Injectable hydrogels based on gellan gum promotes in situ mineralization and potential osteogenesis

Bone defects are usually caused by trauma, infection, tumor resection or congenital diseases, and they attract many researchers’ attention to fabricate biomaterials to promote bone regeneration. In this report, we prepared double-network hydrogel by one-step mixing method, in which anion polysaccharide gellan gum (GG) was used as the first network and polymerizable monomer in the presence of crosslinking agent was acted as the second network. Among then, a synthesized monomer named as 2-methacrylamidoethyl dihydrogen phosphate (MDP) with phosphate group was introduced in the second network to promote in situ mineralization. The addition of the second network can significantly increase the mechanical properties of the hydrogel, including both the compressive modulus and ultimate stress of hydrogels increase compared to uncrosslinked groups. To certify the potential application of double-network hydrogel to act as scaffold in bone regeneration, the double-network hydrogels was incubated in simulated body fluid (SBF) for 2 weeks to explore the in situ mineralization capacity of hydrogels. The hydroxyapatite can be observed on the surface of hydrogels, as confirmed by the scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) test and X-ray diffraction test (XRD). In addition, the results of thermal gravimetric analysis (TGA) and colorimetric test indicate that as the concentration of monomer MDP increased, both the quantity and the rate of the generation of hydroxyapatite on the surface of hydrogels increased. The cytotoxicity of hydrogels was also tested by preosteoblast MC3T3-E1 cell line. Therefore, the double-network hydrogels can act as a potential scaffold material in bone regeneration.