Bioactive glass-gelatin hybrids: building scaffolds with enhanced calcium incorporation and controlled porosity for bone regeneration.

Thanks to their active promotion of bone formation, bioactive glasses (BG) offer unique properties for bone regeneration, but their brittleness prevents them from being used in a wide range of applications. Combining BG with polymers into a true hybrid system is therefore an ideal solution to associate toughness from the polymer and stimulation of bone mineralization from the glass. In this work, we report the synthesis and characterization of hybrid scaffolds based on SiO2-CaO bioactive glass and gelatin, a hydrolyzed form of bone type-I collagen. Incorporation of calcium ions, known to trigger bone formation and cellular activity, into the hybrid structure was achieved at ambient temperature through careful control of chemistry of the sol-gel process. Thorough characterization of the materials highlights the effect of grafting an organoalkoxysilane coupling molecule to covalently link networks of BG and gelatin, and proves it a successful means to take control over the degradation and bioactive properties of hybrids. Importantly, BG-gelatin hybrids are synthesized in a process fully conducted at ambient temperature that allows obtaining open-porous scaffolding structures, with well-controlled and tuneable porosity with regards to both pore and interconnection sizes. Mechanical properties of the scaffolds under compression are similar to that of trabecular bone and their apatite-forming ability is even higher than that of pure BG scaffold foams.

Bioactive glass hybrids: a simple route towards the gelatin-SiO2-CaO system.

Bioactive glass hybrids are among the most promising materials for bone regeneration, but the incorporation of calcium, a key element for mineralization properties of the implant, into the inorganic part of the hybrid network is challenging. We present here a synthesis route towards both class I and II gelatin-bioactive glass hybrids allowing the efficient incorporation of calcium ions at low temperature.

Elasticity of an assembly of disordered nanoparticles interacting via either van der Waals-bonded or covalent-bonded coating layers.

Tailoring physical and chemical properties at the nanoscale by assembling nanoparticles currently paves the way for new functional materials. Obtaining the desired macroscopic properties is usually determined by a perfect control of the contact between nanoparticles. Therefore, the physics and chemistry of nanocontacts are one of the central issues for the design of the nanocomposites. Since the birth of atomic force microscopy, crucial advances have been achieved in the quantitative evaluation of van der Waals and Casimir forces in nanostructures and of adhesion between the nanoparticles. We present here an investigation, by a noncontact method, of the elasticity of an assembly of nanoparticles interacting via either van der Waals-bonded or covalent-bonded coating layers. We demonstrate indeed that the ultrafast opto-acoustic technique, based on the generation and detection of hypersound by femtosecond laser pulses, is very sensitive to probe the properties of the nanocontacts. In particular, we observe and evaluate how much the subnanometric molecules present at nanocontacts influence the coherent acoustic phonon propagation along the network of the interconnected silica nanoparticles. Finally, we show that this ultrafast opto-acoustic technique provides quantitative estimates of the rigidity/stiffness of the nanocontacts.