Zinc containing hydroxyapatite ceramics to promote osteoblastic cell activity

Abstract

Calcium phosphate ceramics with a (CazZn)/P molar ratio of 1 . 67 containing various amounts of zinc (ZnHAP ceramics) were synthesised and their effect on promoting osteoblastic cell proliferation was examined. Above 0 . 13 wt-%Zn, which is the solid solution limit of zinc in hydroxyapatite (HAP), zinc containing tricalcium phosphate (ZnTCP) phases appeared in the ZnHAP ceramics. The TCP phases were in b or a form, or both, depending on the sintering temperatures and zinc content. A monophasic ZnHAP ceramic was obtained only when ZnHAP with a zinc content of less than 0 . 13 wt-% was sintered from 1050 to 1150uC. When zinc was incorporated only in HAP crystal lattice, thereby having no TCP phases, no marked release of zinc from ZnHAP ceramics was observed in either the cell culture medium or in the acetic acid -sodium acetate buffer solution at pH 5. Without TCP phases, ZnHAP ceramics showed no influence on the proliferation of MC3T3-E1 cells in vitro. The optimum zinc content of ZnHAP ceramics for promoting osteoblastic cell proliferation was 0 . 34 wt-%. The present study demonstrated that the incorporation of zinc beyond the solid solution limit converted the HAP ceramic into a zinc releasing calcium phosphate material.MST/6206

Zinc incorporation into hydroxylapatite

“…Substitution into the P position was not considered as our initial EXAFS fitting, because substitution in this site is very unlikely (as described in Section 3.4). In addition, a previous experimental study [42] showed that the (Ca þ Zn)/P ratio remained at the phase-pure HAP value of 1.67, confirming Ca positions as the substitution sites. In order to determine the most stable configuration, formation energies were calculated using,…”

Cationic and Anionic Substitutions in Hydroxyapatite

“…Regarding the effect of zinc substitution on the HAp lattice structure, there are many conflicting reports [136,137,144].…”

“…Some XRD studies evidenced that there was the formation of α-zinc tricalcium phosphate phase after calcination at 1050 C, in the case of Zn amount higher than 0.13 wt% [137].…”

Cellular proliferation, cellular viability, and biocompatibility of HA‐ZnO composites

“…12,13 Zn also stimulates the new bone formation in vivo, when tested in rabbit femur. 14 However, excessive extracellular Zn concentration can lead to the breakdown of Zn transporting system of plasma membrane, disruption of the Zn homeostatic system, and cellular transduction processes. Also, the resulting higher intracellular Zn concentration will induce cellular apoptosis.…”