Physicochemical and biological properties of carboxymethyl chitosan zinc (CMCS-Zn)/α‑calcium sulfate hemihydrate (α-CSH) composites

To improve the osteoinductivity, antibacterial activity, and clinical application of calcium sulfate hemihydrate (CSH), carboxymethyl chitosan zinc (CMCS-Zn) and α-CSH were prepared using different mass ratios. The setting time and injectability of the CMCS-Zn/α-CSH composite were increased with increasing CMCS-Zn content. After adding different amounts of CMCS-Zn to α-CSH, the fine lamellar structure of CMCS-Zn was found by scanning electron microscopy (SEM), which is evenly distributed in the matrix of α-CSH. With the increase of CMCS-Zn, the pores on the surface gradually increased. After mixing CMCS-Zn and α-CSH, no new phase was measured by X-ray diffraction (XRD) and Fourier transform (FTIR) spectroscopy. The degradation rate of CMCS-Zn/α-CSH decreased with increasing CMCS-Zn content, and the pH was stable during the degradation process. The release of Zn²⁺ increased with increasing CMCS-Zn content, while the release of Ca²⁺ decreased. Extracts of CMCS-Zn/α-CSH composites up-regulated the osteoinduction and migration of rat bone marrow stem cells. The antibacterial ability of CMCS-Zn/α-CSH was evaluated as a function of CMCS-Zn content. In the rat bone defect model, 5% CMCS-Zn/α-CSH group revealed a higher volume and density of trabeculae by micro-CT 8 weeks after the operation. Therefore, CMCS-Zn/α-CSH was demonstrated to be an adjustable, degradable, substitute biomaterial (with osteogenesis-promoting effects) for use in bone defects, which also has antibacterial activity that can suppress bone infection.