Interaction of immunoglobulin G with N,N,N′,N′-ethylenediaminetetramethylenephosphonic acid-modified zirconia

Zirconia beads (25–38 μm in diameter) were modified with N,N,N′,N′-ethylenediaminetetramethylenephosphonic acid to generate a pseudo-biospecific support, r_PEZ. To better understand the force of interaction between the IgG and the r_PEZ, the equilibrium dissociation constant (Kd) was determined by static binding isotherms, as a function of temperature and by frontal analysis at different linear velocities. Temperature had no significant impact on the maximum static binding capacity (Qmax) and the equilibrium-binding constant (Kd), whereas pH and the salt concentration had a noticeable impact on both Qmax and Kd values. Qmax was found to be in the range of 55–65 mg IgG per ml of beads and unaffected by temperature. The maximum dynamic binding capacity (Qx) was found to be in the range of 20–12 mg IgG per ml of beads. The adsorption rate constant (ka) was determined by a split-peak approach to be between 982 and 3242 l mol−1 s−1 depending on the linear velocity. Adsorption rate of IgG on r_PEZ was studied as a function of both feed concentration and linear velocity. The standard enthalpy and entropy values were estimated for the interaction of IgG with this novel support. The binding constants were also determined by modeling the batch protein-uptake data.