Synthesis of Core@Brush microspheres by atom transfer radical polymerization for capturing phosphoprotein β-casein utilizing iron ion chelation and Schiff base bio-conjugation

Abstract

This paper aims to design a highly efficient adsorbent to capture phosphoprotein in a facile way. One of the applications would be removing the allergenic β-casein from vaccines. To avoid the use of organic reagents and improve the capacity of immobilized metal ion affinity chromatography applied for bio-products at neutral pH, synergistic functional Core@Brush microspheres were designed utilizing iron ion chelation and Schiff base bio-conjugation. Surface-initiated atom transfer radical polymerization (ATRP) was used to grow polymer brushes, composed of one carbonyl-containing functional monomer diacetone acrylamide (DAAM) and the other monomer glycidyl methacrylate (GMA), on active microspheres as the cores. Then the material was chemically modified with iminodiacetic acid and chelated with Fe(III). Adsorption studies show that the Core@Brush microspheres can selectively distinguish phosphoproteins with non-phosphoproteins, and has an excellent adsorption capacity over 2000 μg/mg towards β-casein owing to a large number of adsorption sites. The adsorption was well fitted to a pseudo-second-order kinetic model, indicating multi-valent chemisorption. The assumption is that β-casein was selectively captured by the synergistic function of stable iron ion chelation and reversible Schiff base bio-conjugation, and the particle-protein-particle aggregates formed.