ortho-Phenyl dialkylphosphonium sulfonate compounds: two rotamers in equilibrium.

Two known and two new ortho-phenyl phosphonium-sulfonate compounds have been synthesized and analyzed in solution and in the solid state. When the phosphonium moiety bears alkyl substituents, two rotamers are in equilibrium in solution. These two rotamers have been entirely characterized and are shown to differ by the spatial arrangement of the phosphonium proton relative to the sulfonate moiety. The phosphonium proton chemical shift and the 1JPH coupling constant are characteristic values for each rotamer. The kinetic and thermodynamic constants have been determined by means of NMR and DFT studies.

New perspectives in hydrogen storage based on RCH2NH2/RCN couples.

A recent breakthrough in primary amine dehydrogenation by an oxidant-free process, and without any hydrogen acceptor, opens the possibility for RCH2NH2/RCN couples to be considered as potential hydrogen energy carriers. Both hydrogenation and dehydrogenation processes can be catalysed by ruthenium complexes under rather mild conditions. This emerging exciting approach could be the starting point for the development of valuable economical systems.

Pectin-based injectable biomaterials for bone tissue engineering.

A variety of natural polymers and proteins are considered to be 3D cell culture structures able to mimic the extracellular matrix (ECM) to promote bone tissue regeneration. Pectin, a natural polysaccharide extracted from the plant cell walls and having a chemical structure similar to alginate, provides interesting properties as artificial ECM. In this work, for the first time, pectin, modified with an RGD-containing oligopeptide or not, is used as an ECM alternative to immobilize cells for bone tissue regeneration. The viability, metabolic activity, morphology, and osteogenic differentiation of immobilized MC3T3-E1 preosteoblats demonstrate the potential of this polysaccharide to keep immobilized cells viable and differentiating. Preosteoblasts immobilized in both types of pectin microspheres maintained a constant viability up to 29 days and were able to differentiate. The grafting of the RGD peptide on pectin backbone induced improved cell adhesion and proliferation within the microspheres. Furthermore, not only did cells grow inside but also they were able to spread out from the microspheres and to organize themselves in 3D structures producing a mineralized extracellular matrix. These promising results suggest that pectin can be proposed as an injectable cell vehicle for bone tissue regeneration.

Cell-to-cell communication between osteogenic and endothelial lineages: implications for tissue engineering.

There have been extensive research efforts to develop new strategies for bone tissue engineering. These have mainly focused on vascularization during the development and repair of bone. It has been hypothesized that pre-seeding a scaffold with endothelial cells could improve angiogenesis and bone regeneration through a complex dialogue between endothelial cells and bone-forming cells. Here, we focus on the paracrine signals secreted by both cell types and the effects they elicit. We discuss the other modes of cell-to-cell communication that could explain their cell coupling and reciprocal interactions. Endothelial cell-derived tube formation in a scaffold and the dialogue between endothelial cells and mesenchymal stem cells provide promising means of generating vascular bone tissue-engineered constructs.