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Background We previously showed that cerium oxide (CeO 2 ), barium sulfate (BaSO 4 ) and zinc oxide (ZnO) nanoparticles (NPs) exhibited different lung toxicity and pulmonary clearance in rats. We hypothesize that these NPs acquire coronas with different protein compositions that may influence their clearance from the lungs. Methods CeO 2 , silica-coated CeO 2 , BaSO 4 , and ZnO NPs were incubated in rat lung lining fluid in vitro. Then, gel electrophoresis followed by quantitative mass spectrometry was used to characterize the adsorbed proteins stripped from these NPs. We also measured uptake of instilled NPs by alveolar macrophages (AMs) in rat lungs using electron microscopy. Finally, we tested whether coating of gold NPs with albumin would alter their lung clearance in rats. Results We found that the amounts of nine proteins in the coronas formed on the four NPs varied significantly. The amounts of albumin, transferrin and α-1 antitrypsin were greater in the coronas of BaSO 4 and ZnO than that of the two CeO 2 NPs. The uptake of BaSO 4 in AMs was less than CeO 2 and silica-coated CeO 2 NPs. No identifiable ZnO NPs were observed in AMs. Gold NPs coated with albumin or citrate instilled into the lungs of rats acquired the similar protein coronas and were cleared from the lungs to the same extent. Conclusions We show that different NPs variably adsorb proteins from the lung lining fluid. The amount of albumin in the NP corona varies as does NP uptake by AMs. However, albumin coating does not affect the translocation of gold NPs across the air-blood barrier. A more extensive database of corona composition of a diverse NP library will develop a platform to help predict the effects and biokinetics of inhaled NPs.

Background Nanomaterials like cerium oxide and barium sulfate are frequently processed in industrial and consumer products and exposure of humans and other organisms is likely. Generally less information is given on health effects and toxicity, especially regarding long-term exposure to low nanoparticle doses. Since inhalation is still the major route of uptake the present study focused on pulmonary effects of CeO 2 NM-212 (0.1, 0.3, 1.0, 3.0 mg/m 3 ) and BaSO 4 NM-220 nanoparticles (50.0 mg/m 3 ) in a 90-day exposure setup. To define particle-related effects and potential mechanisms of action, observations in histopathology, bronchoalveolar lavage and immunohistochemistry were linked to pulmonary deposition and clearance rates. This further allows evaluation of potential overload related effects. Results Lung burden values increased with increasing nanoparticle dose levels and ongoing exposure. At higher doses, cerium clearance was impaired, suggesting lung overload. Barium elimination was extremely rapid and without any signs of overload. Bronchoalveolar lavage fluid analysis and histopathology revealed lung tissue inflammation with increasing severity and post-exposure persistency for CeO 2 . Also, marker levels for genotoxicity and cell proliferation were significantly increased. BaSO 4 showed less inflammation or persistency of effects and particularly affected the nasal cavity. Conclusion CeO 2 nanoparticles penetrate the alveolar space and affect the respiratory tract after inhalation mainly in terms of inflammation. Effects at low dose levels and post-exposure persistency suggest potential long-term effects and a notable relevance for human health. The generated data might be useful to improve nanoparticle risk assessment and threshold value generation. Mechanistic investigations at conditions of non-overload and absent inflammation should be further investigated in future studies.

This study presents a sustainable one-step process for converting raw sugarcane bagasse (SB) into bioethanol, highlighting the innovative use of cerium-doped iron oxide nanoparticles (CeFe 3 O 4 NPs). Initially, these nanoparticles facilitated simultaneous pretreatment and hydrolysis of the raw SB biomass under ambient conditions (50 °C), demonstrating direct catalytic activity by producing 6.55 ± 0.112 g/L glucose and 4.73 ± 0.143 g/L xylose within 24 h. The scalability of this approach was confirmed with similar results achieved in a larger 7.5 L-scale fermentation. A key novelty of this research lies in demonstrating the synergistic effect of CeFe 3 O 4 NPs with enzymatic hydrolysis. By incorporating a minimal amount of in-house generated cellulase enzymes alongside CeFe 3 O 4 NPs, the sugar yields dramatically increased to 23.1 ± 1.12 g/L of glucose and 13.9 ± 0.88 g/L of xylose. This indicates that CeFe 3 O 4 NPs are not merely catalysts but function effectively as promoters, significantly enhancing the efficiency of enzymatic process. The subsequent fermentation using Saccharomyces cerevisiae efficiently converted these sugars, including xylose, into 17.3 ± 0.98 g/L of bioethanol with a productivity of 1.44 g/L/h. Further gene expression studies using quantitative real-time PCR (qRT-PCR) analysis revealed that CeFe 3 O 4 NPs played a role in upregulating xylose-utilizing genes within yeast strain, leading to near-complete utilization of xylose. This stimulation of xylose metabolism is a crucial finding that significantly aids in improving the overall economics of the biomass conversion process. This integrated approach, combining magnetic CeFe 3 O 4 NPs with enzymatic activity and xylose metabolism, represents a significant step towards more cost-effective and scalable bioethanol production from lignocellulosic biomass. Key points • Eco-friendly bioethanol production from sugarcane bagasse using nanobiotechnology • Delignification and hydrolysis of biomass by enzyme-mimicking CeFe3O4 nanoparticles • Xylose utilization by S. cerevisiae noticed due to CeFe3O4 nanoparticles

The extensive mining of bastnasite (CeFCO 3 ) has caused severe pollution of lanthanum (La), cerium (Ce), and fluorine (F) in the surrounding farmland soil, threatening the safety of the soil-plant system. However, the stress effects of the interaction among these three elements on the tolerance and accumulation traits of Brassica chinensis L. ( B. chinensis ) are unclear. In this study, the interaction mechanisms of these three pollutants regulating the growth characteristics, antioxidant capacity, and accumulation characteristics of B. chinensis was explored using pot experiments of La-Ce (LC), Ce-F (CF), La-F (LF), and La-Ce-F (LCF) interactions. The LC interaction pollution treatments at the element concentrations higher than those of LC3 showed significant impact ( P  < 0.05) on the plant growth. The order of tolerance in B. chinensis under four interaction treatments was La-F > Ce-F > La-Ce-F > La-Ce, which was supported by the integrated biomarker response (IBR) analysis. The synergistic effect of La and Ce in La-Ce experiment promoted these two elements in the plants, whereas the presence of F in CF, LF, and LCF combined pollution treatments inhibited the absorption of La and Ce. Moreover, under the interaction among three elements, the synergistic effect of La and Ce in LC treatment enhanced the biotranslocation factor (BTF) of both elements, reaching the highest levels of 0.36 and 0.40, respectively. The addition of F in CF (BTF of 0.3 and 0.15, respectively), LF (BTF of 0.25 and 0.15, respectively), and LCF (BTF of 0.21, 0.24, and 0.15, respectively) treatments reduced the BTF of La and Ce in the plants due to the formation of insoluble precipitates between F with La or Ce. In conclusion, the interaction between La and Ce could reduce the tolerance of B. chinensis , while the presence of F could enhance the plant resistance to both La and Ce.

In aerobic methanotrophs, copper and cerium control the expression and activity of different forms of methane monooxygenase and methanol dehydrogenase, respectively. To exploit methanotrophy for the valorization of methane, it is crucial to determine if these metals exert more global control on gene expression in methanotrophs. Using RNA-Seq analysis we compared the transcriptome of Methylosinus trichosporium OB3b grown in the presence of varying amounts of copper and cerium. When copper was added in the absence of cerium, expression of genes encoding for both soluble and particulate methane monooxygenases varied as expected. Genes encoding for copper uptake, storage, and efflux also increased, indicating that methanotrophs must carefully control copper homeostasis. When cerium was added in the absence of copper, expression of genes encoding for alternative methanol dehydrogenases varied as expected, but few other genes were found to have differential expression. When cerium concentrations were varied in the presence of copper, few genes were found to be either up- or downregulated, indicating that copper over rules any regulation by cerium. When copper was increased in the presence of cerium, however, many genes were upregulated, most notably multiple steps of the central methane oxidation pathway, the serine cycle, and the ethylmalonyl-CoA pathway. Many genes were also downregulated, including those encoding for nitrogenase and hydrogenase. Collectively, these data suggest that copper plays a larger role in regulating gene expression in methanotrophs, but that significant changes occur when both copper and cerium are present.

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. Graphical Abstract

Particles present in diesel exhaust have been proposed as a significant contributor to the development of acute and chronic lung diseases, including respiratory infection and allergic asthma. Nanoceria (CeO2 nanoparticles) are used to increase fuel efficiency in internal combustion engines, are present in exhaust fumes, and could affect cells of the airway. Components from the environment such as biologically derived proteins, carbohydrates, and lipids can form a dynamic layer, commonly referred to as the \"protein corona\" which alters cellular nanoparticle interactions and internalization. Using confocal reflectance microscopy, we quantified nanoceria uptake by lung-derived cells in the presence and absence of a serum-derived protein corona. Employing mass spectrometry, we identified components of the protein corona, and demonstrated that the interaction between transferrin in the protein corona and the transferrin receptor is involved in mediating the cellular entry of nanoceria via clathrin-mediated endocytosis. Furthermore, under these conditions nanoceria does not affect cell growth, viability, or metabolism, even at high concentration. Alternatively, despite the antioxidant capacity of nanoceria, in serum-free conditions these nanoparticles induce plasma membrane disruption and cause changes in cellular metabolism. Thus, our results identify a specific receptor-mediated mechanism for nanoceria entry, and provide significant insight into the potential for nanoparticle-dependent toxicity.

The goal of this work was to investigate the relevant dosimetric and luminescent properties of MgO:Li 3% ,Ce 0.03% ,Sm 0.03% , a newly-developed, high sensitivity Optically Stimulated Luminescence (OSL) material of low effective atomic number ( Z eff  = 10.8) and potential interest for medical and personal dosimetry. We characterized the thermoluminescence (TL), OSL, radioluminescence (RL) and OSL emission spectrum of this new material and carried out a preliminary investigation on the OSL signal stability. MgO:Li,Ce,Sm has a main TL peak at ~180 °C (at a heating rate of 5 °C/s) associated with Ce 3+ and Sm 3+ emission. The results indicate that the infrared (870 nm) stimulated OSL from MgO:Li,Ce,Sm has suitable properties for dosimetry, including high sensitivity to ionizing radiation (20 times that of Al 2 O 3 :C, under the measurement conditions) and wide dynamic range (7 μGy–30 Gy). The OSL associated with Ce 3+ emission is correlated with a dominant, practically isolated peak at 180 °C. Fading of ~15% was observed in the first hour, probably due to shallow traps, followed by subsequent fading of 6–7% over the next 35 days. These properties, together with the characteristically fast luminescence from Ce 3+ , make this material also a strong candidate for 2D OSL dose mapping.

Although the toxicological impact of metal oxide nanoparticles has been studied for the last few decades on aquatic organisms, the exact mechanism of action is still unclear. The fate, behavior, and biological activity of nanoparticles are dependent on physicochemical factors like size, shape, surface area, and stability in the medium. This study deals with the effect of nano and bulk CeO 2 particles on marine microcrustacean, Artemia salina . The primary size was found to be 15 ± 3.5 and 582 ± 50 nm for nano and bulk CeO 2 (TEM), respectively. The colloidal stability and sedimentation assays showed rapid aggregation of bulk particles in seawater. Both the sizes of CeO 2 particles inhibited the hatching rate of brine shrimp cyst. Nano CeO 2 was found to be more toxic to A. salina (48 h LC 50 38.0 mg/L) when compared to bulk CeO 2 (48 h LC 50 92.2 mg/L). Nano CeO 2 -treated A. salina showed higher oxidative stress (ROS) than those treated with the bulk form. The reduction in the antioxidant activity indicated an increase in oxidative stress in the cells. Higher acetylcholinesterase activity (AChE) was observed upon exposure to nano and bulk CeO 2 particles. The uptake and accumulation of CeO 2 particles were increased with respect to the concentration and particle size. Thus, the above results revealed that nano CeO 2 was more lethal to A. salina as compared to bulk particles.

BACKGROUND AND AIMS: Plant growth responses to the rare earth elements lanthanum (La) and cerium (Ce) have been reported, but little is known about the effects of these two elements on plant mineral nutrition. METHODS: Corn (Zea mays 'Hycorn 82') and mungbean (Vigna radiata 'Berken') were grown in continuous flowing nutrient solutions containing 0, 0·2, 1·0 and 5·0 μM La or Ce. At harvest plants were divided into roots and shoots, dried, weighed and analysed for macro- and micronutrients, as well as for La and Ce. KEY RESULTS: La and Ce did not increase the growth of corn or mungbean. The dry weight of corn shoots was decreased by 32 % in the presence of 5·0 μM Ce; the other La and Ce concentrations had no effect. La and Ce concentrations of 0·9 and 5·0 μM decreased the shoot dry weight of mungbean by 75 or 95 %, the two elements having closely similar effects. Decreases in the uptake of Ca, Na, Zn and Mn by corn were observed with increases in solution La and Ce. For mungbean, the uptake rates of all measured elements decreased with increases in solution La and Ce. The concentrations of La and Ce in the roots of both species were higher than in the shoots and increased strongly with increasing concentrations of La or Ce in solution. The La and Ce concentrations in mungbean shoots were always higher than in corn shoots. CONCLUSIONS: La and Ce did not enhance the growth of corn or mungbean, but decreased the growth, root function and consequently the nutritional status of mungbean at concentrations >0·2 μM in solution. It is concluded that if La or Ce have positive effects on corn and mungbean growth, they can only occur at solution concentrations below 0·2 μM.