Chan Jin

Cellular Toxicity of TiO2 Nanoparticles in Anatase and Rutile Crystal Phase

Titanium dioxide nanoparticles are massively produced and widely used in daily life, which has posed potential risk to human health. However, the molecular mechanism of TiO2 nanoparticles (NPs) with different crystal phases is not clear. In this study, the characterization of two crystalline phases of TiO2 NPs is evaluated by transmission electron microscopy and X-ray absorption fine structure spectrum; an interaction of these TiO2 NPs with HaCaT cells is studied in vitro using transmission electron microscopy, chemical precipitation method, and X-ray absorption fine structure spectrometry. The coordination and surface properties indicate that only the anatase–TiO2 NPs allow spontaneous reactive oxygen species (ROS) generation, but rutile–TiO2 NPs do not after dispersion. The interaction between TiO2 NPs and cellular components might also generate ROS for both anatase–TiO2 NPs and rutile–TiO2 NPs. The ROS generation could lead to cellular toxicity if the level of ROS production overwhelms the antioxidant defense of the cell or induces the mitochondrial apoptotic mechanisms. Furthermore, Ti had a direct combination with some protein or DNA after NPs enter the cell, which could also lead to cellular toxicity.

Cytotoxicity of silica nanoparticles on HaCaT cells

Despite the widespread use of silica nanoparticles (SiO2 NPs) in biological and medical fields, their adverse effects have not been clearly elucidated. In this study, spherical SiO2 NPs with a 50 nm diameter were used to study their interaction with HaCaT cells. SiO2 NPs were found to be readily internalized into HaCaT cells and localized in the cytoplasm, lysosomes and autophagosomes. Decreased cell viability and damaged cell membrane integrity showed the cytotoxicity of SiO2 NPs. Significant glutathione depletion and reactive oxygen species generation, which reduced the cellular antioxidant level, could be the major factor of cytotoxicity induced by SiO2 NPs. Copyright

Mitochondrial injury induced by nanosized titanium dioxide in A549 cells and rats.

The nanosized titanium dioxide (nano-TiO2) is an important nanoscale compound applied in many different fields because of its superior performance. Here, an anatase nano-TiO2 showed cytotoxicity in a dosage-dependent manner, which was in accordance with changes of A549 cell ultrastructure, A549 cell viability and intracellular ATP level. The lungs of rats treated with single intratracheal instillation of nano-TiO2 were injured, which was demonstrated by changes of alveolar epithelial cell ultrastructure, lung tissue pathology and lung tissue MDA level. The results of this study indicated that nano-TiO2 should be related to the generation of intracellular reactive oxygen species (ROS), which injured mitochondria and prevented the synthesis of ATP. The cells were approaching to apoptosis eventually. In macroscopic view, the lungs inevitably suffered.

Direct methylation of N-methylaniline with CO2/H2 catalyzed by gold nanoparticles supported on alumina

Small gold nanoparticles (∼3 nm) loaded onto various supports have been prepared by a deposition–precipitation method and studied for direct methylation of N-methylaniline with CO2/H2. Among the catalysts examined, an acid–base bifunctional support γ-alumina supported gold catalyst (Au/γ-Al2O3) exhibits the best catalytic performance. Au/γ-Al2O3 catalysts with controlled mean Au particle sizes (1.8–8.3 nm) have also been successfully prepared by regulating the concentration of HAuCl4 in solution, aging time, aging temperature and mole ratio of urea to gold in the process of deposition–precipitation with urea. The turnover frequency (TOF) values for direct methylation of N-methylaniline with CO2/H2 increase on decreasing the mean size of Au nanoparticles (from 8.3 to 1.8 nm), showing that methylation of N-methylaniline with CO2/H2 is a structure-sensitive reaction. A fast increase in TOF occurs when the mean Au particle size becomes smaller than 3 nm. Through TEM (transmission electron microscope), gold L3-edge XAFS (X-ray absorption fine structure) and CO2- and NH3-TPD (temperature programmed desorption) analysis, we can conclude the Au particle sizes, oxidation state of the gold species and acid–base properties of the supports are responsible for the high catalytic activity of direct methylation of N-methylaniline with CO2/H2.

Distribution of Graphene Oxide and TiO2-Graphene Oxide Composite in A549 Cells

Graphene and its derivatives are increasingly applied in nanoelectronics, biosensing, drug delivery, and biomedical applications. However, the information about its cytotoxicity remains limited. Herein, the distribution and cytotoxicity of graphene oxide (GO) and TiO2-graphene oxide composite (TiO2-GO composite) were evaluated in A549 cells. Cell viability and cell ultrastructure were measured. Our results indicated that GO could enter A549 cells and located in the cytoplasm and nucleus without causing any cell damage. TiO2 nanoparticles and GO would be separated after TiO2-GO composite entered A549 cells. TiO2-GO composite could induce cytotoxicity similar to TiO2 nanoparticles, which was probably attributed to oxidative stress. These results should be considered in the development of biological applications of GO and TiO2-GO composite.

Noninjection facile synthesis of Gram-scale highly luminescent CdSe multipod nanocrystals.

Nearly all reported approaches for synthesis of high quality CdSe nanocrystals (NCs) involved two steps of preparation of Cd or Se stock solution in advance and then mixing the two reactants via hot-injection in high temperature. In this manuscript, Gram-scale CdSe multipod NCs were facilely synthesized in a noninjection route with the use of CdO and Se powder directly as reactants in paraffin reaction medium containing small amount of oleic acid and trioctylphosphine. The influence of various experimental variables, including reaction temperature, nature and amount of surfactants, Cd-to-Se ratio, and the nature of reactants, on the morphology of the obtained CdSe NCs have been systematically investigated. After deposition of ZnS shell around the CdSe multipod NCs, the PL QY of the obtained CdSe/ZnS can be up to 85%. The reported noninjection preparation approach can satisfy the requirement of industrial production bearing the advantage of low-cost, reproducible, and scalable. Furthermore, this facile noninjection strategy provides a versatile route to large-scale preparation of other semiconductor NCs with multipod or other morphologies.

In vivo evaluation of the interaction between titanium dioxide nanoparticle and rat liver DNA

Titanium dioxide nanoparticles (TiO2 NPs) are massively produced and widely used in daily life, which may pose potential risk to human health via uncharacterized interaction between DNAs. This research aims to examine the interaction between DNA and three types of TiO2 NPs of different sizes and crystallines. The interaction between TiO2 NPs and liver DNA molecules obtained from Sprague-Dawley rats was systematically evaluated in vivo using atomic force microscopy, transmission electron microscopy, various spectroscopic techniques and gel electrophoresis. We found that TiO2 NPs (diameter <25 nm and <100 nm) in anatase crystalline can covalently interact with liver DNA by either inserting itself in between DNA base pairs or binding to DNA nucleotide via P–O–Ti–O bond. Such interaction may not be NP size-dependent but may be crystalline phase-dependent, because such interaction did not occur in rutile crystal phase, in which the DNA damage was potentially caused by reactive oxygen species.

Isobaric yield ratios in heavy-ion reactions, and symmetry energy of neutron-rich nuclei at intermediate energies

The isobaric yield ratios of the fragments produced in the neutron-rich (48)Ca and (64)Ni projectile fragmentation are analyzed in the framework of a modified Fisher model. The correlations between the isobaric yield ratios (R) and the energy coefficients in the Weiszacker-Beth semiclassical mass formula (the symmetry-energy term a(sym), the Coulomb-energy term a(c), and the pairing-energy term a(p)) and the difference between the chemical potentials of the neutron and proton (mu(n) - mu(p)) are investigated. Simple correlations between (mu(n) - mu(p))/T, a(c)/T, a(sym)/T, and a(p)/T (where T is the temperature), and ln R are obtained. It is suggested that (mu(n) - mu(p))/T, a(c)/T, a(sym)/T, and a(p)/T of neutron-rich nuclei can be extracted using isobaric yield ratios for heavy-ion collisions at intermediate energies.

Effects of fullerene C60 nanoparticles on A549 cells

Fullerene C60 nanoparticles (C60 NPs) have been widely applied in many fields due to their excellent physical and chemical properties. As production and applications of C60 NPs expand, public concern about the potential risk to human health has also risen. The toxicity of C60 NPs was evaluated by the CCK-8 assay using the cultured human epithelial cell line A549. Cellular uptake of the C60 NPs was observed by TEM imaging. In our findings, C60 NPs could readily enter A549 cells and showed no significant toxicity. Exposure of cultured A549 cells to C60 NPs led to an increase of intracellular reactive oxygen species (ROS) while glutathione reductase activity was probably activated to generate more GSH to maintain a cellular oxidation-reduction equilibrium. The A549 cells responded to the ROS increases through the inauguration of autophagic responses, aimed at restoring cellular health and equilibrium.

Efficient Hydrogenation of Alkyl Formate to Methanol over Nanocomposite Copper/Alumina Catalysts

The production of methanol, an important fuel and chemical feedstock, from carbon dioxide is an important process for CO2 utilization. We describe herein a mild and efficient method for the indirect hydrogenation of carbon dioxide to methanol via a CO2‐derived formate ester intermediate by using a simple heterogeneous catalyst system comprising Cu highly dispersed in an alumina matrix under solvent‐free conditions. This catalyst is also effective for the hydrogenation of other formate esters, such as ethyl formate, propyl formate, and butyl formate.