Hydrophobic Membrane Adsorbers for Large-Scale Downstream Processing

Membranes fea- ture a more open structure than resins, so there is virtually no diffusion limita- tion, and as a result they offer many technical advantages that have been well described in the lit- erature.69 Several applications have been discussed for MAb purification. Because of the gen- erally high isoelec- tric points of MAbs, anion exchange (AEX) resins are typically used as a polishing step in a flow-through mode (i.e., the product does not bind while the trace impuri- ties such as DNA, viruses, endo- toxins, and host cell proteins are retained).10 Although the amount of impurities to bind is very low in such operations, conventional polishing scale-up leads to column oversizing because of the pressure and diffusion limitations associ- ated with conventional bead-based chromatography.