Ligand–receptor interactions in complex media: A new type of biosensors for the detection of coagulation factor VIII

Detection of receptor–ligand interaction in complex media remains a challenging issue. We report experimental results demonstrating the specific detection of the coagulation factor VIII in the presence of a large excess of other proteins using the new BIA-ATR technology based on attenuated total reflection Fourier transform infrared spectroscopy. The principle of the detection is related to the ability of factor VIII molecules to bind to lipid membranes containing at least 8% phosphatidylserine. Several therapeutic concentrates of factor VIII were analyzed and the binding of the coagulation factor was monitored as a function of time. We show that a non-specific adsorption of stabilizing agents (typically, von Willebrand factor and human serum albumin) may be avoided by controlling the geometry of the ATR element. A linear response of the sensors as a function of the factor VIII concentration is described for different lipid membrane compositions.