title: Protein adsorption to poly(ethylenimine)-modified Sepharose FF. IV. Dynamic adsorption and elution behaviors.
abstract: We have previously investigated bovine serum albumin (BSA) uptake to poly(ethylenimine) (PEI)-grafted Sepharose FF. It was found that there was a critical ionic capacity (cIC; 600mmol/L) for BSA, above which the protein adsorption capacity and uptake kinetics increased drastically. In this work, two poly(ethylenimine) (PEI)-grafted resins with IC values of 271mmol/L (FF-PEI-L270) and 683mmol/L (FF-PEI-L680), which were below and above the cIC, respectively, were chosen to investigate the breakthrough and linear gradient elution (LGE) behaviors of BSA. Commercially available anion exchanger, Q Sepharose FF, was used for comparison. The DBC values of FF-PEI-L680 were much higher in the entire residence time range (2-10min) than the other two resins due to its high static adsorption capacity and uptake kinetics. At a residence time of 5.0min, the DBC of FF-PEI-L680 (104mg/mL) was about seven times that of FF-PEI-L270 and three times that of Q Sepharose FF. A rise-fall trend of the DBCs with increasing ionic strength (IS) was found for all the three resins studied, indicating the presence of electrostatic exclusion for protein uptake at low IS. With increasing NaCl concentration from 20 to 200mmol/L, FF-PEI-L680 kept very high DBC values (64-114mg/mL). In addition, FF-PEI-L270 showed more favorable adsorption properties than Q Sepharose FF at 100-300mmol/L NaCl. These results proved that the three-dimensional grafting ion exchange layer on the PEI resins enhanced their tolerance to IS. In the study of LGE, the three resins showed similar elution behaviors and no distinct peak tailings were observed. The salt concentrations at the elution peaks (IR) were in the order of FF-PEI-L680>FF-PEI-L270>Q Sepharose FF, indicating that the elution for the PEI resins needed higher salt concentrations, which was also an appearance of the salt-tolerant feature of the PEI resins. When protein loading amount was increased to the value equivalent to the DBC at 10% breakthrough, the adsorbed BSA could be eluted at lower salt concentrations. The chromatographic study has provided new insights into the practical application of the PEI-based anion exchangers.
authors.affiliation: Department of Biochemical Engineering and Key Laboratory of Systems Bioengineering of Ministry of Education, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China.
authors.forename: Na
authors.initials: N
authors.lastname: Liu
authors.affiliation: Department of Biochemical Engineering and Key Laboratory of Systems Bioengineering of Ministry of Education, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China; Collaborative Innovation Center of Chemical Science and Engineering (Tianjin) , Tianjin 300072, China.
authors.forename: Lin-Ling
authors.initials: LL
authors.lastname: Yu
authors.affiliation: Department of Biochemical Engineering and Key Laboratory of Systems Bioengineering of Ministry of Education, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China; Collaborative Innovation Center of Chemical Science and Engineering (Tianjin) , Tianjin 300072, China. Electronic address: ysun@tju.edu.cn.
authors.forename: Yan
authors.initials: Y
authors.lastname: Sun
mesh_terms: D000327:Adsorption; D002853:Chromatography, Liquid / Q000379:methods*; D007700:Kinetics; D009994:Osmolar Concentration; D011094:Polyethyleneimine / Q000737:chemistry*; D012685:Sepharose / Q000737:chemistry*; D012710:Serum Albumin, Bovine / Q000737:chemistry*; D012965:Sodium Chloride / Q000737:chemistry
chemical_list: D012710:Serum Albumin, Bovine; D012965:Sodium Chloride; D011094:Polyethyleneimine; D012685:Sepharose
keywords: Dynamic binding capacity; Ion exchange chromatography; Ionic strength; Linear gradient elution.; Poly(ethylenimine); Residence time