Phosphonylation, a chemical surface treatment, has been proposed as a means of increasing the hydrophilicity of LDPE, and therefore increase its lubricity and reduce vascular tissue damage. Phosphonyl groups O=P(OH)-O- are added by a gas phase coating process under reduced pressure. These groups can interact with phospholipids and proteins. To study the effect of protein adsorption, a set of samples was soaked in pig serum for 15 minutes. To study damage to the tissue as well as retention of the surface treatment on the polymer, samples were friction tested against the internal surface of pig aorta (Note: friction-tested samples were soaked first.) ESCA analysis of the various samples yielded the elemental composition given in the table below. What can you infer from the data about protein adsorption on LDPE after phosphonylation and friction testing? How might this affect the application as a catheter material?
|
LDPE Type
|
Atomic Concentration %
|
| |
C
|
P
|
N
|
|
Untreated
|
|
|
|
|
Untested
|
82.95
|
-
|
0.35
|
|
Soaked
|
67.91
|
-
|
13.29
|
|
Friction tested
|
69.10
|
-
|
7.19
|
|
Phosphonylated
|
|
|
|
|
Untested
|
73.94
|
2.38
|
1.93
|
|
Soaked
|
66.88
|
-
|
12.86
|
|
Friction tested
|
69.14
|
0.65
|
11.32
|