BIOMATERIALS AND MANUFACTURING METHODS FOR SCAFFOLD IN REGENERATIVE MEDICINE - Intelligent Scaffolds for Tissue Engineering and Regenerative Medicine - page 19

1.2.3.6 Oxalate-based polyesters (polyoxalate)
Polyoxalate is one of absorbable polyesters that have oxalate link-
agesintheirbackbone.Theoxalate-basedpolymerswerefirstintro-
duced by Shalaby and coworkers in the 1970s for suture-coating
purposes. 21 Polyoxalate was reported to undergo ester hydroly-
sis to give oxalic acid and diol as by-products. The hydropho-
bicity was between PLA and PGA, and the hydrolytic stability
decreased primarily with an increase in methylene fraction in
the repeating unit. Copolyoxalate was also synthesized to increase
the melting temperature by using cyclic and aromatic diols. The
chemical composition influenced hydrolytic stability and tissue
reaction. The poly(1,4-cyclohexylenedicarbinyl- co -hexamethylene
oxalate) exhibited an increasing fast in vivo weight loss as the
1,4-cyclohexylenedicarbinyl content decreased and slight and mild
tissue reactions during the first five days of implantation.
Poy(oxalate- co -oxamide) exhibited higher hydrophilicity and a
faster degradation profile compared with copolyoxalate. When for-
mulated into films, poy(oxalate- co -oxamide) showed higher cell
attachment andproliferation than PLGA. 22
1.2.3.7 Polyphosphazene
Polyphosphazene consists of an inorganic backbone of alternating
single and double bonds between phosphorous and nitrogen atoms,
while most of the polymer comprises the carbon-carbon organic
backbone. 20 It has side groups that can react with another func-
tional group resulting in block or star polymers. Biological and
physical properties can be controlled by the substitution of func-
tional side groups. The wettability as hydrophilicity, hydrophobic-
ity, and amphiphilicity of polyphosphazene might depend on the
properties of side groups. It can be fabricated into films, mem-
branes, and hydrogels for scaffolds applications by cross-linking or
graftingmodifications.Cytocompatibilityofhighlyporouspolyphos-
phazene scaffolds was observed with the possibility of skeletal
tissue engineering. Also, the blend of polyphosphazene with PLGA
has been investigated to modify and determine miscibility and
degradability.