February 15, 2015 (Vol. 35, No. 4)

Quality by Design Approaches and Polyethylene Film Development Advance New Bag Range

Growing adoption of single-use bags for the production of biopharmaceutical drugs raises new challenges, including consistent product quality, robust change management, and improved assurance of supply. In close collaboration with resin and film suppliers, Sartorius Stedim Biotech’s polymer scientists and biologists have followed a Quality by Design (QbD) program for the development of a completely new polyethylene film, thus assuring consistent performance of the new Flexsafe® bags for critical bioprocess applications.

Quality by Design Approach

The QbD approach, as described in the ICH guidelines1 ICH Q8, Q9, and Q10, ensures that the developed product will consistently meet the intended performance criteria (Table). These criteria have been defined in accordance with the customer’s applications, enabling safe and robust single-use bioprocessing.

Well-established and open supplier relationships, knowledge sharing, and risk-mitigation strategies are a prerequisite for selecting the appropriate raw materials. By establishing relevant specifications and controls, security of supply is achieved with long-term contracts covering both assurance of supply warranty and robust business continuity plan for critical raw materials and for the final single-use bags.

The resin and additive package and the processing parameters of the new polyethylene film were selected based on testing several raw materials and film compositions with the aim to identify the best physical and mechanical properties and the most consistent cell growth performance.2 The film specification was established to enable that Flexsafe bags are suitable and scalable for all upstream, downstream, and aseptic bioprocessing steps including cell culture, storage, shipping, mixing, freezing, and filling applications.

Figure 1. Graphical representation of full factorial experimental design to establish operating ranges of critical extrusion process parameters (extruder temperature, chill roll temperature, and output); L, M, and H represent low, middle, and high settings. Center point (CP) settings were performed in triplicate.6

Consistent Cell Growth

Together with strategic partners in the polymer and film industry, Sartorius Stedim Biotech was able to establish full control of state-of-the-art, polyethylene multilayer film formulation as well as traceability and control of polymers and additives used to make it. A multifactorial experimental-design approach has been used to determine operating ranges for the film extrusion of the Flexsafe bags (Figure 1).

Based on this material and biological science and process control approach, the new single-use bags can ensure excellent and reproducible growth behavior of the most sensitive cell lines (Figure 2). This has been confirmed by a recently published interlaboratory test3 in which a number of bioprocessing bags from different vendors was evaluated using a panel of different production cell lines and media.

Other authors have demonstrated the suitability of Flexsafe bags for mesenchymal stem cells.4 Controlling the complete manufacturing process—from resin to final bag—ensures consistent and reproducible quality of Flexsafe bioprocessing bags. This has been proven by lot-to lot consistency in cell-growth performance of this new multilayer polyethylene film.

Understanding and controlling the film formulation and manufacturing process are key prerequisites to establish meaningful and reliable extractable and leachable data as needed for toxicological assessment of intermediate and bulk drug substance storage and stability studies. All that combined with a robust assurance of supply concept guaranteeing uninterrupted supply of bioprocessing bags5 is absolutely crucial to pave the way toward fully single-use bioprocessing facilities of the future.

Figure 2. Influence of critical film extrusion process parameters on cell growth examined using a cell growth testing approach described by Jurkiewicz et al.2,6; error bars represent ± SEM. The numbers correlate with different experimental conditions of the factorial designs with 1a, 1b, and 1c representing the center point settings.

Enhanced Quality Assurance

A key aspect of quality assurance is working in collaboration with the manufacturers of the resins and additive packages used for the extrusion of the film. Working directly with the suppliers of raw materials and plastic resins is of paramount importance to establishing specifications, operating ranges, and process controls and obtaining full understanding and traceability of the initial resin and additive package used for making the film.

Second, a robust product quality proess necessitates complete understanding of the entire production process, the definition of the operating ranges, and the implementation of multiple controls to guarantee lot to lot consistency of the film, the bag and the final single-use bag assembly (Figure 3).

This comprehensive understanding of the entire process from the resin to the final product can only be achieved with strong collaborations between the single-use bag manufacturer, the raw material suppliers and the film manufacturer.

Knowing the formulation of the resins, the additives, and of the film extrusion process, it is possible to identify the critical process parameters influencing the critical quality attributes of the final product. This QbD approach helps develop more detailed resin specifications and provide consistent lot-to-lot film performance and desirable bag quality attributes such as cell growth performance, robustness, and extractable profiles.

Also knowing and controlling the detailed formulation of the various compounds that enter into the manufacture of our films enables the establishment of consistent and relevant extractable profiling, data reporting, and leachable validation data. Knowing what films are made of helps us interpret our extractable data in a very precise and accurate way.

Figure 3. Overall supply chain for single-use biprocessing bags


The material science and process understanding applied during development of SSB’s new polyethylene film, which was enabled by strategic partnerships in the polymer industry, were cornerstones to delivering the new Flexsafe range of bioprocessing bags. 

Elisabeth Vachette ([email protected]) is senior global manager for Flexel and Flexsafe, Lucie Delaunay is R&D project leader, Magali Barbaroux is director of film and material R&D, Gerhard Greller is R&D director of upstream technologies, Christel Fenge is vp of marketing for fermentation technologies, Heiko Hackel is vp of global sourcing, and Jean-Marc Cappia is vp of marketing for fluid management technologies at Sartorius Stedim Biotech. The authors wish to acknowledge Sartorius Stedim R&D teams in Aubagne, France, and Göttingen, Germany.

1. ICH (2009) Harmonized tripartite guideline, pharmaceutical development Q8(R2)  / ICH (2005) Harmonized tripartite guideline, quality risk management Q9 / ICH (2008) Harmonized tripartite guideline, pharmaceutical quality system Q10.
2. Jurkiewicz E, et al. Verification of a New Biocompatible Single-Use Film Formulation with Optimized Additive Content for Multiple Bioprocess Applications. Biotechnol. Progr. 30 May 2014; http://onlinelibrary.wiley.com/doi/10.1002/btpr.1934/full.
3. Eibl R, et al. Recommendation for Leachable Studies: Standardized Cell Culture Test for the Early Identification of Critical Films for CHO Cell Lines in Chemically Defined Culture Media. Dechema January 2014.
4. Imseng N, et al. Towards a Standardized Biological Test for the Identification of Cell Growth Influencing Leachables (poster). ESACT 2013: Lille, France, 23–26 June 2013.
5. Cappia JM, et al. Enhanced Assurance of Supply for Single-Use Bags: Based on Material Science, Quality By Design, and Partnership with Suppliers. BioProcess Int. 12(8) 2014: S43–S46.

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