Next Generation Bioactive Glass Derived Scaffold for Bone Tissue Engineering: Synthesis and Characterization

Abstract

Substitution of TiO2 for network modifiers (Na2O and CaO) within a bioactive glass series was investigated to fabricate next generation bioactive glass derived scaffolds with amorphous structure and improved mechanical stability. This study consisted of initial glass characterization and mechanical durability analysis when incubated in simulated body fluid (SBF), and both synthesis and characterization of scaffolds. Three glasses were formulated for this study where a SiO2-CaO-Na2O-P2O5 bioactive glass was used as control denoted BG, 9 wt% substitution of TiO2 for CaO and Na2O were denoted SC-1 and SC-2, respectively. X-ray diffraction revealed partial crystallinity in SC-1 and SC-2 where amorphous pattern was observed for BG. Differential thermal analysis indicated crystallization (devitrification) temperatures were not evident for SC-1 and SC-2. Each glass was incubated in SBF for 1, 10, 100, and 1,000 hours. Scanning electron microscopy images indicated the presence of calcium phosphate deposition layer on BG after 1,000 hours with visible dehydration cracks. However, no visible deposition layer was observed on the surface of SC-1 and SC-2. Ion release profiles of extracted SBF showed decreasing amounts of Ca and P over time, which indicated very thin layer of deposition on the surface of SC-1 and SC-2. Additionally, pH measurement results on the SBF extracts of each glass after incubation study showed evidence of dissolution supported by an increase in pH where BG exhibited highest dissolution rate among three glasses as expected. Although the hardness of SC-1 and SC-2 was found to significantly decrease after each incubation period, SC-1 and SC-2, when incubated for 1,000 hours presented higher mechanical durability than BG. Both BG and SC-1 was synthesized into scaffolds via foam replication technique and heat treated at various temperatures. BG did not form a stable structure for further characterization but X-ray diffraction pattern of SC-1 indicated low crystallinity present when heat treated at below sintering temperature. Optical stereomicroscopy showed transition of powder based material into a predominantly amorphous scaffold over the temperature region of 600~635 °C.