Simultaneous measurements of dynamic modulus and turbidity and effects of calcium ions on the process of thrombin-induced fibrin gel formation

Abstract

Aqueous solution of fibrinogen, one of blood clotting factors, forms a fibrin gel by the action of enzyme thrombin. Calcium ions are known to affect not only the gelation kinetics but the structure of fibrin gel network. Dynamic modulus and turbidity have been used to monitor the gelation, however, there are few reports to compare the two data sets. In this study, we have carried out simultaneous measurements of the dynamic modulus and transmitted light intensity during fibrin gelation using a newly developed coaxial-cylinder rotational rheometer with transparent inner and outer cylinders. The measurements for dynamic modulus were carried out at an oscillation frequency of 1 Hz and an oscillation amplitude of 1 mrad in the presence of calcium ions (1–50 mM). After the addition of thrombin to fibrinogen solution, an opaque fibrin gel was formed. The decrease in the transmitted light intensity occurred faster than the increase in the elastic modulus due to the stepwise fibrin polymerization. The time courses of the dynamic moduli and the transmitted light intensity were well expressed using empirical exponential-type equations. The parameters obtained by fitting the data to the equations closely related to the gelation kinetics and the network structure of fibirin. We discuss the effect of calcium ions on the parameters.