Plant-based green synthesis of metallic nanoparticles: scientific curiosity or a realistic alternative to chemical synthesis?

Currently, thousands of tons of metallic nanoparticles (MNPs) are produced and utilized in nano-enabled devises, personal care, medicinal, food and agricultural products. It is generally accepted that the reaction compounds and the techniques used in industrial production of MNPs are not environmentally friendly. The green synthesis has been proposed as an alternative to reduce the use of hazardous compounds and harsh reaction conditions in the production of MNPs. In this endeavor, investigators have used organic compounds, microbes, plants and plant-derived materials as reducing agents. Research papers are published every year, and each one of them stresses the benefits of the green approach and the advantages over the traditional syntheses. However, after almost two decades since the explosion of the reports about the new approach, the commercial production of green-synthesized nanoparticles does not seem to find a way to scale up commercial production. This review includes descriptions of the traditional and green synthesis and applications of MNPs and highlights the factors limiting the use of plant-based synthesis as a real alternative to the traditional synthesis of MNPs

Impacts of Copper Oxide Nanoparticles in Bell Pepper (\u3ci\u3eCapsicum annum\u3c/i\u3e L.) Plants: A Full Life Cycle Study

Several studies have explored the effects of copper nanoparticles (NPs) on different edible plants. However, no studies on bell pepper (Capsicum annum L.) plants have been reported. In this study, plants were grown for a full life-cycle assessment (90 days of exposure) in natural soil amended with nano CuO (nCuO), bulk CuO (bCuO), and ionic copper (CuCl2) at 0, 125, 250, and 500 mg kg−1. Based on our experimental findings, none of the treatments significantly affected stem elongation, plant dry biomass, foliar area, leaf chlorophyll content, and fruit productivity of bell pepper. However, ionic copper significantly decreased the gas exchange parameters, evapotranspiration, stomatal conductance, and photosynthesis by an average of 41%, 59%, and 38%, respectively, compared to the other treatments at select concentrations (p ≤ 0.05). The ICP-OES data showed that, except for bCuO at 500 mg kg−1, at 250 mg kg−1 and above, the three compounds significantly increased root Cu (196%, 184%, and 184%) with respect to the control. Only at 500 mg kg−1, ionic Cu gave significantly higher root Cu compared to the other Cu treatments. Additionally, at 125 mg kg−1, leaf P was 41% lower for nCuO, compared to the bCuO treatment. At 500 mg kg−1, nCuO reduced Zn by 55% in leaves and 47% in fruits, compared to the control (p ≤ 0.05); however, it is premature to assert that the reduction in fruit Zn compromises the nutritional quality of bell pepper. Overall, this investigation showed that, at the concentrations tested, nCuO presented low toxicity to bell pepper, with rare differences between nano and bulk treatment responses

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

Transport of Zn in a sandy loam soil treated with ZnO NPs and uptake by corn plants: Electron microprobe and confocal microscopy studies

The manufacture and multiple uses of zinc oxide (ZnO) nanoparticles (NPs) will represent a possible source of soil contamination. Little is known about how these NPs transport in soil and plants. In this research, the transport of Zn/ZnO NPs in sandy loam soil and the uptake by corn plants (Zea mays) was investigated. Results showed that ZnO NPs exhibit low mobility in a soil column at various ionic strengths. Elution curves suggest that some of the adsorbed ZnO NPs/Zn were released in the presence of chemical perturbations. The breakthrough of released Zn coincided with Fe and Al (indicator of soil colloids) suggesting that soil colloids may act as carriers of strongly adsorbed NPs. By using electron microprobe, Zn/ZnO NPs aggregates were visualized associate with soil clay minerals. The uptake (mg/kg) of Zn by one-month old corn plants varied from 69 to 409 in roots and from 100 to 350 in shoots, respectively, in soils contaminated with different concentrations of ZnO NPs (from 100 to 800 mg NPs/kg soil). Confocal microscope images showed that ZnO NPs aggregates penetrated the root epidermis and cortex through the apoplastic pathway; however, the presence of some NP aggregates in xylem vessels suggests that the aggregates passed the endodermis through the symplastic pathway

Tomato Fruit Nutritional Quality Is Altered by the Foliar Application of Various Metal Oxide Nanomaterials

Carbohydrates and phytonutrients play important roles in tomato fruit’s nutritional quality. In the current study, Fe3O4, MnFe2O4, ZnFe2O4, Zn0.5Mn0.5Fe2O4, Mn3O4, and ZnO nanomaterials (NMs) were synthesized, characterized, and applied at 250 mg/L to tomato plants via foliar application to investigate their effects on the nutritional quality of tomato fruits. The plant growth cycle was conducted for a total of 135 days in a greenhouse and the tomato fruits were harvested as they ripened. The lycopene content was initially reduced at 0 stored days by MnFe2O4, ZnFe2O4, and Zn0.5Mn0.5Fe2O4; however, after a 15-day storage, there was no statistical difference between the treatments and the control. Moreover, the β-carotene content was also reduced by Zn0.5Mn0.5Fe2O4, Mn3O4, and ZnO. The effects of the Mn3O4 and ZnO carried over and inhibited the β-carotene after the fruit was stored. However, the total phenolic compounds were increased by ZnFe2O4, Zn0.5Mn0.5Fe2O4, and ZnO after 15 days of storage. Additionally, the sugar content in the fruit was enhanced by 118% and 111% when plants were exposed to Mn3O4 and ZnO, respectively. This study demonstrates both beneficial and detrimental effects of various NMs on tomato fruit quality and highlights the need for caution in such nanoscale applications during crop growth

Influence of CeO2 and ZnO Nanoparticles on Cucumber Physiological Markers and Bioaccumulation of Ce and Zn: A Life Cycle Study

With the dramatic increase in nanotechnologies, it has become increasingly likely that food crops will be exposed to excess engineered nanoparticles (NPs). In this study, cucumber plants were grown to full maturity in soil amended with either CeO2 or ZnO NPs at concentrations of 0, 400, and 800 mg/kg. Chlorophyll and gas exchange were monitored, and physiological markers were recorded. Results showed that, at the concentrations tested, neither CeO2 nor ZnO NPs impacted cucumber plant growth, gas exchange, and chlorophyll content. However, at 800 mg/kg treatment, CeO2 NPs reduced the yield by 31.6% compared to the control (p ≤ 0.07). ICP-MS results showed that the high concentration treatments resulted in the bioaccumulation of Ce and Zn in the fruit (1.27 mg of Ce and 110 mg Zn per kg dry weight). μ-XRF images exhibited Ce in the leaf vein vasculature, suggesting that Ce moves between tissues with water flow during transpiration. To the authors’ knowledge, this is the first holistic study focusing on the impacts of CeO2 and ZnO NPs in the life cycle of cucumber plants

Monitoring the Environmental Effects of CeO2 and ZnO Nanoparticles Through the Life Cycle of Corn (\u3ci\u3eZea mays\u3c/i\u3e) Plants and in Situ μ-XRF Mapping of Nutrients in Kernels

Information about changes in physiological and agronomic parameters through the life cycle of plants exposed to engineered nanoparticles (NPs) is scarce. In this study, corn (Zea mays) plants were cultivated to full maturity in soil amended with either nCeO2 or nZnO at 0, 400, and 800 mg/kg. Gas exchange was monitored every 10 days, and at harvest, bioaccumulation of Ce and Zn in tissues was determined by ICP-OES/MS. The effects of NPs exposure on nutrient concentration and distribution in ears were also evaluated by ICP-OES and μ-XRF. Results showed that nCeO2 at both concentrations did not impact gas exchange in leaves at any growth stage, while nZnO at 800 mg/kg reduced net photosynthesis by 12%, stomatal conductance by 15%, and relative chlorophyll content by 10% at day 20. Yield was reduced by 38% with nCeO2 and by 49% with nZnO. Importantly, μ-XRF mapping showed that nCeO2 changed the allocation of calcium in kernels, compared to controls. In nCeO2 treated plants, Cu, K, Mn, and Zn were mainly localized at the insertion of kernels into cobs, but Ca and Fe were distributed in other parts of the kernels. Results showed that nCeO2 and nZnO reduced corn yield and altered quality of corn

Monitoring the environmental effects of CeO\u3csub\u3e2\u3c/sub\u3e and ZnO nanoparticles through the life cycle of corn (Zea mays) plants and in situ μ-XRF mapping of nutrients in kernels

© 2015 American Chemical Society. Information about changes in physiological and agronomic parameters through the life cycle of plants exposed to engineered nanoparticles (NPs) is scarce. In this study, corn (Zea mays) plants were cultivated to full maturity in soil amended with either nCeO2 or nZnO at 0, 400, and 800 mg/kg. Gas exchange was monitored every 10 days, and at harvest, bioaccumulation of Ce and Zn in tissues was determined by ICP-OES/MS. The effects of NPs exposure on nutrient concentration and distribution in ears were also evaluated by ICP-OES and μ-XRF. Results showed that nCeO2 at both concentrations did not impact gas exchange in leaves at any growth stage, while nZnO at 800 mg/kg reduced net photosynthesis by 12%, stomatal conductance by 15%, and relative chlorophyll content by 10% at day 20. Yield was reduced by 38% with nCeO2 and by 49% with nZnO. Importantly, μ-XRF mapping showed that nCeO2 changed the allocation of calcium in kernels, compared to controls. In nCeO2 treated plants, Cu, K, Mn, and Zn were mainly localized at the insertion of kernels into cobs, but Ca and Fe were distributed in other parts of the kernels. Results showed that nCeO2 and nZnO reduced corn yield and altered quality of corn

CeO\u3csub\u3e2\u3c/sub\u3e and ZnO nanoparticles change the nutritional qualities of cucumber (Cucumis sativus)

There is lack of information about the effects of nanoparticles (NPs) on cucumber fruit quality. This study aimed to determine possible impacts on carbohydrates, proteins, mineral nutrients, and antioxidants in the fruit of cucumber plants grown in soil treated with CeO2 and ZnO NPs at 400 and 800 mg/kg. Fourier transform infrared spectroscopy (FTIR) was used to detect changes in functional groups, while ICP-OES and μ-XRF were used to quantify and map the distribution of nutrient elements, respectively. Results showed that none of the ZnO NP concentrations affected sugars; however at 400 mg/kg, CeO2 and ZnO NPs increased starch content. Conversely, CeO 2 NPs did not affect starch content but impacted nonreducing sugar content (sucrose). FTIR data showed changes in the fingerprint regions of 1106, 1083, 1153, and 1181, indicating that both NPs altered the carbohydrate pattern. ZnO NPs did not impact protein fractionation; however, CeO2 NPs at 400 mg/kg increased globulin and decreased glutelin. Both CeO2 and ZnO NPs had no impact on flavonoid content, although CeO2 NPs at 800 mg/kg significantly reduced phenolic content. ICP-OES results showed that none of the treatments reduced macronutrients in fruit. In case of micronutrients, all treatments reduced Mo concentration, and at 400 mg/kg, ZnO NPs reduced Cu accumulation. μ-XRF revealed that Cu, Mn, and Zn were mainly accumulated in cucumber seeds. To the best of the authors\u27 knowledge this is the first report on the nutritional quality of cucumber fruit attributed to the impact of CeO2 and ZnO NPs. © 2014 American Chemical Society

CeO2 and ZnO Nanoparticles Change the Nutritional Qualities of Cucumber (\u3ci\u3eCucumis sativus\u3c/i\u3e)

There is lack of information about the effects of nanoparticles (NPs) on cucumber fruit quality. This study aimed to determine possible impacts on carbohydrates, proteins, mineral nutrients, and antioxidants in the fruit of cucumber plants grown in soil treated with CeO2 and ZnO NPs at 400 and 800 mg/kg. Fourier transform infrared spectroscopy (FTIR) was used to detect changes in functional groups, while ICP-OES and μ-XRF were used to quantify and map the distribution of nutrient elements, respectively. Results showed that none of the ZnO NP concentrations affected sugars; however at 400 mg/kg, CeO2 and ZnO NPs increased starch content. Conversely, CeO2 NPs did not affect starch content but impacted nonreducing sugar content (sucrose). FTIR data showed changes in the fingerprint regions of 1106, 1083, 1153, and 1181, indicating that both NPs altered the carbohydrate pattern. ZnO NPs did not impact protein fractionation; however, CeO2 NPs at 400 mg/kg increased globulin and decreased glutelin. Both CeO2 and ZnO NPs had no impact on flavonoid content, although CeO2 NPs at 800 mg/kg significantly reduced phenolic content. ICP-OES results showed that none of the treatments reduced macronutrients in fruit. In case of micronutrients, all treatments reduced Mo concentration, and at 400 mg/kg, ZnO NPs reduced Cu accumulation. μ-XRF revealed that Cu, Mn, and Zn were mainly accumulated in cucumber seeds. To the best of the authors’ knowledge this is the first report on the nutritional quality of cucumber fruit attributed to the impact of CeO2 and ZnO NPs