Bioactive glass nanoparticles obtained through sol-gel chemistry.

Different sol-gel strategies based on the Stöber method are proposed enabling preparation of nanoparticles of SiO2-CaO bioactive glass with different size, narrow size distribution and good dispersion capability. Eu(3+)-doped glass nanoparticles with luminescent properties can also be obtained.

Influence of glass scaffolds macroporosity on the bioactive process.

Little is known about the ideal morphology for three-dimensional (3D) porous scaffolds to be used in bone tissue engineering. The present study will supply useful data about the dependence of the mineralization process upon macroporous features of bioactive glass scaffolds. It also points out the difficulty in distinguishing between the bioactive properties of scaffolds if using common characterization techniques often considered as standard techniques to assess in vitro bioactivity. Here, two bioactive glass foams with different porosities (porous diameters and interconnection sizes) were successfully synthesized by varying the surfactant quantity in the sol-gel foaming process. The two foams had porosities apparently sufficient to serve as a bone tissue engineering scaffold and exhibited no significant difference when studied for the releasing or the taking up of ionic species when immersed in simulated body fluid (SBF). However, thanks to microion beam analysis, it was possible to highlight key differences in the mineralization reaction taking place at the surface of the pores. It is clearly evident that the homogeneity of reaction inside the 3D-scaffolds is particularly dependent upon porosity. In particular, it is demonstrated that inadequate porous features can result in limited circulation of the fluid inside the pores. Careful attention must be paid to the pore size distribution and interconnection sizes when designing scaffolds for bone tissue engineering, in order to induce homogeneous mineralization inside the porous material and for the scaffold to be efficiently alimented with nutrients or growth factors while allowing a free circulation of the bone cells.

Green and safe in situ templating of bioactive glass scaffolds for bone tissue engineering.

This communication reports a new process for the synthesis of bioactive glass foams. This process is based on the use of gelatin as a template during the foaming of a sol, and the gelled gelatin template formed in situ maintains the foam structure during further condensation of the glass network.

87Sr solid-state NMR as a structurally sensitive tool for the investigation of materials: antiosteoporotic pharmaceuticals and bioactive glasses.

Strontium is an element of fundamental importance in biomedical science. Indeed, it has been demonstrated that Sr(2+) ions can promote bone growth and inhibit bone resorption. Thus, the oral administration of Sr-containing medications has been used clinically to prevent osteoporosis, and Sr-containing biomaterials have been developed for implant and tissue engineering applications. The bioavailability of strontium metal cations in the body and their kinetics of release from materials will depend on their local environment. It is thus crucial to be able to characterize, in detail, strontium environments in disordered phases such as bioactive glasses, to understand their structure and rationalize their properties. In this paper, we demonstrate that (87)Sr NMR spectroscopy can serve as a valuable tool of investigation. First, the implementation of high-sensitivity (87)Sr solid-state NMR experiments is presented using (87)Sr-labeled strontium malonate (with DFS (double field sweep), QCPMG (quadrupolar Carr-Purcell-Meiboom-Gill), and WURST (wideband, uniform rate, and smooth truncation) excitation). Then, it is shown that GIPAW DFT (gauge including projector augmented wave density functional theory) calculations can accurately compute (87)Sr NMR parameters. Last and most importantly, (87)Sr NMR is used for the study of a (Ca,Sr)-silicate bioactive glass of limited Sr content (only ~9 wt %). The spectrum is interpreted using structural models of the glass, which are generated through molecular dynamics (MD) simulations and relaxed by DFT, before performing GIPAW calculations of (87)Sr NMR parameters. Finally, changes in the (87)Sr NMR spectrum after immersion of the glass in simulated body fluid (SBF) are reported and discussed.