Enhanced Osteogenesis of Abalone Shell–Derived Hydroxyapatite via Strontium Substitution and Hyaluronic Acid Incorporation in MC3T3-E1 Osteoblasts

Alveolar ridge resorption after tooth extraction is an inevitable physiologic process and can compromise implant site development; therefore, ridge preservation requires bioactive grafts that support early osteoblast colonization and osteogenic signaling. This study evaluated an abalone shell–derived bone graft formulated as carbonated hydroxyapatite (ABG), modified by Sr²⁺ substitution (ABGSr) and supplemented with hyaluronic acid at two ratios (1:1 and 3:4, w/w) to enhance material characteristics, biocompatibility, and osteogenic-related gene expression in MC3T3-E1 osteoblasts. Material characterization included FTIR, SEM, and EDX. FTIR confirmed apatite functional groups (phosphate ~1046 cm⁻¹, hydroxyl ~3572 cm⁻¹, and carbonate bands), supporting successful carbonated hydroxyapatite formation, while SEM showed ABGSr surfaces became rougher and less dense than ABG, suggesting a more cell-favorable topography.

Biocompatibility was assessed by CCK-8 at 24–72 h and compared with a commercial xenograft control (KX) and negative control. ABGSrHA3 (3:4) produced significantly higher optical density than the control at 24, 48, and 72 h, indicating superior proliferation, whereas ABGSrHA1 (1:1) did not exceed the control at 48–72 h. RT-PCR demonstrated significant group-, time-, and interaction-effects for BMP-2, OPN, and OCN. BMP-2 expression peaked early (day 5) with the highest levels in ABGSrHA3, OPN peaked at day 3 with the highest expression in KX, and OCN peaked at day 7 with the highest expression in ABGSrHA1.

Overall, Sr²⁺ substitution combined with HA supplementation—particularly the 3:4 formulation—most consistently enhanced early osteoblast proliferation and osteogenic signaling, supporting its potential as a locally sourced ridge preservation biomaterial.