Biomedical Engineering Reference
In-Depth Information
In addition to natural polymers such as silk and HA, a large number of syn-
thetic polymers - based electrospun nano/micro - fi bers have been studied for bone
tissue engineering applications. One such polymer, polycaprolactone, has been
explored in bone tissue engineering primarily due to its low costs, slow degrada-
tion and non-toxic nature. Yashimoto et al. studied the potential of PCL nanofi -
bers in bone tissue engineering when seeded with human MSCs and cultured in
rotary bioreactors [227]. Their results demonstrated hardening of cell-matrix con-
structs after a few days, thereby supporting mineralized tissue formation and
demonstrating the potential of PCL nanofi bers in bone regeneration.
In another study, Venugopal et al. synthesized electrospun biocomposite scaf-
folds composed of PCL, hydroxyapatite nanoparticles, and collagen in the ratio of
60 : 90 : 30 [228] . The rationale for the composition was that PCL provided mechan-
ical strength; collagen (component of the natural ECM) supported cell prolifera-
tion; and HA promoted osteogenesis and bone mineralization. The results
demonstrated an interconnecting porous structure (porosity-80%) with fi ber
diameter ranging from 189
272 nm that provided suffi cient
mechanical strength of 1.73 MPa and good osteoblast morphology along with an
increase in proliferation (up to 35%) and mineralization (up to 55%) as com-
pared to the controls. Therefore, this study demonstrated the potential of PCL,
collagen and HA in bone-tissue engineering. In a more recent study, Catledge
et al. synthesized a triphasic scaffold composed of a similar mixture (PCL :
collagen : HA in a ratio of 50 : 30 : 20) with mean fi ber diameter of 180
±
0.026 nm to 579
±
50 nm
closely resembling the collagen fi ber in the ECM of bone [229]. The collagen
counterpart played an important role in improving the stiffness of the scaffold as
indicated by the elastic modulus (highest for collagen/HA: 3.9 GPa) and demon-
strated the potential of the composite scaffold in bone-tissue regeneration.
Recent advances in technology have led scientists to develop a strategy of
guided bone regeneration (GBR). In this approach, a membrane—when placed
on a defected bone site—“guides” the growth of the new bone and at the same
time prevents the in-growth of fi brous scar tissue into the grafted site. GBR has
been mainly explored in periodontal surgery with success of both non-degradable
implant and biodegradable membranes. Fujihara et al. reported the phenomenon
of GBR on nanofi brous surfaces due to the enhanced cell response as compared
to microfi brous surfaces [230]. Initial experiments by their group focused on the
synthesis of GBR membranes composed of PCL nanofi bers with calcium carbon-
ate nanoparticles that promoted osteoconduction and served as bone-fi lling
material. The GBR membrane, however, lacked the requisite tensile strength. In
later studies, they provided a supporting PCL nanofi brous layer to the mechani-
cally stable composite of electrospun PCL nanofi bers and demonstrated its
mechanical stability by stretching it to around 200% strain without physical dis-
ruption. Further, the authors demonstrated osteoblast proliferation on the PCL/
CaCO3 composite nanofi bers on GBR membranes thereby their potential in
bone tissue engineering. Approximately at the same time, another type of
composite electrospun PCL mats impregnated with calcium carbonate or HA
particles were synthesized by Wutticharoenmongkol et al. [231]. They demon-
±
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