Toxicity Of Zinc Oxide And Cerium Oxide Nanoparticles To Mesquite

The impact of metal nanoparticles (NPs) in biological systems is still not well understood. Little is known about the response of plants, the first trophic level, to NP exposure; consequently, their possible role on the fate and transport of NPs in ecosystems is unknown. The aim of this research was to determine the response of mesquite (Prosopis juliflora-velutina), a native desert plant, to ZnO and CeO2 (nanoceria) NPs. Mesquite seedlings were grown for 15 days in hydroponics with of ZnO (10 nm) and CeO2 NPs (10 nm) at concentrations varying from 500 to 4000 mg L-1. In the present study, cerium and zinc concentrations as well as the concentration of some macro and micro elements in plant tissues were determined by inductively coupled plasma optical emission spectroscopy (ICP OES). Structural and morphological modification in tissues, deposition of Ce and Zn, and plant stress were examined by infra red microspectroscopy (IMS), electron probe micro-analyzer (EPMA), and specific activity of catalase (CAT) and ascorbate peroxidase (APOX), respectively. In addition, the biotransformation of CeO2 and ZnO NPs was determined by using x-ray absorption spectroscopy (XAS). Results showed that none of the NPs reduced plants growth. In addition, at all concentrations the nanoceria increased CAT and APOX in leaves, while ZnO NPs increased CAT in roots stems and leaves, while APOX was increased in stems and leaves. The ICP-OES data showed that mesquite plants differentially absorbed Zn and Ce from the NPs. In the case of Zn, the bioconcentration factors (metal in tissues/metal in medium) were 11, 4, 2, and 0.9 for the 500, 1000, 2000, and 4000 mg L-1 treatments, respectively. While for the nanoceria the bioconcentration factors were 53, 30, 26, 30, and 12 for the 500, 1000, 2000, and 4000 mg L-1 treatments, respectively. However, in all cases the translocation factors were higher for the ZnO NPs. ZnO NPs reduced the accumulation of some micronutrients, mainly in roots and in some cases in stems; but very few changes were observed in leaves. On the other hand, the nanoceria reduced the concentration of Cu, Mn, and Fe, but increased Mo concentration in roots. The IMS analysis of roots treated with the nanoceria at 4000 mg L-1 showed changes in the peaks associated with proteins (1150-1100 cm-1) and lipids (2900-2850 cm-1), whereas in the ZnO NPs treated plants, only the band of aromatic phenolic compounds (845 cm-1) showed changes. The EPMA analysis confirmed the presence of Zn in the vascular system of the ZnO NP treated plants, but the nanoceria treated plants showed Ce only in cortex and epidermis. However the x-ray mapping did not showed evidence of nanoceria agglomeration in the vascular tissue. The XAS study showed clear evidence of the presence of CeO2 NPs within tissues but ZnO NPs were not observed. The data also showed that at the concentration used and the growth stage studied, the nanoceria and ZnO NPs exerted low toxicity on mesquite, suggesting that this desert plant may display some resistance to both the nanoceria and ZnO NPs

Toxicity of zinc oxide and cerium oxide nanoparticles to mesquite (Prosopis juliflora-velutina)

The impact of metal nanoparticles (NPs) in biological systems is still not well understood. Little is known about the response of plants, the first trophic level, to NP exposure; consequently, their possible role on the fate and transport of NPs in ecosystems is unknown. The aim of this research was to determine the response of mesquite (Prosopis juliflora-velutina ), a native desert plant, to ZnO and CeO2 (nanoceria) NPs. Mesquite seedlings were grown for 15 days in hydroponics with of ZnO (10 nm) and CeO2 NPs (10 nm) at concentrations varying from 500 to 4000 mg L-1. In the present study, cerium and zinc concentrations as well as the concentration of some macro and micro elements in plant tissues were determined by inductively coupled plasma optical emission spectroscopy (ICP OES). Structural and morphological modification in tissues, deposition of Ce and Zn, and plant stress were examined by infra red microspectroscopy (IMS), electron probe micro-analyzer (EPMA), and specific activity of catalase (CAT) and ascorbate peroxidase (APOX), respectively. In addition, the biotransformation of CeO2 and ZnO NPs was determined by using x-ray absorption spectroscopy (XAS). Results showed that none of the NPs reduced plants growth. In addition, at all concentrations the nanoceria increased CAT and APOX in leaves, while ZnO NPs increased CAT in roots stems and leaves, while APOX was increased in stems and leaves. The ICP-OES data showed that mesquite plants differentially absorbed Zn and Ce from the NPs. In the case of Zn, the bioconcentration factors (metal in tissues/metal in medium) were 11, 4, 2, and 0.9 for the 500, 1000, 2000, and 4000 mg L-1 treatments, respectively. While for the nanoceria the bioconcentration factors were 53, 30, 26, 30, and 12 for the 500, 1000, 2000, and 4000 mg L-1 treatments, respectively. However, in all cases the translocation factors were higher for the ZnO NPs. ZnO NPs reduced the accumulation of some micronutrients, mainly in roots and in some cases in stems; but very few changes were observed in leaves. On the other hand, the nanoceria reduced the concentration of Cu, Mn, and Fe, but increased Mo concentration in roots. The IMS analysis of roots treated with the nanoceria at 4000 mg L-1 showed changes in the peaks associated with proteins (1150-1100 cm-1) and lipids (2900-2850 cm -1), whereas in the ZnO NPs treated plants, only the band of aromatic phenolic compounds (845 cm-1) showed changes. The EPMA analysis confirmed the presence of Zn in the vascular system of the ZnO NP treated plants, but the nanoceria treated plants showed Ce only in cortex and epidermis. However the x-ray mapping did not showed evidence of nanoceria agglomeration in the vascular tissue. The XAS study showed clear evidence of the presence of CeO2 NPs within tissues but ZnO NPs were not observed. The data also showed that at the concentration used and the growth stage studied, the nanoceria and ZnO NPs exerted low toxicity on mesquite, suggesting that this desert plant may display some resistance to both the nanoceria and ZnO NPs

Determination Of The Effects Of ZnO And CeO2 Nanoparticles In Mesquite (Prosopis Juliflora) And Soybean (Glycine Max): Synchrotron And Spectroscopic Approaches

The rapid growth of nanotechnology is exposing the environment to abnormal concentrations of engineered nanoparticles (NPs). There is concern about the unknown consequences of NPs on the environment and human health. This Dissertation has relied significantly on Synchrotron and other spectroscopic techniques to give insights on the effects, speciation and distribution of two metal oxide nanoparticles (ZnO, CeO2) on two plant species (Mesquite and Soybean). We evaluated the effects of ZnO (10 nm) and CeO2 (8 nm) NPs on a plant species native to the semi-arid regions of North America, Mesquite (Prosopis juliflora velutina). Mesquite plants grown in hydroponic culture with ZnO NPs presented an increased uptake of Zn when compared to control plants. Zn synchrotron μXRF from root transversal sections (30 μm) showed Zn accumulated mainly in the vascular region. Zn μXRF maps obtained from the leaves showed that Zn is mainly concentrated in the veins. Combined Bulk and μXANES synchrotron analysis showed that Zn has different coordination environments compared to the ZnO NPs, and corroborated that ZnO NPs were transformed on/in the root surface and transported as Zn (II) from roots to leaves. Exposure to ZnO NPs increased the specific activity of stress enzymes catalase in root, stem and leaves and ascorbate peroxidase only in stem and leaves. The concentration of Ce in mesquite plants exposed to CeO2 NPs was higher when compared to the control; however Ce μXRF maps showed most of the cerium was adsorbed in the root. Bulk XANES showed that Ce maintained the same coordination as the CeO2 NPs. Few reports thus far have addressed the entire life cycle of plants grown in NP-contaminated soil. We performed a lifecycle study of ZnO and CeO2 NPs with the fifth largest crop produced in the world and second in the USA, Soybean (Glycine max).We determined the effects of NPs exposure and the potential storage of NPs or their biotransformed products in edible/reproductive organs of the plants in order to study the possible transfer of NPs into the food chain and potentially into the next plant generation. Soybean (Glycine max) seeds were germinated and grown to full maturity in organic farm soil amended with either ZnO NPs or CeO2 NPs at different concentrations. At harvest, synchrotron μ-XRF and μ-XANES analyses were performed on soybean tissues, including pods, to determine the forms of Ce and Zn in NP-treated plants. The X-ray absorption spectroscopy studies showed no presence of ZnO NPs within tissues. However, μ-XANES data showed O-bound Zn, in a form resembling Zn-citrate, which could be an important Zn complex in the soybean grains. On the other hand, the synchrotron μ-XANES results showed that Ce remained mostly as CeO2 NPs within the plant. Our results also showed that a small percentage of Ce(IV), the oxidation state of Ce in CeO2 NPs, was biotransformed to Ce(III). Our results also showed that the plants exposed to CeO2 diminished in growth but most importantly, nitrogen fixation was stopped at higher exposure concentrations. To our knowledge, this is the first report on the presence and effects of CeO2 and Zn compounds in the reproductive/edible portion of the soybean plant grown in farm soil with CeO2 and ZnO NPs

Determination of the effects of ZnO and CeO2 nanoparticles in mesquite (Prosopis juliflora) and soybean (Glycine max): Synchrotron and spectroscopic studies

The rapid growth of nanotechnology is exposing the environment to abnormal concentrations of engineered nanoparticles (NPs). There is concern about the unknown consequences of NPs on the environment and human health. This dissertation has relied significantly on Synchrotron and other spectroscopic techniques to give insights on the effects, speciation and distribution of two metal oxide nanoparticles (ZnO, CeO2) on two plant species (Mesquite and Soybean). We evaluated the effects of ZnO (10 nm) and CeO2 (8 nm) NPs on a plant species native to the semi-arid regions of North America, Mesquite (Prosopis juliflora velutina). Mesquite plants grown in hydroponic culture with ZnO NPs presented an increased uptake of Zn when compared to control plants. Zn synchrotron μXRF from root transversal sections (30 μm) showed Zn accumulated mainly in the vascular region. Zn μXRF maps obtained from the leaves showed that Zn is mainly concentrated in the veins. Combined Bulk and μXANES synchrotron analysis showed that Zn has different coordination environments compared to the ZnO NPs, and corroborated that ZnO NPs were transformed on/in the root surface and transported as Zn (II) from roots to leaves. Exposure to ZnO NPs increased the specific activity of stress enzymes catalase in root, stem and leaves and ascorbate peroxidase only in stem and leaves. The concentration of Ce in mesquite plants exposed to CeO2 NPs was higher when compared to the control; however Ce μXRF maps showed most of the cerium was adsorbed in the root. Bulk XANES showed that Ce maintained the same coordination as the CeO2 NPs. Few reports thus far have addressed the entire life cycle of plants grown in NP-contaminated soil. We performed a lifecycle study of ZnO and CeO 2 NPs with the fifth largest crop produced in the world and second in the USA, Soybean (Glycine max).We determined the effects of NPs exposure and the potential storage of NPs or their biotransformed products in edible/reproductive organs of the plants in order to study the possible transfer of NPs into the food chain and potentially into the next plant generation. Soybean (Glycine max) seeds were germinated and grown to full maturity in organic farm soil amended with either ZnO NPs or CeO2 NPs at different concentrations. At harvest, synchrotron μ-XRF and μ-XANES analyses were performed on soybean tissues, including pods, to determine the forms of Ce and Zn in NP-treated plants. The X-ray absorption spectroscopy studies showed no presence of ZnO NPs within tissues. However, μ-XANES data showed O-bound Zn, in a form resembling Zn-citrate, which could be an important Zn complex in the soybean grains. On the other hand, the synchrotron μ-XANES results showed that Ce remained mostly as CeO2 NPs within the plant. Our results also showed that a small percentage of Ce(IV), the oxidation state of Ce in CeO2 NPs, was biotransformed to Ce(III). Our results also showed that the plants exposed to CeO2 diminished in growth but most importantly, nitrogen fixation was stopped at higher exposure concentrations. To our knowledge, this is the first report on the presence and effects of CeO2 and Zn compounds in the reproductive/edible portion of the soybean plant grown in farm soil with CeO2 and ZnO NPs

Zno Nanoparticle Fate In Soil And Zinc Bioaccumulation In Corn Plants (Zea Mays) Influenced By Alginate

Nanoparticles (NPs) can interact with naturally occurring inorganic and organic substances in soils, which may change their transport behavior in soil and plants. This study was performed in two steps. In the first step, corn (Zea mays) plants were cultivated for one month in soil amended with 10 nm commercial spheroid ZnO NPs at 0–800 mg kg−1 and sodium alginate at 10 mg kg−1. In the second step, the plants were grown with ZnO NPs at 400 mg kg−1 and alginate at 0, 10, 50, and 100 mg kg−1. The dynamics of Zn concentrations in soil solution and Zn accumulation in plant tissues were determined by ICP-OES. Biomass accumulation, chlorophyll concentration, and the activity of antioxidant enzymes in leaves were also quantified. Results indicate that ZnO NPs coexisting with Zn dissolved species were continuously released to the soil solution to replenish the Zn ions or ZnO NPs scavenged by roots. At 400 and 800 mg kg−1, without alginate, ZnO NPs significantly reduced the root and shoot biomass production; however, plants treated with these NP concentrations, plus alginate, had significantly more Zn in tissues with no reduction in biomass production. Alginate significantly reduced the activity of stress enzymes catalase and peroxidase, which could indicate damage in the defense system. The effects of ZnO NPs in a food crop grown in alginate enriched soil, showing an excess of Zn in the aerial parts, are yet to be reported

Toxicity Assessment of Cerium Oxide Nanoparticles in Cilantro (<i>Coriandrum sativum</i> L.) Plants Grown in Organic Soil

Studies have shown that CeO₂ nanoparticles (NPs) can be accumulated in plants without modification, which could pose a threat for human health. In this research, cilantro (<i>Coriandrum sativum</i> L.) plants were germinated and grown for 30 days in soil amended with 0 to 500 mg kg^–1 CeO₂ NPs and analyzed by spectroscopic techniques and biochemical assays. At 125 mg kg^–1, plants produced longer roots (<i>p</i> ≤ 0.05), and at 500 mg kg^–1, there was higher Ce accumulation in tissues (<i>p</i> ≤ 0.05). At 125 mg, catalase activity significantly increased in shoots and ascorbate peroxidase in roots (<i>p</i> ≤ 0.05). The FTIR analyses revealed that at 125 mg kg^–1 the CeO₂ NPs changed the chemical environment of carbohydrates in cilantro shoots, for which changes in the area of the stretching frequencies were observed. This suggests that the CeO₂ NPs could change the nutritional properties of cilantro