本试剂盒应用双抗体夹心酶标免疫分析法测定标本中C-Peptide水平。用纯化的抗体包被微孔板，制成固相抗体，往包被单抗的微孔中依次加入C-Peptide抗原、生物素化的抗人C-Peptide抗体、HRP标记的亲和素，经过彻底洗涤后用底物TMB显色。TMB在过氧化物酶的催化下转化成蓝色，并在酸的作用下转化成最终的黄色。颜色的深浅和样品中的C-Peptide呈正相关。用酶标仪在450nm波长下测定吸光度（OD值），计算样品浓度。
Intended use
This immunoassay kit allows for the specific measurement of human C-Peptide concentrations in serum and plasma.
Introduction
Human insulin and C-Peptide originate as a single polypeptide chain known as proinsulin(MW 9000) in the pancreatic cell. Proinsulin is cleaved proteolytically to form equimolar amounts of mature insulin and C-Peptide that are released into the portal vein. So called because it connects the A and B chains of insulin in the proinsulin molecule. C-Peptide is a single chain of 31 amino acid (MW 30,200). Unlike insulin has no known physiological function. Because C-Peptide has a longer half-life than insulin (2-5 times longer), high concentrations of C-Peptide persist in the peripheral circulation and these level fluctuate less insulin. For these reasons, in plasma C-Peptide concentrations may reflect pancreatic insulin secretion more reliable than the level of insulin itself1. C-Peptide is cleaved from the body by the kidney. Urine concentrations of C-Peptide are 20-50 times higher than in plasma, unlike plasma insulin levels, which fluctuate in response to meals, measurement of the 24 hour urinary excretion of C-Peptide provides a useful monitor of average cell insulin secretion 2. C-Peptide measurements are useful in insulinoma diagnosis, especially in patients treated with insulin. Elevated C-Peptide levels are indicative of insulinoma. C-Peptide measurements are useful in the need for progression to insulin therapy in non-insulin dependent diabetics (NIDDM). C-Peptide measurements are useful as a marker for residual pancreatic tissue after pancreatectomy. It may also be used to monitor the progress of pancreas or islet cell transplantation. C-Peptide measurements are useful in the diagnosis of hypoglycemia brought on by surreptitious insulin administration.
Test principle
This assay employs the quantitative sandwich enzyme immunoassay technique. A monoclonal antibody specific for C-Peptide has been pre-coated onto a microplate. Standards and samples are pipetted into the wells and any C-Peptide present is bound by the immobilized antibody. An enzyme-linked monoclonal antibody specific for C-Peptide is added to the wells. Following a wash to remove any unbound antibody-enzyme reagent, a substrate solution is added to the wells and color develops in proportion to the amount of C-Peptide bound in the initial step. The color development is stopped and the intensity of the color is measured.
