On the relationship between the adhesive properties and the structural features of fibrin sealants

The relationship between the adhesive properties and network architecture of fibrin sealants was studied at various fibrinogen, thrombin and calcium ion concentrations. Network features were characterized using Scanning Electron Microscopy at cryogenic temperature (cryo-SEM). This technique allows examination of the hydrated gel without drying. It was shown that by gradually increasing the calcium ion concentration, at constant thrombin and fibrinogen concentrations, the network appearance changed dramatically, from an almost isotropic structure at low concentration to highly oriented fibers at higher concentration of 7 mM CaCl₂. In addition, it was found that further increase in the calcium ion concentration induced fiber aggregation and formation of large clusters, co-existing with fine fibers. Changes in thrombin concentration at constant calcium and fibrinogen concentrations induced only slight changes in the gel appearance. Adhesive properties of fibrin sealants were measured using the shear-lap test and were correlated with structural features of the network. Holding fibrinogen and thrombin concentrations constant and varying the CaCl₂ concentration, maximal shear strength was found with 7 mM CaCl₂, corresponding to an oriented network. Holding fibrinogen and calcium chloride concentrations constant, a slight increase in shear strength was observed with increase in thrombin concentration, demonstrating again the correlation between the network structure and its adhesive properties.