Pleiotrophin (PTN) is a 136 amino acid secreted heparin-binding cytokine that signals diverse functions, including lineage-specific differentiation of glial progenitor cells, neurite outgrowth, and angiogenesis. A considerable amount of research has been carried out to understand the mechanisms by which PTN regulates these events. PTN has now been shown to bind a diverse collection of receptors including Syndecan 1 (SDC1). A functional binding ELISA assay was conducted to detect the interaction of recombinant human PTN and recombinant human SDC1. Briefly, PTN were diluted serially in PBS, with 0.01% BSA (pH 7.4). Duplicate samples of 100 µl were then transferred to SDC1-coated (2 ug/ml, 100 ul/well) microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST and incubated for 1h with PTN pAb, then aspirated and washed 3 times. After incubation with HRP labelled secondary antibody, 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 recombinant human PTN and recombinant human SDC1 was shown in Figure 1, the EC50 was 3.47 ug/ml.