Concentrating on AAV Impurities With Ultrasensitive Total Protein Detection on Simple Western

Purity is a critical quality attribute (CQA) that must be monitored during AAV manufacturing. Impurities in protein products can be dangerous and impact efficacy. For example, protein impurities in final drug products may lead to undesirable immune responses in patients, so detecting total protein is critical for revealing impurities in preparative protein production. Traditional methods for total protein detection rely on SDS-PAGE with dyes like Coomassie Blue, or more sensitive stains like SYPRO Ruby and silver stain. However, SDS-PAGE requires large sample volumes, a lot of hands-on time, and it is poorly reproducible. Also, the use of staining dyes often comes with a lot of waste and can require specialized imaging equipment to which not every researcher has access. Here, we present a new workflow that enables total protein detection of AAVs on the Simple Western capillary electrophoresis-based immunoassay platform with a sensitivity that exceeds SYPRO Ruby. While SYPRO Ruby requires at least 1 ng of protein for reliable detection, Simple Western can reliably detect as little as 150 pg. These findings should enable researchers who are currently using SDS-PAGE to monitor purity to apply the automated platform and sensitivity improvements enabled by this workflow to assess AAV purity using smaller AAV sample sizes.