The bioactivity of EGF was determined using the Promega serum response element luciferase reporter assay in HEK293T cells. Cells were treated in triplicate with a serial dilution of EGF for 3 hours in conditioned media. Firefly luciferase activity was measured at days 0 and 2 and normalized to the control Renilla luciferase activity.
The bioactivity assay showed that EGF has high bioactivity at day 0 and maintained stable bioactivity after 2 days in conditioned media. The stability of EGF in conditioned media provides a reliable source of animal-free EGF. This has the potential to improve the reproducibility in self-renewal and differentiation for iPSC, ESC, and organoid cultures.