Biomedical Engineering Reference
In-Depth Information
pore sizeforthe simple reason of obtaininguseful and usabletissue
engineering scaffolds. The conventional norm of producing highly
porousstructureswithinterconnectingporesfortissueengineering
has to be followed. And the pore size must be su
ciently large for
cell migration.
45.5 Nanocomposite Scaffolds as Delivery Vehicles
for Biomolecules
Despitetheintroductionofbioactivematerialssuchasosteoconduc-
tiveCa-Pnanoparticlesintothepolymermatrix,compositescaffolds
alone may still not be su
cient to cause spontaneously bone heal-
ing and the regeneration of functional bone tissue, especially for
large bone defects, due to the lack of osteoinductivity.
60
In order to
further improve the bioactivity and functionality of scaffolds, bio-
molecules, especially growth factors, can be incorporated in bone
tissue engineering scaffolds. Delivery vehicles for biomolecules can
be made either by the attachment of biomolecules onto the sur-
face of scaffolds, through non-covalent binding (surface adsorption,
a
nity binding, ionic complexation) or covalent binding (chemical
conjugation), or by the physical entrapment of biomolecules inside
scaffolds during the scaffold fabrication process.
61
The release rate
and release kinetics of biomolecules from delivery vehicles are con-
trolledbycommonreleasemechanisms,includingdiffusion,erosion,
and swelling, subjected to the scaffold material, scaffold fabrica-
tiontechnique,scaffoldarchitecture,andbiomoleculeincorporation
method. In this chapter, our work on both entrapment and attach-
ment of biomolecules within/onto sintered Ca-P/PHBV nanocom-
posite scaffolds is presented as examples of the two approaches.
Fortheencapsulation ofbiomoleculeswithinsintered nanocom-
positescaffolds,thebiomoleculescouldbeincorporatedatthestage
of making Ca-P/PHBV nanocomposite microspheres using a solid-
in-water-in-oil-in-water(S/W/O/W)double-emulsionsolventevap-
oration method.
62
The double-emulsion method was chosen for the
purpose of minimizing biomolecule denaturation, which could be
causedbyorganicsolventsthatwereusedformakingpolymersolu-
tions. Bovine serum albumin (BSA), instead of growth factors, was
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