Fibroblast Growth Factor Bioactivity Measurements Using Live-Cell Biosensor Imaging

Growth factor proteins are essential reagents for cell culture and tissue engineering but require quality control for bioactivity. Currently, growth factor bioactivity measurements made by immunoblot or ELISA are limited in evaluating the kinetics and heterogeneity of cellular responses, and there is a need for convenient methods with higher temporal and spatial resolution. In this study, we evaluate the advantages of using genetically encoded biosensors to quantify growth factor bioactivity in living cells. Using fibroblasts expressing a FRET-based biosensor of ERK activity, we compare methods for quantifying the cellular response across several doses and sources of recombinant basic fibroblast growth factor (bFGF). In contrast to immunological methods, the biosensor-based approach provides single-cell ERK activity kinetics and robust dose-response curves with minimal experimental processing. We additionally demonstrate that this method can assess bFGF activity in induced pluripotent stem cells and resolve spatial activity patterns. We conclude that biosensors represent a rapid, high-quality bioactivity assay extendable to other growth factors and signaling pathways.