Effect of fluorine addition on the biological performance of hydroxyapatite coatings on Ti by aerosol deposition.
ABSTRACT Dense and well-adherent fluoridated hydroxyapatite [Ca(10)(PO(4))(6)(OH)(2-x )F( x ), FHA] coatings with various amounts of fluorine contents (x = 0, 0.5, 1.0, 1.5, and 2.0) were deposited on commercially available pure titanium by aerosol deposition using FHA powders in order to investigate the effect of fluorine content on the properties of the coatings. FHA powders with different compositions were synthesized by solid-state reactions of hydroxyapatite (HA) and fluorapatite (FA) powders at various ratios. X-ray diffraction and Fourier transform infrared spectroscopy results showed that fluoride ions were successfully incorporated into the HA lattice for both the FHA powders and the FHA coatings. Scanning electron microscopy analysis revealed dense microstructures and good substrate adhesion of the coatings with high adhesion strengths of more than 33.1 MPa. The dissolution behavior in a tris-buffered saline solution indicated that the dissolution rate of the FHA coatings decreased as a result of increasing the fluorine content in the coatings. In addition, in vitro cellular tests, including cell attachment, proliferation, and alkaline phosphatase activity of MC3T3-E1 preosteoblast cells grown on the coatings, demonstrated that an FHA coating with a moderate degree of F(-) substitution, x = 1.0, had a stronger stimulating effect on cell proliferation and differentiation. These results suggested that there exists an optimum fluorine content level in the FHA coatings for the best long-term stability and cellular responses.
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ABSTRACT: A systematic analysis of results available from in vitro, in vivo, and clinical trials on the effects of biocompatible CaP coatings is presented. An overview of the most frequently used methods to prepare CaP-based coatings was conducted. Dense, homogeneous, highly adherent, and biocompatible CaP or hybrid organic/inorganic CaP coatings with tailored properties can be deposited. It has been demonstrated that CaP coatings have a significant effect on the bone regeneration process. In vitro experiments using different cells (e.g. SaOs2, hMSCs, and osteoblast-like cells) have revealed that CaP coatings enhance cellular adhesion, proliferation, and differentiation to promote bone regeneration. However, in vivo, the exact mechanism of osteogenesis in response to CaP coatings is unclear, indeed there are conflicting reports of the effectiveness of CaP coatings with results ranging from highly effective to no significant or even negative effects. This review will therefore highlight progress in CaP coatings for orthopaedic implants and discuss the future research and use of these devices. Currently, an exciting area of research is in bioactive hybrid composite CaP-based coatings containing both inorganic (CaP coating) and organic (collagen, BMPs, RGD etc.) components with the aim of promoting tissue ingrowth and vascularisation. Further investigations are necessary to reveal the relative influences of implant design, surgical procedure, and coating characteristics (thickness, structure, topography, porosity, wettability etc) on the long-term clinical effects of hybrid CaP coatings. In addition to commercially available plasma spraying, other effective routes for the fabrication of hybrid CaP coatings for clinical use still need to be determined and current progress is discussed.Acta biomaterialia 11/2013; · 5.68 Impact Factor
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ABSTRACT: Vacuum kinetic spray(VKS) is a relatively advanced process for fabricating thin/thick and dense ceramic coatings via submicron-sized particle impact at room temperature. However, unfortunately, the particle velocity, which is an important value for investigating the deposition mechanism, has not been clarified yet. Thus, in this research, VKS average particle velocities were derived by numerical analysis method(CFD: computational fluid dynamics) connected with an experimental approach(SCM: slit cell method). When the process gas or powder particles are accelerated by a compressive force generated by gas pressure in kinetic spraying, a tensile force generated by the vacuum in the VKS system accelerates the process gas. As a result, the gas is able to reach supersonic speed even though only 0.6MPa gas pressure is used in VKS. In addition, small size powders can be accelerated up to supersonic velocity by means of the drag-force of the low pressure process gas flow. Furthermore, in this process, the increase of gas flow makes the drag-force stronger and gas distribution more homogenized in the pipe, by which the total particle average velocity becomes higher and the difference between max. and min. particle velocity decreases. Consequently, the control of particle size and gas flow rate are important factors in making the velocity of particles high enough for successful deposition in the VKS system.Korean Journal of Materials Research 02/2014; 24(2).