Superhydrophobicity of composite surfaces created from polymer blends.

HYPOTHESIS: When they are used alone, some polymers, such as polypropylene, Carnauba wax or polycarbonate allow the creation of superhydrophobic surfaces by spin coating or casting. On the other hand, some other polymers, such as polystyrene, polyvinylacetate or polychloroprene, are unable to render a superhydrophobic surface by these techniques. Using binary mixtures of these two types of polymers in a single common solvent, superhydrophobic composite surfaces can be created. We aim to show that superhydrophobicity is depending on the ratio between the two polymers in the initial blend and their intrinsic wettability. EXPERIMENTS: The transition towards superhydrophobicity is studied on composite surfaces made of various polymers. Surfaces are created with simple coating methods, such as casting or spin-coating, of polymer solutions and letting the solvent evaporate at ambient conditions. FINDINGS: Transitions are sharp and the amount of polypropylene in the blend to achieve superhydrophobicity decreases with the hydrophobicity of the second polymer. Topographic and wettability measurements are performed that show that both effects, topographical and chemical, interplay in the property of superhydrophobicity.

Injectability, microstructure and release properties of sodium fusidate-loaded apatitic cement as a local drug-delivery system.

The introduction of an antibiotic, sodium fusidate (SF), into the liquid phase of calcium carbonate-calcium phosphate (CaCO3-CaP) bone cement was evaluated, considering the effect of the liquid to powder ratio (L/P) on the composition and microstructure of the set cement and the injectability of the paste. In all cases, we obtained set cements composed mainly of biomimetic carbonated apatite analogous to bone mineral. With this study, we evi-denced a synergistic effect of the L/P ratio and SF presence on the injectability (i.e., the filter-pressing pheno-menon was suppressed) and the setting time of the SF-loaded cement paste compared to reference cement (without SF). In addition, the in vitro study of SF release, according to the European Pharmacopoeia recommendations, showed that, regardless of the L/P ratio, the cement allowed a sustained release of the antibiotic over 1month in sodium chloride isotonic solution at 37°C and pH7.4; this release is discussed considering the microstructure characteristics of SF-loaded cements (i.e., porosity, pore-size distribution) before and after the release test. Finally, modelling antibiotic release kinetics with several models indicated that the SF release was controlled by a diffusion mechanism.

Comparison of Physical-chemical and Mechanical Properties of Chlorapatite and Hydroxyapatite Plasma Sprayed Coatings.

Chlorapatite can be considered a potential biomaterial for orthopaedic applications. Its use as plasma-sprayed coating could be of interest considering its thermal properties and particularly its ability to melt without decomposition unlike hydroxyapatite. Chlorapatite (ClA) was synthesized by a high-temperature ion exchange reaction starting from commercial stoichiometric hydroxyapatites (HA). The ClA powder showed similar characteristics as the original industrial HA powder, and was obtained in the monoclinic form. The HA and ClA powders were plasma-sprayed using a low-energy plasma spraying system with identical processing parameters. The coatings were characterized by physical-chemical methods, i.e. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy, including distribution mapping of the main phases detected such as amorphous calcium phosphate (ACP), oxyapatite (OA), and HA or ClA. The unexpected formation of oxyapatite in ClA coatings was assigned to a side reaction with contaminating oxygenated species (O2, H2O). ClA coatings exhibited characteristics different from HA, showing a lower content of oxyapatite and amorphous phase. Although their adhesion strength was found to be lower than that of HA coatings, their application could be an interesting alternative, offering, in particular, a larger range of spraying conditions without formation of massive impurities.