Effects of Four Kinds of Oxide Nanoparticles on Proteins in Extracellular Polymeric Substances of Sludge.
ABSTRACT: Proteins are the most important component in sludge extracellular polymeric substances (EPS) and play a crucial role in the formation of sludge flocs, adsorption performance of sludge, and flocculation ability of sludge. This research is aimed at exploring the changes in proteins in EPS extracted from concentrated sludge after various nanoparticle (NP) treatments. The results showed that the protein content in EPS decreased by 40% after nanoalumina (Al2O3 NPs) treatment but increased at varying degrees after nanoferric oxide (Fe3O4 NPs), nanozinc oxide (ZnO NPs), and nanotitanium dioxide (TiO2 NPs) treatments. The four kinds of nanoparticles not only affected the protein content in EPS but also influenced the types and structures of proteins. The results of three-dimensional fluorescence spectroscopy showed that the tyrosine-like protein content in soluble EPS (SEPS) decreased after treatments with four kinds of NPs. Infrared spectroscopy analysis revealed that the absorption intensity of amide I and amide II weakened after Al2O3 NP treatment, whereas that of amide I enhanced after Fe3O4 NP, ZnO NP, and TiO2 NP treatments. Further analysis of the secondary structure of proteins in the infrared range of 1700-1600?cm-1 demonstrated that the value of ?-helix/(?-sheet+random coil) decreased from 0.513 to 0.383 in SEPS after TiO2 NP treatment. For the samples treated by Fe3O4 NPs, the percentage of ?-helix significantly increased and that of ?-sheet slightly decreased in proteins from SEPS and loosely bound EPS.
Project description:The unregulated discharge of nanoparticles (NPs) from various nanotechnology industries into the environment is expected to alter the composition and physiological functions of soil microbiota. Considering this knowledge gap, the impact of five NPs (Ag, ZnO, CuO, Al2O3, and TiO2) differing in size and morphology on growth behavior and physiological activity of Azotobacter chroococcum, Bacillus thuringiensis, Pseudomonas mosselii, and Sinorhizobium meliloti were investigated. Various biochemical and microscopic approaches were adopted. Interestingly, all bacterial strains were found sensitive to Ag-NPs and ZnO-NPs but showed tolerance toward CuO, Al2O3, and TiO2-NPs. The loss of cellular respiration due to NPs was coupled with a reduction in population size. ZnO-NPs at 387.5 ?g mL-1 had a maximum inhibitory impact on A. chroococcum and reduced its population by 72%. Under Ag-NP stress, the reduction in IAA secretion by bacterial strains followed the order S. meliloti (74%) > P. mosselii (63%) > A. chroococcum (49%). The surface of bacterial cells had small- or large-sized aggregates of NPs. Also, numerous gaps, pits, fragmented, and disorganized cell envelopes were visible. Additionally, a treated cell surface appeared corrugated with depressions and alteration in cell length and a strong heterogeneity was noticed under atomic force microscopy (AFM). For instance, NPs induced cell roughness for P. mosselii followed the order 12.6 nm (control) > 58 nm (Ag-NPs) > 41 nm (ZnO-NPs). TEM analysis showed aberrant morphology, cracking, and disruption of the cell envelope with extracellular electron-dense materials. Increased permeability of the inner cell membrane caused cell death and lowered EPS production. Ag-NPs and ZnO-NPs also disrupted the surface adhering ability of bacteria, which varied with time and concentration of NPs. Conclusively, a plausible mechanism of NP toxicity to bacteria has been proposed to understand the mechanistic basis of ecological interaction between NPs and resourceful bacteria. These results also emphasize to develop strategies for the safe disposal of NPs.
Project description:Engineered aluminum oxide (Al2O3), titanium dioxide (TiO2), and silicon dioxide (SiO2) nanoparticles (NPs) are utilized in a broad range of applications; causing noticeable quantities of these materials to be released into the environment. Issues of how and where these particles are distributed into the subsurface aquatic environment remain as major challenges for those in environmental engineering. In this study, transport and retention of Al2O3, TiO2, and SiO2 NPs through various saturated porous media were investigated. Vertical columns were packed with quartz-sand, limestone, and dolomite grains. The NPs were introduced as a pulse suspended in aqueous solutions and breakthrough curves in the column outlet were generated using an ultraviolet-visible spectrophotometer. It was found that Al2O3 and TiO2 NPs are easily transported through limestone and dolomite porous media whereas NPs recoveries were achieved two times higher than those found in the quartz-sand. The highest and lowest SiO2-NPs recoveries were also achieved from the quartz-sand and limestone columns, respectively. The experimental results closely replicated the general trends predicted by the filtration and DLVO calculations. Overall, NPs mobility through a porous medium was found to be strongly dependent on NP surface charge, NP suspension stability against deposition, and porous medium surface charge and roughness.
Project description:Polymerase chain reaction (PCR) is used as an in vitro model system of DNA replication to assess the genotoxicity of nanoparticles (NPs). Prior results showed that several types of NPs inhibited PCR efficiency and increased amplicon error frequency. In this study, we examined the effects of various metal oxide NPs on inhibiting PCR, using high- vs. low-fidelity DNA polymerases; we also examined NP-induced DNA mutation bias at the single nucleotide level. The effects of seven major types of metal oxide NPs (Fe2O3, ZnO, CeO2, Fe3O4, Al2O3, CuO, and TiO2) on PCR replication via a low-fidelity DNA polymerase (Ex Taq) and a high-fidelity DNA polymerase (Phusion) were tested. The successfully amplified PCR products were subsequently sequenced using high-throughput amplicon sequencing. Using consistent proportions of NPs and DNA, we found that the effects of NPs on PCR yield differed depending on the DNA polymerase. Specifically, the efficiency of the high-fidelity DNA polymerase (Phusion) was significantly inhibited by NPs during PCR; such inhibition was not evident in reactions with Ex Taq. Amplicon sequencing showed that the overall error rate of NP-amended PCR was not significantly different from that of PCR without NPs (p > 0.05), and NPs did not introduce single nucleotide polymorphisms during PCR. Thus, overall, NPs inhibited PCR amplification in a DNA polymerase-specific manner, but mutations were not introduced in the process.
Project description:The effect of surface or lattice modification of nanoparticles (NPs) on terrestrial plants is poorly understood. We investigated the impact of different zinc oxide (ZnO) NPs on green pea (Pisum sativum L.), one of the highest consumed legumes globally. Pea plants were grown for 65 d in soil amended with commercially available bare ZnO NPs (10 nm), 2 wt% alumina doped (Al2O3@ZnO NPs, 15 nm), or 1 wt% aminopropyltriethoxysilane coated NPs (KH550@ZnO NP, 20 nm) at 250 and 1000 mg NP/kg soil inside a greenhouse. Bulk (ZnO) and ionic Zn (zinc chloride) were included as controls. Plant fresh and dry biomass, changes in leaf pigment concentrations, elements (Zn, Al, Si), and protein and carbohydrate profile of green pees were quantified upon harvest at 65 days. With the exception of the coated 1000 mg/kg NP treatment, fresh and dry weight were unaffected by Zn exposure. Although, all treated plants showed higher tissue Zn than controls, those exposed to Al2O3@ZnO NPs at 1000 mg/kg had greater Zn concentration in roots and seeds, compared to bulk Zn and the other NP treatments, keeping Al and Si uptake largely unaffected. Higher Zn accumulation in green pea seeds were resulted in coated ZnO at 250 mg/kg treatments. In leaves, Al2O3@ZnO NP at 250 mg/kg significantly increased Chl-a and carotenoid concentrations relative to the bulk, ionic, and the other NP treatments. The protein and carbohydrate profiles remained largely unaltered across all treatments with the exception of Al2O3@ZnO NPs at 1000 mg/kg where sucrose concentration of green peas increased significantly, which is likely a biomarker of stress. Importantly, these findings demonstrate that lattice and surface modification can significantly alter the fate and phytotoxic effects of ZnO NPs in food crops and seed nutritional quality. To the authors' knowledge, this is the first report of a life cycle study on comparative toxicity of bare, coated, and doped ZnO NPs on a soil-grown food crop.
Project description:To further explore and differentiate the biotoxicity mechanisms of individual nanoparticles (NPs) and NP mixture on Nitrosomonas europaea (N. europaea, ATCC 19718) at genetic level, a genome-sequenced model ammonia oxidizing bacterium (AOB) commonly detected in the activated sludge of biological wastewater treatment plants, the induced whole-genome expressions were analyzed with the high throughput Microarray technique, after the dose-dependent changes of N. europaea’s physiological, metabolic and AMO enzyme activities in single and dual component NP systems was evaluated. NP stress induced gene expressions were measured after 6hr exposure to 10 ppm nano-ZnO, 50 nano-TiO2 and their mixture.Three independent experiments were performed for each experiment.
Project description:Most artificial nanomaterials are known to exhibit broad-spectrum bactericidal activity; however, the defence mechanisms that bacteria use based on extracellular polymeric substances (EPS) to detoxify nanoparticles (NPs) are not well known. We ruled out the possibility of ion-specific bactericidal activity by showing the lack of equivalent dissolved zinc and silicon toxicity and determined the particle-specific toxicity of ZnO and SiO2 nanoparticles (ZnONPs/SiO2NPs) through dialysis isolation experiments. Surprisingly, the manipulation of the E. coli EPS (i.e., no EPS manipulation or EPS removal by sonication/centrifugation) showed that their particle-specific bactericidal activity could be antagonized by NP-EPS sequestration. The survival rates of pristine E. coli (no EPS manipulation) reached 65% (ZnONPs, 500?mg L(-1)) and 79% (SiO2NPs, 500?mg L(-1)), whereas survival rates following EPS removal by sonication/centrifugation were 11% and 63%, respectively. Transmission electron microscopy (TEM) combined with fluorescence micro-titration analysis and Fourier-transform infrared spectroscopy (FTIR) showed that protein-like substances (N-H and C-N in amide II) and secondary carbonyl groups (C=O) in the carboxylic acids of EPS acted as important binding sites that were involved in NP sequestration. Accordingly, the amount and composition of EPS produced by bacteria have important implications for the bactericidal efficacy and potential environmental effects of NPs.
Project description:Nanoparticle (NP) association with macromolecules in a physiological environment forms a biocorona (BC), which alters NP distribution, activity, and toxicity. While BC formation is dependent on NP physicochemical properties, little information exists on the influence of the physiological environment. Obese individuals and those with cardiovascular disease exist with altered serum chemistry, which is expected to influence BC formation and NP toxicity. We hypothesize that a BC formed on NPs following incubation in hyperlipidemic serum will result in altered NP-BC protein content, cellular association, and toxicity compared to normal serum conditions. We utilized Fe3O4 NPs, which are being developed as MRI contrast and tumor targeting agents to test our hypothesis. We used rat aortic endothelial cells (RAECs) within a dynamic flow in vitro exposure system to more accurately depict the in vivo environment. A BC was formed on 20nm PVP-suspended Fe3O4 NPs following incubation in water, 10% normal or hyperlipidemic rat serum. Addition of BCs resulted in increased hydrodynamic size and decreased surface charge. More cholesterol associated with Fe3O4 NPs after incubation in hyperlipidemic as compared with normal serum. Using quantitative proteomics, we identified unique differences in BC protein components between the 2 serum types. Under flow conditions, formation of a BC from both serum types reduced RAECs association of Fe3O4 NPs. Addition of BCs was found to exacerbate RAECs inflammatory gene responses to Fe3O4 NPs (Fe3O4-hyperlipidemic?>?Fe3O4-normal?>?Fe3O4) including increased expression of IL-6, TNF-?, Cxcl-2, VCAM-1, and ICAM-1. Overall, these findings demonstrate that disease-induced variations in physiological environments have a significant impact NP-BC formation, cellular association, and cell response.
Project description:Titanium dioxide nanoparticles (TiO2 NPs) constitute the top five NPs in use today. A recent study determined that oral administration of TiO2 NPs increases plasma glucose in mice. In the current study, RNA sequencing (RNA-seq) technology was used to investigate genome-wide effects of TiO2 NPs. Clustering analysis of the RNA-seq data showed the most significantly enriched gene ontology terms and KEGG pathways related to the endoplasmic reticulum (ER) and ER stress. Molecular biology verification showed that TiO2 NPs activated a xenobiotic biodegradation response and increased expression of cytochrome P450 family genes in mouse livers, thus inducing ER stress in mice. ER stress activated MAPK and NF-B pathways and induced an inflammation response, resulting in phosphorylation of the insulin receptor substrate 1 and, consequently, insulin resistance. This was the main mechanism by which TiO2 NPs increased plasma glucose in mice. Meanwhile, ER stress disturbed the monooxygenase system, and thus generated reactive oxygen species (ROS). Relief of ER stress with 4-phenylbutyric acid inhibited all the above effects of TiO2 NPs, including the generation of ROS. Therefore, TiO2 NP-induced ER stress was a decisive factor with a central role in plasma glucose disturbance in mice. Overall design: Examination of genome-wide expressions in Control and NP groups
Project description:The development of noninvasive imaging techniques for the accurate diagnosis of progressive hepatocellular carcinoma (HCC) is of great clinical significance and has always been desired. Herein, a hepatocellular carcinoma cell-targeting fluorescent magnetic nanoparticle (NP) was obtained by conjugating near-infrared fluorescence to the surface of Fe3O4 (NIRF-Fe3O4) NPs, followed by coating the lipids consisting of tumoral hepatocytes-targeting polymer (Gal-P123). This magnetic NP (GPC@NIRF-Fe3O4) with superparamagnetic behavior showed high stability and safety in physiological conditions. In addition, GPC@NIRF-Fe3O4 achieved more specific uptake of human liver cancer cells than free Fe3O4 NPs. Importantly, with superpara-magnetic iron oxide and strong NIR absorbance, GPC@NIRF-Fe3O4 NPs demonstrate prominent tumor-contrasted imaging performance both on fluorescent and T2-weighted magnetic resonance (MR) imaging modalities in a living body. The relative MR signal enhancement of GPC@NIRF-Fe3O4 NPs achieved 5.4-fold improvement compared with NIR-Fe3O4 NPs. Therefore, GPC@ NIRF-Fe3O4 NPs may be potentially used as a candidate for dual-modal imaging of tumors with information covalidated and directly compared by combining fluorescence and MR imaging.
Project description:Besides cell death, nanoparticles (Nps) can induce other cellular responses such as inflammation. The potential immune response mediated by the exposure of human lymphoid cells to metal oxide Nps (moNps) was characterized using four different moNps (CeO2, TiO2, Al2O3, and ZnO) to study the three most relevant mitogen-activated protein kinase subfamilies and the nuclear factor kappa-light-chain-enhancer of the activated B-cell inhibitor, I?B?, as well as the expression of several genes by immune cells incubated with these Nps. The moNps activated different signaling pathways and altered the gene expression in human lymphocyte cells. The ZnO Nps were the most active and the release of Zn2+ ions was the main mechanism of toxicity. CeO2 Nps induced the smallest changes in gene expression and in the I?B? protein. The effects of the particles were strongly dependent on the type and concentration of the Nps and on the cell activation status prior to Np exposure.