Novel highly bioactive and biodegradable gypsum/calcium silicate composite bone cements: from physicochemical characteristics to in vivo aspects

Gypsum is a promising material for bone defect repair due to its osteoconductivity, whereas it is still limited in orthopedic and dental surgeries due to its low bioactivity and too rapid resorption so that one major concern is the significant loss in microstructural stability in vivo. In the present strategy some key features were significantly improved by introducing rapidly biodegradable but highly bioactive calcium silicate (CS) for regulating the physicochemical properties and biological performances of the gypsum-based cements at the same liquid/solid ratio. We demonstrated that introduction of 23% CS into β-calcium sulfate hemihydrate (CSH) could improve the physicochemical properties but would not compromise the mechanical strength of the composite. The surface bioactivity was significantly enhanced by introducing 23% CS, and these biphasic composites were favorable for decelerating the biodegradation rate by nearly 18.5% in 28 days in vitro. A mild bioresorption rate, with 39.6% of composite residual 4 weeks after operation, was determined when implanted in subcutaneous tissue of rats. 8 weeks after implantation, the composite cement containing 23% CS significantly enhanced new bone tissue regeneration with a much higher relative bone content (∼68.6%) than pure gypsum in critical size femoral defects in rabbits. The novel CSH–CS biocements represent promising candidates for rapid bone resconstruction and repair in trauma and pathological conditions.