Biomedical Engineering Reference
In-Depth Information
TABLE 19.6
Interfacial Energies between Materials and Plasma Proteins
Ca-DLC
CaP-DLC
P-DLC
LTIC
Biological
Substances
γ
s
p
/
γ
s
d
γ
s
p
/
γ
s
d
γ
sp
γ
s
p
/
γ
s
d
γ
s
p
/
γ
s
d
γ
sp
γ
sp
γ
sp
Fibrinogen
6.7
0.04
45.4
4.62
6.5
0.02
16.8
12.2
Albumin
11.2
0.11
35.8
6.31
10.7
0.08
11.8
46.6
Source
:
Kwok, S.C.H. et al.,
Diam. Relat. Mater.,
15, 893, 2006. With permission.
TABLE 19.7
Contact Angle (
θ
w
) and Interfacial Energy (
γ
sw
) between Different
Materials (Samples) and Water
γ
sw
(nJ/cm
2
)
Materials
θ
w
(
°
)
Ca-DLC
87.2
6.2
CaP-DLC
51
57.6
P-DLC
49
5.1
LTIC
74.9
24.2
Source
:
Kwok, S.C.H. et al.,
Diam. Relat. Mater.
, 15, 893, 2006. With permission.
The interfacial energies (
γ
sp
) between plasma proteins and samples are shown in Table 19.6.
Ca-DLC (0.11) and P-DLC (0.08) have lower values of
γ
sp
p
/
γ
sp
d
for albumin (
γ
sp
p
and
γ
sp
d
represent
the polar and dispersive components of the interfacial energy between proteins and materials) than
CaP-DLC and LTIC, suggesting stronger adhesion of albumin. The
γ
sp
p
/
γ
sp
d
ratio for fi brinogen is
also small, but the total interfacial energy,
γ
sp
, is less than that of albumin, which means that less
conformational changes occur. The results suggest that these surface energies are the primary
factors for the good compatibility observed on Ca-DLC and P-DLC in the platelet adhesion test.
Table 19.7 shows the results of the contact angles and calculated interfacial energies (
γ
sw
) between
water and the fi lms. Ca-DLC and P-DLC have the lowest values of interfacial energy (
γ
sw
=
6.2
and 5.1, respectively) with water (medium), indicating that both fi lms have closer interfacial ten-
sion (1-3 nJ/cm
2
) with the cell medium than CaP-DLC and LTIC. Hence, the platelet results are
consistent with the calculated surface energy.
19.5.2 T
I
-O T
HIN
F
ILM
Titanium oxide is widely used in optical and electrical applications because of its high refractive
index and dielectric constant. It is also very attractive as a biocompatible protective coating on
medical implants, where a protective surface layer of TiO
2
increases the wear resistance and hard-
ness considerably. Dissolution of Ti metal ions from the rutile phase is one order of magnitude lower
than that from anatase, and so rutile is the preferred phase with respect to biomedical applications
