Synthesis of Poly[(hydroxyethyl methacrylate)-co-(methacrylamidoalanine)] Membranes and Their Utilization as an Affinity Sorbent for Lysozyme Adsorption

Abstract

Various adsorbent materials have been reported in the literature for protein separation. We have developed a novel and new approach to obtain high protein-adsorption capacity utilizing a 2-methacrylamidoalanine-containing membrane. An amino acid ligand 2-methacrylamidoalanine (MAAL) was synthesized from methacrylochloride and alanine. Then, poly[(2-hydroxyethyl methacrylate)-co-(2-methacrylamidoalanine)] [p(HEMA-co-MAAL)] membranes were prepared by UV-initiated photopolymerization of HEMA and MAAL. The synthesized MAAL monomer was characterized by NMR spectrometry. p(HEMA-co-MAAL) membranes were characterized by swelling studies, porosimeter, scanning electron microscopy, FT-IR spectroscopy and elemental analysis. These membranes have large pores; the micropore dimensions are around 5–10 μm. p(HEMA-co-MAAL) affinity membranes with a swelling ratio of 198.9%, and containing 23.9 (mmol MAAL)·m–2 were used in the adsorption of lysozyme from aqueous media containing different amounts of lysozyme (0.1–3.0 mg·ml–1) and at different pH values (4.0–8.0). The effect of Cu(II) incorporation on lysozyme adsorption was also studied. The non-specific adsorption of lysozyme on the pHEMA membranes was 0.9 μg-cm–2. Incorporation of MAAL molecules into the polymeric structure significantly increased the lysozyme adsorption up to 2.96 mg·cm–2. The lysozyme-adsorption capacity of the membranes incorporated with Cu(II) (9.98 mg·cm–2) was greater than that of the p(HEMA-co-MAAL) membranes. More than 85% of the adsorbed lysozyme was desorbed in 1 h in the desorption medium containing 1.0 M NaCl. The p(HEMA-co-MAAL) membranes are suitable for repeated use for more than 5 cycles without noticeable loss of capacity. These features make p(HEMA-co-MAAL) membrane a very good candidate for bioaffinity adsorption.