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Significance Statement
Due to the requirements for biomedical applications, controlling of surface topography and chemical functionality on the nanometer scale is crucial for the development and the design of tailor-made smart bio-interfaces. Thus contributing to a faster conversion, nano-technological knowledge can assist bio-scientific approaches. In this regard, our research is focused on nano-engineering of well-defined, tunable and nano-scaled polymer brush systems, sensitive to different physical or chemical stimuli.
The advantages of polymer brushes are manifold, e.g. defined adjustment of physico-chemical surface properties by grafting density, molecular weight and composition; response of the polymer chains to environmental changes followed by switching of surface properties; enormous variety of well adjustable polymer brush compositions (homo, binary, ternary). In this way, the polymer brush properties open many possible applications, especially for the ability to adapt and regulate interactions with cells and biomolecules such as switchable adsorption or bio-functionalization. Respectively, the results in the featured article demonstrate the sensitivity and selectivity of polymer brush systems as a cited example. As one can observe, small changes of the brush composition sufficiently effect as well as potentially enhance the impact on protein adsorption and cell behavior onto the brush surface. In particular, cells are attracted to response to the flexible polymer brush layer in a characteristic manner. Each brush composition whether homo or binary polymer brush shows specific cell interactions.
In addition, the easy-to use and adaptive brush preparation process -the grafting-to process- is a simple technology attractive for industrial manufacturing. Polymer brushes used as functional nano-scaled coatings have a significant relevance for bioscience applications in the fields of tissue engineering, diagnostics, regenerative medicine and biomaterial research.
Figure Legend:
Chart of bioengineered polymer brushes: schematic representation of the brush composition interacting with exemplary biomolecules; derived principal properties and potential applications.
Journal Reference
ACS Appl Mater Interfaces. 2015;7(23):12516-29.
Psarra E1,2, König U1, Ueda Y3, Bellmann C1, Janke A1, Bittrich E1, Eichhorn KJ1, Uhlmann P1.
[expand title=”Show Affiliations”]- Leibniz Institute of Polymer Research Dresden, Hohe Strasse 6, 01069 Dresden, Germany.
- Faculty of Science, Department of Chemistry, Chair of Physical Chemistry of Polymeric Materials, The Technische Universität Dresden, Bergstrasse 66, 01069 Dresden, Germany.
- Department of Biocompatibility, Institute of Biomaterial Science HZG Teltow, Kantstrasse 55, 14513 Teltow, Germany.
Abstract
Controlling the reversibility, quantity, and extent of biomolecule interaction at interfaces has a significant relevance for biomedical and biotechnological applications, because protein adsorption is always the first step when a solid surface gets in contact with a biological fluid. Polymerbrushes, composed of end-tethered linear polymers with sufficient grafting density, are very promising to control and alter interactions with biological systems because of their unique structure and distinct collaborative response to environmental changes. We studied protein adsorption and cell adhesion at polymer brush substrates which consisted of poly(N-isopropylacrylamide) (PNIPAAm), having a lower critical solution temperature (LCST), to control bioadsorptive processes by changing the environmental temperature. Preparing the PNIPAAm brushes by the “grafting-to”-method two differently synthesized PNIPAAm polymers were used, at which one possessed an additional hydrophobic terminal headgroup. It is known that hydrophobic moieties can influence protein adsorption significantly. The films were comprehensively analyzed by in situ spectroscopic ellipsometry, contact angle measurements, streaming potential, and atomic force microscopy. Our study was mainly focused on the investigation of the fibrinogen (FGN) adsorption responsiveness both on homo polymer PNIPAAm brushes with and without the hydrophobic terminal functionalization, and further on binary brushes made of the polyelectrolyte poly(acrylic acid) (PAA) and one of the prior described two PNIPAAm species. The results show that the terminal hydrophobic modification of PNIPAAm has a considerable impact on wettability, LCST, and morphology of the homo and the binary brush systems, which consequently led to an alteration of FGN adsorption. By using binary PNIPAAm-PAA brushes with different composition it was possible to induce stimuli dependent FGN adsorption with a considerable amplified switching effect by introducing a hydrophobic terminal residue to PNIPAAm. Cell adhesion studies with human mesenchymal stem cells reflected the results of the FGN adsorption.
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