In situ immunoradiometric assay of fibrinogen adsorbed to artificial surfaces

An in situ immunoradiometric assay was devised to quantitate human fibrinogen deposited on hemodialysis membrane, Cuprophane, from in vitro exposure to fibrinogen solution and from ex vivo extracorporally clinical use. The method requires a monospecific 125I-labeled antifibrinogen -IgG purified by DEAE chromatography and immunoadsorption. The labeled antifibrinogen IgG was shown to react specifically with fibrinogen adsorbed and immobilized (by glutaraldehyde) on Cuprophane. Other plasma proteins such as human albumin, IgG, or alpha-thrombin, adsorbed singly or coadsorbed with fibrinogen on the surface did not seem to affect the fibrinogen- antifibrinogen reaction. The presence of blood cells such as platelets and granulocytes with fibrinogen on Cuprophane reduced only slightly the uptake of 125I- antifibrinogen -IgG. The examination of fibrinogen-fibrin deposition on clinically used Cuprophane by this technique and by autoradiography of the same material following 125I- antifibrinogen -IgG conjugation indicated that the deposition of fibrinogen was heavy and heterogeneous. We concluded that this in situ method may be useful to monitor fibrinogen-fibrin deposition and adsorption of other plasma proteins that occur under in vitro, ex vivo, and in vivo conditions.