Insulin Like Growth Factor Binding Protein 4 (IGFBP4), corresponding to product code A055Ra, is a key member of the IGFBP family, widely expressed in tissues like the liver, kidneys, and bones. Its primary role is to regulate the biological activity of Insulin Like Growth Factors (IGFs). By binding to IGFs, it controls their free concentration in the circulation, prevents rapid degradation, and modulates their transport to target tissues. IGFBP4 also participates in processes such as cell proliferation, differentiation, and tissue development, with implications in growth disorders and cancer research. IGFBP4 (A055Ra) specifically binds to IGF1 (A050Po), regulating IGF1’s availability to its receptors and thus its biological effects.Briefly, IGF1 was diluted serially in PBS with 0.01% BSA (pH 7.4). Duplicate samples of 100 μl were then transferred to IGFBP4-coated microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST and incubated for 1h with anti-IGF1 pAb, then aspirated and washed 3 times. After incubation with HRP labelled secondary antibody for 1h at 37℃, wells were aspirated and washed 5 times. With the addition of substrate solution, wells were incubated 15-25 minutes at 37℃. Finally, add 50 µL stop solution to the wells and read at 450/630nm immediately.Measured by its binding ability in a functional ELISA. When Recombinant IGFBP4 is lmmobilized at 2 µg/mL(100 uLwell), the concentration of IGF1 that produces 50% optimal bindingresponse is found to be approximately 0.0938 µg/mL.