Authors Pop-Georgievski, O. ; Zimmermann, R. ; Kotelnikov, I. ; Proks, V. ; Romeis, D. ; Kucka, J. ; Caspari, A. ; Rypácek, F. ; Werner, C.
Title Impact of bioactive peptide motifs on molecular structure, charging and non-fouling properties of poly(ethylene oxide) brushes
Date 04.05.2018
Number 54412
Abstract Polymer layers capable of suppressing protein adsorption from biological media while presenting extracellular matrix derived peptide motifs offer valuable new options for biomimetic surface engineering. Herein, we provide detailed insights into physico-chemical changes induced in a non-fouling poly(ethylene oxide) (PEO) brush/polydopamine (PDA) system by incorporation of adhesion ligand (RGD) peptides. Brushes with high surface chain densities (s = 0.5 chains·nm-2) and pronounced hydrophilicity (water contact angles = 10°) were prepared by end-tethering of hetero-bifunctional PEOs (Mn ~ 20000 g·mol-1) to PDA-modified surfaces from a reactive melt. Using alkyne distal end-group on the PEO chains, azidopentanoic-bearing peptides were coupled through a copper-catalyzed Huisgen azide-alkyne „click· cycloaddition reaction. The RGD surface concentration was tuned from complete saturation of the PEO surface with peptides (1.7×105 fmol·cm-2) to values which may induce distinct differences in cell adhesion (<6.0×102 fmol·cm-2). Infrared reflection-absorption and X-ray photoelectron spectroscopies proved the PDA-PEO layers’ covalent structure and the immobilization of RGD peptides. The complete reconstruction of experimental electrohydrodynamics data utilizing mean-field theory predictions further verified the attained brush structure of the end-tethered PEO chains which provided hydrodynamic screening of the PDA anchor. Increasing surface concentration of immobilized RGD peptides led to increased interfacial charging. Supported by simulations, this observation was attributed to as a result of the ionization of functional groups in the amino acid sequence and to the pH-dependent adsorption of water ions (OH- > H3O+) from the electrolyte. Despite the distinct differences observed in the electrokinetic analysis of the surfaces bearing different amounts of RGD, it was found that the peptide presence on PEO(20000)-PDA layers does not have a significant effect on the non-fouling properties of the system. Notably, the presented PEO(20000)-PDA layers bearing RGD peptides in the surface concentration range 5.9–1.7×105 reduced the protein adsorption from fetal bovine serum to less than 30 ng·cm-2, i.e. values comparable to the ones obtained for pristine PEO(20000)-PDA layers.
Publisher Langmuir
Citation Langmuir 34 (2018) 6010-6020

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