60 research outputs found
The role of the coating and aggregation state in the interactions between iron oxide nanoparticles and 3T3 fibroblasts
Recent nanotoxicity studies revealed that the physico-chemical
characteristics of engineered nanomaterials play an important role in the
interactions with living cells. Here, we report on the toxicity and uptake of
the iron oxide sub-10 nm nanoparticles by NIH/3T3 mouse fibroblasts. Coating
strategies include low-molecular weight ligands (citric acid) and polymers
(poly(acrylic acid), MW = 2000 g mol-1). We find that most particles were
biocompatible, as exposed cells remained 100% viable relative to controls. The
strong uptake shown by the citrate-coated particles is related to the
destabilization of the dispersions in the cell culture medium and their
sedimentation down to the cell membranes.Comment: 5 pages 3 figure
Microrheology of viscoelastic solutions studied by magnetic rotational spectroscopy
Magnetic rotational spectroscopy is based on the use of magnetic micron-size
wires for viscosity measurements. Submitted to a rotational magnetic field with
increasing frequency, the wires undergo a hydrodynamic instability between a
synchronous and an asynchronous regime. From a comparison between predictions
and experiments, the static shear viscosity and elastic modulus of wormlike
micellar solutions are here determined. The values agree with the determination
by cone-and-plate rheometry.Comment: 6 pages, 4 figures, proceedings of the TNT2015 conference in Toulous
Rotational microrheology of Maxwell fluids using micron-sized wires
We demonstrate a simple method for rotational microrheology in complex
fluids, using micrometric wires. The three-dimensional rotational Brownian
motion of the wires suspended in Maxwell fluids is measured from their
projection on the focal plane of a microscope. We analyze the mean-squared
angular displacement of the wires of length between 1 and 40 microns. The
viscoelastic properties of the suspending fluids are extracted from this
analysis and found to be in good agreement with macrorheology data. Viscosities
of simple and complex fluids between 0.01 and 30 Pa.s could be measured. As for
the elastic modulus, values up to ~ 5 Pa could be determined. This simple
technique, allowing for a broad range of probed length scales, opens new
perspectives in microrheology of heterogeneous materials such as gels, glasses
and cells.Comment: to appear in Soft Matte
Design and applications of a fluorescent labeling technique for lipid and surfactant preformed vesicles
International audienceAmphiphilic molecules such as surfactants, lipids and block copolymers can be assembled into bilayers and form vesicles. Fluorescent membrane labeling methods require the use of dye molecules that can be inserted in the bilayers at different stages of the synthesis. To our knowledge there is no generalized method for labeling preformed vesicles. Herein we develop a versatile protocol that is suitable to both surfactant and lipid preformed vesicles and requires no separation or purification steps. Based on the lipophilic carbocyanine green dye PKH67, the methodology is assessed on zwitterionic phosphatidylcholine vesicles. To demonstrate its versatility, it is applied to dispersions of anionic or cationic vesicles, such as a drug administrated to premature infants with respiratory distress syndrome, or a vesicle formulation used as a fabric softener for homecare applications. By means of fluorescence microscopy we then visualize the interaction mechanisms of nano-particles crossing live cell membranes and of surfactant adsorbing on cotton fabric. These results highlight the advantages of a membrane labeling technique that is simple and applicable to a large number of soft matter systems
Cerium oxide catalyzed disproportionation of hydrogen peroxide: a closer look at the reaction intermediate
Cerium oxide nanoparticles (CNPs) have recently gained increasing interest as
redox enzyme-mimetics to scavenge the intracellular excess of reactive oxygen
species, including hydrogen peroxide (H2O2). Despite the extensive exploration
of CNP scavenging activity, there remains a notable knowledge gap regarding the
fundamental mechanism underlying the CNP catalyzed disproportionation of H2O2.
In this Letter, we present evidence demonstrating that H2O2 adsorption at CNP
surface triggers the formation of stable intermediates known as ceriumperoxo
complexes (Ce-O2 2-). The cerium-peroxo complexes can be resolved by Raman
scattering and UV-Visible spectroscopy. We further demonstrate that the
catalytic reactivity of CNPs in the H2O2 disproportionation reaction increases
with the Ce(III) fraction. The developed approach using UV-Visible spectroscopy
for the characterization of Ce-O2 2-complexes can potentially serve as a
foundation for determining the catalytic reactivity of CNPs in the
disproportionation of H2O2
Towards a better understanding on agglomeration mechanisms and thermodynamic properties of TiO2 nanoparticles interacting with natural organic matter
Interaction between engineered nanoparticles and natural organic matter is
investigated by measuring the exchanged heat during binding process with
isothermal titration calorimetry. TiO2 anatase nanoparticles and alginate are
used as engineered nanoparticles and natural organic matter to get an insight
into the thermodynamic association properties and mechanisms of adsorption and
agglomeration. Changes of enthalpy, entropy and total free energy, reaction
stoichiometry and affinity binding constant are determined or calculated at a
pH value where the TiO2 nanoparticles surface charge is positive and the
alginate exhibits a negative structural charge. Our results indicate that
strong TiO2-alginate interactions are essentially entropy driven and
enthalpically favorable with exothermic binding reactions. The reaction
stoichiometry and entropy gain are also found dependent on the mixing order.
Finally correlation is established between the binding enthalpy, the reaction
stoichiometry and the zeta potential values determined by electrophoretic
mobility measurements. From these results two types of agglomeration mechanisms
are proposed depending on the mixing order. Addition of alginate in TiO2
dispersions is found to form agglomerates due to polymer bridging whereas
addition of TiO2 in alginate promotes a more individually coating of the
nanoparticles.Comment: 30 pages, 6 figures, 11 figures in S
A health concern regarding the protein corona, aggregation and disaggregation
Nanoparticle (NP)-protein complexes exhibit the correct identity of NP in
biological media. Therefore, protein-NP interactions should be closely explored
to understand and to modulate the nature of NPs in medical implementations.
This review focuses mainly on the physicochemical parameters such as dimension,
surface chemistry, the morphology of NPs and influence of medium pH on the
formation of protein corona and conformational changes of adsorbed proteins by
different kinds of methods. Also, the impact of protein corona on the colloidal
stability of NPs is discussed. Uncontrolled protein attachment on NPs may bring
unwanted impacts such as protein denaturation and aggregation. In contrast,
controlled protein adsorption by optimal concentration, size, pH and surface
modification of NPs may result in potential implementation of NPs as
therapeutic agents especially for disaggregation of amyloid fibrils. Also, the
effect of NPs-protein corona on reducing the cytotoxicity and clinical
implications such as drug delivery, cancer therapy, imaging and diagnosis will
be discussed. Validated correlative physicochemical parameters for NP-protein
corona formation frequently derived from protein corona fingerprints of NPs
which are more valid than the parameters obtained only on the base of NP
features. This review may provide useful information regarding the potency as
well as the adverse effects of NPs to predict their behavior in the in vivo
experiments.Comment: 40 pages, 20 figure
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