Visualizing effects of protein fouling on capture profiles in the Planova BioEX and 20N virus filters

One of the challenges in applying virus filtration in bioprocessing is the high level of membrane fouling seen with many process streams. A number of previous studies have examined the nature of the resulting flux decline, but much less is known about the effect of protein fouling on the virus retention characteristics. The objective of this work was to use confocal and electron microscopy to evaluate changes in the capture of 20 nm nanoparticles, comparable in size to small parvovirus, within the depth of Planova^TM 20N and BioEX hollow fiber virus filters after fouling with serum IgG. Confocal images of fluorescently-labeled IgG showed protein capture throughout the virus filter, with the greatest intensity seen more than half-way through the depth of the filter. IgG fouling of the Planova^TM 20N led to clustering in nanoparticle capture, likely due to changes in the flow distribution through the filter. This effect was not seen with the BioEX membrane. Instead, IgG fouling shifted the location of the captured nanoparticles towards the inlet (lumen) surface of the filter. These results provide important insights into the effects of protein fouling on the flow and virus capture behaviour of these important hollow fiber virus filters.