Search

The ultimate goal of our study is to establish thin-layer chromatography (TLC) as a quick and simple method for identifying the type of refined petroleum products present in the environmental media. As a preliminary step, TLC chromatograms of different petroleum products, including gasoline, kerosene, and diesel, were characterized and compared. Methanol was determined as the optimum carrier solution in TLC analysis. The spherical-shaped TLC chromatogram of gasoline showed the longest migration distance, and thus the highest retardation factor ( R ) of 0.91. This was followed by that of kerosene (0.63) with an elliptical-shaped, and diesel (0.24) with an elongated trapezoid-shaped chromatogram. R of kerosene and diesel increased with the dilution factor, while gasoline showed a constant value. Additionally, it was observed that the TLC chromatograms of oils produced the same peak pattern with the corresponding petroleum products in gas chromatography (GC). A mixed sample of kerosene and diesel presented a triangular shaped chromatogram, underlining the need to consider the shape of chromatogram in addition to the R value, as an indicator of the petroleum type. The findings indicate that TLC has a huge potential to be used as a quick and reliable method for identifying the type of refined petroleum products in the environmental media. [ABSTRACT FROM AUTHOR]

Highlights: [•] The bioaccumulation of TiO2 NPs was strongly influenced by the extrinsic properties of NPs. [•] New sets of effective dosimetry parameters were suggested for TiO2 NPs. [•] The effective dosimetry parameters well correlated with bioaccumulated NPs. [Copyright &y& Elsevier]

The effects of UV-A on the toxicity of TiO2 nano-particles (NPs) were evaluated using Moina macrocopa and Daphnia magna under environmentally relevant level of UV-A. The waterfleas were exposed to TiO2 NPs with different sizes of ~298nm, ~132nm, or ~72nm for up to 48h, with or without UV-A light. Whole body reactive oxygen species and transcription of antioxidant enzyme genes were measured, as well as the survival of the waterflea. In the presence of UV-A, the survival rates of M. macrocopa significantly decreased in concentration dependent way until ~1mg/L TiO2 NPs, but the survivals were reversed at greater concentrations. This peculiar non-monotonic trend of concentration–response relationship might be explained by changes of particle size under different light conditions. TiO2 NPs within a certain size range could be trapped in the filter apparatus and exert toxicity, and the NPs of greater size were subject to either precipitation or ingestion leading to no or little toxicity. Observed TiO2 toxicity was associated with oxidative stress in the filter apparatus. The results of this study showed that the size change due to UV-A irradiation should be considered in evaluation of ecological risks of TiO2 NP. [Copyright &y& Elsevier]

The extrinsic physicochemical properties of nanoparticles (NPs), such as hydrodynamic size, surface charge, surface functional group, and colloidal stabilities, in toxicity testing media are known to have a significant influence on in vitro toxicity assessments. Therefore, interpretation of nanotoxicity test results should be based on reliable characterization of the NPs' extrinsic properties in actual toxicity testing media. Here, we present a set of physicochemical characterization results for commercially available ZnO NPs, including core diameter, hydrodynamic diameter, surface charges, and colloidal stabilities, in two in vitro toxicity testing media (Roswell Park Memorial Institute [RPMI] and Dulbecco's Modified Eagle's Medium [DMEM]), as well as simple cell viability assay results for selected ZnO NPs. Four commercially available and manufactured ZnO NPs, with different core sizes, were used in this study, and their surface charge was modified with five different surface coating materials (sodium citrate, tris(2-aminoethyl)amine, poly(acrylic acid), poly(allylamine hydrochloride), and poly-L-lysine hydrochloride). The results showed that ZnO NPs were better dispersed in cell culture media via surface modification with positively or negatively charged molecules. Moreover, in the presence of fetal bovine serum (FBS) in RPMI and DMEM media, ZnO NPs were found even better dispersed for a longer period (at least 48 hours). For the HeLa cells exposed to ZnO NPs in DMEM media without FBS, surface charge-dependent cytotoxicity trends were observed, while these trends were not observed for those cells cultured in FBS-containing media. This confirmed the important roles of surface-modifying compounds and of surface charge on the resultant cytotoxicities of NPs.

Background: Titanium dioxide (TiO(2)) has been widely used in many areas, including biomedicine, cosmetics, and environmental engineering. Recently, it has become evident that some TiO(2) particles have a considerable cytotoxic effect in normal human cells. However, the molecular basis for the cytotoxicity of TiO(2) has yet to be defined., Methods and Results: In this study, we demonstrated that combined treatment with TiO(2) nanoparticles sized less than 100 nm and ultraviolet A irradiation induces apoptotic cell death through reactive oxygen species-dependent upregulation of Fas and conformational activation of Bax in normal human cells. Treatment with P25 TiO(2) nanoparticles with a hydrodynamic size distribution centered around 70 nm (TiO(2) (P25-70)) together with ultraviolet A irradiation-induced caspase-dependent apoptotic cell death, accompanied by transcriptional upregulation of the death receptor, Fas, and conformational activation of Bax. In line with these results, knockdown of either Fas or Bax with specific siRNA significantly inhibited TiO(2)-induced apoptotic cell death. Moreover, inhibition of reactive oxygen species with an antioxidant, N-acetyl-L-cysteine, clearly suppressed upregulation of Fas, conformational activation of Bax, and subsequent apoptotic cell death in response to combination treatment using TiO(2) (P25-70) and ultraviolet A irradiation., Conclusion: These results indicate that sub-100 nm sized TiO(2) treatment under ultraviolet A irradiation induces apoptotic cell death through reactive oxygen species-mediated upregulation of the death receptor, Fas, and activation of the preapoptotic protein, Bax. Elucidating the molecular mechanisms by which nanosized particles induce activation of cell death signaling pathways would be critical for the development of prevention strategies to minimize the cytotoxicity of nanomaterials.