Abstract: Glutaraldehyde (GA), the most widely used crosslinking agent for biomaterials, is cytotoxic. CaCl2 is of particular interest due to its non-toxic nature. Rhein can chelate Ca2+ and promote bone growth. Here we reported a novel nano calcium-deficient hydroxyapatite/O-carboxymethyl chitosan-CaCl2 microspheres loaded with rhein (RH-nCDHA/OCMC-CaCl2 microspheres) using CaCl2 as crosslinking agent for bone defect repair. The obtained microspheres were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TG) and Fourier transform infrared spectroscopy (FT-IR). The surface of the obtained microspheres is rough with quite a few voids. The nano calcium-deficient hydroxyapatite (nCDHA) accounts for about 70% of the total weight of the microspheres, which is equivalent to the proportion of inorganic substances in human bones. A high encapsulation efficiency (EE) and loading capacity (LC) of the microspheres loaded with rhein was 90.20?±?0.60% and 11.03?±?0.30%, respectively. For microspheres using CaCl2 in simulated body fluid (SBF) after 14 days, the drug released continuously and bone-like apatite formed like layer. The cells on the surface of the RH-nCDHA/OCMC-CaCl2 microspheres grew better comparing with nCDHA/OCMC-GA microspheres and the skull defects of rats after landfill can be almost repaired after 8 weeks, which revealed the potential of the microspheres for bone repair.

Key words: Nano calcium-defcient hydroxyapatite , · O-carboxymethyl chitosan , · Rhein , · Microspheres , · Bone repair