Effect of architecture disorder on the elastic response of two-dimensional lattice materials.

We examine how disordering joint position influences the linear elastic behavior of lattice materials via numerical simulations in two-dimensional beam networks. Three distinct initial crystalline geometries are selected as representative of mechanically isotropic materials with low connectivity, mechanically isotropic materials with high connectivity, and mechanically anisotropic materials with intermediate connectivity. Introducing disorder generates spatial fluctuations in the elasticity tensor at the local (joint) scale. Proper coarse-graining reveals a well-defined continuum-level scale elasticity tensor. Increasing disorder aids in making initially anisotropic materials more isotropic. The disorder impact on the material stiffness depends on the lattice connectivity: Increasing the disorder softens lattices with high connectivity and stiffens those with low connectivity, without modifying the scaling between elastic modulus and density (linear scaling for high connectivity and cubic scaling for low connectivity). Introducing disorder in lattices with intermediate fixed connectivity reveals both scaling: the linear scaling occurs for low density, the cubic one at high density, and the crossover density increases with disorder. Contrary to classical formulations, this work demonstrates that connectivity is not the sole parameter governing elastic modulus scaling. It offers a promising route to access novel mechanical properties in lattice materials via disordering the architectures.

Combining surface chemistry modification and in situ small-angle scattering characterization to understand and optimize the biological behavior of nanomedicines.

Nanomedicines are considered as promising therapeutics for cancer treatment. However, clinical translation is still scarce, partly because their biological behavior is not well understood. Extracting general guidelines from the great variety of nanoparticles and conditions studied is indeed difficult, and relevant techniques are lacking to obtain in situ information. Here, both issues are solved by combining versatile model nanoparticles with in situ tools based on small-angle scattering techniques (SAS). The strategy was to develop a library of nanoparticles and perform systematic study of their interactions with biological systems. Considering the promising properties of gold nanoparticles as cancer therapeutics, polymethacrylate-grafted gold nanoparticles were chosen as models. Modulation of polymer chemistry was shown to change the surface properties while keeping the same structure for all nanoparticles. This unity allowed reliable comparison to extract general principles, while the synthesis versatility enabled to fine-tune the nanoparticles surface properties, especially through copolymerization, and thus to optimize their biological behavior. Two specific aspects were particularly examined: colloidal stability and cell uptake. Positive charges and hydrophobicity were identified as key parameters influencing toxicity and internalization. In situ SAS gave valuable information about nanoparticles evolution in biologically relevant environments. Good colloidal stability was thereby shown in cell culture media, while intracellular transformation and quantity of nanoparticles were monitored, highlighting the potential of these techniques for nanomedicines studies.

Determining the morphology and concentration of core-shell Au/Ag nanoparticles.

Accurately measuring the shape, structure and concentration of nanoparticles (NPs) is a crucial step towards understanding their formation and a prerequisite for any applications. While determining these parameters for single-metal NPs is by now rather routine, reliably characterizing bimetallic NPs is still a challenge. Using four complementary techniques: transmission electron microscopy (TEM), light absorbance spectroscopy (AS), small-angle X-ray scattering (SAXS) and inductively coupled plasma mass spectrometry (ICP-MS) we study bimetallic nanoparticles obtained by growing a silver shell on top of a gold seed. The initial quasi-spherical objects become faceted and grow into a rounded cube as the molar silver-to-gold ratio K increases. The shape evolution is well described by SAXS and TEM. The shell thickness, overall size polydispersity and number particle concentration obtained by the various methods are in good agreement, validating the use of non-invasive in situ techniques such as AS and SAXS for the study of bimetallic NPs.

Improving 131I Radioiodine Therapy By Hybrid Polymer-Grafted Gold Nanoparticles.

BACKGROUND: Human trials combining external radiotherapy (RT) and metallic nanoparticles are currently underway in cancer patients. For internal RT, in which a radioisotope such as radioiodine is systemically administered into patients, there is also a need for enhancing treatment efficacy, decreasing radiation-induced side effects and overcoming radio-resistance. However, if strategies vectorising radioiodine through nanocarriers have been documented, sensitizing the neoplasm through the use of nanotherapeutics easily translatable to the clinic in combination with the standard systemic radioiodine treatment has not been assessed yet. METHOD AND MATERIALS: The present study explored the potential of hybrid poly(methacrylic acid)-grafted gold nanoparticles to improve the performances of systemic 131I-mediated RT on cancer cells and in tumor-bearing mice. Such nanoparticles were chosen based on their ability previously described by our group to safely withstand irradiation doses while exhibiting good biocompatibility and enhanced cellular uptake. RESULTS: In vitro clonogenic assays performed on melanoma and colorectal cancer cells showed that poly(methacrylic acid)-grafted gold nanoparticles (PMAA-AuNPs) could efficiently lead to a marked tumor cell mortality when combined to a low activity of radioiodine, which alone appeared to be essentially ineffective on tumor cells. In vivo, tumor enrichment with PMAA-AuNPs significantly enhanced the killing potential of a systemic radioiodine treatment. CONCLUSION: This is the first report of a simple and reliable nanomedicine-based approach to reduce the dose of radioiodine required to reach curability. In addition, these results open up novel perspectives for using high-Z metallic NPs in additional molecular radiation therapy demonstrating heterogeneous dose distributions.

Mercury(II) Binding to Metallothionein in Mytilus edulis revealed by High Energy-Resolution XANES Spectroscopy.

Of all divalent metals, mercury (HgII ) has the highest affinity for metallothioneins. HgII is considered to be enclosed in the α and ß domains as tetrahedral α-type Hg4 Cys11-12 and ß-type Hg3 Cys9 clusters similar to CdII and ZnII . However, neither the four-fold coordination of Hg nor the existence of Hg-Hg atomic pairs have ever been demonstrated, and the HgII partitioning among the two protein domains is unknown. Using high energy-resolution XANES spectroscopy, MP2 geometry optimization, and biochemical analysis, evidence for the coexistence of two-coordinate Hg-thiolate complex and four-coordinate Hg-thiolate cluster with a metacinnabar-type (ß-HgS) structure in the α domain of separate metallothionein molecules from blue mussel under in vivo exposure is provided. The findings suggest that the CXXC claw setting of thiolate donors, which only exists in the α domain, acts as a nucleation center for the polynuclear complex and that the five CXC motifs from this domain serve as the cluster-forming motifs. Oligomerization is driven by metallophilic Hg⋅⋅⋅Hg interactions. Our results provide clues as to why Hg has higher affinity for the α than the ß domain. More generally, this work provides a foundation for understanding how metallothioneins mediate mercury detoxification in the cell under in vivo conditions.

Contribution to Accurate Spherical Gold Nanoparticle Size Determination by Single-Particle Inductively Coupled Mass Spectrometry: A Comparison with Small-Angle X-ray Scattering.

Small-angle X-ray scattering spectroscopy (SAXS) is the method of choice for nanoparticle diameter and concentration determination. On the one hand, it is metrologically traceable for spherical nanoparticle mean diameter determination and does not require any sample preparation or calibration. On the other hand, single-particle inductively coupled mass spectrometry (SPICPMS) is still under development and requires involved process clarification and accuracy improvement. The strategy of this study is the comparison of the two techniques to study comprehensively SPICPMS performance and observe phenomena otherwise hidden. Six spherical gold nanoparticle suspensions distributed over a large size range (30, 50, 60, 80,100, and 150 nm) are studied as calibration points. Potential matrix effects are eliminated by stabilizing nanoparticles with chitosan in HCl. Chitosan encapsulates nanoparticles, stabilizes their dispersion, and protects them from dissolution. Detection counting/analogue threshold and timeout appear as the relevant parameters for transient signals. They show an influence not only on mean signal but also on signal distribution. The detection tuning proposed allows to linearly calibrate the nanoparticle distribution signal to cubed diameter over the entire range studied with no sensitivity diminution. Comparing the three classical transport efficiency methods, size transport efficiency is shown as the most accurate. The new procedure is validated analyzing three gold nanoparticle suspensions (135, 40, and 50 nm). The results are consistent with SAXS measurements.

Carbon nanotube-copper ferrite-catalyzed aqueous 1,3-dipolar cycloaddition of in situ-generated organic azides with alkynes.

A novel nanohybrid catalyst was developed by assembling copper ferrite nanoparticles on carbon nanotubes. The supramolecular catalyst was applied to the one-pot azidation/1,3-dipolar cycloaddition of various substrates, at room temperature, and in an aqueous medium. The nanohybrid could also be recycled and reused by means of magnetic recovery.

The challenge of studying TiO2 nanoparticle bioaccumulation at environmental concentrations: crucial use of a stable isotope tracer.

The 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 (47)Ti. Thanks to the (47)Ti labeling, we could detect the bioaccumulation of NPs in zebra mussels (Dreissena polymorpha) exposed for 1 h at environmental concentrations via water (7-120 µg/L of (47)TiO2 NPs) and via their food (4-830 µg/L of (47)TiO2 NPs mixed with 1 × 10(6) 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.

Selective conversion of nitroarenes using a carbon nanotube-ruthenium nanohybrid.

Ruthenium nanoparticles were assembled on carbon nanotubes and the resulting nanohybrid was used in the hydrazine-mediated catalytic hydrogenation of various nitroarenes, at room temperature. Depending on the solvent, a selective transformation occurred, giving either access to the corresponding aniline or hydroxylamine derivative.

Co-catalytic oxidative coupling of primary amines to imines using an organic nanotube-gold nanohybrid.

A novel nanohybrid structure was synthesized by assembling gold nanoparticles on polymerized polydiacetylene nanotubes. Combination of the nanohybrid with gallacetophenone afforded an efficient cooperative co-catalytic system for the oxidative coupling of primary amines into imines. The system is highly efficient and sustainable as it operates in high yields using minimal amounts of the metal and the quinone, under ambient atmosphere, at room temperature, in water, and is easily recycled.

Behavior and determination of titanium dioxide nanoparticles in nitric acid and river water by ICP spectrometry.

ICP spectrometry (ICPMS, ICPOES) are classical techniques for the determination of solubilized or suspended elements. Unfortunately, their relevance for nanoparticles at low concentration (below 10 ppm) is rarely called into question, even if literature reports are not always coherent. This work is a systematic study based on the measurement of TiO2 nanoparticle suspensions, as a model of quasi-insoluble material, by plasma spectrometry. It studies both sample treatment and measurement in the 10 ppb to 30 ppm concentration range. Realized on a set of four engineered nanoparticles suspensions at low concentration, it shows the existence of three different regimes of stability that affect concentration measurement. Above a C(S) stability concentration value, suspensions are stable in time; below a low-concentration C(E) value, the signal loss is at a maximum, and a final partition is reached between the container walls and the suspension. Between these two regimes, the suspension aging varies with concentration. C(E) and C(S) depend on nanoparticle characteristics and the suspension medium, whereas the evolution kinetic is volume-dependent. Because TiO2 nanoparticles are present in the environment at concentrationd below C(S), it is then necessary to find a way to rehomogenize the suspension between sampling and analyzing. Soft sonication, minimizing the sample temperature, and trapping of free radicals is proposed and evaluated. Homogenization is traced by the addition of an internal standard before storage. The procedure is applied to a real sample, Seine River water. The amount of total titanium found, 48.7 ppb, is in good agreement with the result of the reference method.

Separation and analysis of lanthanides by isotachophoresis coupled with inductively coupled plasma mass spectrometry.

This study is a large project initiated by the French Nuclear Agency, and concerns the development of a new electrolyte system for the separation of lanthanides by isotachophoresis. This new system is based on a leading electrolyte that incorporates 2-hydroxy-2-methylbutyric acid as complexing agent. The optimization of separation conditions (complexing agent concentration, pH, capillary dimensions, injection conditions, and current intensity) performed by experiments on a commercial capillary instrument with contactless conductivity detection, which allows to improve the separation of 13 lanthanides (La to Lu, except Pm and Ho). We have also directly coupled the isotachophoresis to an inductively coupled plasma mass spectrometer to visualize the mono-elementary elution bands and demonstrate the potentiality of the method for isotope ratio measurements. The application to a simulated solution representative of a fraction of fission products present in a MOX spent fuel is presented in this paper to demonstrate the possible application in future on nuclear fuel samples.

Stability constants determination of successive metal complexes by hyphenated CE-ICPMS.

The study of radionuclides speciation requires accurate evaluation of stability constants, which can be achieved by CE-ICPMS. We have previously described a method for 1:1 metal complexes stability constants determination. In this paper, we present its extension to the case of successive complexations and its application to uranyl-oxalate and lanthanum-oxalate systems. Several significant steps are discussed: analytical conditions choice, mathematical treatment by non-linear regression, ligand concentration and ionic strength corrections. The following values were obtained: at infinite dilution, log(beta(1) degrees (UO(2)Oxa))=6.93+/-0.05, log(beta(2) degrees (UO(2)(Oxa)(2) (2-)))=11.92+/-0.43 and log(beta(3) degrees (UO(2)(Oxa)(3) (4-)))=15.11+/-0.12; log(beta(1) degrees (LaOxa(+)))=5.90+/-0.07, log(beta(2) degrees (La(Oxa)(2) (-)))=9.18+/-0.19 and log(beta(3) degrees (La(Oxa)(3) (3-)))=9.81+/-0.33. These values are in good agreement with the literature data, even though we suggest the existence of a new lanthanum-oxalate complex: La(Oxa)(3) (3-). This study confirms the suitability of CE-ICPMS for complexation studies.

Metal complexes stability constant determination by hyphenation of capillary electrophoresis with inductively coupled plasma mass spectrometry: the case of 1:1 metal-to-ligand stoichiometry.

Nuclear energy development has raised new issues like radionuclides biogeochemistry. The modelling of their biochemical properties involves the accurate determination of thermodynamical data, like stability constants. This can be achieved by using hyphenated capillary electrophoresis (CE)-ICPMS and the method was applied successfully on 1:1 lanthanum-oxalate and uranyl-oxalate complexes. Several significant steps are discussed: choice of analytical conditions, electrophoretic mobility calculation, mathematical treatment of experimental data by using linear regressions, ligand concentration and ionic strength corrections. The following values were obtained with a good precision for lanthanum-oxalate and uranyl-oxalate complexes: log(K degrees (LaOxa(+)))=6.10+/-0.10 and log(K degrees (UO(2)Oxa))=6.40+/-0.30, respectively, at infinite dilution. These values are consistent with the literature data, showing CE-ICPMS potential for metal complexes stability constants determination.