Viral Filtration Integrity: Validating the Gold Nanoparticle Test with the CTech™ SoloVPE® System

Viral filtration is a size-based removal method that uses a membrane to retain virus particles during the production of biological products while allowing the product to pass through the filter. Confirmation of filter integrity as part of in-process testing is critical to ensure filter effectiveness. The gold particle test (GPT) is one of the most common and effective ways to perform post-use integrity testing of Planova filters. GPT is used to confirm that there is no shift in pore size distribution after virus filtration. A gold particle solution matched to the Planova filter type (e.g., Planova filter, 20N) is passed through the filter. Ultraviolet–visible (UV-Vis) spectroscopy at A520, A526, and A530 is used throughout filtration to quantify the level of gold particles pre and post-filtration. These readings are then used to calculate virus removal capability as shown in Figure 2, where the acceptance criteria are set to φ < 1.40. Traditional UV-Vis methods rely on fixed-pathlength absorbance readings which can lead to assay error. Because of the high concentration of gold particles, each sample requires substantial serial dilution to be measured within the linear range of the instrument. This can produce up to 30% error in the optical density reading, which can call the validity of the method into question.

Viral Filtration Integrity: Validating the Gold Nanoparticle Test with the CTech™ SoloVPE® System