Study on fabrication of calcium sulfate hemihydrate/tricalcium phosphate based injectable bone cement modified by sodium alginate-carboxymethyl chitosan gel network and its resistance to collapse

The collapsibility of bone cement may cause blood vessel embolism, blocking blood flow and causing serious complications such as pulmonary embolism or spinal cord injury, especially when implantation by injection. Therefore, it is of great significance to develop an artificial bone graft with excellent collapse resistance performance. Calcium sulfate and calcium phosphate complex bone cements can be formulated as injectable materials, making them particularly suitable for treating irregular bone defects. However, its clinical application is limited by poor collapsibility resistance and mechanical strength. This study aimed to develop an injectable bone repair material by integrating a biphasic calcium source, which was achieved by calcium sulfate (CS) and calcium phosphate (CP), and a synergistic network formed by sodium alginate (SA) and carboxymethyl chitosan (CMCS). The results showed that the addition of SA-CMCS as a solidifying liquid significantly improved the compressive strength, injectability, and collapsibility resistance of composite bone cement. At the concentration of 1% SA and 15% CMCS, the peak compressive strength reached 11.53 ± 1.3 MPa. All the composite bone cements did not collapse at 5 h in the static environment, and the collapse times of samples SA1-CMCS15 and SA1-CMCS20 in the dynamic environment were 95.3 ± 5.1 min and 96.7 ± 4.9 min, respectively. At CMCS concentrations of 10-20%, the injectability of composite bone cement was higher than 90% and degradation ratio was less than 15%. ALP activity and alizarin red staining confirmed that the composite bone cement showed excellent cytocompatibility and promoted cell proliferation and osteogenic differentiation. This study successfully developed a bone repair material with enhanced mechanical properties, collapsibility resistance, injectability, and biocompatibility, which may make it a promising candidate for bone regeneration applications in clinical.