Sonochemical synthesis of calcium phosphate powders.

beta-tricalcium phosphate (beta-TCP) and biphasic calcium phosphate powders (BCP), consisting of hydroxyapatite (HA) and beta-TCP, were synthesized by thermal decomposition of precursor powders obtained from neutralization method. The precursor powders with a Ca/P molar ratio of 1.5 were prepared by adding an orthophosphoric acid (H(3)PO(4)) solution to an aqueous suspension containing calcium hydroxide (Ca(OH)(2)). Mixing was carried out by vigorous stirring and under sonochemical irradiation at 50 kHz, respectively. Glycerol and D-glucose were added to evaluate their influence on the precipitation of the resulting calcium phosphate powders. After calcination at 1000 degrees C for 3 h BCP nanopowders of various HA/beta-TCP ratio were obtained.

The interation of blood proteins with alpha-alumina

The use of alumina (Ó-Al2O3) as a material for cardiovascular applications was investigated on the basis of protein adsorption and thrombus formation on the material. The adsorption of 125I-labelled albumin and fibrinogen from phosphate buffered saline (pH 7.35, 0.100 M NaCl, 8.66 mM KH2PO4 and 41 mM Na2HPO4) solution on ceramic discs of alumina was studied. Both albumin and fibrinogen presented affinity for ceramic surfaces, with adsorptions of 1.47 + or - 0.6 ng/cm2 and 0.198 + or - 0.01 ng/cm2, respectively. Scanning electron micrographs of the Ó-Al2O3 surfaces after contact of the discs with whole human blood showed a thrombogenic behavior of alumina alpha. These results indicate a hemoincompatible property. Although critical surface tension (YC: 21.8 dynes/cm) of the disc surfaces determined by contact angle technique of sessile drops indicates that alumina alpha is a biocompatible material, by this criterion, the data reported here indicate that Ó-Al2O3 cannot be used for cardiovascular applications