Exposure modeling of engineered nanoparticles in the environment

The aim of this study was to use a life-cycle perspective to model the quantities of engineered nanoparticles released into the environment. Three types of nanoparticles were studied: nano silver (nano-Ag), nano TiO2 (nano-TiO2), and carbon nanotubes (CNT). The quantification was based on a substance flow analysis from products to air, soil, and water in Switzerland. The following parameters were used as model inputs: estimated worldwide production volume, allocation of the production volume to product categories, particle release from products, and flow coefficients within the environmental compartments. The predicted environmental concentrations (PEC) were then compared to the predicted no effect concentrations (PNEC) derived from the literature to estimate a possible risk. The expected concentrations of the three nanoparticles in the different environmental compartments vary widely, caused by the different life cycles of the nanoparticle-containing products. The PEC values for nano-TiO2 in water are 0.7--16 microg/L and close to or higher than the PNEC value for nano-TiO2 (< 1 microg/L). The risk quotients (PEC/PNEC) for CNT and nano-Ag were much smaller than one, therefore comprising no reason to expect adverse effects from those particles. The results of this study make it possible for the first time to carry out a quantitative risk assessment of nanoparticles in the environment and suggest further detailed studies of nano-TiO2.     

Detection and characterization of engineered nanoparticles in food and the environment

Nanotechnology is developing rapidly and, in the future, it is expected that increasingly more products will contain some sort of nanomaterial. However, to date, little is known about the occurrence, fate and toxicity of nanoparticles. The limitations in our knowledge are partly due to the lack of methodology for the detection and characterisation of engineered nanoparticles in complex matrices, i.e. water, soil or food. This review provides an overview of the characteristics of nanoparticles that could affect their behaviour and toxicity, as well as techniques available for their determination. Important properties include size, shape, surface properties, aggregation state, solubility, structure and chemical composition. Methods have been developed for natural or engineered nanomaterials in simple matrices, which could be optimized to provide the necessary information, including microscopy, chromatography, spectroscopy, centrifugation, as well as filtration and related techniques. A combination of these is often required. A number of challenges will arise when analysing environmental and food materials, including extraction challenges, the presence of analytical artifacts caused by sample preparation, problems of distinction between natural and engineered nanoparticles and lack of reference materials. Future work should focus on addressing these challenges.     

Detection and characterization of engineered nanoparticles in food and the environment

Nanotechnology is developing rapidly and, in the future, it is expected that increasingly more products will contain some sort of nanomaterial. However, to date, little is known about the occurrence, fate and toxicity of nanoparticles. The limitations in our knowledge are partly due to the lack of methodology for the detection and characterisation of engineered nanoparticles in complex matrices, i.e. water, soil or food. This review provides an overview of the characteristics of nanoparticles that could affect their behaviour and toxicity, as well as techniques available for their determination. Important properties include size, shape, surface properties, aggregation state, solubility, structure and chemical composition. Methods have been developed for natural or engineered nanomaterials in simple matrices, which could be optimized to provide the necessary information, including microscopy, chromatography, spectroscopy, centrifugation, as well as filtration and related techniques. A combination of these is often required. A number of challenges will arise when analysing environmental and food materials, including extraction challenges, the presence of analytical artifacts caused by sample preparation, problems of distinction between natural and engineered nanoparticles and lack of reference materials. Future work should focus on addressing these challenges.     

Organic sorbate-organoclay interactions in aqueous and hydrophobic environments: sorbate-water competition

Sorption of nitrobenzene, phenol, and m-nitrophenol from water and n-hexadecane was measured on Na-montmorillonite and organoclays in which 41 and 90% of the exchange capacity of the Na-clay was occupied by hexadecyltrimethylammonium. The strength of sorbate-sorbent interactions in n-hexadecane for all three sorbents was in the following order: nitrobenzene < phenol < m-nitrophenol. The magnitude of the distribution coefficients suggests that the contribution to solute uptake of partitioning between n-hexadecane and the organic pseudophase of the dried organoclays is minor, whereas the major contribution is from adsorptive sorbate-sorbent interactions. Sorption isotherms obtained in different solvents were compared using a sorbate activity scale. In the organoclays, the stronger the tendency of a sorbate to interact with sorption sites, the less pronounced is the reduction in the activity-based sorption due to competition with water. The order of this reduction for the different sorbates is nitrobenzene > phenol > m-nitrophenol. The weakening of sorbate-sorbent interactions resulting from water-sorbate competition might be mitigated by interaction between the organic sorbate and sorbed water molecules. Since the more strongly interacting organic compounds are less susceptible to suppression of sorption in the presence of water, hydrating organoclays may result in an increased differentiation between "weakly" and "strongly" interacting ("nonpolar" and "polar") compounds in the organoclay phase.     

Measurement of engineered nanoparticles in consumer products by surface-enhanced Raman spectroscopy and neutron activation analysis

There has been an increasing number of consumer and food products sold on the market that contain various engineered nanomaterials (ENMs) such as silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs). These nanomaterials possess novel physical and chemical properties that can be used for wide applications in agriculture and food safety. However, current analytical methods to detect and measure ENMs are time-consuming, labor-intensive, and expensive. The objective of this study was to develop a novel, simple, rapid, and accurate method to detect AgNPs and AuNPs in consumer products using surface-enhanced Raman spectroscopy (SERS). SERS measurement was conducted to detect AgNPs and AuNPs using an effective Raman indicator, 4-aminothiophenol (pATP). The pATP can strongly bind onto nanoparticles, generating greatly enhanced Raman signals that can be used for measurement. The pATP was combined with Ag or Au stock solution, AgNO₃, citrate-coated AgNPs, citrate-coated AuNPs, AuCl, AgNPs, AuNPs, and five commercial products to study the differences in their SERS spectral data. The observed spectra of AgNPs and AuNPs have similar peaks at ~?390, ~?1087, and ~?1590 cm^?1 that can be attributed to the C–S stretching vibration, C–C stretching vibration, and C–H stretching vibration, respectively. Neutron activation analysis (NAA) and electron microscopy was used to characterize and quantify AgNPs and AuNPs in the consumer products. The results demonstrate that SERS method in combination with NAA can be an effective method for detection of ENMs, and it can easily distinguish AgNPs and AuNPs from other non-nanoparticle species in the complex matrices.     

Characterization and quantification of engineered nanoparticles in food by epithermal instrumental neutron activation analysis and electron microscopy

Engineered nanoparticles (NPs) have increasingly been used in various areas including agriculture and food packaging, which may potentially cause contamination in food products. In this study, a combination of analytical techniques was used to detect, characterize, and quantify engineered NPs (cerium (IV) oxide (CeO₂), silica (SiO₂) NPs, and their mixture) in food matrices. A series of concentrations of CeO₂, SiO₂, and their mixtures from 0 to 0.75 wt% were mixed in soybean powders. The presence of engineered NPs was investigated using transmission electron microscopy and scanning electron microscopy coupled with energy dispersive spectroscopy. The average size of CeO₂ and SiO₂ was 28.5 and 30.5 nm in diameter, respectively. CeO₂ NPs were irregular octahedral and cubic in shape, while SiO₂ NPs were spherical. The concentration of NPs in soybean powders was analyzed by epithermal instrumental neutron activation analysis (EINAA). Calibration curves were plotted for quantification of NPs in soybean powders (R ² = 0.996 and 0.994 for CeO₂, SiO₂ NPs in soybean powders, respectively; R ² = 0.995 and 0.997 for CeO₂ and SiO₂ NP in a mixture in soybean powders, respectively). The study of the detection limit (DL) demonstrates that at 99 % confidence interval, EINAA can detect both NPs at 0.1 wt% in soybean powders. Satisfactory recoveries were obtained for samples with a concentration at and higher than the DL (86.2–104.7 % for CeO₂ NPs and 85.7–95.2 % for SiO₂ NPs; 87.5–101.3 and 85.6–93.5 % for CeO₂ and SiO₂ NPs in a mixture in soybean powders, respectively).     

Sulfidation processes of PVP-coated silver nanoparticles in aqueous solution: impact on dissolution rate

Despite the increasing use of silver nanoparticles (Ag-NPs) in nanotechnology and their toxicity to invertebrates, the transformations and fate of Ag-NPs in the environment are poorly understood. This work focuses on the sulfidation processes of PVP-coated Ag-NPs, one of the most likely corrosion phenomena that may happen in the environment. The sulfur to Ag-NPs ratio was varied in order to control the extent of Ag-NPs transformation to silver sulfide (Ag?S). A combination of synchrotron-based X-ray Diffraction (XRD) and Extended X-ray Absorption Fine Structure spectroscopy shows the increasing formation of Ag?S with an increasing sulfur to Ag-NPs ratio. TEM observations show that Ag?S forms nanobridges between the Ag-NPs leading to chain-like structures. In addition, sulfidation strongly affects surface properties of the Ag-NPs in terms of surface charge and dissolution rate. Both may affect the reactivity, transport, and toxicity of Ag-NPs in soils. In particular, the decrease of dissolution rate as a function of sulfide exposure may strongly limit Ag-NPs toxicity since released Ag? ions are known to be a major factor in the toxicity of Ag-NPs.     

Removal of heavy metals from aqueous systems with thiol functionalized superparamagnetic nanoparticles

We have shown that superparamagnetic iron oxide (Fe3O4) nanoparticles with a surface functionalization of dimercaptosuccinic acid (DMSA) are an effective sorbent material for toxic soft metals such as Hg, Ag, Pb, Cd, and Tl, which effectively bind to the DMSA ligands and for As, which binds to the iron oxide lattices. The nanoparticles are highly dispersible and stable in solutions, have a large surface area (114 m2/g), and have a high functional group content (1.8 mmol thiols/g). They are attracted to a magnetic field and can be separated from solution within a minute with a 1.2 T magnet. The chemical affinity, capacity, kinetics, and stability of the magnetic nanoparticles were compared to those of conventional resin based sorbents (GT-73), activated carbon, and nanoporous silica (SAMMS) of similar surface chemistries in river water, groundwater, seawater, and human blood and plasma. DMSA-Fe3O4 had a capacity of 227 mg of Hg/g, a 30-fold larger value than GT-73. The nanoparticles removed 99 wt% of 1 mg/L Pb within a minute, while it took over 10 and 120 min for Chelex-100 and GT-73 to remove 96% of Pb.     

Impact of natural organic matter on the physicochemical properties of aqueous C60 nanoparticles

Existing toxicity data indicate that industrial-scale production of C60 fullerene poses a potential threat to the environment. Evaluating the environmental impact of C60 requires careful characterization of its physicochemical properties in the natural aqueous environment. Our study aims to determine the effects of aquatic natural organic matter (NOM) on the physicochemical properties of aqueous C60 nanoparticles, nC60. Stable nC60 suspensions were formed using three different solvent exchange protocols. They were thoroughly characterized for particle size, morphology, and electrophoretic mobility in the absence or presence of two model NOM components, Suwannee River humic acid and fulvic acid. NOM caused disaggregation of nC60 crystals and aggregates under typical solution conditions of natural water, leading to significant changes in particle size and morphology. Such effect increased with increasing NOM concentration. The changes in nC060 size and morphology strongly depended on the nC60 formation pathway. Results from this study indicate that NOM may play a critical role in the transport and toxicity of C60 in the natural aqueous environment.     

Quercetin loaded biopolymeric colloidal particles prepared by simultaneous precipitation of quercetin with hydrophobic protein in aqueous medium

Quercetin loaded biopolymeric colloidal particles were prepared by precipitating quercetin (water insoluble polyphenol) and zein (hydrophobic protein), simultaneously, by adding their hydro-alcoholic solution to aqueous solution in presence of sodium caseinate as an electrosteric stabiliser. The presence of protein resulted in altering the shape of quercetin precipitates from needle-like to spherical shape at higher zein proportions, as confirmed by transmission electron microscopy. The average particle size of zein:quercetin composite particles was below 200 nm (130–161 nm) with negative surface charge (−30 to −41 mV), as confirmed by dynamic light scattering and electrophoretic mobility data. Solid state characterisation (X-ray diffraction) and spectroscopic measurements (UV–Vis and IR spectroscopy) confirmed characteristic changes in quercetin due to the entrapment in the biopolymeric matrix of colloidal particles. Results from anti-oxidant study demonstrated the advantage of entrapping quercetin in the colloidal particles in terms of the chemical stability in the alkaline pH and against photodegradation under UV-light irradiation.     

Interaction of fine particles and nanoparticles with red blood cells visualized with advanced microscopic techniques

So far, little is known about the interaction of nanoparticles with lung cells, the entering of nanoparticles, and their transport through the blood stream to other organs. The entering and localization of different nanoparticles consisting of differing materials and of different charges were studied in human red blood cells. As these cells do not have any phagocytic receptors on their surface, and no actinmyosin system, we chose them as a model for nonphagocytic cells to study how nanoparticles penetrate cell membranes. We combined different microscopic techniques to visualize fine and nanoparticles in red blood cells: (I) fluorescent particles were analyzed by laser scanning microscopy combined with digital image restoration, (II) gold particles were analyzed by conventional transmission electron microscopy and energy filtering transmission electron microscopy, and (III) titanium dioxide particles were analyzed by energy filtering transmission electron microscopy. By using these differing microscopic techniques we were able to visualize and detect particles < or = 0.2 microm and nanoparticles in red blood cells. We found that the surface charge and the material of the particles did not influence their entering. These results suggest that particles may penetrate the red blood cell membrane by a still unknown mechanism different from phagocytosis and endocytosis.     

Exposure of engineered nanoparticles to human lung epithelial cells: influence of chemical composition and catalytic activity on oxidative stress

The chemical and catalytic activity of nanoparticles has strongly contributed to the current tremendous interest in engineered nanomaterials and often serves as a guiding principle for the design of functional materials. Since it has most recently become evident that such active materials can enter into cells or organisms, the present study investigates the level of intracellular oxidations after exposure to iron-, cobalt-, manganese-, and titania-containing silica nanoparticles and the corresponding pure oxides in vitro. The resulting oxidative stress was quantitatively measured as the release of reactive oxygen species (ROS). The use of thoroughly characterized nanoparticles of the same morphology, comparable size, shape, and degree of agglomeration allowed separation of physical (rate of particle uptake, agglomeration, sedimentation) and chemical effects (oxidations). Three sets of control experiments elucidated the role of nanoparticles as carriers for heavy metal uptake and excluded a potential interference of the biological assay with the nanomaterial. The present results indicate that the particles could efficiently enter the cells by a Trojan-horse type mechanism which provoked an up to eight times higher oxidative stress in the case of cobalt or manganese if compared to reference cultures exposed to aqueous solutions of the same metals. A systematic investigation on iron-containing nanoparticles as used in industrial fine chemical synthesis demonstrated that the presence of catalytic activity could strongly alter the damaging action of a nanomaterial. This indicates that a proactive development of nanomaterials and their risk assessment should consider chemical and catalytic properties of nanomaterials beyond a mere focus on physical properties such as size, shape, and degree of agglomeration.     

Incorporation of lipid nanoparticles into calcium alginate beads and characterization of the encapsulated particles by differential scanning calorimetry

The aim of this study was to encapsulate lipid nanoparticle dispersions into calcium alginate microbeads and to investigate the feasibility of this incorporation as well as the stability of the enclosed nanoparticles. Two methods were used to prepare the lipid-containing microbeads by external gelation, i.e. an electrostatic droplet generation technique and a spraying method using the two-fluid spray nozzle of a spray dryer. The particle sizes of the hydrogel beads were determined with laser diffraction. The first method produced particles with median sizes between 330 and 1350 μm, depending on the needle applied. Using the second method smaller particles (∼45 μm) could be prepared. Small tyloxapol-stabilized trimyristin nanoparticles (<100 nm) could easily be incorporated into the differently sized alginate beads. The small size of the lipid nanoparticles leads to a typical melting behavior characterized by the occurrence of multiple discrete melting peaks in their differential scanning calorimetry (DSC) thermograms which enabled the characterization of the lipid particles within the microbeads. Thus, any negative influence of the preparation procedure on the lipid dispersions could be detected and it was possible to verify optimization options of the incorporation procedure. Finally, handling and shelf life of the hydrogel beads were improved by a freezing process.     

Anti-melanoma, tyrosinase inhibitory and anti-microbial activities of gold nanoparticles synthesized from aqueous leaf extracts of Teraxacum officinale

There has been a tenacious search for pharmaceuticals of natural origin, as they are cost-effective and are noted for having little or no side effects. The rate at which diseases are developing resistance to synthetic drugs is quite alarming, and the side effects of these drugs remain an excruciating agony to the pharmaceutical industry. Gold nanoparticles (AuNPs) have wide applications in current technology. However, their use in medicine has not been adequately explored. Chemical methods for the synthesis are associated with environmental benignity and tissue toxicity on in vivo administration. For the first time, we have synthesized AuNPs from leaf extracts of Teraxacum officinale that were found to have significant anti-melanoma, tyrosinase inhibitory and anti-microbial effects, and hence stand as promising candidates for use in cosmetics medical and food industries.     

白藜芦醇在酿酒酵母中的组合表达

将克隆自拟南芥的4cl基因和巨峰葡萄的rs基因,利用降落重叠延伸PCR的方法,成功构建了含有G418抗性筛选标记的酵母表达载体pRS42K-4CL以及含有潮霉素抗性筛选标记的酵母表达载体pRS42H-RS。采用LiAc/SS carrier DNA/PEG法将含有目的基因的2个载体共同转化至酿酒酵母工业菌株EC1118中,通过PCR及酶切鉴定等方法验证重组工程菌。以对香豆酸为底物,将获得的酿酒酵母工程菌于YPD液体培养基中发酵(25℃,150 r/min,96 h),发酵液用乙酸乙酯抽提后采用高效液相色谱(HPLC)法进行检测,其结果显示发酵产物中白藜芦醇的含量为0.78 mg/L。这表明,拟南芥的4cl基因与巨峰葡萄的rs基因在酿酒酵母工程菌中成功得到了表达,并且表达产物利用对香豆酸为前体物质合成了目标产物白藜芦醇。该研究为进一步实现白藜芦醇在酵母中的工业化生产奠定了基础。     

活性白土吸附L-组氨酸的研究

测定了25℃时活性白土吸附L组氨酸的吸附动力学曲线和吸附等温线,结果表明,达到吸附平衡的时间为40min,其最大平衡吸附量为108.5g/kg。考察了pH值、温度、活性白土用量对活性白土吸附L组氨酸的影响,结果表明,pH在5～6之间时吸附量较大;随着温度的升高L组氨酸的吸附量逐渐减少,该吸附是一个放热过程;L组氨酸吸附率随着活性白土用量的增加而不断上升,但吸附量随着活性白土用量的增加而快速减少,工业上采用10%的活性白土用量较适宜。