Root uptake and phytotoxicity of ZnO nanoparticles

Increasing application of nanotechnology highlights the need to clarify nanotoxicity. However, few researches have focused on phytotoxicity of nanomaterials; it is unknown whether plants can uptake and transport nanoparticles. This study was to examine cell internalization and upward translocation of ZnO nanoparticles by Lolium perenne (ryegrass). The dissolution of ZnO nanoparticles and its contribution to the toxicity on ryegrass were also investigated. Zn2+ ions were used to compare and verify the root uptake and phytotoxicity of ZnO nanoparticles in a hydroponic culture system. The root uptake and phytotoxicity were visualized by light scanning electron, and transmission electron microscopies. In the presence of ZnO nanoparticles, ryegrass biomass significantly reduced, root tips shrank, and root epidermal and cortical cells highly vacuolated or collapsed. Zn2+ ion concentrations in bulk nutrient solutions with ZnO nanoparticles were lower than the toxicity threshold of Zn2+ to the ryegrass; shoot Zn contents under ZnO nanoparticle treatments were much lower than that under Zn2+ treatments. Therefore, the phytotoxicity of ZnO nanoparticles was not directly from their limited dissolution in the bulk nutrient solution or rhizosphere. ZnO nanoparticles greatly adhered on to the rootsurface. Individual ZnO nanoparticles were observed present in apoplast and protoplast of the root endodermis and stele. However, translocation factors of Zn from root to shoot remained very low under ZnO nanoparticle treatments, and were much lower than that under Zn2+ treatments, implying that little (if any) ZnO nanoparticles could translocate up in the ryegrass in this study.     

Nanoparticles and their biological and environmental applications

Nanoparticles exhibit unique physical properties (such as particle aggregation and photoemission, and electrical and heat conductivities) and chemical properties (such as catalytic activity), and hence have received much attention from scientists and researchers in different areas of biological sciences. In this review, we briefly summarize the major types of nanoparticle that have been used so far and discuss the possible applications of these nanoparticles in biological and environmental research, and the potential environmental and health impacts associated with the use of these nanoparticles.     

Size dependent and reactive oxygen species related nanosilver toxicity to nitrifying bacteria

The intrinsic slow growth of nitrifying bacteria and their high sensitivity to environmental perturbations often result in cell growth inhibition by toxicants. Nanoparticles are of great concern to the environment because of their small size and high catalytic properties. This work sought to determine size-dependent inhibition by Ag nanoparticles and evaluate the relationship between the inhibition and reactive oxygen species (ROS). Nanoparticles with an average size range of 9-21 nm were synthesized by varying the molar ratios of BH4-/Ag+ in the solution. The resulting ROS generation was quantified in the presence and absence of the bacteria while the degree of inhibition was inferred from specific oxygen uptake rate measurements, determined by extant respirometry. By examining the correlation between nanoparticle size distribution, photocatalytic ROS generation, intracellular ROS accumulation, and nitrification inhibition, we observed that inhibition to nitrifying organisms correlated with the fraction of Ag nanoparticles less than 5 nm in the suspension. It appeared that these size nanoparticles could be more toxic to bacteria than any other fractions of nanoparticles or their counterpart bulk species. Furthermore, inhibition by Ag nanoparticles as well as other forms of silver (AgCl colloid and Ag+ ion) correlated well with the intracellular ROS concentrations, but not with the photocatalytic ROS fractions. The ROS correlations were different for the different forms of silver, indicating that factors other than ROS are also important in determining nanosilver toxicity.     

Oxide nanoparticle uptake in human lung fibroblasts: effects of particle size, agglomeration, and diffusion at low concentrations

Quantitative studies on the uptake of nanoparticles into biological systems should consider simultaneous agglomeration, sedimentation, and diffusion at physiologically relevant concentrations to assess the corresponding risks of nanomaterials to human health. In this paper, the transport and uptake of industrially important cerium oxide nanoparticles, into human lung fibroblasts is measured in vitro after exposing thoroughly characterized particle suspensions to a fibroblast cell culture for particles of four separate size fractions and concentrations ranging from 100 ng g(-1) to 100 microg g(-1) of fluid (100 ppb to 100 ppm). The unexpected findings at such low but physiologically relevant concentrations reveal a strong dependence of the amount of incorporated ceria on particle size, while nanoparticle number density or total particle surface area are of minor importance. These findings can be explained on the basis of a purely physical model. The rapid formation of agglomerates in the liquid is strongly favored for small particles due to a high number density while larger ones stay mainly unagglomerated. Diffusion (size fraction 25-50 nm) or sedimentation (size fraction 250-500 nm) limits the transport of nanoparticles to the fibroblast cells. The biological uptake processes on the surface of the cell are faster than the physical transport to the cell at such low concentrations. Comparison of the colloid stability of a series of oxide nanoparticles reveals that untreated oxide suspensions rapidly agglomerate in biological fluids and allows the conclusion thatthe presented transport and uptake kinetics at low concentrations may be extended to other industrially relevant materials.     

Formation and biological effects of protein corona for food-related nanoparticles

The rapid development of nanoscience and nanoengineering provides new perspectives on the composition of food materials, and has great potential for food biology research and applications. The use of nanoparticle additives and the discovery of endogenous nanoparticles in food make it important to elucidate in vivo safety of nanomaterials. Nanoparticles will spontaneously adsorb proteins during transporting in blood and a protein corona can be formed on the nanoparticle surface inside the human body. Protein corona affects the physicochemical properties of nanoparticles and the structure and function of proteins, which in turn affects a series of biological reactions. This article reviewed basic information about protein corona of food-related nanoparticles, elucidated the influence of protein corona on nanoparticles properties and protein structure and function, and discussed the effect of protein corona on nanoparticles in vivo. The effects of protein corona on nanoparticles transport, cellular uptake, cytotoxicity, and immune response were reviewed, and the reasons for these effects were also discussed. Finally, future research perspectives for food protein corona were proposed. Protein corona gives food nanoparticles a new identity, which makes proteins bound to nanoparticles undergo structural transformations that affect their recognition by receptors in vivo. It can have positive or negative impacts on cellular uptake and toxicity of nanoparticles and even trigger immune responses. Understanding the effects of protein corona have potential in evaluating the fate of the food-related nanoparticles, providing physicochemical and biological information about the interaction between proteins and foodborne nanoparticles. The review article will help to evaluate the safety of protein coronas formed on nanoparticles in food, and may provide fundamental information for understanding and controlling nanotoxicity.     

Fabrication of nanoparticles using partially purified pomegranate ellagitannins and gelatin and their apoptotic effects

Scope: Nanoparticles possess unique chemical and biological properties compared to bulk materials. Bioactive food components encapsulated in nanoparticles may have increased bioavailability and bioactivities. Methods and results: Self‐assembled nanoparticles made of partially purified pomegranate ellagitannins (PPE) and gelatin were fabricated using three PPE‐to‐gelatin mass ratios (1:5, 5:5, and 7:5). The PPE contained 16.6% (w/w) of punicalagin A, 32.5% (w/w) of punicalagin B, and a small amount of ellagic acid‐hexoside and ellagic acid (1%, w/w). Nanoparticles fabricated using the ratio 5:5 had a particle size of 149.3±1.8 nm, positive zeta‐potential of 17.8±0.9 mV, production efficiency 53.0±4.2%, and spherical morphology under scanning electron microscopy. Loading efficiency of punicalagin A and punicalagin B in these particles were 94.2±0.4% and 83.8±0.5 %, respectively. Loading capacity was 14.8±1.5% and 25.7±2.2%, respectively. Only punicalagin anomers were able to bind with gelatin to form nanoparticles, whereas ellagic acid‐hexoside or ellagic acid could not. Fourier transform infrared spectroscopy suggested that the interactions between ellagitannins and gelatin were hydrogen bonding and hydrophobic interactions. PPE‐gelatin nanoparticle suspension was less effective than PPE in inducing the early stage of apoptosis on human promyelocytic leukemia cells HL‐60. But they had similar effects in inducing late stage of apoptosis and necrosis. Conclusion: Pomegranate ellagitannins bind with gelatin to form self‐assembled nanoparticles. Ellagitannins encapsulated in nanoparticles had decreased apoptotic effects on leukemia cells HL‐60.     

Removal of oxide nanoparticles in a model wastewater treatment plant: influence of agglomeration and surfactants on clearing efficiency

The rapidly increasing production of engineered nanoparticles has created a demand for particle removal from industrial and communal wastewater streams. Efficient removal is particularly important in view of increasing long-term persistence and evidence for considerable ecotoxicity of specific nanoparticles. The present work investigates the use of a model wastewater treatment plant for removal of oxide nanoparticles. While a majority of the nanoparticles could be captured through adhesion to clearing sludge, a significant fraction of the engineered nanoparticles escaped the wastewater plant's clearing system, and up to 6 wt % of the model compound cerium oxide was found in the exit stream of the model plant. Our study demonstrates a significant influence of surface charge and the addition of dispersion stabilizing surfactants as routinely used in the preparation of nanoparticle derived products. A detailed investigation on the agglomeration of oxide nanoparticles in wastewater streams revealed a high stabilization of the particles against clearance (adsorption on the bacteria from the sludge). This unexpected finding suggests a need to investigate nanoparticle clearance in more detail and demonstrates the complex interactions between dissolved species and the nanoparticles within the continuously changing environment of the clearing sludge.     

Visualizing the air-to-leaf transfer and within-leaf movement and distribution of phenanthrene: further studies utilizing two-photon excitation microscopy

Two-photon excitation microscopy (TPEM) was used to monitor the air-to-leaf transfer and within-leaf movement and distribution of phenanthrene in two plant species (maize and spinach) grown within a contaminated atmosphere. Phenanthrene was visualized within the leaf cuticle, epidermis, mesophyll, and vascular system of living maize and spinach plants. No detectable levels of phenanthrene were observed in the roots or stems of either species, suggesting phenanthrene entered the leaves only from the air. Phenanthrene was observed in both the abaxial and adaxial cuticles of both species. Particulate material (aerosols/dust) contaminated with phenanthrene was located at the surface of the cuticle and became encapsulated within the cuticularwaxes. Overtime, diffuse areas of phenanthrene formed within the adjacent cuticle. However, most of the visualized phenanthrene reaching the leaves arrived via gas-phase transfer. Phenanthrene was found within the wax plugs of stomata of both species and on the external surface of the stomatal pore, but not on the internal surface, or within the sub-stomatal cavity. Phenanthrene diffused through the cuticles of both species in 24-48 h, entering the epidermis to reside predominantly within the cell walls of maize (indicative of apoplastic transport) and the cellular cytoplasm of spinach (indicative of symplastic transport). Phenanthrene accumulated within the spinach cytoplasm where it concentrated into the vacuoles of the epidermal cells. Phenanthrene was not observed to accumulate in the cytoplasm of maize cells. Phenanthrene entered the internal mesophyll of both species, and was found within the mesophyll cell walls, at the surface of the chloroplasts, and within the cellular cytoplasm. Phenanthrene was observed within the xylem of maize following 12 days exposure. The cuticle and epidermis at the edges of spinach leaves had a systematically higher concentration of phenanthrene than the cuticle and epidermal cells at the center of the leaf. These results provide important new information about how such compounds enter, move, and distribute within leaves, and suggest that contemporary views of such processes based on data obtained from traditional analytical methods may need to be revised.     

Microbial bioavailability of covalently bound polymer coatings on model engineered nanomaterials

By controlling nanoparticle flocculation and deposition, polymer coatings strongly affect nanoparticle fate, transport, and subsequent biological impact in the environment. Biodegradation is a potential route to coating breakdown, but it is unknown whether surface-bound polymers are bioavailable. Here we demonstrate, for the first time, that polymer coatings covalently bound to nanomaterials are bioavailable. Model poly(ethylene oxide) (PEO) brush-coated nanoparticles (densely cross-linked bottle brush copolymers) with hydrophobic divinyl benzene cross-linked cores and hydrophilic PEO brush shells, having ~ 30 nm hydrodynamic radii, were synthesized to obtain a nanomaterial in which biodegradation was the only available coating breakdown mechanism. PEO-degrading enrichment cultures were supplied with either PEO homopolymer or PEO brush nanoparticles as the sole carbon source, and protein and CO? production were monitored as a measure of biological conversion. Protein production after 90 h corresponded to 14% and 8% of the total carbon available in the PEO homopolymer and PEO brush nanoparticle cultures, respectively, and CO? production corresponded to 37% and 3.8% of the carbon added to the respective system. These results indicate that the PEO in the brush is bioavailable. Brush biodegradation resulted in particle aggregation, pointing to the need to understand biologically mediated transformations of nanoparticle coatings in order to understand the fate and transport of nanoparticles in the environment.     

Copper oxide nanoparticle mediated DNA damage in terrestrial plant models

Engineered nanoparticles, due to their unique electrical, mechanical, and catalytic properties, are presently found in many commercial products and will be intentionally or inadvertently released at increasing concentrations into the natural environment. Metal- and metal oxide-based nanomaterials have been shown to act as mediators of DNA damage in mammalian cells, organisms, and even in bacteria, but the molecular mechanisms through which this occurs are poorly understood. For the first time, we report that copper oxide nanoparticles induce DNA damage in agricultural and grassland plants. Significant accumulation of oxidatively modified, mutagenic DNA lesions (7,8-dihydro-8-oxoguanine; 2,6-diamino-4-hydroxy-5-formamidopyrimidine; 4,6-diamino-5-formamidopyrimidine) and strong plant growth inhibition were observed for radish (Raphanus sativus), perennial ryegrass (Lolium perenne), and annual ryegrass (Lolium rigidum) under controlled laboratory conditions. Lesion accumulation levels mediated by copper ions and macroscale copper particles were measured in tandem to clarify the mechanisms of DNA damage. To our knowledge, this is the first evidence of multiple DNA lesion formation and accumulation in plants. These findings provide impetus for future investigations on nanoparticle-mediated DNA damage and repair mechanisms in plants.     

Filter-feeding bivalves store and biodeposit colloidally stable gold nanoparticles

Nanoparticles resistant to salt-induced aggregation are continually being developed for biomedical and industrial applications. Because of their colloidal stability these functionalized nanoparticles are anticipated to be persistent aquatic contaminants. Here, we show that Corbicula fluminea, a globally distributed clam that is a known sentinel of aquatic ecosystem contamination, can uptake and biodeposit bovine serum albumin (BSA) stabilized gold nanoparticles. Nanoparticle clearance rates from suspension were dictated by diameter and concentration, with the largest particles cleared most quickly on a mass basis. Particle capture facilitates size-selective 'biopurification' of particle suspensions with nanoscale resolution. Nanoparticles were retained either within the clam digestive tract or excreted in feces. Our results suggest that biotransformation and biodeposition will play a significant role in the fate and transport of persistent nanoparticles in aquatic systems.     

Phytoremediation of mercury and organomercurials in chloroplast transgenic plants: enhanced root uptake, translocation to shoots, and volatilization

Transgenic tobacco plants engineered with bacterial merA and merB genes via the chloroplast genome were investigated to study the uptake, translocation of different forms of mercury (Hg) from roots to shoots, and their volatilization. Untransformed plants, regardless of the form of Hg supplied, reached a saturation point at 200 microM of phenylmercuric acetate (PMA) or HgCl2, accumulating Hg concentrations up to 500 microg g(-1) with significant reduction in growth. In contrast, chloroplast transgenic lines continued to grow well with Hg concentrations in root tissues up to 2000 microg g(-1). Chloroplasttransgenic lines accumulated both the organic and inorganic Hg forms to levels surpassing the concentrations found in the soil. The organic-Hg form was absorbed and translocated more efficiently than the inorganic-Hg form in transgenic lines, whereas no such difference was observed in untransformed plants. Chloroplast-transgenic lines showed about 100-fold increase in the efficiency of Hg accumulation in shoots compared to untransformed plants. This is the first report of such high levels of Hg accumulation in green leaves or tissues. Transgenic plants attained a maximum rate of elemental-Hg volatilization in two days when supplied with PMA and in three days when supplied with inorganic-Hg, attaining complete volatilization within a week. The combined expression of merAB via the chloroplast genome enhanced conversion of Hg2+ into Hg,0 conferred tolerance by rapid volatilization and increased uptake of different forms of mercury, surpassing the concentrations found in the soil. These investigations provide novel insights for improvement of plant tolerance and detoxification of mercury.     

Distribution of selenium and phenolics in buckwheat plants grown from seeds soaked in Se solution and under different levels of UV-B radiation

Seeds of common buckwheat (Fagopyrum esculentum) were soaked in water, sodium selenate (5, 10 or 20 mg Se^VI/L), or sodium selenite (10 or 20 mg Se^IV/L) solutions. Plants grown from soaked seeds were exposed to reduced UV-B radiation, ambient, or enhanced UV-B. The mass fraction of selenium in leaves was much higher in plants obtained from seeds soaked with selenate (up to 185 ng/g) in comparison to selenite (up to 103 ng/g). In plants obtained from seeds soaked in water, regardless of UV-B levels, the highest concentration of selenium was found in leaves, where the values were between 45 and 66 ng Se/g. In buckwheat leaves 44.5–63.6 mg/100 g d.m. of fagopyrin was found, and in stems 14.3–26.4 mg/100 g d.m.; here no influence of seed soaking solution or UV-B exposure was found. The content of total flavonoids in leaves was 7.8–15.9% and in stems 1.4–4.1%.     

Transgenic Maize

Transgenic maize for commercial production currently confers either insect resistance or herbicide tolerance or a combination of these traits. The introduction of transgenic maize has resulted in an increase in maize production. Effects of these transgenic plants on non‐target insects, soil, and animals consuming them have been studied, and in general these effects are small. The economic impact of transgenic maize into the global market has been tremendous because maize can no longer be marketed as a simple commodity. Identity preservation and tracking systems are now required to ensure that maize meets the tolerance levels set by different countries for content of transgenic maize.     

Biological evaluation of improved local maize hybrids using rats

The incorporation of the opaque-2 gene into local maize hybrids results in an increase in the levels of lysine and tryptophan and an improved biological value. The average weight gain of rats fed diets containing opaque-2 maize, normal maize and normal maize supplemented with synthetic lysine was 22·6 g, 12·2 g and 18·4 g respectively. Using other parameters: Efficiency of Food Conversion (EFC), Net Protein Utilisation (NPU), Protein Efficiency Ratio (PER) and Biological Value (BV), opaque-2 hybrid was superior to normal maize or normal maize supplemented with lysine.Supplementation of opaque-2 maize with lysine alone had no added beneficial effect but supplementation of normal maize with lysine and tryptophan gave an additional improvement in its biological value.     

Cereal starch nanoparticles—A prospective food additive: A review

Starch is one of the most abundant biopolymers in nature and is typically isolated from plants in the form of micro-scale granules. Raw starch has limited applications due to its innate disadvantages such as poor solubility in cold water, tendency to retrograde and high viscosity once it is gelatinized. Therefore, some degree of modification is required to enhance its functionality. Starch nanoparticle is one of the products of such modification. Chemical, enzymatic, and physical treatments are used for the preparation of starch nanoparticles and to study their granular and molecular structures. Characterization of starch nanoparticles on the size distribution, crystalline structure, and physical properties in relation to the starch sources and preparation methods can be done using various characterization tools e.g. Scanning Electron Microscopy, Transmission Electron Microscopy, Atomic Florescence Microscopy, etc. Starch nanoparticles can be used as a food additive as it has adverse range of uses in food such as emulsion stabilizer, fat replacer, Thickener, or rheology modifier etc.     

Effect of photoperiod on flavonoid pathway activity in sweet potato (Ipomoea batatas (L.) Lam.) leaves

Compared with those of major commercial leafy vegetables, leaves of sweet potato have higher contents of flavonoids and phenolic acids, which provide significant health benefits and may be used as natural colourants. We have analysed the expression of key flavonoid biosynthesis genes using RT-PCR and the accumulation of polyphenolic compounds using high-performance liquid chromatography coupled to a photodiode-array detector, during the development of leaves of sweet potato plants growing under either long day or short day photoperiods. A massive induction of flavonoid pathway gene expression, correlating with a dramatic increase in the content of an anthocyanin, catechins, flavonols, hydroxycinnamic acids and hydroxybenzoic acids, was observed during sweet potato leaf exposure to a long day photoperiod. These results provide further support for the protective role of flavonoids and phenolic acids against enhanced light exposure in plants.     

Interactions between plants in intercropped maize and common bean

BACKGROUND: Intercropping maize (Zea mays L.) with common bean (Phaseolus vulgaris L.) can give silage yields that are as high as with monocropped maize, but with more crude protein. Interactions between maize and common bean intercropped in the UK were assessed at a range of plant densities (maize 100 000, 75 000 and 50 000 plants ha^?1 and beans at a fixed density of 50 000 plants ha^?1). RESULTS: In monoculture, maize yield per plant increased as planting density decreased from 100 000 to 50 000 plants ha^?1. At a density of 50 000 maize plants ha^?1, both dry weight yield per plant and shoot N concentrations of maize were greater when intercropped with 50 000 Type III (bush‐type) bean plants ha^?1 than in monoculture (196.4 g plant^?1 and 167.0 g plant^?1; 21.6 g N kg^?1 dry mass and 17.4 g N kg^?1 dry mass, respectively), but intercropping Type IV (climbing) beans at this density combination had no effects on either maize plant weight or shoot N concentration. Invariably, however, the beans grown at 50 000 plants ha^?1 were adversely affected by competition with maize at all densities. Weight per plant of both Type III (bush‐type) and Type IV (climbing) beans grown in competition with 50 000 maize plants ha^?1 was only about half that of when grown alone. Intercropping gave increased mycorrhizal colonization of both species, especially in unfertilized plots, and gave a higher shoot N concentration in the maize. The beans had more nodules in the intercrop than in the monocrop. CONCLUSIONS: Intercropping maize with Type III common bean at 50 000 plants of each species ha^?1 increases yield per maize plant above that of monoculture maize at 50 000 plants ha^?1, despite plant density being doubled. This increase is brought about by increased maize shoot N concentration. Mycorrhizal infection of both species, and bean plant nodulation, are stimulated, and N moves from the beans to the maize. Copyright © 2008 Society of Chemical Industry     

Standardization of Nanoparticle Characterization: Methods for Testing Properties,Stability, and Functionality of Edible Nanoparticles

There has been a rapid increase in the fabrication of various kinds of edible nanoparticles for oral delivery of bioactive agents, such as those constructed from proteins, carbohydrates, lipids, and/or minerals. It is currently difficult to compare the relative advantages and disadvantages of different kinds of nanoparticle-based delivery systems because researchers use different analytical instruments and protocols to characterize them. In this paper, we briefly review the various analytical methods available for characterizing the properties of edible nanoparticles, such as composition, morphology, size, charge, physical state, and stability. This information is then used to propose a number of standardized protocols for characterizing nanoparticle properties, for evaluating their stability to environmental stresses, and for predicting their biological fate. Implementation of these protocols would facilitate comparison of the performance of nanoparticles under standardized conditions, which would facilitate the rational selection of nanoparticle-based delivery systems for different applications in the food, health care, and pharmaceutical industries.     

Influence of aqueous food simulants on potential nanoparticle detection in migration studies involving nanoenabled food-contact substances

Research focused on assessing potential consumer exposure to nanoparticles released from nano-enabled food-contact materials (FCMs) has often reached conflicting conclusions regarding the detection of migrating nanoparticles. These conflicting conclusions, coupled with the potential for nanoparticles to be unstable in certain food simulants, has necessitated a closer look at the role played by food simulants recommended for use in nanoparticle migration evaluation. The influence of aqueous food simulants on nanoparticles under migration evaluation conditions is reported herein. The stability of silver nanoparticles (AgNP) spiked into three food simulants (water, 10% ethanol and 3% acetic acid) was investigated using asymmetric flow field-flow fractionation (AF4), ultrafiltration, electron microscopy (EM), and single-particle inductively coupled plasma mass spectrometry (sp-ICP-MS). While 3% acetic acid induced significant oxidative dissolution of AgNP to silver ions, there were very minor to no changes in the physicochemical properties of AgNP in water and 10% ethanol.