Effect of milling media on processing and performance of 13-93 bioactive glass scaffolds fabricated by robocasting

Three dimensional scaffolds with controlled pore architecture were prepared from 13-93 bioactive glass powder by robocasting (direct-writing), using carboxymethyl cellulose (CMC) as a single, multifunctional additive. The influence of powder milling environment (water or ethanol) on sintering, mechanical and biological performance and in vitro degradation behavior of the fabricated scaffolds was investigated. Despite the incorporation of carbonaceous species to the glass upon milling in ethanol, all fabricated structures exhibited good bioactivity and cell affinity and their strength values were close to those of cortical bone. Water milled powders produced poorer inks and some residual microporosity in the scaffold rods even at the optimum sintering temperature. This microporosity plays a major role in controlling the in vitro degradation and mechanical performance of 13-93, enhancing its degradation rate and maximum conversion factor to HA — from below 6%, for dense structures to ~35% for microporous scaffolds — by hampering the formation of a passivating layer.