Biomedical Engineering Reference
In-Depth Information
BSA-vs-Fg Binary Binding Competition
For the purpose of haemo-compatibility, manipulations of protein adsorption
aim to maximally resist Fg binding by means of albumin preoccupation. In
contrast to the outcomes from the trials with a single protein—no matter BSA
or Fg, the setup of BSA-vs-Fg binary binding competition obviously provides
a better model to mimic and thus investigate the real reactions occurring at
the interface between serum and artificial materials. The experiment is per-
formed with two parallel systems—mixtures of BSA
∗
/Fg and BSA/Fg
∗
with
the same concentration fractions that are comparable to the ratio in serum.
The results of the competition are presented in Fig. 6a. As compared with the
data yielded from untreated PEU materials, the surface decoration by MPEO-
derived SMAs simultaneously enhances BSA adsorption and reduces Fg bind-
ing in a dramatic manner; in contrast, if solely immobilizing PEG spacers
without the presence of functional endgroups (the ligands), as MPEO-OH
does, both BSA and Fg bindings are significantly resisted. This result again re-
veals the SMAs' function of BSA binding efficacy while highlighting the BSA
binding specificity against Fg under a competitive condition [80, 81].
BSA Reversible Adsorption
The efficacy of protein adsorption comprises not only the quantity of phys-
ical binding but also the maintenance of protein bioactivity. As stated in
Sect. 1.5.2, one of the major rationales for granting SMAs with spacer arms is
just to maximally avoid denaturing the adsorbed proteins. From the physic-
ochemical angle, a very straightforward means to examine bioactivity of the
adsorbed BSA is to test the binding reversibility. Active protein binding is
believed to be a dynamic equilibrium between the counteractions of adsorp-
tion and desorption, namely, active protein adsorption should be reversible
and the adsorbed bioactive proteins should be renewable. The assessment
is conducted by exposing sample surfaces to radioiodine-labeled BSA
∗
so-
Fig. 6
Competitive binding of bovine serum albumin [BSA] vs. bovine serum fibrinogen
[Fg] (
A
), and reversibility of BSA adsorption (
B
), on PEU surfaces modified by MPEO-
derived SMAs, as determined by radioiodine labeling [80, 81]. Reproduced from [177, 178]
