Single-Use System Integrity II: Characterization of Liquid Leakage Mechanisms.

This study investigated the liquid leakage mechanism through microchannels in a flexible single-use packaging system composed of multilayer plastic film. Based on this study, a relationship between the maximum allowable leakage limit (MALL) and the loss of package integrity can be established under different use-case conditions. The MALL is defined as the greatest leak size that does not pose any risk to the product. A specifically designed liquid leak test was used to determine the leakage time, i.e., the time it takes for a package to show leakage. As a result, this method was able to determine the leak size for which no liquid leakage is observed after 30 days. This leak size varied between 2 µm and 10 µm and can be considered the MALL for liquid egress under different use-case conditions. This article also compared the MALL results of this liquid leak test with those of the microbial ingress test, showing a direct correlation between both tests. As test samples, an ethylene vinyl acetate multilayer film (300 µm thick) and a polyethylene multilayer film (400 µm thick) were cut into 50 mm patches. Before the patches were assembled in a filter holder to form a leak-tight seal, artificial leaks in sizes of 2 -25 µm were laser drilled into the center of each patch. The test units were filled aseptically with culture media and mounted vertically on the test setup. Various pressures were applied to each test unit to simulate the constraints that single-use systems may be subject to under real-world conditions. To detect the exact leakage time, electric circuits with timers were attached below each film patch. Microscopic investigations, including light microscopy and computed tomography, were used to interpret and understand the physics and geometries of the microchannels to explain any deviation from the expected results.

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.