Adsorption of dextrans onto hydroxyapatite: Presence of maxima

Hydroxyapatite has been widely used as a model substrate for studying biological systems involving mineralization and protein adsorption. In the present study, hydroxyapatite from three commercial sources was used to study the adsorption behavior of commercially available dextrans. Depending on the molecular weight of dextran and the technique used for dispersing the solid, maxima were observed in the adsorption isotherms for all three adsorbents. Scanning electron microscopy observations showed significant differences in the morphological properties of the hydroxyapatite samples. The adsorption maximum is attributed to the inability of the polymer molecules to diffuse into the interior of hydroxyapatite aggregates. The adsorption results have been analyzed to estimate the pore volume and the average pore size in the aggregates.