Insulin Like Growth Factor Binding Protein 1 (IGFBP1) is a member of the IGFBP family that binds to insulin-like growth factors (IGFs) with high affinity. IGFBP1 plays a crucial role in regulating the biological activities of IGFs, which are important for growth and development. IGFBP1 is primarily produced in the liver and is also secreted by various other tissues, including the decidua of the uterus during pregnancy. Its levels in the bloodstream are influenced by factors such as nutritional status, insulin levels, and growth hormone. To detect the activity of recombinant GFBP1, a functional ELISA assay was performed to evaluate the interaction between recombinant human IGFBP1 and recombinant rabbit Insulin-Like Growth Factor 2 (IGF2).Briefly, biotin-linked IGFBP1 were diluted serially in PBS, with 0.01% BSA (pH 7.4). Duplicate samples of 100µl were then transferred to IGF2-coated microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST 3 times and incubation with Streptavidin-HRP for 30min, then wells were aspirated and washed 5 times. With the addition of substrate solution, wells were incubated 15-25 minutes at 37℃. Finally, add 50µl stop solution to the wells and read at 450nm immediately. The binding activity of IGFBP1 and IGF2 was shown in Figure 1, the EC50 for this effect is 0.085µg/mL.