Biomedical Engineering Reference
In-Depth Information
6 nm [57, 58]. The POSS modification of the PCU polymer enhances several characteristics
of the polymer, including its mechanical, thermodynamic stability, and cytocompatibility
[59]. The POSS is derived from a class of compounds closely related to silicones and
has the chemical composition of a hybrid, intermediate between that of silica and silicone.
The chemical diversity of POSS technology is broad and POSS molecules are cytocompat-
ible and suitable for synthesis of nanocomposite materials [54, 60].
They possess high tensile and elastomeric properties, good biocompatibility, and are easily
fabricated and modified. The contrasting segmental characteristics of the soft amorphous
phase and hard crystalline phase of polyurethanes provide the foundation for its versatility
[61]. The hard segment provides this material with advantageous mechanical properties and
the soft segment allows for elastomeric properties. The side chains of this copolymer may be
modified to enhance particular properties for biomedical applications [62-64].
Numerous studies have shown that POSS-PCU scaffolds are antithrombogenic, biocom-
patible [58], nontoxic [54, 60], and do not cause inflammatory reactions to the surrounding
host tissue [55]. Several cell lineages have been shown to attach to and grow on POSS-PCU,
including fibroblasts, adipose stem cells, epithelial cells, endothelial cells, and chondrocytes,
illustrating the cytocompatiblity and nontoxic properties of the biomaterial [55, 60, 65, 66].
Furthermore POSS-PCU scaffolds implanted in a sheep model illustrated no signs of
degradation and inflammation over 36 months [55].
The POSS-PCU scaffold has already been taken to clinic use to replace tissues and organs,
being implemented as the world's first synthetic trachea in 2011 (Figure 21.2) in a 36-year-old
O
(A)
NH
O
(C)
O
i-Bu
O
Si
O
O
O
Si
NH
NH
NH
Urea hard segment
i-Bu
O
O
Si
Si
NH
i-Bu
O
O
O
i-Bu
O
HN
Si
Urethane group
Si
O
O
O
i-Bu
O
O
Si
Si
O
O
O
i-Bu
i-Bu
POSS Nanocage
O
NH
O
NH
O
O
O
O
n
O
ata
O
O
O
(B)
i-Bu
O
O
O
O
O
Si
O
O
O
Si
i-Bu
O
Si
Si
(D)
(E)
i-Bu
O
O
i-Bu
O
Si
Si
O
O
i-Bu
O
Si
Si
O
i-Bu
i-Bu
POSS Nanocage
Figure 21.2
Translational applications of POSS-PCU nanocomposite polymer already used for
humans. (A) Schematic drawing of the poly-oligomeric silsesquioxane (POSS) nanocage. (B) The chemical
structure of POSS-PCU with the polycarbonate back bone with the POSS particle. (C) The POSS-
PCU manufactured for a lower limb bypass graft. (D) The POSS-PCU lacrimal duct that has been
successfully used in a patient. (E) The world's first synthetic trachea, which was implanted to replace the
trachea of a man with carcinoma of the trachea. Reproduced from [58] with permission by the Journal
of Tissue Engineering and Regenerative Medicine.
(See insert for color representation of the figure.)
