Biomedical Engineering Reference
In-Depth Information
Sonication
(95% vol. acetone/water mix)
3x 5 min
Distilled water
rinse
Distilled water
rinse
Distilled water
rinse
Distilled water
rinse
3x 5 min
H
2
SO
4
soaking
(pH 4)
NaOH soaking
(0.1 M)
SBF
(pH 7.4)
1 min
3 min
3 hr
Distilled water
rinse
Distilled water
rinse
Distilled water
rinse
3x 5 min
3x 5 min
3x 5 min
FIGURE 9.23
Cleaning methods investigated [71].
with complex ionic exchange resulting in few free -OH groups. The cleaned glasses were
then functionalized using 3-amino-propyl-triethoxysilane (APTS). Not surprisingly, acid-,
base-, and SBF-washed glasses exhibited poor functionalization with APTS. Washing the
glasses with acetone/water mixture resulted in high numbers of free hydroxyl groups cou-
pled with poor condensation, resulting in higher APTS functionalization. Finally, human
BMP-2 protein was grafted onto all the functionalized substrates and protein immobili-
zation tracked via determining N/Si ratios using XPS spectra. As expected, N/Si ratios
indicated successful grafting of BMP-2 on all silanized surfaces.
Summary
Bioactive glasses offer new concepts for both loading-bearing implant applications and
regenerative medicine devices. For all generations of biomaterials, bioactive glasses show
the highest levels of bioactivity.
First-generation bone replacement biomaterials were bioinert and were selected because
they mechanically matched host tissues. These materials were designed as a means to an
end to replace host tissue and interact, to a minimum, with the hosts' immune system. The
discovery that certain compositions of glasses could elicit in vivo biological responses with
bone and soft tissues (bioactivity) revolutionized biomaterials research. Second-generation
materials are bioactive or resorbable. Silica has been shown to be the active component for
bioactivity via the formation of a silica-gel layer on/in which HA precipitation occurs
and subsequent tissue bonding. Precipitation of HA is believed to be crucial for bio-
activity. Varying silica content directly correlates to the materials bonding ability to hard
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