The clinical use of plasma-sprayed hydroxyapatite (HA) coatings on metal implants has been widely adopted because the HA coating can achieve the firmly and directly biological fixation with the surrounding bone tissue. However, the long-term mechanical properties of HA coatings has been concern for the long-term clinical application. Previous research showed that the concept of adding ZrO2 as second phase to HA significantly increased the bonding strength of plasma-sprayed composite material. The present work aimed to explore the biological properties, including the histological responses and shear strength, between the plasma-sprayed HA and HA/ZrO2 coating, using the transcortical implant model in the femora of canines. After 6 and 12 weeks of implantation, the HA coating revealed the direct bone-to-coating contact by the backscattered electron images (BEIs) of scanning electron microscope (SEM), but the osseointegration was not observed at the surface of HA/ZrO2 coating. For new bone healing index (NBHI) and apposition index (AI), the values for HA implants were significantly higher than that for HA/ZrO2 coatings throughout all implant periods. After push-out test, the shear strength of HA-coated implants were statistically higher than HA/ZrO2 coated implants at 6- and 12-week implantation, and the failure mode of HA/ZrO2 coating was observed at the coating-bone interface by SEM. The results indicate that the firm fixation between bone and HA/ZrO2 has not been achieved even after 12-week implantation. Consequently, the addition of ZrO2 could improve the mechanical properties of coatings, while the biocompatibility was influenced by the different material characteristics of HA/ZrO2 coating compared to HA coatings.

The growth of hollow tubes, nanowire array, and segmented porous nanowire arrays made of Cu–Zn alloys in a Lewis acidic ZnCl2-1-ethyl-3-methylimidazolium chloride ionic liquid via direct electrodeposition without the need for a template is presented. The formation of each of type of structure is described. Hollow tubes result from the uneven overpotential gradient created at low Cu(I) concentration and low applied deposition overpotential. Nanowire arrays form under mass-transport-limited conditions, in which the ionic liquid speciation plays an important role. Segmented porous nanowire arrays are obtained by increasing the Cu(I) concentration to enhance the concentration profile vibration near the growth surface. The electrodeposited nanowire arrays show very good efficiency for the electrocatalytic reduction of nitrate ions in alkaline aqueous solution.

No abstract

The biocompatibility of material plays an important role in the bone-implant interface for the prosthetic implant fixation. The biocompatibility of implants is associated with the chemical composition, surface topography, surface energy and surface roughness of biomaterials. The effects of two factors, surface roughness and serum contents, on osteoblast behavior at the surface of Ti-6Al-4V and plasma sprayed HA coating were investigated in the experiment. The osteoblasts derived from neonatal rat calvarial were cultured in Dulbecco's modified Eagle medium (DMEM) with fetal bovine serum (FBS) on the surface of polished Ti-6Al-4V (Ti-p), grit-blasted Ti-6Al-4V (Ti-b), polished HA coating (HAC-p), and as-sprayed HA coating (HAC). Under culture medium containing 4% FBS, the level of cell attachment to the polished surface is significantly higher than the rough surface of the same experimental materials during all culture periods. Increasing the contents of FBS up to 10%, the difference of osteoblast attachment is not found between Ti-p and Ti-b. Under 4% serum condition, the cell morphology attached to smooth surfaces (Ti-p and HAC-p) is spread faster and are more flattened than the one to rough surface of the same experimental materials by SEM. After 24 h culture, the corroded cracks are easily observed at the surface of polished HA coatings, and the cell morphology on HAC-p coatings are elongated and less flattened compared with Ti-p. The result is consistent with statistical difference of cell attachment between Ti-p and HAC-p under 4% serum condition.

Plasma-sprayed hydroxyapatite (HA) coating, applied to metal substrates, can induce a direct chemical bond with bone and hence achieve a biological fixation of the implant. However, the poor bonding strength between the HA coating and the substrate has been a concern for the orthopedists. In a previous study, the zirconia-reinforced hydroxyapatite composite coatings (HA/ZrO(2)) could significantly improve the mechanical strength before and after soaking in simulated body fluid. This study aims to investigate the biological responses of osteoblasts on plasma-sprayed HA/ZrO(2) coating. The osteoblasts derived from neonatal rat calvarial were cultured in Dulbecco's modified Eagle medium (DMEM) with fetal bovine serum (FBS) on the surface of plasma-sprayed HA coating, HA/ZrO(2) coating, and ZrO(2) coating, respectively. The biological responses were investigated by the cell growth (1, 3, 5, and 10 days) and the cell morphology under scanning electron microscopy (SEM) (3, 6, 12, 24 and 48 h). Examination by SEM revealed that osteoblasts on HA coatings exhibit less spreading during the medium phase (6 and 12 h), while, better morphologies were observed at the latter phases (24 and 48 h). This should be derived by the dissolution of HA coating in the culture medium. On HA/ZrO(2) coating, the cells showed the poor morphologies at the latter phases (24 and 48 h). This could be explained by the no apatite formed at the surface HA/ZrO(2) coating after soaking in simulated body fluid. The lower contents of ZrO(2) coating in HA coating and the addition of other solid solution (ZrO(2)-MgO, CaO-ZrO(2), ZrO(2)-CeO(2)) in HA coating are the two possible methods to improve the cytocompatibility of HA/ZrO(2) coating.