Cytotoxicity investigations of plasma sprayed calcium phosphate coatings

Abstract

One potential alternative material to replace hydroxyapatite (HAp) as a coating material for plasma-sprayed coatings on implants for hip replacement is fluorapatite (FAp). FAp has advantages over HAp regarding the capability of being chemically stable during the coating process. This leads to surface coatings containing high apatite rates with a mechanical stability (bond strength, microhardness) comparable to HAp. From the technical point of view the production of FAp coatings is well investigated, although studies on biocompatibility of FAp coatings are fewer. This paper reports the production of HAp and FAp coatings with varying solubilities by plasma spraying and their in vitro cytotoxicity. Varying solubilities were realized by using modified plasma-spray parameters in common with suitable apatite powders with different crystallinities. Coating solubilities were evaluated by immersing the plasma-sprayed coatings in deionized water and electrolyte solution. Afterwards, cytotoxicity tests were performed using a modified half-slide technique. Cell attachment and cell morphology were evaluated. Neither HAp nor FAp coatings exhibited cytoxic influence on cells in culture. Results suggest that HAp coatings stimulate cell growth and FAp coatings do not. This could be explained by a negative effect on cell growth of the dissolved fluoride ions.

The effect of fluoride contents in fluoridated hydroxyapatite on osteoblast behavior

“…The higher the level of fluoridation, the more fluoride ions released. As a result, besides its high thermal and chemical stability [3,11], FHA is considered as a promising implant material due to its great biological potential [12]. However, high F À concentration in bone can also lead to severe adverse effects such as osteomalacia [13].…”

Sol‐gel preparation and in vitro test of fluorapatite/hydroxyapatite films

“…Among them, plasma spray is the most prevalent. 2 However, plasma-sprayed coating usually has a thickness of tens of micrometers, so the film may have characteristics similar to those of HA ceramics. 6 Moreover, it seems difficult for the technique to precisely control the chemical compositions and microstructures of the coating.…”

Microstructural Properties of Air Plasma Sprayed Coating Consisting of Tungsten Carbide and Yttria‐Stabilized Zirconia

“…An ionized gas stream generated from an arc between two electrodes produces a plasma flow. Temperatures in the plasma stream could reach up to 15,000°C which is significantly above the melting point of any known material . APS is widely used for depositing the high temperature metallic material such as Inconel alloys, refractory, and ceramics such as zirconium‐based materials …”

“…Temperatures in the plasma stream could reach up to 15,000°C which is significantly above the melting point of any known material. 5 APS is widely used for depositing the high temperature metallic material such as Inconel alloys, refractory, and ceramics such as zirconium-based materials. 1,4 HVOF is another common method for deposition of high-quality coatings at relatively low cost.…”