Isothermal droplet digital PCR method for quantification of CHO residual DNA

Biologics drug manufacturers need to show clearance of host cell DNA in the purified drug to alleviate safety concerns. Currently, sensitive methods of DNA quantification, like quantitative real-time PCR (qPCR) or digital PCR (dPCR) are used in different labs. We have developed an isothermal PCR method to detect Chinese Hamster Ovary (CHO) DNA and performed it in droplet digital PCR (ddPCR) format to make the method quantitative. In this novel approach the protein drug is directly added to the isothermal PCR reaction mix avoiding DNA extraction and related manipulations. Then nanoliter-sized droplets are generated, followed by incubation, and reading the fluorescence in each droplet. The method is simple and fast and can potentially be adapted to other dPCR systems.