Similar trends are perceived when it comes to implantable gels, which are often tested as drug delivery vehicles and have shown to promote anti-bacterial, anti-inflammatory, or anti-fouling properties. One such example effectively created a hydrogel tube (PNASC) that was tested as an artificial blood vessel in rabbits. The authors implanted a 3 cm long hydrogel tube and did not observe hemorrhage after the implantation (vascular anastomosis) for 4 h. Among the few types of blood vessels studied, the fracture energy of pig aorta was Γ = 1.8 kJ/m 2 . Whether this value is similar to rabbit or human tissue, however, is still unknown.