Hydrolytic degradation of ROMP thermosetting materials catalysed by bio-derived acids and enzymes: from networks to linear materials

This paper reports the first example of degradable ROMP thermosetting materials catalysed by bio-derived acids and cutinase from Thermobifida cellulosilytica (Thc_Cut1). The ROMP thermosetting materials are based on norbornene dicarboximides containing acetal ester groups only in the crosslinking moiety. The insoluble cross-linked materials were subjected to acid-catalysed hydrolysis using bio-derived acetic and citric acids as well as enzymatic degradation using Thc_Cut1, resulting in the materials becoming completely soluble in dichloromethane. 1H NMR and rheological analysis performed on materials after acid-catalysed hydrolysis showed characteristics indistinguishable to those of the linear polymer analogues. These analyses confirmed the cleavage of the crosslinking moiety upon degradation with the main backbone chains remaining intact. The glass transition temperatures of the polymer materials after acid-catalysed hydrolysis were the same as those observed for the linear polymer analogues. TGA showed that the cross-linked polymers were thermally stable to 150 °C, beyond which they showed weight losses due to the thermal cleavage of the acetal ester linkages

Enzymatic surface functionalisation of lignocellulosic materials with tannins for enhancing antibacterial properties

10 páginas, 11 figuras, 2 tablas -- PAGS nros. 1072-1081Grafting natural antibacterial phenols onto lignocellulosic materials is an environmentally friendly way of imparting antibacterial properties to the substrates. In the present investigation, wood veneer and pulp were treated with tannins in the presence or absence of laccase. Treatments with hydrolysable tannins significantly improved the antibacterial resistance of veneers and paper made from tannin-treated pulp against a Gram-positive bacterium (Staphylococcus aureus) while a more modest protective effect was observed against a Gram-negative bacterium (Escherichia coli). Condensed tannin improved the antibacterial resistance against S. aureus, albeit less than hydrolysable tannin, but had little effect on E. coli. A cationic condensed tannin derivative bearing a quaternary amino group provided far better resistance to pulp against S. aureus and E. coli than the corresponding unmodified condensed tannin. These findings agree with the minimal inhibitory concentrations (MICs) of the tannins and their reactivities toward laccase as determined by O2 consumption measurements. Due to a better retention of tannins via covalent bonding, treatments with laccase usually resulted in greater antibacterial effects than those without laccase. LC–MS investigations with monomeric tannin and lignin model compounds showed that covalent bonding of tannin to lignin via radical coupling occurred in the presence of laccase.European Union Biorenew Project (6th Framework Program, FP6-2004-NMP-NI-4). Austrian Academic Exchange Service (OEAD) for financial supportPeer reviewe

Assessment of infection in chronic wounds based on the monitoring of elastase, lysozyme and myeloperoxidase activities

Infection in wounds affects about 2% of the population in developed countires at least once in their lifetime, and the lack of tools for its rapid diagnosis is still a problem 1. Standard procedures of infection detection include the judgement of the classical clinical signs, the detection of signals specific to secondary wounds, or the quantification of the microbial load 2–5. The determination of the microbial load is a time-consuming standard procedure, although the presence of microbes per se is not indicative of infection 2

Laccase catalyzed covalent coupling of fluorophenols increases lignocellulose surface hydrophobicity

7 páginas, 6 figuras, 2 tablas -- PAGS. nros. 2793-2799This work presents for the first time the mechanistic evidence of a laccase-catalyzed method of covalently grafting hydrophobicity enhancing fluorophenols onto Fagus sylvatica veneers. Coupling of fluorophenols onto complex lignin model compounds guaiacylglycerol beta-guaiacyl ether and syringylglycerol beta-guaiacyl ether was demonstrated by LC-MS and NMR. Laccase-mediated coupling increased binding of 4-[4-(trifluoromethyl)phenoxy]phenol (4,4-F3MPP) and 4-(trifluoromethoxy)phenol (4-F3MP) to veneers by 77.1% and 39.2%, respectively. XPS studies showed that laccase-catalyzed grafting of fluorophenols resulted in a fluorine content of 6.39% for 4,4-F3MPP, 3.01% for 4-F3MP and 0.26% for 4-fluoro-2-methylphenol (4,2-FMP). Grafting of the fluorophenols 4,2-FMP, 4-F3MP and 4,4-F3MPP led to a 9.6%, 28.6% and 65.5% increase in hydrophobicity, respectively, when compared to treatments with the respective fluorophenols in the absence of laccase, in good agreement with XPS data.This work has been supported by the Austrian Academic Exchange Service (OEAD) and European Union Biorenew Project [Sixth Framework Programme (FP6-2004-NMP-NI-4)].Peer reviewe

Laccase catalyzed covalent coupling of fluorophenols increases lignocellulose surface hydrophobicity

7 páginas, 6 figuras, 2 tablas -- PAGS. nros. 2793-2799This work presents for the first time the mechanistic evidence of a laccase-catalyzed method of covalently grafting hydrophobicity enhancing fluorophenols onto Fagus sylvatica veneers. Coupling of fluorophenols onto complex lignin model compounds guaiacylglycerol beta-guaiacyl ether and syringylglycerol beta-guaiacyl ether was demonstrated by LC-MS and NMR. Laccase-mediated coupling increased binding of 4-[4-(trifluoromethyl)phenoxy]phenol (4,4-F3MPP) and 4-(trifluoromethoxy)phenol (4-F3MP) to veneers by 77.1% and 39.2%, respectively. XPS studies showed that laccase-catalyzed grafting of fluorophenols resulted in a fluorine content of 6.39% for 4,4-F3MPP, 3.01% for 4-F3MP and 0.26% for 4-fluoro-2-methylphenol (4,2-FMP). Grafting of the fluorophenols 4,2-FMP, 4-F3MP and 4,4-F3MPP led to a 9.6%, 28.6% and 65.5% increase in hydrophobicity, respectively, when compared to treatments with the respective fluorophenols in the absence of laccase, in good agreement with XPS data.This work has been supported by the Austrian Academic Exchange Service (OEAD) and European Union Biorenew Project [Sixth Framework Programme (FP6-2004-NMP-NI-4)].Peer reviewe

Sensor materials for the detection of human neutrophil elastase and cathepsin G activity in wound fluid

Human neutrophil elastase (HNE) and cathepsin G (CatG) are involved in the pathogenesis of a number of inflammatory disorders. These serine proteinases are released by neutrophils and monocytes in case of infection. Wound infection is a severe complication regarding wound healing causing diagnostic and therapeutic problems. In this study we have shown the potential of HNE and CatG to be used as markers for early detection of infection. Significant differences in HNE and CatG levels in infected and non-infected wound fluids were observed. Peptide substrates for these two enzymes were successfully immobilised on different surfaces, including collagen, modified collagen, polyamide polyesters and silica gel. HNE and CatG activities were monitored directly in wound fluid via hydrolysis of the chromogenic substrates. Infected wound fluids led to significant higher substrate hydrolysis compared with non-infected ones. These different approaches could be used for the development of devices which are able to detect elevated enzyme activities before manifestation of infection directly on bandages. This would allow a timely intervention by medical doctors thus preventing severe infections.Peer Reviewe