The modulation function of proteins was studied during biomineralization in vitro. Morphological development of calcium carbonate precipitation in collagen solutions at different concentrations has been examined using scanning electron microscope. X-ray diffraction is used to determine the polymorph of calcium carbonate crystals. Its data indicate that only calcite crystals are formed. The experimental results also show that the calcite growth is more and more inhibited as collagen is increasing in concentration. A simple crystal model is employed to explain these phenomena. Different crystal planes with different affinities to collagen play a crucial role in changing the morphology of calcite crystals.

The antimicrobial ceramics (AC) based on hydroxyapatite (HA) were made in a wet chemical process with additions of AgNO3, Cu(NO3)2

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.

Ion beam assisted deposition (IBAD) has been successfully used to produce a dense ultra-adherent and pinhole-free hydroxyapatite (HAp) layer on alumina substrates. After deposition the HAp-coated alumina was immersed in 20 ppm and 100 ppm AgNO3 solution to carry out the ion exchange between Ag1 and Ca21 in HAp. An obvious antimicrobial effect against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Staphylococcus epidermidis was observed in the samples treated with 20 ppm AgNO3 solution. In contrast to this, the untreated samples did not show any bactericidal effect. Scanning electron microscopy (SEM) studies showed that Ag-rich phases were homogeneously distributed on the surface. X-ray diffraction (XRD) demonstrated that the surface structure in the samples without Ag was HAp, whereas with Ag it is HAp and AgCaP. The minimum inhibitory concentration of AgNO3 was measured to be 1.302 mg/ml. The release of Ag1 ions from the Ag-HAp

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.