Construction Of Model Surfaces With Glycopolymer Brushes And Lectin Adsorption

The interaction between glycopolymer brushes and lectins is very important for protein separation by affinity membrane chromatography. Here, we utilized surface-initiated atom transfer radical polymerization (SI-ATRP) and surface plasmon resonance (SPR) to investigate the relationship between structures of glycopolymer brushes and lectin adsorption. Specific studies are mainly focused on the following aspects:A vinyl monomer with galactose pendant,2-lactobionamidoethyl methacrylate (LAMA), was synthesized via a two-step routine with90%yield. Initiators of ATRP were fixed on gold surface by self-assembly of mercaptoundecanol (MUD). Glycopolymer brushes with different thicknesses were fabricated through SI-ATRP in a living fashion. The grafting density was controlled by changing the density of the initiator by mixing of MUD and undecanethiol. Random copolymerization of2-hydroxyethyl methacrylate (HEMA) and LAMA was achieved both in liquid phase and on solid surface. LAMA proportion in the resulted polymer was corresponding to that in the monomer solution.SPR was used to study effects of brush thickness, grafting density and epitope density on the adsorption of lectin RCA120, which binds galactose specifically. Results indicate that mass transport effect is the key point. The total amount of adsorbed RCA120only increased when the brush thickness was less than10nm because lectin molecules can only reach limited depth. As the grafting density was raised, the amount of adsorbed lectin increased and then levelled off. The mass transport coefficient was reduced by increasing grafting density due to the increasing steric hindrance. Similarly, the highest binding capacity was achieved with a LAMA proportion of30%. Additional sugar pendant will lower the binding strength and the transport velocity.In conclusion, we tuned the brush thickness, grafting density and sugar epitope density and achieved an optimal steric arrangement for lectin binding, and it is important to keep the balance between the sugar cluster effect and the mass transport effect for the preparation of high-performance affinity membrane chromatography.