IN VIVO EVALUATION OF SCAFFOLDS WITH A GRID-LIKE MICROSTRUCTURE COMPOSED OF A MIXTURE OF SILICATE (13-93) AND BORATE (13-93B3) BIOACTIVE GLASSES

A borate bioactive glass (designated 13-93B3) converts faster to hydroxyapatite (HA) than silicate 13-93 bioactive glass but recent studies have shown conflicting results for its capacity to repair rat calvarial defects. In this study, scaffolds composed of 13-93 and 13-93B3 glass alone and composite scaffolds composed of a mixture of 13-93 and 13-93B3 glasses were created with the same grid-like microstructure (porosity = 47%; filament diameter = 330 mu m; pore width = 300 mu m) using a robocasting technique. When implanted in rat calvarial defects in vivo, the scaffolds showed a decreasing capacity to regenerate bone with increasing volume fraction of 13-93B3 glass in the scaffolds. The percent new bone in the defects implanted with the 13-93 scaffolds (23 +/- 4 % at 6 weeks and 28 +/- 8% at 12 weeks) was significantly higher than in the defects implanted with the 13-93B3 scaffolds (6 +/- 4 % at 6 weeks and 9 +/- 7 % at 12 weeks). While the 13-93 glass was only partially converted to HA after 12 weeks in vivo, the 13-93B3 glass was almost fully converted within 6 weeks. Composite scaffolds composed of an optimized mixture of silicate 13-93 and borate 13-93B3 bioactive glasses may provide advantages for bone and tissue healing over scaffolds composed of 13-93 or 13-93B3 glass alone.