BIOMATERIALS AND MANUFACTURING METHODS FOR SCAFFOLD IN REGENERATIVE MEDICINE - Intelligent Scaffolds for Tissue Engineering and Regenerative Medicine - page 20

1.2.3.8 Biodegradable polyurethane
Polyurethane is one of the most widely used polymeric bioma-
terials in biomedical fields due to unique physical properties
such as durability, elasticity, elastomer-like character, fatigue resis-
tance, compliance, and tolerance. Moreover, the plentiful reac-
tivity on the functional group of a polyurethane backbone can
achieve the attachment of biologically active biomolecules and the
adjustment of hydrophilicity/hydrophobicity. 23 Typical biodegrad-
able polyurethane is composed of an amino acid-based hard seg-
ment, such as lysine diisocyanate, and a polyol soft segment, such
as hydroxyl donor-like polyester and sugar. Hence, the degradation
products of this nontoxic lysine diisocyanate-based urethane poly-
mer are nontoxic lysine and the polyol. By the covalent bonding of
various proteins, such as cytokines, growth factors, and peptides,
introduced in the polymer backbone, the controlled release of the
bioactive molecules can be achieved by the degradable manner of
polyurethane scaffolds.
Mechanisms of degradation are hydrolysis, oxidation, and ther-
malandenzymaticmanner.Boththechemistryandthecomposition
of soft and hard segments play an important role in the degradabil-
ity of polyurethane. Poly(urethane-urea) matrices with lysine diiso-
cyanate as the hard segment and glucose, glycerol, or PEG as soft
segments. Toxicity, induction of foreign-body reactions, and anti-
body formation were not observed in the in vivo experiment. The
elucidation of long-term safety and biocompatibility for biodegrad-
able polyurethane must be continuously conducted for the success-
ful application of tissue engineeringscaffold substrates.
1.2.3.9 Other synthetic polymers
Many synthetic polymers, either degradable or nondegradable, are
newly launched and tested to mimic the natural tissue and wound-
healing environment. Examples are poly(2-hydroxyethylmetha-
cryrate) hydrogel, injectable poly( N -isopropylacryamide) hydrogel,
and polyethylene for neocartilage, poly(iminocarbonates) and
tyrosine-based poly(iminocarbonates) for bone and cornea,
cross-linked collagen/PVA films and an injectable biphasic calcium