Using a new and simple etching method to investigate the tablets of nacre, it is possible to observe a great deal of tablets in a large range. We found that most tablets have the same formal orientations after citric acid treatment. This phenomenon occurred not only in the same lamina but also along the direction perpendicular to nacreous plane. Based on the additional selected area diffraction patterns of transmission electron microscope, it is proposed that the formal orientations could indicate the crystal orientations of aragonite tablets.Statistical analyze shows that there is a main (type I tablets) and a secondary (type II tablets) preferred orientation with an angle of around 60 between them. Two possible modes of structural correspondence between protein sheets and aragonite lattice are assumed to interpret the orientation preference. On the other hand, the cluster character of type II tablets strongly supports that mineral bridges of the organic matrix have significant function in the crystal growth.At last, the mechanisms of structural correspondence and mineral bridges are combined to explain the formation process of nacreous layer in mussel.

The effects of phosphorylated chitin (P-chitin) on the tissue responses to two kinds of calcium phosphate cements (CPCs) were investigated using experimental rabbits. One of them consisting of monocalcium phosphate monohydrate, calcium oxide, 1 m phosphate buffer (pH: 7.4) and different amounts of P-chitin (CPC-I or P-CPC-I) with relatively neutral initial pH was filled as paste into tibial defects of the rabbits for 1, 4, 12 and 22 weeks. The other kind of cement made from dicacium phosphate dihydrate/calcium hydroxide/1m Na2HPO4/different amounts of P-chitin (CPC-II or P-CPC-II) with relatively higher initial pH was implanted as prehardened cylinders into the radial defects of the rabbits for the same periods. Pure CPC-I and CPC-II were used as controls. Histological and histomorphological studies were performed on thin un-decalcified and decalcified sections. Three different bone formation types in the resorption lacuna of the P-CPCs were found during this study. The biodegradation rate of the P-CPCs had a negative relationship with the P-chitin content. Most of the low P-chitin-containing samples were bioabsorbed in 16 weeks, while the high P-chitin-containing samples disappeared in 22 weeks. The newly formed bone was identified with back scattered scanning electron microscopy and X-ray energy-dispersive spectrometry. The results show that with P-chitin component in a certain range, the P-CPCs are biocompatible, bioabsorbable and osteoinductive and could be used as promising candidates of bone repair materials.

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

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.