High-performance bilayer composites for the replacement of osteochondral defects.

Osteochondral (OC) defects combine damage to cartilage and subchondral bone, posing a significant challenge to their repair due to the dissimilar characteristics and regenerative capabilities between the two tissues. Here, we propose novel OC bilayer composites, drawing inspiration from corresponding biological tissues and using a combination of simple and reproducible techniques. Cartilage-like materials based on poly(vinyl alcohol) (PVA) hydrogels were produced with nanofiber reinforcements acquired from high-performance fibers (Kevlar® and Zylon®), while bone-like materials were obtained by adding magnesium-substituted calcium phosphate ceramics to PVA. All composites were sterilized by gamma irradiation to rule out the possibility of undesirable effects resulting from the process, and then fully characterized. The results indicated that nanofibers and bioceramics incorporated into the PVA networks form promising structures with multiple interesting properties. The composites resembling cartilage and bone showed high biomimicry with natural tissues, being able to reconcile exceptional mechanics with the requirements of adequate porosity, liquid content, and biological behavior. The developed materials reveal a high potential for use in OC tissue repair applications.

Two modes of linear layer-by-layer growth of nanoparticle--polylectrolyte multilayers and different interactions in the layer-by-layer deposition.

The structure of the multilayer assemblies of yttrium iron garnet nanoparticles (YIG) with polyelectrolytes was investigated with the emphasis on the control of the particle density in the adsorption layers. It was found that the growth of YIG films prepared by the layer-by-layer assembly can occur via two deposition modes: (1) sequential adsorption of densely packed adsorption layers (normal growth mode) and (2) in-plane growth of isolated particle domains (lateral expansion mode). Importantly, the dependence of the optical density on the number of deposition cycles remains linear in both cases. Microscopy results indicate that the origin of the lateral growth is in the interplay of particle/particle and particle/polyelectrolyte interactions rather than in a substrate effect. The lateral expansion mode is a general attribute of the layer-by-layer deposition and can be observed for various aqueous colloids. For the preparation of sophisticated multifunctional assemblies on nanoparticles, the film growth via domain expansion should be avoided, and therefore, one must be able to control the growth pattern. The switch from lateral to normal growth mode can be effected by grafting charged organic groups to YIG nanoparticles. Hydrophobic interactions between the hydrocarbon groups of the modified YIG and polyelectrolyte significantly increase the attractive component of the particle/polyelectrolyte and particle/particle interactions. The films from modified YIG display densely packed nanoparticle layers with a greatly reduced number of defects.

[Experimental studies of the combined effect of styrene and general vibration]. / Eksperimental'nye issledovaniia sochetannogo deistviia stirola i obshchei vibratsii.

People working in modern carpet industry are exposed to a complex of factors of different origin, the most important among which are general vibration and styrene vapors. It has been found out in animal experiments simulating working conditions, that the central nervous system is the most sensitive both under an isolated and joint exposure to the factors. The joint exposure of animals to styrene and vibration may be evaluated as having different targets depending on the parameters under study.