCC 1034) using dick diffusion assay and microdilution method. Furthermore, the cell viability test was performed for the ceramics on Vero cells (African green monkey kidney cells), and their antitumor activity was determined by PC3 cell line (prostatic cancer). Also, the cellular uptake was determined by the flow cytometry., Key Findings: The results showed that the substitution of Mg by Ce decreased the particle size from 40 to 90 nm for MP sample to 2-10 nm for MP-C sample and increased the degradation rate. Both samples showed excellent antimicrobial activities. Moreover, MP demonstrated more cell viability than MP-C on Vero cells at high concentrations, whereas, MP-C showed more antitumor activity on PC3 cells than MP sample. Moreover, MP-C showed a higher cell uptake than MP due to its smaller size and more negative charge., Significance: Mg-phosphate ceramic can be used in this study successfully as a delivery system for cerium ions and showed a high antitumor activity, which makes it highly recommended as safe and effective cancer treatment materials., Competing Interests: Declaration of competing interest The authors declare that they have no conflict of interest., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Prior studies showed nanoparticle clearance was different in C57BL/6 versus BALB/c mice, strains prone to Th1 and Th2 immune responses, respectively. Objective : Assess nanoceria (cerium oxide, CeO 2 nanoparticle) uptake time course and organ distribution, cellular and oxidative stress, and bioprocessing as a function of mouse strain. Methods : C57BL/6 and BALB/c female mice were i.p. injected with 10 mg/kg nanoceria or vehicle and terminated 0.5 to 24 h later. Organs were collected for cerium analysis; light and electron microscopy with elemental mapping; and protein carbonyl, IL-1β, and caspase-1 determination. Results : Peripheral organ cerium significantly increased, generally more in C57BL/6 mice. Caspase-1 was significantly elevated in the liver at 6 h, to a greater extent in BALB/c mice, suggesting inflammasome pathway activation. Light microscopy revealed greater liver vacuolation in C57BL/6 mice and a nanoceria-induced decrease in BALB/c but not C57BL/6 mice vacuolation. Nanoceria increased spleen lymphoid white pulp cell density in BALB/c but not C57BL/6 mice. Electron microscopy showed intracellular nanoceria particles bioprocessed to form crystalline cerium phosphate nanoneedles. Ferritin accumulation was greatly increased proximal to the nanoceria, forming core-shell-like structures in C57BL/6 but even distribution in BALB/c mice. Conclusions : BALB/c mice were more responsive to nanoceria-induced effects, e.g. liver caspase-1 activation, reduced liver vacuolation, and increased spleen cell density. Nanoceria uptake, initiation of bioprocessing, and crystalline cerium phosphate nanoneedle formation were rapid. Ferritin greatly increased with a macrophage phenotype-dependent distribution. Further study will be needed to understand the mechanisms underlying the observed differences.

Background: Both antioxidant and prooxidant activities have been previously reported for cerium oxide (CeO 2 ). The aim of this study was to investigate the effects of CeO 2 at different doses on changes in kidney tissues and markers in neonatal mice., Methods: We randomly divided 30 pregnant NMRI mice into five groups ( n = 6 per group)-a control group and four groups treated with intraperitoneal (i.p.) administration of different doses of CeO 2 (10, 25, 80, or 250 mg/kg body weight (bw)) on gestation days (GD) 7 and GD14. At the end of the treatment period, we analyzed the kidney tissues and serum samples. The levels of two serum redox markers, malondialdehyde (MDA) and ferric reducing/antioxidant power (FRAP), were determined. Data were analyzed using one-way ANOVA and Tukey's test, and a P value of <0.05 was considered significant., Results: The mean total volumes of the renal corpuscle, glomeruli, and Bowman's capsule membranes significantly increased, and there was a significant decrease in the mean total volume of Bowman's space in the high-dose CeO 2 group compared to that in the control group. No statistically significant differences existed in the serum levels of MDA and FRAP in the treated and control groups., Conclusion: Our results suggest that high doses of CeO 2 impair fetal renal development in pregnant mice, which results in kidney damage. Therefore, CeO 2 administration during pregnancy could have dose-dependent adverse effects on the developing kidneys in neonates., Competing Interests: There is no conflict of interest related to this research., (Copyright © 2020 Afsaneh Nemati et al.)

This study is planned to synthesise new biocompatible, nano antimicrobial formulation against biofilm producing strains. Aqueous root extract of Arctium lappa l. was used to synthesise ceria nanoparticles (CeO 2 -NPs). The synthesised nanoparticles were encapsulated with nano-chitosan by sol-gel method and characterised using standard techniques. Gas chromatography-mass spectrometer of Arctium lappa l. revealed the presence of ethanol, acetone, 1- propanol, 2-methylethane, 1,1-di-ethoxy, 1-Butanol, and oleic acid acted as reducing and surface stabilising agents for tailoring morphology of CeO 2 -NPs. Erythrocyte integrity after treatment with synthesised nanomaterials was evaluated by spectrophotometer measurement of haemoglobin release having biocompatibility. Scanning electron microscopy revealed the formation of mono dispersed beads shaped particles with mean particle size of 26.2 nm. X-ray diffractometry revealed cubic crystalline structure having size of 28.0 nm. After encapsulation by nano-chitosan, the size of CeO 2 -NPs enhances to 48.8 nm making average coverage of about 22.6 nm. The synthesised nanomaterials were found effective to disrupt biofilm of S. aureus and P. aeruginosa . Interestingly, encapsulated CeO 2 -NPs revealed powerful antibacterial and biofilm disruption activity examined by fluorescent live/dead staining using confocal laser scanning microscopy. The superior antibacterial activities exposed by encapsulated CeO 2 -NPs lead to the conclusion that they could be useful for controlling biofilm producing multidrug resistance pathogens.

Excessive reactive oxygen species (ROS) play a significant role in the pathogenesis of many eye diseases. Controlling oxidative stress by reducing the amount of ROS is a potential therapeutic strategy for the prevention and treatment of eye diseases, particularly ocular surface diseases. Ceria nanoparticles (CeNPs) have been investigated owing to their efficient ROS-scavenging properties. To overcome the disadvantages of eyedrop administration due to rapid elimination on the surface of the eye and to retain the intrinsic properties of contact lenses, we developed an ROS-scavenging water-soluble CeNP-embedded contact lens (CeNP-CL) for the prevention of ocular surface diseases. The intrinsic ROS-scavenging property of the CeNPs, which mimicked the activities of superoxide dismutase and catalase, was incorporated into polyhydroxyethyl methacrylate-based contact lenses. The CeNP-CL exhibited high transparency and physical properties comparable to those of a commercial contact lens, along with excellent extracellular ROS-scavenging properties. The viabilities of human conjunctival epithelial cells and human meibomian gland epithelial cells were significantly enhanced in the presence of CeNP-CLs, even in media with high H 2 O 2 contents (100 and 500 μM). Additionally, the wearing of CeNP-CLs on the eyes had a protective effect in a mouse model when 3% H 2 O 2 eyedrops were administered. These results indicate the salvaging effect of the CeNP-CL in a high-ROS environment on the ocular surface, which may be helpful for the treatment of ocular surface diseases.

To assess the role of citric acid, as a typical low-molecular-weight organic acid from root exudates, on cerium (Ce) uptake, accumulation and translocation in rice seedlings (Oryza sativa L.) exposed to two CeO 2 nanoparticles (NPs) (14 nm and 25 nm). A hydroponic experiment was performed under two citric acid levels (0.01 and 0.04 mmol L -1 ) combined with iron plaque presence. Citric acid significantly enhanced surface-Ce, root-Ce and shoot-Ce accumulation, irrespective of NPs size and iron plaque presence. The increased surface-Ce was associated with the promoted interactive attraction between NPs and root surface, and the enhanced NPs dissolution. Surface-Ce (containing crystalline and amorphous fractions of iron plaque) accumulation increased with the increase of citric acid concentrations. However, the enhancement influence of 0.01 mmol L -1 citric acid on root-Ce, shoot-Ce accumulations, rice-Ce distribution and TF root-shoot was more remarkable than citric acid (0.04 mmol L -1 ), which suggested higher food security risk for human health with environment-level citric acid. Iron plaque presence attenuated the enhancement effect of citric acid on rice-Ce accumulation and distribution (containing surface-Ce, root-Ce and shoot-Ce) due to the reduced attractive interaction between NPs and root surface from the effect of Fe 2+ being dissolved by iron plaque. Above effect of citric acid and iron plaque was more remarkable in 25 nm NP than 14 nm NP., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The high toxicity and mobility of hexavalent chromium (Cr(VI)) allow it to easily spread and bioaccumulate, and its detection is a major part of environmental protection. In this work, an innovative method is developed for preparation of cerium oxide nanorod-templated metal-organic frameworks (CeO 2 NRs-MOF). The in situ growth of MOF on the surface of CeO 2 nanorods (CeO 2 NRs) enhances its oxidase-like activity. In the presence of a trace amount of Cr(VI), CeO 2 NRs-MOF can significantly accelerate the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) due to Cr(VI)-boosted oxidation, resulting in a blue colored oxidation product. It can detect Cr(VI) over a range of 0.03-5 μM with high selectivity. Moreover, this method can be applied to the detection of Cr(VI) in different water environment samples with satisfactory recoveries, demonstrating the potential application of CeO 2 NRs-MOF for the direct monitoring of Cr(VI) in environmental water systems. Thus, this work provides a facile host-templated MOF preparation method, which could possibly be extended to other fields.

The extensive use of nano-fabricated products in daily life is releasing a large volume of engineered nanoparticles (ENPs) in the environment having unknown consequences. Meanwhile, little efforts have been paid to immobilize and prevent the entry of these emerging contaminants in the food chain through plant uptake. Herein, we investigated the biochar role in cerium oxide nanoparticles (CeO 2 NPs) bioaccumulation and subsequent translocation in wheat (Triticum aestivum L.) as well as impact on growth, photosynthesis and gas-exchange related physiological parameters. Results indicated that CeO 2 NPs up to 500 mg L -1 level promoted the plant growth by triggering photosynthesis, transpiration and stomatal conductance. Higher NPs concentration (2000 mg CeO 2 NPs L -1 ) has negatively affected the plant growth and photosynthesis related processes. Conversely, biochar amendment with CeO 2 NPs considerably reduced (~9 folds) the plants accumulated contents of Ce even at 2000 mg L -1 exposure level of CeO 2 NPs through surface complexation process and alleviated the phyto-toxic effects of NPs on plant growth. XPS and FTIR analysis confirmed the role of biochar-mediated carboxylate and hydroxyl groups bonding with CeO 2 NPs. These findings provides an inside mechanistic understanding about biochar interaction with nano-pollutants to inhibit their bioavailability to plant body., (Copyright © 2019 Elsevier Inc. All rights reserved.)

In this study, Cerium chloride-induced conformational changes of Bovine Liver Catalase (BLC) has been investigated by molecular docking and further supported by various biophysical techniques. The temporal change of catalytic activity of BLC has also been studied in presence of Ce(III) with different buffer solution in vitro at 25 °C. The differential binding of Ce(III) to BLC observed by simulation study was well supported by the differential regulation of BLC activity in different buffers. After 1 h of incubation with CeCl 3 , the reduction in activity of BLC was maximum in MOPS, HEPES and Tris buffer, whereas no change in activity was noticed in phosphate buffer. Isothermal Titration Calorimetric (ITC) study also supports the differential binding of Ce(III) to BLC in different buffers. Ce(III)-induced conformational transition in BLC was followed as a function of concentration. Nevertheless, with 24 h incubation of CeCl 3 the activity of BLC was highest with higher molar concentration of CeCl 3 suggesting the conformational stability of BLC in presence of Ce(III). The compromised activity of BLC in response to Ce(III) is due to the induced conformational change and the degree of change in secondary conformation of BLC was maximum in MOPS, HEPES and Tris and least in phosphate buffer. Therefore, the reduced activity of BLC is controlled by the direct interaction of Ce(III) in the active site of BLC in Tris buffer or indirect interaction of Ce(III) in the non-active site of BLC in MOPS and HEPES buffer., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

An indicator displacement assay (IDA) was used to probe phosphate ions in an aqueous medium at neutral pH using a dinuclear cerium based complex [Ce2(HXTA)]3+. The homoleptic complex can be used to detect phosphate ions with nanomolar affinity either spectrophotometrically or with the naked-eye. To our knowledge, this is the first dinuclear cerium biomimetic IDA detection system with the highest affinity known to date for selective, naked-eye based phosphate recognition under physiological conditions (pH = 5-7) and even in pure water and complex samples such as sea water.

Polyvalent metal ions are susceptible to hydrolysis, making their reproducible detection by sensors and biosensors difficult. We herein turned this disadvantage into an advantage to develop a high selectivity colorimetric method for detecting Ce(iv) by intentionally hydrolyzing it through heating, where subsequent addition of F - recovered the activity, allowing a detection limit of 3.8 μM Ce(iv).

Nanoscale cerium dioxide (nanoceria) has industrial applications, capitalizing on its catalytic, abrasive, and energy storage properties. It auto-catalytically cycles between Ce 3+ and Ce 4+ , giving it pro-and anti-oxidative properties. The latter mediates beneficial effects in models of diseases that have oxidative stress/inflammation components. Engineered nanoparticles become coated after body fluid exposure, creating a corona, which can greatly influence their fate and effects. Very little has been reported about nanoceria surface changes and biological effects after pulmonary or gastrointestinal fluid exposure. The study objective was to address the hypothesis that simulated biological fluid (SBF) exposure changes nanoceria's surface properties and biological activity. This was investigated by measuring the physicochemical properties of nanoceria with a citric acid coating (size; morphology; crystal structure; surface elemental composition, charge, and functional groups; and weight) before and after exposure to simulated lung, gastric, and intestinal fluids. SBF-exposed nanoceria biological effect was assessed as A549 or Caco-2 cell resazurin metabolism and mitochondrial oxygen consumption rate. SBF exposure resulted in loss or overcoating of nanoceria's surface citrate, greater nanoceria agglomeration, deposition of some SBF components on nanoceria's surface, and small changes in its zeta potential. The engineered nanoceria and SBF-exposed nanoceria produced no statistically significant changes in cell viability or cellular oxygen consumption rates., (Copyright © 2019 Elsevier B.V. All rights reserved.)

We herein communicate the DNase I like activity of nanoceria (CeO2 nanoparticles). Both CeO2 and DNase I cleave polyadenine (poly-A) DNA down to ∼5-mer fragments as the major products, although further cleavage to even shorter fragments was observed with CeO2. Mass spectrometry indicates a hydrolytic cleavage mechanism instead of oxidative cleavage.

Cerium oxide nanoparticles (nanoceria) were synthesized by a novel, simple green chemistry procedure using Elaeagnus angustifolia leaf extract as a reducing and capping agent. The crystalline nature of nanoceria was confirmed by XRD analysis. FTIR analysis revealed that phytochemicals are present on the surface of nanoceria. SEM and TEM images revealed that the nanoceria are well dispersed, spherical in shape with a particle size range in between 30 and 75 nm. Thereafter, the effects of various concentrations of cerium oxide (CeO 2 ) and green synthesized nanoceria on growth and metabolism of Solanum lycopersicum (tomato) were investigated. The bio-accumulation of Ce in tomato seedlings was found to be dose dependent and the results showed that with the increase in exposure concentrations, the accumulation of Ce contents in both root and shoots augmented. However, unlike nanoceria treated seedlings, Ce contents in the roots with CeO 2 treatments were negligible than that in the shoots at lower concentrations and this suggested the immobilization of Ce in CeO 2 treatment at lower concentrations. Nanoceria at 500 and 1000 mg/L resulted in inhibitory effect on growth of test plant as compared to CeO 2 component. The exposure of plants to nanoceria and CeO 2 has resulted in significant reduction in pigment content, increased LP, EL and H 2 O 2 content. The activities of antioxidant enzymes viz. SOD, CAT, APX and GPX were significantly up regulated on exposure of nanoceria and CeO 2 . It is concluded that plant exposure with nanoceria at concentrations of 20 and 100 mg/L were more beneficial for growth and metabolism of tomato plants than that of CeO 2 at equivalent concentrations., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Cerium oxide (CeO 2 ) nanoparticles (CeNPs) are potent antioxidants that are being explored as potential therapies for diseases in which oxidative stress plays an important pathological role. However, both beneficial and toxic effects of CeNPs have been reported, and the method of synthesis as well as physico-chemical, biological, and environmental factors can impact the ultimate biological effects of CeNPs. In the present study, we explored the effect of different ratios of citric acid (CA) and EDTA (CA/EDTA), which are used as stabilizers during synthesis of CeNPs, on the antioxidant enzyme-mimetic and biological activity of the CeNPs. We separated the CeNPs into supernatant and pellet fractions and used commercially available enzymatic assays to measure the catalase-, superoxide dismutase (SOD)-, and oxidase-mimetic activity of each fraction. We tested the effects of these CeNPs in a mouse hippocampal brain slice model of ischemia to induce oxidative stress where the fluorescence indicator SYTOX green was used to assess cell death. Our results demonstrate that CeNPs stabilized with various ratios of CA/EDTA display different enzyme-mimetic activities. CeNPs with intermediate CA/EDTA stabilization ratios demonstrated greater neuroprotection in ischemic mouse brain slices, and the neuroprotective activity resides in the pellet fraction of the CeNPs. The neuroprotective effects of CeNPs stabilized with equal proportions of CA/EDTA (50/50) were also demonstrated in two other models of ischemia/reperfusion in mice and rats. Thus, CeNPs merit further development as a neuroprotective therapy for use in diseases associated with oxidative stress in the nervous system.

Due to their unique physical and chemical properties, the production and use of cerium oxide nanoparticles (CeO 2 NPs) in different areas, especially in automotive industry, is rapidly increasing, causing their presence in the environment. Released CeO 2 NPs can undergo different transformations and interact with the soil and hence with plants, providing a potential pathway for human exposure and leading to serious concerns about their impact on the ecosystem and human organism. This study investigates the uptake, bioaccumulation, possible translocation and localization of CeO 2 NPs in a model plant (Raphanus sativus L.), whose edible part is in direct contact with the soil where contamination is more likely to happen. The stability of CeO 2 NPs in plant growth medium as well as after applying a standard enzymatic digestion procedure was tested by single particle ICP-MS (SP-ICP-MS) showing that CeO 2 NPs can remain intact after enzymatic digestion; however, an agglomeration process was observed in the growth medium already after one day of cultivation. An enzymatic digestion method was next used in order to extract intact nanoparticles from the tissues of plants cultivated from the stage of seeds, followed by size characterization by SP-ICP-MS. The results obtained by SP-ICP-MS showed a narrower size distribution in the case of roots suggesting preferential uptake of smaller nanoparticles which led to the conclusion that plants do not take up the CeO 2 NPs agglomerates present in the medium. However, nanoparticles at higher diameters were observed after analysis of leaves plus stems. Additionally, a small degree of dissolution was observed in the case of roots. Finally, after CeO 2 NPs treatment of adult plants, the spatial distribution of intact CeO 2 NPs in the radish roots was studied by laser ablation ICP-MS (LA-ICP-MS) and the ability of NPs to enter and be accumulated in root tissues was confirmed., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Oxidative stress plays a crucial role in ammonia nitrogen toxicity. In this study, the beneficial effects of dietary nano cerium oxide (nano CeO 2 ) as a potent antioxidant were examined in the Chinese mitten crab (Eriocheir sinensis). Crabs were fed a diet supplemented with 0, 0.2, 0.4, 0.8, 1.6, 3.2, 6.4, or 12.8 mg/kg nano CeO 2 for 60 d. The optimum supplementation level of nano CeO 2 that significantly increased weight gain rate and decreased feed coefficient was 0.8 mg/kg. This level also offered immune protection when crabs were kept under ammonia nitrogen stress and/or exposed to pathogen infection (Aeromonas hydrophila). Supplementation with 0.8 mg/kg of CeO 2 (i) relieved pathological damage to the hepatopancreas; (ii) increased hemocyte counts, including total number of hemocytes, granulocytes, and hyalinocytes; (iii) decreased malondialdehyde content and increased antioxidant enzyme activities of superoxide dismutase and catalase in the hemolymph; (iv) increased the activities of lysozyme, acid phosphatase, and alkaline phosphatase in the hemolymph; and (v) increased gene and protein expression of cathepsin L in the hepatopancreas. Mortality increased when crabs were injected with bacteria under ammonia nitrogen stress, but dietary supplementation with 0.8 mg/kg nano CeO 2 decreased the mortality rate. Thus, the results of this study suggested that dietary supplementation with nano CeO 2 in crabs promoted growth and up-regulated immunity to bacterial infection under ammonia nitrogen stress., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Engineered nanomaterials (ENMs) are increasingly utilised for the remediation of contaminated soils. In this study, contaminant (As, Pb), nutrient (N, P) and trace element (Cu, Fe, Mn, Zn) phytoavailability in three Australian soils contaminated (<10 years) with As (≈100 mg As kg -1 soil) or Pb (≈300 mg Pb kg -1 soil) was determined periodically. These soils were exposed to two ENMs (cerium dioxide - nCeO 2 or titanium dioxide - nTiO 2 ) (applied to soil at a concentration of 500 mg ENM kg -1 soil) with contaminant, nutrient and trace element phytoavailability assessed over a 260-day period. While As phytoavailability was not influenced by either ENM, the presence of nCeO 2 in some soils increased Pb phytoavailability approximately two fold at the conclusion of the experiment (day 260), which was attributed to nCeO 2 decreasing soil pH and/or outcompeting Pb 2+ ions for sorption sites. More significantly, both ENMs significantly altered the phytoavailability of N, P and Zn across soils. In some instances >90% of the soil N was lost in the presence of both ENMs, while in some instances the phytoavailability of P and Zn was tripled and doubled respectively in the presence of ENMs. For N it was hypothesised that both ENMs altered the mineralisation of organic N and/or soil nitrification rates due to the catalytic and/or anti-microbial properties of the ENMs. For P, it was hypothesised that anti-microbial effects of both ENMs altered the activity of P-solubilising microbes. For Zn competition between the positively charged ENMs and Zn 2+ ions was the most likely mechanism for altered Zn phytoavailability. This study suggested that while ENMs can potentially be effective as metal remediation agents when applied to soils, there are however a range of potentially deleterious 'non-target' effects on soil ecosystems that have not as yet been widely considered., (Copyright © 2019. Published by Elsevier B.V.)

Cerium oxide nanoparticles (CeO 2 NPs), used in some diesel fuel additives to improve fuel combustion efficiency and exhaust filter operation, have been detected in ambient air and concerns have been raised about their potential human health impact. The majority of CeO 2 NP inhalation studies undertaken to date have used aerosol particles of larger sizes than the evidence suggests are emitted from vehicles using such fuel additives. Hence, the objective of this study was to investigate the effects of inhaled CeO 2 NP aerosols of a more environmentally relevant size, utilizing a combination of methods, including untargeted multi-omics to enable the broadest possible survey of molecular responses and synchrotron X-ray spectroscopy to investigate cerium speciation. Male Sprague-Dawley rats were exposed by nose-only inhalation to aerosolized CeO 2 NPs (mass concentration 1.8   mg/m 3 , aerosol count median diameter 40   nm) for 3   h/d for 4 d/week, for 1 or 2 weeks and sacrificed at 3 and 7   d post-exposure. Markers of inflammation changed significantly in a dose- and time-dependent manner, which, combined with results from lung histopathology and gene expression analyses suggest an inflammatory response greater than that seen in studies using micron-sized ceria aerosols. Lipidomics of lung tissue revealed changes to minor lipid species, implying specific rather than general cellular effects. Cerium speciation analysis indicated a change in Ce 3+ /Ce 4+ ratio within lung tissue. Collectively, these results in conjunction with earlier studies emphasize the importance of aerosol particle size on toxicity determination. Furthermore, the limited effect resolution within 7   d suggested the possibility of longer-term effects.

Cerium oxide (CeO x ) with a reversible surface Ce 3+ /Ce 4+ redox pair has played an important role in catalytic reactions, whereas catalase mimetics of CeO x have attracted little attention in the field of biotherapy. Herein, a smart photosensitizer-cerium oxide nanoprobe was developed to represent a promising paradigm in high-performance photodynamic therapy. The photosensitizer was linked to CeO x nanoparticles through a substrate peptide (EGPLGVRGK) of matrix metalloproteinase-2 (MMP-2). The smart nanoprobe could be converted from the "silent state" before arriving at the cancer cells to the "activated state" within the cells to turn on the fluorescence and 1 O 2 generation when the peptide linker (EGPLGVRGK) was cut by the cancer biomarker MMP-2. Moreover, CeO x played the role of an excellent catalase-like compound to decompose endogenous hydrogen peroxide to relieve tumor hypoxia. Via the conventional application of CeO x , our study showed innovatively how a smart nanoprobe could relieve tumor hypoxia and achieve a therapeutic effect for highly selective and efficient personalized treatment.

This study aims to assess the role of iron plaque (IP) on cerium (Ce) uptake and translocation by rice after CeO 2 nanoparticles (NPs) exposure over a 4 days period. A hydroponic experiment was performed under two IP levels (low and high) combined with two CeO 2 NPs size (14 nm and 25 nm). It was found that CeO 2 NPs as the main form was absorbed by rice due to limited NPs dissolution in hydroponic solution. IP significantly reduced surface-Ce, root-Ce and shoot-Ce accumulation, irrespective of CeO 2 NPs sizes. The reduced uptake of Ce was more obvious in NP 25 than NP 14 . Ce accumulations decreased with increasing IP amounts. In IP treatments, the interactive attraction between NPs and root surface was weakened through the enhancement of hydrodynamic diameters and the reduction of ζ-potential of CeO 2 NPs in solution, as well as the reduction of |ζ| values of rice root, which reduced the Ce bioaccumulation in rice. PCA indicated the negative correlation between surface-Ce (IP-C-Ce and IP-A-Ce) and NPs size, and between shoot-Ce/root-Ce and IP-Fe/tissue-Fe. IP also decreased Ce translocation from root to shoot. A full life study indicated the reduction effect of IP on surface-Ce, root-Ce, shoot-Ce and grain-Ce accumulations. These findings are significant as they imply that the IP formation is a promising approach for preventing Ce accumulation in rice, which would regulate Ce uptake by rice in the following growth stages and decrease the health risk of CeO 2 NPs exposure in agricultural environment., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Heavy metals and emerging engineered nanoparticles (ENPs) are two current environmental concerns that have attracted considerable attention. Cerium oxide nanoparticles (CeO 2 NPs) are now used in a plethora of industrial products, while cadmium (Cd) is a great environmental concern because of its toxicity to animals and humans. Up to now, the interactions between heavy metals, nanoparticles and plants have not been extensively studied. The main objectives of this study were (i) to determine the synergistic effects of Cd and CeO 2 NPs on the physiological parameters of Brassica and their accumulation in plant tissues and (ii) to explore the underlying physiological/phenotypical effects that drive these specific changes in plant accumulation using Artificial Neural Network (ANN) as an alternative methodology to modeling and simulating plant uptake of Ce and Cd. The combinations of three cadmium levels (0 [control] and 0.25 and 1 mg/kg of dry soil) and two CeO 2 NPs concentrations (0 [control] and 500 mg/kg of dry soil) were investigated. The results showed high interactions of co-existing CeO 2 NPs and Cd on plant uptake of these metal elements and their interactive effects on plant physiology. ANN also identified key physiological factors affecting plant uptake of co-occurring Cd and CeO 2 NPs. Specifically, the results showed that root fresh weight and the net photosynthesis rate are parameters governing Ce uptake in plant leaves and roots while root fresh weight and F v /F m ratio are parameters affecting Cd uptake in leaves and roots. Overall, ANN is a capable approach to model plant uptake of co-occurring CeO 2 NPs and Cd., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Insulin resistance is associated with oxidative stress, mitochondrial dysfunction, and a chronic low-grade inflammatory status. In this sense, cerium oxide nanoparticles (CeO 2 NPs) are promising nanomaterials with antioxidant and anti-inflammatory properties. Thus, we aimed to evaluate the effect of CeO 2 NPs in mouse 3T3-L1 adipocytes, RAW 264.7 macrophages, and C2C12 myotubes under control or proinflammatory conditions. Macrophages were treated with LPS, and both adipocytes and myotubes with conditioned medium (25% LPS-activated macrophages medium) to promote inflammation. CeO 2 NPs showed a mean size of ≤25.3 nm (96.7%) and a zeta potential of 30.57 ± 0.58 mV, suitable for cell internalization. CeO 2 NPs reduced extracellular reactive oxygen species (ROS) in adipocytes with inflammation while increased in myotubes with control medium. The CeO 2 NPs increased mitochondrial content was observed in adipocytes under proinflammatory conditions. Furthermore, the expression of Adipoq and Il10 increased in adipocytes treated with CeO 2 NPs. In myotubes, both Il1b and Adipoq were downregulated while Irs1 was upregulated. Overall, our results suggest that CeO 2 NPs could potentially have an insulin-sensitizing effect specifically on adipose tissue and skeletal muscle. However, further research is needed to confirm these findings.

Owing to the high costs and instability of natural enzymes, the development of enzyme mimics based on inorganic nanomaterials has attracted a wide concern in recent years. In this work, a stable nanocomposite composed of highly dispersed CeO 2 nanoparticles decorated on zeolite Y as support (CeO 2 /Y) was synthesized by a facile wet impregnation method, and the CeO 2 /Y nanocomposite was firstly proposed as an efficient peroxidase-mimicking nanozyme for accurate detection of H 2 O 2 and glucose. The best catalyst was the nanocomposite with CeO 2 to zeolite Y mass ratio of 0.20 (denoted as 20CeO 2 /Y), showing a better affinity and higher catalytic constant to the substrate of H 2 O 2 and 3,3',5,5'-tetramethylbenzidine (TMB) than horseradish peroxidase (HRP) enzymes by the steady-state kinetic analysis. The enzyme-mimicking catalyst could be used over a wider range of pH and temperature for a long-time reuse in TMB oxidation. A facile colorimetric assay was set up for the accurate detection of H 2 O 2 and glucose, with the detection limits of 0.323 μM and 35.4 μM, respectively. The CeO 2 /Y-based peroxidase mimic was used to precisely detect the glucose concentration in real blood serum samples, exhibiting a great potential to be constructed as a reliable biosensor for glucose detection in some complex systems. The superior peroxidase-mimicking performance of CeO 2 /Y nanocomposite is attributed to the synergistic effects of outstanding activity of highly dispersed CeO 2 nanoparticles (5-10 nm) and adsorption properties of zeolite Y with large surface area (517 m 2 ·g -1 ) and pore volume (0.329 cm 3 ·g -1 )., (Copyright © 2018 Elsevier Inc. All rights reserved.)

As alkaline phosphatase (ALP) plays crucial roles in disease warning and dephosphorylation-related cellular regulation, it is widely recognized as an important biomarker for clinical diagnosis. In this work, we proposed a facile colorimetric assay based on phosphate anion-quenched oxidase-mimicking activity of Ce(Ⅳ) ions for sensitive and selective detection of ALP activity. Free Ce(Ⅳ) ions exhibited a strong oxidase-like capability (providing a 40-fold catalytic turnover number compared with CeO 2 ) to catalyze the oxidation of colorless 3,3',5,5'-tetramethylbenzidine (TMB) into its blue product TMBox mediated by dissolved O 2 at neutral pH, thus triggering a remarkable color reaction visually. When PO 4 3- was added, its strong affinity to Ce(Ⅳ) ions rapidly precipitated the free Ce(Ⅳ) ions, resulting in the quenching of their enzymatic ability. Given that ALP catalyzed the hydrolysis of adenosine triphosphate to produce PO 4 3- , determination of ALP activity could be achieved using the colorimetric assay with no need of complicated instrumentation and protocol. As demonstrated, our assay offered a highly sensitive readout for ALP activity in two linear scopes of 0-50 U L -1 and 50-250 U L -1 , providing a detection limit down to 2.3 U L -1 . Besides, it could provide specific response toward ALP against other enzymes and biological species. Furthermore, the developed assay was successfully applied to evaluate ALP activity in human plasma accurately and reliably, indicating its great promise as a powerful and convenient tool for monitoring of ALP activity in clinical practice., (Copyright © 2018 Elsevier B.V. All rights reserved.)

An increasing input rate of rare earth elements in the environment is expected because of the intense extraction of such elements form their ores to face human technological needs. In this study Lemna minor L. plants were grown under laboratory conditions and treated with increasing concentrations of cerium (Ce) ions to investigate the effects on plant growth and antioxidant systems. The growth increased in plants treated with lower Ce concentrations and reduced in plants treated with higher concentrations, compared to control plants. In plants treated with higher Ce concentrations lower levels of chlorophyll and carotenoid and the appearance of chlorotic symptoms were also detected. Increased levels of hydrogen peroxide, antioxidant metabolites and antioxidant activity confirmed that higher Ce concentrations are toxic to L. minor. Ce concentration in plant tissues was also determined and detectable levels were found only in plants grown on Ce-supplemented media. The use of duckweed plants as a tool for biomonitoring of Ce in freshwater is discussed., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Rare earth elements play a pivotal role in high-technology devices, are used as contrast agents for magnetic resonance imaging in clinical settings, are explored as drug carriers for tumor photodynamic therapy, and are used as fertilizers. From the biochemical viewpoint, they act not only as antagonists of Ca 2+ but have been proposed as alternative to Ca 2+ in metallo-enzymes, in particular in Ce 3+ -based methanol dehydrogenases (MDHs). Up to now, the analysis of protein sequence databases identified Ce 3+ -based MHDs only in Archea and Bacteria. Here, we report evidence that Ce 3+ -based MDHs are also present in higher organisms. These enzymes, identified in the parasite Plasmodium yoelii yoelii, in the spider Nephila clavipes, in the Tibetan antelope Pantholops hodgsonii, and in Homo sapiens, are encoded by intronless genes, thus representing a case of multiple, independent lateral gene transfer from Prokaryotes to Eukaryotes. The conservation of residues involved in the Ce 3+ coordination, pyrroquinoline quinone cofactor recognition and in the structure stabilization suggests that these enzymes belong to the Ce 3+ -dependent MDH family, hitherto considered as exclusive of Prokaryotes. © 2018 IUBMB Life, 70(11):1067-1075, 2018., (© 2018 International Union of Biochemistry and Molecular Biology.)

Many nanomaterials have been reported to have enzyme-like activities and are considered as nanozymes. As a multifunctional nanozyme, nanoceria has received much attention due to the dual oxidation states of Ce 3+ /Ce 4+ which facilitate redox reactions at the particle surface. Despite the advantages of nanozymes, their limited activity and lack of enzyme specificity are still problems to be resolved. DNA is used to modulate the oxidase activity of nanoceria because it has recently become an important molecule in bionanotechnology. However, the current research on the effect of DNA on the oxidase mimetic activity of nanoceria is contradictory. It has been discovered that nanoceria used in recent works are different, including in particle size, doping and concentration, and these differences may affect the interaction between DNA and nanoceria, and then affect the oxidase mimetic activity of nanoceria. Hence, it is important to clarify the factors that affect the interaction between DNA with nanoceria. In this work, the interactions between DNA and nanoceria with three different morphologies (nanoparticles, nanocubes, and nanorods) have been investigated. Experimental results show that DNA has different influences on the oxidase mimetic activity of nanoceria with different morphologies. The oxidase mimetic activity of CeO 2 nanoparticles and nanocubes increased, but that of CeO 2 nanorods decreased, after DNA modification. The mechanism of these experimental results has been explored, and it has been found that it is the interaction between cerium and the phosphate backbone of DNA that changes with the different morphologies, resulting in the varying effect of DNA on the oxidase mimetic activity of nanoceria. These results may provide a better understanding of the effect of DNA on the oxidase mimetic activity of nanoceria and promote the applications of nanoceria.