Synthesis of ultrasmall cerium oxide nanoparticles in deep eutectic solvent and their application in an electrochemical sensor to detect dopamine in biological fluid.

A solvothermal synthesis of ultrasmall cerium oxide nanoparticles (USCeOxNPs) with an average size of 0.73 ± 0.07 nm using deep eutectic solvent (DES) as a stabilizing medium at a temperature of 90 ºC is reported. Transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) were used to morphologically characterize the USCeOxNPs. These revealed approximately spherical shapes with emission lines characteristic of cerium. Selected area electron diffraction (SAED) was used to determine the crystalline structure of the cerium oxide nanoparticles (CeO2NPs), revealing the presence of crystalline cubic structures. The USCeOxNPs-DES/CB film was characterized by scanning electron microscopy (SEM), which demonstrated the spherical characteristic of CB with layers slightly covered by DES residues. DES was characterized by Fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR), indicating its formation through hydrogen bonds between the precursors. An electrochemical sensor for dopamine (DA) determination in biological fluids was developed using the USCeOxNPs together with carbon black (CB). An enhanced current response was observed on DA voltammetric determination, and this can be attributed to the USCeOxNPs. This sensor displayed linear responses for DA in the range 5.0 × 10-7 mol L-1 to 3.2 × 10-4 mol L-1, with a limit of detection of 80 nmol L-1. Besides detectability, excellent performances were verified for repeatability and anti-interference. The sensor based on USCeOxNPs synthesized in DES in a simpler and environmentally friendly way was successfully applied to determine DA in biological matrix.

Geniposide and Harpagoside Functionalized Cerium Oxide Nanoparticles as a Potential Neuroprotective.

Alzheimer's disease is associated with protein aggregation, oxidative stress, and the role of acetylcholinesterase in the pathology of the disease. Previous investigations have demonstrated that geniposide and harpagoside protect the brain neurons, and cerium nanoparticles (CeO2 NPs) have potent redox and antioxidant properties. Thus, the effect of nanoparticles of Ce NPs and geniposide and harpagoside (GH/CeO2 NPs) on ameliorating AD pathogenesis was established on AlCl3-induced AD in mice and an aggregation proteins test in vitro. Findings of spectroscopy analysis have revealed that GH/CeO2 NPs are highly stable, nano-size, spherical in shape, amorphous nature, and a total encapsulation of GH in cerium. Treatments with CeO2 NPs, GH/CeO2 NPs, and donepezil used as positive control inhibit fibril formation and protein aggregation, protect structural modifications in the BSA-ribose system, have the ability to counteract Tau protein aggregation and amyloid-ß1-42 aggregation under fibrillation condition, and are able to inhibit AChE and BuChE. While the GH/CeO2 NPs, treatment in AD induced by AlCl3 inhibited amyloid-ß1-42, substantially enhanced the memory, the cognition coordination of movement in part AD pathogenesis may be alleviated through reducing amyloidogenic pathway and AChE and BuChE activities. The findings of this work provide important comprehension of the chemoprotective activities of iridoids combined with nanoparticles. This could be useful in the development of new therapeutic methods for the treatment of neurodegenerative diseases.

Brazilin-Ce nanoparticles attenuate inflammation by de/anti-phosphorylation of IKKß.

Inflammation is associated with a series of diseases like cancer, cardiovascular disease and infection, and phosphorylation/dephosphorylation modification of proteins are important in inflammation regulation. Here we designed and synthesized a novel Brazilin-Ce nanoparticle (BX-Ce NPs) using Brazilin, which has been used for anti-inflammation in cardiovascular diseases but with narrow therapeutic window, and Cerium (IV), a lanthanide which has the general activity in catalyzing the hydrolysis of phosphoester bonds, to conferring de/anti-phosphorylation of IKKß. We found that BX-Ce NPs specifically bound to Asn225 and Lys428 of IKKß and inhibited its phosphorylation at Ser181, contributing to appreciably anti-inflammatory effect in cellulo (IC50 = 2.5 µM). In vivo mouse models of myocardial infarction and sepsis also showed that the BX-Ce NPs significantly ameliorated myocardial injury and improved survival in mice with experimental sepsis through downregulating phosphorylation of IKKß. These findings provided insights for developing metal nanoparticles for guided ion interfere therapy, particularly synergistically target de/anti-phosphorylation as promising therapeutic agents for inflammation and related diseases.

Recovery of Ce and La from phosphogypsum leachate by adsorption using grape wastes.

The present research aimed to evaluate the use of grape stalk in the adsorption of lanthanum and cerium to identify the best operating conditions enabling the application of the bioadsorbent in REEs leached from phosphogypsum. The grape stalk was characterized and showed an amorphous structure with a heterogeneous and very porous surface. Also, it was possible to identify the groups corresponding to carboxylic acids, phenols, alcohols, aliphatic acids, and aromatic rings. The pH effect study showed that the adsorption process of La3+ and Ce3+ ions was favored at pH 5.0. The adsorption kinetics followed the pseudo-second-order model. In just 20 min, 80% saturation was reached, while equilibrium was reached after 120 min. The adsorption isotherms were appropriately adjusted to the Langmuir model, and the maximum adsorption capacities were obtained at 298 K, which were 35.22 mg g-1 for La3+ and 37.99 mg g-1 for Ce3+. Furthermore, the adsorption process was favorable, spontaneous, and exothermic. In the study's second phase, phosphogypsum was leached with a sulfuric acid solution. Then, the adsorption of REEs was carried out under the experimental conditions of pH after leaching and pH 5.0 (adjustment carried out with sodium hydroxide solution) at 298 K for 120 min and with adsorbent dosages of 1 and 5 g L-1. This process resulted in removal percentages above 95% for the most abundant REEs, such as neodymium, lanthanum, and cerium, at pH 5.0 and a dosage of 5 g L-1, demonstrating the effectiveness of the bioadsorbent used. These results indicate the potential of using grape residue as a promising bioadsorbent in recovering rare earth elements from phosphogypsum leachate.

Effectiveness of Cerium Oxide Nanoparticles in Non-Alcoholic Fatty Liver Disease Evolution Using In Vivo and In Vitro Studies: A Systematic Review.

Nonalcoholic fatty liver disease (NAFLD) describes a spectrum of liver abnormalities, from benign steatosis to nonalcoholic steatohepatitis (NASH). Because of their antioxidant capabilities, CeNPs have sparked a lot of interest in biological applications. This review evaluated the effectiveness of CeNPs in NAFLD evolution through in vivo and in vitro studies. Databases such as MEDLINE, EMBASE, Scopus, and Web of Science were looked for studies published between 2012 and June 2023. Quality was evaluated using PRISMA guidelines. We looked at a total of nine primary studies in English carried out using healthy participants or HepG2 or LX2 cells. Quantitative data such as blood chemical markers, lipid peroxidation, and oxidative status were obtained from the studies. Our findings indicate that NPs are a possible option to make medications safer and more effective. In fact, CeNPs have been demonstrated to decrease total saturated fatty acids and foam cell production (steatosis), reactive oxygen species production and TNF-α (necrosis), and vacuolization in hepatic tissue when used to treat NAFLD. Thus, CeNP treatment may be considered promising for liver illnesses. However, limitations such as the variation in durations between studies and the utilization of diverse models to elucidate the etiology of NAFLD must be considered. Future studies must include standardized NAFLD models.

Comparative Study of the Effect of Doping ZnTiO3 with Rare Earths (La and Ce) on the Adsorption and Photodegradation of Cyanide in Aqueous Systems.

Cyanide is a highly toxic compound that can pose serious health problems to both humans and aquatic organisms. Therefore, the present comparative study focuses on the removal of total cyanide from aqueous solutions by photocatalytic adsorption and degradation methods using ZnTiO3 (ZTO), La/ZnTiO3 (La/ZTO), and Ce/ZnTiO3 (Ce/ZTO). The nanoparticles were synthesized by the sol-gel method and characterized by X-ray powder diffractometry (XRD), Scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS), Diffuse reflectance spectroscopy (DRS), and Specific surface area (SSA). The adsorption equilibrium data were fitted to the Langmuir and Freundlich isotherm models. Adsorption kinetics were also evaluated using the pseudo-first-order and pseudo-second-order models and the intraparticle diffusion model. Likewise, the photodegradation of cyanide under simulated sunlight was investigated and the reusability of the synthesized nanoparticles for cyanide removal in aqueous systems was determined. The results demonstrated the effectiveness of doping with lanthanum (La) and cerium (Ce) to improve the adsorbent and photocatalytic properties of ZTO. In general, La/ZTO showed the maximum percentage of total cyanide removal (99.0%) followed by Ce/ZTO (97.0%) and ZTO (93.6%). Finally, based on the evidence of this study, a mechanism for the removal of total cyanide from aqueous solutions using the synthesized nanoparticles was proposed.

Cerium oxide-doped PEDOT nanocomposite for label-free electrochemical immunosensing of anti-p53 autoantibodies.

A label-free nanoimmunosensor is reported based on p53/CeO2/PEDOT nanobiocomposite-decorated screen-printed gold electrodes (SPAuE) for the electrochemical detection of anti-p53 autoantibodies. CeO2 nanoparticles (NPs) were synthesized and stabilized with cyanopropyltriethoxysilane by a soft chemistry method. The nanoimmunosensing architecture was prepared by in situ electropolymerization of 3,4-ethylenedioxythiophene (EDOT) on SPAuE in the presence of CeO2 NPs. The CeO2 NPs and Ce/PEDOT/SPAuE were characterized by scanning and transmission electron microscopy, dynamic and electrophoretic light scattering, ultraviolet-visible spectrophotometry, X-ray diffraction, Fourier-transform infrared spectroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. Ce/PEDOT/SPAuE was biofunctionalized with p53 antigen by covalent bonding for the label-free determination of anti-p53 autoantibodies by differential pulse voltammetry. The nanobiocomposite-based nanoimmunosensor detected anti-p53 autoantibodies in a linear range from 10 to 1000 pg mL-1, with a limit of detection (LOD) of 3.2 pg mL-1. The nanoimmunosensor offered high specificity, selectivity, and long-term storage stability with great potential to detect anti-p53 autoantibodies in serum samples. Overall, incorporating organo-functional nanoparticles into polymeric matrices can provide a simple-to-assemble, rapid, and ultrasensitive approach for on-site screening of anti-p53 autoantibodies and other disease-related biomarkers with low sample volumes.

New bimetallic adsorbent material based on cerium-iron nanoparticles highly selective and affine for arsenic(V).

Bimetallic oxy(hydroxides) have gain great interest in water treatment systems based on adsorption processes. Their high OH groups density, in addition to inheriting the oxides properties make them highly promising adsorbents of anions. In this work, highly affine and selective bimetallic oxyhydroxides of cerium and iron (Ce:Fe-P's) for arsenic(V) were synthesized by implementing an assisted microwave methodology. The Ce:Fe-P's were characterized by various techniques (SEM, FTIR, XRD and XPS) and the As(V) adsorption capacity and kinetics as well as the effect of pH and the presence of coexisting anions were determined. The results showed that Ce:Fe-P's have an outstanding As(V) adsorption capacity (179.8 mg g-1 at Ce = 3 mg L-1) even at low concentrations (120 mg g-1 at Ce = 37 µg L-1). Moreover, the adsorption equilibrium was reached very fast, just in 3 min, with an adsorption rate of 0.123 mg min-1, that is, 80% of the initial As(V) concentration of 5 mg L-1 was removed in the first 3 min. The arsenic adsorption capacity decreased only up to 20% at pH above 7, attributed to electrostatic repulsions due to the adsorbent's pHPZC, which was 6.8. On the other hand, the arsenic adsorption capacity of Ce:Fe-P's decreased just 21% in the presence of 10 mg L-1 of each of the following competing anions: F-, Cl-, SO42-, NO3-, PO43- and CO32-, which usually coincide in contaminated water with As(V). Ce:Fe-P's has proven to be one of the most promising As(V) adsorbent materials reported so far in the literature, because it presented an outstanding adsorption capacity and at the same time a very fast adsorption speed. Furthermore, the pH and the concentration of coexisting anions caused little interference in the adsorption processes. Due to the above, the Ce:Fe-P's is already in the process of intellectual protection.

Synthesis and defect characterization of hybrid ceria nanostructures as a possible novel therapeutic material towards COVID-19 mitigation.

This study reports the synthesis of hybrid nanostructures composed of cerium dioxide and microcrystalline cellulose prepared by the microwave-assisted hydrothermal route under distinct temperature and pH values. Their structural, morphological and spectroscopic behaviors were investigated by X-Rays Diffraction, Field Emission Gun Scanning Electron Microscopy, High-Resolution Transmission Electron Microscopy, and Fourier-Transform Infrared, Ultraviolet-Visible, Raman and Positron Annihilation Lifetime spectroscopies to evaluate the presence of structural defects and their correlation with the underlying mechanism regarding the biocide activity of the studied material. The samples showed mean crystallite sizes around 10 nm, characterizing the formation of quantum dots unevenly distributed along the cellulose surface with a certain agglomeration degree. The samples presented the characteristic Ce-O vibration close to 450 cm-1 and a second-order mode around 1050 cm-1, which is indicative of distribution of localized energetic levels originated from defective species, essential in the scavenging of reactive oxygen species. Positron spectroscopic studies showed first and second lifetime components ranging between 202-223 ps and 360-373 ps, respectively, revealing the presence of two distinct defective oxygen species, in addition to an increment in the concentration of Ce3+-oxygen vacancy associates as a function of temperature. Therefore, we have successfully synthesized hybrid nanoceria structures with potential multifunctional therapeutic properties to be further evaluated against the COVID-19.

Reduction-Driven 3D to 2D Transformation of Cu Nanoparticles.

The interaction between metal and metal oxides at the nanoscale is of uttermost importance in several fields, thus its enhancement is highly desirable. In catalysis, the performance of the nanoparticles is dependent on a wide range of properties, including its shape that is commonly considered stable during the catalytic reaction. In this study, highly reducible CeO2-x nanoparticles are synthesized aiming to provide Cu/CeO2-x nanoparticles, which are classically active catalysts for the CO oxidation reaction. It is observed that the Cu nanoparticles shape changes during reduction treatment (prior to the CO oxidation reaction) from a nearly spherical 3D to a planar 2D shape, then enhances the Cu-CeO2-x interaction. The spread of the Cu nanoparticles over the CeO2-x surface during the reduction treatment occurs due to the minimization of the total system energy. The shape change is accompanied by migration of O atoms from CeO2 surface to the border of the Cu nanoparticles and the change from the Cu0 to Cu+1 state. The spreading of the Cu nanoparticles influences on the reactivity results toward the CO oxidation reaction since it changes the local atomic order around Cu atoms. The results show a timely contribution for enhancing the interaction between metal and metal oxide.

Cerium oxide nanoparticle conjugation to microRNA-146a mechanism of correction for impaired diabetic wound healing.

Diabetic wounds represent a significant healthcare burden and are characterized by impaired wound healing due to increased oxidative stress and persistent inflammation. We have shown that CNP-miR146a synthesized by the conjugation of cerium oxide nanoparticles (CNP) to microRNA (miR)-146a improves diabetic wound healing. CNP are divalent metal oxides that act as free radical scavenger, while miR146a inhibits the pro-inflammatory NFκB pathway, so CNP-miR146a has a synergistic role in modulating both oxidative stress and inflammation. In this study, we define the mechanism(s) by which CNP-miR146a improves diabetic wound healing by examining immunohistochemical and gene expression analysis of markers of inflammation, oxidative stress, fibrosis, and angiogenesis. We have found that intradermal injection of CNP-miR146a increases wound collagen, enhances angiogenesis, and lowers inflammation and oxidative stress, ultimately promoting faster closure of diabetic wounds.

Engineered nanoceria modulate neutrophil oxidative response to low doses of UV-B radiation through the inhibition of reactive oxygen species production.

To avoid aging and ultraviolet mediated skin disease the cell repair machinery must work properly. Neutrophils, also known as polymorphonuclear leukocytes, are the first and most abundant cell types which infiltrate sites of irradiation and play an important role in restoring the microenvironment homeostasis. However, the infiltration of neutrophils in ultraviolet-B (UV-B) irradiated skin might also contribute to the pathophysiology of skin disease. The polymorphonuclear leukocytes activation induced by UV-B exposure may lead to prolonged, sustained NADPH oxidase activation followed by an increase in reactive oxygen species (ROS) production. Our previous work showed that cerium oxide nanoparticles can protect L929 fibroblasts from ultraviolet-B induced damage. Herein, we further our investigation of engineered cerium oxide nanoparticles (CNP) in conferring radiation protection specifically in modulation of neutrophils' oxidative response under low dose of UV-B radiation. Our data showed that even low doses of UV-B radiation activate neutrophils' oxidative response and that the antioxidant, ROS-sensitive redox activities of engineered CNPs are able to inhibit the effects of NADPH oxidase activation while conferring catalase and superoxide dismutase mimetic activity. Further, our investigations revealed similar levels of total ROS scavenging for both CNP formulations, despite substantial differences in cerium redox states and specific enzyme-mimetic reaction activity. We therefore determine that CNP activity in mitigating the effects of neutrophils' oxidative response, through the decrease of ROS and of cell damage such as chromatin condensation, suggests potential utility as a radio-protectant/therapeutic against UV-B damage.

Ingestion and effects of cerium oxide nanoparticles on Spodoptera frugiperda (Lepidoptera: Noctuidae).

The objective of this study was to evaluate the biological and nutritional characteristics of Spodoptera frugiperda (Lepidoptera: Noctuidae), an arthropod pest widely distributed in agricultural regions, after exposure to nano-CeO2 via an artificial diet and to investigate the presence of cerium in the body of this insect through X-ray fluorescence mapping. Nano-CeO2, micro-CeO2, and Ce(NO3)3 were incorporated into the diet (0.1, 1, 10, and 100 mg of Ce L-1). Cerium was detected in caterpillars fed with diets containing nano-CeO2 (1, 10 and 100 mg of Ce L-1), micro-CeO2 and Ce(NO3)3, and in feces of caterpillars from the first generation fed diets with nano-CeO2 at 100 mg of Ce L-1 as well. The results indicate that nano-CeO2 caused negative effects on S. frugiperda. After it was consumed by the caterpillars, the nano-CeO2 reduced up to 4.8% of the pupal weight and 60% of egg viability. Unlike what occurred with micro-CeO2 and Ce(NO3)3, nano-CeO2 negatively affected nutritional parameters of this insect, as consumption rate two times higher, increase of up to 80.8% of relative metabolic rate, reduction of up to 42.3% efficiency of conversion of ingested and 47.2% of digested food, and increase of up to 1.7% of metabolic cost and 8.7% of apparent digestibility. Cerium caused 6.8-16.9% pupal weight reduction in second generation specimens, even without the caterpillars having contact with the cerium via artificial diet. The results show the importance of new ecotoxicological studies with nano-CeO2 for S. frugiperda in semi-field and field conditions to confirm the toxicity.

Tuning the photoactivity of TiO2 nanoarchitectures doped with cerium or neodymium and application to colour removal from wastewaters.

The impact of cerium (Ce) and neodymium (Nd) rare-earth metal doping of TiO2 prepared by the hydrothermal method was investigated to tailor effective photocatalytic degradation of coloured wastewater under UV or visible illumination. The hydrothermal treatment of TiO2 decreased the pHpzc from 6.3 to 3.1-3.8 favouring the affinity for cationic water contaminants. Doping with Ce and Nd modified the crystallinity and the morphology of the photocatalysts and significantly increased the BET surface area and the adsorption capacity of cationic dyes. The photocatalytic activity under UV light irradiation decreased due to shielding of the catalyst active area by excessive amount of dye adsorbed. Conversely, the photocatalytic activity of the Ce and Nd doped TiO2 increased under visible light irradiation by 1.2 times as a result of the dye photosensitization effect. It was demonstrated that two-steps dark adsorption and photocatalytic reaction or one-step simultaneous adsorption and reaction can produce significantly different results for the photocatalytic degradation of dyes in coloured waters, the rate being controlled by the competitive adsorption of the reacting organics and the H2O/OH- species. The reaction is driven by the radical oxygen species (ROS) formed on the catalyst surface the nature of which, differs under UV or visible light irradiation. The Ce-doped TiO2 and Nd-doped TiO2 photocatalysts with 0.5% rare-earth content were found to be efficient in the degradation of MB in aqueous solution, removing the colour and reducing the toxicity of wastewaters.

Effect of nano cerium oxide on soybean (Glycine max L. Merrill) crop exposed to environmentally relevant concentrations.

This study evaluated the uptake and translocation of cerium nanoparticles (CeO2 NPs) and soluble Ce(NO3)3 by soybean plants (Glycine max L. Merrill) under the whole plant life-cycle and relevant environmental concentrations, 0.062 and 0.933 mg kg-1, which represent maximal values for 2017 in agricultural soils and sludge treated soils, respectively. The experiments were carried out using a nutrient solution. Cerium was detected in the soybean roots epidermis and cortex, leaves, and grains, but it neither impaired plant development nor grain yield. The concentration of Ce in the shoot increased as a function of time for plants treated with Ce(NO3)3, while it remained constant for plants treated with CeO2 NPs. It means that CeO2 NPs were absorbed in the same rate as biomass production, which suggests that they are taken up and transported by water mass flow. Single-particle inductively coupled plasma mass spectrometry revealed clusters of CeO2 NPs in leaves of plants treated with 25 nm CeO2 NPs (ca. 30-45 nm). The reprecipitation of soluble cerium from Ce(NO3)3 within the plant was not confirmed. Finally, bioconcentration factors above one were found for the lowest concentrated treatments. Since soybean is a widespread source of protein for animals, we draw attention to the importance of evaluating the effects of Ce entrance in the food chain and its possible biomagnification.

Cerium-modified iron oxides applied as catalysts in the heterogeneous Fenton system for degradation of cephalexin.

The effect of incorporation of different amounts of cerium on iron oxides and different heat treatment temperatures was evaluated for the degradation of cephalexin (CEX) using heterogeneous Fenton and photo-Fenton processes. The materials were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), specific area (BET), and zeta potential (ZP). The conversion of magnetite to maghemite was observed when a 140 °C thermal treatment was applied. The insertion of cerium resulted in a loss of the uniform spherical shape of the particles. The material containing the lowest amount of cerium (0.5% w/w) presented an increase in the specific area from 91.2 to 171.6 m2 g-1 relative to the pure iron oxide, while with 2% (w/w) a decrease to 99.2 m2 g-1 was observed for the materials treated at 70 °C. The same behavior was observed for materials treated at 140 °C, however, with smaller areas. At pH 6.0, a low catalytic activity was observed contrasting to the high consumption of H2O2, suggesting its catalytic decomposition into water and oxygen. This was confirmed by the very low production of HO• in the degradation system. On the other hand, the high production of HO• was observed at pH 3.5, which was chosen as a working pH. The material treated at 140 °C and containing 1% Ce (w/w) was the highlight, promoting degradation of 0.052 mg of CEX per m2 area of the catalyst after 150 min using 1.0 mmol L-1 of H2O2. The CEX intermediates identified indicated hydroxylation as the major route of degradation.

Synthesis of silver-cerium titanate nanotubes and their surface properties and antibacterial applications.

Nano-heterostructures of titanate nanotubes were synthesized and they revealed a complex structure with the formation of TiO2 (anatase), CeO2, Ag2O and metallic silver nanoparticles on the outer walls and intercalation of Ce4+ and Ag+ into the interlayer spaces of the nanotubes by microwave-assisted hydrothermal process and subjected to ion exchange reactions. To the best of our knowledge, this is the first reported silver and cerium co-exchanged titanate nanotubes for bio-applications. The co-ion exchange processes preserved the original tubular structure of titanate nanotubes with significant changes of the superficial as well as interlamellar environment. This study opens up possibility of synthesizing complex, functional nano-heterostructure with the scope of modification of the final structure, especially the amount and oxidation state of the intercalated cation (Ce4+, Ce3+ and Ag+) as well as the quantity and variety of the decorating nanoparticles (CeO2, Ag2O or metallic Ag). The interplay of which, in turn, can lead to important biological properties and applications, owing to their ion-liberation capacity. The samples were tested in antibacterial activity with two different kind of bacteria (gram positive and negative), cell cytotoxicity and adhesion, and it was found that the nano-heterostructure formed shows high antibacterial activity with low cytotoxicity and high cell adhesion, which makes it a promising material for further health applications.

Antioxidative photochemoprotector effects of cerium oxide nanoparticles on UVB irradiated fibroblast cells.

The Ultraviolet-B radiation (UVB) might induce cellular redox imbalance which plays an important role in the development of skin disorders. Thus, the search for photochemoprotective alternatives with antioxidant efficacy would be a safe aspect towards prevention of skin diseases. Cerium oxide nanoparticles (CNPs) have antioxidant properties, that are mostly related to CNPs catalase and superoxide dismutase (SOD)-like antioxidative mimetic activity. Considering that, we investigated whether CNPs induce photochemoprotection against UVB-induced cellular damages on L929 fibroblasts. Our results showed that CNPs prevented UVB mediated L929 cell oxidative damage by reestablishing the oxidative balance through ameliorating the reactive oxygen species (ROS) level and enhancing the antioxidant enzyme activities.

Surface composition and catalytic activity of an iron mining residue for simultaneous degradation of sulfonamide antibiotics.

Iron mining residue was evaluated as a potential catalyst for heterogeneous Fenton/photo-Fenton degradation of sulfonamide antibiotics. The residue contained 25% Fe2O3 and 8% CeO2, as determined by X-ray fluorescence spectroscopy, as well as other minor phases such as P2O5, SiO2, and TiO2. X-ray photoelectron spectroscopy analysis revealed a lower content of iron oxides on the surface, which restricted interaction of the residue with H2O2. Despite this limitation and the relatively low specific surface area (26 m2 g-1) of the crude iron mining residue (without any pretreatment), the material presented high catalytic activity for Fenton degradation of sulfonamide antibiotics. The degradation was strongly dependent on the initial pH, showing the highest efficiency at pH 2.5. For this condition, a concentration of sulfathiazole below the detection limit was obtained within 30 min, under black light irradiation and using 0.3 g L-1 residue, with low H2O2 consumption (0.2 mmol L-1). The residue also provided highly efficient sulfathiazole degradation in the dark, with the concentration of the antibiotic decreasing to an undetectable level after 45 min. Simultaneous degradation of two sulfonamide antibiotics revealed higher recalcitrance of sulfamethazine, compared to sulfathiazole, but the levels of both antibiotics decreased to below the detection limit after 45 min. The residue was very stable, since no significant concentration of soluble iron was detected after the degradation process. Furthermore, high catalytic activity was maintained during up to five cycles, showing the potential of this material for use as a low-cost and environmentally compliant catalyst in Fenton processes.

Ecological risk assessment of cerium for tropical agroecosystems.

Cerium (Ce) is present in high technology materials and in mineral P fertilizers and the use and discharge of such resources may change the natural status of Ce in the soil environment. Brazilian soils in farming areas are significantly exposed to increased levels of unintentionally-added Ce through intensive input of phosphate fertilizers. The aims of this study were to evaluate the ecotoxicological risk to plants growing in tropical soils contaminated with Ce, as well as to create a database to support future legislation regulating the limits of this element in Brazilian and conceivably other tropical soils. Eight crop species (corn, sorghum, rice, wheat, soybeans, sunflower, radish, and beans) were exposed to a Ce concentration gradient in two typical tropical soils (Oxisol and Inceptsol), and an artificial soil. Our findings showed that among the endpoints measured, Ce phytotoxicity was more pronounced on shoot dry matter than on percent germination and germination speed index. Sensitivity of plants is species specific and our data showed that sunflower and radish exposed to Ce were the most sensitive crop species. Soil properties such as pH, cation exchange capacity, and organic carbon may have influenced the severity of Ce phytotoxicity. Because of that, the Oxisol contaminated with this element caused higher phytotoxicity than the other soils tested. Our risk assessment results (hazardous concentration, HC5 = 281.6 mg Ce kg-1) support the idea that unintentional Ce input through P fertilizers does not pose a risk to soils of Brazilian agroecosystems.