Biomedical Engineering Reference
In-Depth Information
30
29
28
27
26
25
Si-DLC
CF
4
treated
Si-DLC
N
2
treated
Si-DLC
O
2
treated
Si-DLC
FIGURE 2.25
aPTTs of as deposited and O
2
-plasma treated a-C:H(Si) films. (Reprinted with permission from Roy et al.,
Acta
Biomater.
, 5, 249, 2009.)
a-C:H(Si) films were also found to have considerably reduced platelet adhesion compared
with untreated and CF
4
plasma-treated a-C:H(Si) films. The plasma treatment revealed an
intimate relationship between the polar component of the surface energy and its hemocom-
patibility. All
in vitro characterizations (e.g., protein absorption behavior, activated par-
tial thromboplastin time measurement, and platelet adhesion behavior) showed improved
hemocompatibility of the N
2
- or O
2
plasma-treated surfaces where the polar component
of the surface energy was significantly increased. Si-O or Si-N surface bonds played an
important role in improving hemocompatibility. These results support the importance of a
negatively charged polar component of the surface in inhibiting fibrinogen adsorption and
platelet adhesion.
Cytocompatibility
Cytocompatibility studies of a-C films have been performed in vitro by exposing the coated
materials to a variety of environments simulating the body ambience. In this section, the
various cells relating to various physiological environment and function will be discussed.
In vivo evaluation on a-C films will also be touched on.
Before we move on, we should at least have the basic concept of cell culturing, since
most of the studies carried out require cells to be cultured and then analyzed. Below is one
example, but do note the method is not limited to the one discussed here.
Cell culturing
. The study of cellular behavior on biomaterials surface in vitro is an impor-
tant aspect in determining the biocompatibility of the material. The healthy growth/pro-
liferation and morphology of the biological cells on the material surface is an important
prerequisite for compatibility.
Two types of cell lines were used in this study: African green monkey kidney fibroblast
COS7; and human osteosarcoma MG63. Both cell lines were obtained from the American
Type Culture Collection (ATCC, Rockwell, MD). Cells were cultured at 37°C in a humidi-
fied 5% CO
2
atmosphere. The standard medium used for culturing COS7 was Dulbecco's
