2.14 SEM of vascular structure
The 3D bionics vascular structure was fixed with 2.5% glutaraldehyde (Sigma-Aldrich, USA) at 4 ℃ for 4 hours after 7 days of culture. The structure was dehydrated with 30%, 50%, 70%, 80%, 90%, 95% and 100% ethanol for 20 minutes each. After replacing the ethanol with Co2 by a critical point dryer (Leica, EM CPD 300, Germany) and coating with gold, the samples were observed by SEM.