Detection Method:Sandwich
Test principle:This assay employs a two-site sandwich ELISA to quantitate CTX-I in samples. An antibody specific for CTX-I has been pre-coated onto a microplate. Standards and samples are pipetted into the wells and anyCTX-I present is bound by the immobilized antibody. After removing any unbound substances, a biotin-conjugated antibody specific for CTX-I is added to the wells. After washing, Streptavidin conjugated Horseradish Peroxidase (HRP) is added to the wells. Following a wash to remove any unbound avidin-enzyme reagent, a substrate solution is added to the wells and color develops in proportion to the amount of CTX-I bound in the initial step. The color development is stopped and the intensity of the color is measured.
Product Overview:The carboxyterminal telopeptide of type I collagen (ICTP) is an indicator of degradation of type I collagen. ICTP antigen consists of a trivalent collagen cross-link joining three polypeptide chains of which two are α1 chains of one collagen molecule while the third is derived from either an α1 or an α2 chain of the helical region of another molecule (Fig. 1) (Risteli?et al.?1993). The major determinant for antigeneity must contain two phenylalanine-rich regions, which is only possible if the cross-link is trivalent in nature (Sassi?et al.?2000). In osteoclasts, catepsin K cleaves the trivalently cross-linked ICTP structure at two sites between the phenylalanine-rich region and the cross-link, thereby destroying any reactivity with ICTP antibodies (Sassi?et al.?2000). Therefore degradation of type I collagen in bone is not measurable by the present ICTP-test. ICTP is cleared from circulation by the kidneys and has a molecular mass of about 12 000C20 000 (Risteli?et al.?1993).