Type I collagen is a fibril-forming collagen found in most connective tissues and is abundant in bone, cornea, dermis and tendon. It is a heterotrimer that consists of two alpha 1 chains and one alpha 2 chain, although homotrimers consisting of three identical alpha 1 chains have also been described. Thus a functional binding ELISA assay was conducted to detect the interaction of recombinant human COL1a1 and recombinant human COL1a2. Briefly, biotin-linked COL1a1 were diluted serially in PBS, with 0.01% BSA (pH 7.4). Duplicate samples of 100 ul were then transferred to COL1a2-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 50 μl stop solution to the wells and read at 450 nm immediately. The binding activity of COL1a1 and COL1a2 was shown in Figure 1, the EC50?for this effect is 10.13 ug/mL.