Expi293™ Expression System Kit - FAQs

Most 293 cell lines can be adapted directly from conventional serum-containing or other serum-free media into Expi293 Expression Medium by either using the Direct Adaptation method or Sequential Adaptation method, described in the manual.

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Please refer to the Application Note (http://www.thermofisher.com/content/dam/LifeTech/global/life-sciences/CellCultureandTransfection/pdfs/Expi293Adaption-MembraneProTech_AppNoteGlobal_FHR.pdf) for a protocol for adapting the MembranePro kit for use with the Expi293 System.

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Please see the Application Note (http://www.thermofisher.com/content/dam/LifeTech/migration/files/proteins-expression-isolation-analysis/pdfs.par.0358.file.dat/PG1391-PJ6257-CO28716-Expi293-10L-Wave-Bag-App-Note-Global_FHR.pdf) for a method for the adaptation of the Expi293 Expression System for use in the WAVE Bioreactor System.

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Yes, see the Application Note (http://www.thermofisher.com/content/dam/LifeTech/migration/files/proteins-expression-isolation-analysis/pdfs.par.28891.file.dat/expi293-microtiter-plates-co25793.pdf) on using 96-well microtiter plates with the Expi293 Expression System.

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Please refer to the Application Note for tips on optimizing protein yield using the Expi293 Expression System (http://www.thermofisher.com/content/dam/LifeTech/migration/files/proteins-expression-isolation-analysis/pdfs.par.61153.file.dat/expi293-protein-yield-co25763.pdf).

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We recommend cloning the heavy and light chain subunits separately into the pcDNA3.4 TOPO vector and then optimizing the ratios of the 2 plasmids. Each antibody needs to have the ratio of heavy to light chain adjusted for optimal antibody expression. Having the chains on separate plasmids makes this easier. Using the same plasmid will also ensure equal levels of expression of each subunit to start with.

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Our in-house scientists have cultured a 1 L volume in a 3 L baffled shake flask at 80-85 rpm. This was done using an Innova shaker with a 0.75-inch orbital throw.

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In the manual, we have provided optimal shake speeds for various formats. For most flasks, there would be a drop-off in expression when you go too fast or too slow because of cell shear stress or insufficient aeration. The effect is sharper in plates, where there is a sharper transition between static and moving fluid in wells.

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This depends on the flask, but a general rule of thumb is to use one quarter the volume of the flask.

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No. The Expi293 Expression System is designed to run without media exchanges. There is no need to remove transfection complexes or to change growth medium following transfection.

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The best transfection efficiencies are obtained when transfection complexes are used fresh. However, they should be stable for at least an hour.

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The growth and expression characteristics of Expi293F cells are such that, by 7 days post-transfection, the culture medium should be close to being spent and maximal protein expression should have already been achieved. Continued incubation will result in a large decrease in cell culture viability.

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The optimal expression time will be different for each protein, but most tested proteins fall within a 3-7 day window. As the system scales well, it is recommended you run a small-scale pilot experiment to determine when to harvest your protein of interest prior to scaling up.

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While the Expi293 Expression Medium can support much higher cell densities, we do not recommend growing your Expi293F cultures beyond 5-6 x 10e6 cells/mL, as subsequent transfection and protein expression efficiencies may be reduced. At higher densities, there is also the increased possibility of reaching the point of reduced culture viability. If your seed culture does exceed 5-6 x 10e6 cells/mL, passage them once or twice as detailed in the manual, monitoring them for viability and growth rate. Perform a test transfection using the Protein Expression Control IgG or an expression construct of known yield to determine if cell expression performance has been impacted.

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Other 293 cell lines may be used with the Expi293 Expression System. However, before these cell lines may be used for transfection studies, they must be adapted to serum-free, suspension culture in Expi293 Expression Medium and evaluated for transfection and expression.

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We recommend using the pcDNA 3.4-TOPO TA vector (Cat. No. A14697). This vector contains the native, full-length CMV promoter and a WPRE (Woodchuck Posttranscriptional Regulatory Element) downstream of the cloning site, both of which contribute to high level gene expression (about 2-3 fold higher expression than with pcDNA3.3 TOPO vector, which in turn provides 2-5 fold higher expression than with a standard pcDNA vector). Of course, the expression level is also protein-dependent.

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All the components of the system are animal-origin free except for the Opti-MEM I Reduced Serum Medium that is serum-free but not animal-origin free. Please see the Application Note for using the Expi293 Expression System under animal origin-free conditions:
http://www.thermofisher.com/content/dam/LifeTech/migration/files/proteins-expression-isolation-analysis/pdfs.par.5943.file.dat/expi-293-animal-origin-free-co25751.pdf

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For stable high-yield expression, we offer the Freedom CHO-S and Freedom DG44 kits. For transient high-yield expression, we offer the ExpiCHO Expression System, Expi293 Expression System, FreeStyle 293 Expression System, FreeStyle Max 293 Expression System, and FreeStyle Max CHO Expression System. For high-yield expression of functional membrane proteins in Exp293F cells, we offer the Expi293 MembranePro Expression System (Cat. Nos. A25869, A25870) that combines the scalability and ease of use of Expi293 and the technology of MembranePro to allow an increase of more than 20-fold in membrane protein yield compared to the standard, adherent culture MembranePro Functional Protein Expression System. Please see the Application Note (http://www.thermofisher.com/content/dam/LifeTech/global/life-sciences/ProteinExpressionAnalysis/pdfs/PG1391-PJ6257-CO28704-Expi293Adaption-MembraneProTech_AppNoteGlobal-FHR.pdf) for more details.

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You can have Anti-Clumping Agent and Pluronic F-68 in the medium while growing Expi293 cells. You need to remove Anti-Clumping Agent at least 2 passages prior to transfection of Expi293 cells because it interferes with transfection. You can add it back to the medium after transfection. Pluoronic F-68 can be present during transfection as it does not interfere with transfection.

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The formation of intact IgG molecules may be quantified using a sandwich ELISA designed to capture and detect rabbit IgG. Besides the rabbit IgG positive control vector, reagents, and consumables that are included in the kit, you will also need purified rabbit IgG to be used as a standard, F(ab')2-Goat anti-Rabbit IgG (H+L) Cross-Adsorbed Secondary Antibody, HRP (Cat. No. A10547), Protein A Coated Plates, Clear, 96-Well (Cat. No. 15130), TMB Substrate Kit (Cat. No. 34021), SuperBlock (TBS) Blocking Buffer (Cat. No. 37535), and PBS or TBS buffer for washes. There is an example procedure in our Protein A Coated Plates manual (https://tools.thermofisher.com/content/sfs/manuals/MAN0011310_Thermo Scientific_ProteinA_G_AG_Coat_96Well_UG.pdf). Please note that our R&D scientists determine titer values from crude cell culture supernatants using a Pall Life Sciences FortéBio Octet instrument equipped with a Protein A biosensor.

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We offer pRABBIT IgG IRES-EmGFP Positive Control Vector, Cat. No. A39243, which you can use to monitor your transfection and expression.

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No. The Expi293 Expression System is designed to run without media changes. There is no need to remove transfection complexes or to change growth medium following transfection.

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The Enhancers are designed to work together for maximal expression. Addition of just one Enhancer will result in reduced expression and may be anywhere from one third to two thirds the level of expression obtained if both Enhancers had been added on time.

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Expi293F cells must be recovered from freezing and passaged at least 3 times using the procedure outlined in the manual to ensure optimal performance. Cells should maintain performance for at least 30 passages if maintained in accordance with the protocol in the manual.

The formation of intact IgG molecules may be quantitated using a sandwich ELISA designed to capture and detect rabbit IgG. Besides the rabbit IgG positive control, reagents, and consumables that are included in the kit, you will also need purified rabbit IgG to be used as a standard, F(ab')2 goat anti-rabbit IgG HRP conjugate (Cat. No. A10547), Protein A-coated plates (Cat. No. 15130 for clear plates used in colorimetric detection), TMB colorimetric substrate (Cat. No. 34021), SuperBlock (TBS) Blocking Buffer (Cat. No. 37581), and PBS or TBS buffer for washes. There is an example procedure in our Protein A-coated plates manual (https://assets.thermofisher.com/TFS-Assets/LSG/manuals/MAN0011310_Pierce_ProteinA_G_AG_Coat_96Well_UG.pdf). Please note, our R&D scientists determine titer values from crude cell culture supernatants using a Pall Life Sciences FortéBio Octet instrument equipped with a protein A biosensor.

Find additional tips, troubleshooting help, and resources within our Protein Expression Support Center.