Search

Enzymatic polymerization of lignosulfonate (LS) has a high potential for various applications ranging from coatings to adhesives. Here, the effect of different ions in low concentrations on enzymatic polymerization of LS was investigated, including salt solutions consisting of mono‐ and dicarboxylic acids, sulfate, phosphate and chloride with sodium as counter ion. LS polymerization was followed by viscometry and size exclusion (SEC) chromatography. Interestingly, there was only a small effect of ions on the activity of the laccase on standard substrate ABTS, while the effect on polymerization of LS was substantially different. The presence of acetate led to a 39 % higher degree of polymerization (DP) for LS. Small angle X‐ray scattering (SAXS) revealed that the structure of the enzyme was largely unaffected by the ions, while the determination of the zeta potential showed that those ions conveying higher negative surface charges onto LS particles showed lower DPs, than those not affecting the surface charge. Further, electron paramagnetic resonance (EPR) spectroscopy showed 5‐times higher intensity in phenoxyl radicals for the monovalent ions compared to the divalent ones. It was concluded that the DPs of LS could be tuned in the presence of certain ions, by facilitating the interaction between the laccase substrate‐binding site and the LS molecules. [ABSTRACT FROM AUTHOR]

Urinary catheters expose patients to a high risk of acquiring nosocomial infections. To prevent this risk of infection, cellobiose dehydrogenase (CDH), an antimicrobial enzyme able to use various oligosaccharides as electron donors to produce hydrogen peroxide using oxygen as an electron acceptor, was covalently grafted onto plasma-activated urinary polydimethylsiloxane (PDMS) catheter surfaces. Successful immobilization of CDH on PDMS was confirmed by Fourier transformed-infrared spectrometry and production of H2O2. The CDH functionalized PDMS surfaces reduced the amount of viable Staphylococcus aureus by 60%, total biomass deposited on the surface by 30% and 70% of biofilm formation. The immobilized CDH was relatively stable in artificial urine over 16 days, retaining 20% of its initial activity. The CDH coated PDMS surface did not affect the growth and physiology of HEK 239 and RAW 264,7 mammalian cells. Therefore this new CDH functionalized catheter system shows great potential for solving the current problems associated with urinary catheters. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1448-1456, 2016. [ABSTRACT FROM AUTHOR]

A large percentage of the population suffers from impaired wound healing related problems that are partly attributed to the continuous production and exposure of wounds to reactive species. The skin is prone to many adverse effects when e.g. damaged, exposed to ionizing UV radiation and/or environmental reactive pollutants. The reactive molecular species attacking the skin in excessive quantities quickly overwhelm tissue antioxidants and other oxidant-degrading pathways. The uncontrolled release of these reactive species is involved in the oxidation of biomolecules including lipids which in turn results in a number of human skin disorders. Phenolic antioxidants are emerging as contenders removing reactive species produced in these chronic wounds, thus accelerating the healing process. Building on this knowledge, a novel physiologically active wound dressing containing both phenolic antioxidants and an enzyme (cellobiose dehydrogenase) for the continuous recycling of oxidized phenolic antioxidants has been developed recently. This novel approach should protect the wound from damage and will help to create ideal conditions for the successful healing of chronic wounds. [ABSTRACT FROM AUTHOR]

Novel multifunctional bioresponsive gelatin and alginate based hydrogels with in-built antioxidant regenerating system and antimicrobial properties were successfully synthesized. These hydrogels are based on the versatile reactions catalyzed by cellobiose dehydrogenase (CDH). CDH uses cellobiose and cello-oligosacharides as electron donors to reduce oxidized phenolic antioxidants, quinones, or molecular oxygen to H2O2 (a well-known antimicrobial agent). The antioxidant regenerating system consisting of CDH and cellobiose increased the ability of catechol to quench nitric oxide (NO), superoxide (O2−) and hydroxyl radicals (OH•) in solution and when incorporated into hydrogels. The CDH loaded into the hydrogels free of oxidized phenolic antioxidants and quinones reduced molecular to H2O2 resulting in the complete inhibition of the growth of Stapylococcus aeureus, Bacillus subtilis, Pseudomonas putida, Escherichia coli and Cellulomonasmicrobium cellulans. This study therefore presents a new concept for synthesizing multifunctional bioresponsive chronic wound dressing polymers with in-built continuous antioxidant system able to continuously quench [reactive oxygen species (ROS) and reactive nitrogen species (RNOS)], and antimicrobial properties able to prevent microbial colonization of wound. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2013. [ABSTRACT FROM AUTHOR]

Accurate monitoring of the antioxidant status or of oxidative stress in patients is still a big challenge in clinical laboratories. This study investigates the possibility of applying a newly developed total antioxidant capacity assay method based on laccase or peroxidase oxidized syringaldazine [Tetramethoxy azobismethylene quinone ( TMAMQ)] which is referred to here as Syrin OX, as a diagnostic tool for monitoring both oxidative stress and antioxidant status in patients. Attempts to adapt the Randox total antioxidant procedure [simultaneous incubation of the radical generating system (metmyoglobin and H2O2) and antioxidant sample] for Syrin OX were abandoned after it was discovered that the H2O2 reacted with enzymatically generated TMAMQ and ABTS radicals at a rate of 6.4 × 10−2/μM/s and 5.7 × 10−3/μM/s respectively. Thus this study for the first time demonstrates the negative effects of H2O2 in the Randox system. This leads to erroneous results because the total antioxidant values obtained are the sum of radicals reduced by antioxidants plus those reacting with the radical generating system. Therefore they should be avoided not only for this particular method but also when using other similar methods. Consequently, Syrin OX is best applied using a three-step approach involving, production of TMAMQ, recovery and purification (free from enzyme and other impurities) and then using TMAMQ for measuring the total antioxidant capacity of samples. Using this approach, the reaction conditions for application of Syrin OX when measuring the total antioxidant capacity of plasma sample were determined to be 50% (v/v) ethanol/50 mM sodium succinate buffer pH 5.5, between 20 and 25 °C for at least 1 h. [ABSTRACT FROM AUTHOR]

Eur J Clin Invest 2012; 42 (4): 432-438 Abstract Background The human body is constantly exposed to a large variety of reactive oxygen species that are implicated in many pathophysiological conditions (atherosclerosis, cancer, neurodegenerative diseases etc.). Monitoring the antioxidant status of biological fluids could be used as an early warning sign 'biomarker' of possible disease onset. However, although several methods have been developed, questionable sensitivity, unreliability and non-reproducibility hamper all, making it difficult to have an internationally accepted standardized method. This study presents and demonstrates the remarkable ability of a newly developed antioxidant capacity assay method based on tetramethoxy azobismethylene quinone (TMAMQ) to measure the total antioxidant capacity of serum samples using three complimentary approaches. Design Using an UV-Vis spectroscopy and oxygen sensor, the reduction of TMAMQ by serum antioxidants was compared to either the formation of syringaldazine or consumption of oxygen. Results After adding a fraction of human serum, 4·01 μM TMAMQ was reduced to syringaldazine from a stock of 11·74 μM TMAMQ. Subsequent addition of laccase resulted in the oxidation of the formed syringaldazine back to TMAMQ resulting in an increase in TMAMQ concentration to 11·71 μM (re-establishing almost the same initial concentration of TMAMQ) while consuming 1·04 μM molecular oxygen. Conclusions The reduction of TMAMQ by serum samples is directly proportional to the consumption of oxygen and the formation of syringaldazine. This means that either the formation of syringaldazine or oxygen consumption can be used to validate or confirm data obtained through monitoring TMAMQ reduction. [ABSTRACT FROM AUTHOR]

Laccase enzymes are multicopper oxidases capable of oxidizing different compounds. However, to be able to use this biocatalyst for industrial applications, their immobilization is needed. The present work investigates the immobilization of Myceliophthora thermophila laccase (MtL) on monodisperse microspheres of poly(glycidyl methacrylate) (PGMA) to be used in azinphos‐methyl degradation. The immobilization was optimized to achieve the highest activity of the immobilized enzyme. As result, the protein load obtained was 2.5 mg protein g−1 carrier (35 U g−1 of carrier). The immobilized enzymes showed a broadened pH and temperature range of optimum activity and significantly improved the storage and operational stability. Finally, the complete degradation of azinphos‐methyl using immobilized laccase was achieved after 1 h of reaction. The collected data indicate that the immobilization of MtL on PGMA microspheres is an excellent alternative to improve biochemical properties in the enzyme and to allow their efficient use in pesticides degradation. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47417. [ABSTRACT FROM AUTHOR]