Immunomodulatory and pro-mineralizing effects of an injectable baicalein-loaded methacrylated gelatin hydrogel for vital pulp therapy

This study first investigated the biological function of baicalein (BA) and then developed a photocrosslinkable methacrylated gelatin (GelMA) hydrogel incorporating BA-loaded, carboxylated mesoporous silica nanospheres (MSNs-COOH-BA) for vital pulp therapy. Initially, BA (1-20 μM) was tested for cytocompatibility, in vitro mineralized nodule formation as an early indicator of odontogenic potential, and antioxidant/anti-inflammatory functionality on dental pulp stem cells (DPSCs) and macrophages. Then, 15% (w/v) GelMA was formulated with MSNs-COOH-BA (10 or 20 mg/mL). Hydrogels were characterized by SEM/EDS for their microstructure morphology and chemical composition, as well as for compression, swelling, degradation, and BA release. Biological assessments included DPSC cytocompatibility and early mineralization responses under or without LPS stimulation, macrophage cytokine modulation, and in vivo subcutaneous biocompatibility in rats. Statistical analysis used ANOVA/post-hoc tests (α = 5%). BA was non-cytotoxic (≥70% viability at 24 h), enhanced mineralized nodule formation under both basal and inflammatory conditions, reduced intracellular ROS levels, and suppressed TNF-α, IL-1α, and IL-6 production in a dose-responsive manner. GelMA maintained its porous architecture after MSN incorporation. Although BA-functionalized MSNs showed some nanosphere clustering, they reinforced mechanical performance, with MSNs-COOH-BA (20 mg/mL) increasing Young's modulus and ultimate compressive strength relative to GelMA and outperforming MSNs without BA. MSNs-containing hydrogels displayed moderated swelling and slower enzymatic mass loss versus GelMA alone. BA was released over 10 days, and eluates remained non-cytotoxic (<30% reduction vs control). Under LPS challenge, 20 mg/mL MSNs-COOH-BA induced the highest 21-day mineralized nodule formation in DPSCs, and hydrogel extracts reduced macrophage synthesis of TNF-α and IL-1α. In vivo, all groups exhibited an acute infiltrate at 7 days, which significantly declined by 28 days, with no differences observed among formulations at either time point. The GelMA/MSNs-COOH-BA hydrogel paired sustained BA delivery with mechanical integrity, cytocompatibility, anti-inflammatory activity, and early pro-odontogenic cellular responses, supporting its promise as an injectable biomaterial with clinically relevant therapeutic properties for preserving pulp vitality while supporting the dentin-pulp complex's intrinsic repair and development abilities.