BIOMATERIALS AND MANUFACTURING METHODS FOR SCAFFOLD IN REGENERATIVE MEDICINE - Intelligent Scaffolds for Tissue Engineering and Regenerative Medicine - page 29

1.2.4.10 Polyhydroxyalkanoates
Polyhydroxyalkanoates are entirely natural and obtained from a
microorganism Alcaligen eutrophus , a gram-negative bacteria.
The physical properties of polyhydroxybutyrate (PHB) are similar
to those of nondegradable polypropylene. Its copolymers with
hydroxyvalerate—poly(hydroxybutylate- co -hydrovalerate) (PHBV)
—have a modest range of mechanical properties and a correspond-
ingly modest range of chemical compositions of each monomer and
processing condition. Also, these polymers can be manufactured
with many features, such as fibers, meshes, sponges, films, tubes,
and matrices, through standard processing techniques due to good
processability.
The family of polyhydroxyalkanoates shows no acute inflam-
mation, abscess formation, or tissue necrosis in the tissue adja-
cent in the form of nonporous discs or cylinders. 1 In order to
optimize the mechanical property of PHBV, an organic/inorganic
hybrid composite such as PHBV/hydroxyapatite was developed
for the tissue-engineered bone due to osteoconductive activity of
hydroxyapaitite. 10 Also, Schwann cell-seeded PHB was applied for
the regeneration of nerve in the shape of a conduit to guide and
induce neonerve tissue at the nerve ends. Good nerve regeneration
in PHB conduits in comparison with nerve grafts was observed. The
shapes, mechanical strength, porosity, thickness, and degradation
rate ofPHB and its copolymers can beengineered.
1.2.4.11 Other natural polymers
Naturalpolymersexceptthosediscussedinearliersectionsarepro-
teins, albumin, gluten, elastin, fibroin, cellulose, starch, sclerolucan,
elsinan, pectin (pectinic acid), galactan, curdlan, gellan, levan, emul-
san, dextran, pullulan, heparin, chondroitin 6-sulfate, etc. Although
they were not explained in this section, they are of interest due to
being the most abundant biopolymers on earth and due to their
unusual and useful functional properties. Typical properties are (i)
biocompatibilityandnontoxicity,(ii)easyprocessingasfilmandgel
status, (iii) heat stability and thermal processability over a
broad temperature range, and (iv) water solubility. 1 , 16 For the