Poly(carbonate urethane) vs Poly(ether urethane) in vivo biodegradation

http://capricenter.cwru.edu/Published%20papers/Christenson-PCU%20In%20Vivo-2006.pdf

In this article, the effects of an antioxidant on the in vivo biodegradation of a poly(ether urethane) and a poly(carbonate urethane) synthetic vascular graft were compared. Foreign-body response as a biodegradation factor was also investigated. I’m not going to focus on the antioxidant or biological effect on the biodegradation, but instead I’ll focus on the differences between the biodegradation on the two polyurethanes without the antioxidant added. (FYI: The antioxidant, santowhite, inhibits the oxidation by capturing oxygen radicals. It also prevents surface cracking)

In their experiment, unstrained Elasthane (PEU) and Bionate (PCU) specimens were implanted into 3 month old rats. In the article, the specimens were removed after 1 years and images were taken:

The Elasthane (PEU) specimen has extensive surface microcracking covering a majority of the surface area. The Bionate (PCU) specimen had some small pits, however no microcracking was observed. The specimens were then strained to fracture and allowed to recover. Under high magnification, the stretched Elasthane specimen had another group of surface cracks running perpendicular to the stretch direction. But Once again, no surface cracking was seen on the Bionate Specimen. However, some surface buckling occurred, which causes a wave-like pattern. This was attributed to the plastic deformation of the surface layer. Although the surface damage of the explanted PCU was minor, the surface buckling indicated that the film had undergone some degradation.

In conclusion, the PEU specimen was not as biostable as the PCU specimen, and thus the PCU specimen would be a better candidate for the outer reinforcing layer of a vascular graft.

I'm interested in vascular grafts and their applications in bypass surgery, so this article interested me. The in vivo biodegradation of the grafts is a significant property that needs to be studied. If the grafts will not last for many years, then patency of the affected arteries can not be permanently achieved.