Comparative In Vitro Osteoinductivity Study of HA and α‐TCP/HA Bicalcium Phosphate

A bicalcium phosphate (BCP) bioceramic comprising α‐tricalcium phosphate (α‐TCP) and hydroxyapatite (HA) was prepared by a two‐step sintering. The microstructure of the BCP bioceramic was investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X‐ray diffraction. The in vitro osteoinductivity was evaluated by culturing MG63 osteoblast‐like cells on the BCP bioceramic. Results showed that the BCP bioceramic comprising α‐TCP and HA in a moderate ratio possessed a hardness of 93.7 Hv. The cells spread faster on the BCP bioceramic than those on the commercial HA. It suggested that the BCP bioceramic can enhance osteoinductivity in vivo.     

Valorization of waste thermoset material as a filler in thermoplastic: Mechanical properties of phenolic molding compound waste‐filled PP composites

As most thermoset material, phenolic molding compound (PMC) wastes are an environmental problem. Very few recycling solutions have been proposed so far for this type of material. A mechanical recycling method to valorize these materials is proposed in this work. It relies on the use of phenolic waste as filler in thermoplastic. Such phenolic filler can increase mechanical properties (tensile, flexural) of the matrix, and be used in substitution of traditional particulate fillers such as calcium carbonate or talc. In this study, several morphological parameters influencing the final mechanical properties of a PMC‐filled polypropylene (PP) micro‐composite are studied, such as filler loading rate, particles size distribution of the filler, and interfacial adhesion between the filler and the matrix. Some structural parameters are also studied and linked with mechanical properties, such as dispersion of the filler and crystallinity of the matrix. Finally, the properties of PMC‐filled PP are compared with CaCO₃‐ and talc‐filled PP. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45849.     

Chiral mercaptoacetamides display enantioselective inhibition of histone deacetylase 6 and exhibit neuroprotection in cortical neuron models of oxidative stress

Mercaptoacetamide-based ligands have been designed as a new class of histone deacetylase (HDAC) inhibitors for possible use in the treatment of neurodegenerative diseases. The thiol group of these compounds provides a key binding element for interaction with the catalytic zinc ion, and thus differs from the more typically employed hydroxamic acid based zinc binding groups. Herein we disclose the chemistry and biology of some substituted mercaptoacetamides with the intention of increasing HDAC6 isoform selectivity while maintaining potency similar to their hydroxamic acid analogues. The introduction of a stereocenter α to the thiol group was found to have a considerable impact on HDAC inhibitor potency. These new compounds were also profiled for their therapeutic potential in an in?vitro model of stress-induced neuronal injury and were found to act as nontoxic neuroprotective agents.     

Synthesis and Evaluation of a Series of Bis(pentylpyridinium) Compounds as Antifungal Agents

A series of bis(4‐pentylpyridinium) compounds with a variety of spacers between the pyridinium headgroups was synthesised, and the antifungal activity of these compounds was investigated. Lengthening the alkyl spacer between the pentylpyridinium headgroups from 12 to 16 methylene units resulted in increased antifungal activity against C. neoformans and C. albicans, but also resulted in increased hemolytic activity and cytotoxicity against mammalian cells. However, inclusion of an ortho‐substituted benzene ring in the centre of the alkyl spacer resulted in decreased cytotoxicity and hemolytic activity, while maintaining antifungal potency. Replacement of the alkyl and aromatic‐containing spacers by more hydrophilic ethylene glycol groups resulted in a loss of antifungal activity. Some of the compounds inhibited fungal PLB1 activity, but the low correlation of this inhibition with antifungal potency indicates PLB1 inhibition is unlikely to be the predominant mode of antifungal action of this class of compounds, with preliminary studies suggesting they may act via disruption of fungal mitochondrial function.     

How to increase the safety and efficacy of compounds against neurodegeneration? A multifunctional approach

Successful drug design requires not only the detailed knowledge of the pharmacokinetic and pharmacodynamic profiles of the drug candidate portfolio but also a thorough documentation of the possible toxic effects on humans and the environment. Thus, experimental and computational strategies able to measure or predict specific profiles of designed compounds related to their potential toxicity are highly desired. Moreover, a strategy to avoid toxic effects thus enhancing the potential efficacy of drug candidates is of great interest. To fulfil this aim, the pharmacochemistry research unit at the EPGL has recently developed and improved methodologies that detect the potential human health and environmental hazards of compounds active against neurodegeneration at an early stage. A three-step strategy is presented herein. In particular, i) an alternative index to model the bioconcentration of chemicals in the environment was determined; ii) the antioxidant activity of chemical species against free radicals was evaluated. Moreover, since antioxidants play a key role in both toxicity prevention and neuroprotection, iii) the potential interaction of such compounds with enzymatic targets involved in the neurodegenerative cascade was investigated in silico.     

Morphological and adhesive properties of polypyrrole films synthesized by sonoelectrochemical technique

This paper presents electrochemical synthesis of polypyrrole films under high frequency sonication. The films are characterized in terms of adhesion and surface morphology. Comparison to classical electrosynthesized polypyrrole films is made. In particular, the use of high frequency sonication (500 kHz) during electrodeposition of polypyrrole on Si was reported for the first time. Chronocoulometry was used for polymer films electrosynthesis on Si substrates. Influence of polymer thickness on the rugosity, morphology and adhesion force properties was studied. Scanning Electron Microscopy and mechanical probe profiling showed that sonication led to less rough and more homogeneous surface structure. Adhesion force properties of polypyrrole films were also studied by means of force–distance curves obtained by atomic force microscopy. For polymer films obtained in the absence of sonication, adhesion forces decreases with increase in polymer thickness. On the contrary, for polymer films obtained under sonication, the adhesion of the films decreased when the polymer thickness decreased.     

Surface treatment effects on ceramic matrix composites: Case of a thermal sprayed alumina coating on SiC composites

High-temperature-resistant ceramics are already used for many industrial applications. In response to the growing demand, the need for further research considering the final application and the global behaviour of the material is becoming increasingly apparent. In general, it is possible to comply with many specifications, just by treating the surface of the ceramics. For instance, it is possible to achieve an adequate mechanical strength by depositing a protective layer with different structure and/or chemical composition. Regardless to the specification, the adhesion coating/substrate is the most crucial property to be considered. Conventionally, surface degreasing (applying solvents to remove organic impurities) and grit blasting (corundum) are carried out as a two steps pretreatment prior to the thermal-spraying operation to guarantee a mechanical anchorage of the molten particles to the substrate. However, some substrates are grit-blasting sensitive and therefore, alternative treatments should be considered. In these cases, the adherence of the coating must be attained by others means, either from a chemical point of view by modifying the surface wettability, or from a photonic one.Within this context, this study aims to explore the surface modifications induced on SiC composites (Ceramic Matrix Composites, CMC) before plasma spraying of alumina coatings. The effect of two different pre-treatments, deposition of a silicon bonding layer and short-pulse laser treatment (Nd:YAG), on the coating-substrate interface is investigated. A better chemical affinity between the alumina coating and the silicon carbide CMC has been observed with the silicon bond coating. On the other hand, a mixture of chemical and mechanical interaction induced by a cone-like structure occurs when treating the SiC CMC surface by laser prior thermal-spraying.     

Laser densification of organic coating: Effects of laser wavelength,operating parameters and substrate properties

Mechanical bonding and interface behaviour play a key role for any materials deposited on different substrates. Usually, a post-spray heat treatment is required to improve the coating morphology and to enhance mechanical properties of thermal-sprayed polymeric coating. The effects of YAG, CO₂ and diode laser radiations on as-sprayed PEEK coating deposited on stainless steel and aluminum substrates were investigated. The results revealed a good coating densification and interface behavior. A correlation between coating and substrate absorption coefficients, their thermophysical properties and laser operating parameters was shown. Besides, the finite element modeling based on IR temperature measurements during diode laser irradiation demonstrated that the densification of organic coating occurs above its melting point.