Newly synthesized bentonite–histidine (Bent–His) micro-composite affinity sorbents for IgG adsorption

Bentonite has several advantages for use as a support, including its lack of toxicity, chemical reactivity and hydrophilicity allowing easy fixation of biomolecules. A new approach was developed to obtain an efficient and cost effective purification of IgG from human plasma. This study focused on developing bentonite–histidine micro-composite affinity sorbents (Bent–His) (38–105 μm) for immunoglobulin-G (IgG) adsorption from human plasma. The pseudo-biospecific affinity ligand l-histidine was reacted with covalent binding onto the bentonite structures. X-ray diffraction and FT-IR analysis of Bent–His composite affinity sorbents were performed. The surface area of the bentonite and Bent–His micro-composite structures were found as 33.00 ± 0.30 and 24.70 ± 0.30, respectively. An elemental analysis of immobilized l-histidine for nitrogen was estimated to be 541.3 μmol/g bentonite. The non-specific IgG adsorption onto bentonite structures was negligible (ca. 0.3 mg/g). Higher adsorption values up to 15.6 mg/g were obtained in which Bent–His micro-composite affinity sorbents were used from aqueous solutions. Isotherm studies were carried out to evaluate the effect of initial concentration of IgG, pH and the desorption characteristics of Bent–His micro-composite affinity sorbents. The maximum amount of IgG adsorption from aqueous solution in phosphate buffer was 15.6 mg/g at pH 7.0. A higher adsorption value was obtained from human plasma (up to 89.6 mg/g) with a purity of 94.5%. IgG molecules could be repeatedly adsorbed and desorbed with these micro-composite affinity sorbent systems without noticeable loss in their IgG adsorption capacity.