CHO Cell Transfection
CHO cells have a well-earned reputation for being “difficult to transfect” compared to workhorses like HEK293. Compared to HEK293 cells, CHO cells have several challenges (explained further below) including thicker membranes.
Our team at EZ Biosystems has created a proprietary formulation for CHO cell transfection to increase the overall delivery efficiency of large plasmid, mRNA, siRNA, and other types of nucleic acids. Explore our CHO Cell Avalanche® Transfection Reagent and learn more about CHO cell transfection below.
The Challenges of CHO Cell Line Transfection
CHO cells have a well-earned reputation for being difficult to transfect compared to workhorses like HEK293. Compared to HEK293 cells, CHO cells have thicker membranes, are less permissive to DNA uptake, often require higher DNA amounts, and are sensitive to toxicity. Because of this, CHO transfection usually needs optimized reagent ratios, high-quality plasmid DNA, and cell-line-specific protocols.
Lower Uptake Efficiency (Membrane & Endocytosis Differences):
HEK293 cells are notoriously poorly adherent as they detach easily during media changes, washing steps, and even pipetting. HEK cells often grow in loosely attached clumps as well which reduces transfection uniformity.
Endosomal Escape:
After uptake, nucleic acids must escape the endosome before lysosomal degradation. CHO cells have more robust endolysosomal processing, meaning a higher fraction of cargo gets degraded before escape. This creates a major bottleneck especially for siRNA and mRNA, which need cytoplasmic access.
Innate Immune / Stress Responses and Higher Sensitivity to Toxicity
CHO cells mount stronger innate immune-like responses to exogenous nucleic acids than HEK293 or Sf9 because cationic lipids and polymers damage CHO membranes more easily. dsRNA transfection (common contaminant in siRNA preps or plasmid transcripts) can trigger PKR-mediated pathways, reducing translation.
CHO cells naturally trigger stronger stress responses. This can result in lower viability after transfection and lower protein yield even if DNA enters cells.
Chromatin & Silencing (Challenge for siRNA and sgRNA Transfection)
CHO cells are prone to transgene silencing via epigenetic mechanisms (DNA methylation, histone deacetylation) and position-effect variegation after random integration leads to highly variable expression across clones. siRNA and sgRNA delivery face additional silencing of the RNAi/CRISPR machinery itself in some CHO backgrounds.
Nuclear Envelope Barrier (Challenge for Plasmid DNA Transfection)
After entry, DNA must reach the nucleus, however CHO cells divide at a much slower rate compared to certain cells like HEK293. There are fewer mitotic windows where the nuclear envelope breaks down (which is the primary route for plasmid entry in non-viral transfection)
Cargo-Specific Challenges for CHO Cell Transfection
Researchers cannot easy change the gene delivery molecule they are working with, however understanding the unique challenges before the transfection process begins may shed light on understanding future problems as they arise.
| Molecule Type: | Challenge: |
|---|---|
| Plasmid DNA | Low mitotic uptake, nuclear barrier, silencing post-integration |
| siRNA | Endosomal degradation, off-target innate immune activation, rapid turnover |
| sgRNA | RNase sensitivity, poor cytoplasmic/nuclear delivery, CHO-specific Cas9 expression challenges |
| sgRNA + Cas9 RNP | RNP complexes are large and charged; CHO membranes resist uptake; electroporation often required |
| Large plasmids and CRISP payloads (>10kb) | Dramatically reduced efficiency vs. smaller constructs; compaction into lipoplexes is poor |
| mRNA | Innate immune sensing, rapid degradation, lower translation efficiency vs. HEK293 |
Our team has created a CHO cell transfection protocol for our CHO Cell Avalanche® Transfection Reagent. However if you are unsure about your transfection efficiency or have technical questions, contact our team.
Suspension CHO Cells Are Harder Than Adherent Cells to Transfect
Suspension-adapted CHO cells (like CHO-S cells or CHO-DG44 cells) are harder to transfect than adherent CHO cells mainly because of differences in their growth state, membrane properties, and cellular uptake pathways. Suspension CHO cells are optimized for large-scale bioreactor growth, not for efficient uptake of foreign nucleic acids. Switching suspension CHO to adherent is possible but slow and not guaranteed, and the resulting cells may not behave like traditional adherent CHO.
Transfection Efficiency: CHO vs. Other Cell Lines (HEK293, Jurkat, Sf9, HeLa)
HEK293 and HEK293T Cells:
HEK293 are arguably the easiest mammalian cells to transfect. Routine lipofection yields 70–90% efficiency in HEK293 vs. 20–50% in CHO under similar conditions. HEK293 divide faster, giving more mitotic windows for plasmid nuclear entry. But HEK293/HEKK293T cells may not be suitable for manufacturing due to oncogenic concerns and glycosylation differences. Interested in transfecting HEK293 cells? Try our HEK293 specific Avalanche transfection reagents.
Jurkat and Primary T Cells:
CHO cells are actually easier than primary immune cells. T cells are notoriously resistant to all non-viral methods. Both CHO cells and Jurkat cells typically require electroporation for reliable delivery. Interested in transfecting Jurkat or Primary Cells? Try our dedicated Avalanche transfection reagents for both those categories.
Sf9 Cells (Insect Cells):
Sf9 cells use baculovirus infection as the dominant delivery method. For plasmid transfection, Sf9 is actually quite easy with cationic lipid reagents. However, Sf9 lacks mammalian post-translational machinery, so they’re used for different applications. Interested in transfecting Sf9 cells? Try our Avalanche®-Everyday Transfection Reagent or Avalanche®-Omni Transfection Reagent.
HeLa Cells:
HeLa cells are similarly permissive to HEK293/HEK293T cells, heavily used for transfection optimization, and CHO cells are meaningfully harder than HeLa for all cargo types. Interested in transfecting HeLa cells? Try our Hela Cell Avalanche® Transfection Reagent or HEp-2 Cell Avalanche® Transfection Reagent if you are working with HeLa marker chromosomes.
Learn More About CHO Cell Avalanche® Transfection Reagent
Our proprietary formulation of lipids and polymers ensures the highest possible transfection efficiencies and viabilities for CHO cells. No other transfection reagents can match the efficiency, convenience, and gentleness of CHO Cell Avalanche® Transfection Reagent for transfection on CHO cells.
If you and your team have technical questions about our CHO Cell Avalanche® Transfection Reagent, need advice on optimizing your workflow, or have a question about our transfection protocol, contact our team anytime.
Interested in a sample of our proprietary transfection reagent? Request a sample!