Enzyme-induced biodegradation of polycarbonate-polyurethanes: Dependence on hard-segment chemistry

Abstract

Polycarbonate urethanes (PCNUs) have been used as a replacement for traditional biomedical polyether-urethanes due to their reported resistance to oxidative biodegradation. However, relatively little is known about their hydrolytic stability in the presence of inflammatory derived enzymes. This has in part motivated the current study relating to the effect of hard segment chemistry and the microdomain structures generated by such chemistry, on the cholesterol esterase (CE) catalyzed hydrolysis of PCNUs. The bulk structures of the studied materials were characterized using gel permeation chromatography (GPC), differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS), Fourier transform infrared spectroscopy (FTIR) for their bulk structures, and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) for their subsurface structures. 14C-labeled PCNUs were incubated with CE (400 units/mL), for a period of 10 weeks (pH 7.0 at 37 degrees C), and radiolabel release was used to monitor the degradation. The results showed that all of the polymers synthesized in this study were susceptible to CE-catalyzed hydrolytic degradation, and that the extent of degradation was highly dependent on the nature of hard segment interactions within the polymer and at the surface. More specifically, the degree of phase separation and soft segment crystallinity were found to be less important in comparison to the hydrogen bonding among the carbonate and urethane linkages. The rank of the different chemical groups' susceptibility to hydrolysis was as follows: nonhydrogen bonded carbonate > nonhydrogen bonded urethane > hydrogen bonded carbonate > hydrogen bonded urethane. The findings suggest that the degree of hydrogen bonding, when processed into a polyurethane material could be an important parameter to consider in the design of new biostable polyurethane products.

Characterization of a biodegradable electrospun polyurethane nanofiber scaffold: Mechanical properties and cytotoxicity

“…The T v hard-segment melting transition temperature remained relatively unchanged near 93°C across all samples and was unaffected by the pre-wetting process. This temperature corresponds to the crystalline segments containing polar urethane groups, which are anticipated to be the most stable regions of the polymer due to the potential of extensive hydrogen bonding within this domain [40]. Likewise, the T g values for polycarbonate near À36°C remained relatively unchanged.…”

“…5) from approximately 51°C for T iii to 68°C for T iv . The shift of this polycarbonate (PCN) polymer phase towards higher temperatures suggests a loss of PCN phase purity (pure polycarbonate has a melt transition temperature of 45°C [40]) and an increase in phase mixing of hard segment with the soft segment content. More evidence that the pre-wetting process disrupted the crystalline state of the soft segment PCN phase was observed near 33°C (T ii , Fig.…”

“…Efforts in the 1980s and 1990s had previously been directed at producing biostable polyurethanes; however, in the past decade, the focus has shifted to developing bioactive/biocompatible and biodegradable polyurethanes for the purpose of tissue engineering or regeneration [30,39]. In this study, PU was synthesized, as has been described [40], with hexane diisocyanate:polycarbonate diol:butane diol in a molar ratio of 3:2:1. In addition, an ADO additive was synthesized through the reaction of lysine diisocyanate, polytetramethylene oxide and hydroxyethyl methacrylate (HEMA), followed by subsequent hydrolysis of ester groups on the lysine and HEMA moieties [33].…”

Enzymatic Synthesis and Chemical Recycling of Poly(carbonate‐urethane)

“…[10] A new class of polycarbonate-based polyurethanes has attracted interest in the field of biomaterials due in part to their mechanical properties similar to those of conventional polyurethanes and to a relatively enhanced hydrolytic stability and oxidative stability. [11][12][13][14][15][16] Recently, it was reported that polycarbonate-based polyurethane materials have a strong sensitivity towards hydrolysis when changes are made to their hard segment content or chemistry or both. [17] In this report, a biodegradable low-molecular weight diurethanediol was combined with the carbonate linkage Summary: Novel enzymatically recyclable poly(carbonateurethane) consisting of a diurethane moiety as a hard segment and a carbonate linkage as an enzymatically cleavable unit was prepared by the polycondensation of biodegradable diurethanediol and diethyl carbonate using lipase.…”

“…1 H NMR spectra were recorded with a Varian NMR 300 (300 MHz) spectrometer (Varian, Inc., CA, USA) in DMSO-d 6 with tetramethylsilane as an internal standard. 13 C NMR spectra were recorded with a JOEL Model JNM-LA300 (75 MHz) spectrometer (JOEL Ltd., Tokyo, Japan) in DMSOd 6 . The matrix-assisted laser desorption ionization time-offlight mass spectrometry (MALDI-TOF MS) was measured with Bruker Ultraflex mass spectrometer.…”