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

Abstract

Polycarbonate-based polyurethanes with varying hard segment contents were synthesized. The physical and chemical structures were characterized by using gel permeation chromatography, differential scanning calorimetry, water uptake testing, Fourier transform infrared, and attenuated total reflectance--Fourier transform infrared. The polymers were incubated with cholesterol esterase in a phosphate buffer solution at 37 degrees C over 10 weeks. A higher resistance to hydrolytic degradation was observed in polycarbonate-based urethanes with higher hard segment content. The analysis of the material structures revealed that the degradation of polycarbonate-based urethanes was preferentially initiated at non-hydrogen-bonded carbonates and urethanes. Although the crystallinity of the polycarbonate soft segment may contribute to reducing the hydrolytic degradation catalyzed by cholesterol esterase, it was found to be relatively minor in comparison to the importance of hydrogen bonding between the carbonate and urethane groups. These observations suggest that the biostability of polyurethanes and specifically polycarbonate-based polyurethanes can be improved by manipulating the degree of hydrogen bonding within the materials.

In vivo biostability of polymeric spine implants: retrieval analyses from a United States investigational device exemption study

“…8, thus the results are not presented here. Hydrolytic biodegradation [19] (evidenced by the formation of a carboxyl peak at 1,640 cm -1 ) was absent in the spectra of both outer and central fibers. The carboxyl indices of both outer and central fibers were all less than the detection limit of 5%; therefore, no structural chemical changes associated with hydrolytic biodegradation were identifiable in the explanted cords.…”

Study on degradation of a commercial rigid polyurethane foam used for fillingof process gas equipment.

“…The PU with the lowest concentration of hard segment and higher number of carbonyl groups was disposed on the surface, whereas the increase of hard segment concentration does lead to restrictions in polymer chain mobility. Biodegradation of polycarbonated polyether PUs by esterase activity is mostly dependent on the hard segment chemistry and size (Tang et al, 2001). As mentioned before, the functional groups on polyether PU surfaces play an important role in susceptibility of PU to biodegradation.…”

Assessment of aliphatic poly(ester-carbonate-urea-urethane)s potential as materials for biomedical application

“…Evaluation of direct cytotoxicity Additionally, to evaluate the cytotoxicity of tested materials, polymers were transferred to 12-well cell culture treated plates and pre-coated with collagen I (0.1 mg/mL, 2 h incubation). Then, on their surface a suspension of HaCaT cells (immortalized, human keratinocyte cell line) at a density of 1.2 × 10 4 cells/well was seeded and cultured in DMEM medium supplemented with 10% fetal bovine serum, 50 U/mL penicillin, and 50 mg/mL streptomycin at 37°C in a 5% CO 2 incubator for up to 72 h. At the indicated time points (24,48, and 72 h) optical images were collected in order to count the number of cells attached to the polymer surface. The number of cells at the surface of materials was compared to the number of cells growing on the surface of the cell culture plates.…”

“…A relatively new generation of polyurethanes used in medical devices are based on poly(carbonate-urethane)s (PCUs). According to in vitro and early in vivo studies, PCUs exhibit improved resistance to hydrolytic degradation and in vivo stress cracking compared to oligoester based medical grade polyurethanes [17][18][19][20][21][22][23][24]. Furthermore, according to the mechanism of hydrolytic degradation of PCUs [25], a decrease of pH is not observed, which leads to a much lower inflammation of the surrounding tissues.…”