Chemical stability of metallic nanoparticles: A parameter controlling their potential cellular toxicity in vitro

The level of production of nanoparticles will inevitably lead to their appearance in air, water, soils, and organisms. A theoretical framework that relates properties of nanoparticles to their biological effects is needed to identify possible risks to human health and the environment. This paper considers the properties of dispersed metallic nanoparticles and highlights the relationship between the chemical stability of these nanoparticles and their in vitro toxicity. Analysis of published data suggests that chemically stable metallic nanoparticles have no significant cellular toxicity, whereas nanoparticles able to be oxidized, reduced or dissolved are cytotoxic and even genotoxic for cellular organisms.     

Removal of trichloroethylene from water by cellulose acetate supported bimetallic Ni/Fe nanoparticles

In this study, cellulose acetate (CA) supported Ni/Fe nanoparticles were prepared and the ability of these nanoparticles to remove trichloroethylene (TCE) from water was studied. The effects of TCE reduction by the nanoparticles and sorption by the CA support were accounted for separately in the model. CA supported post-coated Ni/Fe nanoparticles were used to investigate the effect of metal particle composition on the observed reduction rate constant. The results show that the metal mass normalized observed reduction rate constant was proportional to the Ni content in the post-coated Ni/Fe nanoparticles in the range of 0-14.3 wt.%. This constant reached a maximum between 14.3 and 21.4 wt.% and decreased with further increase in Ni content. CA supported co-reduced Ni/Fe bimetallic nanoparticles gave poorer performance compared to CA supported post-coated Ni/Fe bimetallic nanoparticles at the same Ni content in Ni/Fe nanoparticles.     

Distribution and bioavailability of ceria nanoparticles in an aquatic ecosystem model

Along with the increasing utilization of engineered nanoparticles, there is a growing concern for the potential environmental and health effects of exposure to these newly designed materials. Understanding the behavior of nanoparticles in the environment is a basic need. The present study aims to investigate the distribution and fate of ceria nanoparticles in an aquatic system model which consists of sediments, water, hornworts, fish and snails, using a radiotracer technique. Concentrations of ceria in the samples at regular time intervals were measured. Ceria nanoparticles were readily removed from the water column and partitioned between different organisms. Both snail and fish have fast absorption and clearance abilities. Hornwort has the highest bioaccumulation factors. At the end of the experiment, sediments accumulated most of the nanoparticles with a recovery of 75.7 ± 27.3% of total ceria nanoparticles, suggesting that sediments are major sinks of ceria nanoparticles.     

Removal of nanoparticles from CMP wastewater by magnetic seeding aggregation

CMP wastewaters have high solids content resulted from abrasive nanoparticles. Tremendous amount of ultrapure water consumption also makes the removal of nanoparticles from CMP wastewaters an important issue. Magnetic seeding aggregation of silica nanoparticles from the oxide CMP wastewater is studied in this work. Magnetite nanoparticles were synthesized and used as seeding particles. The turbidity of the CMP wastewater was reduced from 110 NTU to 7 NTU when solution pH was 6 and no addition of salt. This is because silica and magnetite nanoparticles were highly oppositely charged and the aggregation between silica and magnetite nanoparticles was achieved by electrostatic attractions. When the seeded wastewater was placed in a magnetic field strength higher than 800 G, the turbidity of the CMP wastewater was reduced to 1 NTU, which was clearer than the CMP wastewater treated by many other technologies.     

Genotoxicity of titanium dioxide (TiO2) nanoparticles at two trophic levels: plant and human lymphocytes

The environmental fate and behaviour of titanium dioxide (TiO(2)) nanoparticles is a rapidly expanding area of research. There is a paucity of information regarding toxic effect of TiO(2) nanoparticles in plants and to certain extent in humans. The present study focuses on the effect of exposure of TiO(2) nanoparticles in two trophic levels, plant and human lymphocytes. The genotoxicity of TiO(2) nanoparticles was evaluated using classical genotoxic endpoints, comet assay and DNA laddering technique. DNA damaging potential of TiO(2) nanoparticles in Allium cepa and Nicotiana tabacum as representative of plant system could be confirmed in the comet assay and DNA laddering experiments. In Allium micronuclei and chromosomal aberrations correlated with the reduction in root growth. We detected increased level of malondialdehyde (MDA) concentration at 4mM (0.9 μM) treatment dose of TiO(2) nanoparticles in Allium cepa. This indicated that lipid peroxidation could be involved as one of the mechanism leading to DNA damage. A comparative study of the cytotoxic and genotoxic potential of TiO(2) nanoparticles and bulk TiO(2) particles in human lymphocytes also reveal interesting results. While TiO(2) nanoparticles were found to be genotoxic at a low dose of 0.25 mM followed by a decrease in extent of DNA damage at higher concentrations; bulk TiO(2) particles reveal a more or less dose dependent effect, genotoxic only at dose 1.25 mM and above. The study thus confirms the genotoxic potential of TiO(2) nanoparticles in both plant and human lymphocytes.     

金属纳米材料在厌氧条件下对脱氮副球菌反硝化作用的影响

以脱氮副球菌YF1为实验菌株,研究纳米Fe0和纳米Fe/Ni 2种金属纳米材料对菌体生长及其反硝化作用的影响。实验结果表明:添加纳米材料到反应体系中会降低实验菌株的生长量和生物反硝化作用,纳米Fe/Ni对实验菌株的毒性比纳米Fe0大。在含硝态氮初始浓度为100 mg/L的反硝化培养基中接种脱氮副球菌,于30℃培养20 h,脱氮率为89.47%,而菌+1 000 mg/L纳米Fe/Ni的体系脱氮率仅为64.33%;菌+1 000 mg/L纳米Fe0体系的脱氮率为76.36%。不同体系的反硝化过程均可采用零级动力学模型进行拟合(相关系数R2>0.92)。这2种金属纳米材料对实验菌株的生长量及其反硝化作用的影响程度,与体系的pH和温度有较大关系。     

Influence of titanium dioxide nanoparticles on speciation and bioavailability of arsenite

In this study, the influence of the co-existence of TiO₂ nanoparticles on the speciation of arsenite [As(III)] was studied by observing its adsorption and valence changing. Moreover, the influence of TiO₂ nanoparticles on the bioavailability of As(III) was examined by bioaccumulation test using carp (Cyprinus carpio). The results showed that TiO₂ nanoparticles have a significant adsorption capacity for As (III). Equilibrium was established within 30 min, with about 30% of the initial As (III) being adsorbed onto TiO₂ nanoparticles. Most of aqueous As (III) was oxidized to As(V) in the presence of TiO₂ nanoparticles under sunlight. The carp accumulated considerably more As in the presence of TiO₂ nanoparticles than in the absence of TiO₂ nanoparticles, and after 25-day exposure, As concentration in carp increased by 44%. Accumulation of As in viscera, gills and muscle of the carp was significantly enhanced by the presence of TiO₂ nanoparticles.     

Biotoxicity of nickel oxide nanoparticles and bio-remediation by microalgae Chlorella vulgaris

Adverse effects of manufactured nickel oxide nanoparticles on the microalgae Chlorellavulgaris were determined by algal growth-inhibition test and morphological observation via transmission electron microscopy (TEM). Results showed that the NiO nanoparticles had severe impacts on the algae, with 72 h EC(50) values of 32.28 mg NiOL(-1). Under the stress of NiO nanoparticles, C. vulgaris cells showed plasmolysis, cytomembrane breakage and thylakoids disorder. NiO nanoparticles aggregated and deposited in algal culture media. The presence of algal cells accelerated aggregation of nanoparticles. Moreover, about 0.14% ionic Ni was released when NiO NPs were added into seawater. The attachment of aggregates to algal cell surface and the presence of released ionic Ni were likely responsible for the toxic effects. Interestingly, some NiO nanoparticles were reduced to zero valence nickel as determined by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis. The maximum ratios of nickel reduction was achieved at 72 h of exposure, in accordance with the time-course of changes in soluble protein content of treated C. vulgaris, implying that some proteins of algae are involved in the process. Our results indicate that the toxicity and bioavailability of NiO nanoparticles to marine algae are reduced by aggregation and reduction of NiO. Thus, marine algae have the potential for usage in nano-pollution bio-remediation in aquatic system.     

Effect of silver nanoparticles in crop plants Phaseolus radiatus and Sorghum bicolor: media effect on phytotoxicity

Understanding some adverse effects of nanoparticles in edible crop plants is a matter of importance because nanoparticles are often released into soil environments. We investigated the phytotoxicity of silver nanoparticles (AgNPs) on the important crop plants, Phaseolus radiatus and Sorghum bicolor. The silver nanoparticles were selected for this study because of their OECD designation as a priority nanomaterial. The toxicity and bioavailability of AgNPs in the crop plant species P. radiatus and S. bicolor were evaluated in both agar and soil media. The seedling growth of test species was adversely affected by exposure to AgNPs. We found evidence of nanoparticle uptake by plants using electron microscopic studies. In the agar tests, P. radiatus and S. bicolor showed a concentration dependent-growth inhibition effect. Measurements of the growth rate of P. radiatus were not affected in the soil studies by impediment within the concentrations tested herein. Bioavailability of nanoparticles was reduced in the soil, and the dissolved silver ion effect also differed in the soil as compared to the agar. The properties of nanoparticles have been shown to change in soil, so this phenomenon has been attributed to the reduced toxicity of AgNPs to plants in soil medium. The application of nanoparticles in soil is a matter of great importance to elucidate the terrestrial toxicity of nanoparticles.     

Antimicrobial activity of metal oxide nanoparticles supported onto natural clinoptilolite

The antimicrobial activity of Cu₂O, ZnO and NiO nanoparticles supported onto natural clinoptilolite was investigated in the secondary effluent under dark conditions. After 24 h of contact the Cu₂O and ZnO nanoparticles reduced the numbers of viable bacterial cells of Escherichia coli and Staphylococcus aureus in pure culture for four to six orders of magnitude and showed consistent 100% of antibacterial activity against native E. coli after 1 h of contact during 48 exposures. The antibacterial activity of NiO nanoparticles was less efficient. The Cu₂O and NiO nanoparticles showed 100% of antiprotozoan activity against Paramecium caudatum and Euplotes affinis after 1 h of contact, while ZnO nanoparticles were less efficient. The morphology and crystallinity of the nanoparticles were not affected by microorganisms. The metal oxide nanoparticles could find a novel application in the disinfection of secondary effluent and removal of pathogenic microorganisms in the tertiary stage of wastewater treatment.     

Chemical and biological oxidative effects of carbon black nanoparticles

Several studies show that ultrafine particles have a larger surface area than coarse particles, thus causing a greater inflammatory response. In this study, we investigated chemical and biological oxidative effects of nanoparticles in vitro. Carbon black (CB) nanoparticles with mean aerodynamic diameters of 14, 56, and 95nm were examined. The innate oxidative capacity of the CB nanoparticles was measured by consumption of dithiothreitol (DTT) in cell-free system. The expression of heme oxygenase-1 (HO-1) in rat alveolar type II epithelial cell line (SV40T2) and alveolar macrophages (AM) exposed to CB nanoparticles was measured by ELISA. DTT consumption of 14nm CB was higher than that of other CB nanoparticles having the same particle weight. However, DTT consumption was directly proportional to the particle surface area. HO-1 protein in SV40T2 cells was significantly increased by the 14nm and 56nm CB, however, 95nm CB did not affect. HO-1 protein in AM was significantly increased by the 14, 56, and 95nm CB. The increase in HO-1 expression was diminished by N-acetyl-l-cysteine (NAC) treatment of each CB nanoparticles before exposure although the difference between the effects of NAC-treated and untreated 14nm CB did not achieve significant. In conclusion, CB nanoparticles have innate oxidative capacity that may be dependent on the surface area. CB nanoparticles can induce oxidative stress in alveolar epithelial cells and AM that is more prominent with smaller particles. The oxidative stress may, at least partially, be mediated by surface function of particles.     

Interaction of engineered nanoparticles with various components of the environment and possible strategies for their risk assessment

Nanoparticles are the materials with at least two dimensions between 1 and 100 nm. Mostly these nanoparticles are natural products but their tremendous commercial use has boosted the artificial synthesis of these particles (engineered nanoparticles). Accelerated production and use of these engineered nanoparticles may cause their release in the environment and facilitate the frequent interactions with biotic and abiotic components of the ecosystems. Despite remarkable commercial benefits, their presence in the nature may cause hazardous biological effects. Therefore, detail understanding of their sources, release interaction with environment, and possible risk assessment would provide a basis for safer use of engineered nanoparticles with minimal or no hazardous impact on environment. Keeping all these points in mind the present review provides updated information on various aspects, e.g. sources, different types, synthesis, interaction with environment, possible strategies for risk management of engineered nanoparticles.     

Carbon black nanoparticles promote the maturation and function of mouse bone marrow-derived dendritic cells

Particulate matter including carbon black (CB) nanoparticles can enhance antigen-related inflammation and immunoglobulin production in vivo. Dendritic cells (DC) as antigen-presenting cells (APC) are the most capable inducers of immune responses. The present study was designed to determine whether CB nanoparticles affect the maturation/activation and function of DC in vitro. DC were differentiated from bone marrow (BM) cells of BALB/c mice by culture with granulocyte macrophage colony stimulating factor (GM-CSF). At day 8 of culture, BM-derived DC (BMDC) were exposed to CB nanoparticles with a diameter of 14nm or 56nm for 24h. The expression of major histocompatibility complex (MHC) class II, DEC205, CD80, and CD86 (maturation/activation markers of BMDC) was measured by flow cytometry. BMDC function was evaluated by an allogeneic mixed lymphocyte reaction (MLR) assay. CB nanoparticles significantly increased the expression of DEC205 and CD86 in BMDC and tended to increase MHC class II and CD80 expression; however, a size-dependent effect was not observed. On the other hand, BMDC-mediated MLR was significantly enhanced by the CB nanoparticles and the enhancement was greater by 14nm CB nanoparticles than by 56nm CB nanoparticles. Taken together, CB nanoparticles can promote the maturation/activation and function of BMDC, which could be related to their effects on allergic diseases and/or responses. In addition, BMDC-mediated MLR might be useful assay for in vitro screening for adjuvant activity of environmental toxicants.     

Photocatalytic degradation of phenol using Ag core-TiO<Subscript>2</Subscript> shell (Ag@TiO<Subscript>2</Subscript>) nanoparticles under UV light irradiation

Ag@TiO₂ nanoparticles were synthesized by one pot synthesis method with postcalcination. These nanoparticles were tested for their photocatalytic efficacies in degradation of phenol both in free and immobilized forms under UV light irradiation through batch experiments. Ag@TiO₂ nanoparticles were found to be the effective photocatalysts for degradation of phenol. The effects of factors such as pH, initial phenol concentration, and catalyst loading on phenol degradation were evaluated, and these factors were found to influence the process efficiency. The optimum values of these factors were determined to maximize the phenol degradation. The efficacy of the nanoparticles immobilized on cellulose acetate film was inferior to that of free nanoparticles in UV photocatalysis due to light penetration problem and diffusional limitations. The performance of fluidized bed photocatalytic reactor operated under batch with recycle mode was evaluated for UV photocatalysis with immobilized Ag@TiO₂ nanoparticles. In the fluidized bed reactor, the percentage degradation of phenol was found to increase with the increase in catalyst loading.     

Growth inhibition of bloom forming cyanobacterium Microcystis aeruginosa by green route fabricated copper oxide nanoparticles

The cyanobacterium Microcystis aeruginosa can potentially proliferate in a wide range of freshwater bionetworks and create extensive secondary metabolites which are harmful to human and animal health. The M. aeruginosa release toxic microcystins that can create a wide range of health-related issues to aquatic animals and humans. It is essential to eliminate them from the ecosystem with convenient method. It has been reported that engineered metal nanoparticles are potentially toxic to pathogenic organisms. In the present study, we examined the growth inhibition effect of green synthesized copper oxide nanoparticles against M. aeruginosa. The green synthesized copper oxide nanoparticles exhibit an excitation of surface plasmon resonance (SPR) at 270 nm confirmed using UV–visible spectrophotometer. The dynamic light scattering (DLS) analysis revealed that synthesized nanoparticles are colloidal in nature and having a particle size of 551 nm with high stability at ?26.6 mV. The scanning electron microscopy (SEM) analysis shows that copper oxide nanoparticles are spherical, rod and irregular in shape, and consistently distributed throughout the solution. The elemental copper and oxide peak were confirmed using energy dispersive x-ray analysis (EDAX). Fourier-transform infrared (FT-IR) spectroscopy indicates the presence of functional groups which is mandatory for the reduction of copper ions. Besides, green synthesized copper oxide nanoparticles shows growth inhibition against M. aeruginosa. The inhibition efficiency was 31.8 % at lower concentration and 89.7 % at higher concentration of copper oxide nanoparticles, respectively. The chlorophyll (a and b) and carotenoid content of M. aeruginosa declined in dose-dependent manner with respect to induction of copper oxide nanoparticles. Furthermore, we analyzed the mechanism behind the cytotoxicity of M. aeruginosa induced by copper oxide nanoparticles through evaluating membrane integrity, reactive oxygen species (ROS), and mitochondrial membrane potential (Δψm) level. The results expose that there is a loss in membrane integrity with ROS formation that leads to alteration in the Δψm, which ends up with severe mitochondrial injury in copper oxide nanoparticles treated cells. Hence, green way synthesized copper oxide nanoparticles may be a useful selective biological agent for the control of M. aeruginosa.     

Decontaminating soil organic pollutants with manufactured nanoparticles

Organic pollutants in soils might threaten the environmental and human health. Manufactured nanoparticles are capable to reduce this risk efficiently due to their relatively large capacity of sorption and degradation of organic pollutants. Stability, mobility, and reactivity of nanoparticles are prerequisites for their efficacy in soil remediation. On the basis of a brief introduction of these issues, this review provides a comprehensive summary of the application and effectiveness of various types of manufactured nanoparticles for removing organic pollutants from soil. The main categories of nanoparticles include iron (oxides), titanium dioxide, carbonaceous, palladium, and amphiphilic polymeric nanoparticles. Their advantages (e.g., unique properties and high sorption capacity) and disadvantages (e.g., high cost and low recovery) for soil remediation are discussed with respect to the characteristics of organic pollutants. The factors that influence the decontamination effects, such as properties, surfactants, solution chemistry, and soil organic matter, are addressed.     

Assessment of silver nanoparticle-induced physiological and molecular changes in Arabidopsis thaliana

In this study, the effect of silver nanoparticles and silver ions on Arabidopsis thaliana was investigated at physiological and molecular levels. The seedlings were grown in sublethal concentrations of silver nanoparticles and silver ions (0.2, 0.5, and 1 mg/L) in 1/4 Hoagland’s medium for 14 days under submerged hydroponic conditions. Significantly higher reduction in the total chlorophyll and increase in anthocyanin content were observed after exposure to 0.5 and 1 mg/L silver nanoparticles as compared to similar concentrations of silver ions. Lipid peroxidation increased significantly after exposure to 0.2, 0.5, and 1 mg/L of silver nanoparticles and 0.5 and 1 mg/L of silver ions. Qualitative analysis with dichloro-dihydro-fluorescein diacetate and rhodamine 123 fluorescence showed a dose-dependent increase in reactive oxygen species production and changes in mitochondrial membrane potential in the roots of seedlings exposed to different concentrations of silver nanoparticles. Real-time PCR analysis showed significant upregulation in the expression of sulfur assimilation, glutathione biosynthesis, glutathione S-transferase, and glutathione reductase genes upon exposure to silver nanoparticles as compared with silver ions. Overall, based on the physiological and molecular level responses, it was observed that exposure to silver nanoparticles exerted more toxic response than silver ions in A. thaliana.     

Metal- and metal/oxide-based engineered nanoparticles and nanostructures: a review on the applications,nanotoxicological effects,and risk control strategies

Environmental Science and Pollution Research - The production and demand of nanoparticles in the manufacturing sector and personal care products, release a large number of engineered nanoparticles...     

Fe3O4／Ag磁性纳米颗粒去除水中的铅离子

采用水相共沉淀法制备小尺寸磁性Fe3O4纳米颗粒,以没食子酸作为还原剂和表面修饰剂,还原Ag[（NH3）2]’制备出Fe3O4／Ag磁性纳米颗粒。研究该磁性纳米颗粒对水溶液中铅离子的吸附行为,研究结果表明,pH为7．0,吸附温度30℃时可得到最好的处理效果,铅的去除率可达99．7％以上,Fe3O4／Ag颗粒吸附行为符合二级动力学模型（R2〉0．99）。该磁性纳米颗粒经过多次再生处理后,仍具有很好的吸附效果,表明Fe3O4／Ag在水处理方面拥有良好的应用前景。