Adherent and suspension cell culture

Key differences in cultivating adherent vs. suspension cells for biomanufacturing

In cell culture, two primary growth methods exist: adherent culture and suspension culture. The choice between these methods depends on cell type, application, and scalability needs. While adherent cells require attachment to a surface for growth, suspension cells freely float in liquid media. Each approach has its unique advantages, limitations, and specific cultivation requirements. Understanding these differences is crucial for optimizing bioprocessing, biomanufacturing, and therapeutic development.

What is adherent cell culture?

Adherent cell culture involves cells that must attach to a surface to grow and proliferate. This requirement is characteristic of cells derived from tissues that naturally depend on anchorage, such as epithelial, fibroblast, and endothelial cells. These cells attach to specialized surfaces such as treated plastic, glass, or extracellular matrix coatings to receive signals necessary for their survival and function.

In laboratory and industrial applications, adherent cell cultures are commonly used for regenerative medicine, cancer research, and tissue engineering. Their behavior closely resembles in vivo conditions, making them ideal for studies that require cell-to-cell interactions and structured growth. However, because these cells need a surface to attach to, scaling up production can be challenging, requiring large surface areas or microcarrier-based systems to expand cell numbers efficiently.

Cultivation of adherent cells is typically performed in T-flasks, multi-layered cell stacks, fixed-bed bioreactors, or microcarrier-based stirred-tank bioreactors. Each system can support either 2D or 3D cultivation approaches, depending on the process goals and cell type requirements. One of the main challenges in adherent culture remains scalability. Expanding adherent cultures to larger volumes often requires additional handling, enzymatic detachment for ell passaging, and increased surface area, which can make large-scale production labor-intensive and costly.

What is suspension cell culture?

Suspension cell culture, in contrast, involves cells that grow freely in a liquid medium without the need for attachment to a solid surface. This method is ideal for cells that naturally exist as single-cell suspensions, such as blood and immune cells, and certain tumor cell lines. Many industrial cell lines used in biopharmaceutical production, such as Chinese Hamster Ovary (CHO) cells and HEK293 cells, have been adapted to grow in suspension to facilitate large-scale biomanufacturing (1-2).

Because suspension cultures do not require a growth surface, they offer significant advantages in terms of scalability. Large volumes of cells can be expanded more efficiently using stirred-tank bioreactors, wave bioreactors, and perfusion systems. These bioreactor systems provide better control over key parameters such as oxygenation, pH, and nutrient distribution, ensuring consistent growth and productivity (3).

Despite these advantages, not all cell types can be easily transitioned into suspension culture. Some cells require adaptation, which can involve gradual passaging in suspension-friendly media or genetic modifications. Additionally, suspension cultures are more susceptible to shear stress from mixing and agitation, requiring careful optimization of bioreactor conditions to maintain cell viability (4).

Transitioning from adherent to suspension culture

Some cell lines originally adapted to adherent growth can be transitioned to suspension culture for improved scalability. However, this process presents challenges (5):

1. Cell Adaptation Time – Some adherent cells take multiple passages to adjust to suspension conditions and to build a stable suspension cell line

2. Media Optimization – Specific formulations are required to support cell survival and proliferation.

3. Shear Stress Sensitivity – Cells must acclimate to mixing conditions in bioreactors.

4. Morphological & Functional Changes – Some cells exhibit altered characteristics when cultured in suspension, making them no more eligible for therapy production

   
   

To mitigate these issues, researchers use gradual adaption protocols, serum-free and adapted media formulations as well as cultivation systems with low shear stress to minimize the impact of the cultivation method on the cell viability and functionality.

Both adherent and suspension cell cultures have critical roles in biotechnology, cell therapy, and biopharmaceutical production. While adherent cultures provide a more in vivo-like environment, suspension cultures enable greater scalability for commercial manufacturing (3). The choice between these methods depends on cell type, application, and production needs. Understanding their differences and potential transition strategies is essential for optimizing bioprocess efficiency and therapeutic development.

Why cells for Cell and Gene therapies rely on adherent cell culture processes.

In the field of cell and gene therapies (CGTs), a significant proportion of cell-based treatments rely on stem cells, which are inherently anchorage-dependent. Mesenchymal stem cells (MSCs), induced pluripotent stem cells (iPSCs), and other progenitor cells require adherent culture conditions to maintain their differentiation potential and therapeutic functionality (5). Since these cells cannot naturally grow in suspension, manufacturing processes for CGTs often rely on large-scale adherent culture systems, such as multi-layered cell stacks, fixed-bed bioreactors, or microcarrier-based stirred-tank bioreactors. The inherent need for adherence makes suspension culture a less viable option for many CGT applications, posing additional challenges in process scalability and automation. Developing scalable solutions for adherent cells remains a key focus in advancing CGT manufacturing.

References

(1) Pereira M, CHO in biomanufacturing: Past, present and future, June 1 2021, European Pharmaceutical Manufacturer, available from https://pharmaceuticalmanufacturer.media/pharmaceutical-industry-insights/biopharma-news/cho-in-biomanufacturing-past-present-and-future/

(2) Abaandou L, Quan D, Shiloach J. Affecting HEK293 Cell Growth and Production Performance by Modifying the Expression of Specific Genes. Cells. 2021 Jul 2;10(7):1667. doi: 10.3390/cells10071667. PMID: 34359846; PMCID: PMC8304725.

(3) Cell Culture Company, Bioreactor Cell Culture: A Key to Advancing Biotech Research, January 27, 2025, available from: https://cellculturecompany.com/bioreactor-cell-culture-a-key-to-advancing-biotech-research/

(4) Eaker S, Abraham E, Allickson J et al. Bioreactors for cell therapies: current status and future advances. Cytotherapy (2017) 19: 9–18.

(5) Bellani CF, Ajeian J, Duffy L, Miotto M, Groenewegen L, Connon CJ. Scale-Up Technologies for the Manufacture of Adherent Cells. Frontiers in Nutrition [Internet]. 2020 Nov 4;7. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7672005/