Environmental geochemistry of cerium: applications and toxicology of cerium oxide nanoparticles

Cerium oxide nanoparticles in wound care: a review of mechanisms and therapeutic applications

Skin wound healing is a complex and tightly regulated process. The frequent occurrence and reoccurrence of acute and chronic wounds cause significant skin damage to patients and impose socioeconomic burdens. Therefore, there is an urgent requirement to promote interdisciplinary development in the fields of material science and medicine to investigate novel mechanisms for wound healing. Cerium oxide nanoparticles (CeO2 NPs) are a type of nanomaterials that possess distinct properties and have broad application prospects. They are recognized for their capabilities in enhancing wound closure, minimizing scarring, mitigating inflammation, and exerting antibacterial effects, which has led to their prominence in wound care research. In this paper, the distinctive physicochemical properties of CeO2 NPs and their most recent synthesis approaches are discussed. It further investigates the therapeutic mechanisms of CeO2 NPs in the process of wound healing. Following that, this review critically examines previous studies focusing on the effects of CeO2 NPs on wound healing. Finally, it suggests the potential application of cerium oxide as an innovative nanomaterial in diverse fields and discusses its prospects for future advancements.

The cerium oxide nanoparticles toxicity induced physiological, histological and biochemical alterations in freshwater mussels, Unio crassus

INTRODUCTION

Releasing of cerium oxide nanoparticles (nano-CeO2) to the nature has increased due to the widespread use in many fields ranging from cosmetics to the food industry. Therefore, nano-CeO2 has been included in the Organization for Economic Co-operation and Development's (OECD) priority list for engineering nanomaterials. In this study, the effects of nano-CeO2 on the freshwater mussels were investigated to reveal the impact on the freshwater systems on model organism.

METHODS

First, the chemical and structural properties of nano-CeO2 were characterized in details. Second, the freshwater mussels were exposed to environmentally relevant concentrations of nano-CeO2 as 10 mg, 25 mg and 50 mg/L during 48-h and 7-d. Third, after the exposure periods, hemolymph and tissue samples were taken to analyse the Total Hemocyte Counts (THCs) histology and oxidative stress parameters (total antioxidant status, glutathione, glutathione-S-transferase, and advanced oxidative protein products).

RESULTS

Significant decrease of the THCs was observed in the nano-CeO2 exposed mussels compared to the control group (P < 0.05). The histological results showed a positive association between nano-CeO2 exposure concentration in the water and level of tissue damage and histopathological alterations were detected in the gill and the digestive gland tissues. Oxidative stress parameters were slightly affected after exposure to nano-CeO2 (P > 0.05). In conclusion, this study showed that acute exposure of freshwater mussels to nano-CeO2 did not pose significant biological risk. However, it has been proven that mussels are able to accumulate nano-CeO2 significantly in their bodies.

CONCLUSION

This suggests that nano-CeO2 may be a potential risk to other organisms in the ecosystem through trophic transfer in the food-web based on their habitat and niche in the ecosystem.

The Effect of Cerium Oxide (CeO2) on Ischemia-Reperfusion Injury in Skeletal Muscle in Mice with Streptozocin-Induced Diabetes

Objective: Lower extremity ischemia-reperfusion injury (IRI) may occur with trauma-related vascular injury and various vascular diseases, during the use of a tourniquet, in temporary clamping of the aorta in aortic surgery, or following acute or bilateral acute femoral artery occlusion. Mitochondrial dysfunction and increased basal oxidative stress in diabetes may cause an increase in the effects of increased reactive oxygen species (ROS) and mitochondrial dysfunction due to IRI. It is of great importance to examine therapeutic approaches that can minimize the effects of IRI, especially for patient groups under chronic oxidative stress such as DM. Cerium oxide (CeO2) nanoparticles mimic antioxidant enzymes and act as a catalyst that scavenges ROS. In this study, it was aimed to investigate whether CeO2 has protective effects on skeletal muscles in lower extremity IRI in mice with streptozocin-induced diabetes. Methods: A total of 38 Swiss albino mice were divided into six groups as follows: control group (group C, n = 6), diabetes group (group D, n = 8), diabetes-CeO2 (group DCO, n = 8), diabetes-ischemia/reperfusion (group DIR, n = 8), and diabetes-ischemia/reperfusion-CeO2 (group DIRCO, n = 8). The DCO and DIRCO groups were given doses of CeO2 of 0.5 mg/kg intraperitoneally 30 min before the IR procedure. A 120 min ischemia-120 min reperfusion period with 100% O2 was performed. At the end of the reperfusion period, muscle tissues were removed for histopathological and biochemical examinations. Results: Total antioxidant status (TAS) levels were found to be significantly lower in group DIR compared with group D (p = 0.047 and p = 0.022, respectively). In group DIRCO, total oxidant status (TOS) levels were found to be significantly higher than in group DIR (p < 0.001). The oxidative stress index (OSI) was found to be significantly lower in group DIR compared with group DCO (p < 0.001). Paraoxanase (PON) enzyme activity was found to be significantly increased in group DIR compared with group DCO (p < 0.001). The disorganization and degeneration score for muscle cells, inflammatory cell infiltration score, and total injury score in group DIRCO were found to be significantly lower than in group DIR (p = 0.002, p = 0.034, and p = 0.001, respectively). Conclusions: Our results confirm that CeO2, with its antioxidative properties, reduces skeletal muscle damage in lower extremity IRI in diabetic mice.

Bioproduction of cerium-bearing magnetite and application to improve carbon-black supported platinum catalysts

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)2O4), 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 L2,3 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.

Root-Applied Cerium Oxide Nanoparticles and Their Specific Effects on Plants: A Review

With the pronounced increase in nanotechnology, it is likely that biological systems will be exposed to excess nanoparticles (NPs). Cerium oxide nanoparticles (CeO2 NPs) are among the most abundantly produced nanomaterials in the world. Their widespread use raises fundamental questions related to the accumulation in the environment and further interactions with living organisms, especially plants. NPs present in either soil or soilless environments are absorbed by the plant root systems and further transported to the aboveground parts. After entering the cytoplasm, NPs interact with chloroplast, nucleus, and other structures responsible for metabolic processes at the cellular level. In recent years, several studies have shown the impact of nanoceria on plant growth and metabolic processes. Research performed on different plants has shown a dual role for CeO2 NPs. The observed effects can be positive or negative and strongly depend on the plant species, characterization, and concentrations of NPs. This review describes the impact of root-applied CeO2 NPs on plant growth, photosynthesis, metal homeostasis, and parameters of induced oxidative stress.

Elevated levels of environmental radioactivity in fluvial sediment: origin and health risk assessment

To study the geogenic processes of naturally occurring radioactive materials' (NORMs') distribution, a transboundary Himalayan river (Punarbhaba) is chosen due to its trivial anthropogenic impacts. In explaining the genesis of radionuclides, transition elements (Sc, Ti, V, and Fe), rare-earth-elements (REEs: La, Eu, Ce, Yb, Sm, and Lu), Ta, Hf, Th, and U were analysed in 30 riverbed sediments collected from the Bangladeshi portion of the river. Elemental abundances and NORMs' activity were measured by neutron activation analysis and HPGe-gamma-spectrometry, respectively. Averagen=30 radioactivity concentrations of 226Ra (68.4 Bq kg-1), 232Th (85.7 Bq kg-1), and 40K (918 Bq kg-1) were 2.0-2.3-fold higher, which show elevated results compared to the corresponding world mean values. Additionally, mean-REE abundances were 1.02-1.38-times higher than those of crustal origin. Elevated (relative to earth-crust) ratios of Th/U (=3.95 ± 1.84) and 232Th/40K and statistical demonstrations invoke Th-dominant heavy minerals, indicating the role of kaolinite clay mineral abundance/granitic presence. However, Th/Yb, La/V, Hf/Sc, and Th/Sc ratios reveal the presence of felsic abundances, hydrodynamic sorting, and recycling of sedimentary minerals. Geo-environmental indices demonstrated the enrichment of chemical elements in heavy minerals, whereas radiological indices presented ionizing radiation concerns, e.g., the average absorbed-gamma-dose rate (123.1 nGy h-1) was 2.24-fold higher compared to the threshold value which might cause chronic health impacts depending on the degree of exposure. The mean excess lifetime cancer risk value for carcinogen exposure was 5.29 × 10-4 S v-1, which is ∼2-times greater than the suggested threshold. Therefore, plausible extraction of heavy minerals and using residues as building materials can alleviate the two-reconciling problems: (1) radiological risk management and (2) fluvial navigability.

Ceria-Based Therapeutic Antioxidants for Biomedical Applications

The growing interest in nanomedicine over the last 20 years has carved out a research field called "nanocatalytic therapy," where catalytic reactions mediated by nanomaterials are employed to intervene in disease-critical biomolecular processes. Among many kinds of catalytic/enzyme-mimetic nanomaterials investigated thus far, ceria nanoparticles stand out from others owing to their unique scavenging properties against biologically noxious free radicals, including reactive oxygen species (ROS) and reactive nitrogen species (RNS), by exerting enzyme mimicry and nonenzymatic activities. Much effort has been made to utilize ceria nanoparticles as self-regenerating antioxidative and anti-inflammatory agents for various kinds of diseases, given the detrimental effects of ROS and RNS therein that need alleviation. In this context, this review is intended to provide an overview as to what makes ceria nanoparticles merit attention in disease therapy. The introductory part describes the characteristics of ceria nanoparticles as an oxygen-deficient metal oxide. The pathophysiological roles of ROS and RNS are then presented, as well as their scavenging mechanisms by ceria nanoparticles. Representative examples of recent ceria-nanoparticle-based therapeutics are summarized by categorization into organ and disease types, followed by the discussion on the remaining challenges and future research directions.

Recovery of Cerium Salts from Sewage Sludge Resulting from the Coagulation of Brewery Wastewater with Recycled Cerium Coagulant

Due to the high cost and limited sources of cerium coagulants, it is extremely important to take measures to recycle this raw material. This paper presents the new possibility of recovering cerium(III) chloride, cerium(III) sulphate, cerium(IV) sulphate, and potentially phosphate from sewage sludge (101.5 g/kg Ce and 22.2 g/kg total P) through a brewery wastewater treatment process using recycled CeCl3 as a coagulant. In order to recover the Ce and P, the sludge was subjected to extraction using an HCl solution. Optimal process conditions were determined by means of central composite design and response surface methodology (CCD/RSM) for three input parameters (HCl mass, reaction time, and extractant volume). Under optimal conditions (0.35 g HCl per 1 g of sludge, 40 min reaction time, extractant volume of 25 mL per 1 g of sludge), the highest efficiency obtained was 99.6% and 97.5% for Ce and P, respectively. Cerium(III) oxalate as Ce2(C2O4)3∙10H2O was precipitated from the obtained solution using H2C2O4 (99.97%) and decomposed into CeO2 (at 350 °C), which was afterwards subjected to a reaction with HCl (30%, m/m) and H2O2 (30%, m/m), which led to the crystallisation of CeCl3∙7H2O with a purity of 98.6% and a yield of 97.0%. The obtained CeO2 was also subjected to a reaction with H2SO4 (96%, m/m) and H2O2 (30%, m/m), which produced Ce2(SO4)3 with a yield of 97.4%. The CeO2 was also subjected to a reaction with only H2SO4 (96%, m/m), which produced Ce(SO4)2 with a yield of 98.3%. The filtrate obtained after filtering the Ce2(C2O4)3∙10H2O contained 570 mg/L of P, which enabled its use as a source of phosphorus compounds. The presented processes of Ce and potentially P recovery from sewage sludge originating from brewery wastewater contribute to the idea of a circular economy.

Influence of Nano-CeO2 and Graphene Nanoplatelets on the Conductivity and Dielectric Properties of Poly(vinylidene fluoride) Nanocomposite Films

Novel three-phase polymer nanocomposites (PNCs) based on cerium oxide (CeO2) nanoparticles (NPs) and graphene nanoplatelets (GNPs) incorporated in a poly(vinylidene fluoride) (PVDF) matrix were formulated using a solution-casting approach. To understand the structural and morphological features of PVDF/CeO2/GNP nanocomposites (NCs), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) analyses were accomplished. The PVDF/CeO2/GNP NCs displayed improved thermal stability which resulted from strong bonding between GNPs and CeO2 NPs and restriction of the polymer chain movement. The introduction of CeO2 NPs and GNPs within the PVDF matrix and good synergy between CeO2 NPs and GNPs led to variable mechanical properties of the prepared NCs. The PVDF/CeO2/GNP NCs portrayed reduced thermal stability, which could be due to the increased mobility of PVDF chains imposed by GNPs leading to the formation of volatile degradation products. Moreover, PVDF/CeO2/GNP NCs exhibited good electrical conductivity and high dielectric permittivity. The obtained dielectric permittivity value for the PVDF/CeO2/GNP NCs was 3-fold greater than PVDF/CeO2 NCs, making these novel tertiary composite materials a probable candidate for energy-storage applications.

Unraveling the multifaceted mechanisms and untapped potential of activated carbon in remediation of emerging pollutants: A comprehensive review and critical appraisal of advanced techniques

The rapid global expansion of industrialization has resulted in the discharge of a diverse range of hazardous contaminants into the ecosystem, leading to extensive environmental contamination and posing a pressing ecological concern. In this context, activated carbon (AC) has emerged as a highly promising adsorbent, offering significant advantages over conventional forms. For instance, AC has demonstrated remarkable adsorption capabilities, as evidenced by the successful removal of atrazine and ibuprofen using KOH and KOH-CO2-activated char, achieving impressive adsorption rates of 90% and 95%, respectively, at an initial dosage of 10 mg L-1. Moreover, AC can effectively adsorb aromatic compounds through π-π stacking interactions. The aromatic rings in organic molecules can align and interact with the carbon atoms in AC's structure, leading to effective adsorption. In this review, by employing a systematic analysis of recent research findings (majorly from 2015 to 2023), an in-depth exploration of AC's evolution and its wide-ranging applications in adsorbing and remediating emerging pollutants, including dyes, organic contaminants, and hazardous gases and mitigating the adverse impacts of such emerging pollutants on ecosystems have been discussed. It serves as a valuable resource for researchers, professionals, and policymakers involved in environmental remediation and pollution control, facilitating the development of sustainable and effective strategies for mitigating the global impact of emerging pollutants.

Single cell ICP-MS to evaluate the interaction behaviour for Cd, Ce and U with Streptomyces coelicolor spores

Streptomyces are important soil bacteria used for bioremediation of metal-contaminated soils, however, it is still unknown how metal-selective Streptomyces are and which mechanisms are involved during their capture. In this work, we exposed S. coelicolor spores to environmentally relevant concentrations (0.1, 1, 10, 100 μM) of Ce, U and Cd in solid medium for one week to investigate the uptake behaviour of hyphae in the newly formed spores. Additionally, metal adsorption onto the spores was explored by incubating inactive, ungerminated spores for one day in aqueous metal solution. The spore-washing treatment was key to distinguishing between strongly spore-associated (e.g. incorporation; Tris-EDTA buffer) and weakly spore-associated metals (Tris buffer alone minus Tris-EDTA). Single cell (sc) ICP-MS was used to quantify metal-associated content in individual spores. Our results revealed element-specific adsorption onto inactive spores showing that out of the total metal exposure, both strongly (Ce: 58%; U: 54%; Cd: 28%) and weakly (Ce: 12%; U: 1%; Cd: 18%) adsorbed metals occur. However, scICP-MS showed that from metal-amended solid medium, only Ce and U were strongly spore-associated (averages 0.040 and 0.062 fg spore-1 for 10 μM exposures, respectively) while Cd was below the limit of detection (< 0.006 fg spore-1). We propose that hyphae only metabolically interact with Ce in a controlled manner but uncontrolled with U, as 66-73% Ce and only 2-4% U were inherited from adsorbed content. We conclude that Streptomyces spore-metal interaction starts with a relevant adsorption step of Ce, U and Cd as presented for aqueous conditions. If spores start to germinate, hyphae are capable of effectively encapsulating Ce and U, but not Cd. This study brings light into the still unknown field of metal interactions with Streptomyces and applied understanding for more efficient and metal-specific use of Streptomyces in bioremediation of metal-polluted soils.

The ameliorative effect of cerium oxide nanoparticles on chlorpyrifos induced hepatotoxicity in a rat model: Biochemical, molecular and immunohistochemical study

BACKGROUND

Chlorpyrifos (CPF) is a widely used insecticide that causes toxicity to living organisms through the production of free radicals. Cerium oxide nanoparticles (CeO2NPs) are a new antioxidant agent that has proved therapeutic effects. We evaluated the effect of CeO2NPs on CPF hepatotoxicity.

METHODS

Forty rats were randomized into four groups. Group I: rats received 1 ml corn oil by gastric tube once daily and 0.5 ml PBS by intra-peritoneal injection twice a week for 4 weeks. Group II: received CeO2NPs 0.5 mg/kg in PBS by i.p. injection, twice weekly for four weeks. Group III: were treated with oral administration of CPF 13.5 mg/kg in corn oil daily for 4 weeks. Group IV: received CPF as in group III, then each animal received CeO2NPs twice weekly for four weeks as in group II. Twenty-four hours after the last dose, rats were anesthetized and sera were collected for liver enzymes assessment. Afterwards, rats were sacrificed, livers were excised, the right lobe of each liver was fixed for immunohistochemical studies, and the left lobe was homogenized for oxidative profile assessment and molecular analysis.

RESULTS

CPF group showed significant increase in liver transaminases, disturbance of the oxidative profile with up-regulation of BAX expression and down-regulation in the Bcl-2, Gadd45 and NFE2L2. CPF caused severe histopathological liver damage as well as significant increase in anti-Caspase 3 and TNF immunostaining. The CeO2NPs treated group revealed significant improvement of all previous parameters.

CONCLUSION

CeO2NPs could alleviate CPF hepatoxicity through decreasing expression of the inflammatory and apoptotic proteins and increasing the activity of antioxidant enzymes.

Occurrence of rare earth elements in water, sediment, and freshwater fish of diverse trophic levels and feeding ecology: Insights from the Po river (northwest Italy)

To date, the occurrence of rare earth elements (REEs) in freshwater ecosystems has garnered limited attention in the scientific literature. Furthermore, a dearth of data exists regarding their potential bioaccumulation in freshwater fish. To fill this knowledge gap, we studied REEs concentrations in water, sediment, and fish specimens collected along the Po River (northwest Italy) and calculated biota-sediment accumulation (BSAF) and bioconcentration (BCF) factors, while taking into account fish feeding behavior and trophic level effects on the overall content of total REEs (ƩREEs). The fish communities were composed of native and non-native species. Remarkably low concentrations of REEs (<0.0003 mg/L) were detected in the water samples, indicating REEs insolubility. In contrast, sediment samples were found to be a good sink for REEs, with a higher mean ƩREEs recorded for the samples from the Moncalieri station (70.93 mg/kg). Notably, no significant differences in ƩREEs concentration were observed in the muscle tissue of fish samples from the three stations. The highest mean ƩREEs was recorded in the samples from the Murazzi station (0.027 mg/kg). The BSAF was very low, consistently below the unit, indicating an absence of bioaccumulation in fish muscle from sediment. In contrast, the BCF was high for several REEs, mainly for Sc and Y. While feeding ecology did not appear to affect REEs accumulation in muscle, there was a significant negative relationship between the trophic level and ΣREEs, indicating a trophic dilution of REEs from predator (Silurus glanis) to planktivorous (Alburnus arborella) fish. This study provides baseline concentrations, trophic transfers, and patterns of REEs in a river system. Further studies are needed to understand the transfer of REEs to other biotic components of lotic ecosystems.

In vitro analyses of cerium oxide nanoparticles in degrading anthracene/fluorene and revealing the antibiofilm activity against bacteria and fungi

A sol-gel method was used to synthesize the cerium dioxide nanoparticles. The nanoparticles formed were then characterized with UV-visible spectrophotometry, Fourier Transform Infrared Spectrophotometer (FTIR), SEM-EDAX, XRD, and Dynamic Light Scattering (DLS). The UV-visible absorbance at 282 nm and characteristic peak at 600-4000 cm-1 provided insight into the formation of cerium dioxide nanoparticles using a chemical method. SEM analysis and EDAX analysis confirmed nanoparticle formation and elements within the nanoparticles based on their irregular morphology. The hydrodynamic size obtained from the DLS analysis was 178.4 nm and the polydispersity was 0.275 nm. Furthermore, XRD results confirmed the crystalline nature of cerium dioxide nanoparticles. Using batch adsorption as a method, the effect of concentration of Polycyclic Aromatic Hydrocarbons (PAH), adsorbent concentration, pH, and irradiation source was investigated. Under UV light conditions, 10 μg/mL cerium dioxide nanoparticle at pH 5 degraded 2 μg/mL of PAH (anthracene and fluorene). Consequently, the synthesized cerium dioxide nanoparticles were effective photocatalysts. For anthracene and fluorene, kinetic studies showed the degradation process followed pseudo-second-order kinetics and Freundlich isotherms. Cerium oxide also exhibited significant antimicrobial and antibiofilm activity against bacteria and fungi. As a result, the cerium dioxide nanoparticle has proved to be a highly effective photocatalytic tool for the degradation of PAHs and exhibits strong antimicrobial activity.

Radiation exposure and health concerns associated with the environmental geochemistry of relatively higher radioactivity in a fresh water basin

This study was carried out on a negligible anthropogenically impacted Indo-Bangla transboundary river basin (Atrai, Bangladesh) to elicit radionuclides' and elemental distributions. Thirty sediment samples were collected from the Bangladesh portion of the river, and instrumental neutron activation analysis and HPGe γ-Spectrometry techniques were used to determine environmental radionuclides (e.g., 232Th, 226Ra, 40K) and associated elemental concentrations, respectively. Metal concentrations (Sc, V, Fe, Eu, Sm, La, Yb, Ce, Lu, Ta, Hf) were determined to comprehend the genesis of greater radioactivity. Recognizing the mean concentration of absorbed gamma dose rate (158.7 hGyh-1) is 2.88-times more than the recommended value (55 hGyh-1) that describes ionizing radiation concerns regarding potential health risks to the surrounding communities and the houses of native residents, which are constructed by Atrai river sediment. This work will assist relevant policymakers in exploring valuable heavy minerals and provide information regarding radiological health risks from a fluvial system.

Infrared spectroscopy analysis determining secondary structure change in albumin by cerium oxide nanoparticles

Cerium oxide (CeO2) nanoparticles are expected to have applications in the biomedical field because of their antioxidative properties. Inorganic nanoparticles interact with proteins at the nanoparticle surface and change their conformation when administered; however, the principle underlying this interaction is still unclear. This study aimed to investigate the secondary structural changes occurring in bovine serum albumin (BSA) mixed with CeO2 nanoparticles having different surface modifications using Fourier transform infrared spectroscopy. CeO2 nanoparticles (diameter: 240 nm) were synthesized from an aqueous cerium (III) nitrate solution using a homogeneous precipitation method. The surfaces of the nanoparticles were modified by the catechol compounds dopamine and 3,4-dihydroxyhydrocinnamic acid (DHCA). In the presence of these CeO2 nanoparticles (0.11-0.43 mg/mL), β-sheet formation of BSA (30 mg/mL) was promoted especially on the amine-modified (positively charged) nanoparticles. The local concentration of BSA on the surface of the positively charged nanoparticles may have resulted in structural changes due to electrostatic and other interactions with BSA. Further investigations of the interaction mechanism between nanoparticles and proteins are expected to lead to the safe biomedical applications of inorganic nanoparticles.

Molecular Imaging Investigations of Polymer-Coated Cerium Oxide Nanoparticles as a Radioprotective Therapeutic Candidate

Cerium oxide nanoparticles (CONPs) have a unique surface redox chemistry that appears to selectively protect normal tissues from radiation induced damage. Our prior research exploring the biocompatibility of polymer-coated CONPs found further study of poly-acrylic acid (PAA)-coated CONPs was warranted due to improved systemic biodistribution and rapid renal clearance. This work further explores PAA-CONPs' radioprotective efficacy and mechanism of action related to tumor microenvironment pH. An ex vivo TUNEL assay was used to measure PAA-CONPs' protection of the irradiated mouse colon in comparison to the established radioprotector amifostine. [18F]FDG PET imaging of spontaneous colon tumors was utilized to determine the effects of PAA-CONPs on tumor radiation response. In vivo MRI and an ex vivo clonogenic assay were used to determine pH effects on PAA-CONPs' radioprotection in irradiated tumor-bearing mice. PAA-CONPs showed excellent radioprotective efficacy in the normal colon that was equivalent to uncoated CONPs and amifostine. [18F]FDG PET imaging showed PAA-CONPs do not affect tumor response to radiation. Normalization of tumor pH allowed some radioprotection of tumors by PAA-CONPs, which may explain their lack of tumor radioprotection in the acidic tumor microenvironment. Overall, PAA-CONPs meet the criteria for clinical application as a radioprotective therapeutic agent and are an excellent candidate for further study.

Nanoparticle Synthesis and Their Integration into Polymer-Based Fibers for Biomedical Applications

The potential of nanoparticles as effective drug delivery systems combined with the versatility of fibers has led to the development of new and improved strategies to help in the diagnosis and treatment of diseases. Nanoparticles have extraordinary characteristics that are helpful in several applications, including wound dressings, microbial balance approaches, tissue regeneration, and cancer treatment. Owing to their large surface area, tailor-ability, and persistent diameter, fibers are also used for wound dressings, tissue engineering, controlled drug delivery, and protective clothing. The combination of nanoparticles with fibers has the power to generate delivery systems that have enhanced performance over the individual architectures. This review aims at illustrating the main possibilities and trends of fibers functionalized with nanoparticles, focusing on inorganic and organic nanoparticles and polymer-based fibers. Emphasis on the recent progress in the fabrication procedures of several types of nanoparticles and in the description of the most used polymers to produce fibers has been undertaken, along with the bioactivity of such alliances in several biomedical applications. To finish, future perspectives of nanoparticles incorporated within polymer-based fibers for clinical use are presented and discussed, thus showcasing relevant paths to follow for enhanced success in the field.

Rare earth element bioaccumulation and cerium anomalies in biota from the Eastern Canadian subarctic (Nunavik)

Recent increases in the demand for rare earth elements (REE) have contributed to various countries' interest in exploration of their REE deposits, including within Canada. Current limited knowledge of REE distribution in undisturbed subarctic environments and their bioaccumulation within northern species is addressed through a collaborative community-based environmental monitoring program in Nunavik (Quebec, Canada). This study provides background REE values (lanthanides + yttrium) and investigates REE anomalies (i.e., deviations from standard pattern) across terrestrial, freshwater, and marine ecosystems in an area where a REE mining project is in development. Results are characteristic of a biodilution of REE, with the highest mean total REE concentrations (ΣREE) reported in sediments (10² nmol/g) and low trophic level organisms (i.e., biofilm, macroalgae, macroinvertebrates, common mussels, and reindeer lichens; 10¹-10² nmol/g), and the lowest mean concentrations in higher-level consumers (i.e., goose, ptarmigan, char, whitefish, cod, sculpin and seal; 10^-2 - 10¹ nmol/g). The animal tissues are of importance to northern villages and analyses demonstrate a species-specific bioaccumulation of REE, with mean concentrations up to 40 times greater in liver compared to muscle, with bones and kidneys presenting intermediate concentrations and the lowest in blubber. Further, a tissue-specific fractionation was presented, with significant light REE (LREE) enrichment compared to heavy REE (HREE) in consumer livers (LREE/HREE ≅ 10¹) and the most pronounced negative cerium (Ce) anomalies (<0.80) in liver and bones of fish species. These fractionation patterns, along with novel negative relationships presented between fish size (length, mass) and Ce anomalies suggest metabolic, ecological, and/or environmental influences on REE bioaccumulation and distribution within biota. Background concentration data will be useful in the establishment of REE guidelines; and the trends discussed support the use of Ce anomalies as biomarkers for REE processing in animal species, which requires further investigation to better understand their controlling factors.

Surface-modified cerium dioxide nanoparticles with improved anti-amyloid and preserved nanozymatic activity

Cerium dioxide nanoparticles (CeO₂ NPs) are used increasingly in nanotechnology and particularly in biotechnology and bioresearch. Thus, CeO₂ NPs have been successfully tested in vitro as a potential therapeutic agent for various pathologies associated with oxidative stress, including the formation of protein amyloid aggregates. In this study, to increase the anti-amyloidogenic efficiency and preserve the antioxidant potential, the surface of the synthesized CeO₂ NPs is modified with a nonionic, sugar-based surfactant, dodecyl maltoside (DDM), which is known for its high anti-amyloidogenic activity and biocompatibility. Dynamic light scattering and Fourier transform infrared spectroscopy demonstrated successful modification by DDM. The apparent hydrodynamic diameters of CeO₂ NPs and DDM-modified NPs (CeO₂@DDM NPs) are found to be ⁓180 nm and ⁓260 nm, respectively. A positive zeta potential value of + 30.5 mV for CeO₂ NPs and + 22.5 mV for CeO₂ @DDM NPs suggest sufficient stability and good dispersion of NPs in an aqueous solution. A combination of Thioflavin T fluorescence analysis and atomic force microscopy is used to assess the effect of nanoparticles on the formation of insulin amyloid fibrils. Results show that the fibrillization of insulin is inhibited by both, naked and modified NPs in a dose-dependent manner. However, while the IC₅₀ of naked NPs is found to be ∼270 ± 13 µg/mL, the surface-modified NPs are 50% more efficient with IC₅₀ equaled to 135 ± 7 µg/mL. In addition, both, the naked CeO₂ NPs and DDM-modified NPs displayed an antioxidant activity expressed as oxidase-, catalase- and SOD-like activity. Therefore, the resulting nanosized material is very well suited to prove or disprove the hypothesis that oxidative stress plays a role in the formation of amyloid fibrils.

Cerium oxide nanoparticles (nCeO2) exert minimal adverse effects on microbial communities in soils with and without biosolids amendment

Increased use of nano-cerium oxide (nCeO₂) in an array of industrial applications has raised environmental concerns due to potential increased loadings to the soil environment. This research investigated the potential adverse effects of nCeO₂ (10-30 nm) on the soil microbial community in two exposure scenarios: direct application to soil, and indirect application to soil through chemical spiking of biosolids, followed by mixing into soil. Total Ce in test soils without, and with biosolids amendment, ranged from 44 to 770, and 73 to 664 mg Ce kg^-1 soil, respectively. In order to help distinguish whether observed effects were elicited by the solid-phase colloids or the activity of dissolved Ce, a soluble Ce salt (Ce (NO₃)₃) treatment was included in select assays. A suite of tests was used to investigate effects on critical processes: microbial growth (heterotrophic plate count), microbial activity (organic matter (OM) decomposition, enzyme activity and, nitrification) and diversity (structural and functional). Although results showed significant inhibition on microbial growth in soil without biosolids amendment at ≥ 156 mg Ce kg^-1 soil by week 5, these results were inconsistent and non-significant thereafter. In general, nCeO₂ showed no evidence of consistent adverse effects on OM decomposition, nitrification, soil enzyme activities and functional diversity. Leucine aminopeptidase showed significant (p< 0.05) stimulatory effects over time at ≥ 44 mg Ce kg^-1 in soils without biosolids, which was not observed in soils with biosolids amendment. The lack of inhibitory effects of nCeO₂ may be attributed to its low solubility; Ce in soil extracts (0.01 M CaCl₂) were all below detection (< 0.003 mg kg^-1) in the nCeO₂-spiked soils, but detectable in the Ce (NO₃)₃ samples. In contrast, soluble Ce at 359 mg Ce kg^-1 showed a significant reduction in OM decomposition and effects on microbial genomic diversity based on the 16S rDNA data in soils with and without biosolids amendment (359 and 690 mg Ce kg^-1). The nCeO₂ behaviour and effects information described herein are expected to help fulfill data gaps for the characterization of this priority nanomaterial.

Advancements in the dominion of fate and transport of pharmaceuticals and personal care products in the environment-a bibliometric study

The study on the fate and transport of Pharmaceuticals and Personal Care Products, PPCPs (FTP) in the environment, has received particular attention for over two decades. The PPCPs threaten ecology and human health even at low concentrations due to their synergistic effects and long-range transport. The research aims to provide an inclusive map of the scientific background of FTP research over the last 25 years, from 1996 to 2020, to identify the main characteristics, evolution, salient research themes, trends, and research hotspots in the field of interest. Bibliometric networks were synthesized and analyzed for 577 journal articles extracted from the Scopus database. Consequently, seven major themes of FTP research were identified as follows: (i) PPCPs category; (ii) hazardous effects; (iii) occurrence of PPCPs; (iv) PPCPs in organisms; (v) remediation; (vi) FTP-governing processes; and (vii) assessment in the environment. The themes gave an in-depth picture of the sources of PPCPs and their transport and fate processes in the environment, which originated from sewage treatment plants and transported further to sediment/soils/groundwater/oceans that act as the PPCPs' major sink. The article provided a rigorous analysis of the research landscape in the FTP study conducted during the specified years. The prominent research themes, content analysis, and research hotspots identified in the study may serve as the basis of real-time guidance to lead future research areas and a prior review for policymakers and practitioners.

Oxidation and Nanoparticle Formation during Ce(III) Sorption onto Minerals

The sorption of Ce(III) on three abundant environmental minerals (goethite, anatase, and birnessite) was investigated. Batch sorption experiments using a radioactive ¹³⁹Ce tracer were performed to investigate the key features of the sorption process. Differences in sorption kinetics and changes in oxidation states were found in the case of the sorption of Ce(III) on birnessite compared to that on other minerals. Speciation of cerium onto all of the studied minerals was investigated using spectral and microscopic methods: high-resolution transmission electron microscopy (HRTEM), electron energy loss spectroscopy (EELS), and X-ray absorption spectroscopy (XAS) in conjunction with theoretical calculations. It was found that during the sorption process onto birnessite, Ce(III) was oxidized to Ce(IV), while the Ce(III) on goethite and anatase surfaces remained unchanged. Oxidation of Ce(III) by sorption on birnessite was also accompanied by the formation of CeO₂ nanoparticles on the mineral surface, which depended on the initial cerium concentration and pH value.

Divergent effects of cerium oxide nanoparticles alone and in combination with cadmium on nutrient acquisition and the growth of maize (Zea mays)

INTRODUCTION

The increasing use of cerium nanoparticles (CeO₂-NPs) has made their influx in agroecosystems imminent through air and soil deposition or untreated wastewater irrigation. Another major pollutant associated with anthropogenic activities is Cd, which has adverse effects on plants, animals, and humans. The major source of the influx of Cd and Ce metals in the human food chain is contaminated food, making it an alarming issue; thus, there is a need to understand the factors that can reduce the potential damage of these heavy metals.

METHODS

The present investigation was conducted to evaluate the effect of CeO₂-10-nm-NPs and Cd (alone and in combination) on Zea mays growth. A pot experiment (in sand) was conducted to check the effect of 0, 200, 400, 600, 1,000, and 2,000 mg of CeO₂-10 nm-NPs/kg^-1 dry sand alone and in combination with 0 and 0.5 mg Cd/kg^-1 dry sand on maize seedlings grown in a partially controlled greenhouse environment, making a total of 12 treatments applied in four replicates under a factorial design. Maize seedling biomass, shoot and root growth, nutrient content, and root anatomy were measured.

RESULTS AND DISCUSSION

The NPs were toxic to plant biomass (shoot and root dry weight), and growth at 2,000 ppm was the most toxic in Cd-0 sets. For Cd-0.5 sets, NPs applied at 1,000 ppm somewhat reverted Cd toxicity compared with the contaminated control (CC). Additionally, CeO₂-NPs affected Cd translocation, and variable Ce uptake was observed in the presence of Cd compared with non-Cd applied sets. Furthermore, CeO₂-NPs partially controlled the elemental content of roots and shoots (micronutrients such as B, Mn, Ni, Cu, Zn, Mo, and Fe and the elements Co and Si) and affected root anatomy.

Benzo(a)pyrene and Cerium Dioxide Nanoparticles in Co-Exposure Impair Human Trophoblast Cell Stress Signaling

Human placenta is a multifunctional interface between maternal and fetal blood. Studying the impact of pollutants on this organ is crucial because many xenobiotics in maternal blood can accumulate in placental cells or pass into the fetal circulation. Benzo(a)pyrene (BaP) and cerium dioxide nanoparticles (CeO2 NP), which share the same emission sources, are found in ambient air pollution and also in maternal blood. The aim of the study was to depict the main signaling pathways modulated after exposure to BaP or CeO2 NP vs. co-exposure on both chorionic villi explants and villous cytotrophoblasts isolated from human term placenta. At nontoxic doses of pollutants, BaP is bioactivated by AhR xenobiotic metabolizing enzymes, leading to DNA damage with an increase in γ-H2AX, the stabilization of stress transcription factor p53, and the induction of its target p21. These effects are reproduced in co-exposure with CeO2 NP, except for the increase in γ-H2AX, which suggests a modulation of the genotoxic effect of BaP by CeO2 NP. Moreover, CeO2 NP in individual and co-exposure lead to a decrease in Prx-SO3, suggesting an antioxidant effect. This study is the first to identify the signaling pathways modulated after co-exposure to these two pollutants, which are common in the environment.

Monoclonal Antibody-Guided Tumor-Targeted Hollow Virus-Like Cerium Oxide with Oxygen Self-Supply for Intensifying Photodynamic Therapy

The hypoxic character of tumors and the poor targeting ability of photosensitizers often limit the efficacy of photodynamic therapy (PDT). In recent years, the discovery of metal nanoenzymes and nanocarriers has improved PDT. Thereby, to improve the effective utilization of photosensitizers and oxygen (O₂ ) in tumors, herein, a nanosystem (LS-HB@HvCeO₂ -NRP1 mAb, LHCN1) is reported, in which a hollow virus-like cerium oxide (HvCeO₂ ) is surface-decorated with tumor-targeting neuropilin-1 monoclonal antibody (NRP1 mAb), and loaded with a photosensitizer (chlorin e6-C-15-ethyl ester, LS-HB). In vitro and in vivo experiments demonstrate that LHCN1 can efficiently accumulate within the tumor sites via the targeting guidance of NRP1 mAb and is then rapidly endocytosed into cells. Furthermore, HvCeO₂ with catalase-mimetic activity can decompose the endogenous hydrogen peroxide (H₂ O₂ ) to promote O₂ via the valence transformation between Ce⁴⁺ and Ce³⁺ , relieving tumor hypoxia and improving the PDT efficacy. Upon near-infrared laser irradiation, LS-HB produces large amounts of cytotoxic reactive oxygen species. Moreover, LHCN1 is used in fluorescence/photoacoustic multimodal imaging for in vivo drug localization, and its use in PDT evidently helps inhibit tumor growth with no apparent toxicity to normal tissues. Thus, LHCN1 may provide a promising strategy for precise tumor-specific diagnosis and treatment.

The role of nanocerianite (CeO2) in the stability of Ce carbonates at low-hydrothermal conditions

The formation of cerianite (CeO₂) was investigated at low hydrothermal conditions (35-205 °C) via two experimental settings: (1) crystallisation from solution experiments, and (2) replacement of Ca-Mg carbonates (calcite, dolomite, aragonite) mediated by Ce-bearing aqueous solutions. The solid samples were studied with a combination of powder X-ray diffraction, scanning electron microscopy, and Fourier-transform infrared spectroscopy. The results revealed a multi-step crystallisation pathway: amorphous Ce carbonate → Ce-lanthanite [Ce₂(CO₃)₃·8H₂O] → Ce-kozoite [orthorhombic CeCO₃(OH)] → Ce-hydroxylbastnasite [hexagonal CeCO₃(OH)] → cerianite [CeO₂]. We found that Ce carbonates can decarbonise in the final stage of the reaction, forming cerianite which significantly increases the porosity of the solids. The redox behaviour of Ce combined with the temperature, and the availability of CO₂ ^3- govern this crystallisation sequence, the sizes, morphologies, and crystallisation mechanisms of the solid phases. Our results explain the occurrence and behaviour of cerianite in natural deposits. These findings also present a simple, environmental-friendly, and cost-efficient method for the synthesis of Ce carbonates and cerianite with tailored structures and chemistries.

Solution-Route Inkjet Fabrication of CeO2 Thin Films with Tunable Microstructure

We report the fabrication and characterization of solution-route CeO₂ thin films with a tunable porosity and microstructure. Films were deposited by means of inkjet printing technique using 0.2 M, 0.4 M and 0.6 M concentration inks prepared from Ce(NO₃)₃·6H₂O precursor. Printing was performed at two different temperatures of 60 °C and 300 °C to study the variation in structure. Printing parameters were adjusted for the consecutive deposition of layers, resulting in ≈140 nm and ≈185 nm thick single layers for 60 °C and 300 °C printing temperatures, respectively. We compared the microstructure of printed films for different concentrations, printing temperatures, solvents and substrates. The formation of the cubic fluorite structure of the printed films was confirmed via XRD characterization. We suggest this technique as an advanced method for high-quality film fabrication with a controlled microstructure and with a minimal waste of materials. Through adjusting printing parameters, both dense and porous films can be produced for use in different applications.

Synthesis and Spectral Characterisation of Fabricated Cerium-Doped Magnesium Oxide Nanoparticles: Evaluation of the Antimicrobial Potential and Its Membranolytic Activity through Large Unilamellar Vesicles

Considerable attention has been given to Magnesium oxide nanoparticles lately due to their antimicrobial potential, low toxicity to humans, high thermal stability, biocompatibility, and low cost of production. However, their successful transformation into sustainable drugs is limited due to their low membrane permeability, which reduces their bioavailability in target cells. Herein we propose Cerium-doped magnesium oxide nanoparticles (MgOCeNPs) as a powerful solution to above mentioned limitations and are compared with MgO NPs for their membrane permeability and antimicrobial activity. Both pure and Ce-doped were characterized by various spectroscopic and microscopic techniques, in which an X-ray diffraction (XRD) examination reveals the lattice patterns for doped nanoparticles. Furthermore, Atomic Force Microscopy (AFM) revealed the three-dimensional (3D) structure and height of the nanoparticle. The crystal structure (FCC) of MgO did not change with Ce doping. However, microstructural properties like lattice parameter, crystallite size and biological activity of MgO significantly changed with Ce doping. In order to evaluate the antimicrobial potential of MgOCeNPs in comparison to MgO NPs and to understand the underlying mechanisms, the antibacterial activity was investigated against human pathogenic bacteria E. coli and P. aeruginosa, and antifungal activity against THY-1, a fungal strain. MgOCeNPs were studied by several methods, which resulted in a strong antibacterial and antifungal activity in the form of an elevated zone of inhibition, reduced growth curve, lower minimum inhibitory concentration (MIC₈₀) and enhanced cytotoxicity in both bacterial and fungal strain as compared to MgO nanoparticles. The study of the growth curve showed early and prolonged stationary phase and early decline log phase. Both bacterial and fungal strains showed dose-dependent cytotoxicity with enhancement in intracellular reactive oxygen species (ROS) generation and formation of pores in the membrane when interacting with egg-phosphatidylcholine model Large Unilamellar Vesicles (LUVs). The proposed mechanism of MgOCeNPs toxicity evidently is membranolytic activity and induction of ROS production, which may cause oxidative stress-mediated cytotoxicity. These results confirmed that MgOCeNPs are a novel and very potent antimicrobial agent with a great promise of controlling and treating other microbes.

CeO2@NH2 functionalized electrodes for the rapid detection of SARS-CoV-2 spike receptor binding domain

A detection method based on an electrochemical aptasensor has been developed as an alternative fast, portable, simple, inexpensive, and high-accuracy detection method for detecting the SARS-CoV-2 Spike Receptor Binding Domain (spike RBD). The CeO₂@NH₂ functionalized Screen Printed Carbon Electrode (SPCE) was used to immobilize an aminated aptamer of spike RBD protein via glutaraldehyde as a linker. The aptamer's interaction with the SARS-CoV-2 Spike RBD was measured via the [Fe(CN)₆]^4-/3- redox system signal. Experimental conditions were optimized using a Box-Behnken experimental design and showed that the optimal conditions of the SARS-CoV-2 aptasensor were 1.5 ng mL^-1 of aptamer, immobilization of aptamer for 60 minutes, and Spike RBD incubation for 10 minutes. The developed aptasensor was able to detect the standard SARS-CoV-2 Spike RBD with a detection limit of 0.017 ng mL^-1 in the range of 0.001-100 ng mL^-1. This aptasensor was used to detect salivary and oropharyngeal swab samples of normal individuals with the addition of Spike RBD, and the recoveries were 92.96% and 96.52%, respectively. The testing on nasopharyngeal swab samples of COVID-19 patients showed that the aptasensor results were comparable with the qRT-PCR results. Thus, the developed aptasensor has the potential to be applied as a SARS-CoV-2 rapid test method for clinical samples.

Lanthanides-Substituted Hydroxyapatite for Biomedical Applications

Lately, there has been an increasing demand for materials that could improve tissue regenerative therapies and provide antimicrobial effects. Similarly, there is a growing need to develop or modify biomaterials for the diagnosis and treatment of different pathologies. In this scenario, hydroxyapatite (HAp) appears as a bioceramic with extended functionalities. Nevertheless, there are certain disadvantages related to the mechanical properties and lack of antimicrobial capacity. To circumvent them, the doping of HAp with a variety of cationic ions is emerging as a good alterative due to the different biological roles of each ion. Among many elements, lanthanides are understudied despite their great potential in the biomedical field. For this reason, the present review focuses on the biological benefits of lanthanides and how their incorporation into HAp can alter its morphology and physical properties. A comprehensive section of the applications of lanthanides-substituted HAp nanoparticles (HAp NPs) is presented to unveil the potential biomedical uses of these systems. Finally, the need to study the tolerable and non-toxic percentages of substitution with these elements is highlighted.

Biosorption kinetics of cerium(III) and cobalt(II) from liquid wastes using individual bacterial species isolated from low-level liquid radioactive wastes

The existence of toxic heavy metals in the aquatic environment has emphasized a considerable exigency to develop several multifunctional biosorbents for their removal. Herein, three individual bacterial species of Cellulosimicrobium cellulans, Bacillus coagulans, and Microbacterium testaceum were successfully isolated from low-level liquid radioactive wastes. Their loading capacities towards cerium and cobalt metal ions were inclusivity inspected under variable operational parameters of pH, primary pollutant concentration, interaction time, temperature, stirring speed, and biosorbent dosage. By analyzing the influence of solution pH, concentration, temperature, biosorbent mass, and agitation speed on the biosorption kinetics, the biosorption process confirms pseudo-second-order kinetic, intraparticle diffusion, and Elovich equation. Remarkably, the isolated Microbacterium testaceum exhibited high loading capacities reaching 68.1 mg g^-1, and 49.6 mg g^-1 towards Ce(III), and Co(II) ions, respectively, at the initial concentration of 2.8 mM, pH 4.5, and 25 °C. Overall, the isolated bacterial species can potentially be offered up as a promising scavenger for Ce(III) and Co(II) from liquid waste effluents.

Comparative synthesis and characterization of nanocomposites using chemical and green approaches including a comparison study on in vivo and in vitro biological properties

In this study, the anti-diabetic, anti-inflammatory, anti-cytotoxic, and antibacterial effects of various substances were studied in vitro. Malachite green's photocatalytic effects were used to determine the optimised sample while it was exposed to visible light. The intended nanocomposites were created without any contaminants, according to XRD data. The overall characterisation results of the green synthesis of CS/SiO₂/TiO₂/CeO₂/Fe₃O₄ nanocomposites (CSTCF(G)) were superior to those of the chemical synthesis of CS/SiO₂/TiO₂/CeO₂/Fe₃O₄ nanocomposites (CSTCF(C)). At the five doses examined, the green synthesis of CS/SiO₂/TiO₂/CeO₂/Fe₃O₄ nanocomposites (CSTCF(G)) and chemical synthesis of CS/SiO₂/TiO₂/CeO₂/Fe₃O₄ nanocomposites (CSTCF(C)) resulted in higher α-glucosidase inhibition percentages in the antidiabetic assay. HaCaT cells and MCF-7 cells were less harmful when treated with chemically synthesized CS/SiO₂/TiO₂/CeO₂/Fe₃O₄ nanocomposites (CSTCF(C)), and green synthesized CS/SiO₂/TiO₂/CeO₂/Fe₃O₄ nanocomposites (CSTCF(G)). From the results of the cytotoxicity tests against MCF-7 cells and HaCaT cells using the nanocomposites, the IC₅₀ values of Salacia reticulata, green synthesized CS/SiO₂/TiO₂/CeO₂/Fe₃O₄ nanocomposites (CSTCF(G)), and chemically synthesized CS/SiO₂/TiO₂/CeO₂/Fe₃O₄ nanocomposites (CSTCF(C)) were calculated. This research work shows that the green synthesized CS/SiO₂/TiO₂/CeO₂/Fe₃O₄ nanocomposites (CSTCF(G)) have strong anti-inflammatory, antibacterial and anti-diabetic properties, as well as considerable suppression of high activation in in vivo zebrafish embryo toxicity. The novelty of this study focused on the revelation that green synthesized nanocomposites are more affordable, environmentally friendly and biocompatible than chemically synthesized ones.

Toxicity of ceria nanoparticles to the regeneration of freshwater planarian Dugesia japonica: The role of biotransformation

Cerium oxide nanoparticles (n-CeO₂) have wide applications ranging from industrial to consumer products, which would inevitably lead to their release into the environment. Despite the toxicity of n-CeO₂ on aquatic organisms has been largely reported, research on developing organisms is still lacking. In this study, we investigate the toxic effects of n-CeO₂ on the stem cells, tissue- and neuro-regeneration, using freshwater planarian Dugesia japonica as a model. Effects of bulk sized (μ-) CeO₂ and ionic Ce (Ce³⁺) were compared with that of n-CeO₂ to explore the origin of the toxic effects of n-CeO₂. No overt toxicity was observed in μ-CeO₂ treatment. n-CeO₂ 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-CeO₂ than the normal ones. Ce³⁺ exhibited significantly higher toxicity than n-CeO₂, even though the total Ce uptake is 0.2 % less in Ce³⁺ than in n-CeO₂ treated in planarian. X-ray absorption near edge spectroscopy (XANES) analysis revealed that 12.8 % of n-CeO₂ (5.95 mg/kg Ce per planarian) was transformed to Ce³⁺ 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-CeO₂ is a slow process, it may cause long-term chronic toxicity to planarians due to the slow while sustained release of toxic Ce³⁺ ions.

Insights from a Bibliometrics-Based Analysis of Publishing and Research Trends on Cerium Oxide from 1990 to 2020

The purpose of this study is to evaluate the literature for research trends on cerium oxide from 1990 to 2020 and identify gaps in knowledge in the emerging application(s) of CeONP. Bibliometric methods were used to identify themes in database searches from PubMed, Scopus and Web of Science Core Collection using SWIFT-Review, VOSviewer and SciMAT software programs. A systematic review was completed on published cerium oxide literature extracted from the Scopus database (n = 17,115), identifying themes relevant to its industrial, environmental and biomedical applications. A total of 172 publications were included in the systematic analysis and categorized into four time periods with research themes identified; "doping additives" (n = 5, 1990-1997), "catalysts" (n = 32, 1998-2005), "reactive oxygen species" (n = 66, 2006-2013) and "pathology" (n = 69, 2014-2020). China and the USA showed the highest number of citations and publications for cerium oxide research from 1990 to 2020. Longitudinal analysis showed CeONP has been extensively used for various applications due to its catalytic properties. In conclusion, this study showed the trend in research in CeONP over the past three decades with advancements in nanoparticle engineering like doping, and more recently surface modification or functionalization to further enhanced its antioxidant abilities. As a result of recent nanoparticle engineering developments, research into CeONP biological effects have highlighted its therapeutic potential for a range of human pathologies such as Alzheimer's disease. Whilst research over the past three decades show the versatility of cerium oxide in industrial and environmental applications, there are still research opportunities to investigate the potential beneficial effects of CeONP in its application(s) on human health.

Selenium nanoparticles reduce Ce accumulation in grains and ameliorate yield attributes in mung bean (Vigna radiata) exposed to CeO2

Exposure of crops to CeO₂ nanoparticles (nCeO₂) in agricultural environments impact crop quality and human health. In this regard, the effects of selenium nanoparticles (nSe) on the yield and quality of Vigna radiata (L.) exposed to nCeO₂ were investigated. The experiment was carried out as a factorial with two factors: NPs (nCeO₂, and nSe) as factor one and concentrations as factor two [(0, 250, 500 and 1000 mg/L nCeO₂; 0, 25, 50 and 75 mg/L nSe)]. Nanoparticles were foliar applied to 45-day old mung bean shoot in two steps and one-week interval. At 250-1000 mg/L, nCeO₂ increased P, protein and Ce accumulation in grain. Additionally, at 1000 mg/L, the nCeO_2, significantly decreased seed number, yield, Fe, and Zn storage in seeds. Conversely, at 25 and 50 mg/L, nSe stimulated the growth and yield of mung bean, and significantly increased P, Fe, Zn, and Se in seeds, but reduced the protein content in seeds. The Se₂₅+Ce₂₅₀ and Se₅₀+Ce₂₅₀ significantly increased pod number, seed number, grain weight, yield, Fe, Zn and Se storage in grains. In contrast, the Ce accumulation in seeds decreased in all combination treatments (nCeO₂ + nSe) compared to their respective single nCeO₂ treatments. Moreover, in the plants exposed to high nCeO₂ concentrations, nSe application resulted in undamaged vacuoles, less starch granules' accumulation, significant yield improvement, and elevated Fe, Se, and Zn in seeds. Data suggest that selenium nanoparticles prevent nCeO₂ stress in mung bean and improve grain production and quality.

Regulatory actions of rare earth elements (La and Gd) on the cell cycle of root tips in rice seedlings (Oryza sativa L.)

The continuous expansion of the application of rare earth elements (REEs) in various fields has attracted attention to their biosafety. At present, the molecular mechanisms underlying the biological effects of REEs are unclear. In this study, the effects of lanthanum (La) and gadolinium (Gd) on cell cycle progression in the root tips of rice seedlings were investigated. Low concentrations of REEs (0.1 mg L^-1) induced an increase in the number of cells in the prophase and metaphase, while high concentrations of REEs (10 mg L^-1) induced an increase in the number of cells in the late and terminal stages of the cell cycle, and apoptosis or necrosis. Additionally, low concentrations of REEs induced a significant increase in the expression of the cell cycle factors WEE1, CDKA;1, and CYCB1;1, and promoted the G2/M phase and accelerated root tip growth. However, at high REEs concentrations, the DNA damage response sensitized by BRCA1, MRE11, and TP53 could that prevent root tip growth by inhibiting the transcription factor E2F, resulting in obvious G1/S phase transition block and delayed G2/M phase conversion. Furthermore, by comparing the biological effect mechanisms of La and Gd, we found that these two REEs share regulatory actions on the cell cycle of root tips in rice seedlings.

The modification of biomass waste by cerium-based MOFs for efficient phosphate removal: excellent performance and reaction mechanism

Due to the possibility of causing eutrophication, excessive phosphate discharged into water bodies always threatens the stabilization of aquatic ecosystem. A promising strategy is to remove phosphate from water by the utilization of biomass waste as adsorbents. In this paper, the corn straw (CS) and pine sawdust (PS) are chosen for adsorption; however, the phosphate removal capacities of them are very limited. Considering the high phosphate uptake of trivalent cerium, Ce (III)-based nanoparticles (CD and CT) are selected to be loaded on the biomass by hydrothermal synthesis to obtain four modified materials. CD is metal organic frameworks (MOFs) with Ce5(BDC)7.5(DMF)4 as its molecular structure, while CT is MOFs derivatives with [Ce (HCOO)]n as its crystal structure. The adsorption capacities of CS-CD, PS-CD, CS-CT and PS-CT reach 181.38, 183.27, 225.55 and 186.23 mg/g. But on account of the different molecular structures, CS-CD and PS-CD achieve great phosphate uptake under wide applicable scope of pH from 2 to 11, whereas CS-CT and PS-CT only under acidic conditions. The analysis of the adsorption mechanism indicates that due to the unsaturated coordination bond of CD, it could remove phosphate through coprecipitation and ion exchange even under alkaline conditions.

Assessment of the biotoxicity of lanthanides (La, Ce, Gd, and Ho) on zebrafish (Danio rerio) in different water environments

The expanding applications of lanthanides (Ln) in various aspects have raised concerns about their biosafety. Slight changes in the chemical composition of environmental media can significantly affect the biological effectiveness of poorly water-soluble Ln; however, the knowledge of the effects of environmental factors on Ln toxicity remains limited. Here, the effects of pH, HCO₃^-, Ca²⁺, Mg²⁺, Na⁺, K⁺, Cl^-, and SO₄^2- on the bioefficacy and biotoxicity of Ln (La, Ce, Gd, and Ho) were comparatively studied using zebrafish (Danio rerio) as the test organism. In the standard water, the toxicity of Ln in zebrafish was significantly correlated with pH, HCO₃^-, and Ca²⁺-Mg²⁺ levels in the medium but not with the levels of Cl^-, Na⁺, K⁺, and SO₄^2-. At the beginning of the test, the four Ln were complexed with HCO₃^- in the medium to form precipitates. A decrease in pH or HCO₃^- concentration can promote the conversion of granular Ln to a soluble state, thus enhancing their bioavailability, biotoxicity, and bioaccumulation. At a pH of 5.0 and 0.2 mmol·L^-1 HCO₃^-, where Ln precipitates were not found, the four Ln showed a consistent trend of 96 h-LC50 in zebrafish. These data indicate that the differences in the toxicities of the four Ln in the standard water may be due to differences in the effective states of the individual elements rather than the different toxicities of the elements. Overall, in biological toxicity assessments, Ln can be regarded as a group of elements with additive patterns of toxicity until the differences in their biological toxicity mechanisms are revealed, and the effects of pH and carbonate should be considered.

Designing the ultrasonic treatment of nanoparticle-dispersions via machine learning

Ultrasonication is a widely used and standardized method to redisperse nanopowders in liquids and to homogenize nanoparticle dispersions. One goal of sonication is to disrupt agglomerates without changing the intrinsic physicochemical properties of the primary particles. The outcome of sonication, however, is most of the time uncertain, and quantitative models have been beyond reach. The magnitude of this problem is considerable owing to fact that the efficiency of sonication is not only dependent on the parameters of the actual device, but also on the physicochemical properties such as of the particle dispersion itself. As a consequence, sonication suffers from poor reproducibility. To tackle this problem, we propose to involve machine learning. By focusing on four nanoparticle types in aqueous dispersions, we combine supervised machine learning and dynamic light scattering to analyze the aggregate size after sonication, and demonstrate the potential to improve considerably the design and reproducibility of sonication experiments.

Transcriptome analysis of lipid metabolism in response to cerium stress in the oleaginous microalga Nannochloropsis oculata

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.

Multiomics analyses uncover nanoceria triggered oxidative injury and nutrient imbalance in earthworm Eisenia fetida

The toxic stress caused by nanoceria remains vague owing to the limited efforts scrutinizing its molecular mechanisms. Herein, we investigated the impacts of nanoceria on earthworm Eisenia fetida, at the molecular level using the multiomics-based profiling approaches (transcriptomics, metabolomics, and 16 S rRNA sequencing). Nanoceria (50 and 500 mg/kg) significantly increased the contents of malondialdehyde (MDA), Fe, and K in worms, suggesting oxidative injury and nutrient imbalance. This was corroborated by the transcriptomic and metabolomic analyses. Nanoceria decreased the levels of certain genes and metabolites associated with glycerolipid and glycerophospholipid metabolisms, suggesting the production of reactive oxygen species and subsequent oxidative stress. Additionally, the ABCD3 gene belonging to ABC transporter family was upregulated, facilitating Fe uptake by worms. Moreover, the higher contents of MDA, Fe, and K after exposure were tightly associated with the imbalanced intestinal flora. Specifically, a higher relative abundance of Actinobacteriota and a lower relative abundance of Proteobacteria and Patescibacteria were induced. This study, for the first time, revealed that nanoceria at nonlethal levels caused oxidative stress and nutrient imbalance of earthworms from the perspective of genes, metabolites, and gut microbiome perturbations, and also established links between the gut microbiome and the overall physiological responses of the host.

Toxic Effects of Two Representative Rare Earth Elements (La and Gd) on Danio rerio Based on Transcriptome Analysis

The expanding applications of rare earth elements (REEs) in various fields have raised concerns about their biosafety. However, previous studies are insufficient to elucidate their toxic effects and mechanisms of action and whether there are uniform or predictable toxicity patterns among REEs. Herein, we investigated the toxic effects of two representative REEs (lanthanum (La) and gadolinium (Gd)) on zebrafish (Danio rerio) through toxicity experiments and transcriptome analysis. The results of the toxicity experiments showed that the two REEs have similar lethality, with half-lethal concentrations (LC50) at micromolar levels and mixed toxicity showing additive effects. Differential expression gene screening and functional group enrichment analysis showed that La and Gd might affect the growth and development of Danio rerio by interfering with some biological molecules. The two REEs showed significant effects on the metabolic pathways of exogenous or endogenous substances, including glutathione sulfotransferase and acetaldehyde dehydrogenase. Moreover, some basic biological processes, such as DNA replication, the insulin signaling pathway, and the p53 signaling pathway, were significantly enriched. Overall, the toxicity patterns of La and Gd may affect some biological processes with different intensities; however, there are many similarities in their toxicity mechanisms and modes of action. The concentrations investigated in this study were comparable to those of REE residues at highly contaminated sites, thus mimicking the ecotoxicological effects at environmentally relevant concentrations.

Environmental geochemistry of higher radioactivity in a transboundary Himalayan river sediment (Brahmaputra, Bangladesh): potential radiation exposure and health risks

This study of a downstream segment (Brahmaputra, Bangladesh) of one of the longest transboundary (China-India-Bangladesh) Himalayan rivers reveals elevated radioactivity compared to other freshwater basins across the world. Naturally occurring radioactive nuclides (²²⁶Ra, ²³²Th, and ⁴⁰K) and metal contents (transition metals, Fe, Ti, Sc, and V; rare earth elements, La, Ce, Eu, Sm, Dy, Yb, and Lu; high field strength elements, Ta and Hf; and actinides, Th and U) in thirty sediment samples were measured by HPGe γ-spectrophotometry and research reactor-based neutron activation analysis, respectively. We systematically investigated the mechanism of the deposition of higher radioactivity concentrations and rare earth elements (REEs) associated with heavy minerals (HMs) and photomicrograph-based mineralogical analysis. The results show that total REEs (∑REE) and Ta, Hf, U, and Th are generally 1.5- to 3.0-fold elevated compared to crustal values associated with -δEu and -δCe anomalies, suggesting a felsic source provenance. The enrichment of light REEs (×1.5 upper continental crust (UCC)) and Th (×1.9 UCC), besides Th/U (=7.74 ± 2.35) and ²³²Th/⁴⁰K ratios, along with the micrographic and statistical approaches, revealed the elevated presence of HMs. Fluvial suspended sedimentary transportation (from upstream) followed by mineralogical recycling and sorting enriched the HM depositions in this basin. Bivariate plots, including La/Th-Hf, La/Th-Th/Yb, and La/V-Th/Yb, revealed significant contributions of felsic source rock compared to mafic sources. The assessment of radiological hazards demonstrates ionizing-radiation-associated health risks to the local residents and people inhabiting houses made from Brahmaputra River sediments (as construction material).

Activation of SIRT-1 Pathway by Nanoceria Sheds Light on Its Ameliorative Effect on Doxorubicin-Induced Cognitive Impairment (Chemobrain): Restraining Its Neuroinflammation, Synaptic Dysplasticity and Apoptosis

Chemo fog is one of the most serious health concerns encountered by cancer survivors receiving doxorubicin (DOX)-based chemotherapy. Oxidative stress, neuroinflammation, apoptosis and impairment of synaptic plasticity are regarded as the key factors implicated in DOX-induced cognitive impairment. This research aimed to assess the possible neuroprotective effect of cerium oxide nanoparticles (CeNPs) against DOX-induced neurotoxicity. Forty-eight rats were divided into four groups (12 rats/group): control group, CeNPs group (received oral CeNPs solution (35 mg/kg) daily for 4 weeks), and DOX group (were administered DOX intraperitoneally (2 mg/kg, once/week for 4 weeks)) and DOX+ CeNPs group. The findings revealed that CeNPs mitigated behavioral alterations in DOX-induced cognitive deficit. Additionally, CeNPs alleviated the histopathological abnormalities in hippocampus and ameliorated DOX-induced neuroinflammation by downregulating the expression of NF-κB, TNF-α, IL-1β and IL6. In addition, CeNPs antagonized the apoptosis through reducing the protein expression of cytochrome c and caspase 3. In addition, it stimulated the antioxidant defense, as indicated by upregulating the expression of the Nrf2, HO-1 and PGC-1α genes. CeNPs improved synaptic plasticity via acting on the BDNF. These actions were related through the modification of SIRT-1 expression. Based on the aforementioned results, CeNPs antagonized the doxorubicin-induced neurodegeneration by its antioxidant, anti-inflammatory and antiapoptotic effects, alongside its SIRT-1 mediated mechanisms.

Accumulation of scandium, cerium, europium, hafnium, and tantalum in oats and barley grown in soils that differ in their characteristics and level of contamination

Up to now, information about biogeochemistry of many trace elements is scarce. Meanwhile, all the elements are always present in soil and plants. It may be suggested that the trace elements also play certain role in the biogeochemical processes. The aim of the research was to study bioaccumulation of poorly investigated trace elements (scandium, cerium, europium, hafnium, and tantalum) and well-known elements (chromium, iron, cobalt, zinc, and arsenic) in two crops, oats and barley, and examine how these elements interact with each other as they absorbed by plants. The plants were grown in the soils that differed in their parameters and in level of contamination. Although oats and barley are botanically similar and were grown under the same conditions, the plants differed in the ability to accumulate many elements. The uptake of the elements by the plants also depended on type of soil. For example, concentrations of Cr, Fe, Co, As, Sc, Ce, Eu, Hf, and Ta in roots of the oats grown in slightly contaminated soil were much higher as compared to the concentrations of the elements in roots of the barley grown in the same soil. In leaves of the oats grown in moderately contaminated soil, the concentrations of Cr, As, Ce, Eu, and Ta were statistically significantly higher than those in leaves of the barley grown in the soil. In soils and in plants, relationships between elements were both similar and different. A statistically significant correlation was found between the poorly investigated trace elements and well-studied elements.

Europium-Doped Cerium Oxide Nanoparticles for Microglial Amyloid Beta Clearance and Homeostasis

Alzheimer's disease (AD) is the most common neurodegenerative disorder. Pathologically, the disease is characterized by the deposition of amyloid beta (Aβ) plaques and the presence of neurofibrillary tangles. These drive microglia neuroinflammation and consequent neurodegeneration. While the means to affect Aβ plaque accumulation pharmacologically was achieved, how it affects disease outcomes remains uncertain. Cerium oxide (CeO₂) reduces Aβ plaques, oxidative stress, inflammation, and AD signs and symptoms. In particular, CeO₂ nanoparticles (CeO₂NPs) induce free-radical-scavenging and cell protective intracellular signaling. This can ameliorate the pathobiology of an AD-affected brain. To investigate whether CeO₂NPs affect microglia neurotoxic responses, a novel formulation of europium-doped CeO₂NPs (EuCeO₂NPs) was synthesized. We then tested EuCeO₂NPs for its ability to generate cellular immune homeostasis in AD models. EuCeO₂NPs attenuated microglia BV2 inflammatory activities after Aβ_1-42 exposure by increasing the cells' phagocytic and Aβ degradation activities. These were associated with increases in the expression of the CD36 scavenger receptor. EuCeO₂NPs facilitated Aβ endolysosomal trafficking and abrogated microglial inflammatory responses. We posit that EuCeO₂NPs may be developed as an AD immunomodulator.

Can nanomaterials support the diagnosis and treatment of human infertility? A preliminary review

Human infertilities are disorders that afflict many people all over the world. Both male and female reproductive systems must work together in a precise and coordinated manner and infertility has a wide range of problems for this system. Recent advances in nanomedicine immensely helped design the diagnostic and therapeutic approaches to alleviate human infertility in both sexes. Nanoscience has recently been used by researchers to increase the detection limit of infertility-related biomarkers via fabricating sensitive nanobiosensors for detecting follicle-stimulating hormone (FSH), luteinizing hormone (LH), anti-müllerian hormone (AMH), pregnancy-associated plasma protein-A (PAPP-A), progesterone, and testosterone. At the same time, a variety of nanostructures, including magnetic nanoparticles (i.e., zinc nanoparticles, cerium nanoparticles, gold nanoparticles, silver nanoparticles), nano-vitamins, extracellular vesicles, and spermbots, have shown promising outcomes in the treatment of human infertilities. Despite recent advancements, some nanostructures might have toxic effects on cells, especially germ cells, and must be optimized with the right ingredients, such as antioxidants, nutrients, and vitamins, to obtain the right strategy to treat and detect human infertilities. This review presents recent developments in nanotechnology regarding impairments still faced by human infertility. New perspectives for further use of nanotechnology in reproductive medicine studies are also discussed. In conclusion, nanotechnology, as a tool for reproductive medicine, has been considered to help overcome current impairments.

Phytotoxic effect of sub-3-nm crystalline ceria nanoparticles on the hydroponic growth of Daikon radish microgreens

Cerium oxide nanoparticles (ceria NPs) have been widely used in many industrial applications. They have been proposed as a potential remedy for reducing oxidative stress in biological systems. General concerns over the toxicity of engineered ceria NPs have led to studies of their phytotoxicity in plants. Most of these plant growth studies were conducted in soil using grain crops and commercial ceria NPs of sizes from 6 nm to 100's nm. In this paper, we report our evaluation of the phytotoxicity and uptake of sub-3-nm crystalline ceria NPs by exposing Daikon radish (Raphanus sativus var. longipinnatus) microgreens to these NPs with environmentally relevant concentrations under hydroponic growth conditions. Aqueous suspensions of different concentrations of these ceria NPs (0.1 ppm, 1 ppm, and 10 ppm) were applied to these microgreens for the last 7 days of the 12-day growth period. Our results revealed the uptake of cerium by plant roots and the translocation of cerium to the stems and the cotyledons (seed leaves). The accumulation of cerium was found to be maximum at the roots, followed by the cotyledons and the stems of the plants. Even at the lowest concentration (0.1 ppm) of the sub-3-nm ceria NPs, the accumulation of cerium at the roots significantly stunted the root growth. However, these NP treatments did not show significant changes to the distributions of macro-minerals (Mg, K, and Ca) and micro-minerals (Zn and Cu) in the microgreens at the end of the 12-day growth period. The phytotoxic effect of sub-3-nm crystalline ceria nanoparticles on the hydroponic growth of Daikon radish microgreens was studied. The cerium uptake by the plant and its effect on the bioavailability of major macro-minerals and micro-minerals within the plant were examined.