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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-β, 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.

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.

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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.

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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.