Production of nanocellulose gels and films from invasive tree species.

Wood from invasive tree species Acacia dealbata and Ailanthus altissima was used to produce high value-added nanocellulose. Firstly, bleached pulps were produced from the wood of these tree species after kraft cooking. Afterwards, the resultant pulps were pre-treated by TEMPO-mediated oxidation (Acacia dealbata) or enzymatic hydrolysis (Ailanthus altissima) followed by high-pressure homogenization. Hydrogels were obtained and characterized for their main physical and chemical properties, including rheology measurements. After freeze-drying, the surface properties of the materials were evaluated by inverse gas chromatography. Results showed that nano/micro fibrils could be obtained from the wood of these invasive species. Rheometry studies showed that Acacia-TEMPO cellulose nanofibrils form strong gels with high yield stress point and viscosities (reaching ca. 100,000 Pa·s). Additionally, the surfaces of the obtained nanocelluloses showed a dispersive component of the surface energy near 40 mJ/m2 and a prevalence of the Lewis acidic character over the basic one, as typical for cellulose-based materials. Finally, films with good mechanical and optical properties could be obtained from the cellulose hydrogels. Acacia-TEMPO film (produced by filtration/hot pressing) showed a tensile strength of 79 MPa, Young's modulus of 7.9 GPa, and a transparency of 88%. The water vapor barrier, however, was modest (permeability of 4.9 × 10-6 g/(Pa·day·m)).

Tuning rheology and aggregation behaviour of TEMPO-oxidised cellulose nanofibrils aqueous suspensions by addition of different acids.

The present work intends to study the variations in the rheological properties and aggregation behaviour of TEMPO-oxidised cellulose nanofibrils (CNF) aqueous suspensions, as a function of changes in concentration and systematic changes in the pH, by addition of acids with different anions. It was found that CNF suspensions form strong gels at mass fractions higher than 0.35 % and the gel point is ca. 0.18 %. On the other hand, aggregation is enhanced at acidic pH conditions due to lower charge repulsion among fibrils, leading to an increase of the suspension viscosity. However, distinct rheological behaviours were presented by CNF suspensions as different acids were applied. It was found that phosphate ions resulted in significant aggregation leading to formation of particles of large size and very strong gels, at pH 2.3; distinctly, the presence of acetate ions resulted in lower aggregation, lower particle size and weaker gels, at the same pH value.

Impact of organic nano-vesicles in soil: The case of sodium dodecyl sulphate/didodecyl dimethylammonium bromide.

Aiming at contributing new insights into the effects of nanomaterials (NMs) in the terrestrial ecosystem, this study evaluated the impacts of organic nano-vesicles of sodium dodecyl sulphate/didodecyl dimethylammonium bromide (SDS/DDAB) on the emergence and growth of plant seeds, and on the avoidance and reproduction of soil invertebrates. For this purpose several ecotoxicological assays were performed with different test species (terrestrial plants: Zea mays, Avena sativa, Brassica oleracea and Lycopersicon esculentum; soil invertebrates: Eisenia andrei and Folsomia candida). A wide range of SDS/DDAB concentrations were tested, following standard protocols, and using the standard OECD soil as a test substrate (5% of organic matter). The aqueous suspensions of SDS/DDAB, used to spike the soils, were characterised by light scattering techniques for hydrodynamic size of the vesicles, aggregation index, polydispersity index, zeta potential and surface charge. The SDS/DDAB concentrations in the test soil were analysed by HPLC-UV at the end of the assays. Invertebrate species were revealed to be sensitive to nano-SDS/DDAB upon immediate exposure to freshly spiked soils. However, the degradation of SDS/DDAB nano-vesicles in the soil with time prevented the occurrence of significant reproduction effects on soil invertebrates. Plants were not particularly sensitive to SDS/DDAB, except B. oleracea (at concentrations above 375 mg kg(-1)dw). The results gathered in this study allowed a preliminary determination of a risk limit to nano-SDS/DDAB. The low toxicity of SDS/DDAB nano-vesicles could be explained by its high and fast degradation in the soil. The soil microbial community could have an important role in the fate of this NM, thus it is of remarkable importance to improve this risk limit by taking into account specific data addressing this community.

Assessing the ecotoxicity of metal nano-oxides with potential for wastewater treatment.

The rapid development of nanotechnology and the increasing use of nanomaterials (NMs) raise concern about their fate and potential effects in the environment, especially for those that could be used for remediation purposes and that will be intentionally released to the environment. Despite the remarkable emerging literature addressing the biological effects of NMs to aquatic organisms, the existing information is still scarce and contradictory. Therefore, aimed at selecting NMs for the treatment of organic and inorganic effluents, we assessed the potential toxicity of NiO (100 and 10-20 nm), Fe2O3 (≈85 × 425 nm), and TiO2 (<25 nm), to a battery of aquatic organisms: Vibrio fischeri, Raphidocelis subcapitata, Lemna minor, Daphnia magna, Brachionus plicatilis, and Artemia salina. Also a mutagenic test was performed with two Salmonella typhimurium strains. Suspensions of each NM, prepared with the different test media, were characterized by dynamic light scattering (DLS) and eletrophoretic light scattering (ELS). For the assays with marine species, no toxicity was observed for all the compounds. In opposite, statistically significant effects were produced on all freshwater species, being D. magna the most sensitive organism. Based on the results of this study, the tested NMs can be classified in a decreasing order of toxicity NiO (100 nm) > NiO (10-20 nm) > TiO2 (<25 nm) > Fe2O3, allowing to infer that apparently Fe2O3 NMs seems to be the one with less risks for receiving aquatic systems.

The effects of acrylamide polyelectrolytes on aquatic organisms: relating toxicity to chain architecture.

Understanding the inherent toxicity of water-soluble synthetic polyelectrolytes is critical for adequate risk management as well as enhancing product design when biological activity is a key performance index (e.g. for application in biofouling bivalves' control). The toxicity of two cationic acrylamide copolymers with different chain branching degree was evaluated. Standard ecotoxicity tests were conducted with microalgae and daphnids. The susceptibility of Corbicula fluminea, as a biofouling bivalve, was also evaluated. The effect of polyelectrolyte on the test media viscosity and the polymer chain size distributions under the experimental conditions were also examined. The susceptibility of the microalgae to both polymers was similar. As the complexity and size of the test organisms increased, differences in toxicity due to different chain architecture were noticeable. The more branched polymer was significantly less toxic to both daphnids and the bivalves, which could be linked to the distinctive features of its bimodal size chain distribution. This architecture resulted in both more compact globular molecules and the formation of aggregates, which reduce the polymer interaction with the biological surfaces. The results of this study promote the incorporation of environmental considerations in polyelectrolyte development and contribute to the design of improved solutions for controlling biofouling bivalves.

Toxicity of organic and inorganic nanoparticles to four species of white-rot fungi.

The rapid development of nanoparticles (NP) for industrial applications and large-volume manufacturing, with its subsequent release into the environment, raised the need to understand and characterize the potential effects of NP to biota. Accordingly, this work aimed to assess sublethal effects of five NP to the white-rot fungi species Trametes versicolor, Lentinus sajor caju, Pleurotus ostreatus, and Phanerochaete chrysosporium. Each species was exposed to serial dilutions of the following NP: organic-vesicles of SDS/DDAB and of Mo/NaO; gold-NP, quantum dot CdSe/ZnS, and Fe/Co. Fungi growth rate was monitored every day, and at the end of assay the mycelium from each replicate was collected to evaluate possible changes in its chemical composition. For all NP-suspensions the following parameters were characterized: hydrodynamic diameter, surface charge, aggregation index, zeta potential, and conductivity. All tested NP tended to aggregate when suspended in aqueous media. The obtained results showed that gold-NP, CdSe/ZnS, Mo/NaO, and SDS/DDAB significantly inhibited the growth of fungi with effects on the mycelium chemical composition. Among the tested NP, gold-NP and CdSe/ZnS were the ones exerting a higher effect on the four fungi. Finally to our knowledge, this is the first study reporting that different types of NP induce changes in the chemical composition of fungi mycelium.

Biochemical and metabolic effects of a short-term exposure to nanoparticles of titanium silicate in tadpoles of Pelophylax perezi (Seoane).

This study aimed to evaluate sublethal effects of a short-term exposure (96 h) to titanium silicate nanoparticles (TiSiO(4)-NP) on Pelophylax perezi tadpoles. Tadpoles were exposed to five concentrations of TiSiO(4)-NP (8.2, 10.2, 12.8, 16 and 20 mg/L) plus a control. Effect criteria were: mortality, cholinesterases, glutathione S-transferases, lactate dehydrogenase, and catalase activities, and alanine and lactate contents. Light scattering was used for physical characterization of TiSiO(4)-NP suspensions, revealing a high aggregation state of the NP, consistent with low z-potential values (<30 mV). Mortality among TiSiO(4)-NP treatments was <11%. Significant differences relatively to the control were observed at the biochemical level (for CAT and LDH) and in lactate and alanine contents, which may end-up in increased oxidative stress. Overall, some of the monitored endpoints suggest metabolic alterations in TiSiO(4)-NP exposed tadpoles, highlighting the potential of TiSiO(4)-NP long-term effects on these organisms.

Toxicity and genotoxicity of organic and inorganic nanoparticles to the bacteria Vibrio fischeri and Salmonella typhimurium.

The present work aimed at evaluating the toxicity and genotoxicity of two organic (vesicles composed of sodium dodecyl sulphate/didodecyl dimethylammonium bromide-SDS/DDAB and of monoolein and sodium oelate-Mo/NaO) and four inorganic (titanium oxide-TiO2, silicon titanium-TiSiO4, Lumidot-CdSe/ZnS, and gold nanorods) nanoparticles (NP), suspended in two aqueous media (Milli Q water and American Society for Testing and Materials (ASTM) hardwater), to the bacteria Vibrio fischeri (Microtox test) and Salmonella typhimurium-his⁻ (Ames test with strains TA98 and TA100). Aiming a better understanding of these biological responses physical and chemical characterization of the studied NP suspensions was carried out. Results denoted a high aggregation state of the NP in the aqueous suspensions, with the exception of SDS/DDAB and Mo/NaO vesicles, and of nanogold suspended in Milli Q water. This higher aggregation was consistent with the low values of zeta potential, revealing the instability of the suspensions. Regarding toxicity data, except for nano TiO2, the tested NP significantly inhibited bioluminescence of V. fischeri. Genotoxic effects were only induced by SDS/DDAB and TiO2 for the strain TA98. A wide range of toxicity responses was observed for the six tested NP, differing by more than 5 orders of magnitude, and suggesting different modes of action of the tested NP.

Screening evaluation of the ecotoxicity and genotoxicity of soils contaminated with organic and inorganic nanoparticles: the role of ageing.

This study aimed to evaluate the toxicity and genotoxicity of soils, and corresponding elutriates, contaminated with aqueous suspensions of two organic (vesicles of sodium dodecyl sulphate/didodecyl dimethylammonium bromide and of monoolein and sodium oleate) and five inorganic nanoparticles (NPs) (TiO(2), TiSiO(4), CdSe/ZnS quantum dots, Fe/Co magnetic fluid and gold nanorods) to Vibrio fischeri and Salmonella typhimurium (TA98 and TA100 strains). Soil samples were tested 2h and 30 days after contamination. Suspensions of NPs were characterized by Dynamic Light Scattering. Soils were highly toxic to V. fischeri, especially after 2h. After 30 days toxicity was maintained only for soils spiked with suspensions of more stable NPs (zeta potential>30 mV or <-30 mV). Elutriates were particularly toxic after 2h, except for soil spiked with Fe/Co magnetic fluid, suggesting that ageing may have contributed for degrading the organic shell of these NPs, increasing the mobility of core elements and the toxicity of elutriates. TA98 was the most sensitive strain to the mutagenic potential of soil elutriates. Only elutriates from soils spiked with gold nanorods, quantum dots (QDs) and TiSiO(4) induced mutations in both strains of S. typhimurium, suggesting more diversified mechanisms of genotoxicity.

Polyurethane-based microparticles: formulation and influence of processes variables on its characteristics.

This study reports the development of polyurethane-based microparticles and the influence of some processes variables on its characteristics. These microparticles were prepared by emulsion polymerization, using poly(caprolactone) diol (PCL) and poly(propylene glycol), tolylene 2,4-diisocyanate terminated (TDI) or poly(propylene oxide)-based tri-isocyanated pre-polymer (TI). The reaction of polymerization was confirmed by attenuated total internal reflection Fourier transformed infrared spectroscopy (ATR-FTIR). Their thermal characteristics were investigated by dynamical mechanical thermal analysis (DMTA) and thermogravimetric analysis (TGA). For good microparticles formation, formulation 80/20 (mass ratio isocyanate/PCL) was the most indicated. Their spherical shape and smooth surface were observed by optical and scanning electron microscopy (SEM). Zeta potential measurements suggest that ionized carbonyl groups existent at the surface can be responsible for the negative potentials obtained. Respecting size and size distribution of the particles, measured by laser diffraction spectroscopy (LDS), the stirring speed and type were the process variables that most influenced it.