The Influence of Fluoride on the Uptake of Protein by Hydroxyapatite

Abstract

A brief pretreatment of hydroxyapatite with 1 mM of fluoride caused a reduced uptake of the acidic protein albumin, whereas an increased uptake of the basic protein protamine was observed. Pretreatment with the cations calcium or aluminium had the opposite effect. It is suggested that surface adsorption of the ions in question and changed surface charge of the apatite may be the mechanism involved. The fluoride taken up by the hydroxyapatite during the pretreatment was to a large extent soluble in 1 M KOH, showing that only small amounts of fluoroapatite were formed. As no calcium fluoride could be have been precipitated during the experimental conditions used, an adsorption of fluoride to calcium sites on the surface or in the hydration shell of the hydroxyapatite is postulated.