In this study, a biphasic injectable bone substitute, based on tricalcium silicate (Ca(3)SiO(5)) and plaster (CaSO(4).1/2H(2)O), is presented. The addition of CaSO(4).1/2H(2)O could accelerate the hydration of Ca(3)SiO(5), decrease the setting time, and improve the strength of the cement. The workable Ca(3)SiO(5)/CaSO(4).1/2H(2)O pastes with a liquid to powder (L/P) ratio of 0.8-1.0 mL g(-1) could be injected for 2-20 min (nozzle diameter 2.0 mm) and enabled initial setting times of 9-60 min. The setting process yielded cellular structures with compressive strength of 12.4-31.5 MPa after 2-28 days. The in vitro bioactivity of the paste was investigated by soaking in simulated body fluid (SBF) for 7 days. The result showed that although large amount of CaSO(4).1/2H(2)O (30%) was added, the paste showed good ability to induce the formation of hydroxyapatite (HA). Furthermore, the Ca(3)SiO(5)/CaSO(4).1/2H(2)O paste could degrade in Ringer's solution, and the dissolution extracts of the paste also had a stimulatory effect on L929 cell growth in certain concentration range. Our results indicated that Ca(3)SiO(5)/CaSO(4).1/2H(2)O paste was bioactive and degradable, and showed excellent mechanical properties after self-setting. Therefore, it may be a potential candidate for further investigation as injectable tissue repairing substitute.
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