EGCG suppresses PD-1 expression of T cells via inhibiting NF-κB phosphorylation and nuclear translocation.

Epigallocatechin-3-gallate (EGCG) is an important tea polyphenol with anti-tumor potential. Our previous studies revealed that EGCG was a promising immune checkpoint inhibitor (ICI) as it could downregulate expression of programmed cell death 1 ligand 1 (PD-L1) in tumor cells, thereby resulting tumor killing effect. In particular, EGCG can effectively avoid the inflammatory storm caused by anti-tumor therapy, which is a healthy green capacity absent from many ICIs. However, the relationship between EGCG and programmed cell death 1 (PD-1) of T cells remains unclear. In this work, we explored the effect of EGCG on T cells and found that EGCG suppressed PD-1 via inhibiting NF-κB phosphorylation and nuclear translocation. Furtherly, the capability of EGCG was confirmed in tumor-bearing mice to inhibit PD-1 expression in T cells and enhance apoptosis in tumor cells. These results implied that EGCG could inhibit the expression of PD-1 in T cells, thereby promoting anti-tumor effects of T cells. EGCG will be a promising candidate in anti-tumor therapy.

Strengthening the Combinational Immunotherapy from Modulating the Tumor Inflammatory Environment via Hypoxia-Responsive Nanogels.

Despite the success of immuno-oncology in clinical settings, the therapeutic efficacy is lower than the expectation due to the immunosuppressive inflammatory tumor microenvironment (TME) and the lack of functional lymphocytes caused by exhaustion. To enhance the efficacy of immuno-oncotherapy, a synergistic strategy should be used that can effectively improve the inflammatory TME and increase the tumor infiltration of cytotoxic T lymphocytes (CTLs). Herein, a TME hypoxia-responsive nanogel (NG) is developed to enhance the delivery and penetration of diacerein and (-)-epigallocatechin gallate (EGCG) in tumors. After systemic administration, diacerein effectively improves the tumor immunosuppressive condition through a reduction of MDSCs and Tregs in TME, and induces tumor cell apoptosis via the inhibition of IL-6/STAT3 signal pathway, realizing a strong antitumor effect. Additionally, EGCG can effectively inhibit the expression of PD-L1, restoring the tumor-killing function of CTLs. The infiltration of CTLs increases at the tumor site with activation of systemic immunity after the combination of TIM3 blockade therapy, ultimately resulting in a strong antitumor immune response. This study provides valuable insights for future research on eliciting effective antitumor immunity by suppressing adverse tumor inflammation. The feasible strategy proposed in this work may solve the urgent clinical concerns of the dissatisfactory checkpoint-based immuno-oncotherapy.

Particulate Standard Establishment for Absolute Quantification of Nanoparticles by LA-ICP-MS.

The development of nanotechnology has transformed many cutting-edge studies related to single-molecule analysis into nanoparticle (NP) detection with a single-NP sensitivity and ultrahigh resolution. While laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has been successful in quantifying and tracking NPs, its quantitative calibration remains a major challenge due to the lack of suitable standards and the uncertain matrix effects. Herein, we frame a new approach to prepare quantitative standards via precise synthesis of NPs, nanoscale characterization, on-demand NP distribution, and deep learning-assisted NP counting. Gold NP standards were prepared to cover the mass range from sub-femtogram to picogram levels with sufficient accuracy and precision, thus establishing an unambiguous relationship between the sampled NP number in each ablation and the corresponding mass spectral signal. Our strategy facilitated for the first time the study of the factors affecting particulate sample capture and signal transductions in LA-ICP-MS analysis and culminated in the development of an LA-ICP-MS-based method for absolute NP quantification with single-NP sensitivity and single-cell quantification capability. The achievements would herald the emergence of new frontiers cut across a spectrum of toxicological and diagnostic issues related to NP quantification.

The importance of the IL-1 family of cytokines in nanoimmunosafety and nanotoxicology.

Engineered nanomaterials (ENMs) to which humans are exposed intentionally as nanomedicines or unintentionally as invaders, may elicit unforeseen immune reactions. An uncontrollable ENM-induced immune response poses a potential danger to the human body. During an immunological reaction, interleukin (IL)-1 family cytokines, which play key roles under both physiological and pathological conditions, can be secreted by various types of cells into the surrounding environment to induce a series of defensive reactions. However, the crucial roles played by IL-1 family cytokines in ENM-induced immunological responses have not attracted enough attention from researchers to date. In this review, ENM-mediated inflammatory responses and immunotoxicity are discussed, with the main focus directed to IL-1 family cytokines, including IL-1α, IL-1ß, IL-1Ra, IL-18, IL-33, IL-36, IL-37, and IL-38. The potential molecular mechanisms of IL-1 family cytokine activity triggered by ENMs, particularly the activation of IL-1α, IL-1ß, IL-18, and IL-33, are also reviewed. The understanding of IL-1 family cytokines on nanoimmunosafety provides a fundamental basis for designing safe ENMs that can potentially be used for nanomedicine. This article is categorized under: Toxicology and Regulatory Issues in Nanomedicine > Toxicology of Nanomaterials.

[Effects of water limiting and nitrogen reduction on nitrogen use and apparent balance of winter wheat in the Guanzhong Plain, Northwest China]. / é™æ°´å‡æ°®å¯¹å ³ä¸­å¹³åŽŸå†¬å°éº¦æ°®ç´ åˆ©ç”¨å’Œæ°®ç´ è¡¨è§‚å¹³è¡¡çš„å½±å“.

Effects of water limiting and nitrogen reduction on yield, nitrogen use efficiency and nitrogen apparent balance of wheat were investigated to explore whether it would be feasible to restrict water and reduce nitrogen in wheat production of the Guanzhong Plain and thus to provide scientific supports for yield-stable, high-efficiency, and environment-friendly developments in the irrigated production of winter wheat. Following a split-plot design with two water regimes as the main plots and four N addition rates as sub-plot factors, a field experiment (2017-2019) was conducted in Yangling, Shaanxi. The two water regimes were conventionally irrigating at the rate of 60 mm during the overwinter period and at the jointing stage, respectively (W2, a conventional practice) and irrigating at a rate of 60 mm during the overwintering period (W1, a restrictive irrigation practice). The four nitrogen addition rates were 300 kg·hm-2(N300, a conventional N rate), 225 kg·hm-2 (N225, a nitrogen rate of 25% less than the convention), 150 kg·hm-2(N150, a nitrogen rate 50% of less than the convention), and 0 kg·hm-2(N0, no nitrogen applied). The decreased irrigation rate and nitrogen rate significantly increased nitrogen content in the plants and grains, yield, N output, nitrogen use efficiency, nitrogen harvest index, nitrogen recovery efficiency, and nitrogen agronomic efficiency, reduced nitrate leaching and N surpluses, and maintained nitrogen balance. With both W1 and N150 adopted, the increased irrigation rate and nitrogen rate did not affect yield and N output of winter wheat in 2017-2019. Plant nitrogen content with both W1 and N150 adopted increased by 0.1%-25.5% and 14.0%-31.6% and the grain nitrogen content increased by 0.1% and 4.6%, compared with those with both W2 and N300 adopted in 2017-2018 and 2018-2019, respectively. Nitrogen use efficiency, nitrogen harvest index, nitrogen recovery efficiency, and nitrogen agronomic efficiency were averagely increased by 95.3%, 4.2%, 81.7% and 33.0% respectively. The N surplus was decreased by 97.2% and 95.1%, which effectively alleviated soil nitrate leaching. Considering all the indicators, irrigating at 600 m3·hm-2 during the overwintering period plus applying nitrogen at 150 kg·hm-2 could achieve high yield, high efficiency, and environment friendly development of winter wheat in the Guanzhong Plain of Shaanxi.

Dissolution and Retention Process of CeO2 Nanoparticles in Soil with Dynamic Redox Conditions.

The time-course association of soil physicochemical properties and fate of CeO2 nanoparticles (NPs) is not well understood. This study for the first time investigated the dissolution and retention of CeO2 NPs (<25 nm) during soil short-term (6 h) and long-term (30 d) aging processes with dynamic redox conditions. Under the additional reductant-induced initial reductive condition, theoretically, up to 220‰ of Ce(IV) was temporarily reductively dissolved within 10 min, accompanied by a slow retention process (180 min) of Ce species in soil solutions. Conversely, the dissolution and slow retention of Ce species were not significant in soil solutions without added reductant. X-ray absorption near edge spectroscopy (XANES) shows that most of Ce species were present as Ce(IV) (94.0%-97.8%) in all soils after a long-term aging process. These results indicate that the soil dynamic redox conditions induced by oxidant/reductant intrinsically determined the different time-course dissolution and retention of CeO2 NPs, highlighting the occasional reductive condition in soil solution that may contribute to the migration and diffusion of Ce species. The time-course study should be also adopted to develop a comprehensive understanding of the nano-soil interactions.

Comparative toxicity of rod-shaped nano-CeO2 and nano-CePO4 to lettuce.

The influence of morphology on the biological effects of nanomaterials (NMs) has not been well understood. In the present study, we compared the phytotoxicity of rod-shaped nano-cerium dioxide (R-CeO2) and nano-cerium phosphate (R-CePO4) to lettuce plants. The results showed that R-CeO2 significantly inhibited the root elongation of lettuce, induced oxidative damages, and caused cell death, while R-CePO4 was nontoxic to lettuce. The different distribution and speciation of Ce in plant tissues were determined by transmission electron microscopy (TEM) and X-ray absorption near edge spectroscopy (XANES) combined with linear combination fitting (LCF). The results showed that in the R-CeO2 group, part of Ce was transformed from Ce(IV) to Ce(III), while only Ce(III) was present in the R-CePO4 group. When interacting with plants, R-CeO2 is easier to be dissolved and transformed than R-CePO4, which might be the reason for their different phytotoxicity. Although both are Ce-based NMs and have the same morphology, the toxicity of R-CeO2 seems to come from the released Ce3+ ions rather than its shape. This research emphasizes the importance of chemical composition and reactivity of NMs to their toxicological effects.

Nanoparticles Determination by Laser Ablation Inductively Coupled Plasma Mass Spectrometry.

Quantitatively studying the biodistribution and transformation of nanomaterials is of great importance for nanotoxicological evaluation. Recently, laser ablation inductively coupled plasma mass spectrometry has been employed to distinguish nanoparticles (NPs) with their dissolved ions in biological samples. The principle of the proposal is based on a hypothesis that the intact NPs sampled by laser ablation will generate discrete sharp pulses of signals in ICP-MS measurement, being totally different from the continuous, relatively lower signals generated by ions. However, it is still a controversy whether NPs could maintain their intactness during the laser ablation. This work found a way to exactly determine the number of NPs sampled for each LA-ICP-MS measurement. It made possible to reveal the signal profile of a single NP in LA-ICP-MS analysis. The results suggest that AuNR, AgNP and TIO2 NP were broken into much smaller secondary NPs during the laser ablation, therefore generating continuous signals in the analyzer. There was a certain probability that the fragmentation of large-sized NP or multiple NPs by laser ablation was not sufficient, leaving some NPs unbroken or some secondary NPs with relatively large sizes to generate discrete pulses of signals in the analyzer. When the intactness of NPs during laser ablation cannot be assured, it is impossible to determine the attribution of mass spectrum signals. These findings compromise the reliability of distinguishing NPs from their dissolved ions by LA-ICP-MS.

Effects of ceria nanoparticles and CeCl3 on growth, physiological and biochemical parameters of corn (Zea mays) plants grown in soil.

The release of toxic ions from metal-based nanoparticles (NPs) may play an important role in biological effects of NPs. In this life cycle study, physiological and biochemical responses of soil-grown corn (Zea mays) plants exposed to ceria NPs and its ionic counterparts Ce3+ ions at 0, 25, 75 and 225 mg Ce/kg were investigated. Both treatments tended to reduce the fresh weight and height of the plants at 28 days after sowing (DAS), and delay silk appearance and finally decrease fruit weight at harvest. Uptake and distribution of some mineral nutrients, Ca, P, Fe, B, Zn and Mn in the plants were disturbed. None of the treatments significantly affected activities of antioxidant enzymes and MDA contents in the roots and leaves at 28 DAS. At 90 DAS, ceria NPs and Ce3+ ions disturbed the homeostasis of antioxidative systems in the plants, Ce3+ ions at all concentrations provoked significant oxidative damage in the roots and significantly increased MDA levels as compare to the control. The results indicate that the effects of ceria NPs and Ce3+ ions on corn plants varied with different growth stages and ceria NPs had similar but less severe impacts than Ce3+ ions. Speciation analysis revealed there was mutual transformation between CeO2 and Ce3+ in the soil-plant system. It is speculated that Ce3+ ions play a key role in toxicity. To the authors' knowledge, this is the first report of a life cycle study on comparative toxicity of CeO2 NPs and Ce3+ ions on corn plants.

Effects of Ceria Nanoparticles and CeCl3 on Plant Growth, Biological and Physiological Parameters, and Nutritional Value of Soil Grown Common Bean (Phaseolus vulgaris).

The release of metal ions may play an important role in toxicity of metal-based nanoparticles. In this report, a life cycle study is carried out in a greenhouse, to compare the effects of ceria nanoparticles (NPs) and Ce3+ ions at 0, 50, 100, and 200 mg Ce kg-1 on plant growth, biological and physiological parameters, and nutritional value of soil-grown common bean plants. Ceria NPs have a tendency to negatively affect photosynthesis, but the effect is not statistically significant. Ce3+ ionic treatments at 50, 100, and 200 mg Ce kg-1 result in increases of 1.25-, 0.66-, and 1.20-fold in stomatal conductance, respectively, relative to control plants. Both ceria NPs and Ce3+ ions disturb the homeostasis of antioxidant defense system in the plants, but only 200 mg Ce kg-1 ceria NPs significantly induce lipid peroxidation in the roots. Ceria NP treatments tend to reduced fresh weight and to increase mineral contents of the green pods, but have no effect on the organic nutrient contents. On the contrary, Ce3+ ion treatments modify the organic compositions and thus alter the nutritional quality and flavor of the green pods. These results suggest that the two Ce forms may have different mechanisms on common bean plants.

Graphene Oxide-Induced pH Alteration, Iron Overload, and Subsequent Oxidative Damage in Rice (Oryza sativa L.): A New Mechanism of Nanomaterial Phytotoxicity.

The mechanism of graphene-based nanomaterial (GBM)-induced phytotoxicity and its association with the GBM physicochemical properties are not yet fully understood. The present study compared the effects of graphene oxide (GO) and reduced GO (rGO) on rice seedling growth under hydroponic conditions for 3 weeks. GO at 100 and 250 mg/L reduced shoot biomass (by 25 and 34%, respectively) and shoot elongation (by 17 and 43%, respectively) and caused oxidative damage, while rGO exhibited no overt effect except for the enhancement of the antioxidant enzyme activities, suggesting that the surface oxygen content is a critical factor affecting the biological impacts of GBMs. GO treatments (100 and 250 mg/L) enhanced the iron (Fe) translocation and caused excessive Fe accumulation in shoots (2.2 and 3.6 times higher than control), which was found to be the main reason for the oxidative damage in shoots. GO-induced acidification of the nutrient solution was the main driver for the Fe overload in plants. In addition to the antioxidant regulators, the plants triggered other pathways to defend against the Fe toxicity via downregulation of the Fe transport associated metabolites (mainly coumarins and flavonoids). Plant root exudates facilitated the reduction of toxic GO to nontoxic rGO, acting as another route for plant adaption to GO-induced phytotoxicity. This study provides new insights into the mechanism of the phytotoxicity of GBMs. It also provides implications for the agricultural application of GBM that the impacts of GBMs on the uptake of multiple nutrients in plants should be assessed simultaneously and reduced forms of GBMs are preferential to avoid toxicity.

[Effects of reduced nitrogen application on yield, nitrogen utilization of spring maize and soil nitrate content in Weibei dryland, Northwest China]. / å‡é‡æ–½æ°®å¯¹æ¸­åŒ—æ—±åœ°æ˜¥çŽ‰ç±³äº§é‡ã€æ°®ç´ åˆ©ç”¨åŠåœŸå£¤ç¡æ€æ°®å«é‡çš„å½±å“.

To get a scientific pattern for nitrogen-reducing and efficiency-increasing production of spring maize in Weibei dryland, we conducted an in-situ field experiment of spring maize (Zhengdan 958 and Shaandan 8806) under dryland farming from 2016 to 2019 in Heyang County, located in Weibei dryland of Shaanxi. There were five nitrogen (N) treatments, including 360 kg·hm-2(N360, a rate commonly adopted by local farm households), 270 kg·hm-2(N270), 150-180 kg·hm-2(N150-180), 75-90 kg·hm-2(N75-90) and 0 kg·hm-2(N0). We investigated the effects of reduced nitrogen application on maize yield, nitrogen uptake and utilization of spring maize and soil nitrate residue. The results showed that: 1) Maize yield of both varieties at N150-180 was increased by 0.9%-7.1% and nitrogen uptake was decreased by 4.1%-4.6%, while average reco-very efficiency, partial-factor productivity and agronomic efficiency of N at N150-180 were increased by 79.3%-83.6%, 105.9%-157.7%, and 101.9%-114.1% compared with those at N360, respectively. 2) The contents of residual nitrate increased significantly when nitrogen application rate was more than 180 kg·hm-2, while nitrogen uptake was significantly reduced under rainfall shortage, and thus resulted in increasing soil residual nitrogen. After four-year treatments, the residual nitrate was up to 504.7-620.8 kg·hm-2 in 0-200 cm soil layer, with a peak in 80-140 cm soil layer. There was a risk of nitrate leaching. According to the comprehensive evaluation for annual yield, nitrogen use efficiency and soil nitrate residue, the optimum N application rate was recommended to be 150-180 kg N·hm-2 for spring maize in Weibei dryland.

Effects of foliar applications of ceria nanoparticles and CeCl3 on common bean (Phaseolus vulgaris).

In this study, comparative effects of foliar application of ceria nanoparticles (NPs) and Ce3+ ions on common bean plants were investigated. Soil grown bean seedlings were exposed to ceria NPs and Ce3+ ions at 0, 40, 80, and 160 mg Ce·L-1 every other day at the vegetative growth stage for 17 d. The plants were harvested 47 d after the last treatment. Performed analyses involved growth, physiological and biochemical parameters of the plants and nutritional quality of the pods. Ceria NPs at 40 mg Ce·L-1 increased dry weight of the plants by 51.8% over the control. Neither ceria NPs nor Ce3+ ions significantly affected other vegetative growth parameters. Pod yields and nutrient contents except for several mineral elements were also not significantly different among groups. Compared to control, pods from ceria NPs at 80 mg Ce·L-1 had significantly less S and Mn. At 40 and 80 mg Ce·L-1, ceria NPs reduced pod Mo by 27% and 21%, while Ce3+ ions elevated Mo contents by 20% and 18%, respectively, compared with control. Ce3+ ions at 80 and 160 mg Ce·L-1 significantly increased pod Zn by 25% and 120%, respectively, compared with control. At the end of the experiment, Ce3+ ions at 40, 80, and 160 mg Ce·L-1 increased contents of malondialdehyde (MDA) by 46%, 65%, and 82% respectively as compared with control. While ceria NPs led to a significant increase of MDA level only at the highest concentration. X-ray absorption near edge structure (XANES) analysis of the leaf samples revealed that both ceria NPs and Ce3+ ions kept their original chemical species after foliar applications, suggesting the observed effects of ceria NPs and Ce3+ ions on the plants were probably due to their nano-specific properties and ionic properties respectively.

Influence of Surface Charge on the Phytotoxicity, Transformation, and Translocation of CeO2 Nanoparticles in Cucumber Plants.

The physiochemical properties of nanoparticles (NPs), including surface charge, will affect their uptake, transformation, translocation, and final fate in the environment. In this study, we compared the phytoxoxicity and transport behaviors of nano CeO2 (nCeO2) functionalized with positively charged (Cs-nCeO2) and negatively charged (PAA-nCeO2) coatings. Cucumber seedlings were hydroponically exposed to 0-1000 mg/L of Cs-nCeO2 and PAA-nCeO2 for 14 days and the contents, distribution, translocation, and transformation of Ce in plants were analyzed using inductively coupled plasma mass spectrometry, micro X-ray fluorescence (µ-XRF), and X-ray absorption near-edge spectroscopy (XANES), respectively. Results showed that the seedling growth and Ce contents in plant tissues were functions of exposure concentrations and surface charge. Cs-nCeO2 was adsorbed strongly on a negatively charged root surface, which led to significantly higher Ce contents in the roots and lower translocation factors of Ce from the roots to shoots in Cs-nCeO2 group than in PAA-nCeO2 group. The results of µ-XRF showed that Ce elements were mainly accumulated at the root tips and lateral roots, as well as in the veins and at the edge of leaves. XANES results revealed that the proportion of Ce(III) was comparable in the plant tissues of the two groups. We speculated that Cs-nCeO2 and PAA-nCeO2 were partially dissolved under the effect of root exudates, releasing Ce3+ ions as a result. Then, the Ce3+ ions were transported upward in the form of Ce(III) complexes along the vascular bundles and eventually accumulated in the veins. The other portion of Cs-nCeO2 and PAA-nCeO2 entered the roots through the gap of a Casparian strip at root tips/lateral roots and was transported upward as intact NPs and finally accumulated at the edge of the blade. This study will greatly advance our information on how the properties of NPs influence their phytotoxicity, uptake, and subsequent trophic transfer in terrestrial food webs.

Comparative study of core- and surface-radiolabeling strategies for the assembly of iron oxide nanoparticle-based theranostic nanocomposites.

This work highlights the superiority of the surface-radiolabeling strategy over the core-labeling strategy in the assembly of radioactive iron oxide nanoparticle (IONP)-based nanocomposites for use in multimodal imaging and targeted therapy. It also implies a possible overestimation of the labeling stability in previous studies and points out directions for further optimization.

Trophic Transfer and Transformation of CeO2 Nanoparticles along a Terrestrial Food Chain: Influence of Exposure Routes.

The trophic transfer and transformation of CeO2 nanoparticles (NPs) through a simulated terrestrial food chain were investigated using a radiotracer technique and X-ray absorption near edge structure (XANES). Radioactive 141CeO2 NPs were applied to head lettuce ( Lactuca sativa), treated via root exposure in its potting soil (5.5 or 11 mg/plant) for 30 days or foliar exposure (7.2 mg/plant, with half of the leaves treated and the other half not) for 7 days. Subsequently, two groups of land snails ( Achatina fulica) were exposed to 141Ce via either a direct (i.e., feeding on the lettuce leaves with 141Ce-contaminated surfaces) or an indirect/trophic (i.e., feeding on the lettuce leaves with systemically distributed 141Ce) route. To evaluate the influence of exposure routes, the Ce contents of the lettuce, snail tissues, and feces were determined by radioactivity measurements. The results show that both assimilation efficiencies (AEs) and food ingestion rates of Ce are greater for the trophic (indirect) exposure. The low AEs indicate that the CeO2 NPs ingested by snails were mostly excreted subsequently, and those that remained in the body were mainly concentrated in the digestive gland. XANES analysis shows that >85% of Ce was reduced to Ce(III) in the digestive gland under direct exposure, whereas Ce in the rest of the food chain (including feces) was largely in its original oxidized (IV) state. This study suggests that CeO2 NPs present in the environment may be taken up by producers and transferred to consumers along food chains and trophic transfer may affect food safety.

Xylem and Phloem Based Transport of CeO2 Nanoparticles in Hydroponic Cucumber Plants.

Uptake and translocation of manufactured nanoparticles (NPs) in plants have drawn much attention due to their potential toxicity to the environment, including food webs. In this paper, the xylem and phloem based transport of CeO2 NPs in hydroponic cucumber plants was investigated using a split-root system. One half of the root system was treated with 200 or 2000 mg/L of CeO2 NPs for 3 days, whereas the other half remained untreated, with both halves sharing the same aerial part. The quantitative distribution and speciation of Ce in different plant tissues and xylem sap were analyzed by inductively coupled plasma-mass spectrometry, transmission electron microscope, X-ray absorption near edge structure, and X-ray fluorescence. Results show that about 15% of Ce was reduced from Ce(IV) to Ce(III) in the roots of the treated-side (TS), while almost all of Ce remained Ce(IV) in the blank-side (BS). The detection of CeO2 or its transformation products in the xylem sap, shoots, and BS roots indicates that Ce was transported as a mixture of Ce(IV) and Ce(III) from roots to shoots through xylem, while it was transported almost only in the form of CeO2 from shoots back to roots through phloem. To our knowledge, this is the first report of root-to-shoot-to-root redistribution after transformation of CeO2 NPs in plants, which has significant implications for food safety and human health.

Influence of phosphate on phytotoxicity of ceria nanoparticles in an agar medium.

Fate and toxicity of manufactured nanoparticles (NPs) in the living organisms and the environment are highly related to their transformation. In the present study, the effect of phosphate on the phytotoxicity and transformation of CeO2 NPs was investigated in an agar medium using head lettuce plants that are sensitive to Ce3+ ions. Plants were treated by CeO2 NPs with or without phosphate for 10 days. Results suggest that the treatments of P deficiency (P(-)) and CeO2 NPs (P(+)&Ce) could separately induce significant inhibition on the growth of lettuce seedlings and cause oxidative stress, but the inhibition was the most serious when the two conditions were combined (P(-)&Ce). In the absence of phosphate, more CeO2 NPs were transformed to Ce(III) in the roots and more Ce3+ ions were translocated to the shoots, which induced higher toxicity to head lettuce. Phosphates could alleviate the phytotoxic effect of CeO2 NPs through the precipitation of dissociated Ce3+ ions. Considering the wide existence of phosphate in the environment, phosphate-related transformation may be a critical factor in evaluating the toxicity and fate of many other metal-based NPs.

Response difference of transgenic and conventional rice (Oryza sativa) to nanoparticles (γFe2O3).

Nanoparticles (NPs) are an increasingly common contaminant in agro-environments, and their potential effect on genetically modified (GM) crops has been largely unexplored. GM crop exposure to NPs is likely to increase as both technologies develop. To better understand the implications of nanoparticles on GM plants in agriculture, we performed a glasshouse study to quantify the uptake of Fe2O3 NPs on transgenic and non-transgenic rice plants. We measured nutrient concentrations, biomass, enzyme activity, and the concentration of two phytohormones, abscisic acid (ABA) and indole-3-acetic acid (IAA), and malondialdehyde (MDA). Root phytohormone inhibition was positively correlated with Fe2O3 NP concentrations, indicating that Fe2O3 had a significant influence on the production of these hormones. The activities of antioxidant enzymes were significantly higher as a factor of low Fe2O3 NP treatment concentration and significantly lower at high NP concentrations, but only among transgenic plants. There was also a positive correlation between the treatment concentration of Fe2O3 and iron accumulation, and the magnitude of this effect was greatest among non-transgenic plants. The differences in root phytohormone production and antioxidant enzyme activity between transgenic and non-transgenic rice plants in vivo suggests that GM crops may react to NP exposure differently than conventional crops. It is the first study of NPs that may have an impact on GM crops, and a realistic significance for food security and food safety.

Nonlinear absorption, nonlinear scattering, and optical limiting properties of MoS2-ZnO composite-based organic glasses.

MoS2-ZnO composites were synthesized using a solution-based method. The scanning electron microscopy and transmission electron microscopy analysis demonstrated that ZnO nanoparticles with a size of about 4.5 nm were coated on the basal surface of MoS2 nanosheets with an expanded spacing of the (002) plane. The MoS2-ZnO composite-based poly(methyl methacrylate) (PMMA) organic glasses (MoS2-ZnO-PMMA organic glasses) were prepared through a polymerization process. The nonlinear absorption (NLA), nonlinear scattering (NLS), and optical limiting (OL) properties of the MoS2-ZnO-PMMA organic glasses with different amounts of MoS2-ZnO were investigated using a modified Z-scan technique. Compared to MoS2-PMMA and ZnO-PMMA organic glasses, the MoS2-ZnO-PMMA organic glasses exhibited enhanced NLA, NLS, and OL properties, which were attributed to the interfacial charge transfer between MoS2 nanosheets and ZnO nanoparticles, the layered structure of MoS2 nanosheets, the small size effect of ZnO nanoparticles, and the local field effect. In addition, a changeover from saturable absorption (SA) to reverse saturable absorption (RSA) could be realized in the MoS2-ZnO-PMMA organic glasses by adjusting the input energy. The total nonlinear extinction coefficient and response time of the MoS2-ZnO-PMMA organic glasses could be up to 2380 cm GW(-1) and several hundred picoseconds, respectively. Compared to the MoS2 films, the MoS2-ZnO-PMMA organic glasses have higher optical damage threshold, better mechanical strength and flexibility. Thus the MoS2-ZnO-PMMA organic glasses are very promising for optical devices such as optical limiters, optical shutters, ultrafast lasers, and ultrafast optical switches.