Dual-mode photoelectrochemical radar based on CdS quantum dot and Ce-MOF for detection of low-abundance disease-associated proteins.

Herein, we developed a convenient and versatile dual-mode electrochemiluminescence (ECL) and photoelectrochemistry (PEC) sensing radar for the detection of Prostate-specific antigen (PSA), which has important implications for detection of low-abundance disease-associated proteins. Cerium-based metal-organic framework (Ce-MOFs) were firstly modified on the electrode, showing well ECL and PEC property. In particular, a unique multifunctional Au@CdS quantum dots (QDs) probe loaded numerous QDs and antibody was fabricated, not only displaying strong ECL and PEC signals, but also having specific recognition to PSA. After the signal probe was linked to the electrode by immune reaction, much amplified signals of ECL and PEC were generated for double-mode detection of PSA. Therefore, this work proposed a multifunctional Au@CdS QDs signal probe with excellent ECL and PEC performance, and developed an ultrasensitive photoelectric biosensing platform for dual-mode detection, which provides an effective method for health monitoring of cancer patients.

CeO2 nanocages with tetra-enzyme mimetic activities for dual-channel ratiometric colorimetric detection of microcystins-LR.

BACKGROUND: Microcystin-leucine-arginine (MC-LR) produced by various cyanobacteria during harmful algal bloom poses serious threats to drinking water safety and human health. Conventional chromatography-based detection methods require expensive instruments and complicated sample pretreatment, limiting their application for on-site detection. Colorimetric aptasensors are simple and rapid, and are amenable to fast detection. However, they provide only one output signal, resulting in poor sensitivity and accuracy. Dual-channel ratiometric colorimetric method based on the peroxidase-like activity of nanozyme can achieve self-calibration by recording two reverse signals, providing significantly enhanced sensitivity and accuracy. RESULTS: CeO2 nanocages (CeO2 NCs) with tetra-enzyme mimetic activities (oxidase-, peroxidase-, catalase- and superoxide dismutase-like activities) were facilely synthesized using zeolitic imidazolate framework-67 (ZIF-67) as sacrificial template. The peroxidase-like activity of CeO2 NCs can be regulated by DNA, and it showed opposite response to two chromogenic substrates (2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) and 3,3',5,5'-tetramethylbenzidine (TMB)), which was mainly attributed to the changed affinity. On the basis of MC-LR aptamer-tunable peroxidase-like activity of CeO2 NCs in TMB and ABTS channel, a dual-channel ratiometric colorimetric aptasensor was constructed for detection of MC-LR. Compared with conventional single-signal colorimetric assays, the proposed method showed lower limit of detection (0.66 pg mL-1) and significantly enhanced sensitivity. Moreover, the practicability of the ratiometric colorimetric assay was demonstrated by detecting MC-LR in real water samples, and satisfactory recoveries (94.9-101.9 %) and low relative standard deviations (1.6-6.3 %) were obtained. SIGNIFICANCE: This work presents a nanozyme-based ratiometric colorimetric aptasensor for MC-LR detection by recording the reverse responses of two chromogenic reactions. Benefiting from the self-calibration function, the method can achieve higher sensitivity and accuracy. The short detection time and practical application in real water samples show great potential for environmental monitoring.

Ceria nanoparticles: biomedical applications and toxicity. / 二氧化铈纳米颗粒：生物医学应用和毒性.

Ceria nanoparticles (CeO2 NPs) have become popular materials in biomedical and industrial fields due to their potential applications in anti-oxidation, cancer therapy, photocatalytic degradation of pollutants, sensors, etc. Many methods, including gas phase, solid phase, liquid phase, and the newly proposed green synthesis method, have been reported for the synthesis of CeO2 NPs. Due to the wide application of CeO2 NPs, concerns about their adverse impacts on human health have been raised. This review covers recent studies on the biomedical applications of CeO2 NPs, including their use in the treatment of various diseases (e.|g., Alzheimer's disease, ischemic stroke, retinal damage, chronic inflammation, and cancer). CeO2 NP toxicity is discussed in terms of the different systems of the human body (e.|g., cytotoxicity, genotoxicity, respiratory toxicity, neurotoxicity, and hepatotoxicity). This comprehensive review covers both fundamental discoveries and exploratory progress in CeO2 NP research that may lead to practical developments in the future.

Injectable hydrogel with doxorubicin-loaded ZIF-8 nanoparticles for tumor postoperative treatments and wound repair.

The need for tumor postoperative treatments aimed at recurrence prevention and tissue regeneration have raised wide considerations in the context of the design and functionalization of implants. Herein, an injectable hydrogel system encapsulated with anti-tumor, anti-oxidant dual functional nanoparticles has been developed in order to prevent tumor relapse after surgery and promote wound repair. The utilization of biocompatible gelatin methacryloyl (GelMA) was geared towards localized therapeutic intervention. Zeolitic imidazolate framework-8@ceric oxide (ZIF-8@CeO2, ZC) nanoparticles (NPs) were purposefully devised for their proficiency as reactive oxygen species (ROS) scavengers. Furthermore, injectable GelMA hydrogels loaded with ZC NPs carrying doxorubicin (ZC-DOX@GEL) were tailored as multifunctional postoperative implants, ensuring the efficacious eradication of residual tumor cells and alleviation of oxidative stress. In vitro and in vivo experiments were conducted to substantiate the efficacy in cancer cell elimination and the prevention of tumor recurrence through the synergistic chemotherapy approach employed with ZC-DOX@GEL. The acceleration of tissue regeneration and in vitro ROS scavenging attributes of ZC@GEL were corroborated using rat models of wound healing. The results underscore the potential of the multifaceted hydrogels presented herein for their promising application in tumor postoperative treatments.

hCeO2@ Cu5.4O nanoparticle alleviates inflammatory responses by regulating the CTSB-NLRP3 signaling pathway.

Inflammatory responses, especially chronic inflammation, are closely associated with many systemic diseases. There are many ways to treat and alleviate inflammation, but how to solve this problem at the molecular level has always been a hot topic in research. The use of nanoparticles (NPs) as anti-inflammatory agents is a potential treatment method. We synthesized new hollow cerium oxide nanomaterials (hCeO2 NPs) doped with different concentrations of Cu5.4O NPs [the molar ratio of Cu/(Ce + Cu) was 50%, 67%, and 83%, respectively], characterized their surface morphology and physicochemical properties, and screened the safe concentration of hCeO2@Cu5.4O using the CCK8 method. Macrophages were cultured, and P.g-lipopolysaccharide-stimulated was used as a model of inflammation and co-cultured with hCeO2@Cu5.4O NPs. We then observe the effect of the transcription levels of CTSB, NLRP3, caspase-1, ASC, IL-18, and IL-1ß by PCR and detect its effect on the expression level of CTSB protein by Western blot. The levels of IL-18 and IL-1ß in the cell supernatant were measured by enzyme-linked immunosorbent assay. Our results indicated that hCeO2@Cu5.4O NPs could reduce the production of reactive oxygen species and inhibit CTSB and NLRP3 to alleviate the damage caused by the inflammatory response to cells. More importantly, hCeO2@Cu5.4O NPs showed stronger anti-inflammatory effects as Cu5.4O NP doping increased. Therefore, the development of the novel nanomaterial hCeO2@Cu5.4O NPs provides a possible new approach for the treatment of inflammatory diseases.

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.

Nanoceria-Mediated Cyclosporin A Delivery for Dry Eye Disease Management through Modulating Immune-Epithelial Crosstalk.

Dry eye disease (DED) affects a substantial worldwide population with increasing frequency. Current single-targeting DED management is severely hindered by the existence of an oxidative stress-inflammation vicious cycle and complicated intercellular crosstalk within the ocular microenvironment. Here, a nanozyme-based eye drop, namely nanoceria loading cyclosporin A (Cs@P/CeO2), is developed, which possesses long-term antioxidative and anti-inflammatory capacities due to its regenerative antioxidative activity and sustained release of cyclosporin A (CsA). In vitro studies showed that the dual-functional Cs@P/CeO2 not only inhibits cellular reactive oxygen species production, sequentially maintaining mitochondrial integrity, but also downregulates inflammatory processes and repolarizes macrophages. Moreover, using flow cytometric and single-cell sequencing data, the in vivo therapeutic effect of Cs@P/CeO2 was systemically demonstrated, which rebalances the immune-epithelial communication in the corneal microenvironment with less inflammatory macrophage polarization, restrained oxidative stress, and enhanced epithelium regeneration. Collectively, our data proved that the antioxidative and anti-inflammatory Cs@P/CeO2 may provide therapeutic insights into DED management.

Frustrated Lewis pairs created by Ce-doped Bi2MoO6: A universal strategy to promote efficient utilization of H2O2 for Fenton-like photodegradation.

Photo-Fenton-like technology based on H2O2 is considered as an ideal strategy to generate reactive oxygen species (ROS) for antibiotic degradation, but O2 overflow in the process severely limits the utilization efficiency of H2O2. Herein, we fabricate Bi2MoO6 (BMO) photocatalyst modified with Frustrated Lewis pairs (FLPs) as a Fenton catalyst model for enhancing reuse of spilled O2. The FLPs created by the introduction of cerium and oxygen vacancy were found to contribute to regulate the electronic structure of BMO and further improve the acidic and basic properties of photocatalyst surface. More importantly, the frustrated acid and base sites can enhance the H2O2 and O2 interfacial adsorption process and provide an Ce4+-Ov-O2- active site on the surface of Ce-BMO nanosheets, which can promote O2/•O2-/1O2/H2O2 redox cycles to achieve high H2O2 utilization efficiency. Specifically, in the experiment using tetracycline as a photocatalytic degradation object, the degradation activity of Ce-BMO was 2.15 times higher than that of BMO pure phase. Quenching experiments and EPR assays also confirmed that 1O2 and •O2- were the dominant oxidative species. This study systematically reveals the design of Fenton photocatalytic active sites at the atomic scale and provides new insights into constructing FLPs photocatalysts with high H2O2 utilization efficiency.

Enhanced interfacial effect via acid theory with boosted photocatalytic performance of nitenpyram removal.

Surface reaction is a prominent aspect that affects the efficiency of photocatalysis. In this work, acid theory was employed to facilitate the reaction dynamics and enhance the interfacial effect between photocatalysts and target molecules. The photocatalytic removal efficiency of NTP was 66 % for bare CdS in 50 min with apparent rate constants of 0.023 compare to 96 % with apparent rate constants of 0.065 for 5% Ce-CdS. The introduced Ce atom as bifunctional active site reduces the energy barrier of O2 adsorption, strengthens the interfacial effect and accelerates the electrons transfer, which could facilitate surface reaction process and boost the photocatalytic performance.

Defect-rich sonosensitizers based on CeO2 with Schottky heterojunctions for boosting sonodynamic/chemodynamic synergistic therapy.

Sonodynamic therapy (SDT) has been recognized as a promising treatment for cancer due to its advantages of superior specificity, non-invasiveness, and deep tissue penetration. However, the antitumor effect of SDT remains restricted by the limited generation of reactive oxygen species (ROS) due to the lack of highly efficient sonosensitizers. In this work, we developed the novel sonosensitizer Pt/CeO2-xSx by constructing oxygen defects through S doping and Pt loading in situ. Large amounts of oxygen defects have been obtained by S doping, endowing Pt/CeO2-xSx with the ability to suppress electron-hole recombination, further promoting ROS production. Moreover, the introduction of Pt nanoparticles can not only produce oxygen in situ for relieving hypoxia but also form a Schottky heterojunction with CeO2-xSx for further inhibiting electron-hole recombination. In addition, Pt/CeO2-xSx could effectively deplete overexpressed glutathione (GSH) via redox reactions, amplifying oxidative stress in the tumor microenvironment (TME). Combined with the excellent POD-mimetic activity, Pt/CeO2-xSx can achieve highly efficient synergistic therapy of SDT and chemodynamic therapy (CDT). All these findings demonstrated that Pt/CeO2-xSx has great potential for cancer therapy, and this work provides a promising direction for designing and constructing efficient sonosensitizers.

Controlled-Release Electrochemiluminescence Biosensor with Strong Self-On Effect by a Multiple Signal Amplification Strategy for Trace Detection of Prostate-Specific Antigen.

The enhancement of sensitivity in biological analysis detection can reduce the probability of false positives of the biosensor. In this work, a novel self-on controlled-release electrochemiluminescence (CRE) biosensor was designed by multiple signal amplification and framework-enhanced stability strategies. As a result, the changes of the ECL signal were enhanced before and after the controlled-release process, achieving sensitive detection of prostate-specific antigen (PSA). Specifically, for one thing, Fe3O4@CeO2-NH2 with two paths for enhancing the generation of coreactant radicals was used as the coreaction accelerator to boost ECL performance. For another, due to the framework stability, zeolitic imidazolate framework-8-NH2 (ZIF-8-NH2) was combined with luminol to make the ECL signal more stable. Based on these strategies, the constructed CRE biosensor showed a strong self-on effect in the presence of PSA and high sensitivity in a series of tests. The detection range and limit of detection (LOD) were 5 fg/mL to 10 ng/mL and 2.8 fg/mL (S/N = 3), respectively, providing a feasible approach for clinical detection of PSA.

Unveiling the Function of Oxygen Vacancy on Facet-Dependent CeO2 for the Catalytic Destruction of Monochloromethane: Guidance for Industrial Catalyst Design.

Secondary pollution remains a critical challenge for the catalytic destruction of chlorinated volatile organic compounds (CVOCs). By employing experimental studies and theoretical calculations, we provide valuable insights into the catalytic behaviors exhibited by ceria rods, cubes, and octahedra for monochloromethane (MCM) destruction, shedding light on the elementary reactions over facet-dependent CeO2. Our findings demonstrate that CeO2 nanorods with the (110) facet exhibit the best performance in MCM destruction, and the role of vacancies is mainly to form a longer distance (4.63 Å) of frustrated Lewis pairs (FLPs) compared to the stoichiometric surface, thereby enhancing the activation of MCM molecules. Subsequent molecular orbital analysis showed that the adsorption of MCM mainly transferred electrons from the 3σ and 4π* orbitals to the Ce 4f orbitals, and the activation was mainly caused by weakening of the 3σ bonding orbitals. Furthermore, isotopic experiments and theoretical calculations demonstrated that the hydrogen chloride generated is mainly derived from methyl in MCM rather than from water, and the primary function of water is to form excess saturated H on the surface, facilitating the desorption of generated hydrogen chloride.

Biochemical and biophysical interaction of rare earth elements with biomacromolecules: A comprehensive review.

The growing utilization of rare earth elements (REEs) in industrial and technological applications has captured global interest, leading to the development of high-performance technologies in medical diagnosis, agriculture, and other electronic industries. This accelerated utilization has also raised human exposure levels, resulting in both favourable and unfavourable impacts. However, the effects of REEs are dependent on their concentration and molecular species. Therefore, scientific interest has increased in investigating the molecular interactions of REEs with biomolecules. In this current review, particular attention was paid to the molecular mechanism of interactions of Lanthanum (La), Cerium (Ce), and Gadolinium (Gd) with biomolecules, and the biological consequences were broadly interpreted. The review involved gathering and evaluating a vast scientific collection which primarily focused on the impact associated with REEs, ranging from earlier reports to recent discoveries, including studies in human and animal models. Thus, understanding the molecular interactions of each element with biomolecules will be highly beneficial in elucidating the consequences of REEs accumulation in the living organisms.

In-situ growth of CeO2 on biofilms: Innovative nanoparticles for photothermal therapy & multi-pronged attack on Alzheimer's disease.

Alzheimer's disease (AD) is complex and multifactorial, and its pathogenesis involves multiple factors and processes. This study pioneered the in situ growth of cerium oxide nanoparticles on macrophage membranes (Ce-RAW). Further, carbon quantum dots (CQD) were biomimetically modified by Ce-RAW, leading to the synthesis of a multifunctional nanocomposite (CQD-Ce-RAW). Within the framework of this research, CQD-Ce-RAW was strategically combined with photothermal therapy (PTT), aiming to achieve a more significant therapeutic effect. The macrophage membrane confers the system with anti-phagocytic and anti-inflammatory biological functions. More importantly, the ultra-small size of cerium oxide grown on the membrane acts as a reactive oxygen species (ROS) scavenger and alleviates the degree of oxidative stress. Meanwhile, CQD as a photosensitizer helps dissociate amyloid-ß (Aß) aggregates and chelates excess copper ions, thus further inhibiting Aß aggregation. Cell experiments showed that CQD-Ce-RAW combined with PTT could effectively degrade and inhibit the aggregation of Aß, remove ROS, and improve cell survival rate. The results of in vivo photothermal experiments demonstrated that near-infrared light enhanced the efficiency of drug penetration through the blood-brain barrier and facilitated its accumulation in brain tissue. This comprehensive therapeutic approach can intervene in the disease progression from multiple pathways, providing a new prospect for treating AD.

Microplastic contaminants detection in aquatic environment by hydrophobic cerium oxide nanoparticles.

Microplastics (MPs) poses a significant threat to ecosystems and human health, demanding immediate attention. The reported research work offers an effective and low cost method towards the detection of toxic MPs. In this study, hydrophobic cerium oxide nanoparticles (CeO2 NPs) are synthesized and applied as promising electrode material for the detection of two different types of MPs, i.e. polyethylene (PE) and polypropylene (PP). Through electrochemical analyses, such as cyclic voltammetry (CV) and linear sweep voltammetry (LSV), hydrophobic CeO2 NPs modified glassy carbon electrode (GCE) based sensor demonstrated remarkable sensitivity of ∼0.0343 AmLmg-1cm-2 and detection limit of ∼0.226 mgmL-1, with promising correlation coefficient (R2) towards the detection of PE (∼27-32 µm). Furthermore, hydrophobic CeO2 NPs modified GCE exhibited promising stability and reproducibility towards PE (∼27-32 µm), suggesting the promising potential of hydrophobic CeO2 NPs as electrode materials for an electrochemical microplastics detection.

Cerium oxide and neodymium oxide phytoextraction by ryegrass in bioenhanced hydroponic environments.

Sustainable technologies for the recovery of rare earth elements (REE) from waste need to be developed to decrease the volume of ore mining extractions and its negative environmental consequences, while simultaneously restoring previously impacted lands. This is critical due to the extensive application of REE in everyday life from electronic devices to energy and medical technologies, and the dispersed distribution of REE resources in the world. REE recovery by plants has been previously studied but the feasibility of REE phytoextraction from a poorly soluble solid phase (i.e., nanoparticles) by different plant species has been rarely investigated. In this study, the effect of biostimulation and bioaugmentation on phytorecovery of REE nanoparticles (REE-NP) was investigated by exposing ryegrass seeds to REE-NP in hydroponic environments. This was studied in two sets of experiments: bioaugmentation (using CeO2 nanoparticles and Methylobacterium extorquens AM1 pure culture), and biostimulation (using CeO2 or Nd2O3 nanoparticles and endogenous microorganisms). Addition of M. extorquens AM1 in bioaugmentation experiment including 500 mg/L CeO2 nanoparticles could not promote the nanoparticles accumulation in both natural and surface-sterilized treatments. However, it enhanced the translocation of Ce from roots to shoots in sterile samples. Moreover, another REE-utilizing bacterium, Bacillus subtilis, was enriched more than M. extorquens in control samples (no M. extorquens AM1), and associated with 52% and 14% higher Ce extraction in both natural (165 µg/gdried-plant) and surface-sterilized samples (136 µg/gdried-plant), respectively; showing the superior effect of endogenous microorganisms' enrichment over bioaugmentation in this experiment. In the biostimulation experiments, up to 705 µg/gdried-plant Ce and 19,641 µg/gdried-plant Nd could be extracted when 500 mg/L REE-NP were added. Furthermore, SEM-EDS analysis of the surface and longitudinal cross-sections of roots in Nd2O3 treatments confirmed surface and intracellular accumulation of Nd2O3-NP. These results demonstrate stimulation of endogenous microbial community can lead to an enhanced REE phytoaccumulation.

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.

Phosphotungstic Acid as a Dechlorination Agent Collaborates with CeO2 for Synergistic Catalytic Elimination of NOx and Chlorobenzene.

The development of efficient technologies for the synergistic catalytic elimination of NOx and chlorinated volatile organic compounds (CVOCs) remains challenging. Chlorine species from CVOCs are prone to catalyst poisoning, which increases the degradation temperature of CVOCs and fails to balance the selective catalytic reduction of NOx with the NH3 (NH3-SCR) performance. Herein, synergistic catalytic elimination of NOx and chlorobenzene has been originally demonstrated by using phosphotungstic acid (HPW) as a dechlorination agent to collaborate with CeO2. The conversion of chlorobenzene was over 80% at 270 °C, and the NOx conversion and N2 selectivity reached over 95% at 270-420 °C. HPW not only allowed chlorine species to leave as inorganic chlorine but also enhanced the BroÌ·nsted acidity of CeO2. The NH4+ produced in the NH3-SCR process can effectively promote the dechlorination of chlorobenzene at low temperatures. HPW remained structurally stable in the synergistic reaction, resulting in good water resistance and long-term stability. This work provides a cheaper and more environmentally friendly strategy to address chlorine poisoning in the synergistic reaction and offers new guidance for multipollutant control.

A novel nano-cerium oxide functionalized biochar composite for degradation of organic dye: insight of the photocatalysis mechanism.

Recently, visible-light-driven photocatalysis attracts much concerns in the remediation of environmental organic pollutants. In this study, the cerium doped biochar was fabricated through the hydrothermal method, and served as an efficient photocatalyst towards rhodamine B degradation under visible light irradiation. Almost 100% of rhodamine B was removed by 2.0 g·L-1 cerium doped biochar after 60 min of visible light irradiation at pH 3, but only about 25.50% and 29.60% of rhodamine B was removed by cerium dioxide and biochar under identical conditions. The degradation process coincided well with the pseudo-first-order kinetic model, and the photodegradation rate constant of cerium doped biochar was 0.0485·min-1, which was respectively 97 and 44 times that of biochar (0.0005·min-1) and cerium dioxide (0.0011·min-1). According to the trapping experiments and electron spin resonance spectroscopy analysis, h+, O2-∙ and ∙OH all participated in the degradation of rhodamine B in the cerium doped biochar photocatalytic systems, and the function of h+ and ∙OH was dominated. Consequently, the biochar could not only be an excellent carrier for supporting cerium dioxide, but also greatly improved its photocatalytic activity. The band gap of cerium doped biochar was narrower than cerium dioxide, which could improve the separation and migration of photogenerated electron-hole pairs under visible-light excitation, thus ultimately enhanced the degradation of rhodamine B. This work provided a deeper understanding of the preparation of biochar-based photocatalyst and its application in the remediation of environmental organic pollution.

Safety assessment and gastrointestinal retention of orally administered cerium oxide nanoparticles in rats.

Cerium oxide nanoparticles (CeO2 NPs, NM-212) are well-known for their catalytic properties and antioxidant potential, and have many applications in various industries, drug delivery, and cosmetic formulations. CeO2 NPs exhibit strong antimicrobial activity and can be used to efficiently remove pathogens from different environments. However, knowledge of the toxicological evaluation of CeO2 NPs is too limited to support their safe use. In this study, CeO2 NPs were orally administered to Sprague Dawley rats for 13 weeks at the doses of 0, 10, 100, and 1000 mg/kg bw/day, followed by a four week recovery period. The hematology values for the absolute and relative reticulocyte counts in male rats treated with 1000 mg/kg bw/day CeO2 NPs were lower than those in control rats. The clinical chemistry values for sodium and chloride in the treated male rat groups (100 and 1000 mg/kg/day) and total protein and calcium in the treated female rat groups (100 mg/kg/day) were higher than those in the control groups. However, these changes were not consistent in both sexes, and no abnormalities were found in the corresponding pathological findings. The results showed no adverse effects on any of the parameters assessed. CeO2 NPs accumulated in the jejunum, colon, and stomach wall of rats administered 1000 mg/kg CeO2 NPs for 90 days. However, these changes were not abnormal in the corresponding histopathological and immunohistochemical examinations. Therefore, 1000 mg/kg bw/day may be considered the "no observed adverse effect level" of CeO2 NPs (NM-212) in male and female SD rats under the present experimental conditions.