Compared to expression in lower-order organisms, recombinant protein expression in mammalian cells offers significant advantages in protein quality and post-translational modification. Though transient transfection of mammalian cells has been employed for recombinant protein expression since the invention of transfection reagents, the ability to express milligram-to-gram amounts of recombinant protein has relied mainly on the creation of stable cell lines. More recently, large volume transient transfection of HEK293 and CHO cells adapted to suspension culture has addressed the need to obtain high amounts of recombinant protein without having to resort to the laborious process of stable cell line development. Recombinant protein expression by transient transfection enables researchers to produce, starting from the vector of interest and suspension-adapted CHO or HEK293 cells, milligram-per-liter quantities of correctly folded and glycosylated recombinant proteins in three to seven days.

Additional benefits of transient protein expression in mammalian cells include:

  • Rapidly go from cloned gene to large quantities of protein in 3-7 days
  • Obtain fully post-translationally modified and active mammalian proteins
  • Use your available mammalian cell culture facilities with shake flasks and a platform shaker
  • Easily purify secreted proteins from the serum free cell culture medium
  • Scale-up from 50 multi-well plates to to 25 L of culture volume and more

Featured Products

Expi293™ Expression System
The Expi293™ Expression System includes GIBCO® Expi293™ Expression Medium, Expi293F™ Cells, and the ExpiFectamine™ 293 Transfection Kit.  These components work together to enable high density transient transfection of Expi293F™ Cells for rapid and ultra high-yield protein production.


FreeStyle™ MAX CHO Expression System and FreeStyle™ MAX 293 Expression System
FreeStyle™ MAX Expression System combines GIBCO® FreeStyle™ Media, FreeStyle™ MAX Reagent, and either FreeStyle™ CHO-S cells or FreeStyle™ 923 cells.  The FreeStyle™ MAX Systems can replace time-consuming stable cell line generation with large-scale functional protein production in one week.


FreeStyle™ MAX Reagent
FreeStyle™ MAX Transfection Reagent is a novel transfection reagent to transfection FreeStyle™ CHO and HEK-293 cells with exceptionally high efficiency to enable rapid and milligram scale of protein yield per liter.

Your partner in Transient Protein Production

Life Technologies™ supplies all required materials that are fully compatible with transient protein production including cell culture media, suspension adapted CHO and HEK-293 cells, vectors, plasmid purification products, and transfection reagents.  For researchers wishing to establish mammalian transient protein production in their laboratories, Life Technologies™ provides:

  • Starter kits, Expi293™ Expression System, FreeStyle™ MAX CHO Expression System and FreeStyle™ MAX 293 Expression System
  • Technical webinars and guidance on obtaining needed laboratory equipment
  • Technical Support
  • Hands-on training courses
  • Custom protein production services based on the above transient protein production systems