Biomedical Engineering Reference
In-Depth Information
(see Ref. 142 and citations therein for more
details). The adsorption map is a kind of calibra-
tion curve relating protein adsorption to the sur-
face energy (water wettability) of the
adsorbent.
Plotting
leads to the immediate observation that there is
no measurable difference between FXII and
FXIIa in adsorption to solid surfaces. Furthermore,
it can be concluded from these data that neither
FXII nor FXIIa adsorb at surfaces exhibiting
τ O > 40 MJ/M 2 ∼ 55 O ) because the trend line
through the data passes through
τ τ O against τ O is a way of
accomplishing the correlations indicated by the
dashed arrows on the upper portion of Figure
8.7 that readily identify the surface energy
(water wettability) at which protein adsorption
does not occur. Figure 8.8 is an adsorption map
for purified FXII and FXIIa corresponding to
each purified protein at 300 μ g/mL, nearly 10X
the nominal physiological concentration of FXII
[149, 150] . Thermodynamic boundary conditions
enclose all observable data for a particular
protein or surfactant system in what is termed
an adsorption triangle (shaded portion of
Figure 8.8 ). According to the theory of adsorption
maps,
τ τ O
= 0
near this point.
Figure 8.9 a is an adsorption map correspond-
ing to 10% plasma from which it is also noted
that plasma proteins, taken as a whole, do not
τ − τ O
> 0 is characteristic of surfaces
that support adsorption, whereas surfaces that
do not support adsorption are characterized by
τ − τ O
≤ 0 MJ/M 2 . Inspection of Figure 8.8
FIGURE 8.8 An adsorption map for blood factor XII and
activated enzyme form FXIIa. All physically possible wetting
data falls inside the adsorption triangle (shaded). Data cor-
responding to FXII (triangles) cannot be distinguished from
FXIIa (circles). Open and closed symbols refer to adhesion
tensions calculated from advancing and receding contact
angles (see Section 8.4.4 for further discussion). Data falls
along a linear trend line passing through
FIGURE 8.9 An adsorption map for 10% EDTA antico-
agulated porcine plasma correlated with a quantitative
measure of the catalytic potential of a material to activate
porcine plasma coagulation. Panel A setup is the same as
Figure 8.8 and shows that blood plasma proteins do not
adsorb hydrophilic surfaces (see vertical arrow), in a manner
parallel to that discovered for human FXII and FXIIa. Com-
parison to Panel B shows that hydrophilic surfaces that do
not adsorb blood proteins are the most efficient activators of
plasma coagulation.
τ τ O
= 0 near
τ O = 40 MJ/M 2 (θ ∼ 55 ) , showing that neither protein
adsorbs to more hydrophilic surfaces (θ < 55 ) .
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