Franck Cleymand

In situ glyco-nanostructure formulation via photo-polymerization induced self-assembly

Frequently, the classical self-assembly techniques applied to amphiphilic glycopolymers lead to primitive morphologies, i.e. spherical micelles/nanoparticles. Herein, we report a facile and rapid one-pot synthesis and self-assembly of grafted amphiphilic glycopolymers using photo-initiated Polymerization-Induced Self-Assembly (Photo-PISA) under UV-irradiation at room temperature. Such glycopolymers were based on dextran as a hydrophilic steric stabilizer backbone and poly(hydroxypropyl methacrylate) PHPMA as a hydrophobic graft. Transmission electron microscopy and light scattering analysis reveal the formation of a broad set of advanced glyco-nanostructures ranging from spherical micelles to worm-like micelles and vesicles depending on both the PHPMA graft length and the solids content.

Influence of recasting on the quality of dental alloys: A systematic review.

STATEMENT OF PROBLEM Dental alloy manufacturers advise against the reuse of previously melted alloy. However, for economic reasons, dental laboratories often reuse the casting surplus (sprue and metal remaining in the crucible former). Such reuse remains a controversial topic in dental practice. PURPOSE The purpose of this systematic review was to assess the effects of remelting dental alloys by evaluating the following parameters: reasons for recasting and associated processes, feasible number of recastings, treatment of alloys before recasting and its effects on cytotoxicity, color of opaque porcelain, castability of alloys, marginal accuracy, mechanical properties, porcelain-metal interfaces, and corrosion. MATERIAL AND METHODS The systematic review included all studies on dental alloy recasting. MEDLINE, Dentistry and Oral Science Source, Science Direct, and ISI Web of Science were searched (up to July 2014). Data were extracted and the quality of studies was assessed. RESULTS Thirty-four studies published between 1983 and 2014 were included. The number of recastings ranged from 1 to 10. The percentage of new alloy ranged from 0 to 100 wt%, although the mean value was 50 wt%. CONCLUSIONS Evidence for the feasibility of adding 50% new metal at each recasting is limited. The number of recastings should be limited to a maximum of 4. No general test protocol can be deduced from these studies, which limits the comparison and exploitation of data. Furthermore, no consensus protocol exists for the evaluation of recasting. Future studies should work toward establishing a standard protocol.

Local Modification of the Microstructure and Electrical Properties of Multifunctional Au–YSZ Nanocomposite Thin Films by Laser Interference Patterning

Nanocomposite films consisting of gold nanoparticles embedded in an yttria-stabilized zirconia matrix (Au-YSZ) have been synthesized with different gold loadings by reactive magnetron sputtering followed by ex situ annealing in air or laser interference patterning (LIP) treatment. It is shown that the electrical conductivity of the nanocomposite films can be modified to a large extent by changing the gold loading, by thermal annealing, or by LIP. The structural and microstructural analyses evidenced the segregation of metallic gold in crystalline form for all synthesis conditions and treatments applied. Thermal annealing above 400 °C is observed to trigger the growth of pre-existing nanoparticles in the volume of the films. Moreover, pronounced segregation of gold to the film surface is observed for Au/(Au + Zr + Y) ratios above 0.40, which may prevent the use of thermal annealing to functionalize gold-rich Au-YSZ coatings. In contrast, significant modifications of the microstructure were detected within the interference spot (spot size close to 2 × 2 mm) of LIP treatments only for the regions corresponding to constructive interference. As a consequence, besides its already demonstrated ability to modify the friction behavior of Au-YSZ films, the LIP treatment enables local tailoring of their electrical resistivity. The combination of these characteristics can be of great interest for sliding electrical contacts.

Multiscale characterization of the hierarchical structure of Dynastes hercules elytra

Beetle elytra are thickened forewings, they are lightweight and tough to protect the hindwings without hindering flight capacities. Dynastes hercules elytra are known for their hygrochromic properties. However, the whole structure of the elytron remains to be characterized. Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and to our knowledge for the first time X-Ray tomography were undertaken on adult male Dynastes hercules to characterize their multi-scale structure. Trabeculae present a periodic arrangement over a short distance. Two inferred models describe the heights of plies in endocuticles of dorsal and ventral cuticles. We hypothesize that this study could provide inspiration for biomimetic materials.

Synthesis and Characterization of Nanofunctionalized Gelatin Methacrylate Hydrogels

Given the importance of the extracellular medium during tissue formation, it was wise to develop an artificial structure that mimics the extracellular matrix while having improved physico-chemical properties. That is why the choice was focused on gelatin methacryloyl (GelMA), an inexpensive biocompatible hydrogel. Physicochemical and mechanical properties were improved by the incorporation of nanoparticles developed from two innovative fabrication processes: High shear fluid and low frequencies/high frequencies ultrasounds. Both rapeseed nanoliposomes and nanodroplets were successfully incorporated in the GelMA networks during the photo polymerization process. The impact on polymer microstructure was investigated by Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and enzymatic degradation investigations. Mechanical stability and viscoelastic tests were conducted to demonstrate the beneficial effect of the functionalization on GelMA hydrogels. Adding nanoparticles to GelMA improved the surface properties (porosity), tuned swelling, and degradability properties. In addition, we observed that nanoemulsion didn’t change significantly the mechanical properties to shear and compression solicitations, whereas nanoliposome addition decreased Young’s modulus under compression solicitations. Thus, these ways of functionalization allow controlling the design of the material by choosing the type of nanoparticle (nanoliposome or nanoemulsion) in function of the application.

Elaboration of hydroxyapatite nanoparticles and chitosan/hydroxyapatite composites: a present status

Novel formulations of nano-hydroxyapatite (nano-HAp) and nano-HAp/chitosan composites have attracted much attention in these last years. The use of natural chitosan is found to be potential for fabrication of modified nano-HAp with many biomedical applications such as orthopedic, osteoconductive, dental and drug delivery applications. This review summarizes the different techniques employed for the elaboration of HAp nanoparticles and the effect of the incorporation of HAp with chitosan on the fabrication of nano-HAp composite and on their physical properties. We discuss the effects of the reaction conditions such as reaction time, temperature, pH, solvent nature, surfactants, and concentration of reactants on crystallinity, particle size, morphology and properties of nano-HAp composite. The nano-HAp progress and the present status of HAp (either experimental or theoretical results) have been reviewed.

Bioactive Films Containing Alginate-Pectin Composite Microbeads with Lactococcus lactis subsp. lactis: Physicochemical Characterization and Antilisterial Activity

Novel bioactive films were developed from the incorporation of Lactococcus lactis into polysaccharide films. Two different biopolymers were tested: cellulose derivative (hydroxylpropylmethylcellulose (HPMC)) and corn starch. Lactic acid bacteria (LAB) free or previously encapsulated in alginate-pectin composite hydrogel microbeads were added directly to the film forming solution and films were obtained by casting. In order to study the impact of the incorporation of the protective culture into the biopolymer matrix, the water vapour permeability, oxygen permeability, optical and mechanical properties of the dry films were evaluated. Furthermore, the antimicrobial effect of bioactive films against Listeria monocytogenes was studied in synthetic medium. Results showed that the addition of LAB or alginate-pectin microbeads modified slightly films optical properties. In comparison with HPMC films, starch matrix proves to be more sensitive to the addition of bacterial cells or beads. Indeed, mechanical resistance of corn starch films was lower but barrier properties were improved, certainly related to the possible establishment of interactions between alginate-pectin beads and starch. HPMC and starch films containing encapsulated bioactive culture showed a complete inhibition of listerial growth during the first five days of storage at 5 °C and a reduction of 5 logs after 12 days.

Crystal structure and DFT study of the zwitterionic form of 3-{(E)-1-[(4-ethoxyphenyl)iminiumyl]ethyl}-6-methyl-2-oxo-2H-pyran-4-olate

The title Schiff base compound crystallizes in the zwitterionic form. The resulting iminium and hydroxyl groups are linked by a charge-assisted intramolecular N+—H⋯O− hydrogen bond, and the conformation about the C=N bond is E.

Membranes combining chitosan and natural-origin nanoliposomes for tissue engineering

Chitosan thin films, elaborated by solvent casting, were functionalized by incorporating nanoliposomes based on natural vegetable (soy based) and marine (salmon derived) lecithin. The marine lecithin used in this study contains a higher percentage of polyunsaturated fatty acids (PUFAs) and polar lipids compared with vegetal lecithin. The physical-chemistry properties of the obtained films were characterized by water contact angle (WCA), Fourier Transform InfraRed spectroscopy (FT-IR), water uptake test, and Torsional Harmonic Atomic Force Microscopy analysis (TH-AFM). The surface wettability, swelling ratio, roughness and local stiffness of the thin films can be modified and controlled by adding nanoliposomes. The WCA decreased with the increase of the amount of nanoliposomes. Equilibrium water uptakes of about 170% were achieved in 24 h for the different formulations. The FT-IR results showed the existence of chemical interactions between chitosan and nanoliposomes. The surface topography of the films were identical in terms of asymmetry and amplitude distribution of roughness measurements but showed a significant increase of asperity height when incorporating soya nanoliposomes. This variation is accompanied with a decrease in the average of surface rigidity and of adhesive force value, resulting in a heterogeneous surface. The behaviour of human mesenchymal stem cells (hMSCs) cultured on the films was investigated. Results showed that the films favor cell proliferation when the concentration of soya and salmon nanoliposomes is below 2 mg mL−1 and 4 mg mL−1, respectively. The highest cell proliferation of hMSCs culture was observed when the concentration of salmon nanoliposomes was 1 mg mL−1. This work provides evidence that nanoliposome-functionalized chitosan thin films could offer adequate cyto-friendly cell culture supports for hMSCs, and may potentially be used as suitable scaffolds for tissue engineering applications.

Crystal structure of (E)-4-hy-droxy-3-{1-[(4-hy-droxy-phen-yl)imino]-eth-yl}-6-methyl-2H-pyran-2-one.

In the title Schiff base, C14H13NO4, which adopts the phenol–imine tautomeric form, the dihedral angle between the planes of the benzene and heterocyclic (r.m.s. deviation = 0.037 Å) rings is 53.31 (11)°. An intramolecular O—H⋯N hydrogen bond closes an S(6) ring. In the crystal, molecules are linked by O—H⋯O hydrogen bonds to generate C(11) chains propagating in the [010] direction. A weak C—H⋯O link is also observed, leading to the formation of R 5 5(32) rings extending parallel to the (101) plane.