Biomedical Engineering Reference
In-Depth Information
SLS, 55.63
±
2.89% of BSA encapsulated in the microspheres could
maintain itsbioactivity withoutdenaturation.
For studying the
in vitro
release behavior of BSA, BSA-loaded
microspheres and scaffolds were placed in centrifuge tubes, with
each tube being filled with 5 mL of phosphate buffer saline (PBS,
pH7.4)containing0.05wt%ofsodiumazide.Thetubeswereplaced
in a shaking water bath, which was maintained at 37
◦
C and shaken
horizontally at 30 rpm, for up to 28 days. At preset times, 2 mL
of the supernatant was withdrawn from each tube after centrifu-
gation to determine the amount of BSA released by using a Micro
BCAassaykitand2mLfreshmediumwasreplenishedforeachtube.
Figure 45.10 shows
in vitro
release profiles of BSA from Ca-P/PHBV
microspheres and scaffolds in relation to the total amount of encap-
sulated BSA and in relation to the carrier, respectively. As could be
seen,aninitialburstreleaseoccurred,followedbyalow-raterelease
behavior for all test samples. After 28 days, approximately 85%
cumulativereleaseofBSAfromCa-P/PHBVnanocompositescaffolds
was achieved.
Differing from the traditional approach, which uses dry-blended
polymeric particles with drug powders for SLS-formed scaffolds, in
thisinvestigation,thebiomoleculeswereencapsulatedinsidePHBV-
based microspheres and the microspheres were expected to protect
biomolecules from high heat caused by SLS during scaffold fabri-
cation and to control the release behavior of biomolecules
in vitro
and
in vivo
. However, although BSA could be successfully encapsu-
lated within Ca-P/PHBV nanocomposite scaffolds and released
in
vitro
in a relatively controlled manner, the EE in both BSA-loaded
microspheres and scaffolds was relatively low. Therefore, other
strategies need to be considered and investigated for achieving SLS-
formed, multifunctional bonetissue engineeringscaffolds.
Immobilizing biomolecules on the carrier surface and releas-
ing them in a controlled manner has been appealing to many
researchersandcanbeaneffectivewayforthecontrolleddeliveryof
growthfactorsfromSLS-formedscaffolds.ForCa-P/PHBVnanocom-
posite scaffolds, this strategy requires surface modification of the
scaffolds forintroducing bindingsitesfor growth factors.
The surface modification of sintered rod-shaped Ca-P/PHBV
scaffolds was conducted in two steps: (1) physical entrapment of
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