1,721,061 research outputs found
NanoTiO2@DNA complex: a novel eco, durable, fire retardant design strategy for cotton textiles
No full textA strategy for the design of cotton flame retardant coatings is described, exploiting the natural intumescent formulation of nucleic acids, the intrinsic thermal inertia of TiO 2 ceramic phase and the strong affinity that TiO 2 nanoparticles shows for amphiphilic biomolecules (e.g. proteins, nucleic acids) and hydrophilic substrates. Two different self-assembled TiO 2 @DNA systems are obtained by mixing two opposite charged TiO 2 nanoparticles suspensions with DNA solution. The colloidal behavior of separate and mixed phases was investigated, as well as the morphological, chemical structure and thermal properties of resulting coatings, in order to make some hypothesis on the observed synergic effects. Scanning electron microscopy (SEM) and Attenuated Total Reflectance (ATR) spectroscopy demonstrated the homogeneous distribution of nano-TiO 2 @DNA based coatings on the treated fabrics. The washing fastness tests evidenced the highly improved performance of hybrid coatings if compared with DNA alone. The flammability and cone calorimetry test results confirmed this positive synergy that resulted quite effective in slowing down (or even blocking) the propagation of a flame within the treated substrates and in improving the resistance of the fabrics to the applied heat flux, these latter leaving increased residues at the end of the test
Hollow-fiber flow field-flow fractionation and multi-angle light scattering as a new analytical solution for quality control in pharmaceutical nanotechnology
No full textThe rapid development of nanoproducts in pharmaceutical field highlights the need for robust analytical methods to ensure their quality and stability. Nanoparticles of different nature and composition (NPs) are employed for many purposes, such as the improvement of drug solubility/bioavailability and the controlled delivery of drugs. Among NPs features, particle size distribution (PSD) plays a fundamental role in determining NPs properties. Nevertheless the high development of different NPs, authorities such as the FDA and the European Union highlight the lack of robust characterization methods and quality control for nanomaterials.
Among the techniques for the size-characterization of particles, Field-Flow Fractionation (FFF) represents a competitive choice: due to the absence of a stationary phase, the separation mechanism is gentle with total maintenance of the native properties of the analytes. In this paper the microcolumn variant of FFF, the Hollow-Fiber Flow FFF (HF5), is coupled on-line with Multi-Angle Light Scattering (MALS) for the development of methods for the characterization of NPs as quality control in new pharmaceutical field. The HF5-MALS was applied to the size characterization in different preservation conditions of silver polyvinylpyrrolidone-stabilized NPs (AgPVP) used for their antimicrobial activity. The ratio of gyration and hydrodynamic radii of AgPVP was evaluated for fresh and aged NPs, suggesting in this case aggregation rearrangement. The influence of different PVP coating and dilution factor was also studied. Finally the metal ion release was determined in relationship to these shape modifications. The HF5-MALS method is robust and reproducible and it can be considered as an important tool for the development of analytical platform for quality control of NPs
Characterization of polyethylene and polyurethane microplastics and their adsorption behavior on Cu2+ and Fe3+ in environmental matrices
Get PDFAs the world faces growing environmental challenges, understanding the nature of microplastics—such as Low-Density Polyethylene (LDPE) and Polyurethane (PU)—and their transformation in water-based environments is necessary for predicting and mitigating their effects. In this study, we investigated their physicochemical characteristics, presence of impurities, colloidal behavior, and sorption capacity to understand better how microplastics behave and transform in the environment, including their role in transporting heavy metals. The two types of microparticles investigated fall into distinct size ranges, approximately 70 microns for PE particles and around 5 microns for PU particles. Both samples showed a spherical morphology and an evident surface micro-roughness. The elemental and thermal analysis did not show the presence of any significant metal impurities. The zeta-potential measurements as a function of pH provided insights into the dispersion behavior of microplastics (MPs) in freshwaters, suitable for the growth of Zebrafish (Egg water) and Daphnia magna (Elendt M7 Water). Both materials showed in bidistilled water negative zeta potential (ZP) at natural pH (ZP = − 51.0 ± 4.3 mV at pH = 6.6 and ZP = − 29.5 ± 1.4 mV at pH = 5.6 for LDPE and PU, respectively), justified by the presence of surface-active charged impurities. In saline media, ZP vs. pH curves were flatter, with ZP values near 0 mV, confirming the reduced colloidal stability from higher ionic strength and double-layer compression. Finally, we assessed the metal adsorption capacity to establish the role of microplastics in the transport of heavy metals in the environment. We observed selective adsorption for Cu2+ ions, which was both medium-dependent (more ions adsorbed in Elendt M7) and plastic-dependent, with PU showing a stronger affinity for Cu2+ in MilliQ and Egg water. On the contrary, both plastics showed similar adsorption capacity for Fe3+ ions across all media
Shape-Related Toxicity of Titanium Dioxide Nanofibres
Get PDFTitanium dioxide (TiO2) nanofibres are a novel fibrous nanomaterial with increasing applications
in a variety of fields. While the biological effects of TiO2 nanoparticles have been
extensively studied, the toxicological characterization of TiO2 nanofibres is far from being
complete. In this study, we evaluated the toxicity of commercially available anatase TiO2
nanofibres using TiO2 nanoparticles (NP) and crocidolite asbestos as non-fibrous or fibrous
benchmark materials. The evaluated endpoints were cell viability, haemolysis, macrophage
activation, trans-epithelial electrical resistance (an indicator of the epithelial barrier competence),
ROS production and oxidative stress as well as the morphology of exposed cells.
The results showed that TiO2 nanofibres caused a cell-specific, dose-dependent decrease
of cell viability, with larger effects on alveolar epithelial cells than on macrophages. The
observed effects were comparable to those of crocidolite, while TiO2 NP did not decrease
cell viability. TiO2 nanofibres were also found endowed with a marked haemolytic activity, at
levels significantly higher than those observed with TiO2 nanoparticles or crocidolite. Moreover,
TiO2 nanofibres and crocidolite, but not TiO2 nanoparticles, caused a significant
decrease of the trans-epithelial electrical resistance of airway cell monolayers. SEM images
demonstrated that the interaction with nanofibres and crocidolite caused cell shape perturbation
with the longest fibres incompletely or not phagocytosed. The expression of several
pro-inflammatory markers, such as NO production and the induction of Nos2 and Ptgs2,
was significantly increased by TiO2 nanofibres, as well as by TiO2 nanoparticles and crocidolite.
This study indicates that TiO2 nanofibres had significant toxic effects and, for most
endpoints with the exception of pro-inflammatory changes, are more bio-active than TiO2
nanoparticles, showing the relevance of shape in determining the toxicity of nanomaterials.
Given that several toxic effects of TiO2 nanofibres appear comparable to those observed
with crocidolite, the possibility that they exert length dependent toxicity in vivo seems worthy
of further investigation
TiO2 Nanoparticles synergistically increase LPS-induced NO Production by Macrophages
No full textAlthough TiO2 NPs particles are endowed with little acute toxicity in vitro, they exert pro-inflammatory effects when inhaled in vivo. In this study, we evaluated the effects of several TiO2NPs, alone or in combination with LPS, on Raw264.7 macrophages in terms of cell viability (determined up to 72h with resazurin assay), NO production (estimated by nitrite concentration in the culture medium after 48h and 72h of treatment), and Nos2 induction, assessed with RT-PCR after 24h of treatment. We tested three types of TiO2 NP: a) pristine TiO2 NP of industrial origin (84% anatase/16% brookite, average NP size 45 nm), b) citrate-coated TiO2 NP, derived from pristine TiO2 NPs (average NP size 64 nm), c) Aeroxide P25 TiO2 NPs (80% anatase/20% rutile, average NP size 25 nm).
All the TiO2 NPs did not affect significantly cell viability even at the highest doses tested (IC50>80 μg/cm2 at 24,48 and 72h). On the contrary, all the NP preparations, at the dose of 20 μg/cm2, induced Nos2. In particular, Nos2 was 3-fold, 8-fold and 4-fold induced by pristine, citrate coated and Aeroxide P25 TiO2 NPs alone, while fold-induction rose to 13 for pristine and citrate-coated NPs and to 30 for Aeroxide P25 NPs in the presence of 1 ng/ml LPS. LPS alone caused a 6-fold increase in Nos2 expression. The effects of pristine, citrate-coated and Aeroxide P25 TiO2 NPs on NO production were clearly dose- and time-dependent. At 80 g/cm2 of NP, nitrites were 5-fold, 9-fold and 7-fold higher than in the untreated control at 48h and 7-fold,10-fold and 8-fold higher than control at 72h. For all the TiO2NPs tested, the No-Observed-Effect-Level (NOEL) was 20 g/cm2 at 48h and 10 g/cm2 at 72h. After 48h-incubation with LPS (1 ng/ml) and TiO2 (80 μg/cm2), nitrite medium concentration was 31-fold, 30-fold and 25-fold higher than control with, respectively, pristine, citrate-coated and Aeroxide P25. LPS alone caused a 22-fold increase in medium nitrites.
Several TiO2 NPs significantly induce Nos2 gene expression and increase NO production in a dose- and time-dependent manner in Raw264.7 cells. The enhancement of Nos2 induction by LPS suggests that the pro-inflammatory effect of TiO2 NPs in vivo may be exacerbated by concomitant infectious conditions and surface interactions with bacterial endotoxins.
Supported by EU Grant NMP4-SL-2012-280716 (Sanowork Project
Bimetallic Nanoparticles as Efficient Catalysts: Facile and Green Microwave Synthesis
No full textThis work deals with the development of a green and versatile synthesis of stable monoand
bi-metallic colloids by means of microwave heating and exploiting ecofriendly reagents: water
as the solvent, glucose as a mild and non-toxic reducer and polyvinylpirrolidone (PVP) as the
chelating agent. Particle size-control, total reaction yield and long-term stability of colloids were
achieved with this method of preparation. All of the materials were tested as effective catalysts in the
reduction of p-nitrophenol in the presence of NaBH4 as the probe reaction. A synergistic positive
effect of the bimetallic phase was assessed for Au/Cu and Pd/Au alloy nanoparticles, the latter
showing the highest catalytic performance. Moreover, monoand bi-metallic colloids were used to
prepare TiO2- and CeO2-supported catalysts for the liquid phase oxidation of 5-hydroxymethylfufural
(HMF) to 2,5-furandicarboxylic acid (FDCA). The use of Au/Cu and Au/Pd bimetallic catalysts
led to an increase in FDCA selectivity. Finally, preformed Pd/Cu nanoparticles were incorporated
into the structure of MCM-41-silica. The resulting Pd/Cu MCM-41 catalysts were tested in the
hydrodechlorination of CF3OCFClCF2Cl to CF3OCF=CF2. The effect of Cu on the hydrogenating
properties of Pd was demonstrated
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Eco-design di materiali avanzati per la protezione della salute dell'uomo e dell'ambiente
No full textThe widespread manufacturing of nanomaterials and nano-enabled products (NEPs) has led to concerning human and environmental exposure levels. The lack of knowledge regarding the occupational, consumer, and environmental potential adverse effects of this burgeoning technology has ignited serious safety issues and highlighted the importance of a comprehensive risk evaluation. Safety and Sustainability by Design (SSbD) is a concept that thanks to a prevention approach aims to reduce the hazards at the early stages of product development. The combined implementation of safety measures and risk assessment will have to meet regulatory infrastructures to deliver SSbD guidelines and tools. To reach this goal it will be crucial to monitor the effects of these products and their manufacturing processes on human and environmental health. Structure-properties correlations must be studied to determine general guidelines and deliver safer and more sustainable design alternatives to the actual nanomaterials. A proper design of the synthesis step directly affects the structure of the nanomaterials allowing to building of the desired physicochemical, functional, and safety profiles. In this context, the design or re-design of a nanomaterial is an early-stage measure that can effectively improve the safety and sustainability of the product creating a bridge between design space and functional properties. A full life cycle assessment is required to link the nanomaterials design step to the nano-enabled products manufacturing, use phase, and end of life.
To contribute to this research field, during this work, three main topics were assessed: the synthesis of antimicrobial silver nanoparticles and their implementation into several case studies, the synthesis of gold-platinum nanoparticles for application as a catalyst in biomass valorization, and the production of biopolymeric scaffolds embedding natural-derived active phases for the wastewater remediation.
Three AgNPs synthesis methods using different capping agents were studied:
- Quaternized hydroxyethyl cellulose is a natural-derived biopolymer with positive charged quaternary ammonium groups that confers antibacterial activity to this compound.
- Curcumin is a natural-derived organic molecule with intrinsic antimicrobial and antioxidant properties.
- Cyclic lipopeptide biosurfactant derived from bacterial metabolism which possesses antimicrobial properties thanks to its cell wall lysis capability.
A wide-ranging physicochemical characterization (TEM, XRD, ICP-OES, UV-Vis, DLS, ELS) was performed to correlate synthesis parameters to physicochemical and functional properties.
The so-obtained AgNPs were tested against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus and Listeria innocua) bacteria, demonstrating excellent antibacterial activity against all the tested bacterial strains. Antiviral tests were performed against the SARS-CoV-2 enveloped virus and BK polyomavirus non-enveloped virus, proposing an antiviral mechanism of action of AgNPs involving the interaction of AgNPs with the viral envelope inhibiting the attachment to cell’s receptors.
The most active AgNPs variants were selected for the implementation into nano-enabled products within different case studies: antimicrobial textiles, paper, and biopolymeric film and scaffolds. The antimicrobial properties were successfully transferred from the nanomaterial to the nano-enabled product. Thanks to these case studies workers, users, and environmental exposures were assessed. NEPs antibacterial efficacy and product durability were evaluated.
The Safe and Sustainable by Design approach was applied for the synthesis of gold-platinum nanoparticles catalysts. The green chemistry principles were implemented on multiple levels, first for the safe and sustainable synthesis of the nanoparticles and then in their application for biomass valorization by converting biomass wastes into chemical building blocks. Two different gold-platinum nanoparticles structures were studied core-shell (gold core and a platinum external shell) and alloy. The correlation between the structure and the catalytic activity of these materials was studied thanks to an in-depth physicochemical characterization (TEM, XRD, ICP-OES, UV-Vis, DLS, ELS). The catalytic activity was evaluated in the model reaction of hydrogenation of nitrophenol to aminophenol. Synergistic effects were observed for the bi-metallic nanoparticles, thanks to which a reduced load of platinum allows excellent catalytic activity.
The increasing contamination of hydric resources caused by human activities has highlighted the necessity to develop new technologies for wastewater remediation. From a circular economy perspective, natural adsorbent materials were selected for this purpose. Clays and hydrotalcites share a layered structure able to host counterions, the deriving ion exchange capability has been efficiently exploited for the adsorption of heavy metals and organic pollutants. The selected adsorbents were characterized by XRD, BET, and ELS, subsequently, they were tested in the adsorption of simulated pollutants, namely the cationic dye rhodamine B, anionic dye methyl orange, and copper (II) cation. Clays and hydrotalcites were embedded into renewable seaweed-derived biopolymeric scaffolds made of k-carrageenan, chitosan, or agarose to improve their handleability. The pollutants adsorption tests were replicated on the scaffolds and the resulting adsorption process kinetic followed the pseudo-second-order model
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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