Immobilization of peroxidase on textile carrier materials and their application in the bleaching of colored whey.

Textiles represent promising support materials for enzymes. The goal of the present work was to investigate the immobilization of commercial peroxidase on a polyester needle felt and the repeated use in the gentle degradation of norbixin in whey from dairy cheese as a practical application. High enzyme loads were obtained by a 2-step immobilization procedure. First, the number of functional groups on the textile surface was increased by a modification with amino-functional polyvinylamine. Second, the enzyme was immobilized by using 2 types of crosslinking agents. Due to the iron content of peroxidase, inductively coupled plasma-optical emission spectrometry was used for the quantitative determination of the enzyme load on the textile. The enzyme activity was evaluated using common 2,2'-azino-di-(3-ethylbenzthiazoline-6-sulfonic acid) assay for peroxidases. By the variation of enzyme input and crosslinker concentration, a maximal enzyme load of 80 mg/g of textile was achieved, and a maximum specific activity of 57 U/g of textile. For the visualization of the enzyme on the fiber surface, fluorescence microscopy as well as scanning probe microscopy were used. The immobilized peroxidase showed significant activity, even after 50 reuse cycles. In addition, the potential of the new support and enzyme combination in commercial whey bleaching was demonstrated successfully on a 10-L scale.

Enzymatic epoxidation of cyclohexene by peroxidase immobilization on a textile and an adapted reactor design.

A textile-based reaction system for new peroxidase reactions in non-native media was implemented. The epoxidation of cyclohexene by the commercial peroxidase MaxiBright® was realized with the textile-immobilized enzyme in an adapted liquid-liquid two-phase reactor. A commercially available polyester felt was used as low-price carrier and functionalized with polyvinyl amine. The covalent immobilization with glutardialdehyde lead to an enzyme loading of 0.10 genzyme/gtextile. The textile-based peroxidase shows a high activity retention in the presence of organic media. This catalyst is shown to enable the epoxidation of cyclohexene in various solvents as well as under neat conditions. A model reactor was produced by 3D printing which places the textile catalyst at the interphase between the liquid reaction phase and the product extracting solvent.

[New nanofibrous scaffold for corneal tissue engineering]. / Eine neue Nanofaser-Matrix für den kornealen Gewebeersatz.

BACKGROUND: An estimated 10 million people suffer worldwide from vision loss caused by corneal damage. For the worst cases, the only available treatment is transplantation with human donor corneal tissue. However, in numerous countries there is a considerable shortage of corneal tissue of good quality, leading to various efforts to develop tissue substitutes. The present study aims to introduce a nanofibrous scaffold of poly(glycerol sebacate) PGS as a biodegradable implant, for the corneal tissue engineering. MATERIALS AND METHODS: Nanofibrous scaffolds were produced from PGS and poly(ε-caprolactone) (PCL) by a modified electro-spinning process. The biocompatibility of the material was tested in vitro by colorimetric MTT assay on days 3, 5, and 7 to test the cell viability of human corneal endothelium cells (HCEC). To examine a potential immunological reaction of the scaffolds, samples were exposed to mononuclear cells derived from peripheral blood (PBMCs). After an incubation period of 3 days, supernatants were assayed for apoptotic assessment and immunogenic potentials by annexin V FITC//propidium iodide and flow-cytometric analysis. RESULTS: We could successfully demonstrate that cultivation of HCECs on PGS/PCL scaffolds was possible. Compared to day 3, cell density determined by microplate absorbance was significantly higher after 7 days of cultivation (p < 0.0001). According to the MTT data, none of the samples showed toxicity. Apoptotic assessments by FACS analysis showed that no composition stimulated apoptosis or activated PBMCs occurred. All the compositions were inert for native as well as activated T/B/NK cells and monocytes. It can be concluded that leukocytes and their activity was not affected by the scaffolds. CONCLUSION: A tissue-like scaffold mimicking the human stroma could be developed. The results indicate that PGS/PCL scaffolds could be considered as ideal candidates for corneal tissue engineering as they are biocompatible in contact to corneal endothelial cells and blood cells.

Modification of the morphology of P(S-b-EO) templated thin TiO2 films by swelling with PS homopolymer.

For the controlled modification of sol-gel-templated polymer nanocomposites, which are transferred to a nanostructured, crystalline TiO2 phase by a calcination process, the addition of a single homopolymer was investigated. For the preparation, the homopolymer polystyrene (PS) is added in different amounts to the diblock copolymer P(S-b-EO) acting as a templating agent. The homopolymer/diblock copolymer blend system is combined with sol-gel chemistry to provide and attach the TiO2 nanoparticles to the diblock copolymer. So-called good-poor solvent-pair-induced phase separation leads to the formation of nanostructures by film preparation via spin coating. The fabricated morphologies are studied as a function of added homopolymer before and after calcination with atomic force microscopy, field emission scanning electron microscopy, and grazing incidence small-angle X-ray scattering. The observed behavior is discussed in the framework of controlling the block copolymer morphologies by the addition of homopolymers. At small homopolymer concentrations, the increase in homopolymer concentration changes the structure size, whereas at high homopolymer concentrations, a change in morphology is triggered. Thus, the behavior of a pure polymer system is transferred to a more complex hybrid system.

Nanowear on polymer films of different architecture.

In this paper, we describe atomic force microscope (AFM) friction experiments on different polymers. The aim was to analyze the influence of the physical architecture of the polymer on the degree and mode of wear and on the wear mode. Experiments were carried out with (1) linear polystyrene (PS) and cycloolefinic copolymers of ethylene and norbornene, which are stabilized by entanglements, (2) mechanically stretched PS, (3) polyisoprene-b-polystyrene diblock copolymers, with varying composition, (4) brush polymers consisting of a poly(methyl methacrylate) (PMMA) backbone and PS side chains, (5) PMMA and PS brushes grafted from a silicon wafer, (6) plasma-polymerized PS, and (7) chemically cross-linked polycarbonate. For linear polymers, wear depends critically on the orientation of the chains with respect to the scan direction. With increasing cross-link density, wear was reduced and ripple formation was suppressed. The cross-linking density was the dominating material parameter characterizing wear.