The Experts below are selected from a list of 1611 Experts worldwide ranked by ideXlab platform
Anne Hiltner - One of the best experts on this subject based on the ideXlab platform.
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enzymatic degradation of poly Ether Urethane and poly carbonate Urethane by cholesterol esterase
Biomaterials, 2006Co-Authors: Elizabeth M. Christenson, Sachin Patel, James M Anderson, Anne HiltnerAbstract:Abstract This study examined the effect of cholesterol esterase (CE) on the degradation of commercial poly(Ether Urethane) (PEU) and poly(carbonate Urethane) (PCU). Unstrained PEU and PCU films were incubated in 400 U/mL CE solution or a buffer control for 36 days. The study used a concentration of cholesterol esterase that was considerably higher than the estimated physiological level in order to accelerate degradation. However, characterization of treated polyUrethane films with SEM, attenuated total reflectance Fourier transform infrared (ATR-FTIR) and GPC analysis revealed only a small loss in surface soft segment content. Comparison with implanted PEU and PCU films led to the conclusion that any effect of enzymatic hydrolysis was confined to the immediate surface, and the magnitude of the effect was too small to contribute significantly to in vivo degradation. The study confirmed that oxidation, rather than enzymatic hydrolysis, is the primary mechanism responsible for the observed biodegradation of PEU and PCU. The oxidative H 2 O 2 /CoCl 2 treatment continues to accurately predict the long-term biostability of polyUrethanes.
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Enzymatic degradation of poly(Ether Urethane) and poly(carbonate Urethane) by cholesterol esterase
Biomaterials, 2006Co-Authors: Elizabeth M. Christenson, Sachin Patel, James M Anderson, Anne HiltnerAbstract:This study examined the effect of cholesterol esterase (CE) on the degradation of commercial poly(Ether Urethane) (PEU) and poly(carbonate Urethane) (PCU). Unstrained PEU and PCU films were incubated in 400 U/mL CE solution or a buffer control for 36 days. The study used a concentration of cholesterol esterase that was considerably higher than the estimated physiological level in order to accelerate degradation. However, characterization of treated polyUrethane films with SEM, attenuated total reflectance Fourier transform infrared (ATR-FTIR) and GPC analysis revealed only a small loss in surface soft segment content. Comparison with implanted PEU and PCU films led to the conclusion that any effect of enzymatic hydrolysis was confined to the immediate surface, and the magnitude of the effect was too small to contribute significantly to in vivo degradation. The study confirmed that oxidation, rather than enzymatic hydrolysis, is the primary mechanism responsible for the observed biodegradation of PEU and PCU. The oxidative H2O2/CoCl2 treatment continues to accurately predict the long-term biostability of polyUrethanes. © 2006 Elsevier Ltd. All rights reserved.
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oxidative mechanisms of poly carbonate Urethane and poly Ether Urethane biodegradation in vivo and in vitro correlations
Journal of Biomedical Materials Research Part A, 2004Co-Authors: Elizabeth M. Christenson, James M Anderson, Anne HiltnerAbstract:This study used an in vitro environment that simulated the microenvironment at the adherent cell-material interface to reproduce and accelerate the biodegradation of poly(Ether Urethane) (PEU) and poly(carbonate Urethane)(PCU). PolyUrethane films were treated in vitro for 24 days in 20% hydrogen peroxide/0.1 M cobalt chloride solution at 37°C. Characterization with ATR-FTIR and SEM showed soft segment and hard segment degradation consistent with the chemical changes observed after long-term in vivo treatment. Overall, the PCU underwent less degradation and the degraded surface layer was much thinner than PEU. Nevertheless, the results supported a common oxidation mechanism for biodegradation of these polymers. The observed in vitro degradation was inhibited by adding an antioxidant to the polyUrethane film. Our findings further support the use of the in vitro H 2 O 2 /CoCl 2 system in evaluating the biostability of polyUrethanes under accelerated conditions.
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Oxidative mechanisms of poly(carbonate Urethane) and poly(Ether Urethane) biodegradation: In vivo and in vitro correlations
Journal of Biomedical Materials Research - Part A, 2004Co-Authors: Elizabeth M. Christenson, James M Anderson, Anne HiltnerAbstract:This study used an in vitro environment that simulated the microenvironment at the adherent cell-material interface to reproduce and accelerate the biodegradation of poly(Ether Urethane) (PEU) and poly(carbonate Urethane) (PCU). PolyUrethane films were treated in vitro for 24 days in 20% hydrogen peroxide/0.1 M cobalt chloride solution at 37 degrees C. Characterization with ATR-FTIR and SEM showed soft segment and hard segment degradation consistent with the chemical changes observed after long-term in vivo treatment. Overall, the PCU underwent less degradation and the degraded surface layer was much thinner than PEU. Nevertheless, the results supported a common oxidation mechanism for biodegradation of these polymers. The observed in vitro degradation was inhibited by adding an antioxidant to the polyUrethane film. Our findings further support the use of the in vitro H(2)O(2)/CoCl(2) system in evaluating the biostability of polyUrethanes under accelerated conditions.
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an ftir atr investigation of in vivo poly Ether Urethane degradation
Journal of Applied Polymer Science, 1992Co-Authors: Y Wu, James M Anderson, Anne Hiltner, C Sellitti, Gary A Lodoen, C R PayetAbstract:Surface degradation of implanted poly (Ether Urethane) s was studied quantitatively with a micro-ATR-FTIR technique. Substantial degradation was observed particularly in the soft segment at the α-carbon adjacent to the Ether linkage. The degradation caused changes in the concentration profiles of the soft-segment groups in the depth direction, and the affected depth was up to 10 microns after implantation for 10 weeks. Inhibition of degradation by antioxidants indicated the oxidative nature of degradation. An in vivo poly (Ether Urethane) degradation mechanism was proposed
James M Anderson - One of the best experts on this subject based on the ideXlab platform.
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enzymatic degradation of poly Ether Urethane and poly carbonate Urethane by cholesterol esterase
Biomaterials, 2006Co-Authors: Elizabeth M. Christenson, Sachin Patel, James M Anderson, Anne HiltnerAbstract:Abstract This study examined the effect of cholesterol esterase (CE) on the degradation of commercial poly(Ether Urethane) (PEU) and poly(carbonate Urethane) (PCU). Unstrained PEU and PCU films were incubated in 400 U/mL CE solution or a buffer control for 36 days. The study used a concentration of cholesterol esterase that was considerably higher than the estimated physiological level in order to accelerate degradation. However, characterization of treated polyUrethane films with SEM, attenuated total reflectance Fourier transform infrared (ATR-FTIR) and GPC analysis revealed only a small loss in surface soft segment content. Comparison with implanted PEU and PCU films led to the conclusion that any effect of enzymatic hydrolysis was confined to the immediate surface, and the magnitude of the effect was too small to contribute significantly to in vivo degradation. The study confirmed that oxidation, rather than enzymatic hydrolysis, is the primary mechanism responsible for the observed biodegradation of PEU and PCU. The oxidative H 2 O 2 /CoCl 2 treatment continues to accurately predict the long-term biostability of polyUrethanes.
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Enzymatic degradation of poly(Ether Urethane) and poly(carbonate Urethane) by cholesterol esterase
Biomaterials, 2006Co-Authors: Elizabeth M. Christenson, Sachin Patel, James M Anderson, Anne HiltnerAbstract:This study examined the effect of cholesterol esterase (CE) on the degradation of commercial poly(Ether Urethane) (PEU) and poly(carbonate Urethane) (PCU). Unstrained PEU and PCU films were incubated in 400 U/mL CE solution or a buffer control for 36 days. The study used a concentration of cholesterol esterase that was considerably higher than the estimated physiological level in order to accelerate degradation. However, characterization of treated polyUrethane films with SEM, attenuated total reflectance Fourier transform infrared (ATR-FTIR) and GPC analysis revealed only a small loss in surface soft segment content. Comparison with implanted PEU and PCU films led to the conclusion that any effect of enzymatic hydrolysis was confined to the immediate surface, and the magnitude of the effect was too small to contribute significantly to in vivo degradation. The study confirmed that oxidation, rather than enzymatic hydrolysis, is the primary mechanism responsible for the observed biodegradation of PEU and PCU. The oxidative H2O2/CoCl2 treatment continues to accurately predict the long-term biostability of polyUrethanes. © 2006 Elsevier Ltd. All rights reserved.
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oxidative mechanisms of poly carbonate Urethane and poly Ether Urethane biodegradation in vivo and in vitro correlations
Journal of Biomedical Materials Research Part A, 2004Co-Authors: Elizabeth M. Christenson, James M Anderson, Anne HiltnerAbstract:This study used an in vitro environment that simulated the microenvironment at the adherent cell-material interface to reproduce and accelerate the biodegradation of poly(Ether Urethane) (PEU) and poly(carbonate Urethane)(PCU). PolyUrethane films were treated in vitro for 24 days in 20% hydrogen peroxide/0.1 M cobalt chloride solution at 37°C. Characterization with ATR-FTIR and SEM showed soft segment and hard segment degradation consistent with the chemical changes observed after long-term in vivo treatment. Overall, the PCU underwent less degradation and the degraded surface layer was much thinner than PEU. Nevertheless, the results supported a common oxidation mechanism for biodegradation of these polymers. The observed in vitro degradation was inhibited by adding an antioxidant to the polyUrethane film. Our findings further support the use of the in vitro H 2 O 2 /CoCl 2 system in evaluating the biostability of polyUrethanes under accelerated conditions.
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Oxidative mechanisms of poly(carbonate Urethane) and poly(Ether Urethane) biodegradation: In vivo and in vitro correlations
Journal of Biomedical Materials Research - Part A, 2004Co-Authors: Elizabeth M. Christenson, James M Anderson, Anne HiltnerAbstract:This study used an in vitro environment that simulated the microenvironment at the adherent cell-material interface to reproduce and accelerate the biodegradation of poly(Ether Urethane) (PEU) and poly(carbonate Urethane) (PCU). PolyUrethane films were treated in vitro for 24 days in 20% hydrogen peroxide/0.1 M cobalt chloride solution at 37 degrees C. Characterization with ATR-FTIR and SEM showed soft segment and hard segment degradation consistent with the chemical changes observed after long-term in vivo treatment. Overall, the PCU underwent less degradation and the degraded surface layer was much thinner than PEU. Nevertheless, the results supported a common oxidation mechanism for biodegradation of these polymers. The observed in vitro degradation was inhibited by adding an antioxidant to the polyUrethane film. Our findings further support the use of the in vitro H(2)O(2)/CoCl(2) system in evaluating the biostability of polyUrethanes under accelerated conditions.
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an ftir atr investigation of in vivo poly Ether Urethane degradation
Journal of Applied Polymer Science, 1992Co-Authors: Y Wu, James M Anderson, Anne Hiltner, C Sellitti, Gary A Lodoen, C R PayetAbstract:Surface degradation of implanted poly (Ether Urethane) s was studied quantitatively with a micro-ATR-FTIR technique. Substantial degradation was observed particularly in the soft segment at the α-carbon adjacent to the Ether linkage. The degradation caused changes in the concentration profiles of the soft-segment groups in the depth direction, and the affected depth was up to 10 microns after implantation for 10 weeks. Inhibition of degradation by antioxidants indicated the oxidative nature of degradation. An in vivo poly (Ether Urethane) degradation mechanism was proposed
Sultan A Nasar - One of the best experts on this subject based on the ideXlab platform.
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novel hyperbranched poly aryl Ether Urethane s using ab2 type blocked isocyanate monomers and copolymerization with ab type monomers
Macromolecular Chemistry and Physics, 2008Co-Authors: Thiyagarajan Shanmugam, Sultan A NasarAbstract:A novel AB 2 -type blocked isocyanate monomer was synthesized which was de-blocked to provide a hyperbranched poly(aryl Ether Urethane). Copolymerization of this monomer with a functionally similar AB monomer yielded polymers with molecular weights in the range 8.0-310 kDa with a DB of 41-59% that underwent two-stage decomposition above 200 °C. The inherent viscosities of the polymers in DMF ranged from 0.09 to 1.10 dL g -1 . End-group modification of hyperbranched poly(aryl Ether Urethane)s was carried out with PEG monomethyl Ether and 1-decanol and affected the thermal properties and solubilities of the polymers. T g of the polymers was reduced significantly from 201 to 71°C upon incorporation of AB monomer in the copolymerization.
Yinong Wang - One of the best experts on this subject based on the ideXlab platform.
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controlled release of protein from biodegradable multi sensitive injectable poly Ether Urethane hydrogel
ACS Applied Materials & Interfaces, 2014Co-Authors: Xiaomeng Li, Yangyun Wang, Yinong Wang, Jiaming Chen, Guolin WuAbstract:The synthesis and characterization of multi-sensitive polymers for use as injectable hydrogels for controlled protein/drug delivery is reported. A series of biodegradable multi-sensitive poly(Ether-Urethane)s were prepared through a simple one-pot condensation of poly(ethylene glycol), 2,2′-dithiodiethanol, N-methyldiethanolamine, and hexamethylene diisocyanate. The sol-gel phase transition behaviors of the obtained copolymers were investigated. Experimental results showed that the aqueous medium comprising the multi-segment copolymers underwent a sol-to-gel phase transition with increasing temperature and pH. At a certain concentration, the copolymer solution could immediately change to a gel under physiological conditions (37 °C and pH 7.4), indicating their suitability as in situ injectable hydrogels in vivo. Insulin was used as a model protein drug for evaluation of the injectable hydrogels as a site-specific drug delivery system. The controlled release of insulin from the hydrogel devices was demonst...
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precise control of drug release from dually responsive poly Ether Urethane nanoparticles
RSC Advances, 2013Co-Authors: Yangyun Wang, Guolin Wu, Xiaomeng Li, Jiatong Chen, Yinong WangAbstract:A series of linear poly(Ether Urethane)s was synthesized based on alternating PEG-diisocyanate of different molecular weight and N-methyldiethanolamine containing ternary amino moieties. The molecular structures of the obtained copolymers were confirmed with nuclear magnetic resonance, Fourier transform infrared spectroscopy and gel permeation chromatography. In aqueous solution, the amphiphilic copolymers could self-assemble into nanoparticles, which showed temperature and pH dual-responsive character. The stimuli-responsive behavior was characterized by light transmission, dynamic light scattering, nuclear magnetic resonance, and transmission electron microscopy. The phase transition temperature (Tp) of the nanoparticles could be modulated by changing the molecular weight of the PEG segments. The encapsulation and release of doxorubicin (DOX) were investigated using the obtained polymeric nanoparticles as carriers. The in vitro experimental results showed that DOX release from the nanoparticles was significantly accelerated when it was conducted at a higher temperature and lower pH value. Importantly, only when the ambient temperature was higher than the corresponding Tp, the drug release could be remarkably enhanced by the pH decrease. The system showed a temperature-triggered pH-dependent drug release. Cell viability and microscopic observation of liver cells (HepG2 cells) treated with the DOX-loaded polymeric nanoparticles demonstrated that the therapeutic activity and the DOX distribution could be precisely controlled by the novel dual-responsive system.
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on off switchable drug release from multi responsive degradable poly Ether Urethane nanoparticles
Biomaterials Science, 2013Co-Authors: Yangyun Wang, Guolin Wu, Xiaomeng Li, Yinong WangAbstract:A novel on–off switchable drug-release system was developed based on a series of multi-responsive degradable poly(Ether Urethane)s. The multi-segmented poly(Ether Urethane)s were synthesized through a simple one-pot condensation polymerization of poly(ethylene glycol), 2,2′-dithiodiethanol, N-methyldiethanolamine and hexamethylene diisocyanate. The obtained amphiphilic copolymers could self-assemble into nanoparticles in aqueous solution, which were responsive to temperature, pH and redox potential with tailored phase-transition temperature. The whole process for the responsive behaviours of the poly(Ether Urethane) nanoparticles was confirmed by light transmission, dynamic light scattering, nuclear magnetic resonance and transmission electron microscopy. The nanoparticles could encapsulate hydrophobic drugs and showed a temperature-triggered accelerated and complete drug-release profile. The mechanism of the temperature-triggered multi-responsive accelerated drug release was also elucidated. These results presented the polymeric nanoparticles as an effective multi-responsive degradable nanocarrier to achieve on–off drug release.
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Synthesis, characterization and controlled drug release from temperature-responsive poly(Ether-Urethane) particles based on PEG-diisocyanates and aliphatic diols
Journal of Biomaterials Science-polymer Edition, 2013Co-Authors: Yangyun Wang, Guolin Wu, Xiaomeng Li, Yinong Wang, Jianbiao MaAbstract:A series of linear amphiphilic poly(Ether-Urethane)s with alternative hydrophilic/hydrophobic segments based on PEG-diisocyanates and aliphatic diols is developed. The molecular structures of the copolymers were confirmed with nuclear magnetic resonance, Fourier transform infrared spectra and gel permeation chromatography. Nanoparticles prepared by self-assembly of the resulting copolymers show sharp temperature-responsive phase transition. The phase transition temperature could be easily modulated by the length of hydrophilic or hydrophobic segments of the polymer. The mechanism of the temperature-responsive behaviour is discussed. In the presence of these obtained poly(Ether-Urethane)s, doxorubicin (DOX) could be dispersed into aqueous solution. The ratio of DOX release from polymeric particles increased sharply above the phase transition temperature, while the release was suppressed below the phase transition temperature. A controlled drug release can be achieved by changing the environmental temperatu...
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temperature triggered redox degradable poly Ether Urethane nanoparticles for controlled drug delivery
Journal of Materials Chemistry, 2012Co-Authors: Yangyun Wang, Guolin Wu, Xiaomeng Li, Jiatong Chen, Yinong WangAbstract:A series of biodegradable poly(Ether Urethane)s that responded to changes in temperature and redox potential was synthesized via a facile one-pot method. The amphiphilic poly(Ether Urethane)s were comprised of 2,2′-dithiodiethanol, hydrophobic hexamethylene diisocyanate and hydrophilic poly(ethylene glycol) (PEG) segments. The phase transition temperature (Tp) of the prepared poly(Ether Urethane)s in aqueous solution could be easily controlled by changing the length of the PEG segment or the ratio of PEG to 2,2′-dithiodiethanol and it could be used to trigger the redox-degradable behavior. The redox-responsive disulfide bonds in the polymers could be cleaved in the presence of glutathione (GSH) when the temperature was above Tp, while the degradation was inhibited below Tp. The doxorubicin (DOX)-loaded poly(Ether Urethane) nanoparticles were prepared in order to investigate their stimuli-responsive release. These nanoparticles also showed a temperature-triggered redox-degradable release profile. Toxicity tests showed that the blank nanoparticles had no toxicity, whereas the DOX-loaded nanoparticles showed high cytotoxicity for liver hepatocellular cells (HepG2). Microscopic observations also revealed that the DOX molecules within the poly(Ether Urethane) nanoparticles could be released into HepG2 cells in the presence of higher temperature and GSH.
Elizabeth M. Christenson - One of the best experts on this subject based on the ideXlab platform.
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enzymatic degradation of poly Ether Urethane and poly carbonate Urethane by cholesterol esterase
Biomaterials, 2006Co-Authors: Elizabeth M. Christenson, Sachin Patel, James M Anderson, Anne HiltnerAbstract:Abstract This study examined the effect of cholesterol esterase (CE) on the degradation of commercial poly(Ether Urethane) (PEU) and poly(carbonate Urethane) (PCU). Unstrained PEU and PCU films were incubated in 400 U/mL CE solution or a buffer control for 36 days. The study used a concentration of cholesterol esterase that was considerably higher than the estimated physiological level in order to accelerate degradation. However, characterization of treated polyUrethane films with SEM, attenuated total reflectance Fourier transform infrared (ATR-FTIR) and GPC analysis revealed only a small loss in surface soft segment content. Comparison with implanted PEU and PCU films led to the conclusion that any effect of enzymatic hydrolysis was confined to the immediate surface, and the magnitude of the effect was too small to contribute significantly to in vivo degradation. The study confirmed that oxidation, rather than enzymatic hydrolysis, is the primary mechanism responsible for the observed biodegradation of PEU and PCU. The oxidative H 2 O 2 /CoCl 2 treatment continues to accurately predict the long-term biostability of polyUrethanes.
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Enzymatic degradation of poly(Ether Urethane) and poly(carbonate Urethane) by cholesterol esterase
Biomaterials, 2006Co-Authors: Elizabeth M. Christenson, Sachin Patel, James M Anderson, Anne HiltnerAbstract:This study examined the effect of cholesterol esterase (CE) on the degradation of commercial poly(Ether Urethane) (PEU) and poly(carbonate Urethane) (PCU). Unstrained PEU and PCU films were incubated in 400 U/mL CE solution or a buffer control for 36 days. The study used a concentration of cholesterol esterase that was considerably higher than the estimated physiological level in order to accelerate degradation. However, characterization of treated polyUrethane films with SEM, attenuated total reflectance Fourier transform infrared (ATR-FTIR) and GPC analysis revealed only a small loss in surface soft segment content. Comparison with implanted PEU and PCU films led to the conclusion that any effect of enzymatic hydrolysis was confined to the immediate surface, and the magnitude of the effect was too small to contribute significantly to in vivo degradation. The study confirmed that oxidation, rather than enzymatic hydrolysis, is the primary mechanism responsible for the observed biodegradation of PEU and PCU. The oxidative H2O2/CoCl2 treatment continues to accurately predict the long-term biostability of polyUrethanes. © 2006 Elsevier Ltd. All rights reserved.
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oxidative mechanisms of poly carbonate Urethane and poly Ether Urethane biodegradation in vivo and in vitro correlations
Journal of Biomedical Materials Research Part A, 2004Co-Authors: Elizabeth M. Christenson, James M Anderson, Anne HiltnerAbstract:This study used an in vitro environment that simulated the microenvironment at the adherent cell-material interface to reproduce and accelerate the biodegradation of poly(Ether Urethane) (PEU) and poly(carbonate Urethane)(PCU). PolyUrethane films were treated in vitro for 24 days in 20% hydrogen peroxide/0.1 M cobalt chloride solution at 37°C. Characterization with ATR-FTIR and SEM showed soft segment and hard segment degradation consistent with the chemical changes observed after long-term in vivo treatment. Overall, the PCU underwent less degradation and the degraded surface layer was much thinner than PEU. Nevertheless, the results supported a common oxidation mechanism for biodegradation of these polymers. The observed in vitro degradation was inhibited by adding an antioxidant to the polyUrethane film. Our findings further support the use of the in vitro H 2 O 2 /CoCl 2 system in evaluating the biostability of polyUrethanes under accelerated conditions.
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Oxidative mechanisms of poly(carbonate Urethane) and poly(Ether Urethane) biodegradation: In vivo and in vitro correlations
Journal of Biomedical Materials Research - Part A, 2004Co-Authors: Elizabeth M. Christenson, James M Anderson, Anne HiltnerAbstract:This study used an in vitro environment that simulated the microenvironment at the adherent cell-material interface to reproduce and accelerate the biodegradation of poly(Ether Urethane) (PEU) and poly(carbonate Urethane) (PCU). PolyUrethane films were treated in vitro for 24 days in 20% hydrogen peroxide/0.1 M cobalt chloride solution at 37 degrees C. Characterization with ATR-FTIR and SEM showed soft segment and hard segment degradation consistent with the chemical changes observed after long-term in vivo treatment. Overall, the PCU underwent less degradation and the degraded surface layer was much thinner than PEU. Nevertheless, the results supported a common oxidation mechanism for biodegradation of these polymers. The observed in vitro degradation was inhibited by adding an antioxidant to the polyUrethane film. Our findings further support the use of the in vitro H(2)O(2)/CoCl(2) system in evaluating the biostability of polyUrethanes under accelerated conditions.