BioVision’s human Osteopontin (OPN) Enzyme-Linked Immunosorbent Assay (ELISA) Kit is an in vitro assay for the quantitative measurement of human OPN. OPN is a multifunctional, hyperphosphorylated acidic glycoprotein. As a key component of extracellular matrix-associated protein abundantly expressed in bone, OPN is a key regulator of bone mineralization. In addition, OPN is expressed in multiple other cell types including macrophages, smooth muscle cells and hepatocytes. OPN up-regulation occurs upon exposure to pro-inflammatory cytokines (TNF-α, TGF-β etc.) or under pathological conditions such as hypoxia and hyperglycemia. OPN also functions as a chemokine-like protein involved in regulating cell proliferation, inflammatory responses, angiogenesis and metastasis, and is critical in the development of multiple disorders including cardiovascular disease, diabetes, and cancer. The assay employs monoclonal antibody specific for human OPN coated on a 96-well microplate. Standards and samples are pipetted into the wells and OPN present in the sample is bound to the wells by the immobilized antibody. The antibody-captured OPN is then detected by a biotinylated monoclonal antibody. With HRP conjugated Streptavidin and a HRP substrate, amount of OPN in the sample is determined by measuring absorbance of the HRP product at 450 nm with a microplate reader. The sensitivity of the kit is 0.2 ng/ml and detection range is from 0.2 ng to 70 ng/ml. The intra-assay reproducibility as measured by the coefficient of variation (CV) is <5 % & inter-assay CV < 7 %.