Preparation of fibrin clot samples for tensile stress-strain experiments

New method to prepare autologous fibrin glue on demand

Fibrin-based sealants are commonly employed to arrest bleeding after surgery. Usually, fibrinogen obtained from pooled human plasma is used to prepare sealants, with attendant risk of blood-borne infections. Availability of autologous fibrinogen would eliminate this risk. To prepare autologous fibrin sealant, fibrinogen was precipitated from human plasma using protamine. Under optimal conditions (10-mg/mL protamine and 22 degrees C), 96 +/- 4% of clottable fibrinogen was recovered by a simple and inexpensive technique. Nearly 50% of the plasma factor XIII was also recovered with the fibrinogen. Using bovine thrombin, the fibrinogen was clotted (1) in a specially designed mold to measure tensile strength and (2) in a lap joint between 2 aortic vessel strips to measure adhesion strength. Tensile and adhesion strengths increased with increasing fibrinogen concentration, and they were increased by the addition of calcium chloride. The addition of aprotinin and -aminocaproic acid to the fibrinogen concentrate before clotting had no effect on the mechanical properties of the clots. After adding thrombin to sealant containing 15-mg/mL fibrinogen, maximum tensile strength was achieved in 1-5 min, and maximum adhesion strength was reached in 5-15 min. For the sealant with 30-60-mg/mL fibrinogen and added calcium, the tensile strength was equivalent to that of the commercial fibrin sealant Tisseel. The adhesion strength of sealant with 30-60-mg/mL fibrinogen exceeded the adhesive strength of Tisseel under identical conditions. Autologous fibrin sealant is an attractive alternative to commercial sealants. It can be readily prepared from 5-mL plasma or more and exhibits mechanical properties equivalent to those of the leading commercial sealant.