Biomedical Engineering Reference
In-Depth Information
Mimicking the structure of biological materials is another interesting
direction for developing composites with biomimetic properties, e.g., elec-
trospun composite nanofibers. Due to their similarity to the extracellular
matrix and ease of incorporation of drugs (e.g., chemotherapeutic drugs,
114
antibiotics
115,116
), growth factors, natural materials,
117
and inorganic
nanofillers,
118
electrospun composite nanofibers have been proposed for
drug delivery
117,119,120
and tissue engineering applications.
121-124
Shape
memory electrospun composite nanofibers have emerged as a class of active
biomaterials that are capable of changing shape in a predefined way under
controlled external stimulus such as heat and alternating magnetic field.
This class of electrospun composite nanofibers has potential as multi-
functional tissue engineering scaffolds.
125
To convey the multi-functional character of biologic modulators, surface
modification of synthetic composites with RGD (integrins binding domains)
has been attempted. Growth factors, morphogenetic proteins, specific oli-
gopeptide cleaving sequences specific for matrix metalloproteinases
(MMPs), anti-thrombin sequences and plasmin degradation sites have also
been attempted.
126
For example, adhesion ligands
127
and recombinant
osteopontin (rOPN17-169)
65
have been observed to improve the adhesion of
anchorage-dependent cells, e.g., osteoblasts to a hydrophobic surface. Both
adhesion ligands and rOPN17-169 have the capacity to bind to various
integrins; rOPN17-169 bind to a
v
b
3
,
128
a
v
b
1
,
129
a
v
b
5
,
129
or a
a
b
1
130
integrins.
65
Coating a composite or implantable device with a smart coat is an alter-
native way of developing functionalized composites. Drug-releasing
engineered surface coatings are of paramount importance for various bio-
medical applications from implantable devices to tissue engineering. For
example, lipogel-coated-liposome-functionalized poly(vinyl alcohol) com-
posite hydrogels have been made cell adhesive by coating the lipogel with
poly(dopamine).
131
While enhancing the in vivo functionality of the
implantable device, it can also be important to reduce the foreign body re-
action. Coating glucose biosensors with poly(lactic-co-glycolic) acid (PLGA)
microspheres dispersed in poly(vinyl alcohol) (PVA) hydrogels controlled
both inflammation and fibrous tissue formation while allowing for rapid
glucose diffusion to the sensor.
67,93
d
n
3
r
4
n
g
|
1
.
7.4 Interfaces of Clinical Importance
This next section focuses on interfaces having clinical importance and the
recent advances in composites used to restore them. These interfaces in-
clude osteochondral, neuromuscular-prosthesis and tooth-restoration.
7.4.1 The Osteochondral Interface
Understanding the structural and morphological changes occurring at the
osteochondral interface is of prime importance in treating many diseases
affecting this transitional zone. The osteochondral junction encompasses
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