Effect of protein on the dissolution of HA coatings

The dissolution behavior of hydroxyapatite (HA) in the presence and absence of protein needs to be investigated in order to fully understand the initi al cellular response to HA surfaces. In this study, HA coatings were charac terized using X-ray diffraction, X-ray photoelectron spectroscopy, and Four ier transform infrared spectroscopy (FTIR) prior to protein study. Fibronec tin and albumin adsorption study were also performed. Calcium and phosphoru s released in the presence and absence of albumin were measured. pH of the solution was measured daily. From the materials characterization, it was ob served that the coatings exhibit a HA-type structure, with traces of sodium on the surface. FTIR indicated the possible presence of carbonates on the coatings. From the adsorption study, the amount of albumin adsorbed (0.052 +/- 0.005 mu g/mm(2)) was statistically higher than the amount of fibronect in adsorbed on HA surfaces (0.035 +/- 0.002 mu g/mm(2)). Flame atomic absor ption indicated a significantly higher calcium ions released initially for HA coatings incubated with proteins as compared to coatings in the absence of proteins. However, after 7 days incubation, no significant difference in calcium ions release was observed between the HA coatings in the presence and absence of proteins. Phosphorus dissolution on HA coatings was not sign ificantly affected by the presence of proteins. Thus, it was suggested from this study that the initial dissolution properties of calcium ions from HA coatings was dependent on the media. (C) 1999 Elsevier Science Ltd. All ri ghts reserved.