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 proposed 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 densities 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.

Keywords

• Polymer membranes
• PVDF
• PES
• Protein A
• Plasma