Poly(2-hydroxyethylmethacrylate)/chitosan dye and different metal-ion-immobilized interpenetrating network membranes: Preparation and application in metal affinity chromatography

Composite membranes were synthesized with 2-hydroxyethylmethacrylate and chitosan (pHEMA/chitosan) via an ultraviolet-initiated photopolymerization technique in the presence of an initiator (alpha,alpha'-azobisisobutyronitrile). The interpenetrating network (IPN) membranes were improved by the immobilization of dye molecules via hydroxyl and amino groups on the membrane surfaces from the IPNs. A triazidine dye (Procion Green H-4G) was covalently immobilized as a ligand onto the IPN membranes. The protein showed various affinities to different chelated metal ions on the membrane surfaces that best matched its own distribution of functional sites, resulting in a distribution of binding energies. In support of this interpretation, two different metal ions, Zn(II) and Fe(III), were chelated with the immobilized dye molecules. The adsorption and binding characteristics of the different metal-ion-chelated dye-immobilized IPN membranes for the lysozyme were investigated with aqueous solutions in magnetically stirred cells. The experimental data were analyzed with two adsorption kinetic models, pseudo-first-order and pseudo-second-order, to determine the best fit equation for the adsorption of lysozyme onto IPN membranes. The second-order equation for the lysozyme-dye-metal-chelated IPN membrane systems was the most appropriate equation for predicting the adsorption capacity for all the tested adsorbents. The reversible lysozyme adsorption on the dye-immobilized and metal-ion-chelated membranes obeyed the Temkin isotherm. The lysozyme adsorption capacity of the pHEMA/chitosan dye, pHEMA/chitosan dye-Zn(II), and pHEMA/chitosan dye-Fe(III) membranes were 2.54, 2.85, and 3.64 mg cm(-2), respectively. The nonspecific adsorption of the lysozyme on the plain pHEMA/chitosan membrane was about 0.18 mg cm(-2). (C) 2003 Wiley Periodicals, Inc.