Changes in functional activities of plasma fibrinogen after treatment with methylene blue and red light

BACKGROUND: Methylene blue (MB) plus light treatment used for virus inactivation of human plasma units may lead to changes in the functional activities of fibrinogen. STUDY DESIGN AND METHODS: Single-donor units of fresh plasma were treated with 1.0 muM MB and a red light dose of 48 J per cm(2). The effects of MB plus red light treatment on fibrinogen clottability, fibrin polymerization and gelation, clot stabilization, and fibrinolysis were studied. RESULTS: The concentration of clottable fibrinogen was unchanged during MB plus red light treatment, but a light-close-dependent decrease of the concentration of functional fibrinogen was found. The initial release rate of fibrinopeptide A was slightly increased after MB plus red light treatment. Turbidity measurements of fibrin gel showed prolonged clotting time, lower fibrin fiber mass-to-length ratio, and slightly smaller fiber diameter. At a given clotting time, a gel with lower fibrin fiber mass-to-length ratio was produced. Clot stability and fibrinolysis remained normal. L-Histidine added to plasma before MB plus red light treatment normalized the thrombin-induced coagulation time in a dose-dependent way. CONCLUSION: MB plus red light treatment affected the polymerization and gelation phase of fibrin. A tighter fibrin gel structure was formed. No effect on stabilization of fibrin clot or fibrinolysis was found.