Preparation and characterization of Protein A-immobilized PVDF and PES membranes

Abstract

Polyvinylidene fluoride (PVDF) and polyether sulfone (PES) membranes were activated using low-temperature plasma at atmospheric pressure, and their surface characteristics were investigated. In the plasma-treated PVDF, the XPS data showed that defluorination and oxidation reactions proceeded to 18 and 31%, respectively, at ±4.0 kVp-p for 180 s. Hydroperoxide groups were detected on both the plasma-treated membranes. By decomposing the S2p spectrum, it was proven that the sulfide and sulfo groups were newly formed on the plasma-treated PES. Based on these findings, we pro- posed an activation mechanism. The SEM images showed that the macrovoid formations were maintained after the plasma treatment. Polyacrylic acid (PAA) was grafted on both of the plasma-treated membranes by thermal treatments. Protein A, originating from Staphylococcus aureus, was immobilized on the membrane grafted with PAA using the EDC/Sulfo-NHS system. Adsorption isotherms with a human immunoglobulin G (IgG) antibody were fitted with the monolayer Langmuir model, and the maximum binding capacity (qm) and equilibrium association constant (Ka) were obtained. The ligand densi- ties of the PVDF (pore size 0.45 and 5.0 µm) and PES (pore size 0.45 µm) membranes were 0.98, 1.42 and 2.06 mg·mL -1 , respectively.