Thiourea enhanced oxidase-like activity of CeO2/CuxO nanozyme for fluorescence/colorimetric detection of thiourea and glutathione.

A novel fluorescence/colorimetric dual-mode sensor, based on enhancement of the oxidase-like activity of CeO2/CuxO nanozyme towards the oxidation of o-phenylenediamine (OPD) induced by thiourea (TU), has been proposed for TU detection. The catalytic activity enhancement on CeO2/CuxO can be attributed to the strong electron-donation ability of TU, which promoted hydroxyl radical generation and amplified OPD oxidization with enhanced dual-signal readout. By integrating a portable paper-chip and smartphone system, this CeO2/CuxO-OPD system achieved on-site visual colorimetric analysis of TU. The dual-mode sensor demonstrated high sensitivity and specificity in recognizing TU, with a detection limit (LOD) of 1.90 µM and a linear range (LR) 2.5-80 µM in fluorescent mode; as well as an LOD of 6.69 µM and an LR 10-250 µM in colorimetric mode. Furthermore, the CeO2/CuxO-TU-OPD system has been designed for dual-mode glutathione (GSH) detection with enhanced sensitivity, achieving an LOD of 0.19 µM and an LR 0.5-10 µM in fluorescent mode; as well as an LOD of 1.24 µM and an LR 1.25-25 µM in colorimetric mode. Additionally, GSH discrimination (fluorescent mode) was successfully achieved in different biological samples, showing good consistency with the standard method. The recoveries ranged from 96.8 % to 116.7 % in serum samples and from 97.3 % to 107.7 % in cell lysates, with RSDs less than 2 %. This work not only introduced a novel approach to enhance oxidase-like activity of nanozymes but also provided an efficient field-suitable tool for enhanced dual-mode response towards TU and GSH.

Promotion effect of Ce and Ta co-doping on the NH3-SCR performance over V2O5/TiO2 catalyst.

NH3-SCR (SCR: Selective catalytic reduction) is an effective technology for the de-NOx process from both mobile and stationary pollution sources, and the most commonly used catalysts are the vanadia-based catalysts. An innovative V2O5-CeO2/TaTiOx catalyst for NOx removal was prepared in this study. The influences of Ce and Ta in the V2O5-CeO2/TaTiOx catalyst on the SCR performance and physicochemical properties were investigated. The V2O5-CeO2/TaTiOx catalyst not only exhibited excellent SCR activity in a wide temperature window, but also presented strong resistance to H2O and SO2 at 275 ℃. A series of characterization methods was used to study the catalysts, including H2-temperature programmed reduction, X-ray photoelectron spectroscopy, NH3-temperature programmed desorption, etc. It was discovered that a synergistic effect existed between Ce and Ta species. The introduction of Ce and Ta enlarged the specific surface area, increased the amount of acid sites and the ratio of Ce3+, (V3++V4+) and Oα, and strengthened the redox capability which were related to synergistic effect between Ce and Ta species, significantly improving the NH3-SCR activity.

Cu,Ce-containing phosphotungstates as laccase-like nanozyme for colorimetric detection of Cr(VI) and Fe(â ¢).

Herein, a nanocomposite of Cu,Ce-containing phosphotungstates (Cu,Ce-PTs) with outstanding laccase-like activity was fabricated via a one-pot microwave-assisted hydrothermal method. Notably, it was discovered that both Fe3+ and Cr6+ could significantly enhance the electron transfer rates of Ce3+ and Ce4+, along with generous Cu2+ with high catalytic activity, thereby promoting the laccase-like activity of Cu,Ce-PTs. The proposed system can be used for the detection of Fe3+ and Cr6+ in a range of 0.667-333.33 µg/mL and 0.033-33.33 µg/mL with a low detection limit of 0.135 µg/mL and 0.0288 µg/mL, respectively. The proposed assay exhibits excellent reusability and selectivity and can be used in traditional Chinese medicine samples analysis.

In-situ activation of biomimetic single-site bioorthogonal nanozyme for tumor-specific combination therapy.

Copper-catalyzed click chemistry offers creative strategies for activation of therapeutics without disrupting biological processes. Despite tremendous efforts, current copper catalysts face fundamental challenges in achieving high efficiency, atom economy, and tissue-specific selectivity. Herein, we develop a facile "mix-and-match synthetic strategy" to fabricate a biomimetic single-site copper-bipyridine-based cerium metal-organic framework (Cu/Ce-MOF@M) for efficient and tumor cell-specific bioorthogonal catalysis. This elegant methodology achieves isolated single-Cu-site within the MOF architecture, resulting in exceptionally high catalytic performance. Cu/Ce-MOF@M favors a 32.1-fold higher catalytic activity than the widely used MOF-supported copper nanoparticles at single-particle level, as first evidenced by single-molecule fluorescence microscopy. Furthermore, with cancer cell-membrane camouflage, Cu/Ce-MOF@M demonstrates preferential tropism for its parent cells. Simultaneously, the single-site CuII species within Cu/Ce-MOF@M are reduced by upregulated glutathione in cancerous cells to CuI for catalyzing the click reaction, enabling homotypic cancer cell-activated in situ drug synthesis. Additionally, Cu/Ce-MOF@M exhibits oxidase and peroxidase mimicking activities, further enhancing catalytic cancer therapy. This study guides the reasonable design of highly active heterogeneous transition-metal catalysts for targeted bioorthogonal reactions.

Removal of arsenic from water by silver nanoparticles and Fe-Ce mixed oxide supported on polymeric anion exchanger.

By encapsulating nanoscale particles of goethite (α-FeO(OH)), hydrous ceric oxide (CeO2·H2O, HCO) and silver nanoparticles (AgNPs) in the pores of polystyrene anion exchanger D201, a novel nanocomposite FeO(OH)-HCO-Ag-D201 was prepared for the effective removal of arsenic from water. The isotherm study shows that FeO(OH)-HCO-Ag-D201 has excellent adsorption performance for As(III) and As(V), with an increased adsorption capacity of As(III) to 40.12 mg/g compared to that of 22.03 mg/g by the composite adsorbent without AgNPs (FeO(OH)-HCO-D201). The adsorption kinetics data showed that the sorption rate of FeO(OH)-HCO-Ag-D201 for As(III) is less than that for As(V), and the adsorption of As(III) and As(V) were consistent with the pseudo-second-order model and the pseudo-first-order model, respectively. Neutral or basic conditions are favored for the adsorption of As(III/V) by FeO(OH)-HCO-Ag-D201. Compared with nitrate/chloride/bicarbonate, sulfate/silicate/phosphate showed more remarkable inhibition of arsenic removal by FeO(OH)-HCO-Ag-D201, whereas natural organic matter showed no interference to the arsenic removal. The As(V) adsorption involved different interactions such as electrostatic attraction and surface complexation, while the adsorption of As(III) involved the part oxidization of As(III) to As(V) and the simultaneous adsorption of As(III) and As(V). In addition to the Ce(IV) in CeO2·H2O acted as an oxidant, the synergistic effect of α-FeO(OH) and AgNPs also contributed to the oxidization of As(III) to As(V). Moreover, the reusable property suggested that this FeO(OH)-HCO-Ag-D201 nanocomposite has great potential for arsenic-contaminated water purification.

LaCo0.95Mo0.05O3/CeO2 composite can promote the effective activation of peroxymonosulfate via Co3+/Co2+ cycle and realize the efficient degradation of hydroxychloroquine sulfate.

Hydroxychloroquine sulfate (HCQ) is extensively utilized due to its numerous therapeutic effects. Because of its properties of high solubility, persistence, bioaccumulation, and biotoxicity, HCQ can potentially affect water bodies and human health. In this study, the LaCo0.95Mo0.05O3-CeO2 material was successfully prepared by the sol-gel process, and it was applied to the experiment of degrading HCQ by activating peroxymonosulfate (PMS). The results of characterization analysis showed that LaCo0.95Mo0.05O3-CeO2 material had good stability, and the problem of particle agglomeration had been solved to some extent. Compared with LaCo0.95Mo0.05O3 material, it had a larger specific surface area and more oxygen vacancies, which was helpful to improve the catalytic activity for PMS. Under optimal conditions, the LaCo0.95Mo0.05O3-CeO2/PMS system degraded 95.5 % of HCQ in 10 min. The singlet oxygen, superoxide radicals, and sulfate radicals were the main radicals for HCQ degradation. The addition of Mo6+/Mo4+ and Ce4+/Ce3+ promoted the redox cycle of Co3+/Co2+ and enhanced the degradation rate of HCQ. Based on density functional theory and experimental analysis, three HCQ degradation pathways were proposed. The analysis of T.E.S.T software showed that the toxicity of HCQ was obviously reduced after degradation. The LaCo0.95Mo0.05O3-CeO2/PMS system displayed excellent reusability and the ability to remove pollutants in a wide range of real-world aqueous environments, with the ability to treat a wide range of pharmaceutical wastewater. In summary, this study provides some ideas for developing heterogeneous catalysts for advanced oxidation systems and provide an efficient, simple, and low-cost method for treating pharmaceutical wastewater that has good practical application potential.

Characteristics of catalytic destruction of dichloromethane and ethyl acetate mixture over HxPO4-RuOx/CeO2 catalyst.

Catalytic destruction is an ascendant technology for the abatement of volatile organic compounds (VOCs) originating from solvent-based industrial processes. The varied composition tends to influence each VOC's catalytic behavior in the reaction mixture. We investigated the catalytic destruction of multi-component VOCs including dichloromethane (DCM) and ethyl acetate (EA), as representatives from pharmaceutical waste gases, over co-supported HxPO4-RuOx/CeO2 catalyst. A mutual inhibitory effect relating to concentrations because of competitive adsorption was verified in the binary VOCs oxidation and EA posed a more negative effect on DCM oxidation owing to EA's superior adsorption capacity. Preferential adsorption of EA on acidic sites (HxPO4/CeO2) promoted DCM activation on basic sites (O2-) and the dominating EA oxidation blocked DCM's access to oxidation centers (RuOx/CeO2), resulting in boosted monochloromethane yield and increased chlorine deposition for DCM oxidation. The impaired redox ability of Ru species owing to chlorine deposition in turn jeopardized deep oxidation of EA and its by-products, leading to increased gaseous by-products such as acetic acid originating from EA pyrolysis. Notably, DCM at low concentration slightly promoted EA conversion at low temperatures with or without water, consistent with the enhanced EA adsorption in co-adsorption analyses. This was mainly due to that DCM impeded the shielding effect of hydrolysate deposition from rapid EA hydrolysis depending on the decreased acidity. Moreover, water benefited EA hydrolysis but decreased CO2 selectivity while the generated water derived from EA was likely to affect DCM transformation. This work may provide theoretical guidance for the promotion of applied catalysts toward industrial applications.

Ti3+/Ti4+ and Co2+/Co3+ redox couples in Ce-doped Co-Ce/TiO2 for enhancing photothermocatalytic toluene oxidation.

Cerium and cobalt loaded Co-Ce/TiO2 catalyst prepared by impregnation method was investigated for photothermal catalytic toluene oxidation. Based on catalyst characterizations (XPS, EPR and H2-TPR), redox cycle between Co and TiO2 (Co2+ + Ti4+ ↔ Co3+ + Ti3+) results in the formation of Co3+, Ti3+ and oxygen vacancies, which play important roles in toluene catalytic oxidation reaction. The introduction of Ce brings in the dual redox cycles (Co2+ + Ti4+ ↔ Co3+ + Ti3+, Co2+ + Ce4+ ↔ Co3+ + Ce3+), further promoting the elevation of reaction sites amount. Under full spectrum irradiation with light intensity of 580 mW/cm2, Co-Ce/TiO2 catalyst achieved 96% of toluene conversion and 73% of CO2 yield, obviously higher than Co/P25 and Co/TiO2. Co-Ce/TiO2 efficiently maintains 10-hour stability test under water vapor conditions and exhibits better photothermal catalytic performance than counterparts under different wavelengths illumination. Photothermal catalytic reaction displays improved activities compared with thermal catalysis, which is attributed to the promotional effect of light including photocatalysis and light activation of reactive oxygen species.

Ce-doped TiO2 supported RuO2 as efficient catalysts for the oxidation of HCl to Cl2.

Reducing the cost of RuO2/TiO2 catalysts is still one of the urgent challenges in catalytic HCl oxidation. In the present work, a Ce-doped TiO2 supported RuO2 catalyst with a low Ru loading was developed, showing a high activity in the catalytic oxidation of HCl to Cl2. The results on some extensive characterizations of both Ce-doped TiO2 carriers and their supported RuO2 catalysts show that the doping of Ce into TiO2 can effectively change the lattice parameters of TiO2 to improve the dispersion of the active RuO2 species on the carrier, which facilitates the production of surface Ru species to expose more active sites for boosting the catalytic performance even under some harsh reaction conditions. This work provides some scientific basis and technical support for chlorine recycling.

Insight into catalytic performance and reaction mechanism for toluene total oxidation over Cu-Ce supported catalyst.

Herein, three supported catalysts, CuO/Al2O3, CeO2/Al2O3, and CuO-CeO2/Al2O3, were synthesized by the convenient impregnation method to reveal the effect of CeO2 addition on catalytic performance and reaction mechanism for toluene oxidation. Compared with CuO/Al2O3, the T50 and T90 (the temperatures at 50% and 90% toluene conversion, respectively) of CuO-CeO2/Al2O3 were reduced by 33 and 39 °C, respectively. N2 adsorption-desorption experiment, XRD, SEM, EDS mapping, Raman, EPR, H2-TPR, O2-TPD, XPS, NH3-TPD, Toluene-TPD, and in-situ DRIFTS were conducted to characterize these catalysts. The excellent catalytic performance of CuO-CeO2/Al2O3 could be attributed to its strong copper-cerium interaction and high oxygen vacancies concentration. Moreover, in-situ DRIFTS proved that CuO-CeO2/Al2O3 promoted the conversion of toluene to benzoate and accelerated the deep degradation path of toluene. This work provided valuable insights into the development of efficient and economical catalysts for volatile organic compounds.

Characterization and Expression of the Cytochrome P450 Genes in Daphnia magna Exposed to Cerium Oxide Nanoparticles.

As cerium oxide nanoparticles (nCeO2) continue to infiltrate aquatic environments, the resulting health risks to exposed aquatic organisms are becoming evident. Cytochrome P450 (CYP) enzymes are integral to the detoxification processes in these species. Herein, we conducted a genomic analysis of CYPs in Daphnia magna, encompassing phylogenetic relationships, gene structure, and chromosomal localization. We identified twenty-six CYPs in D. magna, categorizing them into four clans and seven families, distributed across six chromosomes and one unanchored scaffold. The encoded CYP proteins varied in length from 99 to 585 amino acids, with molecular weights ranging from 11.6 kDa to 66.4 kDa. A quantitative real-time PCR analysis demonstrated a significant upregulation of CYP4C1.4, CYP4C1.5, CYP4C1.6, CYP4c3.3, and CYP4c3.6 in D. magna exposed to 150 mg/L nCeO2 for 24 h. The transcript levels of CYP4C1.3, CYP18a1, CYP4C1.1, and CYP4c3.9 were notably downregulated in D. magna exposed to 10 mg/L nCeO2 for 48 h. A further transcriptomic analysis identified differential expression patterns of eight CYP genes, including CYP4C1.3, in response to nCeO2 exposure. The differential regulation observed across most of the 26 CYPs highlights their potential role in xenobiotic detoxification in D. magna, thereby enhancing our understanding of CYP-mediated toxicological responses to metal nanoparticles in aquatic invertebrates.

Cerium oxide nanoparticles promoted lateral root formation in Arabidopsis by modulating reactive oxygen species and Ca2+ level.

Roots play an important role in plant growth, including providing essential mechanical support, water uptake, and nutrient absorption. Nanomaterials play a positive role in improving plant root development, but there is limited knowledge of how nanomaterials affect lateral root (LR) formation. Poly (acrylic) acid coated nanoceria (cerium oxide nanoparticles, PNC) are commonly used to improve plant stress tolerance due to their ability to scavenge reactive oxygen species (ROS). However, its impact on LR formation remains unclear. In this study, we investigated the effects of PNC on LR formation in Arabidopsis thaliana by monitoring ROS levels and Ca2+ distribution in roots. Our results demonstrate that PNC significantly promote LR formation, increasing LR numbers by 26.2%. Compared to controls, PNC-treated Arabidopsis seedlings exhibited reduced H2 O2 levels by 18.9% in primary roots (PRs) and 40.6% in LRs, as well as decreased O 2 · - levels by 47.7% in PRs and 88.5% in LRs. When compared with control plants, Ca2+ levels were reduced by 35.7% in PRs and 22.7% in LRs of PNC-treated plants. Overall, these results indicate that PNC could enhance LR development by modulating ROS and Ca2+ levels in roots.

From ROS scavenging to boosted osseointegration: cerium-containing mesoporous bioactive glass nanoparticles functionalized implants in diabetes.

Excessive production of reactive oxygen species (ROS) around titanium implants under diabetic conditions causes persistent inflammation, leading to poor osseointegration and even implant failure. Surface modification is an effective way to promote ROS clearance, alleviate inflammation, and stimulate bone formation. In this study, a multifunctional coating is fabricated by introducing cerium (Ce)-containing mesoporous bioactive glass nanoparticles (Ce-MBGNs) onto the titanium surface via an electrophoretic deposition method. The incorporation of Ce-MBGNs remarkably improves surface hydrophilicity by increasing the surface areas. The bioactive ions are appropriately released, thereby promoting mesenchymal stem cell proliferation and differentiation under diabetic conditions. The conversion between Ce(III) and Ce(IV) endows Ce-MBGNs coating with antioxidative nanoenzymes properties to scavenge diabetes-induced ROS, resulting in macrophage polarization towards the anti-inflammatory phenotype. The therapeutic effect of Ce-MBGNs-modified titanium implants is also verified in diabetic rats by inhibiting inflammatory responses and accelerating early osseointegration. Taken together, the findings reveal that the ROS-scavenging and immunomodulation activity of the Ce-MBGNs coating contributes to enhanced osseointegration, and provides a novel implant surface for diabetic patients.

A sandwich-type electrochemical sensor based on RGO-CeO2-Au nanoparticles and double aptamers for ultrasensitive detection of glypican-3.

A sandwich-type electrochemical aptasensor for ultrasensitive detection of glypican-3 (GPC3) was constructed using GPC3 aptamer (GPC3Apt) labelled reduced graphene oxide-cerium oxide-gold nanoparticles (RGO-CeO2-Au NPs) as the signal probe and the same GPC3Apt as the capture probe. The electrochemical redox properties of CeO2 (Ce3+/Ce4+) in the RGO-CeO2-Au NPs indicate the electrochemical signals. When the target GPC3 was present, an "aptamer-protein-aptamer" sandwich structure was formed on the sensing interface due to the specific binding between the protein and aptamers, resulting in an increased electrochemical redox signal detected by differential pulse voltammetry (DPV) technique. Under optimal conditions, the established aptasensor exhibited a logarithmic linear relationship between the current response and GPC3 concentration in the range 0.001-100.0 ng/mL, with a minimum detection limit of 0.74 pg/mL. Using the spike-recovery tests for measurement of the human serum samples, the recovery was from 99.26 to 114.01%, and the RSD range was 3.04 to 5.34%. Furthermore, the sandwich-type electrochemical aptasensor exhibited excellent performance characteristics such as good stability, high specificity, and high sensitivity, demonstrating effective detection of GPC3 in human serum samples and can be used as a clinical detection tool for GPC3.

Preparation of Co-Ce@RM catalysts for catalytic ozonation of tetracycline.

In this work, a Co-Ce@RM ozone catalyst was developed using red mud (RM), a by-product of alumina production, as a support material, and its preparation process, catalytic efficiency, and tetracycline (TCN) degradation mechanism were investigated. A comprehensive assessment was carried out using the 3E (environmental, economic, and energy) model. The optimal production conditions for Co-Ce@RM were as follows: The doping ratio of Co and Ce was 1:3, the calcination temperature was 400°C, and the calcination time was 5 h, achieving a maximum removal rate of 87.91% of TCN. The catalyst was characterized using different analytical techniques. Under the conditions of 0.4 L/min ozone aeration rate, with 9% catalyst loading and solution pH 9, the optimal removal rates and chemical oxygen demand by the Co-Ce catalytic ozonation at RM were 94.17% and 75.27%, respectively. Moreover, free radical quenching experiments showed that superoxide radicals (O2 -) and singlet oxygen (1O2) were the main active groups responsible for the degradation of TCN. When characterizing the water quality, it was assumed that TCN undergoes degradation pathways such as demethylation, dehydroxylation, double bond cleavage, and ring-opening reactions under the influence of various active substances. Finally, the 3E evaluation model was deployed to evaluate the Co-Ce@RM catalytic ozonation experiment of TCN wastewater. PRACTITIONER POINTS: The preparation of Co-Ce@RM provides new ideas for resource utilization of red mud. Catalytic ozonation by Co-Ce@RM can produce 1O2 active oxygen groups. The Co-Ce@RM catalyst can maintain a high catalytic activity after 20 cycles. The degradation pathway of the catalytic ozonation of tetracycline was fully analyzed. Catalytic ozone oxidation processes were evaluated by the "3E" (environmental, economic, and energy) model.

Strikingly Facile Cleavage of N-H/N-O Bonds Induced by Surface Frustrated Lewis Pair on CeO2(110) to Boost NO Reduction by NH3.

Ceria with surface solid frustrated Lewis pairs (FLPs), formed by regulating oxygen vacancies, demonstrate remarkable ability in activating small molecules. In this work, we extended the application of FLPs on CeO2(110) to the selective catalytic reduction of NO by NH3 (NH3-SCR), finding a notable enhancement in performance compared to ordinary CeO2(110). Additionally, an innovative approach involving H2 treatment was discovered to increase the number of FLPs, thereby further boosting the NH3-SCR efficiency. Typically, NH3-SCR on regular CeO2 follows the Eley-Rideal (E-R) mechanism. However, density functional theory (DFT) calculations revealed a significant reduction in the energy barriers for the activation of N-O and N-H bonds under the Langmuir-Hinshelwood (L-H) mechanism with FLPs present. This transition shifted the reaction mechanism from the E-R pathway on regular R-CeO2 to the L-H pathway on FLP-rich FR-CeO2, as corroborated by the experimental findings. The practical application of FLPs was realized by loading MoO3 onto FLP-rich FR-CeO2, leveraging the synergistic effects of acidic sites and FLPs. This study provides profound insights into how FLPs facilitate N-H/N-O bond activation in small molecules, such as NH3 and NO, offering a new paradigm for catalyst design based on catalytic mechanism research.

Modified Ce/Zr-MOF Nanoparticles Loaded with Curcumin for Alzheimer's Disease via Multifunctional Modulation.

Introduction: Alzheimer's disease (AD), a neurodegenerative condition, stands as the most prevalent form of dementia. Its complex pathological mechanisms and the formidable blood-brain barrier (BBB) pose significant challenges to current treatment approaches. Oxidative stress is recognized as a central factor in AD, underscoring the importance of antioxidative strategies in its treatment. In this study, we developed a novel brain-targeted nanoparticle, Ce/Zr-MOF@Cur-Lf, for AD therapy. Methods: Layer-by-layer self-assembly technology was used to prepare Ce/Zr-MOF@Cur-Lf. In addition, the effect on the intracellular reactive oxygen species level, the uptake effect by PC12 and bEnd.3 cells and the in vitro BBB permeation effect were investigated. Finally, the mouse AD model was established by intrahippocampal injection of Aß1-42, and the in vivo biodistribution, AD therapeutic effect and biosafety of the nanoparticles were researched at the animal level. Results: As anticipated, Ce/Zr-MOF@Cur-Lf demonstrated efficient BBB penetration and uptake by PC12 cells, leading to attenuation of H2O2-induced oxidative damage. Moreover, intravenous administration of Ce/Zr-MOF@Cur-Lf resulted in rapid brain access and improvement of various pathological features of AD, including neuronal damage, amyloid-ß deposition, dysregulated central cholinergic system, oxidative stress, and neuroinflammation. Conclusion: Overall, Ce/Zr-MOF@Cur-Lf represents a promising approach for precise brain targeting and multi-target mechanisms in AD therapy, potentially serving as a viable option for future clinical treatment.

A Ratiometric Fluorescence Assay for Detection of Ascorbic Acid Based on N,S Co-Doped Carbon Dots Combined With Ce4.

Hence, N,S-CDs with photoluminescent property were simply synthesized via a one-step hydrothermal method. Combined with the commercial reagent Ce4+, a ratiometric fluorescence assay for ascorbic acid (AA) detection was established. Ce4+, possessing oxidization, could directly oxidize o-phenylenediamine (OPD) to form the yellow fluorescent product oxOPD. Under the excitation wavelength of 370 nm, oxOPD had a maximum fluorescence emission at 562 nm. Meanwhile, due to the occurrence of the inner filter effect (IFE), oxOPD quenched the fluorescence of N,S-CDs. However, ascorbic acid (AA) inhibited the oxidation of Ce4+, causing the fluorescence of oxOPD at 562 nm to decrease, accompanied by an increase in the fluorescence belonging to N,S-CDs at 450 nm. Thus, a Ce4+-assisted ratiometric fluorescence method was established for AA detection. The two fluorescence output signals in this method had opposite changing trends, which could reduce system errors and improve the accuracy. This method was successfully applied to the determination of AA in drugs and fruits.

Cell-nanoparticle stickiness and dose delivery in a multi-model in silico platform: DosiGUI.

BACKGROUND: It is well-known that nanoparticles sediment, diffuse and aggregate when dispersed in a fluid. Once they approach a cell monolayer, depending on the affinity or "stickiness" between cells and nanoparticles, they may adsorb instantaneously, settle slowly - in a time- and concentration-dependent manner - or even encounter steric hindrance and rebound. Therefore, the dose perceived by cells in culture may not necessarily be that initially administered. Methods for quantifying delivered dose are difficult to implement, as they require precise characterization of nanoparticles and exposure scenarios, as well as complex mathematical operations to handle the equations governing the system dynamics. Here we present a pipeline and a graphical user interface, DosiGUI, for application to the accurate nano-dosimetry of engineered nanoparticles on cell monolayers, which also includes methods for determining the parameters characterising nanoparticle-cell stickiness. RESULTS: We evaluated the stickiness for 3 industrial nanoparticles (TiO2 - NM-105, CeO2 - NM-212 and BaSO4 - NM-220) administered to 3 cell lines (HepG2, A549 and Caco-2) and subsequently estimated corresponding delivered doses. Our results confirm that stickiness is a function of both nanoparticle and cell type, with the stickiest combination being BaSO4 and Caco-2 cells. The results also underline that accurate estimations of the delivered dose cannot prescind from a rigorous evaluation of the affinity between the cell type and nanoparticle under investigation. CONCLUSION: Accurate nanoparticle dose estimation in vitro is crucial for in vivo extrapolation, allowing for their safe use in medical and other applications. This study provides a computational platform - DosiGUI - for more reliable dose-response characterization. It also highlights the importance of cell-nanoparticle stickiness for better risk assessment of engineered nanomaterials.

Spectrofluorometric Turn-Off Sensing Probe for Tolmetin Determination Using Cerium and Nitrogen Codoped Carbon Dots.

A facile, low-cost, and rapid method was developed for spectrofluorometric determination of tolmetin (TOL) using highly fluorescent (QY = 35%) cerium and nitrogen codoped carbon dots (Ce-NCDs) sensing platform prepared by one-step hydrothermal method. Owing to the severe overlap between TOL absorption and Ce-NCDs excitation spectra around 320 nm, TOL could attenuate the emission of Ce-NCDs at 407 nm through primary inner filter effect (IFE). This concentration dependent attenuation was linear between 2 and 10 µg/mL (r = 0.9993) with a limit of detection of 0.5 µg/mL. The sensor showed very good accuracy (% recovery = 98%-100%) and precision (%RSD < 2). The developed sensing strategy was successfully applied for TOL detection as an active pharmaceutical ingredient in pharmaceutical formulation and as a potential pollutant in environmental water samples, such as tap and river water, with acceptable recovery and considerable selectivity. Thus, the direct single-step spectrofluorometric determination of TOL was enabled without extensive processing or chemical derivatization.