Synthesis of rare earth substituted biphasic calcium phosphate

Full text: Biphasic calcium phosphate (BCP) was first used to described a calcium phosphate ceramic consisting of hydroxyapatite (HAp) and Β-tricalcium phosphate (Β-TCP) mixture. It was initially used to repair periodontal bone defect and currently. Commercial bone substitute materials, BCP was also found to be more efficient bone repair material than Hap. Rare earth elements have little toxicity, and they have anti-blood coagulation effect. The character of the bone substitute material can be changed by substitution of the rare earth element. Because of anti-blood coagulation effect of the rare-earth elements, the rare earth substituted BCP product can be expected to be a new functional biomaterial. Rare earth element such as samarium (Sm) is presently used for the palliation of bone metastases. A beta emitter Sm-153 radioisotope attached to an organic chemical chelating agent is used for this therapy. The potential of using a Sm substituted BCP will eventually result in a higher specificity of targeted bone material as well as lower toxicity and radiation doses to the surrounding tissues. A new synthesis route for the rare earth substituted BCP was developed by using a popular rare earth extracting medium, diethyl hexyl phosphoric acid (DEHPA) as the source for phosphate. The process of attaching the Sm to DEHPA was carried out in normal solvent extraction technique. Synthesis of the Sm substituted BCP was carried out by using a hydrothermal process involving the use of Sm-DEHPA and calcium carbonate. White crystalline powder was formed upon calcination of the precipitate at 600 degree C and this can be pressed into pellets. The product morphology as characterized by SEM shows that it consist of agglomerates of crystalline plates with mean particle size 8-20 μm depending on the parameters used during synthesis. The difractogram shows a highly crystalline product with the presence of both Hap and ΒTCP phases. Quantitative analysis on these phases gives a result of 58% ΒTCP and 42% Hap, which similar to that of the commercial BCP product. (Author)