New insights into the performance characteristics of the Planova-series hollow-fiber parvovirus filters using confocal and electron microscopy.

Virus filtration remains a critical step in the downstream process for the production of monoclonal antibodies and other mammalian cell-derived biotherapeutics. Recent studies have shown large differences in virus capture behavior of different virus filters, although the origin of these differences is still unclear. The objective of this study was to use confocal and scanning electron microscopy to directly evaluate the capture of virus-size nanoparticles in Planova 20N and BioEX hollow-fiber virus filters. Confocal images of fluorescent nanoparticles were quantified using ImageJ image processing software based on the measured fluorescence intensity of the labeled nanoparticles. Nanoparticle capture by the Planova BioEX was independent of transmembrane pressure from 10 to 45 psi. In contrast, the Planova 20N showed significant differences in nanoparticle capture profile at low pressure, consistent with literature data showing virus breakthrough under these conditions. Images obtained after a process interruption show significant migration of previously captured nanoparticles in the Planova 20N filters but not in the BioEX. These results provide important insights into the nature of virus capture in different virus filters and its dependence on the underlying structure of the virus filtration membranes.