Synthesis and characterization of injectable bone cement prepared from biphasic calcium phosphate extracted from lamb and bovine bones

Abstract

Dicalcium phosphate (DCP) cements such as dicalcium phosphate dihydrate (DCPD) also known as brushite and dicalcium phosphate anhydrous (DCPA) also known as monetite have received considerable attention of researchers due to their potential applications in dental, maxillofacial and orthopaedic surgery. Quick setting and poor injectability due to liquid–solid phase separation limit the clinical use of brushite and monetite cements. The presence of certain ions (Mg, Zn, Na, Sr, Co, Ag etc.) in the cement during the setting process can influence setting time and the properties of the cement. In this study we report preparation of injectable dicalcium phosphate (DCP) bone cement using biphasic calcium phosphate (BCP) extracted from lamb and bovine femur bones. BCP was extracted by calcinating the defatted lamb and bovine bones at 1450 °C. BCP was extracted from three batches each for lamb and bovine bones. EDX analysis showed the presence of Mg and Na ions as trace elements in extracted BCPs. X-ray diffraction pattern of the prepared cement showed the formation of brushite along with monetite as minor phase along with a small quantity of hydroxyapatite. Monetite phase diminished gradually with the decrease in powder to liquid ratio (PLR). The values of initial and final setting times were observed to be well within the preferable range 3-8 minutes, for initial and less than 15 minutes for final setting time, as recommended for orthopedic applications. Exceptional injectability (>90 %) was achieved for almost all the PLR formulations used for preparation of DCP cement. A decrease in the compressive strength was observed with increasing liquid phase in the cement, which was attributed to the resulting higher degree of porosity in the set cement. Moreover, for the DCP cement prepared from three different batches of BCP extracted from bovine and lamb bones, there were no noticeable variations in the setting time, injectability or compressive strength. Apatite layer formation on the cement surface was studied by immersing cement samples in simulated body fluid (SBF) for up to 7 days. A formation of apatite layer and an increase in the compressive strength from 2.71 ± 0.22 to 9.68 ± 0.36 MPa were observed. These results indicate that bone cement prepared from BCP extracted from lamb and bovine femur bones can be considered for orthopaedic applications as a potential bone substitute for regeneration and repairing of bone defects.