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Cysteine immobilisation on the polyethylene terephthalate surfaces and its effect on the haemocompatibility.

ABSTRACT: Nitric oxide (NO) is an important signalling molecule involved in haemostasis. NO, present as endogenous S-nitrosothiols, is released by cysteine through a transnitrosation reaction. To exploit this mechanism, cysteine was immobilised onto the different carboxylated polyethylene terephthalate (PET) surfaces using 1-step EDC (1-ethyl-3-(3-dimethylaminopropyl) carbodiimide) crosslinking mechanism. Immobilised cysteine concentration and NO release were dependent on the surface carboxyl density. Stability studies showed that the immobilised cysteine concentration and NO release reduced within 6 h. Immobilisation of cysteine derivatives eliminated the possibility of formation of polycysteine and its electrostatic interaction with the carboxylated PET. The immobilised cysteine concentration did not recover after DTT treatment, eliminating the possibility of disulphide bond formation. Further, cysteine was immobilised using a 2-step EDC crosslinking mechanism. Although the cysteine concentration reduced during stability studies, it recovered upon DTT treatment, indicating that cysteine forms amide bonds with the carboxylated PET and the observed decrease in cysteine concentration is probably due to the formation of disulphide bonds. The haemocompatibility of the cysteine immobilised PET surfaces showed similar results compared to the carboxylated PET. The loss of thiol groups due to the disulphide bond restricts the transnitrosation reaction. Hence, these materials can be used primarily in short-term applications.

SUBMITTER: Ramachandran B

PROVIDER: S-EPMC6853964 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundIncreasing experimental and clinical evidence suggests that illumination of the skin with relatively low intensity light may lead to therapeutic results such as reduced pain or improved wound healing. The goal of this study was to evaluate prospectively whether socks made from polyethylene terephthalate (PET) incorporating optically active particles (Celliant) ameliorates chronic foot pain resulting from diabetic neuropathy or other disorders. Such optically modified fiber is thought to modify the illumination of the skin in the visible and infrared portions of the spectrum, and consequently reduce pain.MethodsA double-blind, randomized trial with 55 subjects (38 men, 17 women) enrolled (average age 59.7 +/- 11.9 years), 26 with diabetic neuropathy and 29 with other pain etiologies. Subjects twice completed the Visual Analogue Scale (VAS), Brief Pain Inventory (BPI), McGill Pain Questionnaire (MPQ), and SF-36 a week apart (W(1+2)) before receiving either control or Celliant socks. The same questionnaires were answered again one and two weeks (W(3+4)) later. The questionnaires provided nine scores for analyzing pain reduction: one VAS score, two BPI scores, five MPQ scores, and the bodily pain score on the SF-36. Mean W(1+2) and W(3+4) scores were compared to measure pain reduction.ResultsMore pain reduction was reported by Celliant subjects for 8 of the 9 pain questions employed, with a significant (p = 0.043) difference between controls and Celliant for McGill question III. In neuropathic subjects, Celliant caused more pain reduction in 6 of the 9 questions, but not significantly. In non-neuropathic subjects 8 of 9 questions showed more pain reduction with the Celliant socks.ConclusionSocks with optically modified PET (Celliant) appear to have a beneficial impact on chronic foot pain. The mechanism could be related to the effects seen with illumination of tissues with visible and infrared light.Trial registrationClinicalTrials.gov NCT00458497.

Project description:Biodegradation of terephthalate (TPA) is a highly desired catabolic process for the bacterial utilization of this polyethylene terephthalate (PET) depolymerization product, but to date, the structure of terephthalate dioxygenase (TPDO), a Rieske oxygenase (RO) that catalyzes the dihydroxylation of TPA to a cis-diol, is unavailable. In this study, we characterized the steady-state kinetics and first crystal structure of TPDO from Comamonas testosteroni KF1 (TPDOKF1). TPDOKF1 exhibited substrate specificity for TPA (kcat/Km = 57 ± 9 mM-1 s-1). The TPDOKF1 structure harbors characteristic RO features as well as a unique catalytic domain that rationalizes the enzyme's function. The docking and mutagenesis studies reveal that its substrate specificity for TPA is mediated by the Arg309 and Arg390 residues, positioned on opposite faces of the active site. Additionally, residue Gln300 is also proven to be crucial for the activity, as its mutation to alanine decreases the activity (kcat) by 80%. This study delineates the structural features that dictate the substrate recognition and specificity of TPDO. IMPORTANCE Global plastic pollution has become the most pressing environmental issue. Recent studies on enzymes depolymerizing polyethylene terephthalate plastic into terephthalate (TPA) show some potential for tackling this. Microbial utilization of this released product, TPA, is an emerging and promising strategy for waste-to-value creation. Research in the last decade has identified terephthalate dioxygenase (TPDO) as being responsible for initiating the enzymatic degradation of TPA in a few Gram-negative and Gram-positive bacteria. Here, we determined the crystal structure of TPDO from Comamonas testosteroni KF1 and revealed that it possesses a unique catalytic domain featuring two basic residues in the active site to recognize TPA. Biochemical and mutagenesis studies demonstrated the crucial residues responsible for the substrate specificity of this enzyme.

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Cysteine immobilisation on the polyethylene terephthalate surfaces and its effect on the haemocompatibility.

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