ADSORPTION OF BOVINE SERUM-ALBUMIN ONTO HYDROXYAPATITE

The adsorption of bovine serum albumin (BSA) onto hydroxyapatite (HA) has been studied as a function of protein concentration, pH and ionic strength. Isotherm data (adsorption being a reversible process) have been analysed using the Langmuir model, the adsorption parameters A(T) (maximum amount of protein adsorbed, mg m(-2)) and K (affinity constant, L g(-1)) being calculated for each solution condition (except NaF). For the pH dependence of adsorption, both A(T) and K increase with decreasing pH, indicating that both electrostatic and hydration effects are important. For the ionic strength dependence, increasing NaCl concentrations result in a slight increase in A(T), but K decreases. With increasing CaCl2 concentrations the A(T) and K values increase, the opposite being true for increasing concentrations of Na2HPO4. NaF both enhances and inhibits adsorption depending on the concentration. Possible reasons for these results are discussed.