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search.filters.applied.f.access: openAccess × Author: König, Ulla × Author: Müller, Martin × DDC: 540 × Type: Text × WGL Institute: IPF ×

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    In Situ Monitoring of Linear RGD-Peptide Bioconjugation with Nanoscale Polymer Brushes
    (Washington, DC : ACS Publications, 2017) Psarra, Evmorfia; König, Ulla; Müller, Martin; Bittrich, Eva; Eichhorn, Klaus-Jochen; Welzel, Petra B.; Stamm, Manfred; Uhlmann, Petra
    Bioinspired materials mimicking the native extracellular matrix environment are promising for biotechnological applications. Particularly, modular biosurface engineering based on the functionalization of stimuli-responsive polymer brushes with peptide sequences can be used for the development of smart surfaces with biomimetic cues. The key aspect of this study is the in situ monitoring and analytical verification of the biofunctionalization process on the basis of three complementary analytical techniques. In situ spectroscopic ellipsometry was used to quantify the amount of chemisorbed GRGDS at both the homopolymer poly(acrylic acid) (PAA) brush and the binary poly(N-isopropylacrylamide) (PNIPAAm)-PAA brushes, which was finally confirmed by an acidic hydrolysis combined with a subsequent reverse-phase high-performance liquid chromatography analysis. In situ attenuated total reflection-Fourier transform infrared spectroscopy provided a step-by-step detection of the biofunctionalization process so that an optimized protocol for the bioconjugation of GRGDS could be identified. The optimized protocol was used to create a temperature-responsive binary brush with a high amount of chemisorbed GRGDS, which is a promising candidate for the temperature-sensitive control of GRGDS presentation in further cell-instructive studies.
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    In-situ-investigation of enzyme immobilization on polymer brushes
    (Lausanne : Frontiers Media, 2019) Koenig, Meike; König, Ulla; Eichhorn, Klaus-Jochen; Müller, Martin; Stamm, Manfred; Uhlmann, Petra
    Herein, we report on the use of a combined setup of quartz-crystal microbalance, with dissipation monitoring and spectroscopic ellipsometry, to comprehensively investigate the covalent immobilization of an enzyme to a polymer layer. All steps of the covalent reaction of the model enzyme glucose oxidase with the poly(acrylic acid) brush by carbodiimide chemistry, were monitored in-situ. Data were analyzed using optical and viscoelastic modeling. A nearly complete collapse of the polymer chains was found upon activation of the carboxylic acid groups with N-(3-Dimethylaminopropyl)-N'-ethylcarbodiimide and N-Hydroxysuccinimide. The reaction with the amine groups of the enzyme occurs simultaneously with re-hydration of the polymer layer. Significantly more enzyme was immobilized on the surface compared to physical adsorption at similar conditions, at the same pH. It was found that the pH responsive swelling behavior was almost not affected by the presence of the enzyme. © 2019 Koenig, König, Eichhorn, Müller, Stamm and Uhlmann.