Sol-gel derived fluor-hydroxyapatite biocoatings on zirconia substrate.

Fluor-hydroxyapatite (FHA) film was coated on a zirconia (ZrO(2)) substrate by a sol-gel method. An appropriate amount of F ions was incorporated into the hydroxyapatite (HA) during the preparation of the sols. The apatite phase began to crystallize after heat treatment at 400 degrees C, and increased in intensity above 500 degrees C. No decomposition was detected by X-ray diffraction analyses up to 800 degrees C, which illustrates the high thermal stability of the FHA films. The films showed a uniform and dense morphology with a thickness of approximately 1 microm after a precisely controlled heat treatment process. These FHA films adhered firmly to the zirconia substrate, representing notable adhesion strengths of approximately 70 MPa after heat treatment above 500 degrees C. The dissolution rate of the FHA coating layer varied according to the heat treatment temperature, which was closely related to the film crystallinity. The dissolution rate of the FHA film was lower than that of the HA film, suggesting the possibility of a functional gradient coating of HA and FHA. The MG63 cells seeded onto the FHA films proliferated in a similar manner to those seeded onto pure HA ceramic and a plastic control.

Eotaxin and monocyte chemotactic protein-3 use different modes of action.

Eotaxin selectively binds CC chemokine receptor (CCR) 3, whereas monocyte chemotactic protein (MCP)-3 binds CCR1, CCR2, and CCR3. To identify the functional determinants of the chemokines, we generated four reciprocal chimeric chemokines-M10E9, M22E21, E8M11, and E20M23-by shuffling the N-terminus and N-loop of eotaxin and MCP-3. M22E21 and E8M11, which shared the N-loop from MCP-3, bound to monocytes with high affinity, and activated monocytes. In contrast, M10E9 and E20M23, which lacked the N-loop, failed to bind and transduce monocyte responses, identifying the N-loop of MCP-3 as the selectivity determinant for CCR1/CCR2. A BIAcore assay with an N-terminal peptide of CCR3 (residues 1-35) revealed that all chimeras except E20M23 exhibited varying degrees of binding affinity with commensurate chemotaxis activity of eosinophils. Surprisingly, E20M23 could neither bind the CCR3 peptide nor activate eosinophils, despite having both N-terminal motifs from eotaxin. These results suggest that the two N-terminal motifs of eotaxin must cooperate with other regions to successfully bind and activate CCR3.

Porous ZrO2 bone scaffold coated with hydroxyapatite with fluorapatite intermediate layer.

Highly porous zirconia (ZrO(2)) bone scaffolds, fabricated by a replication technique using polymeric sponge, were coated with hydroxyapatite (HA). To prevent the chemical reactions between ZrO(2) and HA, an intermediate fluorapatite (FA) layer was introduced. The strength of the porous ZrO(2) was higher than that of pure HA by a factor of 7, suggesting the feasibility of ZrO(2) porous scaffolds as load-bearing part applications. The coated HA/FA layer, with a thickness of about 30 microm, was firmly adhered to the ZrO(2) body with a bonding strength of 22MPa. The osteoblast-like cells were attached and spread well on the coating layer throughout the porous scaffolds. The alkaline phosphatase activity of the proliferated cells on the HA/FA coated ZrO(2) was comparable to that on pure HA and higher than that on pure ZrO(2).

Enhanced performance of fluorine substituted hydroxyapatite composites for hard tissue engineering.

Dense fluorine (F) substituted hydroxyapatite composites with yttria-doped zirconia (Y-TZP) and/or alumina (Al(2)O(3)) were successfully fabricated without applying pressure at 1400 degrees C for 3 h. The suppression of decomposition via the formation of a fluor-hydroxyapatite (FHA) solid solution allowed the sintered body to reach full density. Such fully densified FHA-composites exhibited improved mechanical properties, such as strength, toughness, and hardness, having values of more than approximately 2-4 times higher than those of pure HA or HA-composites. The proliferation behavior of osteoblast-like cells on the FHA-composites showed no cytotoxicity and comparable cell viability to that observed in pure HA for up to 10 days.

Effect of CaF2 on densification and properties of hydroxyapatite-zirconia composites for biomedical applications.

Hydroxyapatite (HA) composites with zirconia (ZrO2) up to 40 vol% were fabricated with the addition of CaF2. The sinterability of the composites was found to be enhanced markedly by the addition of small amounts of CaF2 (< 5 vol%). Decomposition of HA to beta-TCP was suppressed due to the substitution of F- for OH-, consequently forming fluor-hydroxyapatite (FHA) solid solution. This suppression of decomposition allowed the production of a fully dense body, which retained both high flexural strength and fracture toughness. The osteoblast-like cell (MG63) response to these F- ion-containing composites displayed comparable cell viability to pure-HA by in vitro proliferation test.