Plasmid DNA pre-purification by tangential flow filtration

The growing demand of plasmid DNA for gene therapy and third generation vaccines has encouraged the development of simple, robust and scalable production bioprocesses. Bearing in mind the purification step, the membrane separation processes may be a viable and cost-effective option that may be used without compromising the plasmid integrity. In this work, an operation of tangential flow ultrafiltration in a hollow-fiber module was used for the pre-purification of plasmid pVAX1-NH36 from clarified lysates of Escherichia coli DH5α culture. The ultrafiltration system was characterized using model solutions to determine the membrane resistance, plasmid concentration on the membrane wall and the system masstransfer coefficient. In the analysis, a model based on Darcy’s law and the stagnant film layer was used. These results allowed to estimate an optimal flux of 0.0016 cm/s and an optimal bulk concentration for the diafiltration process of 5.50 μg/mL. The concentration of lysates containing the plasmid of interest was performed by constant flow in batch mode achieving a 41% of impurities removal. These results suggest the use of a combination of concentration–diafiltration steps for the pre-purification of the plasmid lysates processed. The electrophoretic and high-performance liquid chromatography by hydrophobic interaction analysis showed that the plasmid supercoiled isoform maintained its integrity and no appreciable plasmid loss was present.