REDUCED BOVINE SERUM-ALBUMIN ADSORPTION BY PREPHOSPHATATION OF POWDERED ZIRCONIUM-OXIDE

The adsorption of phosphate anions to ZrO2 and its influence on protei n adsorption have been studied. Phosphate adsorption experiments revea led that phosphate anions had a high affinity for zirconia: in appropr iate conditions, a monomolecular layer was adsorbed. Using the electro phoretic light scattering technique, it was shown that the isoelectric point of the zirconium oxide was shifted from pH 6.4 down to pH 3.8, From this shift, it was concluded that specific interactions were resp onsible for the adsorption behaviour. In addition, the adsorption of b ovine serum albumin (which was selected as a model protein) to both ba re and phosphated zirconia was investigated: prephosphatation reduced the BSA adsorption by over 50%. Comparing the adsorption behaviour at pH 4.15 and 5.35, it was concluded that electrostatic interactions wer e of minor importance. From contact angle measurements, the different adsorption behaviour was shown to be due to the increased hydrophilici ty of the phosphated adsorbent. On the basis of the present results, t he observed effect of phosphate ions in ultrafiltration of proteins on ZrO2 ceramic ultrafiltration membranes may be explained.