Uiseok Jeong

Au nanoparticle-embedded SiO2–Au@SiO2 catalysts with improved catalytic activity, enhanced stability to metal sintering and excellent recyclability

Synthesizing a precious metal catalyst with high performance and excellent recyclability is always an important issue in catalysis. Here, we report a synthetic strategy for preparing gold nanoparticle (Au NP)-embedded SiO2 particles for use as recyclable nanocatalysts. Au NP-embedded SiO2 (SiO2–Au@SiO2) particles were synthesized by applying a Au NP decoration on the surface of the SiO2 particles and additional SiO2 coating through a sol–gel reaction. In order to improve molecule accessibility, catalyst stability and catalytic performance, post-treatments such as calcination and/or etching with water or ammonia were carried out. A systematic study of the physical property changes of the resulting SiO2–Au@SiO2 samples with variations of each synthetic step revealed that the parameters that are very important for determining the catalytic performance, namely Au NP stability, porosity and capping agents on the Au surface, are strongly influenced by each post-treatment step. In particular, calcination followed by etching with ammonia enables the production of a highly active SiO2–Au@SiO2 catalyst with highly dispersed Au NPs in the silica layer, a surfactant-free Au surface and an improved porosity of the silica layer, which displays significantly enhanced catalytic performance and excellent recyclability as compared to SiO2–Au and as-synthesized SiO2–Au@SiO2.

Hierarchical-like multipod γ-MnS microcrystals: solvothermal synthesis, characterization and growth mechanism

Novel hierarchical multipod γ-MnS microcrystals have been successfully synthesized by a simple solvothermal method, in which manganese acetate was used as a manganese source and thiosemicarbazide was used as both sulfur source and capping agent.

Biodistribution and toxicity of spherical aluminum oxide nanoparticles.

With the rapid development of the nano‐industry, concerns about their potential adverse health effects have been raised. Thus, ranking accurately their toxicity and prioritizing for in vivo testing through in vitro toxicity test is needed. In this study, we used three types of synthesized aluminum oxide nanoparticles (AlONPs): γ‐aluminum oxide hydroxide nanoparticles (γ‐AlOHNPs), γ‐ and α‐AlONPs. All three AlONPs were spherical, and the surface area was the greatest for γ‐AlONPs, followed by the α‐AlONPs and γ‐AlOHNPs. In mice, γ‐AlOHNPs accumulated the most 24 h after a single oral dose. Additionally, the decreased number of white blood cells (WBC), the increased ratio of neutrophils and the enhanced secretion of interleukin (IL)‐8 were observed in the blood of mice dosed with γ‐AlOHNPs (10 mg kg−1). We also compared their toxicity using four different in vitro test methods using six cell lines, which were derived from their potential target organs, BEAS‐2B (lung), Chang (liver), HACAT (skin), H9C2 (heart), T98G (brain) and HEK‐293 (kidney). The results showed γ‐AlOHNPs induced the greatest toxicity. Moreover, separation of particles was observed in a transmission electron microscope (TEM) image of cells treated with γ‐AlOHNPs, but not γ‐AlONPs or α‐AlONPs. In conclusion, our results suggest that the accumulation and toxicity of AlONPs are stronger in γ‐AlOHNPs compared with γ‐AlONPs and α‐AlONPs owing their low stability within biological system, and the presence of hydroxyl group may be an important factor in determining the distribution and toxicity of spherical AlONPs. Copyright

Single-walled carbon nanotubes disturbed the immune and metabolic regulation function 13-weeks after a single intratracheal instillation.

Due to their unique physicochemical properties, the potential health effects of single-walled carbon nanotubes (SWCNTs) have attracted continuous attention together with their extensive application. In this study, we aimed to identify local and systemic health effects following pulmonary persistence of SWCNTs. As expected, SWCNTs remained in the lung for 13 weeks after a single intratracheal instillation (50, 100, and 200μg/kg). In the lung, the total number of cells and the percentages of lymphocytes and neutrophils significantly increased at 200μg/kg compared to the control, and the Th1-polarized immune response was induced accompanying enhanced expression of tissue damage-related genes and increased release of chemokines. Additionally, SWCNTs enhanced the expression of antigen presentation-related proteins on the surface of antigen-presenting cells, however, maturation of dendritic cells was inhibited by their persistence. As compared to the control, a significant increase in the percentage of neutrophils and a remarkable decrease of BUN and potassium level were observed in the blood of mice treated with the highest dose. This was accompanied by the down-regulation of the expression of antigen presentation-related proteins on splenocytes. Moreover, protein and glucose metabolism were disturbed with an up-regulation of fatty acid β-oxidation. Taken together, we conclude that SWCNTs may induce adverse health effects by disturbing immune and metabolic regulation functions in the body. Therefore, careful application of SWCNTs is necessary for the enforcement of safety in nano-industries.

Comparison of distribution and toxicity of different types of zinc-based nanoparticles.

Zinc‐based nanoparticles (Zn‐NPs), mainly zinc oxide (ZnO) NPs, have promising application in a wide area, but their potential harmful effects on environment and human health have been continuously raised together with their high dissolution rate. In this study, we coated the surface of ZnO NPs with phosphate (ZnP NPs) and sulfide (ZnS NPs) which have very low solubility in water, administered orally (0.5 and 1 mg/kg) to mice for 28 days, and then compared their biodistribution and toxicity. As expected, ZnO NPs were rapidly ionized in an artificial gastric fluid. On the other hand, ZnO NPs were more particlized in an artificial intestinal fluid than ZnP and ZnS NPs. After repeated dosing, all three types of Zn‐NPs the most distributed in the spleen and thymus and altered the level of redox reaction‐related metal ions in the tissues. We also found that three types of Zn‐NPs clearly disturb tissue ion homeostasis and influence immune regulation function. However, there were no remarkable difference in distribution and toxicity following repeated exposure of three types of Zn‐NPs, although Na+ and K+ level in the spleen and thymus were notably higher in mice exposed to ZnO NPs compared to ZnP and ZnS NPs. Taken together, we suggest that all three types of Zn‐NPs may influence human health by disrupting homeostasis of trace elements and ions in the tissues. In addition, the surface transformation of ZnO NPs with phosphate and sulfide may not attenuate toxicity due to the higher particlization rate of ZnO NPs in the intestine, at least in part.

A higher aspect ratio enhanced bioaccumulation and altered immune responses due to intravenously-injected aluminum oxide nanoparticles

Abstract Aluminum oxide nanoparticles (AlO NP) have been widely utilized in a variety of areas, including in the optical, biomedical and electronic fields and in the overall development of nanotechnologies. However, their toxicological profiles are still not fully developed. This study compared the distribution and immunotoxicity of two rod-types of AlO NP. As reported previously, the two types of AlO NP had different aspect ratios (long-type: 6.2 ± 0.6, short-type: 2.1 ± 0.4), but the size and surface charge were very similar. On Day 14 after a single intravenous (IV) injection (1.25 or 5 mg/kg), both AlO NP accumulated primarily in the liver and spleen and altered the levels of redox response-related elements. The accumulated level was higher in mice exposed to the long-type AlO NP compared to the short-type. Additionally, it was noted that the levels of IL-1β, IL-8 and MCP-1 were enhanced in the blood of mice exposed to both types of AlO NP and the percentages of neutrophils and monocytes among all white blood cells were increased only in mice injected with the long-type AlO NP (5 mg/kg). In addition, as compared to the control, co-expression of CD80 and CD86 (necessary for antigen presentation) on splenocytes together with a decreased expression of chemotaxis-related marker (CD195) was attenuated by exposure to the AlO NP, especially the long-type. Taken together, the data suggest that accumulation following a single IV injection with rod-types of AlO NP is strengthened by a high aspect ratio and, subsequently, this accumulation has the potential to influence immune functions in an exposed host.

Subchronic immunotoxicity and screening of reproductive toxicity and developmental immunotoxicity following single instillation of HIPCO-single-walled carbon nanotubes: purity-based comparison

Abstract Impurity has been suggested as an important factor determining toxicity following exposure to single-walled carbon nanotubes (SWCNTs). In this study, we first compared immunotoxicity based on iron content on day 90 after a single intratracheal instillation of SWCNTs in male and female mice. The inflammatory responses were generally stronger in mice exposed to acid-purified (P)-SWCNTs compared to raw (R)-SWCNTs. In addition, both R- and P-SWCNTs induced Th1-polarized immune responses with apoptotic death of BAL cells and systemically impaired the function of antigen-presenting cells (APC). We also screened reproductive and developmental toxicity by cohabitating male and female mice on day 14 after instillation. Interestingly, the pregnancy rate rapidly decreased following exposure to both types of SWCNTs, especially R-SWCNTs. In addition, we investigated developmental immunotoxicity of the offspring on day 28 after exposure to both types of SWCNTs. Their hematological changes were clearer relative to those of the parents and a significant decrease in the alkaline phosphatase and potassium levels was observed in mice of both sexes exposed to the higher dose of R- and P-SWCNTs. In conclusion, we suggest that SWCNTs may induce Th1-polarized immune responses accompanied by suppression of APC function on day 90 after a single instillation without significant iron content dependance. In addition, the consecutive exposure of SWCNTs to the subsequent generation may exacerbate metabolic and hematological disturbance. Furthermore, our results underscore the need to clarify the reproductive and developmental health effects of SWCNTs.

Tissue distribution following 28 day repeated oral administration of aluminum‐based nanoparticles with different properties and the in vitro toxicity

The tissue distribution and toxicity of nanoparticles (NPs) depend on their physical and chemical properties both in the manufactured condition and within the biological system. We characterized three types of commercially available aluminum‐based NPs (Al‐NPs), two rod‐type aluminum oxide NPs (Al2O3, AlONPs), with different aspect ratios (short [S]‐ and long [L]‐AlONPs), and spherical aluminum cerium oxide NPs (AlCeO3, AlCeONPs). The surface area was in order of the S‐AlONPs > L‐AlONPs > AlCeONPs. Very importantly, we found that AlCeONPs is Al2O3‐coated CeO2 NPs, but not AlCeO3 NPs, and that the Al level in AlCeONPs is approximately 20% of those in S‐ and L‐AlONPs. All three types of Al‐NPs were slightly ionized in gastric fluid and rapidly particlized in the intestinal fluid. There were no significant differences in the body weight gain following 28 days of repeated oral administration of the three different types of Al‐NPs. All Al‐NPs elevated Al level in the heart, spleen, kidney and blood at 24 hours after the final dose, accompanied by the altered tissue level of redox reaction‐related trace elements. Subsequently, in four types of cells derived from the organs which Al‐NPs are accumulated, H9C2 (heart), HEK‐293 (kidney), splenocytes and RAW264.7 (blood), S‐AlONPs showed a very low uptake level and did not exert significant cytotoxicity. Meanwhile, cytotoxicity and uptake level were the most remarkable in cells treated with AlCeONPs. In conclusion, we suggest that the physicochemical properties of NPs should be examined in detail before the release into the market to prevent unexpected adverse health effects.

Nano-sized iron particles may induce multiple pathways of cell death following generation of mistranscripted RNA in human corneal epithelial cells

Iron is closely associated with an ambient particulate matters-induced inflammatory response, and the cornea that covers the front of the eye, is among tissues exposed directly to ambient particulate matters. Prior to this study, we confirmed that nano-sized iron particles (FeNPs) can penetrate the cornea. Thus, we identified the toxic mechanism of FeNPs using human corneal epithelial cells. At 24h after exposure, FeNPs located inside autophagosome-like vacuoles or freely within human corneal epithelial cells. Level of inflammatory mediators including nitric oxide, cytokines, and a chemokine was notably elevated accompanied by the increased generation of reactive oxygen species. Additionally, cell proliferation dose-dependently decreased, and level of multiple pathways of cell death-related indicators was clearly altered following exposure to FeNPs. Furthermore, expression of gene encoding DNA binding protein inhibitor (1, 2, and 3), which are correlated to inhibition of the binding of mistranscripted RNA, was significantly down-regulated. More importantly, expression of p-Akt and caspase-3 and conversion to LC3B-II from LC3B-I was enhanced by pretreatment with a caspase-1 inhibitor. Taken together, we suggest that FeNPs may induce multiple pathways of cell death via generation of mistranscripted RNA, and these cell death pathways may influence by cross-talk. Furthermore, we propose the need of further study for the possibility of tumorigenesis following exposure to FeNPs.

Magnetically-Separable and Thermally-Stable Au Nanoparticles Encapsulated in Mesoporous Silica for Catalytic Applications

Here, we report a synthetic strategy for fabricating silica-encapsulated gold nanoparticles (Au NPs) on magnetic particle (Fe3O4@SiO2-Au@mSiO2) for use as a magnetically-separable, thermally-stable, and easily recyclable catalyst in liquid phase reactions. Fe3O4@SiO2-Au@mSiO2 samples were prepared by synthesizing a Fe3O4@SiO2 core–shell particle followed by decoration with the Au NPs and additional mesoporous silica coating. The prepared Fe3O4@SiO2-Au@mSiO2 catalysts showed advantageous characteristics for liquid phase reaction, which are superparamagnetic properties for easy separation and recycling, the well-developed mesoporosity on the outer surface for facile diffusion of reactant molecules, and high resistance on thermal sintering of Au NPs. The resulting core–shell-type catalysts showed improved performance in terms of catalytic stability and recyclability for multiple reaction runs. In particular, the Fe3O4@SiO2-Au@mSiO2-H2O catalyst, which is treated with additional water etching, showed optimal properties such as improved molecular accessibility and Au stability, resulting in the best catalytic performance seen in this study.