The present paper demonstrated a biomimetic method to coat calcium phosphate (Ca-P) on the surface of titanium induced by NaOH-treatment from a simple supersaturated hydroxyapatite solution (SHS). The in#uence of pH value and calcium ions concentration on the precipitation process was investigated. It is necessary for the solution to be supersaturated than the critical concentration of octacalcium phosphate (OCP) to get Ca-P coatings on titanium surface. In the precipitating process, it seems that amorphous calcium phosphate (ACP) precipitated first, then OCP, and finally hydroxyapatite (HA). The system was in continuous evolution and the phase transitions occurred in sequence.

Ion-beam assisted deposition (IBAD) was carried out to deposit hydroxyapatite (HAp) on alumina substrate. The amorphous coating layer on alumina substrate is crystallized to the dense HAp after a post. treatment process of annealing at 500℃ for 2 h and immersion in deionized water for 72 h at room temperature. The homogeneous and dense HAp coating is observed by scanning electron microscopy and the thickness of the coating is measured to be about 638 um. The hardness of the coating 1ayer in the as-deposited and post-treated samples is 475 and 508, respectively. The adhesive strength between HAp and α-alumina substrate was measured by a scratch test. The ion-beam sputtered coatings were used as control samples, the adhesion was found to be worse for ion-beam sputtering deposition (IBSD) than for IBAD.

To investigate the mechanism of inhibition of silver ions on microorganisms, two strains of bacteria, namely Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus), were treated with AgNO3 and studied using combined electron microscopy and X-ray microanalysis. Similar morphological changes occurred in both E. coli and S. aureus cells after Ag+ treatment. The cytoplasm membrane detached from the cell wall. A remarkable electron-light region appeared in the center of the cells, which contained condensed deoxyribonucleic acid (DNA) molecules. There are many small electron-dense granules either surrounding the cell wall or depositing inside the cells. The existence of elements of silver and sulfur in the electron-dense granules and cytoplasm detected by X-ray microanalysis suggested the antibacterial mechanism of silver: DNA lost its replication ability and the protein became inactivated after Ag+ treatment. The slighter morphological changes of S. aureus compared with E. coli recommended a defense system of S. aureus against the inhibitory effects of Ag+ ions.

pitation from the 4 mM solution within the vesicles was amorphous calcium phosphate (ACp) and it remained stable at room temperature. The ACp was transformed into HAp crystals after treatment in hot water bath (60℃) for 24 h. As for the 0.03 mMsolution, which is nearly the critical saturation concentration of HAp, the precipitated crystals were small HAp. The role of the vesicle membrane in the controlled precipitation of calcium phosphate is discussed in terms of kinetic and spatial restrictions inherent in the reaction environment. The influence of concentration of calcium ion is also discussed.