Adsorption characteristics of proteins on calcium phosphates using liquid chromatography.

The adsorption characteristics of various proteins on beta-Ca(3)(PO(4))(2) (beta-TCP), CaHPO(4). 2H(2)O (DCPD) and CaHPO(4) (DCPA) have been investigated using liquid chromatography. Acidic proteins were eluted from these calcium phosphate surfaces by potassium phosphate buffer (KP) but not by KCl and MgCl(2), whereas basic proteins were eluted by all three eluents. Such elution behavior can be interpreted by considering two kinds of adsorbing sites on the calcium phosphates, namely positively charged sites (Ca sites) which adsorb acidic proteins, and negatively charged sites (P sites) which adsorb basic proteins. A similar behavior has also been observed on Ca(10)(PO(4))(6)(OH)(2) (HAp) and Ca(8)H(2)(PO(4))(6). 5H(2)O (OCP). The order of the ratios of Ca-to-P sites was estimated to be DCPD > OCP > HAp >> DCPA >> beta-TCP, which is in agreement with the order of the surface zeta potentials. In addition, the (0k0) surface of DCPD is suggested to consist mainly of Ca sites. The total number of Ca sites on beta-TCP is thought to be significantly smaller than the other calcium phosphates. Copyright 2001 John Wiley & Sons, Inc. J Biomed Mater Res 55: 409-414, 2001