Membranes for Bone Engineering Enriched with Magnesium- and Strontium-Substituted Hydroxyapatite

Hydroxyapatite doped with magnesium and strontium can be a promising strategy for improving bone regeneration. The aims of this study were (1) to synthesize hydroxyapatite (HA) with magnesium (Mg²⁺) and/or strontium (Sr²⁺) substitution and to characterize them; (2) to develop electrospun scaffolds associating HA synthesized with poly-l-lactide (PLLA); and (3) to evaluate the osteoinductive and osteoconductive potential of these scaffolds with ionic changes, associated with human periodontal ligament stem cells (hPDLSC). HA was synthesized with ionic substitution with Mg²⁺, Sr²⁺, or both ions and confirmed by X-ray diffraction analysis. Scanning electron microscopy (SEM) showed HA crystals with nanometric size. Membranes of PLLA and PLLA_HA with conventional or ionic substitution were obtained by electrospinning and evaluated by proliferation (CCK-8), differentiation (alizarin red) and qPCR assays with hPDLSC in osteogenic and clonogenic media. Data were subjected to two-way and one-way ANOVA with Tukey's test, and Kruskal-Wallis with Student-Newman-Keuls test (α=0.05). The ionic substitutions of HA did not influence adhesion and proliferation at 3 or 7 days. However, in clonogenic medium scaffold containing ionic substitutions presented greater extracellular mineralization than the control PLLA. Furthermore, scaffolds with HA and magnesium presented higher expression of osteopontin. In the osteogenic medium, only the material with HA conventional or with both ions changes presented greater OPN expression than the control material and greater extracellular matrix mineralization. It can be concluded that membranes containing HA_Mg_Sr have higher osteogenic properties even in clonogenic conditions, improving hPDLSC differentiation and becoming a promising alternative for bone regeneration applications.