Glycogen as a Cross-Linking Agent of Collagen and Nanohydroxyapatite To Form Hydrogels for bMSC Differentiation

Polysaccharides have been considered as an important linker of organics and minerals in the scaffold for bone repair. In this study, we exploited glycogen as the contactor of collagen and hydroxyapatite to form composite hydrogels since it could provide stereoscopic multiple sites for reaction with other components. Glycogen was modified with guanido followed by oxidization to aldehyde, which subsequently combined with collagen and hydroxyapatite through a Schiff base bond and electrostatic interaction, respectively. The resulting hydrogels could almost maintain their prototypes within 2 weeks, with little degradation. Their Young’s modulus (10–70 kPa) and compressive modulus (30–432 kPa) were all within the range of properties required for stem cells to differentiate into osteoblasts or cartilage. Additionally, bone mesenchymal stem cells cultured on the composite hydrogels presented desirable cell adhesion, viability, and growth. The ratio of collagen/glycogen/hydroxyapatite (HAP) components could regulate bone mesenchymal stem cell differentiation into osteoblasts or chondrocytes, which was confirmed by alkaline phosphatase (ALP) activity and related gene expression assays. The results demonstrated that glycogen could be a promising coupling agent for bone scaffold and the collagen/glycogen/nano-HAP (C/G/H) composite hydrogels would be a potential scaffold for bone tissue engineering.