Adsorption of human albumin onto hdroxyapatite. Static and dynamic studies

Abstract

The adsorption of albumin onto hydroxyapatite powder (HA) was studied at equilibrium and kinetically with an experimental system allowing continuous monitoring of the excess interfacial protein concentration with time. By assuming a Langmuir model and by applying a mass conservation law, it was possible to calculate the adsorption and desorption rate constants K a and k d and the affinity constant K, and to compare them with the value of 2.5 × 10 9 cm 3 mol −1 deduced from equilibrium studies. In dynamic studies, significant decreases in the adsorption rate and affinity constants were observed when protein injection rates were increased. To explain this unexpected result, we propose the occurrence of a cooperative effect by the molecules already adsorbed — and perhaps partly denatured — which might promote further adsorption of dissolved molecules.