The Development of a Microbial Challenge Test with Acholeplasma laidlawii To Rate Mycoplasma-Retentive Filters by Filter Manufacturers

Comparative Evaluation of the Performance of Sterile Filters for Bioburden Protection and Final Fill in Biopharmaceutical Processes

Sterile filtration processes are widely used in the production of biotherapeutics for microorganism removal and product sterility. Sterile filtration processes can be applied to buffer preparation and cell culture media preparation in biotherapeutics processes, and to final sterilization or final filling in downstream processes. Owing to their broad range of applications in bioprocessing, various 0.2/0.22 μm sterile filters with different polymer materials (i.e., hydrophilic PVDF and PES) and nominal pore sizes are commercially available. The objective of this study was to evaluate two different commercial sterile filters in terms of filtration performance in various sterile filtration processes of biopharmaceutical production. The results demonstrate the importance of choosing the appropriate filter considering the process type and target removal/transport product to ensure efficient sterile filtration in the production of biotherapeutics.

Soft synthetic microgels as mimics of mycoplasma

Artificial model colloids are of special interest in the development of advanced sterile filters, as they are able to efficiently separate pleomorphic, highly deformable and infectious bacteria such as mycoplasma, which, until now, has been considered rather challenging and laborious. This study presents a full range of different soft to super soft synthetic polymeric microgels, including two types with similar hydrodynamic mean diameter, i.e., 180 nm, and zeta potential, i.e., -25 ± 10 mV, but different deformability, synthesized by inverse miniemulsion terpolymerization of acrylamide, sodium acrylate and N,N'-methylenebisacrylamide. These microgels were characterized by means of dynamic, electrophoretic and static light scattering techniques. In addition, the deformability of the colloids was investigated by filter cake compressibility studies during ultrafiltration in dead-end mode, analogously to a study of real mycoplasma, i.e., Acholeplasma laidlawii, to allow for a direct comparison. The results indicate that the variation of the synthesis parameters, i.e., crosslinker content, polymeric solid content and content of sodium acrylate, has a significant impact on the swelling behavior of the microgels in aqueous solution as well as on their deformability under filtration conditions. A higher density of chemical crosslinking points results in less swollen and more rigid microgels. Furthermore, these parameters determine electrokinetic properties of the more or less permeable colloids. Overall, it is shown that these soft synthetic microgels can be obtained with tailor-made properties, covering the size of smallest species of and otherwise similar to real mycoplasma. This is a relevant first step towards the future use of synthetic microgels as mimics for mycoplasma.

Pre-Plated Cell Lines for ADMETox Applications in the Pharmaceutical Industry

Membrane transporters significantly modulate membrane permeability of endobiotics and xenobiotics, such as bile acids and drugs, respectively. Various in vitro methods have been established for both ATP-binding cassette (ABC) transporters to examine cellular efflux and uptake, and for solute carriers (SLC) to examine cellular uptake of substrates. Cell-based systems are the models of choice to test drug-transporter interactions as well as drug-drug interactions for research and regulatory purposes, albeit, for low passive permeability substrates of ABC transporters, vesicular uptake assays are also recommended. Commercially available pre-plated cells (e.g., immortalized or transfected) offer a useful alternative to in-house cell culture. Three main methods are known to manufacture pre-plated cultures: regular culture medium with vacuum seal, cryopreserved delivery, and the solid shipping media technology. The regular culture medium and the solid shipping media technologies provide ready-to-use models for end users. Models expressing a broad selection of transporters are available in pre-plated formats for absorption, distribution, metabolism, excretion, and toxicity (ADMETox) studies. Conversely, the application and utility of pre-plated cultures coupled with personal experiences have not been extensively covered in published research papers or reviews, despite availability and significant use of pre-plated products in the pharmaceutical industry. In this overview, we will briefly describe: 1) in vitro tools commonly used for ADMETox testing; 2) methods employed in manufacturing, shipment and preparation of pre-plated cell lines; 3) cell-membrane barrier models currently available in pre-plated format to reproduce passage restriction of physiological barriers to certain compounds; and 4) recommended pre-plated cell lines overexpressing uptake transporters for ADMETox applications.