Abstract

Lihong Fan1,2, Yingjie Zhu3. drfan2140@xjtu.edu.cn, 1.Xi’an Jiaotong University; 2.Department of orthopedics, Sanya Central Hospital; 3.Luoyang Orthopedic-Traumatological Hospital
Background: The repair of critical-sized bone defects remains a significant clinical challenge due to the limited availability of autografts and the functional limitations of current synthetic substitutes. While Gelatin Methacryloyl (GelMA) hydrogels offer excellent biocompatibility and injectability, their application is restricted by insufficient mechanical strength and rapid degradation. This study aims to develop a novel composite hydrogel that integrates mechanical reinforcement with controlled drug delivery to enhance bone regeneration.
Methods: We designed an injectable, photocrosslinkable composite hydrogel by incorporating Icariin (ICA)-loaded Mesoporous Silica Nanoparticles (MSNs) into a GelMA matrix. The physicochemical properties, including microstructure, rheology, and degradation, were characterized. The pH-responsive release profile of ICA was evaluated. In vitro, the effects of the hydrogel on rat bone marrow mesenchymal stem cell (rBMSC) proliferation and osteogenic differentiation were assessed via CCK-8, Live/Dead staining, ALP/ARS staining, and RT-qPCR. In vivo bone regeneration potential was evaluated using a rat calvarial defect model, analyzed via micro-CT and histological staining at 6 and 12 weeks.
Results: The incorporation of MSNs increased the compressive modulus of the hydrogel by approximately 1.5-fold (12.3 ± 1.2 kPa) compared to pure GelMA. The composite system exhibited a sustained, pH-responsive release of ICA, with 91.2% cumulative release over 15 days. In vitro experiments demonstrated that the GelMA/MSN/ICA hydrogel significantly promoted rBMSC proliferation and upregulated osteogenic gene expression (ALP, Runx2, Col1). In vivo, micro-CT analysis revealed a significantly higher bone volume fraction (BV/TV) in the composite group at 12 weeks. Histological examination confirmed the formation of mature trabecular bone and enhanced collagen deposition compared to control groups.
Conclusion: The developed GelMA/MSN/ICA composite hydrogel effectively combines mechanical adaptability with the spatiotemporal delivery of osteogenic agents. This multifunctional system provides a favorable microenvironment for stem cell differentiation and significantly accelerates osseointegration, presenting a promising strategy for non-load-bearing bone tissue engineering applications.
Keywords: Bone Tissue Engineering, GelMA Hydrogel, Mesoporous Silica Nanoparticles, Icariin, Osseointegration.