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Generation of Nanostructured Surfaces by Self-Assembly Strategies for Site-Selective Protein Adsorption

Sayın, Mustafa

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Abstract

ABSTRACT The aim of this study is to generate nanopatterned surfaces with feature sizes between 10 and 100 nm on large lateral scale in order to investigate confinement effects on the activity of adsorbed enzymes. To achieve this purpose, novel patterning techniques based on colloidal lithography were developed to generate five different types of nanopatterned surfaces: i) metal-semiconductor nanopatterns, ii) charge heterogeneous 2D and 3D nanopatterned polyelectrolyte multilayers (PEMs), iii) gold nanoparticle arrays on charge heterogeneous nanopatterned PEMs, iv) metal-dielectric hybrid nanopatterns, and v) nanopatterned oligo(ethylene)glycol silane self-assembled monolayers (SAMs). All of the fabricated nanopatterned surfaces were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), scanning electron microscopy (SEM), ellipsometry and UV-visible spectroscopy. Metal-semiconductor nanopatterns and charge heterogeneous 2D and 3D nanopatterned PEMs were chosen for protein adsorption investigations based on their excellent reproducibility and the capability to produce uniform and high density nanopatterns. Specifically, porous metal-semiconductor nanopatterns with 25 nm (type A25) and 60 nm (type A60) adsorption site diameter and honeycomb-like dielectric nanopatterns with 60 nm (type B60) and 100 nm (type B100) adsorption site diameter were fabricated to evaluate the specific enzymatic activity of surface-bound glucose oxidase (GOx). The amount of GOx adsorbed onto these nanopatterned surfaces was quantified by enzyme linked immunosorbent assays (ELISA). The specific activity of GOx on the nanopatterned surfaces was compared to the specific activity of GOx on poly(allyamine hydrochloride) coated non-patterned surfaces and in solution phase. It was found that the confinement of GOx into nano-domains of patterned substrates has a significant effect on protecting the enzymatic activity of GOx. When the adsorption site diameter was selected similar to enzyme size, the activity of the protein was well preserved and only a small loss of activity was observed. This is in line with the observation that proteins tend to unfold and lose their activity upon contact with surfaces which offer sufficient free surface area. We may therefore conclude from the study that geometrical confinement is a promising strategy to overcome this problem and stabilize surface-bound enzymes.

Item Type: Dissertation
Supervisor: Dahint, Prof. (apl). Dr. Reiner
Date of thesis defense: 21 November 2014
Date Deposited: 19 Dec 2014 12:34
Date: 2014
Faculties / Institutes: Fakultät für Chemie und Geowissenschaften > Institute of Physical Chemistry
Subjects: 540 Chemistry and allied sciences
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