Synthesis, Processing and the Effect of Thermal Treatment on the Solubility, Antioxidant Potential and Cytocompatibility of Y2O3 and CeO2 doped SiO2-SrO-Na2O Glass-Ceramics

Thermal treatment of a 0.52SiO₂-0.24SrO-0.24-xNa₂O-xMO glass-ceramic series (where x = 0.08 and MO = Y₂O₃ or CeO₂) was conducted in order to synthesize yttrium (Y³⁺) and cerium (Ce³⁺) crystalline species that may act as radical oxygen specie (ROS) scavengers. The prominent phase for the Control is a sodium-strontium-silicate while the experimental glass-ceramics (HY, YCe, and HCe) present sodium-Y/Ce-silicate and oxide phases. Disk shrinkage during thermal processing ranges from 1-7% for Control, HY, YCe, and HCe in both diameter and thickness. Solubility studies determined that the release of Si⁴⁺ and Na⁺ are greatest from the Control disks which peaks at 1550 µg/mL. Release from the Y³⁺ and Ce³⁺ glass-ceramics reached 320 µg/mL for Si⁴⁺ and 630 µg/mL for Na⁺. The range of antioxidant capacity (ABTS assay) for all samples was 0.31-3.9 mMTE. No significant reduction in MC 3T3 Osteoblast cell viability was observed for any composition tested.

Bioactivity of Y2O3 and CeO2 doped SiO2-SrO-Na2O glass-ceramics

The bioactivity of yttrium and cerium are investigated when substituted for Sodium (Na) in a 0.52SiO2-0.24SrO-0.24 -xNa2O- xMO glass-ceramics (where x = 0.08 and MO = Y2O3 or CeO2). Bioactivity is monitored through pH and inductively coupled plasma-optical emission spectrometry where pH of simulated body fluid ranged from 7.5 to 7.6 and increased between 8.2 and 10.0 after 14-day incubation with the glass-ceramic disks. Calcium (Ca) and phosphorus (P) levels in simulated body fluid after incubation with yttrium and cerium containing disks show a continual decline over the 14-day period. In contrast, Con disks (not containing yttrium or cerium) caused the elimination of Ca in solution after 1 day and throughout the incubation period, and initially showed a decline in P levels followed by an increase at 14 days. Scanning electron microscopy and energy dispersive spectroscopy confirmed the presence of Ca and P on the surface of the simulated body fluid-incubated disks and showed precipitates on Con and HCe (8 mol% cerium) samples. Cell viability of MC3T3 osteoblasts was not significantly affected at a 9% extract concentration. Optical microscopy after 24 h cell incubation with disks showed that Con samples do not support osteoblast or Schwann cell growth, while all yttrium and cerium containing disks have direct contact with osteoblasts spread across the wells. Schwann cells attached in all wells, but only showed spreading with the HY-S (8 mol% yttrium, heated to sintering temperature) and YCe (4 mol% yttrium and cerium) disks. Scanning electron microscopy of the compatible disks shows osteoblast and sNF96.2 Schwann cells attachment and spreading directly on the disk surfaces.