Resilience of the topological phases to frustration.

Recently it was highlighted that one-dimensional antiferromagnetic spin models with frustrated boundary conditions, i.e. periodic boundary conditions in a ring with an odd number of elements, may show very peculiar behavior. Indeed the presence of frustrated boundary conditions can destroy the local magnetic orders presented by the models when different boundary conditions are taken into account and induce novel phase transitions. Motivated by these results, we analyze the effects of the introduction of frustrated boundary conditions on several models supporting (symmetry protected) topological orders, and compare our results with the ones obtained with different boundary conditions. None of the topological order phases analyzed are altered by this change. This observation leads naturally to the conjecture that topological phases of one-dimensional systems are in general not affected by topological frustration.

Size and mass determination of silver nanoparticles in an aqueous matrix using asymmetric flow field flow fractionation coupled to inductively coupled plasma mass spectrometer and ultraviolet-visible detectors.

The powerful antibacterial properties of engineered silver nanoparticles (AgNPs) have, in recent years, led to a great increase in their use in consumer products such as textiles and personal care products offers. This widespread and often indiscriminate use of nano-silver is inevitably increasing the probability that such materials be accidentally or deliberately lost into the environment. Once present in the environment the normally useful antibacterial properties of the silver may instead become a potential hazard to both man and the environment. In the face of such concerns it therefore desirable to develop easy, reliable and sensitive analytical methods for the determination of nano-sized silver in various matrices. This paper describes a method for the simultaneous determination of particles-size and mass-concentration of citrate-stabilized silver nano-particles in aqueous matrices by asymmetric flow field flow fractionation coupled to an ICP-mass spectrometer and UV/vis detector. In particular, this work has evaluated the use of pre-channel injections of mono-dispersed silver nano-particles as a means of accurate size and mass-calibration. The suitability of the method as a means to generate accurate and reliable results was verified by determination of parameters such as precision under repeatability conditions, linearity, accuracy, recovery and analytical sensitivity.

Comparative study of ZnO and TiO2 nanoparticles: physicochemical characterisation and toxicological effects on human colon carcinoma cells.

Despite human gastrointestinal exposure to nanoparticles (NPs), data on NPs toxicity in intestinal cells are quite scanty. In this study we evaluated the toxicity induced by zinc oxide (ZnO) and titanium dioxide (TiO2) NPs on Caco-2 cells. Only ZnO NPs produced significant cytotoxicity, evaluated by two different assays. The presence of foetal calf serum in culture medium significantly reduced ZnO NPs toxicity as well as ion leakage and NP-cell interaction. The two NPs increased the intracellular amount of reactive oxygen species (ROS) after 6 h treatment. However, only ZnO NPs increased ROS and induced IL-8 release both after 6 and 24 h. Experimental data indicate a main role of chemical composition and solubility in ZnO NPs toxicity. Moreover our results suggest a key role of oxidative stress in ZnO NPs cytotoxicity induction related both to ion leakage and to cell interaction with NPs in serum-free medium.

Size-dependent toxicity and cell interaction mechanisms of gold nanoparticles on mouse fibroblasts.

Gold nanoparticles (AuNPs) are currently used in several fields including biomedical applications, although no conclusive information on their cytotoxicity is available. For this reason this work has investigated the effects of AuNPs in vitro on Balb/3T3 mouse fibroblasts. Results obtained exposing cells for 72 h to AuNPs 5 and 15 nm citrate stabilized, revealed cytotoxic effects only for AuNPs 5 nm at concentration ≥ 50 µM if measured by colony forming efficiency (CFE). To understand the differences in cytotoxicity observed for the two AuNPs sizes, we investigated the uptake and the intracellular distribution of the nanoparticles. By TEM it was observed that 5 and 15 nm AuNPs are internalized by Balb/3T3 cells and located within intracellular endosomal compartments. Quantification of the uptake by ICP-MS showed that AuNPs internalization enhanced even up to 72 h. Disruption of the actin cytoskeleton was evident, with cell footprints narrow and contracted; effects more remarkable in cells exposed to 5 nm AuNP. The mechanism of NPs cell internalization was investigated using immunocytochemistry and western blot. No significant effect was observed in the expression level of caveolin, while reduction of the expression and degradation of the clathrin heavy chain was observed in cells exposed for 72 h to AuNPs.

Lipophilic silver nanoparticles and their polymeric entrapment into targeted-PEG-based micelles for the treatment of glioblastoma.

A simple method for the synthesis of lipophilic Ag NPs have been developed. The coated Ag NPs have been entrapped into a FDA-approved and targetable PEG-based polymeric nanoparticles, and this nanocarrier has been conjugated with the peptide chlorotoxin. Uptake experiments have shown a cell-specific recognition of the Ag-1-PNPs-Cltx on U87MG cell lines in comparison to Balb/3T3. The uptake of Ag into the cells was quantified and an interesting cytotoxic effect (IC50 = 45 µM) has been found on glioblastoma cell lines.

Online monitoring of cell metabolism to assess the toxicity of nanoparticles: the case of cobalt ferrite.

Different in vitro assays are successfully used to determine the relative cytotoxicity of a broad range of compounds. Nevertheless, different research groups have pointed out the difficulty in using the same tests to assess the toxicity of nanoparticles (NPs). In this study, we evaluated the possible use of a microphysiometer, Bionas 2500 analyzing system Bionas GmbH®, to detect in real time changes in cell metabolisms linked to NPs exposure. We focused our work on response changes of fibroblast cultures linked to exposure by cobalt ferrite NPs and compared the results to conventional in vitro assays. The measurements with the microphysiometer showed a cobalt ferrite cytotoxic effect, confirmed by the Colony Forming Efficiency assay. In conclusion, this work demonstrated that the measurement of metabolic parameters with a microphysiometer is a promising method to assess the toxicity of NPs and offers the advantage to follow on-line the cell metabolic changes.

Protein--nanoparticle interaction: identification of the ubiquitin--gold nanoparticle interaction site.

We demonstrate that it is possible to identify the protein--nanoparticle interaction site at amino acid scale in solution. Using NMR, chemical shift perturbation analysis, and dynamic light scattering we have identified a specific domain of human ubiquitin that interacts with gold nanoparticles. This method allows a detailed structural analysis of proteins absorbed onto surfaces of nanoparticles in physiological conditions and it will provide much needed experimental data for better modeling and prediction of protein--nanoparticle interactions.

Colony Forming Efficiency and microscopy analysis of multi-wall carbon nanotubes cell interaction.

In this work, we present a complete physicochemical characterization of multi-wall carbon nanotubes (mwCNTs) in order to assess their potential toxicological effects in in vitro cell models using Colony Forming Efficiency (CFE) assay. We verified that Dimethyl Sulfoxide (DMSO) was a more suitable solvent to disperse mwCNTs compared to culture medium guaranteeing reproducibility in the preparation of testing dilutions. The CFE assay was carried out on five mammalian cell lines representing the potentially exposed and/or target organs for nanomaterials (lung, liver, kidney, intestine, skin), as well as on mouse fibroblasts cell line, which usually is considered a sensitive model to verify in vitro cytotoxicity of test compounds. A statistically significant toxic effect was found only in human alveolar basal epithelial cells and immortalized mouse fibroblasts, for which the interaction between mwCNTs and cells was additionally studied by Atomic Force and Scanning Electron Microscopy. In this study, we considered and suggested the CFE assay as a promising test for screening studies of cytotoxicity. In addition, combining in vitro tests with physicochemical analysis, this work underlines basic points to be considered when research on nanomaterials has to be carried out, to set up, in our opinion, well-defined and suitable experimental planning and procedures.

Horizon in random matrix theory, the Hawking radiation, and flow of cold atoms.

We propose a Gaussian scalar field theory in a curved 2D metric with an event horizon as the low-energy effective theory for a weakly confined, invariant random matrix ensemble (RME). The presence of an event horizon naturally generates a bath of Hawking radiation, which introduces a finite temperature in the model in a nontrivial way. A similar mapping with a gravitational analogue model has been constructed for a Bose-Einstein condensate (BEC) pushed to flow at a velocity higher than its speed of sound, with Hawking radiation as sound waves propagating over the cold atoms. Our work suggests a threefold connection between a moving BEC system, black-hole physics and unconventional RMEs with possible experimental applications.

Genotoxicity and morphological transformation induced by cobalt nanoparticles and cobalt chloride: an in vitro study in Balb/3T3 mouse fibroblasts.

Nanotechnology is an emerging field that involves the development, manufacture and measurement of materials and systems in the submicron to nanometer range. Its development is expected to have a large socio-economical impact in practically all fields of industrial activity. However, there is still a lack of information about the potential risks of manufactured nanoparticles for the environment and for human health. In this work, we studied the cytotoxicity, genotoxicity and morphological transforming activity of cobalt nanoparticles (Co-nano) and cobalt ions (Co(2+)) in Balb/3T3 cells. We also evaluated Co-nano dissolution in culture medium and cellular uptake of both Co-nano and Co(2+). Our results indicated dose-dependent cytotoxicity, assessed by colony-forming efficiency test, for both compounds. The toxicity was higher for Co-nano than for Co(2) after 2 and 24 h of exposure, while dose-effect relationships were overlapping after 72 h. Statistically significant results were observed for Co-nano with the micronucleus test and the comet assay, while for Co(2+) positive results were observed only with the latter. In addition, even when Co-nano was genotoxic (at >1 microM), no evident dose-dependent effect was observed. Concerning morphological transformation, we found a statistically significant increase in the formation of type III foci (morphologically transformed colonies) only for Co-nano. Furthermore, we observed a higher cellular uptake of Co-nano compared with Co(2+).

Modeling 13C breath curves to determine site and extent of starch digestion and fermentation in infants.

BACKGROUND: The colon salvages energy from starch, especially when the capacity of the small intestine to digest it is limited. The aim of this study was to determine the site and relative extent of starch digestion and fermentation in infants. METHODS: Thirteen infants (10 male and 3 female infants), median age 11.8 months (range, 7.6-22.7 months), were fed a starchy breakfast containing 13C-labeled wheat flour after an overnight fast. Duplicate breath samples were obtained before breakfast and every 30 minutes for 12 hours. Breath 13CO2 enrichment was measured using isotope ratio mass spectrometry, and results were expressed as percentage dose recovered (PDR) for each 30 minutes. The PDR data were analyzed and mathematically modeled assuming either a constant estimate of CO2 production rate or adjusted for physical activity. RESULTS: Mean +/- SD cumulative 13C PDR (cPDR) at 12 hours was 21.3% +/- 8.4% for unadjusted data and 26.5% +/- 11.6% for adjusted data. A composite model of two curves fit significantly better than a single curve. Modeling allowed estimation of cPDRs of small intestine (17.5% +/- 6.5% and 22.7% +/- 9.3% for unadjusted and adjusted data, respectively) and colon (4.6% +/- 2.9% and 6.3% +/- 5.4%). CONCLUSIONS: Modeling of 13CO2 enrichment curves after ingestion of 13C-enriched wheat flour is an attractive means to estimate the contribution of the upper and lower gut to starch digestion and fermentation.