Taylor dispersion analysis of metallic-based nanoparticles – A short review

Taylor dispersion analysis (TDA) is an interesting tool for nanoparticle (NP) size determination, feasible using simple capillary electrophoresis apparatus. Based upon the radial diffusion of analytes upon a laminar stream, the diffusion coefficient of species is easily estimable. Moreover, TDA is generally more adequate than conventional dynamic light scattering methodologies as it is less dependent on the polydispersity of the sample, leading to accurate measurement and reliable results. This review provides every paper mentioning the use of TDA for metallic-based NPs size determination. Diverse strategies for the detection of metallic NPs (like UV–visible and inductively coupled plasma–mass spectrometry – ICP–MS – for instance) and interpretation of the Taylorgrams are discussed. Based upon the literature, advices on future prospects are also indicated, especially for the comparison of TDA results with other classical techniques.     

Impact of sodium polyacrylate on the amorphous calcium carbonate formation from supersaturated solution

A detailed in situ scattering study has been carried out on the formation of amorphous calcium carbonate (ACC) particles modulated by the presence of small amounts of sodium polyacrylate chains. The work is aiming at an insight into the modulation of ACC formation by means of two polyacrylate samples differing in their molecular weight by a factor of 50. The ACC formation process was initiated by an in situ generation of CO(3)(2-) ions via hydrolysis of 10 mM dimethylcarbonate in the presence of 10 mM CaCl(2). Analysis of the formation process by means of time-resolved small-angle X-ray and light scattering in the absence of any additives provided evidence for a monomer addition mechanism for the growth of ACC particles. ACC formation under these conditions sets in after a lag-period of some 350 s. In the presence of sodium polyacrylate chains, calcium polyacrylate aggregates are formed during the lag-period, succeeded by a modulated ACC growth in a second step. The presence of anionic polyacrylate chains changed the shape of the growing particles toward loose and less homogeneous entities. In the case of low amounts (1.5-7.5 mg/L) of the long chain additive with 97 kDa, the size of the aggregates is comparable to the size of the successively formed hybrid particles. No variation of the lag-period has been observed in this case. Use of the short chain additive with 2 kDa enabled increase of the additive concentration up to 100 mg/L and resulted in a significant increase of the lag-period. This fact, together with the finding that the resulting hybrid particles remained stable in the latter case, identified short chain sodium polyacrylates as more efficient modulators than long chain polyacrylates.     

Charge stoichiometry inside polyelectrolyte-protein complexes: a direct SANS measurement for the PSSNa-lysozyme system

We study by small angle neutron scattering and UV titration how the ratio of negative to positive charges, [-]/[+](intro), acts on the structure of complexes formed by short negatively charged polyelectrolyte chains (PSS) and globular positively charged proteins (lysozyme). The range of [-]/[+](intro) lies between 0.65 and 3.33. In all ratios, dense primary complexes are formed with radii around 10 nm. The species composition and the water content of the primary complexes are precisely obtained by the systematic use of the contrast matching of (deuterated) polymer or protein in SANS, yielding the compactness and the inner charge ratio [-]/[+](inner). The primary complexes have (i) an inner charge ratio [-]/[+](inner) close to 1 whatever [-]/[+](intro), (ii) a high total volume fraction (0.25-0.4), (iii) a constant radius (75 A) for [-]/[+](intro) 1, and (iv) a shell of PSS chains when [-]/[+](intro) > 1. Moreover, UV titration shows that there are free proteins if [-]/[+](introduced) < 1 and free PSS chains if [-]/[+](intro) is largely superior to 1. Hence, we observe that the primary complexes reach a finite size, controlled by electrostatic repulsion, and then aggregate at a higher scale with a fractal dimension of 2.1 characteristic of reaction-limited colloidal aggregation.     

Synthesis of amine functionalized oxazolines with applications in asymmetric catalysis

This paper describes the synthesis of three classes of amine functionalized oxazolines that have been successfully used in asymmetric catalysis in our laboratory. Failed synthetic routes and significantly improved procedures are discussed including the synthesis of ligands for Nozaki-Hiyama-Kishi (NHK) carbonyl allylation reactions that do not require chromatography for purification.     

Development of machineable bioactive glass ceramics for medical uses

Following a controlled, two-stage phase separation in glasses of the system Na₂O/K₂O---MgO---Al₂O₃---SiO₂---CaO---P₂O₅---F, annealing results in both fluorophlogopite and apetite crystallization. The phlogopite mica crystals make the material machineable, whereas the apatite crystals provide for its bioactivity. Animal tests show direct intergrowth with the bone. Bone cells and blood vessels can be found in the immediate neighbourhood of the implant.     

Wide scale range structure in polyelectrolyte-protein dense complexes: where Sans meets freeze-fracture microscopy

We show in this paper how the combination of SANS and freeze-fracture electron microscopy (FFEM) is a powerful tool to picture the structure of very turbid sample liquids at spatial scales lying from a few A to several microns. In a given range of chain size and species concentrations, primary complexes in the shape of globules are observed by both techniques. SANS allows a precise quantitation of size, inner structure, and composition of these globules, as well as aggregated structure of the globules at larger scales, which is fractal-like, with a Hausdorff dimension 2.1 characteristic of Reaction Limited Aggregation (RCLA). The existence of aggregates is seen by FFEM, but most of all FFEM shows the lack of any further structure at larger scale, up to the micrometer size.     

Untargeted Metabolomics Reveals the Potential Antidepressant Activity of a Novel Adenosine Receptor Antagonist

Depression is the most common mental illness, affecting approximately 4.4% of the global population. Despite many available treatments, some patients exhibit treatment-resistant depression. Thus, the need to develop new and alternative treatments cannot be overstated. Adenosine receptor antagonists have emerged as a promising new class of antidepressants. The current study investigates a novel dual A₁/A_2A adenosine receptor antagonist, namely 2-(3,4-dihydroxybenzylidene)-4-methoxy-2,3-dihydro-1H-inden-1-one (1a), for antidepressant capabilities by determining its metabolic profiles and comparing them to those of two reference compounds (imipramine and KW-6002). The metabolic profiles were obtained by treating male Sprague-Dawley rats with 1a and the reference compounds and subjecting them to the forced swim test. Serum and brain material was consequently collected from the animals following euthanasia, after which the metabolites were extracted and analyzed through untargeted metabolomics using both ¹H-NMR and GC-TOFMS. The current study provides insight into compound 1a’s metabolic profile. The metabolic profile of 1a was similar to those of the reference compounds. They potentially exhibit their antidepressive capabilities via downstream effects on amino acid and lipid metabolism.