Biomedical Engineering Reference
In-Depth Information
(a)
(b)
20 µm
10 µm
(c)
(d)
20 µm
10 µm
(e)
(f )
20 µm
10 µm
FIGURE 2.18
SEM micrographs of adherent platelets on: (a and b) uncoated Si wafer, (c and d) undoped a-C film, (e and f)
a-C(Si37.6at.%) film. Number of adherent blood platelets decreases when Si concentration is increased. Platelet
activation type for a-C is mainly Type III-V, while for a-C(Si37.6at.%) is mainly Type I-III. Numerous platelet
aggregation sites are found on bare wafer, which marks the initial stage of thrombus formation.
carbon and fluorine atoms in a-C:H(F) films lowers the surface energy, which could result
in the reduced adsorption of proteins. Results from the protein adsorption study show
that a-C:H(F) film exhibited the highest albumin/fibrinogen ratio, which may be related to
the low number of adhering platelets and, therefore, a low tendency to induce thrombus
formation [72].
In the in vivo study, they assessed the systemic hematologic response and histocompat-
ibility of a-C:H(F) coated disks and uncoated SUS316L disks in a rat implant model. As
acute inflammatory markers, they evaluated the concentrations of TNF-alpha, IL-1beta,
and C3a in rat serum or plasma. In both the SUS and a-C:H(F) groups, they found no
detectable levels of these markers, which suggests that these materials do not induce an
acute systemic inflammatory response. Taken together, the results from these studies sug-
gest a favorable in vitro antithrombogenicity and an acceptable in vivo biocompatibility of
a-C:H(F) coated materials.
