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[en] Carbon nanotubes (CNTs) have been successfully coated with a covalently bonded polymer brush of negatively charged poly(3-sulfopropylamino methacrylate) (PSPM) by in situ polymerization employing atomic transfer radical polymerization (ATRP) from initiating silanes attached to the CNTs before the polymerization. The CNT-bonded brush forms a polymer layer or shell-like structure around the CNTs and provides colloidal stabilization for the CNTs in aqueous media. In situ syntheses of nanocrystalline CdS and magnetic iron oxide in the polymer brushes lead to the formation of hybrid nanocomposites consisting of nanoparticle-containing PSPM-coated CNTs that remain readily dispersible and stable in aqueous media. The hybrid nanostructures are synthesized by ion exchange with the cations of the sulfonate groups of the PSPM followed by precipitation and were followed by stepwise zeta potential measurements and TEM. Such structures could have applications in the design of more complex structures and devices. The general synthetic scheme can be extended to include other nanoparticles as brush cargo to broaden the utility or functionality of the CNTs. TEM data shows nanocrystalline CdS in the range of 5-8 nm embedded in the PSPM brush and nanocrystalline iron oxide with a size between 2 and 4 nm, with the former consistent with UV-vis spectroscopy and fluorescence measurements.
[en] Dustiness testing using a down-scaled EN15051 rotating drum was used to investigate the effects of storage conditions such as relative humidity and physical loading on the dustiness of five inorganic metal oxide nanostructured powder materials. The tests consisted of measurements of gravimetrical respirable dustiness index and particle size distributions. Water uptake of the powders during 7 days of incubation was investigated as an explanatory factor of the changes. Consequences of these varying storage conditions in exposure modelling were tested using the control banding and risk management tool NanoSafer. Drastic material-specific effects on powder respirable dustiness index were observed with the change in TiO_2 from 30 % RH (639 mg/kg) to 50 % RH (1.5 mg/kg). All five tested materials indicate a decreasing dustiness index with relative humidity increasing from 30 to 70 % RH. Test of powder water uptake showed an apparent link with the decreasing dustiness index. Effects of powder compaction appeared more material specific with both increasing and decreasing dustiness indices observed as an effect of compaction. Tests of control banding exposure models using the measured dustiness indices in three different exposure scenarios showed that in two of the tested materials, one 20 % change in RH changed the exposure banding from the lowest level to the highest. The study shows the importance of powder storage conditions prior to tests for classification of material dustiness indices. It also highlights the importance of correct storage information and relative humidity and expansion of the dustiness test conditions specifically, when using dustiness indices as a primary parameter for source strength in exposure assessment
[en] The present study reports on the fabrication, morphological and structural characterizations, magnetic and biological tests of a biocompatible superparamagnetic carrier comprising iron oxide nanoparticle (ION) surface-functionalized with chondroitin sulfate (ChS), labelled ION@ChS. The reported ION@ChS sample is produced by alkaline coprecipitation of Fe2+ and Fe3+ ions in aqueous media in the presence of ChS. Fourier Transform infrared, Raman and x-ray photoelectron spectroscopies provide evidences for coordination of the ChS molecule (mainly through sulfonic groups) onto the ION’s surface. Transmission electron microscopy reveals that the ION@ChS are nearly spherical (mean diameter = 8.2 nm ± 0.1) and almost monodispersed (diameter dispersity = 0.11 ± 0.01), while dynamic light scattering and electrophoretic mobility measurements confirm the presence of ChS at the ION’s surface, providing mean hydrodynamic diameter (∼100 nm) and very high negative zeta potential (around −50 mV). Moreover, the ION@ChS is superparamagnetic at room temperature, with no coercivity or remanence. Cell viability tests performed by means of the MTT assay indicates that ION@ChS shows no cytotoxiciy effect (p < 0.05). Therefore, one can anticipate potential biotechnological applications of the ION@ChS sample for site-specific delivery of ChS as well as a contrast agent in magnetic resonance imaging. (paper)
[en] Highlights: • Humic acid-HA, NaHCO3, MgSO4, KCl and CaCl2 change the stability and oxidation state of silver nanoparticle-AgNPs surface. • Ag3+ is formed on AgNPs surface mainly in presence of NaHCO3, MgSO4 and HA. • Toxicological endpoints in zebrafish embryos exposed to Ag3+ were not significant for acute exposure. • HA coated on AgNPs surface reduces the concentration of Ag ions released and the toxicity in zebrafish embryos. • HA acts as a natural attenuator/remediator of polluted water with AgNPs. - Abstract: The use of silver nanoparticles (AgNPs) result in an inevitable contact with aquatic environments. Here we study the behavior of AgNPs and the developmental toxicity in zebrafish embryos exposed to these nanoparticles (0–10 mg/L) with and without the presence of HA (20 mg/L), using zebrafish facility water (ZFW) and zebrafish growing media (ZGM). The presence of cations and HA gave rise to a decrease in Ag ion release and ζ-potential, an increase in the hydrodynamic diameter and oxidation of the AgNP surface. The results show that the presence of HA and cations in the media, as well as the silver speciation, i.e., the unusual presence of Ag3+, decreases the toxicity of AgNPs (LC50AgNPs: 1.19 mg/L; LC50AgNPs+HA: 3.56 mg/L), as well as silver bioavailability and toxicity in zebrafish embryos. Developmental alterations and the LC50 (1.19 mg/L) of AgNPs in ZFW were more relevant (p ≤ 0.05) than for AgNPs in ZGM (LC50 > 10 mg/L). It was demonstrated that the bioaccumulation and toxicity of AgNPs depends on several factors including AgNPs concentration, nanoparticle aggregation, dissolved silver ions, speciation of silver ions, the amount of salt in the environment, the presence of humic substances and others, and different combinations of all of these factors.
[en] Highlights: • Remotely-actuated chitosan/alginate magnetic nanoplatforms were synthesized. • Layer-by-layer deposition was optimized by conductimetric-potentiometric titrations. • Reversal of the surface charge is achieved by biopolymer polyions capping layers. • Nanoplatforms presented enhanced loading capacity for curcumin. • Biopolymer deposition improved the cell viability of magnetic nanoplatforms. - Abstract: Remotely assisted drug delivery by means of magnetic biopolymeric nanoplatforms has been utilized as an important tool to improve the delivery/release of hydrophobic drugs and to address their low cargo capacity. In this work, MnFe2O4 magnetic nanoparticles (MNPs) were synthesized by thermal decomposition, coated with citrate and then functionalized with the layer-by-layer (LbL) assembly of polyelectrolyte multilayers, with chitosan as polycation and sodium alginate as polyanion. Simultaneous conductimetric and potentiometric titrations were employed to optimize the LbL deposition and to enhance the loading capacity of nanoplatforms for curcumin, a hydrophobic drug used in cancer treatment. ~200 nm sized biopolymer platforms with ~12 nm homogeneously embedded MNPs were obtained and characterized by means of XRD, HRTEM, DLS, TGA, FTIR, XPS and fluorescence spectroscopy techniques to access structural, morphological and surface properties, to probe biopolymer functionalization and to quantify drug-loading. Charge reversals (±30 mV) after each deposition confirmed polyelectrolyte adsorption and a stable LbL assembly. Magnetic interparticle interaction was reduced in the biopolymeric structure, hinting at an optimized performance in magnetic hyperthermia for magneto-assisted drug release applications. Curcumin was encapsulated, resulting in an enhanced payload (~100 μg/mg). Nanocytotoxicity assays showed that the biopolymer capping enhanced the biocompatibility of nanoplatforms, maintaining entrapped curcumin. Our results indicate the potential of synthesized nanoplatforms as an alternative way of remotely delivering/releasing curcumin for medical purposes, upon application of an alternating magnetic field, demonstrating improved efficiency and reduced toxicity.