Modification of poly(glycidyl methacrylate–divinylbenzene) porous microspheres with polyethylene glycol and their adsorption property of protein

Rigid porous poly(glycidyl methacrylate–divinylbenzene) (P(GMA–DVB)) microspheres were synthesized through suspension polymerization with a mixture of isooctane and 4-methyl-2-pentonal as the porogen. The microspheres were intended to use as column packing materials for protein separation. However, irreversible adsorption of protein was found on the polymer microsphere. To circumvent the problem, polyethylene glycol (PEG) was coupled to the microspheres. The coupling reaction took place between the hydroxyl group of PEG and the epoxy group of the P(GMA–DVB) solid medium in the presence of boron trifluoride. The density of PEG immobilized onto the P(GMA–DVB) can be determined easily by saponification of modified microsphere firstly and then titration of glycerol–PEG. The effect of the cross-linker content of microsphere on the density of PEG immobilization was investigated. Molecular weight of PEG was found to influence the PEG-immobilization density, which subsequently affects the hydrophilicity of the modified P(GMA–DVB). Bovine serum albumin (BSA) and trypsin were used as model proteins to examine the adsorption and desorption properties of the modified P(GMA–DVB) microspheres. The results demonstrated that P(GMA–DVB) porous microsphere with 20% DVB and modified with PEG4000 showed excellent adsorption and desorption properties. Adsorption capacity of BSA on the modified microsphere attained to 51.6 mg/g microsphere, and BSA mass recovery and trypsin activity recovery was up to 97.6% and 98.7%, respectively. The modified microsphere was demonstrated to be a promising hydrophobic interaction chromatography material for purification of protein.