76 research outputs found
The challenge of studying TiO2 nanoparticle bioaccumulation at environmental concentrations: Crucial use of a stable isotope tracer
International audienceThe ecotoxicity of nanoparticles (NPs) is a growing area of research with many challenges ahead. To be relevant, laboratory experiments must be performed with well-controlled and environmentally realistic (i.e. low) exposure doses. Moreover, when focusing on the intensively manufactured titanium dioxide (TiO2) NPs, sample preparations and chemical analysis are critical steps to meaningfully assay NP?s bioaccumulation. To deal with these imperatives, we synthesized for the first time TiO2 NPs labeled with the stable isotope 47Ti. Thanks to the 47Ti labeling, we could detect the bioaccumulation of NPs in zebra mussels (Dreissena polymorpha) exposed for 1h at environmental concentrations via water (7 - 120 µg/L of 47TiO2 NPs) and via their food (4 ? 830 µg/L of 47TiO2 NPs mixed with 1?106 cells/mL of cyanobacteria) despite the high natural Ti background, which varied in individual mussels. The assimilation efficiency (AE) of TiO2 NPs by mussels from their diet was very low (AE= 3.0±2.7%) suggesting that NPs are mainly captured in mussel gut, with little penetration in their internal organs. Thus, our methodology is particularly relevant in predicting NP?s bioaccumulation and investigating the factors influencing their toxicokinetics in conditions mimicking real environments
Hybrid Nanocomposites with Tunable Alignment of the Magnetic Nanorod Filler
For many important applications, the performance of polymer-anisotropic
particle nanocomposite materials strongly depends on the orientation of the
nanoparticles. Using the very peculiar magnetic properties of goethite
({\alpha}-FeOOH) nanorods, we produced goethite-poly(hydroxyethyl methacrylate)
nanocomposites in which the alignment direction and the level of orientation of
the nanorods could easily be tuned by simply adjusting the intensity of a
magnetic field applied during polymerization. Because the particle volume
fraction was kept low (1-5.5 vol \%), we used the orientational order induced
by the field in the isotropic phase rather than the spontaneous orientational
order of the nematic phase. At the strongest field values (up to 1.5 T), the
particles exhibit almost perfect antinematic alignment, as measured by optical
birefringence and small-angle X-ray scattering. The results of these two
techniques are in remarkably good agreement, validating the use of
birefringence measurements for quantifying the degree of orientational order.
We also demonstrate that the ordering induced by the field in the isotropic
suspension is preserved in the final material after field removal. This work
illustrates the interest, for such problems, of considering the field-induced
alignment of anisotropic nanoparticles in the isotropic phase, an approach that
is effective at low filler content, that avoids the need of controlling the
nematic texture, and that allows tuning of the orientation level of the
particles at will simply by adjusting the field intensity
Temperature Dependence of Water Absorption in the Biological Windows and Its Impact on the Performance of Ag2S Luminescent Nanothermometers
The application of nanoparticles in the biological context generally requires
their dispersion in aqueous media. In this sense, luminescent nanoparticles
are an excellent choice for minimally invasive imaging and local temperature sensing (nanothermometry). For these applications, nanoparticles must
operate in the physiological temperature range (25–50 °C) but also in the nearinfrared spectral range (750–1800 nm), which comprises the three biological
windows of maximal tissue transparency to photons. In this range, water
displays several absorption bands that can strongly affect the optical properties of the nanoparticles. Therefore, a full understanding of the temperature
dependence of water absorption in biological windows is of paramount
importance for applications based on these optical properties. Herein, the
absorption spectrum of water in the biological windows over the 25–65 °C
temperature range is systematically analyzed, and its temperature dependence
considering the coexistence of two states of water is interpreted. Additionally,
to illustrate the importance of state-of-the-art applications, the effects of the
absorption of water on the emission spectrum of Ag2S nanoparticles, the most
sensitive luminescent nanothermometers for in vivo applications to date, are
presented. The spectral shape of the nanoparticles’ emission is drastically
affected by the water absorption, impacting their thermometric performanceThis work was financed by the Spanish Ministerio de Ciencia e
Innovación under project PID2019-106211RB-I00, by the Instituto de
Salud Carlos III (PI19/00565), by the Comunidad Autónoma de Madrid
(S2017/BMD3867 RENIM-CM) and co-financed by the European
structural and investment fund. Additional funding was provided by
the European Union Horizon 2020 FETOpen project NanoTBTech
(801305), the Fundación para la Investigación Biomédica del Hospital
Universitario Ramón y Cajal project IMP21_A4 (2021/0427), and by
COST action CA17140. A.B. acknowledges funding support through
the TALENTO 2019T1/IND14014 contract (Comunidad Autónoma de
Madrid). F.E.M. and L.D.C. acknowledge the financial support received
from the project Shape of Water (PTDC/NAN-PRO/3881/2020) through
Portuguese fund
Inorganic manufactured nanoparticles: how their physicochemical properties influence their biological effects in aqueous environments
International audienceAmong all environmental contaminants, those emerging from nanotechnologies constitute one of the most critical challenges for the coming years. The new properties of nanoparticles are at the heart of current scientific advances and the growing interest in harnessing them brings awareness of potential impacts that we cannot ignore. To date, scientists and industrialists have focused on the manufacture of nanomaterials more than on the assessment of the risks for humans and ecosystems. Few databases exist regarding the amounts released within ecosystems and no specific procedure of recycling has yet been established. However, nanoparticles cannot be considered as molecular pollutants or larger particles, and careful consideration is needed to establish a legal system that is specific. Their novel properties, surface energy and reactivity make it impossible to simply transfer our physicochemical, thermodynamic and toxicological knowledge from the micronscale to the nanoscale. This article highlights, nonexhaustively, the strong relationship existing between the unique properties of metallic and metal oxide nanoparticles and their biological effects on aquatic organisms
- …