Perspectives on sterile filter performance through insights obtained by membrane characterization methods

Sterile filtration is used to ensure the sterility of essentially all parenteral drug products. Although all commercial 0.2/0.22 μm rated sterile filters are validated to provide essentially complete retention of small bacteria, these membranes are made from a wide range of synthetic and natural polymers that can result in very different chemistries, morphologies, and pore size distributions. These can in turn have a significant effect on filter performance, including both product yield and filter capacity. This is particularly true when sterile filtration is used for larger biotherapeutics, e.g., viral vaccines, lipid nanoparticles, and nanoemulsions, in which the size of the drug product is very similar to that of the pore sizes within the sterile filter. This perspective provides a short overview of available techniques for evaluating key membrane properties in the context of sterile filtration and then examines how these characterization tools can provide important insights into sterile filter performance using experimental data for several example systems.