Haemolytic potential of hydroxyapatite and β-tricalcium phosphate bioceramic powders

Hydroxyapatite and β-tricalcium phosphate powders have been synthesized by wet chemical methods starting from calcium nitrate and ammonium hydrogen phosphate. The powders were characterized with an X-ray diffraction method and scanning electron microscopy. On treatment in the temperature range 100 to 1150°C, it was found that both powers were single phase with stoichiometric composition. In the case of HAP, high haemolysis was observed when the precipitated powder was not thoroughly washed. A direct correlation between the number of washings and the percentage haemolysis could be established. It was observed that in the case of as precipitated and 450°C heated condition, the β-TCP was highly haemolytic. As impurities are normally removed at 450°C, the haemolysis could possibly be due to physical disruption of red blood cells by the sharp needle-like morphology of β-TCP crystals. In order to test this hypothesis, the powder was heated to 1150°C to blunt the sharp edges. The treatment reduced the haemolysis from 54 % to 3%