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Biopharmaceutical viral clearance: Easy on paper says Swedish team

By Gareth MacDonald+


"Compare it to a coffee filter paper but with tailored pore size distribution to stop viruses" Assoc. Prof Albert Mihranyan

Researchers are developing a cellulose filter paper they claim is at least as effective at removing viruses from biopharmaceutical production streams as currently available industrial systems.

The team from Uppsala University in Sweden created the filters from cellulose mass using a traditional paper production technique known as ‘heat pressing’ in combination with ‘trade secret’ annealing techniques to precisely control pore size and distribution.

In industry, the efficiency of a filtering technology is measured in terms of log reduction value (LRV) with an LRV of above six deemed sufficient to ensure the clearance of large viruses like influenza.

Associate Professor Albert Mihranyan from Uppsala University’s department of engineering told the new cellulose nano-fibre filter has an LRV of above six, meaning it can be used to remove viruses in the 80 – 120nm range.

Testing also indicates the filters can trap smaller particles according to Mihranyan, who said: “We were unable to detect model fluorophore tagged styrene latex particles (30 nm) either in the filtrate…so, there is strong evidence that this filter will work also for small viruses.”

Cost reduction

In addition to the potential performance advantages, the Swedish team also believes paper filters can cater for demand for lower cost filtration material which they expect to increase as the biopharmaceutical industry continues to expand globally.

Mihranyan said: “The need for inexpensive and robust virus removal filters is expected to grow in the future due to more protein based products anticipated to come in to use.”

He declined to compare the cost of a commercialised version of the paper filters with technologies on the market, but did  contrast them with the smaller 100nm filters used in laboratories that cost “hundreds of US dollars for a small pack of 10.”

Cellulose is generally a cheap resource and, because [with our technology] there is no need to dissolve it to make a hi-tech virus filter, chances are high that the material will be competitive” said Mihranyan.

 The research paper "A Size-Exclusion Nanocellulose Filter Paper for Virus Removal" was published in Advance Healthcare Materials and is available here

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