Maria Lucia Miglietta

Toxic effects of ZnO nanoparticles towards marine algae Dunaliella tertiolecta.

Dose response curve and population growth rate alterations of marine Chlorophyte Dunaliella tertiolecta derived from the exposure to ZnO nanoparticles were evaluated. Bulk ZnO and ionic zinc were also investigated for comparison. At the same time, the aggregation state and particle size distribution were monitored. The evaluated 50% effect concentration (EC50 1.94 [0.78-2.31] mg Zn L(-1)) indicates that nano ZnO is more toxic than its bulk counterpart (EC50 3.57 [2.77-4.80] mg Zn L(-1)). Cross-referencing the toxicity parameters calculated for ZnCl(2) (EC50 0.65 [0.36-0.70] mg Zn L(-1)) and the dissolution properties of the ZnO, it can be gathered that the higher toxicity of nano ZnO is most likely related to the peculiar physicochemical properties of the nanostate with respect to the bulk material. Furthermore growth rate of D. tertiolecta was significantly affected by nano ZnO exposure. Our findings suggest that the primary particle size of the dispersed particles affect the overall toxicity.

Investigation of ZnO nanoparticles’ ecotoxicological effects towards different soil organisms

IntroductionNanomaterials have widespread applications in several industrial sectors. ZnO nanoparticles (NPs) are among the most commonly used metal oxide NPs in personal care products, coating and paints. However, their potential toxicological impact on the environment is largely unexplored.Materials and methodsThe aim of this work was to evaluate whether ZnO nanoparticles exert toxic and genotoxic effects upon terrestrial organisms: plants (Lepidium sativum, Vicia faba), crustaceans (Heterocyipris incongruens), insects (Folsomia candida). To achieve this purpose, organisms pertaining to different trophic levels of the soil ecosystem have been exposed to ZnO NPs. In parallel, the selected soil organisms have been exposed to the same amount of Zn in its ionic form (Zn2+) and the effects have been compared.ResultsThe most conspicuous effect, among the test battery organisms, was obtained with the ostracod H. incongruens, which was observed to be the most sensitive organism to ZnO NPs. The root elongation of L. sativum was also mainly affected by exposure to ZnO NPs with respect to ZnCl2, while collembolan reproduction test produced similar results for both Zn compounds. Slight genotoxic effects with V. faba micronucleus test were observed with both soils.ConclusionNanostructured ZnO seems to exert a higher toxic effect in insoluble form towards different terrestrial organisms with respect to similar amounts of zinc in ionic form.

Embryotoxicity and spermiotoxicity of nanosized ZnO for Mediterranean sea urchin Paracentrotus lividus.

The effect of nano ZnO (nZnO) upon the fertilization and early development of embryos of the Mediterranean sea urchin Paracentrotus lividus is reported herein for the first time. Zn ion (ZnCl2) and bulk ZnO (bZnO) toxicity were assessed for comparison. The embryotoxicity tests showed a 100% effect already at 1 μM of nZnO (expressed as [Zn]) while bZnO and ZnCl2 showed EC50s of 0.98 [0.88-1.19] μM [Zn] and 2.02 [1.97-2.09] μM [Zn], respectively. Noteworthy, the frequency of developmental defects for the three compounds was dissimilar and a specific trend for larval skeletal abnormality produced by nZnO was observed. The sperm fertilization capability was only slightly affected by the tested chemicals while the effects were dramatic on the offspring quality of sperms exposed to ZnO compounds resulting in an early block of the regular larval development. ZnO toxicity seems related not only to Zinc ions but also to some surface interactions of particle/aggregates with target organisms and/or with the seawater.

Geographical origin of durum wheat studied by 1H-NMR profiling

1H‐Nuclear magnetic resonance (NMR) spectroscopy was used to detect metabolic profiles of wheat flour samples of different geographical and botanical origin. The NMR profiles were analyzed by multivariate statistical techniques in order to establish the origin of the samples. A linear model, able to discriminate among three different locations, was built achieving a prediction level of about 80% of correctly assigned samples. The principal classes of compounds responsible for the geographic origin discrimination were individuated in aromatic compounds and amino acids. The statistical modeling also indicated that botanical origin information is very poor in the NMR profiles of the analyzed wheat samples. Copyright

A study on the physicochemical properties of hydroalcoholic solutions to improve the direct exfoliation of natural graphite down to few-layers graphene

Straightforward methods to produce pristine graphene flakes in large quantities are based on the liquid-phase exfoliation processes. These one-step physical transformations of graphite into graphene offer many unique advantages. To date, a large number of liquids have been employed as exfoliation media exploiting their thermodynamic and chemical features as compared to those of graphene. Here, we pursued the goal of realizing water based mixtures to exfoliate graphite and disperse graphene without the aid of surfactants. To this aim, aqueous mixtures with suitable values of surface tension and Hansen solubility parameters (HSPs), were specifically designed and used. The very high water surface tension was decreased by the addition of solvents with lower surface tensions such as alcohols, obtaining, in this way, more favourable HSP distances. The specific role of each of these thermodynamic features was finally investigated. The results showed that the designed hydroalcoholic solutions were effective in both the graphite exfoliation and dispersion without the addition of any surfactants or other stabilizing agents. Stable graphene suspensions were obtained at concentration comparable to those produced with low-boiling solvents and water/surfactants.

A Simple Optical Model for the Swelling Evaluation in Polymer Nanocomposites

In the present study, we report on a simple optical method based on thin film interferometry for the swelling evaluation in polymer nanocomposite layers used for gas sensing applications. We show that white light interferometry can be profitably applied to characterize scattering materials such as polymer/carbon black nanocomposites. A properly adjusted experimental setup was implemented to monitor the swelling behavior of the sensitive films in real device operating conditions. In particular, the behavior of poly(2-hydroxyethyl methacrylate) (PHEMA) and of carbon black/PHEMA nanocomposite layers, used for volatile organic compounds (VOCs) detection, was investigated and measured under ethanol vapors exposure (max 1%). The method is very sensitive and the swelling in the range of only few nanometers can be measured. Interestingly, we have found that the nanocomposite undergoes a more pronounced swelling process with respect to pristine polymer. Ethanol diffusion coefficients in the nanocomposite were evaluated.

Reproducibility of the Performances of Graphene-Based Gas-Sensitive Chemiresistors

The potential of graphene as sensing layer relies on its two-dimensional nature that provides the greatest sensor area per unit volume. Thanks to this property, besides the highest mobility and the lowest resistivity values, graphene has put itself as the leader of the new discovered materials in every research field. Graphene can be produced by various approaches including micromechanical exfoliation of graphite, thermal dissociation of SiC, chemical vapor deposition, or by low-cost approaches such as chemical exfoliation methods. However, the sensor device development is still affected by several technological limitations mainly related to graphene preparation, introduction into device architectures, and reproducibility of the sensor performances. Regarding the last item, sensing performance may differ from device to device even though graphene materials come from the same batch and the same fabrication protocol. In this work, chemiresistive devices based on chemically exfoliated natural graphite are presented. Several parameters were taken into account: graphene preparation (including solvents, centrifugation speed, and batch), deposition, and conductance. Finally the device-to-device variation is addressed.

Exfoliation of Graphite and Dispersion of Graphene in Solutions of Low-Boiling-Point Solvents for Use in Gas Sensors

In this work we report on the development of an eco-friendly method for the chemical exfoliation of graphite in order to produce high-quality graphene for sensing applications. A mixture of low-boiling-point solvents, such as 1-butanol and 2-propanol, was employed for this purpose. The resulting colloidal suspension was a stable dispersion of few-layer flakes. This material was employed to fabricate chemiresistor devices that showed a remarkable variation of conductance when exposed to 350 ppb of NO2.

Inkjet printed graphene-based chemi-resistors for gas detection in environmental conditions

In this work, we report on the inkjet printing as potential technology to manufacture chemi-resistors based on liquid phase exfoliated graphene. With respect to the conventional solution-processable methods, the main IJP capability is related to the deposition of small ink volumes that entails a more controlled drying process. This specific potentiality of the IJP technique were exploited in order to investigate the reproducibility of the device performances upon NO2 and NH3 exposure and operating in environmental conditions.

Different sizes of ZnO diversely affected the cytogenesis of the sea urchin Paracentrotus lividus

Today nanoparticles (NPs) have many applications in commercial products due to their small size and peculiar properties that, conversely, make them potentially toxic for humans and the environment. ZnO NPs are largely used in many personal care products, such as sunscreens and cosmetics. In this study the cytotoxic effects of ZnO particles with different sizes (ZnO Bulk, >100nm; ZnO NPs, 100nm and ZnO NPs, 14nm) upon the first developmental stages of the sea urchin Paracentrotus lividus, are evaluated. Morphological alterations are also assessed by embryotoxicity tests. The cytogenetic analysis highlighted that ZnO NPs interfere with cell cycle inducing a dose-dependent decrease of mitotic activity and chromosomal aberrations at higher concentrations (30μM). Moreover, the larval development was affected by ZnO NPs 100nm (EC50=0.46 [0.30-0.63] μM [Zn]) in a dose-dependent way. Size-dependent toxicity was instead not obtained for ZnO NPs. From our results could be highlighted that the presence of embryos, blocked in pre-larval stage, could be due to the induction of chromosome aberrations by ZnO particles, confirming that cytogenetic analyses allow evaluating possible NPs action mechanisms.