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Low-Fouling Characteristics of Ultrathin Zwitterionic Cysteine SAMs
journal contribution
posted on 2018-07-30, 00:00 authored by Peter Lin, Tsung-Liang Chuang, Paul Z. Chen, Chii-Wann Lin, Frank X. GuSurface fouling remains an exigent
issue for many biological implants.
Unwanted solutes adsorb to reduce device efficiency and hasten degradation
while increasing the risks of microbial colonization and adverse inflammatory
response. To address unwanted fouling in modern implants in vivo,
surface modification with antifouling polymers has become indispensable.
Recently, zwitterionic self-assembled monolayers, which contain two
or more charged functional groups but are electrostatically neutral
and form highly hydrated surfaces, have been the focus of many antifouling
coatings. Reports using various compositions of zwitterionic polymer
brushes have demonstrated ultralow fouling in the ng/cm2 range. These coatings, however, are thick and can hinder the target
application of biological devices. Here, we report an ultrathin (8.52
Å) antifouling self-assembled monolayer composed of cysteine
that is amenable to facile fabrication. The antifouling characteristics
of the zwitterionic surfaces were evaluated against bovine serum albumin,
fibrinogen, and human blood in real time using quartz crystal microbalance
and surface plasmon resonance imaging. Compared to untreated gold
surfaces, the ultrathin cysteine coating reduced the adsorption of
bovine serum albumin by 95% (43 ng/cm2 adsorbed) after
3 h and 90% reduction after 24 h. Similarly, the cysteine self-assembled
monolayer reduced the adsorption of fibrinogen as well as human blood
by >90%. The surfaces were further characterized using scanning
electron
microscopy: protein-enhanced adsorption and cellular adsorption in
human blood was found on untreated surfaces but not on the cysteine
SAM-protected surfaces. These findings suggest that surfaces can be
functionalized with an ultrathin layer of cysteine to resist the adsorption
of key proteins, with performance comparable to zwitterionic polymer
brushes. As such, cysteine surface coatings are a promising methodology
to improve the long-term utility of biological devices.
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Keywords
adsorptioncysteine self-assembled monolayerantifoulingzwitterionic polymer brushesUnwanted solutes adsorbzwitterionic self-assembled monolayerssurface plasmon resonance imagingcysteine SAM-protected surfacesquartz crystal microbalancescanning electron microscopycysteine surface coatingsultrathin cysteine coatingUltrathin Zwitterionic Cysteine SAMs Surface foulingserum albumin
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