FIG. 6.
Opening angle measurement to determine residual stress within scaffolds. (A) Intact scaffold in stressed state. (B) Native scaffold in zero stress state achieved by radial cut of ring section producing an opening angle θ. (C) Decellularized scaffolds displayed a reduced value for θ compared with native scaffolds. (D) Customized scaffolds revealed an excessive reduction in θ to the extent that the scaffold recoiled beyond the diameter of the zero stress state. These θ values are taken as negative. (E) Boxplot of opening angles for each freeze-drying cycle. Decellularized scaffolds display a significant reduction in θ compared with the native tissue. Customized scaffolds see a significant decrease in θ due to collagen digestion, compared with both native tissue and decellularized scaffolds. Freeze drying reduces the opening angle for the decellularized scaffolds and increases this angle for each of the customized scaffolds, which can be attributed to collagen fiber damage and scaffold heterogeneity. The opening angles of the SF Tf=−40°C scaffolds are reverted back toward that of the native tissue. Statistical significance is indicated as *p<0.05.