Investigation of the surface reactivity of a sol-gel derived glass in the ternary system SiO2-CaO-P2O5

A new glass formulation, with the molar composition 60% SiO₂-35% CaO-5% P₂O₅, was synthesized using the sol-gel process, for applications as biomaterial in orthopaedic or maxillo facial surgery. Pellets, made of glass powder, were uniaxially compacted and soaked in simulated body fluid (SBF) for up to 7 days at 37 °C to evaluate glass bioactivity. Ionic exchanges at the interface glass-SBF were evaluated by studying evolutions of calcium, phosphorus and silicon concentrations in SBF using ICP-OES. Changes in glass surface, and the formation of crystalline phases were analyzed using XRD, SEM, EDS and FTIR methods.Results form ICP-OES showed a high reactivity of the glass surface with a very high and continuous release of calcium, a limited glass dissolution and an uptake of phosphorous from SBF. Results from both FTIR and XRD analysis indicated that the glass surface was progressively covered by two different phases: CaCO₃ as calcite and a carbonated apatite layer. The formation of these phases, following two different schemas, was observed after 2 h of immersion and confirmed after 7 days. SEM micrographs and EDS analysis demonstrated that the main phase, a carbonated apatite, was present as micro-spheroids and the secondary phase, calcite, was materialized by agglomerates which have diameters up to 10-15 μm. These results are in accordance with a bioactive feature of the glass studied.     

Surface Assisted Nucleation and Growth of Polymer Latexes on Organically-Modified Inorganic Particles

Summary: Polymer latex particles were synthesized in the presence of inorganic particles, which had been organically-modified to promote favorable interactions with growing macromolecules. The organic modification was performed using three different routes: (1) surface covalent grafting of vinyl trialkoxysilanes, (2) surface adsorption of polyethylene glycol-based macromonomers, and (3) bulk modification through ion exchange with cationic monomers or cationic initiators. Two types of mineral particles were studied: commercial and self-prepared silica particles (with diameters from 80 nm to 1 µm), and commercial laponite clay particles with a cation exchange capacity of 0.75 meq · g⁻¹. Emulsion polymerization was performed in the presence of styrene or butyl acrylate monomers. The morphologies of the nanocomposite particles were observed by (cryogenic) transmission electron microscopy and correlated to the organic modification procedure.     

Synthesis of composite latex particles filled with silica

Encapsulation of silica nanoparticles was performed by dispersion polymerization of styrene, butyl acrylate and butyl methacrylate in aqueous alcoholic media. Following previous works^1‐3), the silica beads were first modified by reacting on their surface the 3‐trimethoxysilyl propyl methacrylate coupling agent (MPS). In every case, the silica beads are all surrounded by polymer giving composite latex particles filled with silica. Each composite particle contains from one to a great number of silica beads. Changing the size or the concentration of the silica beads, and the experimental conditions for the synthesis of the polymer particles enables to control this number. One can take benefit of this to synthesize model composite particles with controlled compositions.     

Hybrids and biohybrids as green materials for a blue planet

There is an urgency to identify novel technological answers to the decreasing availability of important resources together with increasing accumulation of pollution. Among the many ways materials science can contribute to these issues, the enhanced use of renewable resources, the optimal production of alternative energies and the improved monitoring/cleaning of contaminated environments can be identified as area where the sol–gel technology has, and will have, a major role to play. In this short review, we more specifically illustrate recent developments in biohybrid chemistry applied to bioplastics, biofuel cells, biosensors and bioremediation.     

Analysis of polyethoxylated surfactants in microemulsion-oil-water systems: Part II

Commercial ethoxylated surfactants are always a mixture of oligomers with different ethylene oxide number (EON). The different oligomers were separated by high performance liquid chromatography (HPLC) on an amino column using a mixture of polar and nonpolar mobile phases. Surfactant oil-water-systems were studied according to the unidimensional scan technique. The surfactant content in the oil, microemulsion and water phases was determined by UV spectroscopy and HPLC. The partitioning of the surfactant oligomers in the oil and water phases of a Winsor III system was determined. The effect of different salts on the surfactant partitioning is discussed.     

Combined spectroscopic studies on post-functionalized Au25 cluster as an ATR-FTIR sensor for cations

Recently, significant research activity has been devoted to thiolate-protected gold clusters due to their attractive optical and electronic properties. These properties as well as solubility and stability can be controlled by post-synthetic modification strategies. Herein, the ligand exchange reaction between Au₂₅(2-PET)₁₈ cluster (where 2-PET is 2-phenylethanethiol) and di-thiolated crown ether (t-CE) ligands bearing two chromophores was studied. The post-functionalization aimed to endow the cluster with ion binding properties. The exchange reaction was followed in situ by UV-vis, ¹H NMR and HPLC. MALDI mass analysis revealed the incorporation of up to 5 t-CE ligands into the ligand shell. Once functionalized MALDI furthermore showed complexation of sodium ions to the cluster. ATR-FTIR spectroscopic studies using aqueous solutions of K⁺, Ba²⁺, Gd³⁺ and Eu³⁺ showed noticeable spectral shifts of the C–O stretching band around 1100 cm⁻¹ upon complexation. Further spectral changes point towards a conformational change of the two chromophores that are attached to the crown ether. Density functional theory calculations indicate that the di-thiol ligand bridges two staple units on the cluster. The calculations furthermore reproduce the spectral shift of the C–O stretching vibrations upon complex formation and reveal a conformational change that involves the two chromophores attached to the crown ether. The functionalized clusters have therefore attractive ion sensing properties due to the combination of binding properties, mainly due to the crown ether, and the possibility for signal transduction via an induced conformational change involving chromophore units.

Using ligand exchange reactions an atomically precise gold cluster was functionalized with a di-thiolated crown ether. Using in situ infrared spectroscopy films of the resulting composite were shown to incorporate metal cations.     

Effects of salinity on the viscosity and birefringence of a microemulsion system

Oil/water/surfactant systems form complex equilibrium phases which are sensitive to a number of parameters, including amount and concentration of cosurfactant (often an alcohol), salinity, and temperature. If one of these variables is changed systematically as, for example, the salinity, an interesting transition may be observed in which at low salinities a microemulsion is in equilibrium with an excess oil phase, at moderate salinities a middle phase microemulsion is in equilibrium with both excess oil and excess water phases, and at higher salinities brine is in equilibrium with a microemulsion phase. To help elucidate the structure of the microemulsion, studies of viscoelasticity and streaming birefringence in oscillatory shear flow have been conducted of a middle phase-forming system as a function of salinity. It is found that the viscoelastic properties of the microemulsions are unchanged for shear rates varying from 0.1 to 100 sec⁻¹. Both the birefringence and the viscosity maximize near the salinity marking the transition from lower phase to middle phase microemulsion. Further inflections in these properties occur at a salinity marking the midrange of the middle phase microemulsion. For all cases the dominent relaxation time is near 3 to 5 msec while the birefringence changes by two orders of magnitude. The birefringence is a sensitive indicator of the elastic structure of the microemulsion.     

Study of surfactant–siloxane interfaces in spray-dried mesoporous silica-based spheres

We have undertaken the synthesis of spray-dried mesoporous silica-based micrometric spheres using various synthetic procedures. In this article, we focus on the relationship between textural properties and small organic groups bound to the siloxane network (residual alkoxy groups or added functions). A correlation has been found between the characteristic XRD distance and the quantity of Si-bound organic groups (measured by ¹H solid-state NMR) located at the surfactant–siloxane interface which demonstrates the effect of these organic groups. However, under certain circumstances, Si-bound organic groups can be trapped inside the siloxane network. They have then a different effect on the texture, and are less accessible for further applications. In that sense, this study can also be used in a predictive way for the synthesis of mesoporous spheres with surfaces of functionalised channels.     

3D-QSAR and docking studies of selective GSK-3beta inhibitors. Comparison with a thieno[2,3-b]pyrrolizinone derivative, a new potential lead for GSK-3beta ligands

The three-dimensional structures of 3-anilino-4-arylmaleimides, selective GSK-3beta inhibitors, were correlated to their biological affinities by 3D-QSAR studies (CoMFA method). The cocrystallographic data of GSK-3beta vs 3-anilino-4-arylmaleimide allowed us to compare 3D-QSAR results to experimental intermolecular interactions. The results of the CoMFA analysis did not really correspond to the interactions recorded in the active site, but they characterized fundamental features (areas of the active site) of the interactions ligand-receptor. These studies were the starting point to analyze a new GSK-3beta ligand, a thieno[2,3-b]pyrrolizinone derivative. This comparison based on docking and simulation approaches allowed us to confirm one preferential orientation of this ligand inside the active site, explaining the relationship with the reference 3-anilino-4-arylmaleimide derivatives and its biological affinity.