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Culturing Sf21 and Sf9 cells
Sf21 cells (IPLB-Sf21-AE) are ovarian insect cells isolated from Spodoptera frugiperda (Fall Armyworm). Sf21 cells can be thawed and used directly in suspension culture for rapid expansion of cell stocks, propagation of baculovirus stocks, and production of recombinant proteins. Because Sf21 cells attach firmly to surfaces, they can be used as a monolayer for transfection or plaque assay applications.
Sf9 cells (IPLB-Sf-21-AE) are derived from the parental Spodoptera frugiperda cell line and are a suitable host for expression of recombinant proteins from baculovirus expression systems.
Although insect cells have been historically cultured in stationary systems utilizing T-flasks and serum-supplemented basal medium, insect cells are generally not anchorage dependent and can easily be maintained in suspension culture. Once insect cells reach confluency, they should be subcultured.
Morphology of Sf21 cells
Sf21 cells are spherical in shape with unequal sizes, and have a somewhat granular appearance.
The images below show the morphology of healthy Sf21 insect cells in suspension culture (Figure 1) and in adherent culture at confluency (Figure 2).
Figure 1. Phase contrast images of healthy Sf21 insect cells grown in suspension. The culture was started in a shake flask at a seeding density of 3 × 105 viable cells/mL in Sf-900 II SFM medium and it was maintained in a 28°C, non-humidified, ambient air-regulated incubator. The images were obtained using 10X and 20X objectives (panels A and B, respectively) 3 days after seeding.
Figure 2. Phase contrast images of Sf21 insect cells grown as an adherent monolayer in 293 SFM II medium. The cells were plated at a seeding density of 5 × 104 viable cells/cm2 in a T-25 flask and grown as monolayers in a 28°C, non-humidified, ambient air-regulated incubator. The images were obtained using 10X and 20X objectives (panels A and B, respectively) 7 days after seeding, when the culture had reached confluency.
Morphology of Sf9 cells
The images below show the morphology of healthy Sf9 insect cells in suspension and adherent cultures. Sf9 cells attach firmly to surfaces, and their small, regular size makes them exceptional for the formation of monolayers and plaques.
Figure 3. Phase contrast images of healthy Sf9 insect cells grown in suspension. The culture was started in a shake flask at a seeding density of 3 × 105 viable cells/mL in Sf-900 II SFM medium and it was maintained in a 28°C, non-humidified, ambient air-regulated incubator. The images were obtained using 10X and 20X objectives (panels A and B, respectively) 3 days after seeding.
Figure 4. Phase contrast images of healthy Sf9 insect cells grown as an adherent monolayer in Sf900 II SFM medium. The cells were plated at a seeding density of 5 × 104 viable cells/cm2 in a T-25 flask and grown as monolayers in a 28°C, non-humidified, ambient air-regulated incubator. The images were obtained using 10X and 20X objectives (panels A and B, respectively) 3 days after seeding.
