Chemistry Reference
In-Depth Information
with relatively higher functionality. Grafting oligomers allows more con-
trolled processes and a high yield (83%).
156
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7.4.4 Surface Modification
PHAs' excellent mechanical properties, biocompatibility and degradability
have made them useful in the field of tissue engineering. These polymers
could prove very useful as tissue scaffolds for implantation purposes.
157
However, the smooth surface of a solvent-cast PHA scaffold is a major obs-
tacle for cell attachment in tissue regeneration processes.
158
This warrants
the enzymatic catalyzed surface erosion of PHA. Moreover, the PHA surface
lacks a bioactive ligand to couple with a bioactive molecule in targeting
devices or biosensors. Hence, PHA surface erosion or roughening is needed
to provide a corrugated trough to immobilize bioactive molecules such as
insulin,
159
fibronectin
160
and collagen
161
while enhancing its cell attach-
ment or cell proliferation characteristics and thus expanding its biomedical
applications.
162
Ihssen et al.
163
used extracellular PHA depolymerase from
Pseudomonas fluorescens as the capture ligand to immobilize a fusion protein
on to mcl-PHA microbeads of 200-300 nm size (Figure 7.14). This arrange-
ment could be employed as a probe for targeting proteins in drug delivery,
protein microarrays, and protein purification. Furthermore, the researchers
reported that the binding capacity was comparable to similar-sized poly-
styrene particles commonly used for antibody immobilization in clinical
diagnostics.
163
Recently, the use of nanoparticles as drug delivery systems for targeted
release at specific parts of the body represents a promising solution for
cancer treatment.
164
Surface functionalization of PHA nanoparticles is nee-
ded to improve targeting eciency in delivering drug molecules to target
cells. This modification can be done via PHA-protein block copolymer-
ization. Generally, during in vivo synthesis of PHA, PHA synthase is a key
enzyme that catalyzes the polymerization of hydroxyacyl-Coenzyme A, a
.
Figure 7.14
Immobilization of targeted protein onto PHA using extracellular PHA
depolymerase, reprinted from Ihssen et al.
163
with permission from the
American Chemical Society.
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