Acellular vascular grafts generated from collagen and elastin analogs

Tissue-engineered vascular grafts require long fabrication times, in part due to the requirement of cells from a variety of cell sources to produce a robust, load-bearing extracellular matrix. Herein, we propose a design strategy for the fabrication of tubular conduits comprising collagen fiber networks and elastin-like protein polymers to mimic native tissue structure and function. Dense fibrillar collagen networks exhibited an ultimate tensile strength (UTS) of 0.71 ± 0.06 MPa, strain to failure of 37.1 ± 2.2% and Young's modulus of 2.09 ± 0.42 MPa, comparing favorably to a UTS and a Young's modulus for native blood vessels of 1.4-11.1 MPa and 1.5 ± 0.3 MPa, respectively. Resilience, a measure of recovered energy during unloading of matrices, demonstrated that 58.9 ± 4.4% of the energy was recovered during loading-unloading cycles. Rapid fabrication of multilayer tubular conduits with maintenance of native collagen ultrastructure was achieved with internal diameters ranging between 1 and 4 mm. Compliance and burst pressures exceeded 2.7 ± 0.3%/100 mmHg and 830 ± 131 mmHg, respectively, with a significant reduction in observed platelet adherence as compared to expanded polytetrafluoroethylene (ePTFE; 6.8 ± 0.05 × 105 vs. 62 ± 0.05 × 105 platelets mm-2, p < 0.01). Using a rat aortic interposition model, early in vivo responses were evaluated at 2 weeks via Doppler ultrasound and CT angiography with immunohistochemistry confirming a limited early inflammatory response (n = 8). Engineered collagen-elastin composites represent a promising strategy for fabricating synthetic tissues with defined extracellular matrix content, composition and architecture.