The effect of oxidation on the enzyme-catalyzed hydrolytic biodegradation of poly(urethane)s
Why this work is in the frame
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Bibliographic record
Abstract
Although the biodegradation of polyurethanes (PU) by oxidative and hydrolytic agents has been studied extensively, few investigations have reported on the combination of their effects. Since neutrophils (PMN) arrive at an implanted device first and release HOCl, followed by monocyte-derived macrophages (MDM) which have potent esterase activities and oxidants of their own, the combined effect of oxidative and hydrolytic degradation on radiolabeled polycarbonate-polyurethanes (PCNU)s was investigated and compared to that of a polyester-PU (PESU) and a polyether-PU (PEU). The PCNUs were synthesized with PCN (MW = 1,000), and butanediol (14C-BD) and one of two diisocyanates, hexane-1,6-diisocyanate (14C-HDI) or methylene bis-p-phenyl diisocyanate (MDI). The PESU and PEU were synthesized using toluene-diisocyanate (14C-TDI), with polycaprolactone and polytetramethylene oxide as soft segments respectively, and ethylene diamine as the chain extender. The effect of pre-treatment with 0.1 mM HOC1 for 1 week on the HDI-based PCNUs and both TDI-based PUs resulted in a significant inhibition of radiolabel release (RR) elicited by cholesterol esterase (CE), when compared to buffer alone, whereas the MDI-based PCNU showed a small but significant increase. When PMN were activated on the HDI-based PCNU surface with phorbol myristate acetate (PMA), HOCl was released for 3 h, and was almost completely abolished by sodium azide (AZ). Simultaneously, the PMN-elicited RR, shown previously to be due to the esterolytic cleavage by serine proteases, was inhibited approximately 75% by PMA-activation of the cells, but significantly increased relative to the latter when AZ was added. Both in vitro oxidation by HOCl and the release of HOCI by PMN were associated with the inhibition of RR and suggest perturbations between oxidative and hydrolytic mechanisms of biodegradation.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.005 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it