Role of oxygen in biodegradation of poly(etherurethane urea) elastomers

Abstract

It is generally accepted that biodegradation of poly(etheruethane urea) (PEUU) involves oxidation of the polyether segments on the surface where leukocytes are adhered. The influence of dissolved oxygen, which is known to control oxidation of polymers in more traditional environments, was explored in this study. Specimens treated in vitro with hydrogen peroxide-cobalt chloride for 12 days exhibited a brittle, degraded surface layer about 10 microm thick. Attenuated total reflectance-Fourier transform infrared spectroscopy of the surface revealed that the ether absorbance at 1110 cm(-1) gradually decreased with in vitro treatment time to 30% of its initial value after 12 days. In contrast, 6 days in vitro followed by 6 days in air produced a decrease to 12% of the initial volume. Therefore, removing a specimen from the in vitro solution after 6 days and exposing it to air for the remainder of the 12 days actually resulted in more oxidation than leaving it in the in vitro solution for the entire 12 days. These results suggest that PEUU degrades by an autooxidation mechanism sustained by oxygen. By successfully modeling the depth of the surface degraded layer with a diffusion-reaction model, it was demonstrated that PEUU biodegradation is controlled by diffusion of oxygen into the polymer.

Oxidatively degradable poly(thioketal urethane)/ceramic composite bone cements with bone-like strength

“…An accelerated degradation medium comprising 20 wt% hydrogen peroxide in 0.1 M cobalt chloride in DI water simulated the environment produced by reactive oxygen species at the implant site. 20, 30, 31 PTKUR films (17 mg) were immersed in 350 μL (1 mL/50 mg initial sample) degradation media and placed on a shaker table at 37°C. PTKUR degradation was compared to lysine-derived poly(caprolactone urethane) (PCLUR), which was expected to undergo minimal hydrolytic degradation.…”

A porous tissue engineering scaffold selectively degraded by cell-generated reactive oxygen species

“…Short term oxidative degradation rates of PTK-UR scaffolds were similarly assessed using an oxidative degradation medium that simulates in vivo oxidative degradation at an accelerated rate [49, 50]. This oxidative medium comprised 20 wt% hydrogen peroxide (H 2 O 2 ) in 0.1 M cobalt chloride (CoCl 2 ), with the H 2 O 2 and cobalt ion reacting to stimulate oxidative radical formation [49]. As with the long-term study, triplicate samples were pre-soaked in DCM for 24 h before vacuum drying and incubated at 37°C in the oxidative medium on a shaker.…”

Mechanical characterisation of polyurethane elastomer for biomedical applications

“…This is 303 adequately covered in literature (Stokes et al, 1995;Wiggins et al, 2003;Thoma, 1987;Schmidt et 304 al., 1998;Zhao et al, 1990Zhao et al, , 1991Wu et al, 1992;Schubert et al, 1995Schubert et al, , 1997 …”