The efficiency of virus filtration in gases is an area where the generation of accurate and representative data is difficult to replicate. Process filters to remove viruses and bacteria from gas streams are generally in the range of 0.2µm; an order of magnitude larger than many viruses. The adsorption and Brownian motion mechanisms of filtration allow a high retention of small particles in gases, and thus most viruses can be retained by current process filters. The Parenteral Drug Association1recommends that sterile gas filtration is carried out with filters that have been validated to remove bacteria in liquids; such PTFE membrane filters are also known to effectively remove coliphage viruses of 25nm in size and even particles of 3nm. Depth filters incorporating glassfibre media are also able to retain viruses in gases, albeit with a risk of breakthrough if the filter becomes wet. In recent years, research has focussed on ascertaining the virus retention efficiency of HEPA filters manufactured with polymeric nanofibre media.
Current methods to assess virus retention using surrogates are based on the retention of oil droplets and sodium particles; neither resembles the surface characteristics of viruses, which are critical to the efficiency of separation.
The use of protein nanoparticles as a surrogate is a practical and reproducible tool that challenges filters with particles that closely replicate the properties of viruses. Braas et. al., 20002 have shown, how such particles show a similar behaviour to adenovirus in aqueous phase, liquid-liquid separations and ion-exchange chromatography; this is indicative of similar surface properties and thereby adsorption characteristics to filter media. The aim of the current project is to explore the application of suitable surrogates based on protein nanoparticles to test the retention of viruses, with the surface properties of the chosen challenge particles taken into account...
Session: G16 - Particles for Filter Testing
Day: 24 October 2019
Time: 13:00 - 14:15 h