Adsorption of Bovine Serum Albumin onto Hydroxylapatite: Theoretical Modeling and Measurements

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Adsorption of Bovine Serum Albumin (BSA) onto calcium Hydroxyl Apatite (HA), Ca10PO4(OH)2, has been studied by Ultra Violet (UV) spectroscopy. The adsorption isotherms of BSA onto the HA surface at 291.7 K and 303.2 K were satisfactorily presented by Langmuir equation and the evaluated parameters are reported. The specific surface area of HA has been measured by the BET method. The obtained value for the used HA sample was 63 m2/g. The effect of pH on BSA adsorption onto the HA in presence of salts KCl and NaF and phosphate ion has been investigated. In the fixed concentration of BSA (1 mg/mL) it is shown that the pH decreasing causes to increase of the adsorption of BSA onto HA. Considering the role of effective factors in BSA adsorption onto HA such as the size and charge of the BSA and the surface energy of HA showed that the electrostatic repulsion forces between HA and BSA cause a decrease in BSA adsorption onto HA. Also the obtained results indicated that the surface energy of HA predominates the effect of size and charge of BSA.