Effects of silica nanoparticles on endolysosome function in primary cultured neurons 1.

Silica nanoparticles (SiNPs) have been used as vehicles for drug delivery, molecular detection, and cellular manipulations in nanoneuromedicine. SiNPs may cause adverse effects in the brain including neurotoxicity, neuroinflammation, neurodegeneration, and enhancing levels of amyloid beta (Aß) protein-all pathological hallmarks of Alzheimer's disease. Therefore, the extent to which SiNPs influence Aß generation and the underlying mechanisms by which this occurs deserve investigation. Our studies were focused on the effects of SiNPs on endolysosomes which uptake, traffic, and mediate the actions of SiNPs. These organelles are also where amyloidogenesis largely originates. We found that SiNPs, in primary cultured hippocampal neurons, accumulated in endolysosomes and caused a rapid and persistent deacidification of endolysosomes. SiNPs significantly reduced endolysosome calcium stores as indicated by a significant reduction in the ability of the lysosomotropic agent glycyl-l-phenylalanine 2-naphthylamide (GPN) to release calcium from endolysosomes. SiNPs increased Aß1-40 secretion, whereas 2 agents that acidified endolysosomes, ML-SA1 and CGS21680, blocked SiNP-induced deacidification and increased generation of Aß1-40. Our findings suggest that SiNP-induced deacidification of and calcium release from endolysosomes might be mechanistically linked to increased amyloidogenesis. The use of SiNPs might not be the best nanomaterial for therapeutic strategies against Alzheimer's disease and other neurological disorders linked to endolysosome dysfunction.

SiNPs induce ferroptosis in HUVECs through p38 inhibiting NrF2 pathway.

Introduction: Despite of growing evidence linking silica nanoparticles (SiNPs), one of the global-top-three-produced and -used nanoparticle (NP), to human health risks, there remain many knowledge gaps over the adverse effects of SiNPs exposure on cardiovascular system and the underlying molecular mechanisms. Methods: In this study, the ferroptotic effects of SiNPs (20 nm; 0, 25, 50, and 100 µg/mL) on human umbilical vein endothelial cells (HUVECs) and the possible molecular mechanism were studied with the corresponding biochemical and molecular biology assays. Results and discussion: The results showed that at the tested concentrations, SiNPs could decrease HUVEC viability, but the deferoxamine mesylate (an iron ion chelator) might rescue this reduction of cell viability. Also, increased levels of intracellular reactive oxygen species and enhanced mRNA expression of lipid oxidation enzymes (ACSL4 and LPCAT3) with increase in lipid peroxidation (malondialdehyde), but decreased ratios of intracellular GSH/total-GSH and mitochondrial membrane potential as well as reduced enzymatic activities of anti-oxidative enzymes (CAT, SOD, and GSH-PX), were found in the SiNPs-treated HUVECs. Meanwhile, increase in p38 protein phosphorylation and decrease in NrF2 protein phosphorylation with reduced mRNA expressions of downstream anti-oxidative enzyme genes (CAT, SOD1, GSH-PX, and GPX4) was identified in the SiNPs-exposed HUVECs. These data indicated that SiNPs exposure might induce ferroptosis in HUVECs via p38 inhibiting NrF2 pathway. Ferroptosis of HUVECs will become a useful biomarker for assessing the cardiovascular health risks of environmental contaminants.

A survey on virtualization of Wireless Sensor Networks.

Wireless Sensor Networks (WSNs) are gaining tremendous importance thanks to their broad range of commercial applications such as in smart home automation, health-care and industrial automation. In these applications multi-vendor and heterogeneous sensor nodes are deployed. Due to strict administrative control over the specific WSN domains, communication barriers, conflicting goals and the economic interests of different WSN sensor node vendors, it is difficult to introduce a large scale federated WSN. By allowing heterogeneous sensor nodes in WSNs to coexist on a shared physical sensor substrate, virtualization in sensor network may provide flexibility, cost effective solutions, promote diversity, ensure security and increase manageability. This paper surveys the novel approach of using the large scale federated WSN resources in a sensor virtualization environment. Our focus in this paper is to introduce a few design goals, the challenges and opportunities of research in the field of sensor network virtualization as well as to illustrate a current status of research in this field. This paper also presents a wide array of state-of-the art projects related to sensor network virtualization.

Foliar application of silica sol alleviates boron toxicity in rice (Oryza sativa) seedlings.

Boron (B) toxicity is one of the limiting factors affecting plant growth. Previous studies showed that silicon (Si) application could alleviate B toxicity. However, there is limited information on how Si alleviates B toxicity in rice, particularly nano-silicon (SiNP). Therefore, the current study aimed to explore the foliar function of SiNP in the reduction of B toxicity in rice. The results showed that B toxicity significantly hampered root and shoot development. However, SiNP application increased root and shoot lengths by 14.29% and 29.67%, respectively, compared to B toxicity treatment. Moreover, SiNP increased fresh weight (FW) of root (28.02%) and shoot (34%) and enhanced dry weight (DW) of root (65.13%), and shoot (26.87%), compared to B toxicity treatment. The application of SiNP decreased the translocation of B to leaves and promoted B adsorption to leaf cell wall. In roots, SiNP triggered high B accumulation and Fourier infrared spectroscopy (FTIR) also suggested higher peak values of functional groups (pectin), indicating that cell wall polysaccharides can adsorb high concentration of B. Atomic Force Microscopy (AFM) and Transmission Electron Microscopy (TEM) investigations showed that SiNP treated roots had a well-arranged structure of alkali-soluble pectin (ASP), and ultrastructure of root was well organized. Cell wall adsorbed more than 80% of total B. All of these results suggest that SiNP can alleviate B toxicity in rice seedlings.

Silicon Nanoparticles Enhance Ginger Rhizomes Tolerance to Postharvest Deterioration and Resistance to Fusarium solani.

Postharvest deterioration of ginger rhizome caused by microorganisms or wound infections causes significant economic losses. Fusarium solani is one of the important causal agents of prevalent ginger disease soft rot across the world. The massive and continuous use of chemical fungicides in postharvest preservation pose risks to human health and produce environmental contamination. Hence, new alternative tools are required to reduce postharvest deterioration and extend the postharvest life of ginger. In this study, the use of silicon nanoparticles (SiNPs) on the storability of ginger rhizomes during postharvest storage and their resistance to Fusarium solani was investigated. The results showed that 50, 100, and 150 mg L-1 of SiNPs increased the firmness of the ginger rhizome during storage but decreased the decay severity, water loss, total color difference, and the reactive oxygen species (ROS; H2O2 and superoxide anion) accumulation. Specifically, 100 mg L-1 (SiNP100) demonstrated the best effect in the extension of postharvest life and improved the quality of the ginger rhizomes. SiNP100 application increased the activities of antioxidant enzymes (SOD and CAT) and the total phenolics and flavonoid contents, thereby reducing the ROS accumulation and malondialdehyde (MDA) content. Meanwhile, SiNP100 treatment negatively impacts the peroxidase (POD) and polyphenol oxidase (PPO) activities, which may have contributed to the lower level of lignin and decreased total color difference. SiNP100 likely decreased water loss and the transfer of water by altering the expression of aquaporin genes. Moreover, SiNP100 modulated the expression of lignin synthesis and phytopathogenic responses genes including MYB and LysM genes. Furthermore, SiNP100 inhibited Fusarium solani by preventing the penetration of hyphae into cells, thus decreasing the severity of postharvest pathogenic decay. In summary, this study revealed the physiology and molecular mechanisms of SiNPs-induced tolerance to postharvest deterioration and resistance to disease, which provides a foundation for using SiNPs resources as a promising alternative tool to maintain ginger quality and control postharvest diseases.

Transport of nutrients from the Seybouse River to Annaba Bay (Algeria, SW Mediterranean).

Freshwater and dissolved nutrient inputs that entered the lower Seybouse River estuary were assessed in 2012 through a fortnightly surface water sampling both at a lower river station and at the estuary outlet. The Seybouse estuary delivered annually 950 × 106 m3 of freshwater yielding 83 kg N km-2 yr-1 of N-NH4 and 12 kg P km-2 yr-1 of P-PO4. More than 2/3 of the annual inputs of freshwater, Si(OH)4 and NO3 entered the sea during the flooding event of late February 2012. Si-Si(OH)4 and N-NO3 yields in the Seybouse estuary represented <1/3 those of the Mediterranean rivers. Annaba Bay is subjected to highly polluted waters from the Seybouse estuary, with significant NH4 (72 ± 37 µmol L-1) and PO4 (7 ± 4 µmol L-1) amounts. However it is characterized by low Si(OH)4 (104 ± 43 µmol L-1) amounts. Alteration of Si:N:P ratios at this bay suggest potential risk of eutrophication, except during and weeks after flood episodes.

The size-dependent genotoxicity and oxidative stress of silica nanoparticles on endothelial cells.

Concerns over the health risk of the widely distributed, commonly used silica nanoparticles (SiNPs) are increasing worldwide. Yet, up to now, there are still many major knowledge gaps over the potential adverse effects of SiNP exposure on human cardiovascular health and the underlying mechanisms. In this study, comet assay and micronucleus test were employed to determine the genotoxic potentials of four sizes (10, 25, 50, 100 nm) of SiNPs to human umbilical vein endothelial cells (HUVECs) in culture. The intracellular redox statuses were explored through the determination of the levels of reactive oxygen species (ROS) and reduced glutathione (GSH) with kits, respectively. The protein levels of nuclear factor erythroid 2-related factor 2 (Nrf2) were also detected by Western blot. The results showed that at the administrative levels (1, 5, 25 µg/mL), all the four sizes of SiNPs could induce an increase of both DNA damages and MN frequencies in HUVECs in culture, with a positive dose- and negative size-dependent effect relationship (S100 < S50 < S25 < S10). Also, significantly enhanced levels of intracellular ROS, but decreased levels of GSH, were observed in the SiNP-treated groups. Interestingly, a very similar manner of dose- and size-dependent effect relationship was observed between the ROS test and both comet assay and MN test, but contrary to that of GSH assay. Correspondingly, the levels of Nrf2 protein were also enhanced in the SiNP-treated HUVECs, with a negative size-dependent effect relationship. These results implicated that induction of oxidative stress and subsequent genotoxicity may be an important biological mechanism by which SiNP exposure may affect human cardiovascular health.

The size-dependent effects of silica nanoparticles on endothelial cell apoptosis through activating the p53-caspase pathway.

With the growing production and applications of silica nanoparticles (SiNPs), human exposure to these nanoparticles continues to increase. However, the possible hazards that SiNP exposure may pose to human cardiovascular system and the underlying mechanisms remain unclear. In the present study, the flow cytometry was employed to investigate the potential of four sizes (10, 25, 50, 100 nm) of SiNPs to induce the apoptosis of human umbilical vein endothelial cells (HUVECs) in culture. The apoptotic pathway was also explored through the determination of the protein expression and/or activation of p53, Bcl-2, Bax, caspases-9, -7, -3, and PARP by western blot. The results showed that all the four sizes of SiNPs could significantly elicit apoptosis in HUVECs at the tested concentrations (1, 5, 25 µg/mL), compared with the negative control (p < 0.05, p < 0.01). Moreover, the apoptotic rates were increased with the elevating levels and decreasing sizes of administrative SiNPs, showing both dose- and size-dependent effect relationships. Interestingly, the enhancing phosphorylation of p53 protein (Ser15), decreasing ratio of Bcl-2/Bax protein, and elevating activation of the downstream proteins, caspase-9, -7, -3 and PARP, were also observed with the decreasing sizes of tested SiNPs, indicating that the p53-caspase pathway is the main way of the SiNP-mediated apoptosis in HUVECs and that the size is an important parameter that determines the SiNPs' potential to induce cellular response.

Silicon nanoparticles (SiNp) alleviate chromium (VI) phytotoxicity in Pisum sativum (L.) seedlings.

The present study was aimed to investigate the effect of silicon nanoparticles (SiNp) against Cr (VI) phytotoxicity in pea seedlings. Results show that Cr(VI, 100 µM) significantly (P < 0.05) declined growth of pea which was accompanied by the enhanced level of Cr. Additionally, photosynthetic pigments and chlorophyll fluorescence parameters like F(v)/F(m), F(v)/F0 and qP were decreased while NPQ significantly (P < 0.05) increased under Cr(VI) treatment. Superoxide radical, hydrogen peroxide and malondialdehyde (MDA-lipid peroxidation) contents were enhanced by Cr(VI). Activities of antioxidant enzymes like superoxide dismutase and ascorbate peroxidase were increased by Cr (VI) while activities of catalase, glutathione reductase and dehydroascorbate reductase were inhibited significantly (P < 0.05). Micro and macronutrients also show decreasing trends (except S) under Cr(VI) treatment. However, addition of SiNp together with Cr(VI) protects pea seedlings against Cr(VI) phytotoxicity hence improved growth was noticed. In conclusion, the results of this study show that Cr(VI) causes negative impact on pea seedlings, however; SiNp protects pea seedlings against Cr(VI) phytotoxicity by reducing Cr accumulation and oxidative stress, and up-regulating antioxidant defense system and nutrient elements.

Optical imaging of absorption and distribution of RITC-SiO2 nanoparticles after oral administration.

PURPOSE: In this study, we investigated the absorption and distribution of rhodamine B isothiocyanate (RITC)-incorporated silica oxide nanoparticles(SiNPs) (RITC-SiNPs) after oral exposure, by conducting optical imaging, with a focus on tracking the movement of RITC-SiNPs of different particle size and surface charge. METHODS: RITC-SiNPs (20 or 100 nm; positively or negatively charged) were used to avoid the dissociation of a fluorescent dye from nanoparticles via spontaneous or enzyme-catalyzed reactions in vivo. The changes in the nanoparticle sizes and shapes were investigated in an HCl solution for 6 hours. RITC-SiNPs were orally administered to healthy nude mice at a dose of 100 mg/kg. Optical imaging studies were performed at 2, 4, and 6 hours after oral administration. The mice were sacrificed at 2, 4, 6, and 10 hours post-administration, and ex vivo imaging studies were performed. RESULTS: The RITC-SiNPs were stable in the HCl solution for 6 hours, without dissociation of RITC from the nanoparticles and without changes in size and shape. RITC-SiNPs flowed into the small intestine from the stomach and gradually moved along the gut during the experiment. In the ex vivo imaging studies, optical signals were observed mostly in the lungs, liver, pancreas, and kidneys. The orally administered RITC-SiNPs, which were absorbed in the systemic circulation, were eliminated from the body into the urine. The 20 nm RITC-SiNPs showed higher uptake in the lungs than the 100 nm RITC-SiNPs. The distribution of the 100 nm RITC-SiNPs in the liver was higher than that of the 20 nm RITC-SiNPs, but the differences in the surface charge behavior were imperceptible. CONCLUSION: We demonstrated that the movement of RITC-SiNPs after oral exposure could be traced by optical imaging. Optical imaging has the potential to provide valuable information that will help in understanding the behavior of SiNPs in the body following exposure.