In order to confirm the specific degradation of the protein component of the hybrid scaffold, we analyzed the ratio of the amide II:carbonyl FTIR peaks (A:C ratio). This analysis allowed us to quantify the ratio of protein (collagen) versus polymer (PCL) within the sample as it undergoes biodegradation. We report significant reduction in the A:C ratio (Supplementary Fig. 3C) after 56 days, suggesting loss of protein (collagen) component in the sample during biodegradation but relative stability of the polymer (i.e. PCL) component.
Mechanical anisotropy and cellular alignment is important in organs and tissues such as axonal bundles, muscle, and cardiac valves [39], [40] and [41]. We measured the mechanical properties of SANF scaffolds via uniaxial mechanical testing with samples maintained at 37 °C in a PBS bath. Elastic stress-strain behavior of SANF PCL and PCL/Collagen-75/25 (Fig. 5A) showed mechanical anisotropy between the fiber (FD) and cross-fiber (X-FD) directions. Further, the Young's modulus and maximum strain of the PCL/Collagen scaffold is on the same order of magnitude as cardiac muscle and heart valve leaflets [39], suggesting their suitability for cardiovascular tissue engineering applications. In contrast, PCL constructs were an order of magnitude stiffer and had an elastic limit of 10% strain (Fig. 5A). The low extensibility of pure PCL scaffolds limits their utility in tissue engineering applications.