Characterisation of a generic monoclonal antibody harvesting system for adsorption of DNA by depth filters and various membranes

The physical parameters governing adsorption of DNA by various positively charged depth filters and membranes have been assessed. Buffers that reduced or neutralised the depth filter or membrane charge, and those that impeded hydrophobic interactions were shown to affect their operational capacity, demonstrating that DNA was adsorbed by a combination of electrostatic and hydrophobic interactions. The adsorption profile of DNA by a Sartobind Q anion exchange membrane showed immediate breakthrough, irrespective of challenge DNA concentration or flow rate, and in this case adsorption was by electrostatic interactions only. The production-scale removal of DNA from harvest broths containing therapeutic protein by partitioning of cells and debris from protein in sequential centrifugation and filtration steps, and the concentration of DNA in process supernatant were assessed. Centrifugation reduced the quantity of DNA in the process material from 79.8 mu g ml(-1) to 9.3 mu g ml(-1) whereas the concentration of DNA in the supernatant of pre- and post-filtration samples had only marginally reduced DNA content: from 6.3 to 6.0 mu g ml(-1) respectively. DNA was concentrated to 27.3 mu g ml(-1) along with monoclonal antibody in the ultrafiltration step. Similar effects were observed in the harvest step for a second antibody.