Lipid encapsulated therapeutic and prophylactic products are increasingly prevalent in medicines manufacturing, however these materials present several challenges during sterilizing grade filtration. In this study liposomes with an average diameter of 143 nm and a polydispersity index of 0.1 were filtered through multiple dual layer membranes made of polyethersulfone (PS), polyvinylidene fluoride (PVDF) or a combination of the two. The downstream filter in each case had a nominal retention rating of 200 nm that is standard for sterilizing grade filtration.<br/><br/>X-ray computed tomography was applied to image and measure the internal, porous structure of these membranes at a pixel size of 63 nm, to enable resolution of the internal pores of multiple PES and PVDF sterile grade filters with nominal retention ratings from 650 nm to 200 nm. Obtaining 3D geometries enabled network mapping that provided pore size distribution measurement and visualisation of pore connectivity and allowed for flow based simulations through these networks.<br/><br/>Confocal microscopy was used to identify the location of any liposome retained within the membrane following dual layer filtration across multiple differential pressures. Complementing the two imaging approaches allowed for both structural and liposome retention data to be obtained for comparison between PES and PVDF membranes.

Sterile filtration of liposomes: Operation design based on 3D imaging of flux decline

ACS Spring 2022

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