Modification of mechanical properties of fibrin gel

Objectives: Fibrin is widely used in biomedical materials such as surgical glues and hemostatic agents. Fibrin gel has also been considered as a cell scaffold for tissue engineering. To increase the clinical application of fibrin gel as a cell scaffold, regulation of its mechanical properties is crucial. To address this goal, fibrin gel was fabricated in the presence of poly-L-lysine and Ca2+, and its mechanical properties were evaluated. Poly-L-lysine and Ca2+ were expected to enhance the chemical binding between fibrin fibrils. Methods: Fibrinogen solution (4mg/ml) was mixed with thrombin solution (2.5U/ml) in a 1:1 ratio, and the mixed solution was poured into a silicone mold (length: 10mm, diameter: 6mm) for gelation (30min, 37°C). Fibrin gels containing 0–20µg/ml of poly-L-lysine or 0–5mM of CaCl2 were prepared (n = 6) as samples. The tensile strength and viscoelastic properties of the obtained gel were investigated. Fibril structures in the gel were observed by SEM. Results: Addition of poly-L-lysine or CaCl2 to fibrin increased the tensile strength and storage modulus of fibrin gel compared with the control fibrin gel. This tendency was significant at 0.5µg/ml of poly-L-lysine, 3.75mM of CaCl2 (p < 0.01). Fibrin gels fabricated with poly-L-lysine and Ca2+ showed approximately 2.8- and 4.8-fold increases in strength, respectively. The fibrils in the fibrin gel showed a thin and branched structure on addition of poly-L-lysine or CaCl2. Conclusion: This study suggests that the addition of poly-L-lysine or Ca2+ induces a structural change in fibrin fibrils, and that poly-L-lysine or Ca2+ might be effective for regulating the mechanical properties of fibrin gel.