Benchmarking of Sterilizing-Grade Filter Membranes with Liposome Filtration

Cytotoxic drugs can be encapsulated in liposomes vesicles, which act as drug delivery vehicles and reduce the risk of exposure of drug to healthy cells. The sterility of such liposome solutions is typically ensured using 0.2 μm–rated sterilizing-grade membranes, but due to the high viscosity and low surface tension of these formulations, they can cause premature blocking and increased risk of bacterial penetration through a 0.2 μm sterilizing-grade membrane. The low surface tension of liposome solutions affects the contact angle with membrane and reduces bubble point, leading to bacterial penetration through the membrane. This poses a great challenge to select an appropriate sterilizing-grade membrane for a given process and for filter manufacturers to develop a sterilizing-grade membrane that specifically addresses these needs. In this study, the influence of different variables that could affect the total throughput and bacterial retention performance of different membrane types on processing of liposome solutions was evaluated. Based on the results, we conclude that the membrane properties, for example, surface porosity, surface tension, pore size, symmetry/asymmetry, hydrophilicity and liposome properties (e.g., composition, lipid size, and concentration) affect bacterial retention and total throughput capacity. Process parameters such as temperature, pressure, and flow should also be optimized to improve process efficiency. LAY ABSTRACT: Cytotoxic drugs can be encapsulated in liposomes vesicles, which act as drug delivery vehicles and reduce the risk of exposure of drug to healthy cells. Liposome solution cause premature blocking and increased risk of bacterial penetration through a 0.2 μm sterilizing-grade membrane due to their high viscosity and low surface tension. In this study, we demonstrated the total throughput and bacterial retention performance of different sterilizing-grade membranes with liposome solution. Based on the results, we conclude that some sterilizing-grade membranes yield less throughput and bacterial retention compared to other membranes. This is due to liposome formulation and membrane properties. Therefore, it is important to identify the product formulation and membrane properties before selection of a suitable sterilizing-grade filter for a given process application to ensure expected throughput and bacterial retention.