Nanofibers and Nanosurfaces
113
by Yaylaci et al. [41]. Supramolecular GAG- nanofibers are hypothesized to emulate
natural hyaluronic acid, thereby inducing chondrogenesis. Without chondrogenic
media, the supramolecular GAG- nanofibers were able to display an approximate
increase of 2.5-fold of collagen II expressions, a 3-fold increase in aggrecan and
a 5-fold increase in Sox 9 expression in comparison to untreated control cells. In
another study, a composite nanofiber composed of peptide amphiphile (PA) and
hyaluronic acid (HA) was investigated for cartilage repair in the mouse model. The
results showed PA-HA nanofiber was able to encapsulate chondrocyte encapsulation
and displayed the lowest joint degradation score [42].
2.2 Nanofibers in Neuronal Tissue Engineering
For neuronal tissue engineering, autologous grafting of nerves from another site is
considered the gold standard. However, autologous nerve grafts are restricted by
limited availability, the possibility of permanent function loss at the harvest site, and
mismatch of the diameter of an injured nerve [27, 43]. Due to these limitations, autologous nerve grafting has been substituted with artificial nerve guide conduit (NGC).
Since nanofibers can manoeuvre the alignment of neural precursor cells, can guide
Schwann cell migration [10], and can augment regenerate impaired neurons, they
are considered as a promising alternative for autologous nerve grafting [8]. Electrospun NGC has shown the potential to direct axonal regeneration. A polycaprolactone
(PCL) /poly-L-lactic acid (PLLA), conduit successfully bridged a gap of 10 mm in a
rat sciatic nerve defect [27]. Similarly, a new U-shaped nerve guide conduit composed
of Co-polymers; poly (lactic- co -glycolic acid) (PLGA) and polyurethane (PU) was
fabricated for nerve regeneration using the electrospinning process. This inspiring
technique made the central part of the tube double-coated with randomly oriented
nanofibers over the aligned nanofibers, to strengthen the weak mechanical strength
of the aligned nanofibers. Apart from new technical developments, biodegradability
of polymers used for fabrication of nanofibers can increase the nerve restoration rate
[43]. Schuh et al. made a novel self-shaping conduit with electrospun fibrin-PLGA
nanofiber on fibrin gel, seeded with Schwann cell-like cells (SCLs) for peripheral
nerve regeneration. Although the study lacked in-vivo assessment, invitro analysis
showed that these aligned electrospun fibrin-PLGA fibres promoted the formation
of Büngner-like structures of SCLs [44]. On the other hand, in a different study, a
tubular conduit made of silk nanofiber and polyaniline nanoparticle was electrospun
for peripheral nerve regeneration in a sciatic nerve injury model. Since polyaniline is
a conducting polymer, it supports electrical conduction to repair lost nerve impulses.
The normal nerve conduction velocity in a normal rat is 58 m/sec. On seeding with
Schwann cells an excellent nerve conduction velocity of 50 ms-1 was achieved after
12 months of implantation, implying improved functional neuronal regeneration [45].
113
by Yaylaci et al. [41]. Supramolecular GAG- nanofibers are hypothesized to emulate
natural hyaluronic acid, thereby inducing chondrogenesis. Without chondrogenic
media, the supramolecular GAG- nanofibers were able to display an approximate
increase of 2.5-fold of collagen II expressions, a 3-fold increase in aggrecan and
a 5-fold increase in Sox 9 expression in comparison to untreated control cells. In
another study, a composite nanofiber composed of peptide amphiphile (PA) and
hyaluronic acid (HA) was investigated for cartilage repair in the mouse model. The
results showed PA-HA nanofiber was able to encapsulate chondrocyte encapsulation
and displayed the lowest joint degradation score [42].
2.2 Nanofibers in Neuronal Tissue Engineering
For neuronal tissue engineering, autologous grafting of nerves from another site is
considered the gold standard. However, autologous nerve grafts are restricted by
limited availability, the possibility of permanent function loss at the harvest site, and
mismatch of the diameter of an injured nerve [27, 43]. Due to these limitations, autologous nerve grafting has been substituted with artificial nerve guide conduit (NGC).
Since nanofibers can manoeuvre the alignment of neural precursor cells, can guide
Schwann cell migration [10], and can augment regenerate impaired neurons, they
are considered as a promising alternative for autologous nerve grafting [8]. Electrospun NGC has shown the potential to direct axonal regeneration. A polycaprolactone
(PCL) /poly-L-lactic acid (PLLA), conduit successfully bridged a gap of 10 mm in a
rat sciatic nerve defect [27]. Similarly, a new U-shaped nerve guide conduit composed
of Co-polymers; poly (lactic- co -glycolic acid) (PLGA) and polyurethane (PU) was
fabricated for nerve regeneration using the electrospinning process. This inspiring
technique made the central part of the tube double-coated with randomly oriented
nanofibers over the aligned nanofibers, to strengthen the weak mechanical strength
of the aligned nanofibers. Apart from new technical developments, biodegradability
of polymers used for fabrication of nanofibers can increase the nerve restoration rate
[43]. Schuh et al. made a novel self-shaping conduit with electrospun fibrin-PLGA
nanofiber on fibrin gel, seeded with Schwann cell-like cells (SCLs) for peripheral
nerve regeneration. Although the study lacked in-vivo assessment, invitro analysis
showed that these aligned electrospun fibrin-PLGA fibres promoted the formation
of Büngner-like structures of SCLs [44]. On the other hand, in a different study, a
tubular conduit made of silk nanofiber and polyaniline nanoparticle was electrospun
for peripheral nerve regeneration in a sciatic nerve injury model. Since polyaniline is
a conducting polymer, it supports electrical conduction to repair lost nerve impulses.
The normal nerve conduction velocity in a normal rat is 58 m/sec. On seeding with
Schwann cells an excellent nerve conduction velocity of 50 ms-1 was achieved after
12 months of implantation, implying improved functional neuronal regeneration [45].