Evaluation of loading characteristics and IgG binding performance of Staphylococcal protein A on polypropylene capillary-channeled polymer fibers

The loading characteristics of recombinant Staphyloccocus aureus protein A (rSPA) on polypropylene (PP) capillary-channeled polymer (C-CP) fibers were investigated through breakthrough curves and frontal analysis. The dynamic adsorption data was fit to various isotherm models to assess the possible mode of rSPA-PP fiber adsorption. Among them, the Langmuir-linear model fit the experimental data best, suggesting a two-stage mechanism of adsorption. The first stage involves the formation of a monolayer coverage, which follows the Langmuir isotherm. When the adsorbate concentration increases, solute starts to adsorb onto the already adsorbed layer, following a linear adsorption response. The relationship between the rSPA loading and flow rate and column length was also investigated. These two parameters are related through the residence time of rSPA in the column. It was determined that loading at the flow rate of 0.5 mL min−1 (∼28 mm s−1) with a 1 × 10−5 M (0.5 mg mL−1) rSPA feed concentration on a 30-cm (0.762 mm i.d.) column could conveniently produce a reasonable binding capacity of rSPA on PP surface within only 6 min. Under those conditions, the rSPA binding at 50% breakthrough was found to be ∼2.1 mg g−1 fiber. Operation of the rSPA-modified columns across ten complete processing cycles using clean-in-place conditions (including urea, guanidine HCl, and NaOH) commonly used in the bioprocessing industry allows assessment of the robustness of the rSPA capture layers. In all cases, the robustness was quite good, with the relative responses providing insights to the rSPA/PP surface structure.