Bone-like crystals were acceleratingly grown in a simulated body fluid on the negatively charged surface of electrically poled hydroxyapatite ceramics, while the crystal growth was completely inhibited on the opposite surface. The poling effect was generalized by the enhanced crystal growth on the poled ferroelectric ceramics of BaTiO3 and CaTiO3.

Acceleration and Deceleration of Bone-Like Crystal Growth on Ceramic Hydroxyapatite by Electric Poling

Factors influencing the removal of divalent cations by hydroxyapatite

Adherence of cells to a surface, such as a biomaterial surface, can be significantly influenced by the surface charge on that material. The applicability of electrically charged hydroxyapatite ceramics to selective cell adhesion was examined, and we show that polarized hydroxyapatite has significant effects on cell growth and adhesion. The surface charge applied to polarized hydroxyapatite promotes (i) enhanced colony formation of osteoblast-like cells, (ii) activation of gap junctions, and (iii) specific orienting of neuroblastoma cells. These findings will be of great utility and have significance in applications of tissue engineering, for example, in potential treatments for osteoporosis.

Manipulation of selective cell adhesion and growth by surface charges of electrically polarized hydroxyapatite.

Three hydroxyapatite(HA)-based materials have been investigated with respect to their potential for removing heavy metal ions from aqueous solutions. The materials have been evaluated as both loose powders and in the form of ceramic foams. The results have shown that all three grades of HA were found to be capable of removing a number of different ionic species although the more impure grades generally yielded the best performance. It is believed that the increased impurity levels resulted in increased numbers of lattice defects which were ideal adsorption/exchange sites. 100% removal could be achieved for some ions under the correct experimental conditions. For the ceramic foam filters, the optimum filtration parameters were found to be a high surface area, long filtration times, a low pH and a high filtrate temperature. Ion adsorption was positively detected as a mechanism of ion removal. Ion exchange was not observed but could not be completely ruled out.

An evaluation of hydroxyapatite-based filters for removal of heavy metal ions from aqueous solutions

Electrically polarized HAp-coated Ti: in vitro bone cell-material interactions.

https://www.jstage.jst.go.jp/article/cpb1958/29/8/29_8_2116/_pdf

Adsorption of Mono-and Divalent Metal Cations on Hydroxyapatite in Water

Hydroxyapatite (HAP) in water exhibited a buffer function in the region from weakly acidic through weakly alkaline pH. Equilibrium pH depends on the amount of HAP added, and on the species and concentration of added electrolyte. This function seems to originate from the ability of HAP to adsorb OH-and/or from the protonation-deprotonation equilibrium of surface phosphate ion. Theoretical calculation of the suspension pH was attempted. The isotherm of OH- adsorption from aqueous solutions of NaOH mixed with NaCl was of Langmuir type. The saturated amount of OH- adsorption was almost constant irrespective of the amount of NaCl added, but the binding constant increased with the amount of added NaCl. The adsorption isotherms, however, formed just one curve irrespective of the amount of NaCl added when they were expressed as a function of the thermodynamic activity of NaOH. On the other hand, the amount of adsorbed OH- increased with the amount of Ca2+ added, because Ca2+ is adsorbed on the HAP surface and forms a positively charged adsorption site for OH-. An electrophoresis experiment confirmed that HAP particles have positive charges due to adsorbed Ca2+ even in solutio at high pH.

Chizuko Tamura

Papers

Adsorption of Mono-and Divalent Metal Cations on Hydroxyapatite in Water

Adsorption of Hydroxyl Ion on Hydroxyapatite