Biomedical Engineering Reference
In-Depth Information
Mineralization was confirmed by ARS staining of
nodule formation shown in
Fig. 10.7
; the staining
confirmed the findings from SEM that mineralization
was occurring at an earlier time point on the treated
and titanium surfaces. The level of mineralization on
the 1800 s modified PEEK was significantly higher
throughout compared to unmodified PEEK and the
level of mineralization was found to be more abun-
dant on all the modified PEEK and titanium surfaces
from day 14 onward.
Our research has evaluated surface modification of
PEEK by oxygen plasma treatment to improve
cell
e
material interactions
[45]
. The plasma modifi-
cation has been shown to change both the chemistry
and the micro- and nanotopography of PEEK
surfaces, leading to an increase in surface energy. The
chemical change to the surface led to an increase in
surface oxygen, where polar functional groups were
primarily formed, such as carbonyl and carboxyl. By
washing immediately after the plasma modification,
we have shown the surfaces to be stabilized and that
the increase in surface energy and the polar functional
groups is present even 26 months after plasma treat-
ment. This change in the surface chemistry and
topography was shown to influence HOB adhesion,
spreading and proliferating from day 1 postplating
onward, where significantly higher cell densities were
observed throughout the 28-day experiments on all
the modified PEEK surfaces compared to unmodified
PEEK. Scanning electronmicrographs also confirmed
this, showing the osteoblast cells to have a limited
attachment to the unmodified PEEK. In addition,
higher levels of mineralization were found on the
modified PEEK surfaces compared to the unmodified
surfaces. These findings indicate that this method of
oxygen plasma surface modification is likely to
improve bony integration to PEEK implants, and we
are currently evaluating the in vivo response to these
modified surfaces.
techniques are suitable for a particular application.
Over the past 30 years, there has been a substantial
amount of research into widening the application of
PEEK by changing the various material properties
such as mechanical reinforcement by the incorpora-
tion of carbon fibers
[14,28,111]
, altering the surface
by coating with materials such as calcium phosphates
[33,43,112
e
114]
and titanium
[40,44]
, or by func-
tionalization
[39,41,65,115]
. However, to date, direct
bone contact to orthopedic PEEK implants, such as
spinal fusion cages, has been reported to be limited
[20,23,24,65]
. There is therefore a great need to
identify surface modification techniques that can be
successfully applied to PEEK implants.
References
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10.5 Perspectives
The aim of this chapter has been to give an over-
view of the current state of the art for surface modi-
fication of PEEK materials. As PEEK becomes more
widespread as an implant material, the need to modify
the surface will increase, and there are a number of
techniques currently being investigated. Of utmost
importance is choosing the right modification tech-
nique for an application, as not all modification
cells, Biomaterials
20
(1999)
547
e
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[8] B. Wesslen, M. Kober, C. Freij-Larsson,
A. Ljungh, M. Paulsson, Protein adsorption of
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