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182 results on '"Guebitz G"'

1. Hydrolytic degradation of ROMP thermosetting materials catalysed by bio-derived acids and enzyme: from network to linear materials

Author

Hou, S., Hoyle, D. M., Khosravi, E., Blackwell, C. J., Haernvall, K., Perz, V., and Guebitz, G. M.

Subjects
Condensed Matter - Materials Science, Condensed Matter - Soft Condensed Matter
Abstract

This paper reports the first example of the 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 crosslink 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 that of the linear polymer analogues. These analyses confirmed the cleavage of the crosslink 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 of those observed for the linear polymer analogue. TGA showed that the cross-linked polymers thermally stable to 150 {\deg}C, beyond which showed weight losses due to the thermal cleavage of the acetal ester linkages., Comment: v2: updated article featuring 9 pages, 10 figures

Published
2016

29. Size controlled protein nanoemulsions for active targeting of folate receptor positive cells

Author

Loureiro, A., Nogueira, E., Azoia, N.G., Sárria, M.P., Abreu, A.S., Shimanovich, U., Rollett, A., Härmark, Johan, Hebert, Hans, Guebitz, G., Bernardes, G.J.L., Preto, A., Gomes, A.C., Cavaco-Paulo, A., Loureiro, A., Nogueira, E., Azoia, N.G., Sárria, M.P., Abreu, A.S., Shimanovich, U., Rollett, A., Härmark, Johan, Hebert, Hans, Guebitz, G., Bernardes, G.J.L., Preto, A., Gomes, A.C., and Cavaco-Paulo, A.

Abstract

Bovine serum albumin (BSA) nanoemulsions were produced by high pressure homogenization with a tri-block copolymer (Poloxamer 407), which presents a central hydrophobic chain of polyoxypropylene (PPO) and two identical lateral hydrophilic chains of polyethylene glycol (PEG). We observed a linear correlation between tri-block copolymer concentration and size - the use of 5. mg/mL of Poloxamer 407 yields nanoemulsions smaller than 100. nm. Molecular dynamics and fluorescent tagging of the tri-block copolymer highlight their mechanistic role on the size of emulsions. This novel method enables the fabrication of highly stable albumin emulsions in the nano-size range, highly desirable for controlled drug delivery. Folic Acid (FA)-tagged protein nanoemulsions were shown to promote specific folate receptor (FR)-mediated targeting in FR positive cells. The novel strategy presented here enables the construction of size controlled, functionalized protein-based nanoemulsions with excellent characteristics for active targeting in cancer therapy., QC 20151207

Published
2015
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33. Superhydrophobic functionalization of cutinase activated poly(lactic acid) surfaces.

Author

Gamerith, C., Orcal Yebra, A., Herrero Acero, E., Ortner, A., Guebitz, G. M., Pellis, A., Scaini, D., Kaluzna, I., Mink, D., and de Wildeman, S.

Subjects
SUPERHYDROPHOBIC surfaces, CUTINASE, MICROFLUIDICS
Abstract

Superhydrophobic materials have focused the interest of many researchers due to their potential in a wide spectrum of applications like microfluidics or biosensors in the biomedical field. Typically, the increased surface roughness at the micro or nano scale needed for superhydrophobic surfaces is achieved by coating of different substances, which in combination with a lower surface energy lead to Water Contact Angle (WCA) values greater than 150°. Here, limited enzymatic surface hydrolyis poly(lactic acid) (PLA) was combined with spin coating of a steraic alkene ketene dimer (AKD) layer. The selective enzymatic hydrolysis creates, in a gentle and controlled way, new hydroxylic and carboxylic groups on the polymer surface without damaging the material bulk properties like alkaline treatment does. The creation of new hydrophilic surface groups lead to a significant increase in the hydrophilicity, decreasing the WCA to less than 30° while raising the roughness from an Rrms of 50.5 to 90.8 nm concomittantly increasing the exposed surface vs. the projected one by 13.2%. Coupling of PLA hydroxy groups with AKD was demonstrated by using a PLA model substrate and subsequent identification of the reaction product via LC-TOF/MS. On the PLA film, FTIR based detection of the characteristic β-ketoester bond peak between the AKD and enzymatically generated hydroxy groups on the surface confirmed successful coupling. Scanning Electron Microscopy (SEM) & Atomic Force Microscopy (AFM) imaging confirmed the presence of fractal structures after curation of the enzymatically activated PLA film. The suitable size, 4.15 μm on the lateral dimension and 0.7 μm on height of the structures, together with the high density of these fractal structures lead to a superhydrophobic surface (WCA ＞150°). This process represents an alternative to produce chemically inert superhydrophobic bio-based polyesters surfaces, by combining mild biocatalytic activation of a polyester film with non-toxic chemicals in an environmentally friendly manner. [ABSTRACT FROM AUTHOR]

Published
2017
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47. Substrate specificity of Myriococcum thermophilum cellobiose dehydrogenase on mono-, oligo-, and polysaccharides related to in situ production of H2O2.

Author

Pricelius, S., Ludwig, R., Lant, N., Haltrich, D., and Guebitz, G.

Subjects
HYDROGEN peroxide, SUBSTRATES (Materials science), CORROSION prevention, POLYSACCHARIDES, MONOSACCHARIDES, OLIGOSACCHARIDES, DEHYDROGENASES, CARBOHYDRATES, OXIDATION, PEROXIDASE
Abstract

Cellobiose dehydrogenase from the ascomycete fungus Myriococcum thermophilum (MtCDH) was tested for the ability to generate bleaching species at a pH suitable for liquid detergents. The catalytic properties of MtCDH were investigated for a large variety of carbohydrate substrates using oxygen as an electron receptor. MtCDH produces H2O2 with all substrates tested (except fructose) but only in the presence of a chelant. Insoluble substrates like cellulose and cotton could as well be oxidized by MtCDH. To enhance the amount of cello-oligosaccharides in solution, different cellulases on cotton were used and in combination with MtCDH an increased H2O2 concentration could be measured. Additionally, the degradation of pure anthocyanins in solution (as model substrates for bleaching) was investigated in the absence and presence of a horseradish peroxidase. MtCDH was able to produce a sufficient amount of H2O2 to decolorize the anthocyanins within 2 h. [ABSTRACT FROM AUTHOR]

Published
2009
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49. Production of Cellulase-Free Polygalacturonase Preparation by Sclerotium rolfsii for Bioscrouring of Cotton.

Author

Schnitzhofer, W., Kandelbauer, A., Klug-Santner, B., Onos, M., Calafell, M., and Guebitz, G. M.

Subjects
COTTON, SCLEROTIUM rolfsii, PLANT disease research, POLYGALACTURONASE, CELLULASE, TEXTILE research, EDUCATION
Abstract

The article presents a study on the production of cellulase-free polygalacturonase preparation by Sclerotium rolfsii for bioscouring of cotton. The progress of bioscouring was analyzed by determination of residual pectin, weight loss, and water absorption time. No substantial differences among the tested preparations were observed for pectin removal and water absorption. However, substantially higher weight losses occurred for the preparations containing cellulase.

Published
2006
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50. Antibacterial Properties of an In Situ Generated and Simultaneously Deposited Nanocrystalline ZnO on Fabrics

Author

Perelshtein, I., Applerot, G., Perkas, N., Wehrschetz-Sigl, E., Hasmann, A., Guebitz, G. M., and Gedanken, A.

Abstract

Zinc oxide (ZnO) nanoparticles were synthesized and deposited on the surface of cotton fabrics using ultrasound irradiation. Optimization of the process resulted in a homogeneous distribution of ZnO nanocrystals, 30 nm in size, on the fabric surface. The mechanism of the ultrasound-assisted coating was proposed. The antibacterial activities of the ZnO-fabric composite were tested against Escherichia coli(Gram negative) and Staphylococcus aureus(Gram positive) cultures. A significant bactericidal effect, even in a 0.75% coated fabric (wt %), was demonstrated.

Published
2009
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