The mechanisms involve
d in the inhibition of protein a
dsorption by polyethylene oxi
de (PEO) are not completely un
derstoo
d, but it is believe
d that PEO chain length, chain
density an
d chain conformation all play a role. In this work, surfaces forme
d by chemisorption of PEO-thiol to gol
d were investigate
d: the effects of PEO chain
density, chain length (600, 750, 2000 an
d 5000 MW) an
d en
d-group (–OH, –OCH
3) on protein a
dsorption from plasma are reporte
d. Similar to previous single protein a
dsorption stu
dies (L.D.
Unsworth et al., Langmuir 2005;21:1036–41) it was foun
d that, of the
different surfaces investigate
d, PEO layers forme
d from solutions near the clou
d point a
dsorbe
d the lowest amount of fibrinogen from plasma. Layers of hy
droxyl-terminate
d PEO of MW 600 forme
d un
der these low solubility con
ditions showe
d almost complete suppression (versus controls) of the Vroman effect, with 20±1 ng/cm
2 a
dsorbe
d fibrinogen at the Vroman peak an
d 6.7±0.6 ng/cm
2 at higher plasma concentration. By comparison, Vroman peak a
dsorption was 70±20 an
d 50±3 ng/cm
2, respectively, for 750-OCH
3 an
d 2000-OCH
3 layers forme
d un
der low solubility con
ditions; a
dsorption on these surfaces at higher plasma concentration was 16±9 an
d 12±3 ng/cm
2. Thus in a
ddition to the effect of solution con
ditions note
d previously, the results of this stu
dy also suggest a chain en
d group effect which inhibits fibrinogen a
dsorption to, an
d/or facilitates
displacement from, hy
droxyl terminate
d PEO layers. Fibrinogen a
dsorption from plasma was not significantly
different for surfaces prepare
d with PEO of molecular weight 750 an
d 2000 when the chain
density was the same (
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der=0>0.5 chains/nm
2) supporting the conclusion that chain
density may be the key property for suppression of protein a
dsorption. The proteins elute
d from the surfaces after contact with plasma were investigate
d by SDS-PAGE an
d immunoblotting. A number of proteins were
detecte
d on the various surfaces inclu
ding fibrinogen, albumin, C3 an
d apolipoprotein A-I. The blot responses were zero or weak for all four proteins of the contact system; some complement activation was observe
d on all of the surfaces stu
die
d.