Biomedical Engineering Reference
In-Depth Information
8.9 (continued)
of polymer/ceramic composites to nucleate and deposit hydroxyapatite on
the material surface in vitro, uncoated and ceramic-coated samples were
soaked in simulated body fluid (SBF) for different periods of time. This
process is known in the literature as a 'biomimetic process' associated with
bone (Kokubo, 1996). The samples were characterized after immersion in
SBF for one to two weeks. Field emission scanning electron microscopy
(FESEM) examination of all tested samples indicated changes in the
appearance and morphology (microstructure) of the materials after
incubation in SBF. Figure 8.10 shows the FESEM images of the Al
2
O
3
-
coated porous polymer samples after incubation in SBF at 37
8
C. Compared
to Fig. 8.10(a), after one week, the surface of the polymer substrate was
roughened and several small, individual hydroxyapatite particles (Fig. 8.10
(b)) were formed. After two weeks (Fig. 8.10(c)), the amount of
hydroxyapatite present on the substrate surface was greatly increased.
Moreover, nanoscale hydroxyapatite particles were homogeneously dis-
persed and formed a fairly dense coating on the substrate surface. The
substrate surface appeared considerably rougher in comparison to the
surface before hydroxyapatite formation. In order to verify the composition
of the hydroxyapatite, EDS was performed to analyze the composition of
the particular matter formed on the substrate surface. The EDS spectrum
(Fig. 8.10(d)) confirmed that a considerable amount of calcium (Ca) and
phosphor (P) was present on the roughened surface, and in relative amounts
that are typical of hydroxyapatite compositions.
The impetus behind this study was to demonstrate a convenient and
universal surface treatment strategy for modifying the surface properties of
porous polymer materials and thus a method to promote cell adhesion for
tissue engineering. Surface modification of porous polymers with ultra-thin
