Collagen, fibrin and collagen-fibrin mixtures as matrix materials for vascular tissue engineering

The mechanical and functional properties of engineered blood vessels are determined largely by the characteristics of the scaffold matrix. In the present study, bovine collagen, rat collagen, bovine fibrin and a 1:1 bovine collagen-fibrin mixture were used to mold vascular constructs containing isolated smooth muscle cells. Mechanical property testing showed that each material had a characteristic stress-strain profile and failure mode. Examination of the linear modulus indicated that bovine collagen was the stiffest material (modulus of 191.4±4.9 kPa), while pure bovine fibrin was the least stiff (27.9±1.6 kPa). The collagen-fibrin mixture had an intermediate modulus (153.4±7.0 kPa), while pure rat collagen (39.5±1.4 kPa) was markedly less stiff than bovine collagen. Ultimate tensile stress was highest for the collagen-fibrin mixture scaffolds (49.7±3.0 kPa). Bovine collagen alone (36.1±0.8 kPa) was stronger than rat tail collagen (3.9±0.1 kPa), and was also stronger than bovine fibrin alone (15.6±1.2 kPa). Constructs made with fibrin compacted to a greater degree than purely collagen-based constructs, leading to a denser matrix and increased stress values. These studies show that the properties of engineered blood vessels can be modulated by combining different naturally-derived matrix materials.