Shape-Persistent Replica Synthesis of Gold/Silver Bimetallic Nanoplates Using Tailored Silica Cages.

Shape-persistent replica synthesis of Au/Ag bimetallic nanoplates is invented. Using a tailored silica cage as a template for the synthesis, a successful shape-replication of Au/Ag bimetallic nanoplate is achieved at the cage core having geometry of initial Ag nanoplate. This work can open up the simple fabrication of multicomponent metallic particles, with nanogeometry being defined early at the initial stage.

Effect of dispersion stability on the deposition of citrate-capped silver nanoparticles in natural soils.

Although little is known about the behavior of engineered nanomaterials after exposure to terrestrial areas, recent studies indicate that silver nanoparticles (AgNPs) can perturb the soil environment due to their biocidal and catalytic properties. The fundamental evaluation of the environmental fate of AgNPs would be a significant step toward a comprehensive understanding of the harmful effects of such particles on ecosystems. Therefore, from an eco-toxicological perspective, the estimation of AgNP behavior in soil should be investigated. Among the various environmental characteristics, the deposition of nanoparticles in the soil constitute is a critical step in their migration into surface or groundwater and interaction with organisms, which is determined by the stability of aqueous dispersions in a soil micro-environment. In the present study, we observed the aggregation and deposition of AgNPs to natural soil surfaces by comparing the partitioning of AgNPs in a soil/water interface with that of Ag+ ion. Both AgNPs and Ag+ ion were selectively quantified by means of inductively coupled plasma (ICP) spectrometry and an ion-selective electrode (ISE). We interpreted the partitioning of AgNPs and Ag+ ion using the Freundlich isotherm and the findings indicate that AgNPs with reduced dispersion stability in a soil micro-environment were aggregated and deposited on the surface of natural soil. This study provides a fundamental basis for understanding the deposition of AgNPs, which will enable their accumulation and mobility in a soil environment to be predicted.

CCR5 plays an important role in resolving an inflammatory response to single-walled carbon nanotubes.

Owing to the development of new materials and technology, the pollutants in the environment are becoming more varied and complex over time. In our previous study using ICR mice, we suggested that a single intratracheal instillation of single-walled carbon nanotubes (SWCNTs) induced early lung fibrosis and subchronic tissue damage. In the present study, to investigate the role of CCR5 in inflammatory responses to the uptake of SWCNTs, we compared BAL (Bronchoalveolar lavage) cell composition, cell cycles, cytokines, cell phenotypes, inflammatory response-related proteins, cell surface receptors and histopathology using CCR5 knockout (KO) and wild-type mice. Results showed that the distribution of neutrophils in BAL fluid significantly decreased in KO mice. The expression of apoptosis-related proteins including caspase-3, p53, phospho-p53, p21 and cleaved PARP, TGF ßl and mesothelin markedly increased in KO mice compared with wild-type mice. Histopathological lesions were also more frequently noted in KO mice. Moreover, the secretion of IL-13 and IL-17 with IL-6 significantly increased in KO mice compared with wild-type mice, whereas that of IL-12 significantly decreased in comparison to wild-type mice. The distribution of B cells and CD8+ T cells was predominant in the inflammatory responses in KO mice, whereas that of T cells and CD4+ T cells was predominant in the inflammatory responses in wild-type mice. Furthermore, the expression of CCR4 and CCR7 significantly increased in KO mice. Based on these results, we suggest that the absence of CCR5 delays the resolution of inflammatory responses triggered by SWCNTs inflowing into the lungs and shifts inflammatory response for SWCNTs clearance from Th1-type to Th2-type.

Functional analyses of nanoparticle toxicity: a comparative study of the effects of TiO2 and Ag on tomatoes (Lycopersicon esculentum).

Engineered nanoparticles (NPs), increasingly used in industry, enter and migrate through biological ecosystems. NPs may create some acute toxicity, but their overall effects on living organisms remain largely unknown. In particular, the behavior of NPs in natural conditions and their consequent ecological effects are still poorly understood. In this study, we developed methods to test the phytotoxicity of two distinctly different NPs, one aerosol (nano-TiO2), and the other colloidal silver (AgNP), by specifically considering their tendencies to agglomerate and form precipitates. First we examined effects of these NPs on germination and root elongation. While exposure to neither of these NPs resulted in acute toxicity on germination, silver NPs caused significantly decreased root elongation at every concentration we tested. We found that the hydrodynamic diameters of AgNPs were much smaller than those of nano-TiO2, which induced higher uptake and phytotoxicity. Based on the agglomeration behavior of the NPs, greenhouse trials were run using commercial soil, for nano-TiO2, and Hoagland's solution, for AgNP. Phytotoxicity of silver NPs in the mature plants was demonstrated by lower chlorophyll contents, higher superoxide dismutase activity and less fruit productivity, while nano-TiO2 resulted in higher superoxide dismutase activity at the highest concentration (5000mg/kg). Both nano-TiO2 and AgNPs were taken up into plant stems, leaves and fruits. Our results suggest that further studies of the ecological effects of nanoparticles and steps to mitigate appropriate management strategies are required.

Sustainable colorimetric/luminescent sensors enabled by armored lipid nanoparticles.

In this study, we developed a highly stable polymeric vesicle using a nanosilica-armor membrane to achieve a sustainable colorimetric/luminescent response. The silica armor can be grown directly as ~ 5 nm spherical nanoparticles on the surface of the diacetylene (DA) vesicle with liposomal structure. This can be accomplished via the modified Stöber reaction in pure water on a layer of amine linkers deposited on the vesicles. Once formed, the structural stability of the DA vesicles dramatically increased and remained so even in a dried powder form that could be stored for a period of approximately 6 months. Then, redispersed in water, the armored vesicles did not agglomerate because of the electric charge of the silica armor. After polymerization, the polydiacetylene (PDA) vesicles maintained an average of 87.4% their sensing capabilities compared to unstored vesicles. Furthermore, the silica membrane thickness can be controlled by reiteration of the electrostatic layer-by-layer approach and the direct hydrolysis of silica. As the number of silica armor membranes increases, the passage of the stimuli passing through the membranes becomes longer. Consequently, three layers of silica armor gave the PDA vesicles size-selective recognition to filter out external stimuli. These discoveries are expected to have large-scale effects in the chemo- and biosensor fields by applying protective layers to organic nanomaterials.

PM 2.5 collected in a residential area induced Th1-type inflammatory responses with oxidative stress in mice.

Epidemiologists have tried to establish an association between human health and exposure to particulate matter (PM). In addition, many researchers have investigated the adverse effects of PM as a trigger of cardiovascular and pulmonary diseases. It is known that a number of environmental contaminants are attached to PM and the toxicity of PM may depend on the sources. We investigated the effects of PM collected in a residential area of Seoul on the immunotoxic responses including cytokine production in BAL fluid and in blood after a single intratracheal instillation in mice with the characterization of physico-chemical properties of PM 2.5 samples. As results, pro-inflammatory cytokines (IL-1, TNF-α, and IL-6), Th0-type cytokine (IL-2), and Th1-type cytokines (IL-12 and IFN-γ) were increased by a dose-dependent manner. Cell infiltration in the alveolar area and phagocytosis by macrophage was observed until day 28 after instillation. The expressions of oxidative stress-related genes (HSP 1a, HSP 8, and SOD) and tissue damage-related genes (MMP-15, -19, and Slpi) were time-dependently increased. PM 2.5 also induced an increase of T cell distribution in lymphocyte and decreased the CD4+/CD8+ ratio. Based on the results, we suggest that PM 2.5 collected in a residential area of Seoul may induce Th1 type-inflammatory responses with oxidative stress and trigger adverse effects in human health.

A single intratracheal instillation of single-walled carbon nanotubes induced early lung fibrosis and subchronic tissue damage in mice.

Large amounts of nanomaterials may reach both the natural and occupational environments. This represents a potential health hazard. People have forecasted that CNTs may lead to the toxicity such as mesothelioma and fibrosis like asbestos. To identify dominant immune responses induced by SWCNTs, we investigated the composition of bronchioalveolar lavage (BAL) cells, the secretion of cytokine and collagen, histopathology, protein expression, and cell phenotypes over time after a single administration of single-walled carbon nanotubes (SWCNT). In our results, the number of total cells and macrophages remained at the up-regulated level until Day 28, neutrophils rapidly increased at Day 1, and lymphocytes increased from Day 7. In the BAL fluid, pro-inflammatory cytokines rapidly increased at Day 1 and remained at an up-regulated level throughout the experimental period. IL-12 and IL-10 rapidly increased at Day 1 after administration and remained at a similar level until Day 28. IFN-γ and IL-4 reached the maximum at Day 1, and IL-5, TGF-ß, and collagen reached the maximum at Day 7. IL-13 and IL-17 increased in a time-dependent manner. The distribution of B cells and cytotoxic T cells markedly increased at Days 7 and 14, and fibrotic lesions were histopathologically observed at Days 7 and 14. The expressions of caspase-3, p53, COL1A1, COX-2, iNOS, MMP-9, and MMP-2 were also markedly increased at Days 7 and 14. In addition, the expression of mesothelin, iNOS, MMP-9, and p53 was up-regulated until Day 28. Based on these findings, we suggest that a single intratracheal instillation of SWCNTs may induce early lung fibrosis and subchronic tissue damage.

Rapid, reversible preparation of size-controllable silver nanoplates by chemical redox.

Citrate-stabilized silver nanoplates (AgNPs) were prepared using a seed-mediated growth method. The AgNP shape and size were controlled using potassium permanganate (KMnO(4)) as an oxidant and ascorbic acid (AA) as a reductant. Using KMnO(4), 42 nm nanoplates were changed to 22.9 nm nanodisks because of the release of silver ions. Using AA, the oxidized AgNPs were resynthesized to their initial plate form. These results are similar to those obtained using photoinduced shape control of silver nanoparticles; however, the chemical oxidation/reduction method can control the shape of AgNPs, both quantitatively and reversibly. In addition, because of redox-related visible spectral changes, solution color varies with AgNPs size. That feature may be useful in various applications.

Dual-fluorophore Raspberry-like Nanohybrids for Ratiometric pH Sensing.

We report on the development of raspberry-like silica structures formed by the adsorption of 8-hydroxypyrene-1,3,6-trisulfonate (HPTS)@silica nanoparticles (NPs) on rhodamine B isothiocyanate (RBTIC)@silica NPs for ratiometric fluorescence-based pH sensing. To overcome the well-known problem of dye leaching which occurs during encapsulation of anionic HPTS dye in silica NPs, we utilized a polyelectrolyte-assisted incorporation of the anionic HPTS. The morphological and optical characterization of the as-synthesized dye-doped NPs and the resulting nanohybrids were carried out. The pH-sensitive dye, HPTS, incorporated in the HPTS-doped silica NPs provided a pH-dependent fluorescence response while the RBITC-doped silica provided the reference signal for ratiometric sensing. We evaluated the effectiveness of the nanohybrids for pH sensing; the ratio of the fluorescence emission intensity at 510 nm and 583 nm at excitation wavelengths of 454 nm and 555 nm, respectively. The results showed a dynamic response in the acidic pH range. With this approach, nanohybrids containing different dyes or receptors could be developed for multifunctioning and multiplexing applications.

Polydiacetylene/Anti-HBs Complexes for Visible and Fluorescent Detection of Hepatitis†B Surface Antigen on a Nitrocellulose Membrane.

The immunochromatographic assay (ICA) using a nitrocellulose (NC) membrane offers several advantages. This technique is a rapid and straightforward method in contrast to other immunoassays. Polydiacetylene (PDA) vesicles have unique optical properties, displaying red color and red fluorescence at the same time. In this system, red-phase PDA vesicles are used as a fluorescent dye as well as a surface for immobilized hepatitis B surface antibody (HBsAb). PDA has a remarkable stability compared with other fluorescent dyes. In this study, the most suitable PDA/HBsAb complexes are introduced for detecting hepatitis B surface antigen (HBsAg). Then, the PDA/HBsAb complexes affixed antibody is attached to NC membrane, which has two lines to confirm detection of HBsAg. The main advantage of this system is that the detection of HBsAg can be observed in both visible and fluorescent images due to the optical properties of polydiacetylene. Detection of HBsAg is observed up to 0.1 ng mL-1 by fluorescent analysis and confirmed by red line on the NC membrane up to 1 ng mL-1 (HBsAg) using the naked eye. Consequently, these results show that PDA/HBsAb complexes were successfully applied to ICA for the diagnosis of hepatitis B.

Functional analysis of TiO2 nanoparticle toxicity in three plant species.

Titanium dioxide nanoparticles (nano-TiO2) are manufactured and used worldwide in large quantities. However, phytotoxicity research on nano-TiO2 has yielded confusing results, ranging from strong toxicity to positive effects. Therefore, in this research, the effects of nano-TiO2 on the germination and root elongation of seed and seedlings were studied. Additionally, the uptake and physiological responses of mature plants were investigated. Physical chemistry data were analyzed to assess the availability of nano-TiO2. Finally, a hydroponic system designed to overcome nano-TiO2 precipitation was used to reproduce the environmental conditions of actual fields. Nano-TiO2 did not have any effect on seed germination or on most of the plant species tested. Nano-TiO2 had positive effects on root elongation in some species. No physiological differences in enzyme activities or chlorophyll content were detected, even though the plants absorbed nano-TiO2. Physical chemistry data showed that nano-TiO2 agglomerated rapidly and formed particles with much bigger hydrodynamic diameters, even in distilled water and especially in a hydroponic system. Furthermore, agglomerated nano-TiO2 formed precipitates; this would be more severe in an actual field. Consequently, nano-TiO2 would not be also readily available to plants and would not cause any significant effects on plants. Our results and other reports suggest that titanium itself is not phytotoxic, even though plants absorb titanium. In conclusion, nano-TiO2 is not toxic to the three plant species, in vitro or in situ.

Removal characteristics of engineered nanoparticles by activated sludge.

Environmental release of engineered nanoparticles (NPs) has been on the rise due to the increased use of NPs in commercial products. In addition, the fate of NPs in sewage treatment processes may play an important role in determining the environmental release pathway of NPs. In this study, we investigated the removal of engineered NPs (AgNPs, TiO2NPs, and SiO2NPs) using activated sludge by evaluating the effects of several important factors of the NPs, including physicochemical properties, contact time between NPs and activated sludge, aquatic chemistry of sewage, and the presence of extracellular polymeric substances (EPS) in the activated sludge. For all three types of NPs tested, a considerable amount of NPs were removed after exposure to activated sludge in a time-dependent manner; nevertheless, the removal efficiencies depended on the type of NPs and seemed to be affected by the NP stability relative to the hydrodynamic diameter (HDD) and zeta potential. In addition, the presences of both ionic compounds and EPS significantly enhanced the NP removal efficiency, indicating that the instability of the NPs resulting from the ionic strength in sewage and entrapment of NP by EPS played an important role in NP removal by activated sludge. These results suggest that the removal efficiencies can be affected by the operating conditions of the activated sludge process and the conditions of the activated sludge; therefore, these factors should be considered when developing approaches to sufficiently remove NPs from sewage treatment plants.

Biological toxicity and inflammatory response of semi-single-walled carbon nanotubes.

The toxicological studies on carbon nanotubes (CNTs) have been urgently needed from the emerging diverse applications of CNTs. Physicochemical properties such as shape, diameter, conductance, surface charge and surface chemistry of CNTs gained during manufacturing processes play a key role in the toxicity. In this study, we separated the semi-conductive components of SWCNTs (semi-SWCNTs) and evaluated the toxicity on days 1, 7, 14 and 28 after intratracheal instillation in order to determine the role of conductance. Exposure to semi-SWCNTs significantly increased the growth of mice and significantly decreased the relative ratio of brain weight to body weight. Recruitment of monocytes into the bloodstream increased in a time-dependent manner, and significant hematological changes were observed 28 days after exposure. In the bronchoalveolar lavage (BAL) fluid, secretion of Th2-type cytokines, particularly IL-10, was more predominant than Th1-type cytokines, and expression of regulated on activation normal T cell expressed and secreted (RANTES), p53, transforming growth factor (TGF)-ß, and inducible nitric oxide synthase (iNOS) increased in a time-dependent manner. Fibrotic histopathological changes peaked on day 7 and decreased 14 days after exposure. Expression of cyclooxygenase-2 (COX-2), mesothelin, and phosphorylated signal transducer and activator of transcription 3 (pSTAT3) also peaked on day 7, while that of TGF-ß peaked on days 7 and 14. Secretion of histamine in BAL fluid decreased in a time-dependent manner. Consequently, we suggest that the brain is the target organ of semi-SWCNTs brought into the lung, and conductance as well as length may be critical factors affecting the intensity and duration of the inflammatory response following SWCNT exposure.

Biological responses to diesel exhaust particles (DEPs) depend on the physicochemical properties of the DEPs.

Diesel exhaust particles (DEPs) are the main components of ambient particulate materials, including polyaromatic hydrocarbons (PAHs), n-PAHs, heavy metals, and gaseous materials. Many epidemiological, clinical, and toxicological studies have shown that ambient particles, including DEPs, are associated with respiratory disorders, such as asthma, allergic rhinitis, and lung cancer. However, the relationship between the biological response to DEPs and their chemical composition remains unclear. In this study, we investigated the physicochemical properties of DEPs before toxicological studies, and then administered a single intratracheal instillation of DEPs to mice. The mice were then killed 1, 7, 14 and 28 days after DEP exposure to observe the biological responses induced by DEPs over time. Our findings suggest that DEPs engulfed into cells induced a Th2-type inflammatory response followed by DNA damage, whereas DEPs not engulfed into cells induced a Th1-type inflammatory response. Further, the physicochemical properties, including surface charge, particle size, and chemical composition, of DEPs play a crucial role in determining the biological responses to DEPs. Consequently, we suggest that the biological response to DEPs depend on cell-particle interaction and the physicochemical properties of the particles.

Induction of Inflammatory Responses by Carbon Fullerene (C60) in Cultured RAW264.7 Cells and in Intraperitoneally Injected Mice.

As the use of carbon fullerene increases in the chemical industry, the concern over its biological and toxicological effects is also increasing. In this study, the suspension of carbon fullerene (C60) in phosphate buffered saline was prepared and toxicity was investigated using cultured RAW 264.7 and in intraperitoneally injected mice, respectively. The average size of carbon fullerene in the suspension was 53.7 ± 26.5 nm when determined by particle size analyzer. Cell viability was significantly decreased by the exposure of carbon fullerene (0.25~2.00 µg/ml) for 96 hrs in the cultured RAW 264.7 cells. Intracellular reduced glutathione (GSH) level was also decreased compared to the level of the non-treated control group during the exposure period, while the level of nitric oxide was increased. When mice were intraperitoneally injected with carbon fullerene, serum cytokine levels of IL-1 and IL-6 were increased with the increased expression of inflammatory genes in peritoneal macrophage and T cell distribution in blood lymphocytes.The results suggested inflammatory responses were induced by carbon fullerene.