am5b01590_si_001.pdf (598.18 kB)
Strongly Stretched Protein Resistant Poly(ethylene glycol) Brushes Prepared by Grafting-To
journal contribution
posted on 2015-04-15, 00:00 authored by Gustav Emilsson, Rafael
L. Schoch, Laurent Feuz, Fredrik Höök, Roderick Y. H. Lim, Andreas B. DahlinWe
present a new grafting-to method for resistant “non-fouling”
poly(ethylene glycol) brushes, which is based on grafting of polymers
with reactive end groups in 0.9 M Na2SO4 at
room temperature. The grafting process, the resulting brushes, and
the resistance toward biomolecular adsorption are investigated by
surface plasmon resonance, quartz crystal microbalance, and atomic
force microscopy. We determine both grafting density and thickness
independently and use narrow molecular weight distributions which
result in well-defined brushes. High density (e.g., 0.4 coils per
nm2 for 10 kDa) and thick (40 nm for 20 kDa) brushes are
readily achieved that suppress adsorption from complete serum (10×
dilution, exposure for 50 min) by up to 99% on gold (down to 4 ng/cm2 protein coverage). The brushes outperform oligo(ethylene
glycol) monolayers prepared on the same surfaces and analyzed in the
same manner. The brush heights are in agreement with calculations
based on a simple model similar to the de Gennes “strongly
stretched” brush, where the height is proportional to molecular
weight. This result has so far generally been considered to be possible
only for brushes prepared by grafting-from. Our results are consistent
with the theory that the brushes act as kinetic barriers rather than
efficient prevention of adsorption at equilibrium. We suggest that
the free energy barrier for passing the brush depends on both monomer
concentration and thickness. The extraordinary simplicity of the method
and good inert properties of the brushes should make our results widely
applicable in biointerface science.