Development of a biosensor immunoassay for the quantification of alpha S1-casein in milk.

摘要

An immunoassay to quantify alpha S1-casein ( alpha S1-CN) in milk using an optical biosensor, based on surface plasmon resonance (SPR) measurement, has been developed. The assay consists of a two-step sandwich strategy, with two anti- alpha S1-CN antibodies directed against each extremity of the molecule. This strategy permits only intact alpha S1-CN to be quantified and not its degradation products. The calibration curve was obtained using a reference milk powder with a known alpha S1-CN concentration. Analysis time per sample was less than ten minutes. The antibody-coated surface could be used for more than 150 determinations. Detection limit was established at 0.87 micro g/ml and the intra- and inter-assay variation coefficients were 2.86 and 5.31%, respectively. The method was applied to raw milk to quantify intact alpha S1-CN, with no pre-treatment of the sample. An initial analysis of 48 milk samples permitted alpha S1-CN concentrations ranging from 8.8 to 12.06 mg/ml to be obtained.