Chapter 5:Sol–Gel Glass and Nano–Macro Porous Bioscaffolds

To facilitate hard tissue regeneration there is a pressing need to develop biocompatible, macroporous (pore size ∼100's of µm) scaffolds that are tailored ideally to suit individual patient needs. A critical requirement of this goal is that the scaffolds degrade in the body at a rate that is comparable to that of the tissue re-growth. Among various potential materials, calcium silicate glasses are the most promising model bioactive candidates that also stimulate bone formation, but they degrade too slowly. A successful strategy to accelerate degradation is to increase the specific surface area by superimposing nanoporosity (≈ 10 nm) on macroporosity. In such a bioscaffold, nano- and macroporosities are optimized to meet the needs of a specific patient, so the desired product is a tailored amorphous multi-porous (TAMP) silicate structure. As an added benefit, nanoporosity allows improved diffusion of nutrients and waste products in and out of the scaffolds, further improving its biocompatibility. Here we present an overview of its fabrication process, biological performance and future prospects for use in patients. The TAMP bioscaffolds are fabricated by a modified sol–gel process, which is based on spinodal phase separation induced by a water-soluble polymer. Under quasi-dynamic conditions the model 30CaO–70SiO2 composition degrades in simulated body fluid within weeks depending on nanoporosity. Additionally, in vitro cell tests indicate that nanoscale topology significantly affects the biological performance of TAMP scaffolds. In vivo tests in animals demonstrate superior regeneration of hard, as well as soft, tissue depending on TAMP implant site, and preliminary results of a clinical trial provide a promising outlook for this class of bioscaffold.