Suspension Culture and Seed Train Considerations for Scale-Up | Corning

In the intricate world of biopharmaceuticals, suspension cell culture has emerged as a cornerstone technique for viral vector production. As gene therapies and vaccine development gain momentum, the thoughtful integration of suspension culture has become pivotal in addressing the complexities of production and scale-up. This blog post delves into the nuances of suspension culture, unraveling key considerations and strategies essential for successful viral vector production and seamless scale-up processes.

When it comes to developing and scaling up suspension cell culture processes like viral vector production, there are several important factors to consider. In addition to process parameters like media formulation or agitation, it's also important to have more theoretical considerations, like your plans for production at larger scales.

During the development stage, you will have flexibility as you engage in initial exploration and identify your critical process parameters; however, as you move toward manufacturing, certain aspects of your process will become more important, and are worth consideration up front. One of these aspects is your seed train; how will you get from a few million cells to several billion? Inherent to seed train is the scalability of the vessel you use; can you expect similar performance whether you're growing a few hundred milliliters versus several liters? Finally, once you are manufacturing at large scale and in a GMP environment, your process will require closed systems; as such, it's advantageous to familiarize yourself with these systems from an early stage.

R&D for Cell-Based Products

Initially, you start with small-scale testing and optimizing various conditions such as selecting the right cell line, formulating the media, adjusting pH and temperature, and ensuring proper oxygen levels. The goal is to create an efficient production workflow that determines critical process parameters and maximizes viral yields.

Working on a small scale allows you to try out different conditions without breaking the bank on flasks, media, and reagents. It's a cost-effective way to optimize things quickly, thanks to high-throughput optimization and the use of Design of Experiment (DoE) principles. Usually, this is carried out using open systems like Corning® Mini Bioreactors or Erlenmeyer Shake Flasks.

Scaling Up and Seed Train Optimization

As you move on to larger volumes or scale up the production, it's important to consider the final scale and ideally stick to the same technology to maintain consistency. For example, if you're dealing with volumes below 5 L, Erlenmeyer flasks or spinner flasks might do the trick. But if you need to go beyond that, rocking bioreactors can handle up to 50 L, and for even larger volumes, stirred tank reactors should be considered.

When it comes to cell-based products, we're talking about manufacturing on a massive scale, involving billions or even trillions of cells. Once you've completed the initial development and optimization studies, the next step is to generate enough cells for the final manufacturing stage. This requires a seed train, where the culture volume gradually increases from small vessels to potentially large production bioreactors. Optimizing the seed train can be an expensive and time-consuming process. Conditions for cell growth may differ at each scale, which means adapting the process parameters. Even if you've optimized everything at a small scale, scaling up requires some adjustments and potentially re-optimizing previously targeted parameters. For example, how you mix a liquid culture in an Erlenmeyer flask is different from a stirred tank bioreactor or a spinner flask. Oxygenation through different impeller or shaker speeds can impact cell growth, and as the volume increases, further optimization of transfection protocols may be needed.

Suspension Workflow

Product and Process Safety Considerations

Scaling up also means prioritizing safety. Products for cell and gene therapy, biotherapeutics, and vaccines must be manufactured under GMP standards. Ensuring product protection from contamination and operator safety is critical. When it comes to scaling up viral vector production, biohazard containment becomes essential for both operator protection and GMP compliance.

While small-scale flexibility for initial R&D is usually achieved through an open system approach, producing viruses for gene therapy and vaccines often requires higher biosafety standards like biosafety level 2 lab conditions (BSL2), especially for large product volumes. That's where transitioning to a closed system for seed train solutions comes into play.

Closed System Solutions for Suspension Cell Culture

Switching to a closed system is relatively straightforward, and many manufacturers offer convenient solutions. For instance, Corning's bioprocess portfolio includes preassembled closed system options like Erlenmeyer flasks and spinner flasks with aseptic transfer caps and tubing. You can easily connect them using Luer lock or MPC connectors or by tube welding. Plus, you have the flexibility to customize configurations, such as adapter or tubing length, to suit your specific needs.

Furthermore, Corning's closed system portfolio also includes centrifuge tubes (50 and 500 mL), storage bottles, and collection bags, along with preassembled closed system accessories. This comprehensive range of solutions allows for a seamless implementation of closed systems at every scale, from small shaker flasks or spinner flasks to larger rocking bioreactors or stirred tank bioreactors (STR). You can transfer liquids between vessels effortlessly using sterile, ready-to-use, preassembled solutions.

For processes that don't require much mixing, you can rely on Corning® Cell Expansion Bags. They provide an easy solution for scaling up from 500 mL to 5 L. The entire bag film allows efficient exchange of essential gases like oxygen and carbon dioxide, and they come as sterile, ready-to-use consumables with closed system adapters for liquid transfer and sampling.

With proper planning and the right products, you can strike a balance between flexibility to test multiple conditions during optimization and the need for biohazard containment when scaling up viral vector production.