The Establishment Of A Functional Platform For Regenerated Cellulose Membranes And The Study Of Protein Adsorption

Traditional packed bed chromatography has been used widely in protein separation over the past decades.However,the disadvantages of high pressure drop,long equilibrium time and a large amount of eluent volume in the purification process restrict its development.While membrane chromatography has become a new alternative resulting from a fast combination between the solutes and binding sites with a lower pressure drop and a shorter process time.Generally speaking,protein can be adsorbed onto stationary phase by three main interaction forms:hydrophobic interaction;electrostatic interaction and affinity interaction.But traditional single-mode chromatography based on the above interaction is difficult to combine the two advantages of low cost and high selectivity.While mixed mode chromatography(MMC)which couples two different adsorption mechanisms is expected to solve the problem.But there is still a lack of a simple chemistry for orthogonal design of the ligands of mixed mode chromatography.There are still few reports on mixed mode chromatography membrane adsorbers.One-pot multistep reaction is an important research direction in the field of polymer chemistry in recent years,which is used widely in various research field,such as anti-fouling,separation,adsorption and so on.In this paper,surface-initiated atom transfer radical polymerization(ATRP)is combined with thiolactone ring-opening chemistry to achieve bifunctionalization of cellulose membrane and orthogonal regulation of two ligands on the membrane surface.Firstly,MMA and St-Tla were copolymerized onto the membrane surface via ATRP.Then n-butylamine/Methacrylic acid and octylamine/Methacrylic acid were selected as the modifier to prepared two different membrane adsorbers denoted as RC-HIC/IEC(hydrophobic/ion-exchange)and RC-RPC/IEC(reversed phase/ion-exchange)through amine-thiol-ene conjugation.Consequently,hydrophobic alkyl chains and carboxyl groups were introduced into the polymer side chains.Grafting yield(GY)was characterized by weighing method.The chemical structure was characterized by ATR-FTIR and XPS.In addition,membrane surface morphology was characterized by SEM and AFM.Finally,we selected Immunoglobulin G(IgG)and a-Chymotrypsin(a-CTP)as the model protein to study the adsorption performance of RC-HIC/IEC and RC-RPC/IEC,respectively.And results showed that GY of 99.5μg/cm2 was achieved under the parameters:Molar ratio MMA:St-Tla=8:1;grafting time was 4 h and the polymerization temperature was 70 ℃.Membrane surface roughness and water contact angle increased significantly.Furthermore,the RC-HIC/IEC had the highest statistic IgG adsorption capacity of 73.5μg/cm2 under the condition of pH=8 and NaCl concentration was 0.5 M.The RC-RPC/IEC possessed the highest uptake of 22.6 μg/cm2 under the condition of pH=6.5.In addition,statistic desorption experiment displayed that the recovery of IgG were 72.3%and 79.6%under pH=4 and pH=9 without the addition of salt,respectively.And the recovery of a-CTP reached 84.2%when the acetonitrile volume fraction was 80%.The above results indicated that The ring-opening chemistry based on thiolactone is an effective protocol for bifunctional modification on the membrane surface.