Department of Chemical Engineering, University of Virginia, Charlottesville, VA 22904-4741, USA.
J Chromatogr A. 2009 Nov 20;1216(47):8339-47. doi: 10.1016/j.chroma.2009.09.017. Epub 2009 Sep 11.
Experimental determination and modeling of IgG binding on a new protein A adsorbent based on a macroporous resin were performed. The new adsorbent consists of polymeric beads based on hydrophilic acrylamido and vinyl monomers with a pore structure optimized to allow favorable interactions of IgG with recombinant protein A coupled to the resin. The particles have average diameter of 57 microm and a narrow particle size distribution. The IgG adsorption equilibrium capacity is 46 mg/cm(3) and the effective pore diffusivity determined from pulse response experiments for non-binding conditions is 8.0 x 10(-8) cm(2)/s. The IgG adsorption kinetics can be described with the same effective diffusivity by taking into account a heterogeneous binding mechanism with fast binding sites, for which adsorption is completely diffusion controlled, and slow binding sites for which adsorption is controlled by the binding kinetics. As a result of this mechanism, the breakthrough curve exhibits a tailing behavior, which appears to be associated with the slow binding sites. A detailed rate model taking into account intraparticle diffusion and binding kinetics is developed and is found capable of predicting both batch adsorption and breakthrough behavior over an ample range of experimental conditions. The corresponding effective diffusivity is independent of protein concentration in solution over the range 0.2-2 mg/cm(3) and of protein binding as a result of the large pore size of the support matrix. Overall, the small particle size and low diffusional hindrance allow capture of IgG with short residence times while attaining substantial dynamic binding capacities.
基于大孔树脂的新型蛋白 A 吸附剂上 IgG 结合的实验测定和建模。新型吸附剂由亲水性丙烯酰胺和乙烯单体聚合珠粒组成，其孔结构经过优化，可使 IgG 与偶联到树脂上的重组蛋白 A 之间产生有利的相互作用。这些颗粒的平均直径为 57 微米，且粒径分布较窄。IgG 的吸附平衡容量为 46mg/cm(3)，非结合条件下通过脉冲响应实验确定的有效孔扩散系数为 8.0×10(-8)cm(2)/s。通过考虑具有快速结合位点的非均相结合机制，可以用相同的有效扩散系数来描述 IgG 的吸附动力学，其中快速结合位点的吸附完全受扩散控制，而慢速结合位点的吸附受结合动力学控制。由于这种机制，穿透曲线表现出尾部行为，这似乎与慢速结合位点有关。考虑到颗粒内扩散和结合动力学，开发了一个详细的速率模型，该模型能够预测在广泛的实验条件下的批处理吸附和穿透行为。相应的有效扩散系数与溶液中蛋白质浓度（0.2-2mg/cm(3)）无关，并且由于支撑基质的大孔径，也不受蛋白质结合的影响。总的来说，小颗粒尺寸和低扩散阻力允许在短停留时间内捕获 IgG，同时实现较大的动态结合容量。
