A novel hybrid nanofibrous strategy to target progenitor cells for cost-effective in situ angiogenesis.

Although the impact of composites based on Ti-doped calcium phosphate glasses is low compared with that of bioglass, they have been already shown to possess great potential for bone tissue engineering. Composites made of polylactic acid (PLA) and a microparticle glass of 5TiO2-44.5CaO-44.5P2O5-6Na2O (G5) molar ratio have already demonstrated in situ osteo- and angiogenesis-triggering abilities. As many of the hybrid materials currently developed usually promote osteogenesis but still lack the ability to induce vascularization, a G5/PLA combination is a cost-effective option for obtaining new instructive scaffolds. In this study, nanostructured PLA-ORMOGLASS (organically modified glass) fibers were produced by electrospinning, in order to fabricate extra-cellular matrix (ECM)-like substrates that simultaneously promote bone formation and vascularization. Physical-chemical and surface characterization and tensile tests demonstrated that the obtained scaffolds exhibited homogeneous morphology, higher hydrophilicity and enhanced mechanical properties than pure PLA. In vitro assays with rat mesenchymal stem cells (rMSCs) and rat endothelial progenitor cells (rEPCs) also showed that rMSCs attached and proliferated on the materials influenced by the calcium content in the environment. In vivo assays showed that hybrid composite PLA-ORMOGLASS fibers were able to promote the formation of blood vessels. Thus, these novel fibers are a valid option for the design of functional materials for tissue engineering applications.

Towards 4th generation biomaterials: a covalent hybrid polymer-ormoglass architecture.

Hybrid materials are being extensively investigated with the aim of mimicking the ECM microenvironment to develop effective solutions for bone tissue engineering. However, the common drawbacks of a hybrid material are the lack of interactions between the scaffold's constituents and the masking of its bioactive phase. Conventional hybrids often degrade in a non-homogeneous manner and the biological response is far from optimal. We have developed a novel material with strong interactions between constituents. The bioactive phase is directly exposed on its surface mimicking the structure of the ECM of bone. Here, polylactic acid electrospun fibers have been successfully and reproducibly coated with a bioactive organically modified glass (ormoglass, Si-Ca-P2 system) covalently. In comparison with the pure polymeric mats, the fibers obtained showed improved hydrophilicity and mechanical properties, bioactive ion release, exhibited a nanoroughness and enabled good cell adhesion and spreading after just one day of culture (rMSCs and rEPCs). The fibers were coated with different ormoglass compositions to tailor their surface properties (roughness, stiffness, and morphology) by modifying the experimental parameters. Knowing that cells modulate their behavior according to the exposed physical and chemical signals, the development of this instructive material is a valuable advance in the design of functional regenerative biomaterials.

Urinary glycolipids of YC8 lymphoma bearing mice: effectors of glycosylation process.

Glycolipids from YC8 lymphoma bearing mice urines have peen obtained by the method of Folch and fractionated on silicic column and on silica gel plates. One fraction, among the five obtained, may be used by sera galactosyltransferase as an acceptor for galactose, to form a new glycolipid compound. Furthermore this fraction has shown an inhibitory effect on phosphatase activity, in agreement with hypothesis which relates relates glycosyltransferase and phosphatase activities during tumorous process.

[Demonstration of N-acetylgalactosaminyltransferase activity in the murine lymphoma YC8]. / Mise en évidence d'une activité N-acétyl-galactosaminyltransférase au cours du lymphome murin YC8.

The N-acetyl-galactosaminyltransferase activity has been studied in the biological fluids of YC8-lymphoma bearing Balb/c mice. It is enhanced during tumor development from 1 to 30 times in peritoneal fluids and from 1 to 10 times in sera. This activity is nil in urines. Optimal requirements for activity have been determined. Results suggest the existence, during tumor process not only of an enhancement of enzymatic activity, but also of a new molecule synthesis, molecules which are endogenous acceptors for the enzyme.

Galactose transfer and UDP-galactose hydrolysis in urine from normal Balb/c and Balb/c YC8 mice.

By chromatographic method we have shown the existence of a complex system for galactose transfer from UDP-galactose and for nucleotide hydrolysis in urines from Balb/c YC8 and normal Balb/c mice. By action of sera from normal and ascitic mice as source of enzyme, we have been able to detect transfer for galactose in urines from ascitic mice and an important inhibitory effect of the nucleotide sugar hydrolysis by the sera with urines from normal mice.