A Comparison of Convective-Based Alternatives to Packed Bed Affinity Chromatography for the Purification of Monoclonal Antibodies

Affinity chromatography with Protein A packed bed columns is the current standard for the primary capture of monoclonal antibodies. However traditional packed bead columns suffer from several limitations such as high pressure drop, slow mass transfer through the diffusive pores and strong dependence of the binding capacity on flow rate. One possible alternative to overcome these drawbacks is represented by convective media columns packed with membrane and monolithic materials. Complete affinity cycles have been performed using different innovative affinity membranes and monolithic columns that were characterized for adsorption of pure immunoglobulin G. The most promising materials were tested under a broad range of operating conditions to investigate the effects of operating parameters, like feed concentration and flow rate, on separation performance. Material selectivity was evaluated during the purification of IgG1 from a cell culture supernatant. A critical evaluation between the two convective media used as a support will be presented. However, to promote the application of convective materials in large scale processes, it is imperative to develop a reliable simulation tool able to describe the process performance in a predictive way. An effective model for the description of convective affinity chromatography processes will be presented. The model considers all the relevant mass transport and kinetic phenomena involved with convective media materials, namely axial convection, longitudinal dispersion in the micro-porous matrix and affinity binding, together with extra-column effects in terms of mixing volumes and delay time. The mathematical description takes into account all the different chromatographic steps: adsorption, washing and elution. Model validation has been performed by comparing simulation results with an extensive set of experimental data for both membranes and monolithic columns. Simulations reveal a good agreement with experimental data for all the chromatographic steps, both in the case of membranes and monoliths considered, demonstrating the model accuracy for the description of the transport phenomena in the column and the adsorption binding mechanism. Furthermore, a proper study of the model parameters for the two convective media is addressed, elucidating the main operative differences between the membrane and monolithic columns for protein affinity chromatography.