Flexural fatigue behavior of rocking bioreactor films

The fields of biopharmaceutical processing and cell therapy are adopting single-use, closed systems throughout their workflows to enhance sterility, minimize waste wash effluent and enable manufacturing flexibility compared to traditional stainless steel bioreactors. One of the key single-use technologies in use is the rocking bioreactor, comprising a polymer film bag (outfitted with ports and sensors) mounted to a tray capable of mixing the contents of the bag and a control system (controlling temperature, agitation, and potentially media perfusion). One of the challenges encountered in rocking bioreactor bags is the fact that upon inflation/filling with media, the originally flat bioreactor bags often develop folds and dimples due to their inflated geometry. These deformations tend to be inconsequential at small volumes and low agitation rates/times, but can lead to flex fatigue failures such as whitening, delamination and through-cracking under more extreme conditions. In practice, these failures are dependent on a number of factors including bag material and volume, mounting geometry, rocking angle and rate, and the duration of culture, making a systematic study of the material properties controlling this behavior difficult and time-consuming. Several flex fatigue testing systems exist in the literature, including Gelbo and Sonntag-Universal, but none of these effectively model the unique geometry and stresses of the rocking bioreactor geometry. To this end, we have developed accelerated test methods to analyze the flexural fatigue behavior of multilayer rocking bioreactor films. These methods enable quality control testing of film lots, and have the potential to compare different film compositions with a rapid and reproducible test, thereby facilitating development of new films. Our test method models the local geometry surrounding the fold/dimple in a rocking bioreactor in a small sample of film, and cycles the sample to accelerate flexural fatigue at the dimple site. Initial results indicate the ability to accelerate film failure from tens of days on a rocking bioreactor platform (using a full bioreactor bag) to tens of hours using less than ten square inches of film. We will discuss the effects of various experimental parameters on film failure, optimization of test procedures and correlation with rocking bioreactor testing in the field

Test method development for next-generation bioprocessing applications

As single use disposable (SUD) bioprocessing systems become more commonplace, the range of applications and workflow steps served by single use continues to grow. Nearly all of the process steps and techniques currently used in bioprocessing were developed on stainless steel or glass vessels which exhibit thermal, chemical and mechanical properties which differ greatly from the polymer films used in SUD. While in many cases (e.g., cell culture) these differences have negligible effects on performance, as the industry pushes the limits of intensification and increases in the breadth of SUD applications (antibody-drug conjugation – ADC, microbial culture, etc.) single-use materials and systems face new challenges. This highlights the need for testing capabilities to qualify and develop new SUD materials, components and systems to ensure integrity, cleanliness and performance. In this presentation, we will comment on the current state-of-the-art in standardized testing as well as highlighting several small-scale test methods developed internally, specifically for testing materials for SUD bioprocessing. In order to assess film and component (e.g., port, tubing) capabilities for the full range of current and foreseeable process steps, we have developed/adapted/adopted test methodologies to model environments experienced both in conventional use (abrasion, flexure, pressurization), as well as challenging new use cases including high and low temperature extremes (freezing, pasteurization) and aggressive, non-aqueous environments used in bioconjugate chemistry (e.g., ADC, conjugate vaccines), chemical viral inactivation and non-traditional cell culture (e.g., microbial). For each of these applications, our methods were developed based on generating an understanding of the environment in which the chosen SUD system is to be used, identifying the primary failure modes that are (or could be) encountered in use and reducing these risks to their fundamental physics to generate small-scale tests that can be performed rapidly on small samples of material. These test methods allow for rapid screening of film and component materials to reduce risks in new applications prior to prototype development and assess product and process quality in the long ter