Biomedical Engineering Reference
In-Depth Information
80
70
60
50
40
30
20
10
0
Adhered platelets
Unactivated platelets
80
70
60
50
40
30
20
10
0
0
7.4
16.6
24.9
32.3
37.6
Si atomic concentration (at.%)
FIGURE 2.14
Number of adherent platelets and percentage of inactivated platelets with increasing Si concentration. Values
are mean of six replicates, while error bars denote standard error. ANOVA was conducted, and effect of Si con-
centration on number of adherent platelet was significant,
F
(5,30)
= 23.05,
p
=1.89 × 10
−9
.
such a-C films, whether hydrogenated or not. In this case, there is an increase in the sur-
face energy when Si concentration is increased further, and it is attributed to the increase
in the polar component (as shown in Figure 2.16).
The amount of adhered platelets and activation on the film surfaces is inversely pro-
portional to the ratio of albumin to fibrinogen adhesion on the surfaces [45,46]. This is
because the adhesion of albumin (a water-soluble protein in the blood plasma) on the film
can prevent the adhesion of platelets. Fibrinogen is a protein that can enhance the adhe-
sion and activation of platelets, and hence a thrombus when it is converted into fibrin by
the action of the enzyme thrombin. The surface tensions of both albumin and fibrino-
gen are found to be similar at 65 mN/m [67], and the polar component of fibrinogen is
higher than that of albumin: 40.3 mN/m as compared to 33.6 mN/m. The Lifshitz-van der
Waals/acid-base approach allows a more in-depth analysis of the polar component. The
polar component can further be differentiated into base (electron donor) and acid (electron
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
230
225
220
215
210
205
200
195
190
0
5
10
15
20
25
30
35
40
Si atomic concentration (at.%)
FIGURE 2.15
Raman D to G peaks intensity ratios with increasing Si concentration. (Reprinted with permission from Ong
et al.,
Biomaterials
, 28, 4033, 2007.)
