The characteristics of mussel-inspired nHA/OSA injectable hydrogel and repaired bone defect in rabbit

With the rapid development of minimally invasive techniques in orthopedics, minimally invasive surgery combined with injection of bone repair materials has attracted increasing attention for the treatment of bone defects. Inspired by material in mussels, we decorated nanohydroxyapatite (nHA) with dopamine (DA) to form polydopamine (PDA)-decorated nHA (PHA). Then, we introduced PHA into a Schiff base reaction of oxidized sodium alginate (OSA) and gelatin (Gel) to prepare an injectable bone repair hydrogel under mild conditions. Subsequently, the injectability, morphology, mechanical, swelling, and degradation properties of the hydrogel were studied. Then, bone marrow mesenchymal stem cells (BMSCs) were cocultured with the hydrogels to investigate the cytotoxicity, proliferation, and osteogenic differentiation properties of the hydrogel. Finally, the bone repair ability of the OSA-Gel-PHA hydrogels was explored using a 12 weeks rabbit bone defect model. The results of tube inversion and rheological test showed that the hydrogel gelation time was 3-7 min, which will be suitable for clinical operation. The results of SEM, compression tests, rheological tests, swelling and degradation properties tests showed that the addition of PHA changed the microstructure of the hydrogels from porous structure to layered structure, not only improved the compressive strength, toughness, elastic modulus, storage modulus of the hydrogels, but also reduced the swelling properties and degradation rate of the hydrogels, making it more conducive to clinical operations. The results of laser confocal, MTT assay, alkaline phosphatase (ALP) assay and in vivo animal experiments showed that the addition of PHA not only nontoxic, but also promoted the adhesion, proliferation and osteogenic differentiation of BMSCs, as well as the repair and maturation of bone. The application of injectable bone repair materials not only solves the problem of bone defect filling, but also avoids a series of complications caused by open surgery, providing new method for the treatment of bone defects.