posted on 2012-10-09, 00:00authored byOgnen Pop-Georgievski, Dominique Verreault, Mark-Oliver Diesner, Vladimír Proks, Stefan Heissler, František Rypáček, Patrick Koelsch
Nonfouling surfaces capable of reducing protein adsorption
are
highly desirable in a wide range of applications. Coating of surfaces
with poly(ethylene oxide) (PEO), a water-soluble, nontoxic, and nonimmunogenic
polymer, is most frequently used to reduce nonspecific protein adsorption.
Here we show how to prepare dense PEO brushes on virtually any substrate
by tethering PEO to polydopamine (PDA)-modified surfaces. The chain
lengths of hetero-bifunctional PEOs were varied in the range of 45–500
oxyethylene units (Mn = 2000–20 000).
End-tethering of PEO chains was performed through amine and thiol
headgroups from reactive polymer melts to minimize excluded volume
effects. Surface plasmon resonance (SPR) was applied to investigate
the adsorption of model protein solutions and complex biologic medium
(human blood plasma) to the densely packed PEO brushes. The level
of protein adsorption of human serum albumin and fibrinogen solutions
was below the detection limit of the SPR measurements for all PEO
chains end-tethered to PDA, thus exceeding the protein resistance
of PEO layers tethered directly on gold. It was found that the surface
resistance to adsorption of lysozyme and human blood plasma increased
with increasing length and brush character of the PEO chains end-tethered
to PDA with a similar or better resistance in comparison to PEO layers
on gold. Furthermore, the chain density, thickness, swelling, and
conformation of PEO layers were determined using spectroscopic ellipsometry
(SE), dynamic water contact angle (DCA) measurements, infrared reflection–absorption
spectroscopy (IRRAS), and vibrational sum-frequency-generation (VSFG)
spectroscopy, the latter in air and water.